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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Integrated control of Aedes albopictus in Southwest Germany supported by the Sterile Insect Technique
20046N. Becker, S. M. Langentepe-Kong, A. T. Rodriguez, T. T. Oo, D. Reichle, R. Luhken, J. Schmidt-Chanasit, P. Luthy, A. Puggioli and R. Bellini, Parasites and Vectors, 15:19. 2022-01-05 10:11:20.
Background: The invasive species Aedes albopictus, commonly known as the Asian tiger mosquito, has undergone extreme range expansion by means of steady introductions as blind passengers in vehicles traveling from the Mediterranean to south-west Germany. The more than 25 established populations in the State of Baden-Wurttemberg, Palatine and Hesse (south-west Germany) have become a major nuisance and public health threat. Aedes albopictus deserves special attention as a vector of arboviruses, including dengue, chikungunya and Zika viruses. In Germany, Ae. albopictus control programs are implemented by local communities under the auspices of health departments and regulatory offices. Methods: The control strategy comprised three pillars: (i) community participation (CP) based on the elimination of breeding sites or improved environmental sanitation, using fizzy tablets based on Bacillus thuringiensis israelensis (fizzy Bti tablets; Culinex (R) Tab plus); (ii) door-to-door (DtD) control by trained staff through the application of high doses of a water-dispersible Bti granular formulation (Vectobac (R) WG) aimed at achieving a long-lasting killing effect; and (iii) implementation of the sterile insect technique (SIT) to eliminate remaining Ae. albopictus populations. Prior to initiating large-scale city-wide treatments on a routine basis, the efficacy of the three elements was evaluated in laboratory and semi-field trials. Special emphasis was given to the mass release of sterile Ae. albopictus males. Results: More than 60% of the local residents actively participated in the first pillar (CP) of the large-scale control program. The most effective element of the program was found to be the DtD intervention, including the application of Vectobac (R) WG (3000 ITU/mg) to potential breeding sites (10 g per rainwater container, maximum of 200 I = maximum of approx. 150,000 ITU/I, and 2.5 g per container <50 I) with a persistence of at least 3 weeks. In Ludwigshafen, larval source management resulted in a Container Index for Ae. albopictus of < 1% in 2020 compared to 10.9% in 2019. The mean number of Aedes eggs per ovitrap per 2 weeks was 4.4 in Ludwigshafen, 18.2 in Metzgergrun (Freiburg) (SIT area) and 22.4 in the control area in Gartenstadt (Freiburg). The strong reduction of the Ae. albopictus population by Bti application was followed by weekly releases of 1013 (Ludwigshafen) and 2320 (Freiburg) sterile Ae. albopictus males per hectare from May until October, resulting in a high percentage of sterile eggs. In the trial areas of Ludwigshafen and Frieburg, egg sterility reached 84.7 +/- 12.5% and 62.7 +/- 25.8%, respectively; in comparison, the natural sterility in the control area was 14.6 +/- 7.3%. The field results were in line with data obtained in cage tests under laboratory conditions where sterility rates were 87.5 +/- 9.2% after wild females mated with sterile males; in comparison, the sterility of eggs laid by females mated with unirradiated males was only 3.3 +/- 2.8%. The overall egg sterility of about 84% in Ludwigshafen indicates that our goal to almost eradicate the Ae. albopictus population could be achieved. The time for inspection and treatment of a single property ranged from 19 to 26 min depending on the experience of the team and costs 6-8 euros per property. Conclusions: It is shown that an integrated control program based on a strict monitoring scheme can be most effective when it comprises three components, namely CP, DtD intervention that includes long-lasting Bti-larviciding to strongly reduce Ae. albopictus populations and SIT to reduce the remaining Ae. albopictus population to a minimum or even to eradicate it. The combined use of Bti and SIT is the most effective and selective tool against Ae. albopictus, one of the most dangerous mosquito vector species.
Stakeholder engagement to inform the risk assessment and governance of gene drive technology to manage spotted-wing drosophila
20212A. E. Kokotovich, S. K. Barnhill-Dilling, J. E. Elsensohn, R. Li, J. A. Delborne and H. Burrack, Journal of Environmental Management, 307:114480. 2022-01-04 15:32:08.
Emerging biotechnologies, such as gene drive technology, are increasingly being proposed to manage a variety of pests and invasive species. As one method of genetic biocontrol, gene drive technology is currently being developed to manage the invasive agricultural pest spotted-wing drosophila (Drosophila suzukii, SWD). While there have been calls for stakeholder engagement on gene drive technology, there has been a lack of empirical work, especially concerning stakeholder engagement to inform risk assessment. To help address this gap and inform future risk assessments and governance decisions for SWD gene drive technology, we conducted a survey of 184 SWD stakeholders to explore how they define and prioritize potential benefits and potential adverse effects from proposed SWD gene drive technology. We found that stakeholders considered the most important potential benefits of SWD gene drive technology to be: 1) Decrease in the quantity or toxicity of pesticides used, and 2) Decrease in SWD populations. Stakeholders were most concerned about the potential adverse effects of: 1) Decrease in beneficial insects, 2) Increase in non-SWD secondary pest infestations, and 3) Decrease in grower profits. Notably, we found that even stakeholders who expressed support for the use of SWD gene drive technology expressed concerns about potential adverse effects from the technology, emphasizing the need to move past simplistic, dichotomous views of what it means to support or oppose a technology. These findings suggest that instead of focusing on the binary question of whether stakeholders support or oppose SWD gene drive technology, it is more important to identify and assess the factors that are consequential to stakeholder decision making – including, for example, exploring whether and under what conditions key potential adverse effects and potential benefits would result from the use of SWD gene drive technology.
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.
Newer Genetic Tools, Techniques, Vectors, Promoters, and Molecular Markers for Genetic Engineering of Herbivorous Insects
25474D. D. Rani, S. Subhash, H. R. Gopalkrishna and A. K. Chakravarthy, Genetic Methods and Tools for Managing Crop Pests, 2022-01-01 08:54:42.
Insects can transmit major infectious diseases to crop plants. Recent advances in insect genomics and transformation technology provide new strategies for the control of insect-borne pathogen transmission and insect pest management. One such strategy is the genetic modification of insects with genes that block pathogen development. Another is to suppress insect populations by releasing either sterile males or males carrying female-specific dominant lethal genes into the environment. Newer genetic tools and methods are described.
Stakeholder Views on Engagement, Trust, Performance, and Risk Considerations About Use of Gene Drive Technology in Agricultural Pest Management
19900C. L. Goldsmith, K. E. Kang, E. Heitman, Z. N. Adelman, L. W. Buchman, D. Kerns, X. Liu, R. F. Medina and A. Vedlitz, Health Security, 2021-12-31 08:17:50.
Gene drive is an experimental technique that may make it possible to alter the genetic traits of whole populations of a species through the genetic modification of a relatively small number of individuals. This technology is sufficiently new that literature on the understanding and views of stakeholders and the public regarding the use of gene drive organisms in agricultural pest management is just beginning to emerge. Our team conducted a 2-pronged engagement process with Texas gene drive agricultural stakeholders to ascertain their values, beliefs, and preferences about the efficacy, safety, and risk management considerations of gene drive technology as a potential tool for agricultural pest management. We found that a majority of stakeholders support gene drive research and its potential use for managing agricultural pests. Our work with stakeholders confirms both their willingness to be engaged and the importance they place on stakeholder and public engagement regarding these issues, as well as the need to address these issues before use of gene drive as a pest management mechanism will be accepted and trusted.
Facilitating the Conversation: Gene Drive Classification
19766J. Overcash and A. Golnar, Health Security, 2021-12-29 13:09:10.
Gene drives are an emerging technology with tremendous potential to impact public health, agriculture, and conservation. While gene drives can be described simply as selfish genetic elements (natural or engineered) that are inherited at non-Mendelian rates, upon closer inspection, engineered gene drive technology is a complex class of biotechnology that uses a diverse number of genetic features to bias rates of inheritance. As a complex technology, gene drives can be difficult to comprehend, not only for the public and stakeholders, but also to risk assessors, risk managers, and decisionmakers not familiar with gene drive literature. To address this difficulty, we describe a gene drive classification system based on 5 functional characteristics. These characteristics include a gene drive's objective, mechanism, release threshold, range, and persistence. The aggregate of the gene drive's characteristics can be described as the gene drive's architecture. Establishing a classification system to define different gene drive technologies should make them more comprehensible to the public and provide a framework to guide regulatory evaluation and decisionmaking.
Modeling CRISPR gene drives for suppression of invasive rodents using a supervised machine learning framework
19764S. E. Champer, N. Oakes, R. Sharma, P. García-Díaz, J. Champer and P. W. Messer, PLoS Comput Biol, 17:e1009660. 2021-12-29 13:01:20.
Invasive rodent populations pose a threat to biodiversity across the globe. When confronted with these invaders, native species that evolved independently are often defenseless. CRISPR gene drive systems could provide a solution to this problem by spreading transgenes among invaders that induce population collapse, and could be deployed even where traditional control methods are impractical or prohibitively expensive. Here, we develop a high-fidelity model of an island population of invasive rodents that includes three types of suppression gene drive systems. The individual-based model is spatially explicit, allows for overlapping generations and a fluctuating population size, and includes variables for drive fitness, efficiency, resistance allele formation rate, as well as a variety of ecological parameters. The computational burden of evaluating a model with such a high number of parameters presents a substantial barrier to a comprehensive understanding of its outcome space. We therefore accompany our population model with a meta-model that utilizes supervised machine learning to approximate the outcome space of the underlying model with a high degree of accuracy. This enables us to conduct an exhaustive inquiry of the population model, including variance-based sensitivity analyses using tens of millions of evaluations. Our results suggest that sufficiently capable gene drive systems have the potential to eliminate island populations of rodents under a wide range of demographic assumptions, though only if resistance can be kept to a minimal level. This study highlights the power of supervised machine learning to identify the key parameters and processes that determine the population dynamics of a complex evolutionary system.
Cytoplasmic incompatibility in hybrid zones: infection dynamics and resistance evolution
19742E. S. Røed and J. Engelstädter, Journal of Evolutionary Biology, 2021-12-25 13:16:15.
Cytoplasmic incompatibility is an endosymbiont-induced mating incompatibility common in arthropods. Unidirectional cytoplasmic incompatibility impairs crosses between infected males and uninfected females, whereas bidirectional cytoplasmic incompatibility occurs when two host lineages are infected with reciprocally in compatible endosymbionts. Bidirectional cytoplasmic incompatibility is unstable in unstructured populations, but may be stable in hybrid zones. Stable coexistence of incompatible host lineages should generate frequent incompatible crosses. Therefore, hosts are expected to be under selection to resist their endosymbionts. Here, we for mulate a mathematical model of hybrid zones where two bidirectionally incompatible host lineages meet. We expand this model to consider the invasion of a hypothetical resistance allele. To corroborate our mathematical predictions, we test each prediction with stochastic, individual-based simulations. Our models suggest that hybrid zones may sustain stable coinfections of bidirectionally incompatible endosymbiont strains. Over a range of conditions, host are under selection for resistance against cytoplasmic incompatibility. Under asymetric migration, a resistance allele can facilitate infection turnover and subsequently either persist or become lost. The predictions we present may inform our understanding of the cophylogenetic relationship between the endosym biont Wolbachia and its hosts.
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.
From Wolbachia genomics to phenotype: molecular models of cytoplasmic incompatibility must account for the multiplicity of compatibility types
19733A. Namias, M. Sicard, M. Weill and S. Charlat, Current Opinion in Insect Science, 2021-12-23 13:03:28.
Wolbachia endosymbionts commonly induce cytoplasmic incompatibility, making infected males’ sperm lethal to the embryos unless these are rescued by the same bacterium, inherited from their mother. Causal genes were recently identified but two families of mechanistic models are still opposed. In the toxin–antidote model, interaction between the toxin and the antidote is required for rescuing the embryos. In host modification models, a host factor is misregulated in sperm and rescue occurs through compensation or withdrawal of this modification. While these models have been thoroughly discussed, the multiplicity of compatibility types, that is, the existence of many mutually incompatible strains, as seen in Culex mosquitoes, has not received sufficient attention. To explain such a fact, host modification models must posit that the same embryonic defects can be induced and rescued through a large variety of host targets. Conversely, the toxin–antidote model simply accommodates this pattern in a lock–key fashion, through variations in the toxin–antidote interaction sites.
Meiotic Cas9 expression mediates gene conversion in the male and female mouse germline
19726A. J. Weitzel, H. A. Grunwald, C. Weber, R. Levina, V. M. Gantz, S. M. Hedrick, E. Bier and K. L. Cooper, PLOS Biology, 19:e3001478. 2021-12-23 12:46:23.
Highly efficient gene conversion systems have the potential to facilitate the study of complex genetic traits using laboratory mice and, if implemented as a “gene drive,” to limit loss of biodiversity and disease transmission caused by wild rodent populations. We previously showed that such a system of gene conversion from heterozygous to homozygous after a sequence targeted CRISPR/Cas9 double-strand DNA break (DSB) is feasible in the female mouse germline. In the male germline, however, all DSBs were instead repaired by end joining (EJ) mechanisms to form an “insertion/deletion” (indel) mutation. These observations suggested that timing Cas9 expression to coincide with meiosis I is critical to favor conditions when homologous chromosomes are aligned and interchromosomal homologydirected repair (HDR) mechanisms predominate. Here, using a Cas9 knock-in allele at the Spo11 locus, we show that meiotic expression of Cas9 does indeed mediate gene conversion in the male as well as in the female germline. However, the low frequency of both HDR and indel mutation in both male and female germlines suggests that Cas9 may be expressed from the Spo11 locus at levels too low for efficient DSB formation. We suggest that more robust Cas9 expression initiated during early meiosis I may improve the efficiency of gene conversion and further increase the rate of “super-mendelian” inheritance from both male and female mice.
Weakly deleterious natural genetic variation amplifies probability of resistance in multiplexed gene drive systems
19904B. S. Khatri and A. Burt, bioRxiv, 2021.12.23.473701. 2021-12-23 08:31:18.
Evolution of resistance is a major barrier to successful deployment of gene drive systems to suppress natural populations. Multiplexed guide RNAs that require resistance mutations in all target cut sites is a promising strategy to overcome resistance. Using novel stochastic simulations that accurately model evolution at very large population sizes, we explore the probability of resistance due to three important mechanisms: 1) non-homologous end-joining mutations, 2) single nucleotide mutants arising de novo or, 3) single nucleotide polymorphisms pre-existing as standing variation. If the fraction of functional end-joining mutants is rare, we show that standing variation dominates, via a qualitatively new phenomenon where weakly deleterious variants significantly amplify the probability of multi-site resistance. This means resistance can be probable even with many target sites in not very large populations. This result has broad application to resistance arising in multi-site evolutionary scenarios including the evolution of vaccine escape mutations in large populations.Competing Interest StatementThe authors have declared no competing interest.
Interaction Between Entomology and Gene Technology: Bt-transgenic and Gene Drives for Pests Control .
20105J. C. Ndayıragıje, T. Özek, H. Çevik and İ. Karaca, Türk Bilim ve Mühendislik Dergisi, 3:108-115. 2021-12-22 17:00:56.
Pest control is the major agricultural activity for increasing crop productivity thus insuring food security. Recent pest management programs are depending too much on chemical pesticides, which are a threat to our health and environment. One of the greatest entomological achievements for the benefits of plant protection is the use of Bacillus thuringiensis to produce transgenic plants resisting pests. However, such organisms comprise inconveniences against human health and biodiversity in terms of genetic pollution. In many countries, the use of Genetically Modified Organisms is prohibited. This study review on integration of growing gene technology with actual scientific achievements can help to determine a sustainable solution to the pest’s problem. In this way, many literatures were referred on to comparatively criticize the effectiveness, safety and sustainability of gene drive over Bt transgenic based on scientific soundness. Gene drive technology is a new technic consisting of gene engineering and on-field monitoring of its transgenes. The case in point is the inappropriateness of Bt-transgenes. Practically, gene drive can be an alternative to Bacillus thuringiensis in pest control for increased safety and environmental protection.
chinmo-mutant spermatogonial stem cells cause mitotic drive by evicting non-mutant neighbors from the niche
19728C. Y. Tseng, M. Burel, M. Cammer, S. Harsh, M. S. Flaherty, S. Baumgartner and E. A. Bach, Developmental Cell, 2021-12-22 12:51:45.
Niches maintain a finite pool of stem cells via restricted space and short-range signals. Stem cells compete for limited niche resources, but the mechanisms regulating competition are poorly understood. Using the Drosophila testis model, we show that germline stem cells (GSCs) lacking the transcription factor Chinmo gain a competitive advantage for niche access. Surprisingly, chinmo(-/-) GSCs rely on a new mechanism of competition in which they secrete the extracellular matrix protein Perlecan to selectively evict non-mutant GSCs and then upregulate Perlecan-binding proteins to remain in the altered niche. Over time, the GSC pool can be entirely replaced with chinmo(-/-) cells. As a consequence, the mutant chinmo allele acts as a gene drive element; the majority of offspring inherit the allele despite the heterozygous genotype of the parent. Our results suggest that the influence of GSC competition may extend beyond individual stem cell niche dynamics to population-level allelic drift and evolution.
Temporal Viability of Aedes aegypti and Aedes albopictus Eggs Using Two Hygroscopic Substances as Preservatives under a Sterile Insect Technique (SIT) Program in Southern Mexico
19721E. N. Martínez-García, E. E. Díaz-González, C. F. Marina, J. G. Bond, J. J. Rodríguez-Rojas, G. Ponce-García, R. M. Sánchez-Casas and I. Fernández-Salas, Insects, 13. 2021-12-21 12:31:48.
Dengue and other Aedes-borne diseases have dramatically increased over the last decades. The Sterile Insect Technique (SIT) has been successfully used as part of integrated pest strategies to control populations of insect-plant and livestock pests and is currently being tested as a potential method to reduce mosquito populations in an environmentally friendly approach. However, during the mass rearing steps needed to produce millions of mosquitoes, egg storage and preservation are essential for a certain amount of time. Eggs of Aedes aegypti have a chorionic pad that functions as a sticky substance to glue them onto the inner walls of larval breeding sites. The chorionic pad is chemically made of hyaluronic acid, a hygroscopic compound, responsible to protect them from desiccation over time. Two commercial products with hygroscopic properties, hydrolyzed collagen, and Hyalurosmooth®, both were tested to assess their ability to prolong egg life storage for A. aegypti and A. albopictus. Results showed that 85–95% of Ae. aegypti eggs were able to hatch up to week 8 after being treated with both hydrophilic compounds, compared with the control 66.3%. These two substances showed promising effects for keeping Ae. aegypti eggs viable during prolonged storage in mass rearing insect production focused on vector control SIT programs.
Three Decades of Malaria Vector Control in Sudan: The Plausible Role of Sterile Insect Technique (SIT)
19977A. Elaagip and A. Adedapo, Genetically Modified and other Innovative Vector Control Technologies, 2021-12-21 11:51:34.
In Northern State, Sudan, a feasibility study for sterile insect technique (SIT) in an area-wide integrated pest management was established for the first time in an African country. The aim of the study was to see whether it is feasible, from a technical, an economical and a biological perspective, to use sterile male mosquitoes to control mosquito populations in designated areas in the African context. The project was focussed on Anopheles arabiensis, one of the major malaria vectors. Meteorological data, larval surveillance and population genetic studies were carried out on the disease vectors. The first phase of the study focussed on the development of an efficient sex-separation system, development of dose-sterility curves for the pupal and adult stages and testing of a range of doses in competition experiments to determine effective sterility dose. This stage was followed by a semi-field phase that monitored their swarming and mating behaviours, effectiveness of irradiated males in competitive experiments with wild males and insemination rates. Information regarding irradiation and transportation of irradiated males were also obtained during the study. Unfortunately, the SIT study was terminated in 2017 before starting field release of irradiated males. In spite of the challenges, such investment need not be totally abandoned as valuable experience has been gained and capacity built, which are of high value to malaria control program in Sudan.
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.
Aedes Control Using Sterile Insect Technique (SIT) in Malaysia
19973W. A. Nazni, G.-N. Teoh, S. I. Shaikh Norman Hakimi, M. A. Muhammad Arif, M. Tanusshni, M. A. Nuradila, A. Nurfarahin Hanini, I. A. Shazia, A.-M. Tan, H. Rabizah, M. D. Ahmad Zainuri, A. Hasnor Hadi, Y.-L. Cheong, A. Norazah, H. Maiga, R. S. Lees and L. H, Genetically Modified and other Innovative Vector Control Technologies, 2021-12-21 11:41:43.
The continued occurrence of massive outbreaks of Aedes-borne viral diseases of dengue, chikungunya, Zika and yellow fever, in spite of intensive and extensive application of conventional control measures, necessitates application of new tools, such as sterile insect technique (SIT), to stem the tide. Sterile insect technique is a form of biological control method, whereby sterile male insects are released in overwhelming numbers in the wild. These sterile males compete with the wild males to mate with the wild females. The females mated with sterile males will produce sterile eggs that will not hatch. Sustained release of sterile males over a period of time will lead to suppression or elimination of the natural population. Sterility is induced by gamma ray from the radioisotope of cobalt-60 and cesium-137 or X-ray. SIT is safe, cost-effective and environmentally non-polluting, and insects are unable to develop resistance to this method. SIT has a strong track record of success in elimination of agricultural pests, and this led to increased interest in using SIT against mosquitoes of public health importance. Studies and trials against Aedes were conducted in the 1960s and, more recently, against Ae. albopictus with promising results. Attempts were also made to apply SIT for the control of Aedes in several countries. Malaysia’s first experience with SIT was in the 1990s, when the Malaysian Nuclear Agency teamed with the MARDI and local universities to sterilise an agricultural pest, the diamondback moth. To prepare for the possible threat of introducing the Old World screw worm (Chrysomya bezziana) into Australia from neighbouring countries, from 1995 to 2000, Australia and Malaysia undertook a collaborative myiasis control research project located at the Institut Haiwan, Kluang, Malaysia. The project assisted in suppression trials of the screw worm in Malaysia and supported research that developed and evaluated improved Old World screw worm suppression and eradication techniques. In 2014, in collaboration with the Malaysian Nuclear Agency, the IMR conducted preliminary studies to determine the optimum sterilising dose of gamma irradiation against Ae. aegypti. In addition, the impact of sterilisation on the biological parameters of Ae. aegypti was also determined. The most effective sterilising dose that did not adversely affect the male was determined to be 55 Gy. Subsequently, a new initiative of field release of sterile Aedes aegypti males for the control of dengue was initiated in 2019. This 2-year programme will aim to release gamma ray-sterilised Ae. aegypti males in three trial sites to reduce the natural mosquito population to a level below the threshold required for dengue transmission. To ensure public acceptance, public engagement, a prerequisite for a successful release programme, will be conducted intensively prior to the release.
Integrated Management of Malaria Vectors in Africa
19971R. Mbabazi, K. Maredia, B. B. El-Sayed, A. K. Babumba, M. Savadogo and O. Akinbo, Genetically Modified and other Innovative Vector Control Technologies, 2021-12-21 11:36:56.
Malaria disease is a major public health burden in Africa. The control of malaria vectors is a critical component for prevention, management, and eradication of malaria disease. This chapter presents information on the current status of malaria vector control in Africa with emphasis on integrated vector management (IVM) programs. The chapter highlights innovative and emerging technologies such as sterile insect technique, gene drive, Wolbachia-based biological control, and other technologies for malaria vector control in Africa which can be integrated into IVM programs. The chapter also provides global resources on malaria vector management programs.
Engineering RNA Interference-Based Dengue Virus Resistance in the Mosquito Vector Aedes aegypti: The Current Status and Future Directions
19969S. D. Denipitiyage, Y. I. N. S. Gunawardene, Z. Federico and R. S. Dassanayake, Genetically Modified and other Innovative Vector Control Technologies, 2021-12-21 11:32:49.
Dengue is an acute, febrile disease caused by the dengue viruses (DENV) comprising four serotypes and transmitted by the mosquito vector Ae. aegypti. DENV are single-stranded, positive-sense RNA viruses of the family Flaviviridae. Dengue is declared as a current significant challenge in the Southeast Asia, imposing growing burden on infected populations. To date, dengue control has mostly relied on vector control strategies which have largely become ineffective. There is, therefore, an urgent need for novel vector control strategies. Development of genetically modified mosquito vectors to manipulate disease-vectoring populations has gathered increased interest in recent time. RNAi-mediated viral resistance contributes to the suppression of viruses, including DENV in the mosquito vector Ae. aegypti. With recent advances in the field of molecular biology, we and other scientists are continuing to engineer genes that confer virus resistance to reduce transmission rates of DENV and introducing these genes into the mosquito genome. Even though scientists successfully generated mosquito refractory to DENV2–4, no mosquito refractory to all four serotypes has been developed to date. This limitation can be overcome by systematic analysis of the molecular mechanisms of RNAi in the mosquito vector Ae. aegypti. An enhanced understanding of RNAi function in the mosquito vector Ae. aegypti will facilitate the application of RNAi to control the transmission of the dengue disease in the future. Here, based on current understanding of the RNAi, we discuss the mechanisms of RNAi in the mosquito vector Ae. aegypti. We also provide guidelines for optimal design of RNAi experiments in Ae. aegypti with the possible risks associated with them along with proposed solutions.
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