Keywords: Incompatible insect technique
Spatial Dynamics and Sterilization Range of Incompatible Aedes albopictus Males: Advancing Toward an Optimized IIT Approach
35474Lampazzi, E., Virgillito, C., Caputo, B., et al., Tropical Medicine and Infectious Disease, 11. 2026-02-06 18:17:05.
The Incompatible Insect Technique (IIT) is a species-specific, eco-friendly mosquito control method that relies on releasing Wolbachia-infected males, which induce cytoplasmic incompatibility (CI), rendering eggs inviable when mating with wild females. Aiming at optimizing IIT protocols in terms of cost-effectiveness, data on incompatible male dispersal and survival and the distance- and time-related impact of induced sterility are fundamental. This study plans to fill this gap and reports findings from a two-year field trial (2022–2023) at the ENEA-Casaccia Research Center, based on single-spot releases of incompatible Aedes albopictus males (ARwP strain). Male releases were carried out in late September 2022 (~15,000 released males) and the early Ae. albopictus season (at the end of June 2023; ~24,000 released males). Fifty-eight ovitraps were located at a 20–900 m distance from the ARwP release spot and were monitored weekly from May to November to assess egg hatching rates and measure CI effects in relation to both distance and time. Following the 2023 release, samples of adults were collected at increasing distances from the release site and at multiple post-release time points to assess, individually, wild female fertility and ARwP male dispersal and survival using Wolbachia as a genetic marker. Statistical analyses revealed that: (a) the highest reduction in the egg hatching was found within 100 m from the release spot (46.5% and 19.9%, respectively, in 2022 and 2023) but remained significant even at greater distances (29.9% and 7.7% at 300 m, respectively, in 2022 and 2023); (b) accordingly, the highest reduction in the wild female fertility occurred within 100 m from the release spot (47.3%), but similar effects were recognizable up to 600 m; (c) the overflooding ratio of the ARwP males did not significantly differ between 3 and 11 days after the release, with ARwP males remaining active up to 18 days and dispersing as far as 400 m. These results demonstrate the potential of localized, non-inundative IIT trials to furnish clues for the setup of spatially optimized release strategies, especially in scaled-up applications. The study also emphasizes the need for standardized assessment tools and further research regarding environmental and behavioral factors influencing long-term suppression outcomes.
Thousands of mosquitoes are being dropped by drone over islands in Hawaii. Here’s why
34999Nell Lewis, CNN, 2025-07-31 15:47:51.
In June, dozens of biodegradable pods fell from the sky over the forests of Hawaii. Each one, delivered by drone, contained about 1,000 mosquitoes. These weren’t just any mosquitoes — they were non-biting, lab-reared male mosquitoes carrying a common bacterium that results in eggs that don’t hatch when the males mate with wild females. The hope is that they will help to control the archipelago’s invasive mosquito population, which is decimating native bird populations, such as rare Hawaiian honeycreepers. The birds, which are key pollinators and seed dispersers and also play a central role in Hawaiian culture, are in dire straits. There were once more than 50 known species of honeycreepers in Hawaii, but today there are only 17 left, most of which are endangered. Last year, the ‘akikiki, a small gray bird, went functionally extinct in the wild, and less than 100 of the yellow-green ʻakekeʻe are estimated to remain. Development and deforestation have had an impact, but according to Dr. Chris Farmer, Hawaii program director for the American Bird Conservancy (ABC), the “existential threat” is avian malaria, which is spread by mosquitoes.
Drones To Deliver Millions Of Mosquitoes to Prevent Bird Extinctions In Hawai‘i
34913GrrlScientist, Forbes, 2025-06-11 19:19:54.
In a brilliant demonstration of multidisciplinary collaboration, a conservation program to save Hawai’i’s critically endangered native bird species has taken another step forward. After a team of scientists created “reproductively incompatible” male mosquitoes in the lab, the next challenge was to safely deliver them to where they would most effectively suppress mosquito populations in Hawai’i. “Reproductively incompatible” male mosquitoes are created by infecting their mothers with the bacteria, Wolbachia. This bacteria, which naturally occurs in many wild insect species, interferes with reproduction in mosquitoes by making the Wolbachia-males reproductively incompatible with normal wild-type female mosquitoes. (But the males can successfully reproduce with females infected with the same strain of Wolbachia – that is how the millions of mosquitoes needed for this project are produced in the lab.) When these reproductively incompatible Wolbachia-male mosquitoes mate with normal wild female mosquitoes, the resulting eggs cannot hatch, thereby reducing the mosquito population. The good news in this story (which will become important as you read on) is that male mosquitoes (regardless of whether they carry Wolbachia) do not bite or transmit disease, and feed only on plant juices and nectar for survival and energy. On the other hand, female mosquitoes do bite because they need a fresh blood meal to produce eggs. Additionally, because mosquitoes infected with Wolbachia bacteria are not genetically modified, and because Wolbachia bacteria naturally occur in 60% or more wild insects, these mosquitoes are safe.
Adjacent spillover efficacy of Wolbachia for control of dengue: emulation of a cluster randomised target trial
34679Lim, J.T., Mailepessov, D., Chong, C.S. et al., BMC Medicine, 23. 2025-03-28 08:29:31.
Matings between male Aedes aegypti mosquitoes infected with wAlbB strain of Wolbachia and wild-type females yield non-viable eggs, thereby suppressing Ae. aegypti abundance in the field. We evaluated the spillover efficacy of releasing wAlbB-infected Ae. aegypti male mosquitoes to suppress dengue in sites adjacent to release sites (spillover sites). The protocol of a two-arm cluster-randomised test-negative controlled trial (cRCT) was specified and emulated using a nationally representative dengue test-negative/positive database of 454,437 individuals reporting for febrile illness to primary or secondary care in public healthcare institutions. Spillover intervention sites were defined by geolocating locations which were adjacent to, i.e. shared geographical borders with, actual Wolbachia intervention sites. We built a cohort of individuals who resided in spillover sites versus a comparator control group who resided in sites which did not receive Wolbachia interventions. We emulated a constrained randomisation protocol used in cRCTs to balance dengue risk between spillover and control arms in the pre-intervention period. We matched individuals reporting for testing in intervention and control groups by calendar time and a high-dimensional battery of sociodemographic, environmental and anthropogenic variables. Intention-to-treat analysis was conducted to estimate the protective efficacy against dengue given spillover Wolbachia exposure. The final cohort consisted of 2354 matched individuals residing in Wolbachia spillover and control sites for at least 3 months in the study period. Compared to the controls, individuals residing in spillover sites for 3 or more months were associated with a 45% (OR: 0.55, 95% CI: 0.42‒0.74) reduction in risk of contracting dengue. Higher durations of spillover Wolbachia exposure also modestly increased protective efficacies. Compared to the control arm, the proportion of virologically confirmed dengue cases was lower in the spillover arm overall and across each subgroup. Protective efficacies were found across all years, age and sex subgroups. Our results demonstrated the potential of Wolbachia-mediated sterility for reducing the risk of contracting dengue even in sites which were not directly treated by the intervention.
Mark-Release-Recapture of Packed and Shipped Aedes aegypti with Wolbachia: Implications for Conducting Remote Incompatible Insect Technique Programs
34640Ohm, J. R., Lynd, A., McGowan, A., et al., The American Journal of Tropical Medicine and Hygiene, 2025-03-21 14:44:30.
Male mosquitoes containing the endosymbiont Wolbachia (Wb+) can be used as a tool to suppress wild mosquito populations through a technique termed incompatible insect technique (IIT). IIT programs reduce wild mosquitoes via incompatible matings between released males and wild females to reduce the number of viable offspring produced in the next generation. Successful programs rely on regular release of incompatible males to outcompete wild males for female mates. Past IIT programs have relied on local production of Wb+ males to support regular releases of incompatible males. Here, we evaluated the survival and dispersal of packed and shipped Wb+ Aedes aegypti males in mark-release-recapture studies at a release site in the British Virgin Islands (BVI), separated by over 3,600 miles from the centralized production facility. Released mosquitoes were recaptured using BG-Sentinel 2 traps collected daily for up to 7 days after release. Wb+ male mosquitoes packed and shipped from a centralized production facility performed similarly to males that were locally reared in the BVI in survival, dispersal, and recapture rates. Our results support the conclusion that packing and shipping live Wb+ male mosquitoes does not impact their ability to survive and disperse in release sites and suggests that IIT mosquito control programs can feasibly be conducted nearly anywhere in the world without the need for local mosquito production facilities.
Recommendations for Implementing Innovative Technologies to Control Aedes aegypti: Population Suppression Using a Combination of the Incompatible and Sterile Insect Techniques (IIT-SIT), Based on the Mexican Experience/Initiative
34247Martín-Park, A., Contreras-Perera, Y., et al., Insects, 15:987. 2025-01-13 11:41:22.
The future of Aedes aegypti control emphasizes the transition from traditional insecticides toward more sustainable and multisectoral integrated strategies, like using Wolbachia-carrying mosquitoes for population suppression or replacement. We reviewed the integration of the successful Mexican initiative, “Mosquitos Buenos”, with the key challenges outlined in the PAHO guidelines for incorporating innovative approaches into vector control programs. These challenges include establishing essential infrastructure, training personnel, managing field operations, and fostering community support. Our experience provides critical evidence to support the strategic National Plan for implementing and integrating IIT-SIT technologies to control Ae. aegypti and dengue. Furthermore, this experience serves as a foundation for other countries in the region interested in adopting these technologies. It underscores the importance of strategic planning, multisectoral collaboration, continuous evaluation, and scaling up innovative tools to ensure their long-term effectiveness and sustainability in urban areas where Aedes vectors and the diseases they transmit are endemic.
Effectiveness of Wolbachia-mediated sterility coupled with sterile insect technique to suppress adult Aedes aegypti populations in Singapore: a synthetic control study
31580Bansal, Somya, et al., The Lancet Planetary Health, 8:617-628. 2024-09-17 10:04:54.
In this synthetic control study, we conducted a large-scale, field trial of IIT-SIT targeting Aedes aegypti among high-rise public housing estates in Singapore, an equatorial city state. Routinely collected data from a large, nationwide surveillance system of 57 990 unique mosquito traps, combined with a high-dimensional set of anthropogenic and environmental confounders were collected to ascertain mosquito abundance and its key drivers. Four townships were selected as the intervention groups (approximate population size of 607 872 residents as of 2022), wherein interventions that combined ITT with SIT over the course of the study period were conducted. Townships were subject to releases of wAlbB-SG male A aegypti mosquitoes twice a week. Data were assessed over the course of epidemiological weeks (EWs), which provide the finest temporal resolution of recorded Wolbachia release schedule and mosquito abundance data. A novel synthetic control framework was then developed to account for the non-randomised and staggered adoption setting of the intervention across trial sectors to identify the direct suppressive effectiveness of IIT-SIT on female A aegypti populations, the spillover effects in non-release areas, and the effect of the intervention on other mosquito populations such as Aedes albopictus. Furthermore, we recalculated effectiveness in terms of calendar time, time since intervention, and over multiple sites to examine heterogeneities in IIT-SIT effectiveness. Between EW27 2018 and EW26 2022, Wolbachia releases were conducted across 117 sectors, of which 97 had sufficient trap data, which were collected between EW8 2019 and EW26 2022. We found that Wolbachia-based IIT-SIT reduced wild-type female A aegypti populations by a mean of 62·01% (95% CI 60·68 to 63·26) by 3 months, 78·40% (77·56 to 79·18) by 6 months, and 91·32% (90·95 to 91·66) by at least 18 months of releases. We also found a smaller but non-negligible spillover suppression effect that gradually increased over time (mean spillover intervention effectiveness 61·02% [95% CI 57·89 to 63·72] in adjacent, non-intervention sectors). Although no consistent change in A albopictus populations was seen across the four intervention townships after Wolbachia releases, the average intervention effectiveness on the A albopictus population across all release sectors was –25·80% (95% CI –30·93 to –21·05), which was driven by increases in two towns.
Incompatible insect technique: insights on potential outcomes of releasing contaminant females: a proof of concept under semi-field conditions
30947Giulia Lombardi, Elena Lampazzi, Maurizio Calvitti, Pest Management Science, 2024-07-25 18:45:37.
Releasing large numbers of Aedes albopictus males, carrying the artificially introduced Wolbachia ‘wPip’ strain, results in a decrease in the reproductive capacity of wild females due to a phenomenon known as cytoplasmic incompatibility (CI). This vector control strategy is referred to as the incompatible insect technique (IIT). However, its widespread implementation faces various challenges, including the complexity of removing fertile females from the males intended for release. Here, we present the results of semi-field experiments comparing the impact of minimal female co-release on two IIT modes: unidirectional CI-based (UnCI IIT) and bidirectional CI-based (BiCI IIT), specifically targeting Ae. albopictus. The contamination of ‘wPip’ infected females (2%) during male releases significantly weakened the overall effectiveness of IIT, emphasizing the need for thorough sex separation. Specifically, with UnCI IIT, despite the low rate of co-released females, there was a gradual rise in ‘wPip’ infection frequency, resulting in more compatible mating and subsequently higher rates of egg hatching. Conversely, this pattern was effectively mitigated in BiCI IIT owing to the reciprocal sterility between the wild-type and the ‘wPip’ infected populations. Through an experimental approach, conducted in a semi-field setting, we have contributed to advancing scientific understanding regarding the potential outcomes of implementing the IIT strategy in the absence of a complete sexing system. The results suggest that safety measures for mitigating the potential impacts of co-released females can be tailored according to the specific type of IIT being utilized. © 2024 Society of Chemical Industry.
Taking the fight against disease to mosquitoes
28948Gregory Devine, Setopati, 2024-02-27 18:33:30.
In the medium term it's likely that suppression strategies involving self-limiting genetic modifications, Wolbachia infection and irradiation will be extended to a small number of our most important mosquito vectors of disease.
Efficacy of Wolbachia-mediated sterility to reduce the incidence of dengue: a synthetic control study in Singapore
28940Jue Tao Lim, Somya Bansal*, Chee Seng Chong*, Borame Dickens, Youming Ng, Lu Deng, Caleb Lee, Li Yun Tan, Grace Chain, Pei Ma, Shuzhen Sim, Cheong Huat Tan, Alex R Cook, Lee Ching Ng, The Lancet Microbe, 2024-02-27 18:18:52.
Our study comprised an at-risk population of 607 872 individuals living in intervention sites and 3 894 544 individuals living in control sites. Interventions demonstrated up to 77·28% (121/156, 95% CI 75·81–78·58) intervention efficacy despite incomplete coverage across all towns until EW 26, 2022. Intervention efficacies increased as release coverage increased across all intervention sites. Releases led to 2242 (95% CI 2092–2391) fewer cases per 100 000 people in intervention sites during the study period. Secondary analysis showed that these intervention effects were replicated across all age groups and both sexes for intervention sites.
Maui ‘ground zero’ for release of billions of biopesticide lab-altered mosquitoes
28929Michael Nevradakis, LifeSite, 2024-02-27 16:57:41.
Up to 775,992,000 bacteria-infected mosquitoes could be released in Maui every week for the next 20 years, according to Hawaii Unites, an environmental advocacy group that last month lost its bid to require the state to conduct an environmental impact statement before allowing the controversial project to proceed. Hawaii Unites in May 2023 sued the state in the Circuit Court of the First Circuit in Hawaii. The group’s president and founder, Tina Lia, told The Defender: "These biopesticide lab-altered mosquitoes are already being released in East Maui. Hawaii Unites has taken the state to court seeking a ruling to require an environmental impact statement for the project and comprehensive studies of the risks". She said Hawaii Unites describes itself as “a 501(c)(3) non-profit organization dedicated to the conservation and protection of our environment and natural resources,” with a focus on “protecting the health of Hawai‘i’s people, wildlife, and the ‘āina from the State of Hawaii’s biopesticide bacteria-infected mosquito experiment.”
Judge sides with Hawaii to block challenge to mosquito release plan
28925Candice Cheung, Courthouse News Service, 2024-02-27 16:29:17.
A planned program to save endemic Hawaiian birds from avian malaria by releasing thousands of biopesticide mosquitoes into Maui’s rainforest will go on, despite an attempt by an environmental nonprofit to block the project.First Circuit Court Judge John Tonaki ruled Tuesday in favor of the state of Hawaii, its Department of Land and Natural Resources and conservationists to block a lawsuit claiming the state agency did not complete a proper environmental evaluation of program aimed at curbing mosquito population to prevent them from spreading avian malaria.“This is a victory for our endangered forest birds who some native Hawaiians consider their ancestors,” Dawn Chang, chair of the state’s Board of Land and Natural Resources said in a statement. “The HEPA is an important tool that enables decisionmakers to assess environmental impacts — not the sword by which misinformation kills a project, aimed at saving native species.”
Different mechanisms of X-ray irradiation-induced male and female sterility in Aedes aegypti
28570Zhang, H., Trueman, E., Hou, X. et al., BMC Biology, 21. 2023-11-29 14:14:21.
Aedes aegypti (Ae. aegypti) is the major vector that transmits many diseases including dengue, Zika, and filariasis in tropical and subtropical regions. Due to the growing resistance to chemical-based insecticides, biological control methods have become an emerging direction to control mosquito populations. The sterile insect technique (SIT) deploys high doses of ionizing radiation to sterilize male mosquitoes before the release. The Wolbachia-based population suppression method of the incompatible insect technique (IIT) involves the release of Wolbachia-infected males to sterilize uninfected field females. Due to the lack of perfect sex separation tools, a low percentage of female contamination is detected in the male population. To prevent the unintentional release of these Wolbachia-infected females which might result in population replacement, a low dose of X-ray irradiation is deployed to sterilize any female escapees. However, it remains unclear whether these irradiation-induced male and female sterilizations share common mechanisms.
Millions of Mosquitoes Will Rain Down on Hawaii to Save an Iconic Bird
28010S. Wild, Scientific American, 2023-10-06 06:53:13.
Millions of mosquitoes dropped from helicopters could be the greatest hope for Hawaii’s iconic honeycreepers. At least four species of the brightly colored birds could go extinct within the year if no action is taken to save them. “We’re seriously in a race against time at the moment,” says Hanna Mounce, program manager of the Maui Forest Bird Recovery Project. These small birds evolved on the islands over the course of millions of years and are uniquely adapted to their niche habitat, where they are crucial pollinators for many of Hawaii’s flora. For the people of Hawaii, the honeycreepers are also woven into the cultural fabric, featuring prominently in many legends and providing feathers for traditional garments. More than 50 species of honeycreepers once flitted across the archipelago, but because of introduced predators, habitat destruction and disease, that number has dwindled to only 17. Invasive Culex quinquefasciatus mosquitoes—possibly introduced via water barrels on European ships in the early 19th century—pose a particular threat because they spread the deadly avian malaria parasite.IIT works like this: C. quinquefasciatus mosquitoes, as well as many other arthropods, naturally contain Wolbachia bacteria in their gut. In order to produce offspring together, mating mosquitoes must be infected with the same strain of the bacteria. Birds, Not Mosquitoes’ plan involves releasing male mosquitoes bred by Verily Life Sciences—the life sciences research arm of Alphabet, which also owns Google. These mosquitos will host a different Wolbachia strain than those on Maui. The idea is that the existing female mosquitoes will mate with the male newcomers, but because of their incompatible Wolbachia bacteria, they will not produce viable offspring. If all goes according to plan, the overall mosquito population will plummet.
Molecular Evidence of Wolbachia Species in Wild-Caught Aedes albopictus and Aedes aegypti Mosquitoes in Four States of Northeast India
27843Vinayagam, S. Nirmolia, T. Chetry, S. Kumar, N. P. Saini, P. Bhattacharyya, D. R. Bhowmick, I. P. Sattu, K. Patgiri, S. J., Journal of Tropical Medicine, 2023-09-05 09:37:52.
Wolbachia, a Gram-negative intracellular bacterium, naturally infects many arthropods, including mosquito vectors responsible for the spread of arboviral diseases such as Zika, chikungunya, and dengue fever. Certain Wolbachia strains are involved in inhibiting arbovirus replication in mosquitoes, and this phenomenon is currently being studied to combat disease vectors. A study was conducted in four states in north-eastern India to investigate the presence of natural Wolbachia infection in wild-caught Aedes albopictus and Aedes aegypti mosquitoes, the established vectors of dengue. The detection of a Wolbachia infection was confirmed by nested PCR and sequencing in the two mosquito species Ae. aegypti and Ae. albopictus. Positivity rates observed in Ae. aegypti and Ae. albopictus pools were 38% (44 of 115) and 85% (41 of 48), respectively, and the difference was significant (chi-square = 28.3174, p = 0.00000010). Sequencing revealed that all detected Wolbachia strains belonged to supergroup B. Although Wolbachia infection in Ae. aegypti has been previously reported from India, no such reports are available from north-eastern India. Data on naturally occurring Wolbachia strains are essential for selecting the optimal strain for the development of Wolbachia-based control measures. This information will be helpful for the future application of Wolbachia-based vector control measures in this part of the country.
First Detection and Genetic Identification of Wolbachia Endosymbiont in Field-Caught Aedes aegypti (Diptera: Culicidae) Mosquitoes Collected from Southern Taiwan
27713L.-L. Chao and C.-M. Shih, Microorganisms, 11. 2023-07-23 09:53:12.
The prevalence and genetic character of Wolbachia endosymbionts in field-collected Aedes aegypti mosquitoes were examined for the first time in Taiwan. A total of 665 Ae. aegypti were screened for Wolbachia infection using a PCR assay targeting the Wolbachia surface protein (wsp) gene. In general, the prevalence of Wolbachia infection was detected in 3.3% Ae. aegypti specimens (2.0% female and 5.2% male). Group-specific Wolbachia infection was detected with an infection rate of 1.8%, 0.8% and 0.8% in groups A, B and A&B, respectively. Genetic analysis demonstrated that all Wolbachia strains from Taiwan were phylogenetically affiliated with Wolbachia belonging to the supergroups A and B, with high sequence similarities of 99.4–100% and 99.2–100%, respectively. Phylogenetic relationships can be easily distinguished by maximum likelihood (ML) analysis and were congruent with the unweighted pair group with the arithmetic mean (UPGMA) method. The intra- and inter-group analysis of genetic distance (GD) values revealed a lower level within the Taiwan strains (GD < 0.006 for group A and GD < 0.008 for group B) and a higher level (GD > 0.498 for group A and GD > 0.286 for group B) as compared with other Wolbachia strains. Our results describe the first detection and molecular identification of Wolbachia endosymbiont in field-caught Ae. aegypti mosquitoes collected from Taiwan, and showed a low Wolbachia infection rate belonging to supergroups A and B in Ae. aegypti mosquitoes.
Modeling the Impact of Migration on Mosquito Population Suppression
27422M. Huang and J. Yu, Qualitative Theory of Dynamical Systems, 22:134. 2023-07-17 08:45:23.
The Wolbachia-induced incompatible insect technique is a promising strategy for controlling wild mosquito populations. However, recent experimental studies have shown that mosquito migration into target areas dilutes the strategy’s effectiveness. In this work, we formulate a delay differential equation model to assess the impact of migration on mosquito population suppression. We identify that mosquito migration into an idealized target area makes it impossible to eliminate the target population completely. Our analysis identifies a lower bound of the suppression rate $$gamma ^*$$for a given migration number, which reveals the possible maximum reduction of wild population size in the peak season. For a given suppression rate target $$gamma _0>gamma ^*$$, we identify the permitted maximum migration number $$D(gamma _0)$$, above which is impossible to reduce the field mosquito density up to $$(1-gamma _0)times 100%$$in peak season. To reduce more than $$95%$$of Aedes albopictus population during its peak season in Guangzhou within six weeks, the required minimum release number of Wolbachia-infected males climbs steeply as the migration number increases to D(0.05).
Estimating mosquito abundance and population suppression in an incompatible insect technique study
26901L. Griffin, D. Pagendam, C. Drovandi, B. Trewin and N. W. Beebe, Journal of Applied Ecology, 2023-07-10 10:53:08.
Our model can provide valuable insights that can shape decision support systems in sterile insect technique and incompatible insect technique programmes operating over large geographical scales. The model helps determine how many sterile/incompatible insects should be released over time and how population control is progressing (via use of counterfactual scenarios). These outcomes are achieved because the model provides estimates of wild-type populations over time, even when there has been no differentiation between sterile/incompatible and wild-type insects caught in trap
Draft environmental assessment released for using modified mosquitoes to save native birds on Kauaʻi
26244Anonymous, Big Island NOW, 2023-06-23 07:24:12.
Today, the draft environmental assessment was made public for the use of Wolbachia-based incompatible male mosquitoes on Kauaʻi to stop the spread of avian malaria that is decimating native forest bird populations. The public has 31 days — from June 23 until July 24 — to comment on the draft, which was released by the U.S. Fish and Wildlife Service and the State of Hawaiʻi Division of Forestry and Wildlife. Hawaiʻi’s forest birds are facing an extinction crisis, with avian malaria a major factor. It is transmitted by non-native mosquitoes and just a single bite from an infected mosquito can be deadly. Of Kauaʻi’s 16 native honeycreepers, 10 have gone extinct and three are listed under the Endangered Species Act as threatened or endangered.
Draft environmental assessment for use of Wolbachia-based incompatible insect technique for the suppression of nonnative southern house mosquito populations on Kauaʻi
26247Hawai'i Department of Land and Natural Resources, Hawai'i Department of Land and Natural Resources, 2023-06-16 07:31:10.
The State of Hawai'i Department of Land and Natural Resources hereby transmits the Draft Environmental Assessment and Anticipated Finding of No Significant Impact (DEAEnvironmental Assessment for use of Wolbachia-based Incompatible Insect Technique for the suppression of nonnative southern house mosquito populations o Kaua'i to be published in the next available edition of The Environmental Notice.
Molecular detection of reproductive symbionts and parthenogenesis experiments in Tuta absoluta from Argentina: facing potential for sustainable and specific pest control strategies
26184C. Cagnotti, C. Conte, J. Kramar, S. Lanzavecchia and S. López, Entomologia Experimentalis et Applicata, 2023-06-07 12:24:43.
Tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is a key pest of tomato crops. Specific and environmentally friendly control strategies against this pest, such as the sterile insect technique (SIT), are under development and sexual reproduction has emerged as a key focal point to ensure its success. In the present study, we analyzed four representative T. absoluta populations from Argentina, focusing on the molecular detection of endosymbionts potentially associated with reproductive abnormalities and on determining whether parthenogenesis can occur under laboratory conditions. Larvae of T. absoluta were collected in commercial tomato plantations from La Plata and Mar del Plata (both in Buenos Aires province), Bella Vista (Corrientes province), and Yuto (Jujuy province). Tuta absoluta adults were evaluated by standard PCR for the presence of reproductive endosymbionts (Wolbachia sp., Spiroplasma sp., Arsenophonus sp., Cardinium sp., and Rickettsia sp.). For parthenogenesis assays, 20–23 virgin females from each T. absoluta geographic population were life-long isolated in Petri dishes with a tomato leaf. Fecundity, fertility, and female longevity were estimated and compared with results from mated females from each population. Our results showed the presence of a unique endosymbiont (Wolbachia sp. supergroup B, sequence type 41). Fecundity of the unmated females was significantly lower than fecundity of mated females in all T. absoluta populations. In addition, unmated females only laid infertile eggs. In conclusion, the absence of parthenogenesis in T. absoluta from representative geographic populations supports the implementation of SIT and mating disruption as effective control strategies against this pest in Argentina. © 2023 Netherlands Entomological Society.
The optimal strategy of incompatible insect technique (IIT) using Wolbachia and the application to malaria control
25203T. Matsufuji and S. Seirin-Lee, Journal of Theoretical Biology, 569:111519. 2023-05-29 09:18:33.
For decades, techniques to control vector population with low environmental impact have been widely explored in both field and theoretical studies. The incompatible insect technique (IIT) using Wolbachia, based on cytoplasmic incompatibility, is a technique that Wolbachia-infected male mosquitoes are incapable of producing viable offspring after mating with wild-type female mosquitoes. While the IIT method experimentally ensured its effectiveness in several field works, the failure of female mosquito population control by replacement owing to the accidental contamination of Wolbachia-infected female mosquitoes has been a concern and an obstacle in implementing the IIT method in nature. In this study, we develop a population-based IIT mathematical model using cytoplasmic incompatibility and evaluate the effectiveness of the IIT method in scenarios where contamination is present or absent. In addition, by extending the model to assess the disease infection status of the human population with malaria, we evaluate the optimal release strategy and cost for successful disease control. Our study proves that IIT could be a promising method to control mosquito-borne diseases without perfect suppression of vector mosquito population regardless of contamination.
The prevalence of Wolbachia in multiple cockroach species and its implication for urban insect management
25869S. O. Oladipupo, Y. Laidoudi, J. F. Beckmann, X. P. Hu and A. G. Appel, Journal of Economic Entomology, 2023-05-29 08:56:29.
Cockroach management relies heavily on the use of conventional insecticides in urban settings, which no longer provide the anticipated level of control. Knowledge of cockroach endosymbionts, like Wolbachia, might provide novel avenues for control. Therefore, we screened 16 cockroach species belonging to 3 families (Ectobiidae, Blattidae, and Blaberidae) for the presence of Wolbachia. We mapped the evolution of Wolbachia-cockroach relationships based on maximum likelihood phylogeny and phylogenetic species clustering on a multi-loci sequence dataset (i.e., coxA, virD4, hcpA, and gatB) of Wolbachia genes. We confirmed the previous report of Wolbachia in 1 Ectobiid species; Supella longipalpa (Fab.), and detected the presence of Wolbachia in 2 Ectobiid species; Balta notulata (Stål) and Pseudomops septentrionalis Hebard, and 1 Blaberid species; Gromphadorhina portentosa (Schaum). All cockroach-associated Wolbachia herein detected were clustered with the ancestor of F clade Wolbachia of Cimex lectularius L. (bed bugs). Since Wolbachia provision C. lectularius with biotin vitamins that confer reproductive fitness, we screened the cockroach-associated Wolbachia for the presence of biotin genes. In toto, our results reveal 2 important findings: (i) Wolbachia is relatively uncommon among cockroach species infecting about 25% of species investigated, and (ii) cockroach-associated Wolbachia have biotin genes that likely provide nutritional benefits to their hosts. Thus, we discuss the potential of exploring Wolbachia as a tool for urban insect management.
CRISPR-based gene editing of non-homologous end joining factors biases DNA repair pathway choice toward single-strand annealing in Aedes aegypti
25461K. Chae, J. M. Overcash, C. Dawson, C. Valentin, H. Tsujimoto, K. M. Myles and Z. N. Adelman, Current Research in Biotechnology, 5:100133. 2023-05-29 08:04:22.
To maintain genome stability, eukaryotic cells orchestrate DNA repair pathways to process DNA double-strand breaks (DSBs) that result from diverse developmental or environmental stimuli. Bias in the selection of DSB repair pathways, either non-homologous end joining (NHEJ) or homology-directed repair (HDR), is also critical for efficient gene editing and for homing-based gene drive approaches developed for the control of disease-transmitting vector mosquitoes. However, little is understood about DNA repair homeostasis in the mosquito genome. Here, we utilized CRISPR/Cas9 to generate indel mutant strains for core NHEJ factors ku80, DNA ligase IV (lig4), and DNA-PKcs in the mosquito Aedes aegypti and evaluated the corresponding effects on DNA repair. In a plasmid-based assay, disruption of ku80 or lig4, but not DNA-PKcs, reduced both NHEJ and SSA. However, a transgenic reporter strain-based test revealed that those mutations significantly biased DNA repair events toward SSA. Interestingly, ku80 mutation also significantly increased the end joining rate by a yet-characterized mechanism in males. Our study provides evidence that the core NHEJ factors have an antagonistic effect on SSA-based DSB repair of the Ae. aegypti genome. Down-modulating the NHEJ pathway can enhance the efficiency of nuclease-based genetic control approaches, as most of those operate by homology-based repair processes along with extensive DNA end resection that is antagonized by NHEJ.
Editorial: Genetic control of insect pest species—achievements, challenges, and perspectives
25423I. Häcker, D. Bartsch, A. Choo and F. Marec, Frontiers in Bioengineering and Biotechnology, 11. 2023-05-05 08:12:07.
Genetic control is a type ofbiological control and a promising approach to regulate insect pest populations in a species-specific manner. It is based on targeting the reproductive capacity of the target pest species to reduce population size to non-critical levels. The best known and also very successful genetic control strategy is the Sterile Insect Technique (SIT), which entails the continuous mass-release ofirradiation-sterilized males ofa given species to produce infertile matings in the field, leading to the decline in the target population over time. To date, SIT is only available for a few species, as its transfer to new target species is challenging and time consuming. Key aspects of this classical SIT and challenges in applying it to new pest species include mass rearing of target species, mass removal of female insects prior to irradiation and release, the sterilization procedure, and the biological quality control of the sterile insects produced. Besides this classical SIT strategy, current research efforts are also focused on the development of genetic control approaches based on transgenic, symbiont-mediated, or gene-drive strategies. Modern genetic technologies offer new solutions for the improvement of existing genetic control strategies and insect strains, for faster and easier transfer of existing strategies to new target species, and also for the development of new genetic control approaches. Publications within this Research Topic address pressing questions and challenges related to the genetic control of insect pests.
Wolbachia-based strategies for control of agricultural pests
25104J. T. Gong, T. P. Li, M. K. Wang and X. Y. Hong, Curr Opin Insect Sci, 101039:10.1016/j.cois.2023.101039. 2023-04-25 10:26:15.
Wolbachia-based incompatible insect technique (IIT) and pathogen blocking technique (PBT) have been shown to be effective at protecting humans from mosquito-borne diseases in the past decades. Population suppression based on IIT and population replacement based on PBT have become major field application strategies that have continuously been improved by the translational research on Wolbachia-transinfected mosquitoes. Similarly, Wolbachia-based approaches have been proposed for the protection of plants from agricultural pests and their associated diseases. However, a bottleneck in Wolbachia-based strategies for the control of agricultural pests is the need for methods to establish Wolbachia-transinfected insect lines. As a first step in this direction, we compare field control strategies for mosquitos with the potential strategies for agricultural pests based on Wolbachia. Our results show that there is a critical need for establishing productive insect lines and accumulating field test data.
The Role of Symbiont-Targeted Strategies in the Management of Pentatomidae and Tephritidae Pests under an Integrated Vision
24996E. Gonella and A. Alma, Agronomy, 13. 2023-04-21 15:11:32.
The interaction between insects and gut bacterial symbionts is, nowadays, regarded as an important element in the implementation of pest management, in consideration of the urgent need for sustainable alternatives to insecticide use. In this framework, a major tool is symbiotic control, with the main ready-to-use application represented by the interruption of obligate symbioses. Two insect families, namely Pentatomidae in the Hemiptera order and Tephritidae in Diptera, have been indicated as outstanding targets for symbiont-oriented control tactics. An important advantage of interrupting obligate symbioses is the target shift from insect to bacteria, which avoids insecticide use; however, the compatibility between this approach and other pest/disease management strategies is crucial to design low-impact pest control programs. Here we present the state of knowledge regarding the integration of symbiont manipulation in sustainable plant protection plans. Research assessing the potential for multitarget applications is reported, as well as studies on the impact of symbiont interruption on nontarget species. Besides symbiont-targeted pest control, another relevant outcome of symbiont manipulation is the restoration of microbial perturbation in mass-reared insects used in pest control programs, which is a required step to allow the success of other tactics, such as the Sterile Insect Technique. Despite the potential contribution that symbiont-targeted strategies may offer to integrated pest management, we point out that operational caveats may emerge in symbiont-oriented control in relation to the target extension on the label directions and to the number of required treatments. Future work is needed to increase the target range and the number of tested formulations exploiting the interruption of bacterial symbioses. This will also require assessment of the effect of different products on beneficial organisms, including biological control agents. Finally, the authorization of formulates for symbiotic control should be taken into consideration by the regulatory bodies, to really promote new readily available control options. © 2023 by the authors.
A bacterium against the tiger: further evidence of the potential of non-inundative releases of males with manipulated Wolbachia infection in reducing fertility of Aedes albopictus field populations in Italy
24966B. Caputo, R. Moretti, C. Virgillito, M. Manica, E. Lampazzi, G. Lombardi, P. Serini, V. Pichler, N. W. Beebe, A. Della Torre and M. Calvitti, Pest Management Science, 2023-04-06 10:42:30.
BACKGROUND: Incompatible Insect Technique (IIT) is a population suppression approach based on the release of males with manipulated Wolbachia infection inducing egg inviability in wild females. We here present results of multiple field releases of incompatible ARwP males carried out in 2019 in a 2.7-ha green area within urban Rome (Italy) to assess the effect on Ae. albopictus egg viability. Data are compared with results obtained in 2018, when the approach was tested for the first time in Europe. RESULTS: An average of 4,674 ARwP males were released weekly for 7 weeks, resulting in a mean ARwP/wild male ratio of 1.1:1 (versus 0.7:1 in 2018). Egg-viability dynamics in ovitraps significantly varied between Treated and Control Sites, with an estimated overall reduction of 35% (versus 15% in 2018). The estimated proportion of females classified as mated with ARwP males was 41.8% and the viability rate of eggs laid by these females (9.5%) was on average significantly lower than that of females only mated with wild males (87.8%); however, high variability in fertility was observed. Values of ARwP male competitiveness were 0.36 and 0.73 based on the overall viability rate of eggs in ovitraps and on female fertility, respectively, i.e. well above the conventional 0.2 threshold for an effective suppressive impact in the field. CONCLUSIONS: Results further support the potential of IIT as a tool to contribute to Ae. albopictus control in the urban context, stressing the need of larger field trials to evaluate the cost-efficacy of the approach in temperate regions.
First report of natural Wolbachia infections in mosquitoes from Cuba
24933A. Ruiz, G. Gutiérrez-Bugallo, R. Rodríguez-Roche, L. Pérez, R. González-Broche, L. A. Piedra, L. C. Martínez, Z. Menéndez, A. Vega-Rúa and J. A. Bisset, Acta Tropica, 242:106891. 2023-03-11 08:20:20.
Mosquitoes are extensively responsible for the transmission of pathogens. Novel strategies using Wolbachia could transform that scenario, since these bacteria manipulate mosquito reproduction, and can confer a pathogen transmission-blocking phenotype in culicids. Here, we screened the Wolbachia surface protein region by PCR in eight Cuban mosquito species. We confirmed the natural infections by sequencing and assessed the phylogenetic relationships among the Wolbachia strains detected. We identified four Wolbachia hosts: Aedes albopictus, Culex quinquefasciatus, Mansonia titillans, and Aedes mediovittatus (first report worldwide). Knowledge of Wolbachia strains and their natural hosts is essential for future operationalization of this vector control strategy in Cuba.
Wolbachia pipientis infections in populations of Aedes albopictus in the city of València (Spain): implications for mosquito control
24830R. Bueno-Marí, R. Domínguez-Santos, M. Trelis, E. Garrote-Sánchez, M. Cholvi, F. Quero de Lera, M. Khoubbane, A. Marcilla and R. Gi, Revista Española de Salud Pública, 97. 2023-03-02 16:20:52.
OBJECTIVE: The presence of Aedes albopictus, of high sanitary and social impact, was first reported in Valencia (Eastern Spain) in 2015. Innovative tools for its control include the use of the endosymbiotic bacterium Wolbachia pipientis. The release of mosquito males infected with the wPip strain, has proven very promising for large-scale Incompatible Insect Technique (IIT) applications. Before this strategy can be implemented in Valencia, it is important to know whether the natural local mosquito populations are Wolbachia-infected and, if so, identifying the infecting strains/supergroups, these being the objectives of the present work. METHODS: Eggs were collected from the 19 districts of the València city between May and October 2019. A total of 50 lab-reared adult Ae. albopictus individuals were processed and analyzed for Wolbachia detection and molecular characterization. These actions took place within the framework of a collaboration established with the Department of Health and Consumer Affairs of the city council of Valencia. Fisher's exact test was used to detect the statistical significance of the differences between groups. RESULTS: Our study revealed that 94% of the analyzed samples were naturally infected with Wolbachia. Both wAlbA and wAlbB supergroups were identified, with most samples (72% of the infected ones) carrying co-infections. CONCLUSIONS: These data provide the first characterization of the Wolbachia presence in natural populations of Ae. albopictus in the Mediterranean area of Spain. This information is relevant to evaluate the potential use of Wolbachia strains in order to achieve the suppression of the Asian tiger mosquito populations through massive release of artificially-infected males.
Satellite Rearing of Aedes Mosquito Eggs: Synchronized Empirical Test of a Novel Mass Rearing Model
24981K. L. Dobson, K. Blore, J. A. Henke, K. Y. Hung, T. Morgan, T. Posey, S. Sun, O. Sypes, N. P. Tremblay and S. L. Dobson, J Am Mosq Control Assoc, 39:12-17. 2023-03-01 09:41:35.
Mosquito suppression strategies based on "rear and release" of male mosquitoes are attracting renewed interest from governments, municipalities, and private businesses. These include irradiation-based sterile insect technique, Wolbachia-based technologies, and genetic modification. Each of these approaches requires the mass rearing and release of adult male mosquitoes, which typically is accomplished via a rearing facility near the release site. Although some release programs have relied on centralized rearing and shipment of adult males, adult male mosquitoes are relatively fragile, and their fitness can be diminished by temperature fluctuations, humidity, nutritional deficiencies, and other stresses that occur during shipment. Furthermore, expensive, expedited shipment is typically used to maximize the amount of adult lifetime in the field following the release. In contrast, Aedes aegypti and Ae. albopictus eggs can be desiccated and stored for long periods. They are small, and many millions of eggs can be shipped without specialized environmental conditions and using less expensive means. Here we examine a model in which mosquito eggs are centrally produced and then mailed to satellite rearing facilities. As a control, a replicate set of eggs was reared at the factory of origin. At each of the rearing sites, cloud-based software was used to track and compare rearing at the different locations. The results demonstrate similar rearing outcomes (i.e., egg hatch, immature development, and number of adult males) at each of the different sites for both species. We discuss the outcome in relation to downstream applications and potential future studies.
When less is more: accounting for overcompensation in mosquito SIT projects
24717J. Bouyer, Trends in Parasitology, 2023-02-08 10:14:35.
Compensation and overcompensation under field conditions are confirmed in Aedes mosquitoes recently by Evans et al.: equal or increased densities of emerging adults may thus result from reduced larval densities. Here the consequences when applying the sterile insect technique and provide recommendations to avoid counterproductive effects are discussed.
Joint FAO/IAEA Coordinated Research Project on Mosquito Handling, Transport, Release and Male Trapping Methods in Support of SIT Application to Control Mosquitoes
24566M. Gómez, B. J. Johnson, H. C. Bossin and R. Argilés-Herrero, Insects, 14. 2023-01-19 08:14:17.
The research carried out in the framework of this CRP generated key achievements in areas relevant to the SIT application to control mosquitoes. Among these outcomes, particular mentions must be given to the following: (1) Novel and efficient self-marking techniques were established to improve our understanding of male movement, competitiveness, survival, and potential interaction with closely related species post-release [7,8]. As the next step, these new marking systems will be upscaled and validated under operational conditions in SIT field projects targeting the Aedes species. (2) One of the techniques evaluated included the novel large-scale marking of male mosquitoes via administration of Rhodamine B via sugar feeding. The mentioned technique brings the advantage of marking all of the tissues of the mosquitoes, including sperm and seminal fluid, such that the mark can be retrieved and identified in mated females. Thus, the use of Rhodamine B enables researchers to estimate the sexual competitiveness of sterile male mosquitoes under field conditions [9,10].
Survival-Larval Density Relationships in the Field and Their Implications for Control of Container-Dwelling Aedes Mosquitoes
24714K. G. Evans, Z. R. Neale, B. Holly, C. C. Canizela and S. A. Juliano, Insects, 14. 2022-12-23 10:10:37.
Population density can affect survival, growth, development time, and adult size and fecundity, which are collectively known as density-dependent effects. Container Aedes larvae often attain high densities in nature, and those densities may be reduced when larval control is applied. We tested the hypothesis that density-dependent effects on survival are common and strong in nature and could result in maximal adult production at intermediate densities for Aedes aegypti, Aedes albopictus, and Aedes triseriatus. We surveyed naturally occurring densities in field containers, then introduced larvae at a similar range of densities, and censused the containers for survivors. We analyzed the survival-density relationships by nonlinear regressions, which showed that survival-density relationships vary among seasons, sites, and species. For each Aedes species, some sites and times yielded predictions that larval density reduction would yield the same (compensation), or more (overcompensation), adults than no larval density reduction. Thus, larval control targeting these Aedes species cannot always be assumed to yield a reduction in the number of adult mosquitoes. We suggest that mosquito control targeting larvae may be made more effective by: Imposing maximum mortality; targeting populations when larval abundances are low; and knowing the shape of the survival-density response of the target population.
Assessing the efficacy of male Wolbachia-infected mosquito deployments to reduce dengue incidence in Singapore: study protocol for a cluster-randomized controlled trial
24268J. Ong, S. H. Ho, S. X. H. Soh, Y. Wong, Y. Ng, K. Vasquez, Y. L. Lai, Y. X. Setoh, C. S. Chong, V. Lee, J. C. C. Wong, C. H. Tan, S. Sim, L. C. Ng and J. T. Lim, Trials, 23:1023. 2022-12-17 13:57:59.
The study is designed as a parallel, two-arm, non-blinded cluster-randomized (CR) controlled trial to be conducted in high-rise public housing estates in Singapore, an equatorial city-state. The aim is to determine whether large-scale deployment of male Wolbachia-infected Ae. aegypti mosquitoes can significantly reduce dengue incidence in intervention clusters. We will use the CR design, with the study area comprising 15 clusters with a total area of 10.9 km(2), covering approximately 722,204 residents in 1713 apartment blocks. Eight clusters will be randomly selected to receive the intervention, while the other seven will serve as non-intervention clusters. Intervention efficacy will be estimated through two primary endpoints:
East Maui project hopes mosquito v. mosquito mating battle will save endangered birds
24173K. Cerizo, MAUINOW, 2022-12-11 11:03:34.
A mass rearing cost calculator for the control of Culex quinquefasciatus in Hawaiʻi using the incompatible insect technique
24332A. E. Vorsino and Z. Xi, Parasites and Vectors, 15:453. 2022-12-05 08:32:07.
Hawaiʻi’s native forest avifauna is experiencing drastic declines due to climate change-induced increases in temperature encroaching on their upper-elevation montane rainforest refugia. Higher temperatures support greater avian malaria infection rates due to greater densities of its primary vector, the southern house mosquito Culex quinquefasciatus, and enhance development of the avian malaria parasite Plasmodium relictum. Here we propose the use of the incompatible insect technique (IIT) or the combined IIT/sterile insect technique (SIT) for the landscape-scale (i.e., area-wide) control of Cx. quinquefasciatus, and have developed a calculator to estimate the costs of IIT and IIT/SIT applications at various sites in Hawaiʻi.
Effect of Wolbachia Infection and Adult Food on the Sexual Signaling of Males of the Mediterranean Fruit Fly Ceratitis capitata
23487G. A. Kyritsis, P. Koskinioti, K. Bourtzis and N. T. Papadopoulos, Insects, 13. 2022-08-17 07:10:32.
Sexual signaling is a fundamental component of sexual behavior of Ceratitis capitata that highly determines males' mating success. Nutritional status and age are dominant factors known to affect males' signaling performance and define the female decision to accept a male as a sexual partner. Wolbachia pipientis, a widespread endosymbiotic bacterium of insects and other arthropods, exerts several biological effects on its hosts. However, the effects of Wolbachia infection on the sexual behavior of medfly and the interaction between Wolbachia infection and adult food remain unexplored. This study was conducted to determine the effects of Wolbachia on sexual signaling of protein-fed and protein-deprived males. Our findings demonstrate that: (a) Wolbachia infection reduced male sexual signaling rates in both food regimes; (b) the negative effect of Wolbachia infection was more pronounced on protein-fed than protein-deprived males, and it was higher at younger ages, indicating that the bacterium regulates male sexual maturity; (c) Wolbachia infection alters the daily pattern of sexual signaling; and (d) protein deprivation bears significant descent on sexual signaling frequency of the uninfected males, whereas no difference was observed for the Wolbachia-infected males. The impact of our findings on the implementation of Incompatible Insect Technique (IIT) or the combined SIT/IIT towards controlling insect pests is discussed.
Studies on the fitness characteristics of wMel- and wAlbB-introgressed Aedes aegypti (Pud) lines in comparison with wMel- and wAlbB-transinfected Aedes aegypti (Aus) and wild-type Aedes aegypti (Pud) lines
23485C. Sadanandane, K. Gunasekaran, D. Panneer, S. K. Subbarao, M. Rahi, B. Vijayakumar, V. Athithan, A. Sakthivel, S. Dinesh and P. Jambulingam, Frontiers in Microbiology, 13:947857. 2022-08-05 07:02:55.
Wolbachia, an intracellular maternally transmitted endosymbiont, has been shown to interfere with the replication of dengue virus in Aedes aegypti mosquitoes. The Wolbachia-transinfected Ae. aegypti has been currently released in many countries to test its effectiveness in preventing the transmission of dengue virus. ICMR-Vector Control Research Centre in collaboration with World Mosquito Program Monash University, Australia, has generated two new Wolbachia-introgressed Ae. aegypti Puducherry (Pud) lines via backcrossing Ae. aegypti females of Australian (Aus) strains, infected with wMel and wAlbB Wolbachia with wild-type Ae. aegypti Puducherry (Pud) males. Wolbachia infections are known to induce a fitness cost and confer benefit on the host mosquito populations that will influence spread of the Wolbachia into native wild mosquito populations during the field release. Hence, the induced fitness cost or benefit/advantage in the two newly generated Ae. aegypti (Pud) lines was assessed in the laboratory in comparison with the wild-type Ae. aegypti (Pud) strain. In addition, maternal transmission (MT) efficiency, induced cytoplasmic incompatibility (CI), and insecticide resistance status of the two (Pud) lines were determined to assess the likely frequency of wMel and wAlbB infections in the native wild population after field invasion. The study shows that wMel and wAlbB infections did not induce any fitness cost on the two newly generated (Pud) lines. Rather, in terms of wing length, fecundity, egg hatch rate, and adult survival, the Wolbachia introgression conferred fitness benefits on the (Pud) lines compared to uninfected Wolbachia free wild Ae. aegypti population. wMel and wAlbB exhibited a high maternal transmission (99-100%) and induced nearly complete (98-100%) cytoplasmic incompatibility. Both the (Pud) lines were resistant to deltamethrin, malathion, DDT, and temephos, and the level of resistance was almost the same between the two lines as in the wild type. Overall, the stable association of wMel and wAlbB established with Ae. aegypti and the reproductive advantages of the (Pud) lines encourage a pilot release in the field for population replacement potential.
Wolbachia Dynamics in Mosquitoes with Incomplete CI and Imperfect Maternal Transmission by a DDE System
23393Y. Su, B. Zheng and X. Zou, Bulletin of Mathematical Biology, 84:95. 2022-08-01 08:09:11.
In this paper, we propose a delay differential equation model to describe the Wolbachia infection dynamics in mosquitoes in which the key factor of cytoplasmic incompactibility (CI) is incorporated in a more natural way than those in the literature. By analyzing the dynamics of the model, we are able to obtain some information on the impact of four important parameters: the competition capabilities of the wild mosquitoes and infected mosquitoes, the maternal transmission level and the CI level. The analytic results show that there are ranges of parameters that support competition exclusion principle, and there are also ranges of parameters that allow co-persistence for both wild and infected mosquitoes. These ranges account for the scenarios of failure of invasion, invasion and suppressing the wild mosquitoes, and invasion and replacing the wild mosquitoes. We also discuss some possible future problems both in mathematics and in modeling.
Sensitivity of wMel and wAlbB Wolbachia infections in Aedes aegypti Puducherry (Indian) strains to heat stress during larval development
23056K. Gunasekaran, C. Sadanandane, D. Panneer, A. Kumar, M. Rahi, S. Dinesh, B. Vijayakumar, M. Krishnaraja, S. K. Subbarao and P. Jambulingam, Parasites and Vectors, 15:221. 2022-06-21 15:19:54.
BACKGROUND: ICMR-Vector Control Research Centre, Puducherry, India, developed two colonies of Aedes aegypti infected with wMel and wAlbB Wolbacia strains called Ae. aegypti (Pud) lines for dengue control. The sensitivity of wMel and wAlbB strains in Ae. aegypti (Pud) lines to heat stress was studied. METHODS: wMel and wAlbB infected and uninfected Ae. aegypti larvae (first to fourth instars) were reared in the laboratory to adults at 26 °C, 30 °C, 36 °C and 40 °C constant temperatures and also 26-30 °C, 26-36 °C and 26-40 °C diurnal cyclic temperatures. The adults were tested for Wolbachia infection. Experiments were also carried out rearing the larvae under simulated field conditions in summer (April and June) under sunlight using fully open and half open bowls and also under sunlight and natural shade. RESULTS: At 36 °C and 40 °C constant temperatures, complete larval mortality was observed. At 30 °C and 26 °C, no larval mortality occurred, but Wolbachia density was relatively low in wMel infected males compared to control (maintained at 26 ± 1 °C). At diurnal cyclic temperature of 26-40 °C, Wolbachia density was reduced in males of both the (Pud) lines, but not in females. At 26-36 °C, reduction in Wolbachia density was observed in wMel males but not in wAlbB males. At 26-30 °C, no significant reduction in Wolbachia density was observed with wMel and wAlbB strains. In simulated field conditions (April), under sunlight, the daytime water temperature reached a maximum of 35.7 °C in both full and half open bowls. No larval mortality occurred. Wolbachia frequency and density was reduced in wMel-infected Ae. aegypti (Pud) males from both type of bowls and in females from full open bowls, and in wAlbB males from half open bowls. In June, rearing of larvae under sunlight, the first-instar larvae experienced a maximum daytime water temperature of > 38 °C that caused complete mortality. No larval mortality was observed in bowls kept under shade (< 32 °C). CONCLUSIONS: Exposure of larvae to higher rearing temperatures in the laboratory and simulated-field conditions reduced the densities of wMel and wAlbB strains particularly in males, but the impact was more pronounced for wMel strain. The actual effect of heat stress on the stability of these two Wolbachia strains needs to be tested under natural field conditions.
Mosquito control to save Hawaiian honeycreepers does not involve GMOs
22859Department of Land and Natural Resources, Hawaii Department of Land and Natural Resources, 2022-06-08 08:42:00.
Despite misinformation circulating on social media, the importation of “incompatible-male” mosquitoes to control populations of wild mosquitoes and to save four native bird species from extinction, does not involve the use of any genetically modified organisms (GMOs) or genetically engineered (GE) organisms. On Thursday, the Plant and Animal Advisory Committee of the Dept. of Agriculture will consider listing three species of mosquitoes on its Restricted Species List A. The listing would allow the importation of three species of mosquitoes, all of which are already present in Hawai‘i. One of these, the Southern House Mosquito (Culex quinquefasciatus) isresponsible for sharp declines in the populations of many honeycreeper species on Kaua‘i, Maui, and Hawai‘i Island. The other two species – Yellow Fever Mosquito (Aedes aegypti) and Asian Tiger Mosquito (Aedes albopictus) – transmit human diseases.
Establishment of Wolbachia infection in Aedes aegypti from Pakistan via embryonic microinjection and semi-field evaluation of general fitness of resultant mosquito population
22856M. S. Sarwar, N. Jahan, A. Ali, H. K. Yousaf and I. Munzoor, Parasites and Vectors, 15:191. 2022-06-06 08:36:19.
BACKGROUND: Dengue is a mosquito-borne viral disease that is mainly spread by Aedes aegypti. It is prevalent on five continents, predominantly in tropical and sub-tropical zones across the world. Wolbachia bacteria have been extensively used in vector control strategies worldwide. The focus of the current study was to obtain a natural population of Ae. aegypti harbouring Wolbachia and to determine the impact of this bacteria on the new host in a semi-field environment. METHODS: Wolbachia-infected Aedes albopictus was collected from the city of Lahore, Punjab, Pakistan, and Wolbachia were successfully introduced into laboratory-reared Ae. aegypti via embryonic microinjection. The stable vertical transmission of wAlbB in the host population was observed for eight generations, and the impact of Wolbachia on the general fitness of the host was evaluated in semi-field conditions. RESULTS: In the laboratory and semi-field experiments, wAlbB Wolbachia presented a strong cytoplasmic incompatibility (CI) effect, evidenced as zero egg hatching, in crosses between Wolbachia-infected males and wild (uninfected) females of Ae. aegypti. Wolbachia infection had no noticeable impact on the general fitness (P > 0.05), fecundity, body size (females and males) and mating competitiveness of the new host, Ae. aegypti. However, there was a significant decrease in female fertility (egg hatch) (P < 0.001). In addition, under starvation conditions, there was a remarkable decrease (P < 0.0001) in the life span of Wolbachia-infected females compared to uninfected females (4 vs. > 5 days, respectively). CONCLUSIONS: Wolbachia strain wAlbB has a great potential to control the dengue vector in Ae. aegypti populations by producing 100% CI with a limited burden on its host in natural field conditions. This strain can be used as a biological tool against vector-borne diseases.
Wolbachia interacts with the microbiome to shape fitness-associated traits during seasonal adaptation in Drosophila melanogaster
22693L. P. Henry, M. Fernandez, S. Wolf and J. Ayroles, bioRxiv, 2022.05.31.494239. 2022-06-01 14:39:02.
The microbiome contributes to many different host traits, but its role in host adaptation remains enigmatic. The fitness benefits of the microbiome often depend on ecological conditions, but fluctuations in both the microbiome and environment modulate these fitness benefits. Moreover, vertically transmitted bacteria might constrain the ability of both the microbiome and host to respond to changing environments. Drosophila melanogaster provides an excellent system to investigate the evolutionary effects of interactions between the microbiome and the environment. To address this question, we created field mesocosms of D. melanogaster undergoing seasonal adaptation with and without the vertically transmitted bacteria, Wolbachia pipientis. Sampling temporal patterns in the microbiome revealed that Wolbachia constrained microbial diversity. Furthermore, interactions between Wolbachia and the microbiome contributed to fitness-associated traits. Wolbachia often exerted negative fitness effects on hosts, and the microbiome modulated these effects. Our work supports recent theoretical advances suggesting that hosts in temporally fluctuating environments benefit from flexible microbial associations with low transmission fidelity--specifically when changes in the microbiome can better enable host phenotypes to match environment change. We conclude by exploring the consequences of complex interactions between Wolbachia and the microbiome for our understanding of eco-evolutionary processes and the utility of Wolbachia in combating vector-borne disease.Competing Interest StatementThe authors have declared no competing interest.
Reply to: Assessing the efficiency of Verily’s automated process for production and release of male Wolbachia-infected mosquitoes
22643J. E. Crawford, K. C. Hopkins, A. Buchman, T. Zha, P. Howell, E. Kakani, J. R. Ohm, N. Snoad, L. Upson, J. Holeman, P. Massaro, S. L. Dobson, F. S. Mulligan and B. J. White, Nature Biotechnology, 2022-05-26 06:34:15.
We appreciate the comments from Bouyer et al. under their mandate as a United Nations agency program (‘to promote the safe and appropriate use of nuclear techniques and related technologies in food and agriculture’) on our paper1 . The centuries-old fight against mosquito-borne disease has entered a new phase that is both exciting and fast-moving. Many promising technologies and techniques have been developed in the past 2 decades, including mosquito colonies stably infected with Wolbachia2 mosquitoes3,4, a CRISPR–Cas9-based gene drive5 nations of these techniques with older approaches (that is, irradiated Wolbachia releases6,7 , genetically modified sterile and even combi). In a world where more than half of all humans are at risk of contracting mosquito-borne diseases across a range of economic and geographic landscapes, we think that an array of tools will be needed to turn the tide against the massive public health burden of these diseases.
Assessing the efficiency of Verily’s automated process for production and release of male Wolbachia-infected mosquitoes
22641J. Bouyer, H. Maiga and M. J. B. Vreysen, Nature Biotechnology, 2022-05-26 06:27:58.
A paper by Crawford et al.1 titled ‘Efficient production of male Wolbachia-infected Aedes aegypti mosquitoes enables large-scale suppression of wild populations’ reports a mosquito control suppression trial carried out from2017 to 2018 in Fresco Country, California, USA1 . Between 7.5 million and 14.4 million Wolbachia-infected male mosquitoes were released during the study, which achieved suppression rates of 69% and 95%, respectively. Although the work provided important insights for future Aedes genetic control programs—particularly the information on the immigration of fertile females into release areas—the paper contains several omissions and errors. Below, we discuss how these relate to three main areas: regulatory oversight, entomological efficiency and, finally, cost efficiency.
Strategies to Mitigate Establishment under the Wolbachia Incompatible Insect Technique
23104S. Soh, S. H. Ho, J. Ong, A. Seah, B. S. Dickens, K. W. Tan, J. R. Koo, A. R. Cook, S. Sim, C. H. Tan, L. C. Ng and J. T. Lim, Viruses, 14. 2022-05-24 08:10:53.
The Incompatible Insect Technique (IIT) strategy involves the release of male mosquitoes infected with the bacterium Wolbachia. Regular releases of male Wolbachia-infected mosquitoes can lead to the suppression of mosquito populations, thereby reducing the risk of transmission of vector-borne diseases such as dengue. However, due to imperfect sex-sorting under IIT, fertile Wolbachia-infected female mosquitoes may potentially be unintentionally released into the environment, which may result in replacement and failure to suppress the mosquito populations. As such, mitigating Wolbachia establishment requires a combination of IIT with other strategies. We introduced a simple compartmental model to simulate ex-ante mosquito population dynamics subjected to a Wolbachia-IIT programme. In silico, we explored the risk of replacement, and strategies that could mitigate the establishment of the released Wolbachia strain in the mosquito population. Our results suggest that mitigation may be achieved through the application of a sterile insect technique. Our simulations indicate that these interventions do not override the intended wild type suppression of the IIT approach. These findings will inform policy makers of possible ways to mitigate the potential establishment of Wolbachia using the IIT population control strategy.
Pilot trial using mass field-releases of sterile males produced with the incompatible and sterile insect techniques as part of integrated Aedes aegypti control in Mexico
22224A. Martín-Park, A. Che-Mendoza, Y. Contreras-Perera, S. Pérez-Carrillo, H. Puerta-Guardo, J. Villegas-Chim, G. Guillermo-May, A. Medina-Barreiro, H. Delfín-González, R. Méndez-Vales, S. Vázquez-Narvaez, J. Palacio-Vargas, F. Correa-Morales, G. Ayora-Tal, PLoS Negl Trop Dis, 16:e0010324. 2022-04-26 15:46:43.
We implemented a controlled before-and-after quasi-experimental study in two suburban localities of Yucatan (Mexico): San Pedro Chimay (SPC), which received IIT-SIT, and San Antonio Tahdzibichén used as control. Release of wAlbB Ae. aegypti males at SPC extended for 6 months (July-December 2019), covering the period of higher Ae. aegypti abundance. Entomological indicators included egg hatching rates and outdoor/indoor adult females collected at the release and control sites. Approximately 1,270,000 lab-produced wAlbB-infected Ae. aegypti males were released in the 50-ha treatment area (2,000 wAlbB Ae. aegypti males per hectare twice a week in two different release days, totaling 200,000 male mosquitoes per week). The efficacy of IIT-SIT in suppressing indoor female Ae. aegypti density (quantified from a generalized linear mixed model showing a statistically significant reduction in treatment versus control areas) was 90.9% a month after initiation of the suppression phase, 47.7% two months after (when number of released males was reduced in 50% to match local abundance), 61.4% four months after (when initial number of released males was re-established), 88.4% five months after and 89.4% at six months after the initiation of the suppression phase. A proportional, but lower, reduction in outdoor female Ae. aegypti was also quantified (range, 50.0-75.2% suppression). CONCLUSIONS/SIGNIFICANCE: Our study, the first open-field pilot implementation of Wolbachia IIT-SIT in Mexico and Latin-America, confirms that inundative male releases can significantly reduce natural populations of Ae. aegypti. More importantly, we present successful pilot results of the integration of Wolbachia IIT-SIT within a IVM plan implemented by Ministry of Health personnel.
Could species-focused suppression of Aedes aegypti, the yellow fever mosquito, and Aedes albopictus, the tiger mosquito, affect interacting predators? An evidence synthesis from the literature
20971J. A. S. Bonds, C. M. Collins and L.-C. Gouagna, Pest Management Science, 2022-03-16 07:20:33.
The risks of Aedes aegypti and Aedes albopictus nuisance and vector-borne diseases are rising and the adverse effects of broad-spectrum insecticide application has promoted species-specific techniques, such as sterile insect technique (SIT) and other genetic strategies, as contenders in their control operations. When specific vector suppression is proposed, potential effects on predators and wider ecosystem are some of the first stakeholder questions. These are not the only Aedes vectors of human diseases, but are those for which SIT and genetic strategies are of most interest. They vary ecologically and in habitat origin, but both have behaviourally human-adapted forms with expanding ranges. The aquatic life stages are where predation is strongest due to greater resource predictability and limited escape opportunity. These vectors' anthropic forms usually use ephemeral water bodies and man-made containers as larval habitats; predators that occur in these are mobile, opportunistic and generalist. No literature indicates that any predator depends on larvae of either species. As adults, foraging theory predicts these mosquitoes are of low profitability to predators. Energy expended hunting and consuming will mostly outweigh their energetic benefit. Moreover, as adult biomass is mobile and largely disaggregated, any predator is likely to be a generalist and opportunist. This work, which summarises much of the literature currently available on the predators of Ae. aegypti and Ae. albopictus, indicates it is highly unlikely that any predator species depends on them. Species-specific vector control to reduce nuisance and disease is thus likely to be of negligible or limited impact on non-target predators
Increased biting rate and decreased Wolbachia density in irradiated Aedes mosquitoes
20487R. Moretti, E. Lampazzi, C. Damiani, G. Fabbri, G. Lombardi, C. Pioli, A. Desiderio, A. Serrao and M. Calvitti, Parasites and Vectors, 15:67. 2022-02-24 08:48:28.
Releasing considerable numbers of radiation-sterilized males is a promising strategy to suppress mosquito vectors. However, releases may also include small percentages of biting females, which translate to non-negligible numbers when releases are large. Currently, the effects of irradiation on host-seeking and host-biting behaviors have not been exhaustively investigated. Information is also lacking regarding the effects of sterilizing treatment on the endosymbiotic bacterium Wolbachia, which is known to affect the vector competence of infected mosquitos.
Uniqueness and stability of periodic solutions for an interactive wild and Wolbachia-infected male mosquito model
20438R. Yan and Q. Sun, Journal of Biological Dynamics, 2022-02-15 09:03:48.
We investigate a mosquito population suppression model, which includes the release of Wolbachia-infected males causing incomplete cytoplasmic incompatibility (CI). The model consists of two sub-equations by considering the density-dependent birth rate of wild mosquitoes. By assuming the release waiting period T is larger than the sexual lifespan T¯ of Wolbachia-infected males, we derive four thresholds: the CI intensity threshold sh∗, the release amount thresholds g∗ and c∗, and the waiting period threshold T∗. From a biological view, we assume sh > sh∗ throughout the paper. When g∗ < c < c∗, we prove the origin E0 is locally asymptotically stable iff T < T∗, and the model admits a unique T-periodic solution iff T ≥ T∗, which is globally asymptotically stable. When c ≥ c∗, we show the origin E0 is globally asymptotically stable iff T ≤ T∗, and the model has a unique T-periodic solution iff T > T∗, which is globally asymptotically stable. Our theoretical results are confirmed by numerical simulations.
Genetically engineered insects with sex-selection and genetic incompatibility enable population suppression
20286A. Upadhyay, N. R. Feltman, A. Sychla, A. Janzen, S. R. Das, M. Maselko and M. Smanski, eLife, 11. 2022-02-02 11:49:30.
Engineered Genetic Incompatibility (EGI) is a method to create species-like barriers to sexual reproduction. It has applications in pest control that mimic Sterile Insect Technique when only EGI males are released. This can be facilitated by introducing conditional female-lethality to EGI strains to generate a sex-sorting incompatible male system (SSIMS). Here, we demonstrate a proof of concept by combining tetracycline-controlled female lethality constructs with a pyramus-targeting EGI line in the model insect Drosophila melanogaster. We show that both functions (incompatibility and sex-sorting) are robustly maintained in the SSIMS line and that this approach is effective for population suppression in cage experiments. Further we show that SSIMS males remain competitive with wild-type males for reproduction with wild-type females, including at the level of sperm competition.
Recently introduced Wolbachia reduces bacterial species richness and reshapes bacterial community structure in Nilaparvata lugens
20141T.-P. Li, C.-Y. Zhou, J.-T. Gong, Z. Xi and X.-Y. Hong, Pest Management Science, 2022-01-21 13:28:22.
BACKGROUND Wolbachia has been developed as an effective tool to suppress insect pests and arbovirus transmission. Recently, the brown planthopper Nilaparvata lugens, a serious agricultural pest, has been successfully transinfected with Wolbachia strain wStri from Laodelphax striatellus. However, before conducting the field experiments, the impacts of wStri on the bacterial microbiota in N. lugens and how it differs from native Wolbachia wLug strain have not been clarified. RESULTS Here, we found that wStri reduced bacterial diversity and shaped bacterial community structure more than wLug in both developmental stage and different adult tissues. Overall, the relative abundance of Wolbachia was negatively correlated with bacterial diversity, but the bacterial diversity gradually decreased only when the relative abundance of Wolbachia was higher than 60%. Further analysis found that wStri reduced species richness of other bacteria but not their evenness. wStri infection also affected many bacterial functions (e.g., amino acid metabolism & signaling and cellular processes) in the developmental stages, with a stronger effect than wLug in nymphs. Moreover, although Wolbachia occupied a high relative abundance in infected individuals, Acinetobacter was consistently a core part of microbiome. CONCLUSION These results showed the significant impacts of recently introduced wStri on bacterial microbiota in N. lugens, with the effects differing from native wLug. This study will aid in understanding the relationship between Wolbachia, its host and the host's microbiota, and provide a reference for future field experiments. This article is protected by copyright. All rights reserved.
Lab-scale characterization and semi-field trials of Wolbachia Strain wAlbB in a Taiwan Wolbachia introgressed Ae. aegypti strain
20383W. L. Liu, H. Y. Yu, Y. X. Chen, B. Y. Chen, S. N. Leaw, C. H. Lin, M. P. Su, L. S. Tsai, Y. Chen, S. H. Shiao, Z. Y. Xi, A. C. C. Jang and C. H. Chen, PLOS Neglected Tropical Diseases, 16:24. 2022-01-11 08:53:33.
Author summaryPrior to open field release, new genetic approaches that interfere with mosquito abilities and reduce mosquito population density require progressive evaluation both in the laboratory and contained field trials. Trials in contained outdoor systems are thus an important step and allow for evaluation of the effectiveness and reliability of Wolbachia-infected Aedes aegypti (wAlbB-Tw) in settings that incorporate natural environmental variations. We describe a semi-field system designed to study the ability of wAlbB-Tw mosquitoes to suppress local mosquito populations. We provide a protocol for establishing, maintaining, and monitoring Ae. aegypti population densities inside field cages. These results pave the way for the open release of wAlbB-Tw-infected Ae. aegypti mosquitoes in the field. Dengue fever is one of the most severe viral diseases transmitted by Aedes mosquitoes, with traditional approaches of disease control proving insufficient to prevent significant disease burden. Release of Wolbachia-transinfected mosquitoes offers a promising alternative control methodologies; Wolbachia-transinfected female Aedes aegypti demonstrate reduced dengue virus transmission, whilst Wolbachia-transinfected males cause zygotic lethality when crossed with uninfected females, providing a method for suppressing mosquito populations. Although highly promising, the delicate nature of population control strategies and differences between local species populations means that controlled releases of Wolbachia-transinfected mosquitoes cannot be performed without extensive testing on specific local Ae. aegypti populations. In order to investigate the potential for using Wolbachia to suppress local Ae. aegypti populations in Taiwan, we performed lab-based and semi-field fitness trials. We first transinfected the Wolbachia strain wAlbB into a local Ae. aegypti population (wAlbB-Tw) and found no significant changes in lifespan, fecundity and fertility when compared to controls. In the laboratory, we found that as the proportion of released male mosquitoes carrying Wolbachia was increased, population suppression could reach up to 100%. Equivalent experiments in semi-field experiments found suppression rates of up to 70%. The release of different ratios of wAlbB-Tw males in the semi-field system provided an estimate of the optimal size of male releases. Our results indicate that wAlbB-Tw has significant potential for use in vector control strategies aimed at Ae. aegypti population suppression in Taiwan. Open field release trials are now necessary to confirm that wAlbB-Tw mediated suppression is feasible in natural environments.
Intervention of Modern Genetic Tools for Managing Insect Pests of Fruit Crops
25476G. S. Miglani, S. Singh, Z. Li and R. K. Sandhu, Genetic Methods and Tools for Managing Crop Pests, 2022-01-01 09:00:36.
Merits and demerits of select modern genetic tools as sterile insect technique, repressible dominant lethal, engineering insect pests, transgenic crops, primary resistance management, gene silencing RNA interference, genome-editing-based methods, autocidal insect control techniques, and genomics approaches for pest management have been discussed. Application of these methods to manage insect pests of fruit crops have been dealt with. Finally, new vision to pest control and future prospects in the utilization of molecular genetics-based tools for insect pest management has been presented.
Determinants of stakeholders’ attitudes and intentions toward supporting the use of Wolbachia-infected Aedes mosquitoes for dengue control
19744A. F. Arham, L. Amin, M. A. C. Mustapa, Z. Mahadi, M. Yaacob and M. Ibrahim, BMC Public Health, 21:2314. 2021-12-23 13:22:08.
BACKGROUND: A recent approach in controlling dengue is by using the Wolbachia-infected Aedes mosquito (WiAM). The approach has been reported to be more effective than traditional methods, such as fogging. Therefore, it is imperative to assess the factors predicting its acceptance among stakeholders before implementing this technology more widely in Malaysia. METHODS: The survey data were collected from two primary stakeholder groups using a stratified random sampling technique. The two primary stakeholder groups were scientists (n = 202) and the public (n = 197) in the Klang Valley region of Malaysia, a hot spot area known for the high rate of dengue cases. The respondents answered questions on a seven-point Likert scale survey regarding trust in key players, attitudes toward nature versus materialism, religiosity, perceived benefits, perceived risks, attitudes, and intentions. The data were analyzed using Smart Partial Least Square (SmartPLS) software (version 3.2.6) to determine the predictors influencing attitudes and intentions to support the use of WiAM technology. RESULTS: The results indicated a strong positive relationship between attitudes and intentions to support the use of WiAM (β = 0.676, p < 0.001). The most important significant predictor for attitudes was perceived benefits (β = 0.493, p < 0.001), followed by perceived risks (β = - 0.080, p = 0.048). Trust in key players, attitudes toward nature versus material, and religiosity had indirect relationships with attitudes through the perceived benefits and risks. CONCLUSIONS: The identified predictors can serve as indicators for the decision-making process regarding WiAM implementation in Malaysia and other developing countries with similar demographics and cultures.
Perspectives into Genetic Manipulations for Control of Dengue Vector (Aedes aegypti Linnaeus, 1762) with Reference to Progress in Indian Experiments
19975R. Chatterjee, S. Bhattacharya and B. K. Tyagi, Genetically Modified and other Innovative Vector Control Technologies, 2021-12-21 11:46:45.
Vector-borne diseases like malaria, dengue, chikungunya, Japanese encephalitis, Zika and others claim millions of lives across the globe annually, and as such their control has become an ardent necessity. Past attempts over the decades have introduced vector control through chemical, biological and environmental means. However, these measures, already in place, failed to completely bring down the mortality rates from vector-borne diseases, most of which lack a vaccine to prevent epidemics or even a specific antidote to treat patients. The modern development of technologies such as the release of insects carrying a dominant lethal (RIDL) gene system, an example of transgenesis; the Wolbachia-based cytoplasmic incompatibility inducing infertility in female insects, an example of paratransgenesis; and the revolutionary gene drive (CRISPR/Cas9) technology, has their roots in the sterile insect technology (SIT), which worked by creating sterilized males through irradiation to compete with their wild counterparts and subsequently mate with females in nature to produce infertile eggs; a technology meant to gradually and finally exterminate the vector population in nature. These technologies have shown great promise, albeit many imperfections, particularly regarding acceptance by the concerned societies. As far as vector control is concerned, we have attempted to simplify their definitions for the common man so that the intricate scientific jargon about these technologies do not instill any fear or doubts to the end users.
Wolbachia Endosymbiont and Mosquito Vectors, with Emphasis on Lymphatic Filariasis Elimination
19965I. P. Sunish, Genetically Modified and other Innovative Vector Control Technologies, 2021-12-21 11:24:11.
Wolbachia are maternally inherited intracellular bacteria, known to alter early development and mitotic processes in their hosts. They are frequently observed as a reproductive parasite, capable of inducing feminization, parthenogenesis, male killing, or cytoplasmic incompatibility. A total of 18 clades of Wolbachia have been reported, almost exclusively in arthropods. Wolbachia-based strategies have been proposed for the control of disease vectors. Wolbachia-based population suppression and transmission blocking can work in species not commonly infected with Wolbachia in the wild. However, efficient maintenance and spread of Wolbachia infection into field populations is crucial to the success of this strategy. Property of cytoplasmic incompatibility (CI) can be used to reduce the density of mosquito field populations through inundative releases of incompatible males in order to sterilize females. In semi-field condition at La Reunion, the LR[wPip(Is)] males of Culex quinquefasciatus successfully competed with field males in mating with field females. Depletion of Wolbachia endobacteria by antibiotic therapy prevents larval moulting and kills adult filarial worms. This strategy could act as an adjunct to vector control and is being exploited for the elimination of lymphatic filariasis.
Field Trials of Gene Drive Mosquitoes: Lessons from Releases of Genetically Sterile Males and Wolbachia-infected Mosquitoes
19925J. M. Marshall and V. N. Vásquez, Genetically Modified and other Innovative Vector Control Technologies, 2021-12-21 09:27:08.
The discovery of CRISPR-based gene editing and its application to homing-based gene drive has been greeted with excitement, for its potential to control mosquito-borne diseases on a wide scale, and concern, for the invasiveness and potential irreversibility of a release. At the same time, CRISPR-based gene editing has enabled a range of self-limiting gene drive systems to be engineered with much greater ease, including (1) threshold-dependent systems, which tend to spread only when introduced above a certain threshold population frequency, and (2) temporally self-limiting systems, which display transient drive activity before being eliminated by virtue of a fitness cost. As these CRISPR-based gene drive systems are yet to be field-tested, plenty of open questions remain to be addressed, and insights can be gained from precedents set by field trials of other novel genetics-based and biological control systems, such as trials of Wolbachia-transfected mosquitoes, intended for either population replacement or suppression, and trials of genetically sterile male mosquitoes, either using the RIDL system (release of insects carrying a dominant lethal gene) or irradiation. We discuss lessons learned from these field trials and implications for a phased exploration of gene drive technology, including homing-based gene drive, chromosomal translocations, and split gene drive as a system potentially suitable for an intermediate release.
Arthropods of Medical Importance: Need for Genetic and Other Innovative Vector Control Technologies, with Emphasis on Eco-biosocial and Environmental Considerations.
19923B. K. Tyagi, Genetically Modified and other Innovative Vector Control Technologies, 2021-12-21 09:22:08.
Among the world’s known vector groups, viz. arthropods, snails and rodents, the most important vectors originate from arthropods, the jointed legs. Arthropods are doubtlessly regarded as the most dominant creatures on the Earth due largely to their remarkable structural and behavioural diversity, besides humongous species preponderance. Of course, some of these arthropods are serious pests and/or vectors of human and animal diseases—deadly, debilitating and economy destructing. According to an estimate, arthropod species make approximately 80% of the global biological diversity. Born some 350–400 million years ago, they have of course achieved, to the utter envy of all other animal forms, a formidable genetic diversity and robustness so much so that they have virtually captivated pivotal human attention for centuries. They serve as a spectacular model of bioprospecting or laboratory experiments mostly because they are found in abundance, breed prodigiously and are exceptionally easier to culture or cultivate. For the aforesaid reasons, arthropods are also the easy target for genetic manipulations such as the transgenesis (using the release of insect carrying dominant lethal (RIDL) gene system or gene drive-based genome editing, e.g. CRISPR/Cas9, to suppress or replace the vector population) or paratransgenesis (e.g. deploying endosymbiont Wolbachia-induced cytoplasmic incompatibility for replacing natural vector population). In particular, the advent of CRISPR technology has excited the potential to engineer new game-changing technologies and innovative systems that can be used to control wild populations of mosquitoes. Two developments of particular interest are a self-limiting system termed precision-guided sterile insect technique (pgSIT) and a homing-based gene drive (HGD). The unique features of these systems can make them valuable tools to control vector mosquitoes in the future. All these biotechnological advancements in vector control are designed to fit well in the multi-methodical integrated vector management (IVM) strategy.
The Effects of Boric Acid Sugar Bait on Wolbachia Trans-Infected Male Aedes albopictus (ZAP Males®) in Laboratory Conditions
19917V. S. Aryaprema, W. A. Qualls, K. L. Dobson, S. L. Dobson and R.-D. Xue, Insects, 13. 2021-12-21 09:06:57.
The field release of Wolbachia trans-infected male mosquitoes, as well as the use of toxic sugar baits, is a novel and promising candidate technique for integrated mosquito management programs. However, the methods of action of the two techniques may not be complementary, because the Wolbachia method releases mosquitoes into the environment expecting a wild population reduction in subsequent generations while the toxic baits are intended to reduce the wild population by killing mosquitoes. This laboratory study was conducted to evaluate the effectiveness of boric acid toxic sugar baits on Wolbachia trans-infected male Aedes albopictus, relative to wild-type Ae. albopictus males. Wolbachia trans-infected (ZAP male®) and the wild-type Ae. albopictus males were exposed separately to 1% boric acid in a 10% sucrose solution in BugDorms. In the control test, the two groups were exposed to 10% sucrose solution without boric acid. Percent mortalities were counted for 24 h, 48 h and 72 h post exposure periods. The results show that 1% boric acid toxic sugar bait can effectively kill ZAP males under laboratory conditions, and the effectiveness was significantly higher after 24 h and 48 h, compared to wild-type male Ae. albopictus. This finding will help in planning and coordinating integrated mosquito management programs, including both Wolbachia trans-infected mosquito releases and the use of toxic sugar baits against Ae. albopictus.
Genetically Modified and other Innovative Vector Control Technologies
19912B. K. Tyagi, SpringerLink, 2021-12-21 08:48:19.
This book comprehensively covers the latest development in developing and deploying the genetically modified vectors, particularly Anopheles and Aedes mosquitoes responsible for transmitting malaria parasites and dengue viruses, the most deadly and/or debilitating among all the vector-borne diseases. It is considered timely and commensurate to bring about a book dealing with the various ecological, biological and social as well as regulatory aspects for the deployment of genetically modified vectors in special context with the biosafety of humans, his associates, and the environment. Written by an array of specialists and experts in various subjects of genetically modified organisms, this book centrally addresses the (i) basic principles of the genetic manipulation of vectors and they are potential impact on human and the environment, (ii) ecological, biological, ethical, legal and social implications of the use of genetically modified vectors, (iii) identification of potential hazards; assessment and management of risks for human and environment; risk/benefit analysis, (iv) principles and practices for the assessment and management of biosecurity and biosafety in laboratories (and in the field), (v) guiding principles for creation and management of institutional or national biosafety review boards and ethics review committees, and (vi) development and application of a biosafety regulatory framework and its related legal principles at national levels for securing the development and use of vector control methods based on genetic modification strategies.
New molecular genetic techniques: regulatory and societal considerations
19403Nielsen, K. M., AREA-WIDE INTEGRATED PEST MANAGEMENT: Development and Field Application, 2021-11-29 18:07:46.
A rapidly expanding toolbox of techniques available for genome editing provides the basis for a new continuum in types of modifications that can be introduced into a genome and blur the bimodal GMO vs. non-GMO (genetically modified organism) divide. Site-directed nucleases (SDN) are now used to modify existing nucleotides within genomes instead of adding recombined DNA as transgenes. Moreover, new gene drive approaches are in development based on SDNs. A number of potential drive applications have been reported, but uncertainties in trait stability and limitations in knowledge of the affected system at various temporal and spatial levels slow down their current uses. Adoption of new genome targeted technology takes place in a social context. The context will vary between countries and cultures, expressed in values, ethics, politics and priorities - that are translated into different regulatory approaches. Some developed products using new genome editing techniques clearly fall under internationally negotiated regulations of GMOs. However, other product outcomes of editing techniques challenge our current understanding and definition of GMOs. There is an urgent need for further research, for building international consensus and harmonizing regulatory approaches to facilitate categorization, predictability, transparency, trust and trade.
AREA-WIDE INTEGRATED PEST MANAGEMENT: Development and Field Application
19371Hendrichs, J. Pereira, R., Vreysen, M. J. B., AREA-WIDE INTEGRATED PEST MANAGEMENT: Development and Field Application, 2021-11-29 17:04:54.
The concept of area-wide integrated pest management (AW-IPM), in which the total population of a pest in an area is targeted, is central to the effective control of such populations through the integration of genetic, biological and other pest suppression technologies. Insect movement, occurring sometimes over long distances, is generally underestimated. As a consequence, most conventional pest management is implemented as a localized or field-by-field, un-coordinated action against segments of a pest population, not taking in consideration insect movement, resulting very often in an unsustainable spiral of insecticide application and eventual resistance of the pest against the used insecticides. On the other hand, an AW-IPM approach adopts a preventive rather than a reactive strategy, whereby all individuals of the pest population are targeted in time and space and selecting a time when the pest populations are more vulnerable (e.g. during certain times of the year when the population densities are naturally low), requiring in the longer term fewer inputs and resulting in more cost-effective and sustainable pest management. It involves a coordinated effort over often larger areas, including not only agricultural, but also natural and other areas with pest presence. By addressing these sources of reinfestation in the surroundings of the agricultural areas, satisfactory pest control is achieved in the whole area and fewer control actions are required. This new textbook on AW-IPM assembles a series of selected papers that attempts to address various fundamental components of AW-IPM, e.g. the importance of relevant problem-solving research, the need for essential baseline data, the significance of integrating adequate tools for appropriate control strategies, and the value of pilot trials, etc. Of special interest are the numerous papers on pilot and operational programmes that pay special attention to practical problems encountered during the implementation of insect pest control programmes. A significant number of contributions to this book resulted from oral and poster presentations at the Third FAO/IAEA International Conference on “Area-wide Management of Insect Pests: Integrating the Sterile Insect and Related Nuclear and Other Techniques”, which was successfully held from 22-26 May 2017 at the Vienna International Centre, Vienna, Austria. The conference was attended by 360 delegates from 81 countries and six international organization. However, the book contributions were selected beyond the work presented at the conference and a number of experts dealing mainly with action programmes were invited to present their work in this publication
Combined sterile insect technique and incompatible insect technique: concept, study design, experience and lessons learned from a pilot suppression trial in Thailand
19367Kittayapong, P., AREA-WIDE INTEGRATED PEST MANAGEMENT: Development and Field Application, 2021-11-29 16:50:12.
Climate change, rapid global transport and land use change leading to urbanization and agricultural intensification have facilitated disease emergence in vulnerable regions like Southeast Asia, and also the global expansion of vectors and vector-borne diseases into other regions like the Americas and Europe. Important vector-borne diseases, i.e. dengue, chikungunya, yellow fever, and Zika are transmitted by the major mosquito vector species, Aedes aegypti (L.) and Aedes albopictus (Skuse). Management of Ae. aegypti populations in countries endemic to these diseases, especially in Southeast Asia, is not sufficiently effective, resulting in high morbidity and mortality in the region. Insecticide resistance has become an important issue, causing failure in insecticide-based vector control. Innovative or alternative tools/approaches are needed to effectively reduce mosquito vector populations and consequently reduce the diseases they transmit. A trial integrating the environment-friendly Sterile Insect Technique (SIT) and the insect incompatible technique (IIT) was successfully carried out on a small-scale in a semi-rural setting in Thailand. In this chapter, we report on the design and methodology, as well as the experience and lessons learned from the baseline preparation and implementation of the pilot trial.
Barriers and facilitators of area-wide management including sterile insect technique application: The example of Queensland fruit fly
19365Mankad, A., Loechel, B., and Measham, P. F., AREA-WIDE INTEGRATED PEST MANAGEMENT: Development and Field Application, 2021-11-29 16:44:16.
The area-wide management (AWM) of highly mobile insect pests such as tephritid fruit flies requires an integrated understanding of technical, social and institutional processes that drive a coordinated approach within a defined area. Furthermore, the success of an AWM programme is dependent upon the coordinated efforts of key stakeholders within the designated area (e.g. growers, community members). Yet, public views regarding AWM may not reflect those views held by scientists or stakeholders. Public considerations for acceptance are likely varied and multidimensional. A series of qualitative (phases 1-2) and quantitative (phase 3) studies examined stakeholder and community attitudes towards AWM to manage Queensland fruit fly Bactrocera tryoni (Froggatt) (Tephritidae) and the novel use of the Sterile Insect Technique (SIT) as a possible component of AWM. Research was conducted over three regions of varying pest prevalence, ranging from zero to endemic; participants included growers, extension officers, industry and government representatives, and members of the general public. Participants in this research were asked to consider potential barriers and facilitators to the widespread uptake of AWM integrating the SIT, including any relevant institutional-level factors. Combined data revealed potential social barriers to AWM and SIT uptake. Most notably, there were perceptions of low efficacy in successfully coordinating key social groups for the purposes of an AW-IPM approach, and a concern for the possibility of 'free-riders' within an areawide system. On the other hand, innovation complexity and observability of outcomes were important factors contributing to acceptance of AWM. Importantly, all participants were influenced by the attitudes and behaviours of important others. Participants also identified key facilitators that could assist in the uptake of AWM using the SIT. These facilitators include the importance of trustworthy information sources and harnessing the persuasive influence of community champions and central packing houses on commercial growers. Overall, there was high stated acceptance for the SIT, both on-farm and in towns, as long as SIT application was found to be economically feasible at individual farm or household level and the community was adequately consulted.
Ecology, behaviour and area-wide control of the floodwater mosquito Aedes sticticus, with potential of future integration of the sterile insect technique
19361Lundstrom, J. O. Schafer, M. L. Kittayapong, P., AREA-WIDE INTEGRATED PEST MANAGEMENT: Development and Field Application, 2021-11-29 16:33:24.
The strategy of aerial control of the floodwater mosquito Aedes sticticus (Meigen) in the floodplains of River Dalalven, central Sweden, was developed to directly address specific larval breeding areas in temporary flooded wet meadows and swamps. Using the Bti-based larvicide VectoBac G (R), a very strong reduction of larval abundance is achieved, resulting in a massive decrease of blood-seeking females that could otherwise spread from the wetlands to feast on blood from humans and animals within 5 km or more from the larval biotopes. However, there is also a political demand to reduce the usage of the control agent through hypothetical alternatives, such as cattle grazing and mowing of the meadows, as well as hydrological changes of the River Dalalven. An evaluation of these measures showed that they are either insufficient or unrealistic in reducing floodwater mosquito abundance. Thus, we searched for other potential population suppression methods. Using the criteria of efficacy, environmental neutrality and compatibility within an integrated suppression approach, we conclude that Sterile Insect Technique (SIT) and the Incompatibility Insect Technique (IIT) would qualify for a pilot-scale test of their feasibility for the integrated control of the floodwater mosquito Ae. sticticus. The SIT and the IIT are similar strategies involving the release of sterile males which mate with local fertile females and result in infertile eggs. Prerequisites for a sterile male strategy to control Ae. sticticus include: a laboratory colony of the species, a facility for mass-rearing of mosquitoes, the sterilisation of males, a transport strategy, a dispersal system, assay systems for several life stages, and a method capable of reducing the population of this superabundant species before commencing the sterile male release. One factor in favour of implementing the SIT or IIT against Ae. sticticus is that mating occurs in or near well-defined larval breeding areas with specific relation to flood events. Another factor in favour of the SIT or the IIT is the availability of existing methods to measure gender, larvae and egg abundance. Also, existing Bti-treatments can substantially lower the population size before sterile male release. Other prerequisites, like the successful colonization of Ae. sticticus will require more tests and adaptations of existing mosquito rearing protocols. A pilot study is suggested for an isolated study area, protected from reinvasion by Ae. sticticus-females and included in routine Bti-treatments.
Trial suppresses mosquitoes using non-GMO approach
18863GM Watch, GM Watch, 2021-10-07 18:51:46.
In a first for the Southern Hemisphere, researchers have shown that a bacterium can successfully suppress populations of the invasive, disease-carrying Aedes aegypti mosquito that is responsible for spreading dengue, yellow fever and Zika. Published in PNAS (see abstract below), the trial involved releasing three million male Aedes aegypti mosquitoes in Northern Queensland, sterilised with a naturally occurring bacterium called Wolbachia, across three trial sites over a 20-week period during the summer of 2018. The sterile male insects search out and mate with wild females, preventing the production of offspring. Scientists returned the following year and found one of the trial sites, Mourilyan in Queensland, was almost devoid of mosquitoes.
Invasive, disease-carrying Aedes aegypti mosquito sterilized with bacteria and eradicated in large-scale trial
18872CSIRO, Phys Org, 2021-10-05 19:15:01.
In a first for the Southern Hemisphere, researchers have shown a bacteria can successfully sterilize and eradicate the invasive, disease carrying Aedes aegypti mosquito which is responsible for spreading dengue, yellow fever and Zika. The breakthrough could support the suppression and potential eradication of Aedes aegypti worldwide. Published today in PNAS, the landmark trial involved releasing 3 million male Aedes aegypti mosquitoes in Northern Queensland sterilized with bacteria called Wolbachia. The trial was conducted across three sites over a 20-week period during the summer of 2018. The sterile male insects search out and mate with wild females, preventing the production of offspring.
Releasing incompatible males drives strong suppression across populations of wild and Wolbachiat-carrying Aedes aegypti in Australia
18844N. W. Beebe, D. Pagendam, B. J. Trewin, A. Boomer, M. Bradford, A. Ford, C. Liddington, A. Bondarenco, P. J. De Barro, J. Gilchrist, C. Paton, K. M. Staunton, B. Johnson, A. J. Maynard, G. J. Devine, L. E. Hugo, G. Rasic, H. Cook, P. Massaro, N. Snoad, J., Proceedings of the National Academy of Sciences, 118:e2106828118. 2021-10-05 11:33:10.
Through replicated treatment and control experiments in northern Australia, regular releases of Aedes aegypti males infected with a Wolbachia from Aedes albopictus was shown to drive strong population suppression in mosaic populations of wild-type (no Wolbachia) and wMel-Wolbachia–carrying Ae. aegypti. In a demonstration of bidirectional incompatibility between different Wolbachia strains in the field, we also demonstrate that one season’s suppression experiment can also show an ongoing effect into the following season.Releasing sterile or incompatible male insects is a proven method of population management in agricultural systems with the potential to revolutionize mosquito control. Through a collaborative venture with the “Debug” Verily Life Sciences team, we assessed the incompatible insect technique (IIT) with the mosquito vector Aedes aegypti in northern Australia in a replicated treatment control field trial. Backcrossing a US strain of Ae. aegypti carrying Wolbachia wAlbB from Aedes albopictus with a local strain, we generated a wAlbB2-F4 strain incompatible with both the wild-type (no Wolbachia) and wMel-Wolbachia Ae. aegypti now extant in North Queensland. The wAlbB2-F4 strain was manually mass reared with males separated from females using Verily sex-sorting technologies to obtain no detectable female contamination in the field. With community consent, we delivered a total of three million IIT males into three isolated landscapes of over 200 houses each, releasing ∼50 males per house three times a week over 20 wk. Detecting initial overflooding ratios of between 5:1 and 10:1, strong population declines well beyond 80% were detected across all treatment landscapes when compared to controls. Monitoring through the following season to observe the ongoing effect saw one treatment landscape devoid of adult Ae. aegypti early in the season. A second landscape showed reduced adults, and the third recovered fully. These encouraging results in suppressing both wild-type and wMel-Ae. aegypti confirms the utility of bidirectional incompatibility in the field setting, show the IIT to be robust, and indicate that the removal of this arbovirus vector from human-occupied landscapes may be achievable
Wolbachia-mediated sterility suppresses Aedes aegypti populations in the urban tropics
19443Project Wolbachia-Singapore Consortium, medRxiv, 2021-06-17 21:07:26.
Incompatible insect technique (IIT) via releases of male Wolbachiainfected mosquitoes is a promising tool for dengue control. In a three-year trial in Singaporean high-rise housing estates, we demonstrated that Wolbachia-based IIT dramatically reduces both wildtype Aedes aegypti populations [reductions of 92.7% (95% CI: 84.7%–95.8%) and 98.3% (97.7%–99.8%)] and dengue incidence [reductions of 71% (43%-87%) to 88% (57%-99%)] in the targeted areas. The study highlights the need to ensure adequate vertical distribution of released males in high-rise buildings, address immigration of wildtype females from neighboring areas, and prevent and mitigate stable establishment of Wolbachia in field mosquito populations. Our results demonstrate the potential of Wolbachia-based IIT (supplemented with irradiation, in Singapore’s context) for strengthening dengue control in tropical cities, where dengue burden is the greatest.
Modeling and analysis of the implementation of the Wolbachia incompatible and sterile insect technique for mosquito population suppression.
17098B. Zheng, J. S. Yu and J. Li, Siam Journal on Applied Mathematics, 81:718-740. 2021-04-29 13:06:06.
Mathematical analysis may offer guidance in designing effective mass release strategies for the area-wide application of this Wolbachia incompatible and sterile insect technique in the future. The two most crucial concerns in designing release strategies are how often and in what amount should Wolbachia-infected mosquitoes be released in order to guarantee population suppression. Motivated by the experimental data from the Guangzhou mosquito factory and the release strategy implemented on two islands, we formulate and analyze a mosquito population suppression model considering the situation for the release period T less than the sexual lifespan of Wolbachia-infected males. We define release amount thresholds g(1)* and g(2)* with g(1)* < g(2)*. When the release amount c satisfies c >= g(2)*, population suppression is always achievable, as is mathematically manifested by the global asymptotic stability of the origin. However, when c is an element of (0, g(1)*], we find that suppression can be achieved only if the initial wild mosquito population is small enough. This is mathematically proved by the local asymptotic stability of the origin, together with the existence of exactly two T-periodic solutions, one of which is asymptotically stable and the other of which is unstable, with T being the waiting period between two consecutive releases. For c is an element of (g(1)*, g(2)*), we find sufficient conditions on the nonexistence of T-periodic solution, and the existence of at most two T-periodic solutions.
The Insect Pest Control Laboratory of the Joint FAO/IAEA Programme: Ten Years (2010–2020) of Research and Development, Achievements and Challenges in Support of the Sterile Insect Technique
16702M. J. B. Vreysen, A. M. M. Abd-Alla, K. Bourtzis, J. Bouyer, C. Caceres, C. de Beer, D. Oliveira Carvalho, H. Maiga, W. Mamai, K. Nikolouli, H. Yamada and R. Pereira, Insects, 12. 2021-04-13 15:29:17.
The Joint FAO/IAEA Centre (formerly called Division) of Nuclear Techniques in Food and Agriculture was established in 1964 and its accompanying laboratories in 1961. One of its subprograms deals with insect pest control, and has the mandate to develop and implement the sterile insect technique (SIT) for selected key insect pests, with the goal of reducing the use of insecticides, reducing animal and crop losses, protecting the environment, facilitating international trade in agricultural commodities and improving human health.
When More is Less: Mosquito Population Suppression Using Sterile, Incompatible and Genetically Modified Male Mosquitoes
18708S. L. Dobson, Journal of Medical Entomology, 58:1980-1986. 2021-03-11 13:50:08.
The current review of the Sterile Insect Technique (SIT) is motivated by new technologies and the recent renaissance of male release field trials, which is driving an evolution in mosquito control and regulation. Practitioners that are releasing male mosquitoes would do well to learn from past successes and failures, including political and public engagement complications. With examples that include nuanced integrations of the different technologies, e.g., combinations of Wolbachia and irradiation, it is critical that scientists understand and communicate accurately about the technologies, including their evolving management by different regulatory agencies in the USA. Some male release approaches are considered ‘pesticides’ and regulated by federal and state agencies, while other male release approaches are unregulated. It is important to consider how the new technologies fit with the more ‘traditional’ chemical applications of adulticides and larvicides. The economics of male release programs are substantially different from traditional control costs, which can be a challenge to their adoption by abatement districts. However, there is substantial need to overcome these complications and challenges, because the problem with invasive mosquitoes grows ever worse with factors that include insecticide resistance, globalization and climate change.
Number of Project Wolbachia mosquitoes released is constantly reviewed to maintain suppression of dengue: NEA
16388N. L. Ching, today, 2021-02-09 15:12:34.
Project Wolbachia – Singapore has yielded promising results so far.Releases of non-biting male Wolbachia-Aedes mosquitoes have suppressed the urban Aedes aegypti mosquito populations in study sites at Tampines and Yishun by up to 90 per cent, and we have observed 58 to 74 per cent less dengue cases in 2020 in areas where releases have been ongoing for at least a year compared to areas without releases. However, this does not mean that there will be no dengue cases in the study sites, especially in the initial period, because it takes several months for the releases to bring down the dengue mosquito population.While some residents at the release sites have noticed more non-biting mosquitoes around their homes, the released male mosquitoes do not bite, and the overall data shows a clear benefit — fewer dengue cases.
GeneConvene Global Collaborative Webinar Series | Genetic Biocontrol 2021
16249David O'Brochta and Hector Quemada, GeneConvene Global Collaborative, 2021-02-05 21:53:11.
In the mid 20th century various ideas emerged concerning how genetics and genetic principles could be directly applied to age-old problems of managing insects that threaten food security and public health. This series of webinars will explore the current state-of-the-art of what has been termed genetic control, genetic pest management and genetic biocontrol. It will cover the use of sterility, conditional dominant lethality and Wolbachia-induced cytoplasmic incompatibility. Gene drive, another type of genetic biocontrol, will not be covered in this series; it was recently the focus of webinar series dedicated to the topic.
Reply to: Issues with combining incompatible and sterile insect techniques
16265Y. Li, L. A. Baton, D. Zhang, J. Bouyer, A. G. Parker, A. A. Hoffmann, L. C. Ng, C. H. Tan and Z. Xi, Nature, 590:E3-E5. 2021-02-04 16:31:29.
When the aim is elimination of the target population, Uni-CI and Bi-CI do not have appreciably different risks of population replacement. The small-scale field trial8 cited by Moretti and Calvitti in their Comment1 does not provide evidence that Bi-CI protects against population replacement during IIT, as the occurrence of the released Wolbachia strain in the field was not determined and the level of population suppression was insufficient to facilitate surpassing of the invasion threshold.
Issues with combining incompatible and sterile insect techniques
16261R. Moretti and M. Calvitti, Nature, 590:E1-E2. 2021-02-03 16:00:45.
In a recent paper, Zheng at al.1 performed field experiments that tested a strategy of mosquito suppression based on the release of functionally sterile males produced by the combination of reproductive unidirectional cytoplasmic incompatibility (which is induced by the bacterium Wolbachia) and a sterilization treatment caused by X-rays. In our opinion, the authors do not present an exhaustive description of the current status in this field, and their results highlight several practical weaknesses in this strategy.
Project Wolbachia: Residents are killing the ‘helpful’ mosquitoes, which can be a nuisance
16228T. J. Cheng, today, 2021-01-29 16:33:12.
In 2019, Dr Amy Khor, then Senior Minister of State for the Environment and Water Resources, said that there was a 90 per cent suppression rate at study sites in Tampines and Yishun from February to November that year. However, certain public housing estates under the project were still dengue hot zones last year.The idea of the project is to have the male Aedes mosquitoes, which are injected with the Wolbachia bacteria, mate with female Aedes aegypti mosquitoes. The females then go on to lay eggs that do not hatch, effectively suppressing their numbers.
A patent review on strategies for biological control of mosquito vector
15377K. Parihar, M. Telang and A. Ovhal, World Journal of Microbiology and Biotechnology, 36:23. 2020-12-09 20:28:33.
This paper presents a comprehensive technology overview of patent documents disclosing biological agents for mosquito control. The patent analysis revealed that comparable number of patent documents were filed in two technology categories: non-recombinant agents and genetically modified (GM) agents. In the category of non-recombinant agents, toxic peptides from microbes and biological consortia seemed to be the earliest technology noted right from the year 1965 whereas the patent filings for suppression of mosquito population using genetic modification techniques have emerged from the year 2000 onwards. The United States of America is the leading patent filing jurisdiction followed by China and the Great Britain. Academic institutes have filed higher number of patent applications as compared to private companies. University of Florida was found to be the leading patent filing entity and its patents were focused on suppression of vector population using techniques such as release of insects with dominant lethal (RIDL) and RNA interference (RNAi).
Modelling the Wolbachia incompatible insect technique: strategies for effective mosquito population elimination
15281D. E. Pagendam, B. J. Trewin, N. Snoad, S. A. Ritchie, A. A. Hoffmann, K. M. Staunton, C. Paton and N. Beebe, BMC Biology, 18:13. 2020-12-02 16:29:23.
We introduce a simple Markov population process model for studying mosquito populations subjected to a Wolbachia-IIT programme which exhibit an unstable equilibrium threshold. The model is used to study, in silico, scenarios that are likely to yield a successful elimination result. Our results suggest that elimination is best achieved by releasing males at rates that adapt to the ever-decreasing wild population, thus reducing the risk of releasing Wolbachia-infected females while reducing costs.
Microbiome Innovation in Agriculture: Development of Microbial Based Tools for Insect Pest Management
19716M. Qadri, S. Short, K. Gast, J. Hernandez and A. C.-N. Wong, Frontiers in Sustainable Food Systems, 4. 2020-10-06 12:11:19.
This review emphasizes the potential and use of microbes in sustainable insect pest management. We first review the diverse insect traits shaped by insect-microbe associations that span nutrition, immunity, ecological interactions with natural enemy, insecticide resistance, and behavior. This is followed by discussing different microbiome manipulation approaches to alter pest traits, describing some of the opportunities and obstacles for each approach. We then highlight microbiomes as untapped chemical inventories to discover novel biopesticides, including plant-incorporated protectants and semiochemicals. The last topic covered is the use of beneficial microbes to improve mass-reared insects' performance for autocidal programs, including sterile insect technique and incompatible insect technique, in which we identify topics where data are limited or inconclusive, for future research.
How to fight the deadly dengue virus? Make your own mosquitoes
14320J. Emont, Wall Street Journal, 2020-09-07 15:13:25.
When the bacteria-laden male mosquitoes are released into the open and mate with naturally-born females, the resultant eggs won’t hatch.
Engineered Reproductively Isolated Species Drive Reversible Population Replacement
13837A. Buchman, I. Shriner, T. Yang, J. Liu, I. Antoshechkin, J. M. Marshall, M. W. Perry and O. S. Akbari, bioRxiv, 2020.08.09.242982. 2020-08-10 15:42:26.
Engineered reproductive species barriers are useful for impeding gene flow and driving desirable genes into wild populations in a reversible threshold-dependent manner. We engineer multiple reproductively isolated SPECIES and demonstrate their threshold-dependent gene drive capabilities in D. melanogaster.
Genetic Biocontrol – An Overview (video 13.13 min)
11398GeneConvene Global Collaborative, 2020-04-25 12:41:00.
This video explains what genetic biocontrol is and surveys various technologies that can be consider genetic biocontrol technologies. It offers a conceptual organization of the various technologies based on the potential of genetic biocontrol organisms to persist and spread in an environment. This video was produced by the GeneConvene Global Colaborative.
Can we kill the dreaded mosquito? Do we even want to?
11228Stacey McKenna, Sierra, 2020-04-19 15:40:08.
As a major vector for disease, the mosquito has harmed more human beings than just about any other animal, and a changing climate is only boosting those numbers. As the range of disease-carrying species of mosquitoes expands, so does their ability to transmit the parasites and viruses that result in malaria, chikungunya, Zika, yellow fever, West Nile, and dengue fever. In 2018, the continental United States saw a 25 percent increase in severe, neuroinvasive cases of West Nile virus compared with a decade earlier. And over the past three decades, the CDC reports, the worldwide incidence of dengue fever has risen 30-fold.
Efficient production of male Wolbachia-infected Aedes aegypti mosquitoes enables large-scale suppression of wild populations
22639J. E. Crawford, D. W. Clarke, V. Criswell, M. Desnoyer, D. Cornel, B. Deegan, K. Gong, K. C. Hopkins, P. Howell, et al., Nature Biotechnology, 38:482-492. 2020-04-06 06:19:43.
The range of the mosquito Aedes aegypti continues to expand, putting more than two billion people at risk of arboviral infection. The sterile insect technique (SIT) has been used to successfully combat agricultural pests at large scale, but not mosquitoes, mainly because of challenges with consistent production and distribution of high-quality male mosquitoes. We describe automated processes to rear and release millions of competitive, sterile male Wolbachia-infected mosquitoes, and use of these males in a large-scale suppression trial in Fresno County, California. In 2018, we released 14.4 million males across three replicate neighborhoods encompassing 293 hectares. At peak mosquito season, the number of female mosquitoes was 95.5% lower (95% CI, 93.6–96.9) in release areas compared to non-release areas, with the most geographically isolated neighborhood reaching a 99% reduction. This work demonstrates the high efficacy of mosquito SIT in an area ninefold larger than in previous similar trials, supporting the potential of this approach in public health and nuisance-mosquito eradication programs.
The value of existing regulatory frameworks for the environmental risk assessment of agricultural pest control using gene drive
8194J. Romeis, J. Collatz, D. C. M. Glandorf and M. B. Bonsall, Environmental Science & Policy, 108:19-36. 2020-03-27 20:20:04.
The application of (synthetic) gene drives is a powerful tool to control populations of insects that are agricultural pests, vectors of diseases, or a threat to biodiversity potentially leading to the local or global eradication of a species. The potential use of gene drive organisms has triggered a heated discussion regarding their environmental impacts and regulatory oversight. However, experience exists in assessing the environmental impacts of a number of established agricultural pest control methods that require the release of living organisms, that provide high levels of area-wide control and that might be irreversible. This includes classical biological control, the sterile insect technique, the incompatible insect technique that is based on the cytoplasmic incompatibility caused by Wolbachia endosymbionts, and genetically modified insects containing self-limiting traits. The different technologies are described, the regulatory practice and experience is summarized and pathways through which these control technologies could harm valued ecosystem services are presented. With a focus on the application of gene drives in agriculture, using the invasive Drosophila suzukii (Diptera: Drosophilidae) as a case study we then discuss to what extent the existing frameworks could assist the risk assessment of insects carrying gene drives. We suggest that drawing on existing practices, experiences and legislative frameworks will provide a pragmatic and proportionate approach to evaluate the environmental risks of novel solutions based on gene drive technologies.
Wolbachia transinfections in Culex quinquefasciatus generate cytoplasmic incompatibility
6224T. H. Ant, C. Herd, F. Louis, A. B. Failloux and S. P. Sinkins, Insect Molecular Biology, 29:1-8. 2020-01-06 21:43:12.
Culex quinquefasciatus is an important mosquito vector of a number of viral and protozoan pathogens of humans and animals, and naturally carries the endosymbiont Wolbachia pipientis, strain wPip. Wolbachia are used in two distinct vector control strategies: firstly, population suppression caused by mating incompatibilities between mass-released transinfected males and wild females; and secondly, the spread of pathogen transmission-blocking strains through populations. Using embryonic microinjection, two novel Wolbachia transinfections were generated in C. quinquefasciatus using strains native to the mosquito Aedes albopictus: a wAlbB single infection, and a wPip plus wAlbA superinfection. The wAlbB infection showed full bidirectional cytoplasmic incompatibility (CI) with wild-type C. quinquefasciatus in reciprocal crosses. The wPipwAlbA superinfection showed complete unidirectional CI, and therefore population invasion potential. Whereas the wAlbB strain showed comparatively low overall densities, similar to the native wPip, the wPipwAlbA superinfection reached over 400-fold higher densities in the salivary glands compared to the native wPip, suggesting it may be a candidate for pathogen transmission blocking.
Incompatible and sterile insect techniques combined eliminate mosquitoes
16263X. Zheng, D. Zhang, Y. Li, C. Yang, Y. Wu, X. Liang, Y. Liang, X. Pan, L. Hu, Q. Sun, X. Wang, Y. Wei, J. Zhu, W. Qian, Z. Yan, A. G. Parker, J. R. L. Gilles, K. Bourtzis, J. Bouyer, M. Tang, B. Zheng, J. Yu, J. Liu, J. Zhuang, Z. Hu, M. Zhang, J.-T. Gon, 572, 56-61. 2019-07-17 16:15:33.
Here we show that combining incompatible and sterile insect techniques (IIT–SIT) enables near elimination of field populations of the world’s most invasive mosquito species, Aedes albopictus. Millions of factory-reared adult males with an artificial triple-Wolbachia infection were released, with prior pupal irradiation of the released mosquitoes to prevent unintentionally released triply infected females from successfully reproducing in the field. This successful field trial demonstrates the feasibility of area-wide application of combined IIT–SIT for mosquito vector control.
SCIENTIFIC OPINION: In response to the referral of 12 October 2015 concerning use of genetically modified mosquitoes for vector control
16065High Council for Biotechnology, High Council for Biotechnology (France), 2017-05-31 13:46:03.
The Scientific Committee’s opinion describes emerging vector control techniques using GM mosquitoes, the current state of research into and development of these techniques and the outcomes of initial experiments worldwide. To date, only one technique has been developed to an operational level: Oxitec’s RIDL technique, which sets out to reduce a mosquito population by repeated mass releases of sterilising transgenic males. Two other techniques at an earlier stage of research and development are based on gene drive, seeking to spread a genetic trait in a wild population, either to make the mosquitoes incapable of transmitting pathogens (gene drive for population modification) or to eliminate the population by spreading sterility (gene drive for population elimination).
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