Scholarly Literature

This is a database of scholarly literature that concentrates currently on natural and engineered selfish genetic elements (gene drives).  The latest are shown here.
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Comparing the long-term persistence of different Wolbachia strains after the release of bacteria-carrying mosquitoes

29563
Jose L. Orozco-Gonzales, Antone dos Santos Benedito, Daiver Cardona-Salgado et al.,  Mathematical Biosciences,  372. 2024-04-25 17:59:21.
This paper proposes a bidimensional modeling framework for Wolbachia invasion, assuming imperfect maternal transmission, incomplete cytoplasmic incompatibility, and direct infection loss due to thermal stress. Our model adapts to various Wolbachia strains and retains all properties of higher-dimensional models. The conditions for the durable coexistence of Wolbachia-carrying and wild mosquitoes are expressed using the model’s parameters in a compact closed form. When the Wolbachia bacterium is locally established, the size of the remanent wild population can be assessed by a direct formula derived from the model. The model was tested for four Wolbachia strains undergoing laboratory and field trials to control mosquito-borne diseases: wMel, wMelPop, wAlbB, and wAu. As all these bacterial strains affect the individual fitness of mosquito hosts differently and exhibit different levels of resistance to temperature variations, the model helped to conclude that: (1) the wMel strain spreads faster in wild mosquito populations; (2) the wMelPop exhibits lower resilience but also guarantees the smallest size of the remanent wild population; (3) the wAlbB strain performs better at higher ambient temperatures than others; (4) the wAu strain is not sustainable and cannot persist in the wild mosquito population despite its resistance to high temperatures.

A naturally isolated symbiotic bacterium suppresses flavivirus transmission by Aedes mosquitoes

29561
Liming Zhang et al.,  Science,  384. 2024-04-25 17:51:54.
Flavivirus diseases are increasing in incidence and prevalence owing to the urban proclivities of its Aedes mosquito vector species. Extirpation of mosquitoes is considered key for the control of several human diseases but often involves toxic chemicals that prompt mosquito resistance. As some biocontrol alternatives look promising in malaria campaigns, Zhang et al. examined the microbiota of Aedes mosquitoes for potential agents to control dengue and Zika virus transmission. The authors isolated a bacterium called Rosenbergiella_YN46 in Aedes albopictus mosquitos. The bacterium was fed to caged mosquitoes to establish stable gut infections, and it was found to prevent the insects from being infected by viruses and blocked viral transmission to mice.

Economic optimization of Wolbachia-infected Aedes aegypti release to prevent dengue

29104
Hollingsworth BD, Cho C, Vella M, Roh H, Sass J, Lloyd AL, Brown ZS.,  Pest Management Science,  2024-04-16 09:30:09.
Dengue virus, primarily transmitted by the Aedes aegypti mosquito, is a major public health concern affecting ≈3.83 billion people worldwide. Recent releases of Wolbachia-transinfected Ae. aegypti in several cities worldwide have shown that it can reduce dengue transmission. However, these releases are costly, and, to date, no framework has been proposed for determining economically optimal release strategies that account for both costs associated with disease risk and releases. We present a flexible stochastic dynamic programming framework for determining optimal release schedules for Wolbachia-transinfected mosquitoes that balances the cost of dengue infection with the costs of rearing and releasing transinfected mosquitoes. Using an ordinary differential equation model of Wolbachia and dengue in a hypothetical city loosely describing areas at risk of new dengue epidemics, we determined that an all-or-nothing release strategy that quickly brings Wolbachia to fixation is often the optimal solution. Based on this, we examined the optimal facility size, finding that it was inelastic with respect to the mosquito population size, with a 100% increase in population size resulting in a 50-67% increase in optimal facility size. Furthermore, we found that these results are robust to mosquito life-history parameters and are mostly determined by the mosquito population size and the fitness costs associated with Wolbachia. These results reinforce that Wolbachia-transinfected mosquitoes can reduce the cost of dengue epidemics. Furthermore, they emphasize the importance of determining the size of the target population and fitness costs associated with Wolbachia before releases occur.

Altering traits and fates of wild populations with Mendelian DNA sequence modifying Allele Sails

29102
Michelle L. Johnson, Bruce A. Hay, Maciej Maselko,  Nature Communications,  15. 2024-04-16 09:23:41.
Population-scale genome editing can be used to alter the composition or fate of wild populations. One approach to achieving these aims utilizes a synthetic gene drive element—a multi-gene cassette—to bring about an increase in the frequency of an existing allele. However, the use of gene drives is complicated by the multiple scientific, regulatory, and social issues associated with transgene persistence and gene flow. Alternatives in which transgenes are not driven could potentially avoid some of these issues. Here we propose an approach to population scale gene editing using a system we refer to as an Allele Sail. An Allele Sail consists of a genome editor (the Wind) that introduces DNA sequence edits (the Sail) at one or more sites, resulting in progeny that are viable and fertile. The editor, such as a sequence-specific nuclease, or a prime- or base-editor, is inherited in a Mendelian fashion. Meanwhile, the edits it creates experience an arithmetic, Super-Mendelian increase in frequency. We explore this system using agent-based modeling, and identify contexts in which a single, low frequency release of an editor brings edits to a very high frequency. We also identify conditions in which manipulation of sex determination can be used to bring about population suppression. Current regulatory frameworks often distinguish between transgenics as genetically modified organisms (GMOs), and their edited non-transgenic progeny as non-GMO. In this context an Allele Sail provides a path to alter traits and fates of wild populations in ways that may be considered more acceptable.

Genetic and geographic population structure in the malaria vector, Anopheles farauti, provides a candidate system for pioneering confinable gene-drive releases

29098
Ambrose, L., Allen, S.L., Iro’ofa, C. et al.,  Heredity,  2024-04-16 09:13:44.
Indoor insecticide applications are the primary tool for reducing malaria transmission in the Solomon Archipelago, a region where Anopheles farauti is the only common malaria vector. Due to the evolution of behavioural resistance in some An. farauti populations, these applications have become less effective. New malaria control interventions are therefore needed in this region, and gene-drives provide a promising new technology. In considering developing a population-specific (local) gene-drive in An. farauti, we detail the species’ population genetic structure using microsatellites and whole mitogenomes, finding many spatially confined populations both within and between landmasses. This strong population structure suggests that An. farauti would be a useful system for developing a population-specific, confinable gene-drive for field release, where private alleles can be used as Cas9 targets. Previous work on Anopheles gambiae has used the Cardinal gene for the development of a global population replacement gene-drive. We therefore also analyse the Cardinal gene to assess whether it may be a suitable target to engineer a gene-drive for the modification of local An. farauti populations. Despite the extensive population structure observed in An. farauti for microsatellites, only one remote island population from Vanuatu contained fixed and private alleles at the Cardinal locus. Nonetheless, this study provides an initial framework for further population genomic investigations to discover high-frequency private allele targets in localized An. farauti populations. This would enable the development of gene-drive strains for modifying localised populations with minimal chance of escape and may provide a low-risk route to field trial evaluations.

The Perpetual Vector Mosquito Threat and Its Eco-Friendly Nemeses

29088
Miranda, L.S.; Rudd, S.R.; Mena, O.; Hudspeth, P.E.; Barboza-Corona, J.E.; Park, H.-W.; Bideshi, D.K.,  Biology,  13:182. 2024-04-04 09:42:02.
Aedes, Culex, and Anopheles mosquitoes are the most prolific arthropod vectors of viral and parasitic agents of debilitating and lethal diseases in humans and animals. Despite some success in integrated pest management programs to control vectors, mosquito-borne diseases, such as dengue and dengue hemorrhagic fever, yellow fever, chikungunya, West Nile, and Zika, and parasitic diseases, such as malaria, lymphatic filariasis, and river blindness, continue to threaten the health and well-being of half the world’s population, many of whom live in economically and medically challenged societies. The perpetual problem inflicted by vector-borne diseases is compounded by the selection for resistance to synthetic pesticides, globalization, and climate change. The latter appears to be the most significant factor implicated in the geographic expansion of mosquitoes. Here, we present a review of these challenges and highlight traditional vector control strategies that employ synthetic pesticides, and “green” eco-friendly technologies that include SIT, IIT, RIDL, CRISPR/Cas9/Cas13 gene drive systems, and biological control, with an emphasis on Lysinibacillus sphaericus and Bacillus thuringiensis subsp. israelensis (Bti).

Wolbachia Infection through Hybridization to Enhance an Incompatible Insect Technique-Based Suppression of Aedes albopictus in Eastern Spain

29086
Cholvi M, Trelis M, Bueno-Marí R, Khoubbane M, Gil R, Marcilla A, Moretti R.,  Insects,  15. 2024-04-04 09:29:30.
Wolbachia bacteria occur naturally as symbionts of many insect species and are responsible for various phenomena that modify the hosts’ reproductive biology. Among them, cytoplasmic incompatibility (CI) refers to the sterility of eggs produced by crosses between infected males and females that are uninfected or infected by a non-compatible strain of these bacteria. CI can be exploited for vector control by establishing an opportune Wolbachia infection in a laboratory population of a target insect species and then releasing the infected males into the environment as sterilizing agents. In the present work, a suitable Wolbachia strain was introduced into a Spanish population of the Asian tiger mosquito, Aedes albopictus, through hybridization with the laboratory line, ARwP, already tested as an efficient control tool against this vector. The obtained hybrids were compared with the ARwP to ascertain the effects derived from transferring the infection to a different Ae. albopictus population. No significant differences between lines were found regarding survival, female fecundity, and egg fertility. Importantly, the eggs produced by crosses between males of the hybrid lines and unmodified wild females were 99.9% sterile. This result encourages further studies to explore the feasibility of a Wolbachia-based control program against the Asian tiger mosquito in Spain.

Detection and quantification of natural Wolbachia in Aedes aegypti in Metropolitan Manila, Philippines using locally designed primers

29084
Reyes JIL, Suzuki T, Suzuki Y, Watanabe K.,  Frontiers in Cellular and Infection Microbiology,  2024-04-04 09:23:33.
The Philippines bears health and economic burden caused by high dengue cases annually. Presently, the Philippines still lack an effective and sustainable vector management. The use of Wolbachia, a maternally transmitted bacterium, that mitigate arbovirus transmission has been recommended. Cytoplasmic incompatibility and viral blocking, two characteristics that make Wolbachia suitable for vector control, depend on infection prevalence and density. There are no current Wolbachia release programs in the Philippines, and studies regarding the safety of this intervention. Here, we screened for Wolbachia in Aedes aegypti collected from Metropolitan Manila, Philippines. We designed location-specific primers for qPCR to test whether this improved Wolbachia detection in Ae. aegypti. We explored if host sex and Wolbachia strain could be potential factors affecting Wolbachia density.

Talking About Gene Drive in Uganda: The Need for Science Communication to Underpin Engagement

29082
Hartley, S., Stelmach, A., Opesen, C., Openjuru, G. L., and Neema, S.,  Science Communication,  2024-04-04 09:15:22.
Uganda may host the world’s first field trials of gene drive mosquitoes for malaria control. Global North discourses pre-suppose African publics have access to information about gene drive and are ready to make decisions about its governance. We explore assumptions about the availability of this information in Uganda. We find a paucity of information available combined with a strong desire for information from lay publics. We discuss these findings in the context of Ugandan information infrastructures and political sensitivities to genetic technologies. If Ugandans are to decide about gene drive, they need independent information about the science to underpin engagement.

Monitoring Aedes populations for arboviruses, Wolbachia, insecticide resistance and its mechanisms in various agroecosystems in Benin

29064
S. Ateutchia-Ngouanet, F. Nanfack-Minkeu, K. Mavridis, S. Wanji, M. Demanou, J. Vontas, R. Djouaka,  Acta Tropica,  253. 2024-04-02 11:34:55.
The susceptibility of arbovirus vectors to insecticides and the microbiome of Aedes species are understudied in Benin.

Between the lab and the Wild: Establishing the Potential of Gene Drive Mosquitoes for Malaria Control

29055
Mäkelin, M.,  Science as Culture,  2024-04-02 09:42:13.
Malaria control has been one of the defining goals in global health.

Wolbachia strain wAlbB shows favourable characteristics for dengue control use in Aedes aegypti from Burkina Faso

29041
Maria Vittoria Mancini, Shivan M. Murdochy, Etienne Bilgo, Thomas H. Ant, Daniel Gingell, Edounou Jacques Gnambani, Anna-Bella Failloux, Abdoulaye Diabate, Steven P. Sinkins,  Environmental Microbiology,  26. 2024-03-19 16:46:34.
Dengue represents an increasing public health burden worldwide.

Alpha-mannosidase-2 modulates arbovirus infection in a pathogen- and Wolbachia-specific manner in Aedes aegypti mosquitoes

29035
Nadya Urakova, Renuka E. Joseph, Allyn Huntsinger, Vanessa M. Macias, Matthew J. Jones, Leah T. Sigle, Ming Li, Omar S. Akbari, Zhiyong Xi, Konstantinos Lymperopoulos, Richard T. Sayre, Elizabeth A. McGraw, Jason L. Rasgon,  Insect Molecular Biology,  2024-03-19 15:50:02.
Multiple Wolbachia strains can block pathogen infection, replication and/or transmission in Aedes aegypti mosquitoes under both laboratory and field conditions.

Prophage proteins alter long noncoding RNA and DNA of developing sperm to induce a paternal-effect lethality

29033
Rupinder Kaur et al.,  Science,  383:1111-1117. 2024-03-19 15:33:59.
Many arthropods carry symbiotic bacteria. Some, including Wolbachia strains, have the capacity to cause male sterility.

Comparative analysis of Wolbachia maternal transmission and localization in host ovaries

29029
Michael T.J. Hague, Timothy B. Wheeler, Brandon S. Cooper,  bioRxiv,  2024-03-19 13:26:24.

Scientism, trust, value alignment, views of nature, and U.S. public opinion about gene drive mosquitos

31447
Evans, J. H., & Schairer, C. E.,  Public Understanding of Science,  2024-03-12 21:29:22.
Gene drive could be a powerful tool for addressing problems of conservation, agriculture, and human health caused by insect and animal pests but is likely to be controversial as it involves the release of genetically modified organisms. This study examined the social determinants of opinion of gene drive. We asked a representative sample of the U.S. public to respond to a description of a hypothetical application of a gene-drive mosquito to the problem of malaria and examined the relationship of these responses with demographic and ideological beliefs. We found strong general approval for the use of gene-drive mosquitos to address malaria, coinciding with the concern about a possible environmental impact of modified mosquitos and that gene drives represent “too much power over nature.” Among the determinants we measured, respondent acceptance of scientism and trust that scientists are advancing the public’s interest were the greatest predictors of views of gene drive.

Acceptability of emergent Aedes aegypti vector control methods in Ponce, Puerto Rico: A qualitative assessment

29010
Pérez-Guerra CL, Rosado-Santiago C, Ramos SA, Marrero-Santos KM, González-Zeno G, Partridge SK, et al.,  PLoS Global Public Health,  2024-03-11 13:41:04.
Aedes aegypti control has been fraught with challenges in Puerto Rico. The government has implemented commonly used vector control methods, but arboviral epidemics still occur. It is necessary to explore new Ae. aegypti control methods. This study aimed to understand the perceptions of community members in Ponce, Puerto Rico about emergent and traditional Ae. aegypti vector control methods and determine their acceptability and support for these methods. We identified the type of information needed to increase support for emergent vector control methods, and the preferred strategies to disseminate this information. Four group discussions were conducted with a total of 32 participants representing eight of the 14 clusters participating in the Communities Organized for the Prevention of Arboviruses (COPA), a project designed to mobilize communities in Ponce, Puerto Rico to prevent diseases transmitted by mosquitoes. Group discussions began with an overview of different methods used for controlling Ae. aegypti mosquitoes. These overviews facilitated participant understanding of the mosquito control methods presented. Use of source reduction, autocidal gravid ovitraps (AGO), and manual application of larvicide for arboviral mosquito control received support from almost all participants. Vector control methods that use more familiar techniques in Puerto Rico such as truck-mounted larvicide spraying (TMLS) and insecticide residual spraying received support from most participants. More than half of participants supported the use of emergent mosquito control methods including Wolbachia suppression, Wolbachia replacement, or genetically modified mosquitoes (GMM). Participants preferred to receive vector control information through house-to-house visits with the distribution of written materials, followed by dissemination of information through traditional (i.e., radio, television) and social media. The detailed information resulting from this study was used to develop messages for a communications campaign to garner future community support. Community acceptance and support are critical for the success of vector control programs using emergent mosquito control methods.

Efficacy of Wolbachia-based mosquito control: Predictions of a spatially discrete mathematical model

29008
David Dye, John W. Cain,  PLoS One,  19. 2024-03-11 12:43:55.
Wolbachia is an endosymbiont bacterium present in many insect species. When Wolbachia-carrying male Aedes aegypti mosquitoes mate with non-carrier females, their embryos are not viable due to cytoplasmic incompatibility. This phenomenon has been exploited successfully for the purpose of controlling mosquito populations and the spread of mosquito-borne illnesses: Wolbachia carriers are bred and released into the environment. Because Wolbachia is not harmful to humans, this method of mosquito control is regarded as a safer alternative to pesticide spraying. In this article, we introduce a mathematical framework for exploring (i) whether a one-time release of Wolbachia carriers can elicit a sustained presence of carriers near the release site, and (ii) the extent to which spatial propagation of carriers may allow them to establish fixation in other territories. While some prior studies have formulated mosquito dispersal models using advection-reaction-diffusion PDEs, the predictive power of such models requires careful ecological mapping: advection and diffusion coefficients exhibit significant spatial dependence due to heterogeneity of resources and topography. Here, we adopt a courser-grained view, regarding the environment as a network of discrete, diffusively-coupled “habitats”—distinct zones of high mosquito density such as stagnant ponds. We extend two previously published single-habitat mosquito models to multiple habitats, and calculate rates of migration between pairs of habitats using dispersal kernels. Our primary results are quantitative estimates regarding how the success of carrier fixation in one or more habitats is determined by: the number of carriers released, sizes of habitats, distances between habitats, and the rate of migration between habitats. Besides yielding sensible and potentially useful predictions regarding the success of Wolbachia-based control, our framework applies to other approaches (e.g., gene drives) and contexts beyond the realm of insect pest control.

Aedes aegypti Controls Ae. aegypti: SIT and IIT—An Overview

29003
Robert L. Aldridge; Seth Gibson; Kenneth J. Linthicum,  Journal of the American Mosquito Control Association,  20:32-49. 2024-03-11 12:34:19.
The sterile insect technique (SIT) and the incompatible insect technique (IIT) are emerging and potentially revolutionary tools for controlling Aedes aegypti (L.), a prominent worldwide mosquito vector threat to humans that is notoriously difficult to reduce or eliminate in intervention areas using traditional integrated vector management (IVM) approaches. Here we provide an overview of the discovery, development, and application of SIT and IIT to Ae. aegypti control, and innovations and advances in technology, including transgenics, that could elevate these techniques to a worldwide sustainable solution to Ae. aegypti when combined with other IVM practices.

DENV-1 Titer Impacts Viral Blocking in wMel Aedes aegypti with Brazilian Genetic Background

28991
Corrêa-Antônio, Jessica, Mariana R. David, Dinair Couto-Lima, Gabriela Azambuja Garcia, Milan S. G. Keirsebelik, Rafael Maciel-de-Freitas, and Márcio Galvão Pavan.,  Viruses,  16. 2024-03-11 10:08:24.
Several countries have been using Wolbachia deployments to replace highly competent native Aedes aegypti populations with Wolbachia-carrying mosquitoes with lower susceptibility to arboviruses such as dengue, Zika, and chikungunya. In Rio de Janeiro, Wolbachia deployments started in 2015 and still present a moderate introgression with a modest reduction in dengue cases in humans (38%). Here, we evaluated the vector competence of wild-type and wMel-infected Ae. aegypti with a Brazilian genetic background to investigate whether virus leakage could contribute to the observed outcomes in Brazil. We collected the specimens in three areas of Rio de Janeiro with distinct frequencies of mosquitoes with wMel strain and two areas with wild Ae. aegypti. The mosquitoes were orally exposed to two titers of DENV-1 and the saliva of DENV-1-infected Ae. aegypti was microinjected into wMel-free mosquitoes to check their infectivity. When infected with the high DENV-1 titer, the presence of wMel did not avoid viral infection in mosquitoes’ bodies and saliva but DENV-1-infected wMel mosquitoes produced lower viral loads than wMel-free mosquitoes. On the other hand, wMel mosquitoes infected with the low DENV-1 titer were less susceptible to virus infection than wMel-free mosquitoes, although once infected, wMel and wMel-free mosquitoes exhibited similar viral loads in the body and the saliva. Our results showed viral leakage in 60% of the saliva of wMel mosquitoes with Brazilian background; thus, sustained surveillance is imperative to monitor the presence of other circulating DENV-1 strains capable of overcoming the Wolbachia blocking phenotype, enabling timely implementation of action plans.

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