Keywords: Culex
“Millions have been released.” Hawaii’s beautiful birds are dying. But scientists have a controversial plan to save them
35457James Fair, BBC Wildlife Magazine, 2026-02-24 09:58:30.
About 6-7 million years ago, common rosefinches – which are today found across a vast expanse of northern Eurasia and are even occasional winter visitors to the British Isles – island-hopped their way from the Russian Far East across the Pacific Ocean and arrived in the newly formed, volcanic land masses of Hawaii. There, a single species evolved into an extended family of 56 Hawaiian honeycreepers, many of which only barely resemble their pioneering ancestor. Take, for example, the gorgeous scarlet honeycreeper or i’iwi, with its huge downward curving bill that is perfectly adapted for extracting nectar from endemic Hawaiian flowers. At first glance, it looks nothing like a finch. It’s an amazing story, but also a tragic one, because according to the US Fish & Wildlife Service, 39 of Hawaii’s honeycreepers are extinct, and 11 of the remaining 17 are threatened. One of the biggest factors in this natural history catastrophe is avian malaria. Neither the single-celled organism that causes malaria, nor the mosquito that transmits it, are native to Hawaii, so honeycreepers and other endemic birds have almost no immunity to it. All conservationists agree that something needs to be done – and quickly – if we are to save those that remain. Step forward scientists such as Tim Harvey-Samuel, an expert in arthropod genetics at the University of Keele. Harvey-Samuel and his team are seeing whether they can “modify the mosquito population in Hawaii such that it’s no longer able to transmit avian malaria.” The idea is to insert a gene into the mosquito (Culex quinquefasciatus) so that it doesn’t allow the Plasmodium protozoan that causes malaria to complete its life-cycle.
Dispersal and survival of gamma-irradiated Culex quinquefasciatus: Implications for sterile insect technique applications
35207Nungki Hapsari Suryaningtyas, Raden Wisnu Nurcahyo, Beni Ernawan, et al., Open Veterinary Journal, 15:3054-3062. 2025-10-02 14:51:05.
Culex quinquefasciatus is a major vector of filariasis and other mosquito-borne diseases. The sterile insect technique (SIT) has been widely used to suppress mosquito populations, but its effectiveness depends on the dispersal, survival, and competitiveness of sterile males. This study evaluated the dispersal range, survival rate, and recapture success of gamma-irradiated Cx. quinquefasciatus under field conditions. A mark-release-recapture (MRR) experiment was conducted using sterile male and female Cx. quinquefasciatus. Two release events were conducted, and recapture data were collected over seven days using BG-Sentinel-2 traps baited with octanol placed within a 250-m radius. The irradiated males traveled an average of 143.18 m (FR50: 92.78 m; FR90: 220.02 m), and the females dispersed 146.26 m (FR50: 95.26 m; FR90: 227.25 m). Dispersal distance was significantly influenced by release site in males (p = 0.0089) and females (p = 0.0042) but not by recapture day (p > 0.89). Recapture location significantly affected dispersal in both sexes (p < 0.0001). The daily survival probabilities of males and females were 0.88 and 0.69, respectively, with corresponding life expectancies of 7.57 and 2.71 days. The dispersal and survival of sterile Cx. quinquefasciatus are affected by release strategies. To optimize SIT, further studies should refine the marking techniques, explore a combination of trapping methods, and evaluate the dispersal patterns across varied landscapes. These findings offer valuable insights into improving the implementation of SIT for Cx. quinquefasciatus population control.
Sequence mismatch between gene-drive and target-site flanking regions significantly impairs homing efficiency in Culex quinquefasciatus
35007Tim Harvey-Samuel, Rajdeep Kaur, Philip T Leftwich, et al., bioRxiv, 2025-08-04 11:03:26.
CRISPR/Cas9-based homing gene-drives (homing-drives) hold enormous potential as control tools for mosquito disease-vectors. These genomically-encoded technologies spread themselves through target populations by creating double-stranded DNA breaks on homologous chromosomes, into which the homing-drives are copied (homed). Homing is dependent on sequence homology between the genomic regions flanking the transgene insertion and the break site. Homing efficiency (i.e. copying rate) substantially impacts the power of these systems: less efficient homing-drives spread slower, have fewer applications and are more resistance-prone. Understanding what influences homing-drive efficiency is therefore vital to the successful use of these technologies. Here we report a novel mechanism by which a homing-drives efficiency can be significantly impaired by natural sequence variation within a population into which it is spreading. Using a kmo-targeting split homing-drive in the West Nile virus mosquito Culex quinquefasciatus, we found that target-site heterology (sequence mismatch between the genomic regions flanking the target cut-site and the homing-drive transgene) of less than 10% reduced homing efficiency by up to 54%. While substantial research effort has been dedicated to increasing homing-drive efficiency through optimisation of within-construct components, our results highlight that the real-world efficacy of these systems may in part depend on variation beyond these controllable factors.
Culex-Transmitted Diseases: Mechanisms, Impact, and Future Control Strategies using Wolbachia
31030Madhav, M.; Blasdell, K.R.; Trewin, B.; Paradkar, P.N.; López-Denman, A.J., Viruses, 16:1134. 2024-07-15 11:40:32.
Mosquitoes of the Culex genus are responsible for a large burden of zoonotic virus transmission globally. Collectively, they play a significant role in the transmission of medically significant diseases such as Japanese encephalitis virus and West Nile virus. Climate change, global trade, habitat transformation and increased urbanisation are leading to the establishment of Culex mosquitoes in new geographical regions. These novel mosquito incursions are intensifying concerns about the emergence of Culex-transmitted diseases and outbreaks in previously unaffected areas. New mosquito control methods are currently being developed and deployed globally. Understanding the complex interaction between pathogens and mosquitoes is essential for developing new control strategies for Culex species mosquitoes. This article reviews the role of Culex mosquitos as vectors of zoonotic disease, discussing the transmission of viruses across different species, and the potential use of Wolbachia technologies to control disease spread. By leveraging the insights gained from recent successful field trials of Wolbachia against Aedes-borne diseases, we comprehensively discuss the feasibility of using this technique to control Culex mosquitoes and the potential for the development of next generational Wolbachia-based control methods.
A synthetic biology approach to transgene expression
27699P. Leftwich, T. , J. Purcell, C. , M. Anderson, A. E. , R. Fragkoudis, S. Basu, G. Lycett, T. and L. Alphey, bioRxiv, 2023.08.31.555539. 2023-08-31 09:13:32.
The ability to control gene expression is pivotal in genetic engineering and synthetic biology. However, in most non-model and pest insect species, empirical evidence for predictable modulation of gene expression levels is lacking. This knowledge gap is critical for genetic control systems, particularly in mosquitoes, where transgenic methods offer novel routes for pest control. Commonly, the choice of RNA polymerase II promoter (Pol II) is the primary method for controlling gene expression, but the options are limited. To address this, we developed a systematic approach to characterize modifications in translation initiation sequences (TIS) and 3' untranslated regions (UTR) of transgenes, enabling the creation of a toolbox for gene expression modulation in mosquitoes and potentially other insects. The approach demonstrated highly predictable gene expression changes across various cell lines and promoter sequences, representing a significant advancement in mosquito synthetic biology gene expression.Competing Interest StatementThe authors have declared no competing interest.
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.
CRISPR-based gene drives generate super-Mendelian inheritance in the disease vector Culex quinquefasciatus
25865T. Harvey-Samuel, X. Feng, E. M. Okamoto, D.-K. Purusothaman, P. T. Leftwich, L. Alphey and V. M. Gantz, bioRxiv, 2023.06.12.544656. 2023-06-15 08:40:13.
Culex mosquitoes pose a significant public health threat as vectors for a variety of diseases including West Nile virus and lymphatic filariasis, and transmit pathogens threatening livestock, companion animals, and endangered birds. Rampant insecticide resistance makes controlling these mosquitoes challenging and necessitates the development of new control strategies. Gene drive technologies have made significant progress in other mosquito species, although similar advances have been lagging in Culex. Here we test the first CRISPR-based homing gene drive for Culex quinquefasciatus, demonstrating the possibility of using this technology to control Culex mosquitoes. Our results show that the inheritance of two split-gene-drive transgenes, targeting different loci, are biased in the presence of a Cas9-expressing transgene although with modest efficiencies. Our findings extend the list of disease vectors where engineered homing gene drives have been demonstrated to include Culex alongside Anopheles and Aedes, and pave the way for future development of these technologies to control Culex mosquitoes
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.
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.
Paternal transmission of the Wolbachia CidB toxin underlies cytoplasmic incompatibility
20434B. Horard, K. Terretaz, A. S. Gosselin-Grenet, H. Sobry, M. Sicard, F. Landmann and B. Loppin, Current Biology, 2022-02-01 08:53:36.
Wolbachia are widespread endosymbiotic bacteria that manipulate the reproduction of arthropods through a diversity of cellular mechanisms. In cytoplasmic incompatibility (CI), a sterility syndrome originally discovered in the mosquito Culex pipiens, uninfected eggs fertilized by sperm from infected males are selectively killed during embryo development following the abortive segregation of paternal chromosomes in the zygote. Despite the recent discovery of Wolbachia CI factor (cif) genes, the mechanism by which they control the fate of paternal chromosomes at fertilization remains unknown. Here, we have analyzed the cytological distribution and cellular impact of CidA and CidB, a pair of Cif proteins from the Culex-infecting Wolbachia strain wPip. We show that expression of CidB in Drosophila S2R+ cells induces apoptosis unless CidA is co-expressed and associated with its partner. In transgenic Drosophila testes, both effectors colocalize in germ cells until the histone-to-protamine transition in which only CidB is retained in maturing spermatid nuclei. We further show that CidB is similarly targeted to maturing sperm of naturally infected Culex mosquitoes. At fertilization, CidB associates with paternal DNA regions exhibiting DNA replication stress, as a likely cause of incomplete replication of paternal chromosomes at the onset of the first mitosis. Importantly, we demonstrate that inactivation of the deubiquitylase activity of CidB does not abolish its cell toxicity or its ability to induce CI in Drosophila. Our study thus demonstrates that CI functions as a transgenerational toxin-antidote system and suggests that CidB acts by poisoning paternal DNA replication in incompatible crosses.
Beyond the eye: Kynurenine pathway impairment causes midgut homeostasis dysfunction and survival and reproductive costs in blood-feeding mosquitoes
19915V. Bottino-Rojas, I. Ferreira, R. D. Nunes, X. Feng, T. B. Pham, A. Kelsey, R. Carballar-Lejarazú, V. Gantz, P. L. Oliveira and A. A. James, Insect Biochemistry and Molecular Biology, 103720. 2022-01-06 08:57:05.
Insect ommochrome biosynthesis pathways metabolize tryptophan to generate eye-color pigments and naturally occurring alleles of pathway genes are useful phenotypic markers in transgenesis studies. Pleiotropic effects of mutations in some genes exert a load on both survival and reproductive success in blood-feeding species. Here, we investigated the challenges imposed on mosquitoes by the increase of tryptophan resulting from blood meal digestion and the impact of disruptions of the ommochrome biosynthesis pathway. Female mosquitoes with spontaneous and induced mutations in the orthologs of the genes encoding kynurenine hydroxylase in Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus exhibited impaired survival and reproductive phenotypes that varied in type and severity among the species. A compromised midgut permeability barrier function was also observed in An. stephensi. Surprisingly, mutant mosquitoes displayed an increase in microbiota compared to controls that was not accompanied by a general induction of immune genes. Antibiotic treatment rescued some deleterious traits implicating a role for the kynurenine pathway (KP) in midgut homeostasis. Supplemental xanthurenic acid, a KP end-product, rescued lethality and limited microbiota proliferation in Ae. aegypti. These data implicate the KP in the regulation of the host/microbiota interface. These pleiotropic effects on mosquito physiology are important in the development of genetic strategies targeting vector mosquitoes.
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.
Prevalence and molecular characterization of Wolbachia in field-collected Aedes albopictus, Anopheles sinensis, Armigeres subalbatus, Culex pipiens and Cx. tritaeniorhynchus in China
19078Y. Yang, Y. He, G. Zhu, J. Zhang, Z. Gong, S. Huang, G. Lu, Y. Peng, Y. Meng, X. Hao, C. Wang, J. Sun and S. Shang, PLOS Neglected Tropical Diseases, 15:e0009911. 2021-10-29 20:41:21.
Wolbachia are maternally transmitted intracellular bacteria that can naturally and artificially infect arthropods and nematodes. Recently, they were applied to control the spread of mosquito-borne pathogens by causing cytoplasmic incompatibility (CI) between germ cells of females and males. The ability of Wolbachia to induce CI is based on the prevalence and polymorphism of Wolbachia in natural populations of mosquitoes. In this study, we screened the natural infection level and diversity of Wolbachia in field-collected mosquitoes from 25 provinces of China based on partial sequence of Wolbachia surface protein (wsp) gene and multilocus sequence typing (MLST). Among the samples, 2489 mosquitoes were captured from 24 provinces between July and September, 2014 and the remaining 1025 mosquitoes were collected month-by-month in Yangzhou, Jiangsu province between September 2013 and August 2014. Our results showed that the presence of Wolbachia was observed in mosquitoes of Aedes albopictus (97.1%, 331/341), Armigeres subalbatus (95.8%, 481/502), Culex pipiens (87.0%, 1525/1752), Cx. tritaeniorhynchus (17.1%, 14/82), but not Anopheles sinensis (n = 88). Phylogenetic analysis indicated that high polymorphism of wsp and MLST loci was observed in Ae. albopictus mosquitoes, while no or low polymorphisms were in Ar. subalbatus and Cx. pipiens mosquitoes. A total of 12 unique mutations of deduced amino acid were identified in the wsp sequences obtained in this study, including four mutations in Wolbachia supergroup A and eight mutations in supergroup B. This study revealed the prevalence and polymorphism of Wolbachia in mosquitoes in large-scale regions of China and will provide some useful information when performing Wolbachia-based mosquito biocontrol strategies in China.
Scientists use gene editing tool to target mosquito-spread disease
18650Medical Research Council, Phys Org, 2021-09-13 20:12:56.
Advances in genome editing have allowed the development of genetic insect control methods, which could be highly effective and are species-specific. The results have been published in Scientific Reports. Scientists showed that a method involving a gene editing tool called CRISPR/Cas9 could be used to successfully introduce a gene for a fluorescent protein into the genome of southern house mosquitoes. The gene could be passed on to the next generation through mating. This is a vital component of generating genetic pest management tools. It will allow the desired traits (such as the inability to spread a disease or produce fertile offspring) to be spread throughout a population. The inserted gene produces red fluorescence proteins so that mosquitoes with one or more edited gene fluoresce red. Scientists targeted an eye color gene for the insertion site of the fluorescence gene so mosquitoes that inherited two edited genes from their parents would have white eyes, not black. Both these traits make it easier for scientists to easily identify mosquitoes whose genomes had been modified.
CRISPR/Cas-9 mediated knock-in by homology dependent repair in the West Nile Virus vector Culex quinquefasciatus Say
17811D.-K. Purusothaman, L. Shackleford, M. A. E. Anderson, T. Harvey-Samuel and L. Alphey, Scientific Reports, 11:14964. 2021-07-22 14:14:08.
Culex quinquefasciatus Say is a mosquito distributed in both tropical and subtropical regions of the world. It is a night-active, opportunistic blood-feeder and vectors many animal and human diseases, including West Nile Virus and avian malaria. Current vector control methods (e.g. physical/chemical) are increasingly ineffective; use of insecticides also imposes hazards to both human and ecosystem health. Advances in genome editing have allowed the development of genetic insect control methods, which are species-specific and, theoretically, highly effective. CRISPR/Cas9 is a bacteria-derived programmable gene editing tool that is functional in a range of species. We describe the first successful germline gene knock-in by homology dependent repair in C. quinquefasciatus. Using CRISPR/Cas9, we integrated an sgRNA expression cassette and marker gene encoding a fluorescent protein fluorophore (Hr5/IE1-DsRed, Cq7SK-sgRNA) into the kynurenine 3-monooxygenase (kmo) gene. We achieved a minimum transformation rate of 2.8%, similar to rates in other mosquito species. Precise knock-in at the intended locus was confirmed. Insertion homozygotes displayed a white eye phenotype in early-mid larvae and a recessive lethal phenotype by pupation. This work provides an efficient method for engineering C. quinquefasciatus, providing a new tool for developing genetic control tools for this vector.
New CRISPR Tools Can Help Contain Mosquito Disease Transmission
17191Anonymous, labcompare, 2021-06-01 20:26:34.
Scientists have now developed several genetic editing tools that help pave the way to an eventual gene drive designed to stop Culex mosquitoes from spreading disease. As detailed in the journal Nature Communications, Xuechun Feng, Valentino Gantz and their colleagues at Harvard Medical School and National Emerging Infectious Diseases Laboratories developed a Cas9/guide-RNA expression "toolkit" designed for Culex mosquitoes. Since such little attention in genetic engineering has been devoted to Culex mosquitoes, the researchers were required to develop their toolkit from scratch, starting with a careful examination of the Culex genome. While Culex mosquitoes are less problematic in the United States, they are much more of a health risk in Africa and Asia, where they transmit the worm causing filariasis, a disease that can lead to a chronic debilitating condition known as elephantiasis. The researchers also demonstrated that their tools could work in other insects.
Researchers Create New CRISPR Tools to Help Contain Mosquito Disease Transmission
18225M. Aguilera, UC San Diego News Center, 2021-05-28 15:43:14.
Much less genetic engineering has been devoted to Culex genus mosquitoes, which spread devastating afflictions stemming from West Nile virus—the leading cause of mosquito-borne disease in the continental United States—as well as other viruses such as the Japanese encephalitis virus (JEV) and the pathogen causing avian malaria, a threat to Hawaiian birds.University of California San Diego scientists have now developed several genetic editing tools that help pave the way to an eventual gene drive designed to stop Culex mosquitoes from spreading disease. Gene drives are designed to spread modified genes, in this case those that disable the ability to transmit pathogens, throughout the targeted wild population.As detailed in the journal Nature Communications, Xuechun Feng, Valentino Gantz and their colleagues at Harvard Medical School and National Emerging Infectious Diseases Laboratories developed a Cas9/guide-RNA expression “toolkit” designed for Culex mosquitoes. Since such little attention in genetic engineering has been devoted to Culex mosquitoes, the researchers were required to develop their toolkit from scratch, starting with a careful examination of the Culex genome.
New CRISPR tools help contain mosquito disease transmission: Genetics toolkit targets less researched Culex mosquitoes, which transmit West Nile virus and avian malaria.
17145University of California - San Diego, ScienceDaily, 2021-05-28 13:29:00.
Since the onset of the CRISPR genetic editing revolution, scientists have been working to leverage the technology in the development of gene drives that target pathogen-spreading mosquitoes such as Anopheles and Aedes species, which spread malaria, dengue and other life-threatening diseases. Much less genetic engineering has been devoted to Culex genus mosquitoes, which spread devastating afflictions stemming from West Nile virus -- the leading cause of mosquito-borne disease in the continental United States -- as well as other viruses such as the Japanese encephalitis virus (JEV) and the pathogen causing avian malaria, a threat to Hawaiian birds. University of California San Diego scientists have now developed several genetic editing tools that help pave the way to an eventual gene drive designed to stop Culex mosquitoes from spreading disease. Gene drives are designed to spread modified genes, in this case those that disable the ability to transmit pathogens, throughout the targeted wild population.
Optimized CRISPR tools and site-directed transgenesis towards gene drive development in Culex quinquefasciatus mosquitoes
17147X. Feng, V. López Del Amo, E. Mameli, M. Lee, A. L. Bishop, N. Perrimon and V. M. Gantz, Nature Communications, 12:2960. 2021-05-20 13:34:20.
Culex mosquitoes are a global vector for multiple human and animal diseases, including West Nile virus, lymphatic filariasis, and avian malaria, posing a constant threat to public health, livestock, companion animals, and endangered birds. While rising insecticide resistance has threatened the control of Culex mosquitoes, advances in CRISPR genome-editing tools have fostered the development of alternative genetic strategies such as gene drive systems to fight disease vectors. However, though gene-drive technology has quickly progressed in other mosquitoes, advances have been lacking in Culex. Here, we develop a Culex-specific Cas9/gRNA expression toolkit and use site-directed homology-based transgenesis to generate and validate a Culex quinquefasciatus Cas9-expressing line. We show that gRNA scaffold variants improve transgenesis efficiency in both Culex quinquefasciatus and Drosophila melanogaster and boost gene-drive performance in the fruit fly. These findings support future technology development to control Culex mosquitoes and provide valuable insight for improving these tools in other species.
Optimized CRISPR tools and site-directed transgenesis in Culex quinquefasciatus mosquitoes for gene drive development
16372X. Feng, V. Lopez Del Amo, E. Mameli, M. Lee, A. L. Bishop, N. Perrimon and V. M. Gantz, bioRxiv, 2021.02.10.430702. 2021-02-11 20:33:00.
Here, we developed a Culex-specific Cas9/gRNA expression toolkit and used site-directed homology-based transgenesis to generate and validate a Culex quinquefasciatus Cas9-expressing line. We showed that gRNA scaffold variants improve transgenesis efficiency in both Culex and Drosophila and boost gene-drive performance in the fruit fly. These findings support future technology development to control Culex mosquitoes and provide valuable insight for improving these tools in other species.
Targeting female flight for genetic control of mosquitoes
15310D. Navarro-Payá, I. Flis, M. A. E. Anderson, P. Hawes, M. Li, O. S. Akbari, S. Basu and L. Alphey, PLOS Neglected Tropical Diseases, 14:e0008876. 2020-12-03 20:11:01.
The yellow fever mosquito and the Southern house mosquito are important vectors of infectious diseases. Given their widespread presence across tropical and subtropical regions of the world and the increased risk of spread due to global warming there is a growing need for population control. Gene drives aim to spread a genetic element within target genes required for mosquito reproduction to disrupt their function and crash a population. Female-specific genes provide interesting candidates for population control since female mosquitoes determine the reproductive capacity of a population as well as being the actual vectors of disease. Here we describe a study on Actin-4 loss in both Aedes aegypti and Culex quinquefasciatus, where we observe female-specific disruption of flight ability and propose it as a candidate for genetic methods of population suppression.
Cytoplasmic incompatibility: an autocidal mechanism for mosquito population control
13893V. Dev, BugBitten BMC, 2020-08-18 13:23:13.
Cytoplasmic incompatibility resulting in non-reciprocal fertility is a naturally occurring phenomenon, but remains unexplored to greater extent for the control of insect vector populations. This mechanism deserves priority for mosquito control and reducing disease transmission, being non-insecticidal and easier to operate with minimal investments.
Research team genetically modifies mosquito; now completing construction of full gene drive system
12688University of Hawaii, UH Hilo News, 2020-06-18 20:23:40.
A research group at the University of Hawai‘i at Hilo is currently completing construction of the full gene drive system of the Hawai‘i-sourced southern house mosquito (Culex quinquefasciatus), and plan to use CRISPR technology to insert it alongside an eye-color phenotype marker. CRISPR allows researchers to easily alter DNA sequences and modify gene function.
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.
Genetic pest management technologies to control invasive rodents
11576D. Kanavy and D. Threadgill, Island invasives: scaling up to meet the challenge, 2019-03-05 15:20:05.
Many strategies exist to manage invasive pests on islands, ranging from poison to trapping, with varying degrees of success. Genetic technologies are increasingly being applied to insect pests, but so far, not to vertebrates. We are implementing a genetic strategy to eradicate invasive mouse populations as another tool for pest control. Mus musculus, the common house mouse, is one of the most widespread invasive species. Mice threaten human health, agriculture, and biodiversity on many islands, particularly seabirds. Seabirds are endangered indirectly through competition for resources or predators being attracted by the mice or directly with mice attacking chicks and eggs. Rodenticides are the most common method of eradicating mice, but their use leads to poisoning of non-target species and has limited efficacy against mice. An approach that could eliminate non-target species impact would be to engineer daughterless mice linked to a gene drive system for self-sustained propagation. For this project, we have investigated exploiting a naturally occurring gene drive, the t-complex. Using the t w2 haplotype of the t-complex, we observed the t w2 haplotype being transmitted to offspring with a transmission distortion ratio of 95.3%. The daughterless phenotype is being accomplished by inserting the Sry gene (male sex-determining gene) into an autosome containing the tw2 haplotype via CRISPR/Cas9 gene editing. The presence of Sry will induce testis formation, regardless of the sex chromosomes naturally inherited. When Sry is inserted into the t-complex, the desired gene will spread through the population, eliminating female offspring. This model system will support studies to evaluate the effectiveness of crashing an invasive population without adversely affecting other
Trialling gene drives to control invasive species: what, where and how?
11573T. Harvey-Samuel, K. J. Campbell, M. Edgington and L. Alphey, Island invasives: scaling up to meet the challenge, 2019-03-05 15:16:48.
The control of invasive species would be enhanced through the addition of novel, more effective and sustainable pest management methods. One control option yet to be trialled in the field is to deploy transgene-based ‘Gene Drives’: technologies which force the inheritance of a genetic construct through the gene pool of a wild population, suppressing it or replacing it with a less harmful form. There is considerable interest in applying gene drives to currently intractable invasives across a broad taxonomic range. However, not all species will make efficient or safe targets for these technologies. Additionally, the safety and efficacy of these systems will vary according to where they are deployed, the specific molecular design chosen, and how these factors interact with the ecology of the target pest. Given the transformative but also controversial nature of gene drives, it is imperative that their first field trials are able to successfully demonstrate that they can be used safely and efficiently. Here, we discuss how to maximise the probability of this outcome through considering three important questions: What types of invasive species should we use to trial gene drives? Where should we be trialling them? and How should these trials be conducted? In particular, we focus on the ecological, genetic and geographic features of small, isolated islands which make them ideal locations for these initial trials. A case study of an island invasive that is deemed highly appropriate for gene drive intervention, and for which gene drive development is currently underway (Mus musculus), is used to further explore these concepts
Wolbachia and cytoplasmic incompatibility in mosquitoes
4300Sinkins, SP, Insect Biochemistry and Molecular Biology, 34:723-729. 2004-01-18 00:00:00.
Wolbachia are maternally inherited bacteria that induce cytoplasmic incompatibility in mosquitoes, and are able to use these patterns of sterility to spread themselves through populations. For this reason they have been proposed as a gene drive system for mosquito genetic replacement, as well as for the reduction of population size or for modulating population age structure in order to reduce disease transmission. Here, recent progress in the study of mosquito Wolbachia is reviewed. We now have much more comprehensive estimates of the parameters that can affect the spread of Wolbachia through natural populations from low starting frequencies. and for waves of spread to be maintained in the face of partial barriers to gene flow. In Aedes albopictits these dynamics are extremely favourable, with very high maternal transmission fidelity and levels of incompatibility recorded. Correspondence between measurements taken in the lab and field is much better than in the Drosophila simulans model system. Important research goals are also discussed, including Wolbachia transformation, interspecific transfer and the elucidation of the mechanisms of incompatibility and rescue; all will be aided by a wealth of new Wolbachia genome information. (C) 2004 Elsevier Ltd. All rights reserved.
Population replacement in Culex-fatigans by means of cytoplasmic incompatibility .2. Field cage experiments with overlapping generations
6276C. F. Curtis, Bulletin of the World Health Organization, 53:107-119. 1976-01-08 16:51:11.
Three experiments were carried out in field cages to test the principle of " transport" of a desirable gene or chromosome into a wild Culex fatigans population as a result of the sterility in cross-matings associated with cytoplasmic incompatibility. Cycling populations of Delhi origin were established in the cages and daily releases were made of the IS31B strain, which has Paris cytoplasm and carries a male-linked translocation. It was shown that, if sufficient releases were made to establish a majority of the Paris cytoplasmic type, complete replacement by this cytoplasmic type subsequently occurred. However, as a result of partial compatibility of males of the Delhi population with Paris females, " recombinant " males with Paris cytoplasm and no translocation were produced. In an experiment in which a continuous low rate of " immigration " of a strain of Delhi origin was simulated, a gradual increase of the Paris cytoplasm non-translocated type occurred, and renewed IS31B releases were necessary after 5 months to restore the predominance of this type. The results are compared with computer predictions and discussed in relation to the transport of genes for filaria refractoriness or chromosome translocations into wild populations.
Population replacement in Culex fatigens by means of cytoplasmic incompatibility. Laboratory experiments with non-overlapping generations
6291C. F. Curtis and T. Adak, Bulletin of the World Health Organization, 51:249-255. 1974-01-08 19:45:42.
Bidirectional cytoplasmic incompatibility in the Culex pipiens complex appears to provide a mechanism for the replacement of a wild population by a strain refractory to filaria or a strain made partly sterile by a translocation. As a preliminary test of the feasibility of the replacement process, various ratios of strains with the cytoplasm of either Delhi or Paris, which are bidirectionally incompatible, were tested in laboratory cages. Where one strain was marked with the ruby-eye gene, this strain always declined in frequency in the next generation. In experiments in which the Paris strain was marked with a male-linked translocation complex, after 2-4 generations of breeding there was complete elimination of either the Paris or the Delhi type depending, as expected, on the relative frequencies of the two types with which the population began. In one experiment a type with Paris cytoplasm devoid of the translocation was found. This type increased in frequency in succeeding generations. The possible causes of origin of this type and its relevance to the practical use of the replacement principle are discussed.
Eradication of Culex pipiens fatigans through cytoplasmic incompatibility.
6278H. Laven, Nature, 216:383. 1967-10-28 16:57:49.
Culex pipiens fatigans is the chief vector of filariasis in south-east Asia. Urbanization has often caused the numbers of this mosquito-and with it the danger of filariasis infection-to increase alarmingly. The natural vigour, tolerance and fast development of resistance to insecticides of this mosquito necessitate the development of other control methods, and cytoplasmic incompatibility2 seems to be an ideal means.
Contact Us
Alex Sullivan
Foundation for the
National Institutes of Health
geneconvenevi@fnih.org