Location: Mosquito and Fly Research
2020 Annual Report
Accomplishments
1. Isolation of two derivative mosquito strains. ARS researchers at Gainesville, Florida, and DoD scientists collaborated in the isolation of two derivative strains with different resistance profiles to provide a source of characterized organisms for use as positive and negative controls in both genetic and toxicologic resistance assays. These organisms are already of interest to the state of Louisiana for use in a resistance testing program and will be the strains used for assay validation in a Florida statewide resistance characterization study. Use and characterization of these strains gives measures to assist local mosquito control programs in determining insecticide resistance levels in local populations.
2. Development of a rapid resistance assay. ARS researchers at Gainesville, Florida, and DoD collaborating scientists developed a novel, rapid assay for assessment of genetic pyrethroid insecticide resistance in Cx. quinquefasciatus to assist in effective mosquito control decision making. While other assays exist, they use expensive reagents or require additional upstream sample purification, both of which are eliminated by this new assay. Additionally, this assay was designed to fit within the existing melt curve assay system that we and other laboratories use for the assessment of resistance in Aedes aegypti without the need for any protocol changes except for proper controls and amplification primers. The assay is currently being tested in a Florida study and will soon be implemented in Louisiana.
3. Gamma irradiation reduces survivorship, feeding behavior, and oviposition of female Aedes aegypti. Aedes aegypti is a prominent disease-vector mosquito that is difficult to control through traditional integrated vector management due to their cryptic peridomestic immature habitat and adult resting behavior, increasing resistance to pesticide formulations approved by U.S. Environmental Protection Agency, escalating deregistration of approved pesticides, and slow development of new effective chemical control measures. One novel method to control Ae. aegypti is the sterile insect technique (SIT) that leverages the mass release of irradiated (sterilized) males to overwhelm mate choice of natural populations of females. However, one potential liability of SIT is sex sorting errors of colony pupae prior to irradiation resulting in occasional release of females that may affect the palatability of the SIT program by the public and increase the number of Ae. aegypti females in the environment that could potentially bite humans and potentially become infected with and spread viruses such as dengue, chikungunya, or Zika. Scientists at Gainesville, Florida, conducted unique experiments to investigate impacts of ¿-radiation on behavior (bloodfeeding and oviposition) and physiology (survivorship) of female Ae. aegypti pupae reared with male pupae for an operational SIT program. Data revealed that a radiation dose =30 Gy – a dose sufficient to sterilize males while preserving their mate competitiveness – may substantially negatively impact development, bloodfeeding, and oviposition of female Ae. aegypti after being irradiated as pupae. Importantly, these findings could reduce concern for females incidentally released alongside irradiated males in an operational Ae. aegypti SIT control program, allowing for higher throughput production of sterilized males and providing valuable information for engagement of the stakeholder public.
4. Discovery of synergists for topical and spatial repellents that circumvent pesticide resistance mosquitoes. Pyrethroids are one of the most commonly used classes of insecticides, and their acids are usually considered to be biologically inactive. Resistance to pyrethroid insecticides is increasingly reducing the effectiveness of pesticides and repellents. ARS researchers at Gainesville, Florida, along with partners at the University of Florida discovered that acids of several pyrethroids had a significant synergistic spatial repellent activity that was greater than the topical repellent DEET, were often more active than the parent pyrethroids, and showed little cross resistance in a pyrethroid-resistant Puerto Rico strain of Aedes aegypti mosquitoes. Of greatest significance was the observation that the synergism of several repellent compounds increased protection of human arms from biting Aedes aegypti mosquitoes. Use of these synergists may increase bite protection for existing and novel compounds, including protection against resistant mosquitoes that can transmit diseases such as dengue, Zika, chikungunya and yellow fever.
5. Selection of six mosquito strains with sodium channel mutations. ARS researchers at Gainesville, Florida, and DoD collaborating scientists genetically selected for six strains of Ae. aegypti exhibiting combinations of 2 sodium channel mutations found in the wild that are common in pyrethroid resistant Ae. aegypti in the US. The F0 source was a wild-type collection, so all strains have a genetic background comparable to field mosquitoes and are therefore more useful for insecticide resistance studies than legacy Ae. aegypti colonies. All strains have been characterized for toxicologic and enzymatic response to common adulticides and have been used in aerial spray studies to test operational efficacy.
6. Treated military uniform efficacy study completed. ARS researchers at Gainesville, Florida, and DoD collaborating scientists completed and published a study (in press) clearly demonstrating that treated military uniform efficacy may be completely compromised by strongly pyrethroid resistant strains of Aedes aegypti when the resistance is primarily genetic. This study also showed that the protection provided by DEET based repellents was the same for both the resistant and susceptible strains.
7. Variation in larvicide efficacy against disease vector Aedes and Culex mosquitoes in urban environment. The Aedes aegypti mosquito is a key vector of prominent viruses including dengue and Zika and displays increasing resistance to pesticides targeting their adult stages, potentially favoring operational control programs that include larval control. However, mosquito control programs face challenges in accessing immature mosquito habitat behind urban and suburban structures when conducting truck mounted spray applications of larvicides from the street. Scientists at Gainesville, Florida, conducted the first known parallel trials of two commonly used larvicide formulations applied as a residual with a large ULV sprayer in a simulated urban environment. These trials targeted locations where immature Aedes aegypti mosquitoes could be found such as in discarded containers in front and back yards and in roof-top depressions where water could pool. The sprayer used was one specifically chosen by operational mosquito control programs to deliver larvicide into back yards in urban areas from the street. Results indicated both larvicide formulations could be effective immediately in the front of the house and on the roof, but with little impact on immature habitat behind buildings. These results indicate that current measures designed to overcome a key challenge in operational mosquito control targeting prominent disease vector mosquitoes may need further refinement to protect public health that could include specially formulated larvicide mixtures or modifications to spray equipment to place larvicides into back yards.
Review Publications
Yang, L., Richoux, G.M., Norris, E., Cuba, I., Jiang, S., Coquerel, Q., Linthicum, K., Bloomquist, J.R. 2020. Pyrethroid-derived acids and alcohols: bioactivity and synergistic effects on mosquito repellency and toxicity. Journal of Agricultural and Food Chemistry. https://doi.org/10.1021/acs.jafc.9b07979.
Trzebny, A., Slodkowicz-Kowalska, A., Becnel, J., Sanscrainte, N.D., Dabert, M. 2020. A new method of metabarcoding Microsporidia and their hosts reveals high levels of microsporidian infections in mosquitoes (Culicidae). Molecular Ecology Resources. 00:1-19. https://doi.org/10.1111/1755-0998.13205.
Pantoja-Sanchez, H., Vargas, J.F., Ruiz-Lopez, F., Rua-Uribe, G., Velez, V., Kline, D.L., Bernal, X.E. 2019. A new approach to improve acoustic trapping effectiveness for Aedes aegypti (Diptera: Culicidae). Journal of Medical Entomology. 44(2):216-222. https://doi.org/10.1111/jvec.12352.
Britch, S.C., Linthicum, K., Kline, D.L., Aldridge, R.L., Golden, F.V., Wittie, J., Henke, J., Hung, K., Gutierrez, A., Snelling, M., Lora, C. 2020. Transfluthrin spatial repellent on US military materials reduces Culex tarsalis incursion in a desert environment. Journal of the American Mosquito Control Association. 36(1):37-42. https://doi.org/10.2987/19-6894.1.
Degener, C.M., Geler, M., Kline, D.L., Urban, J., Willis, S., Ramirez, K., Cloherty, E.R., Gordon, S.W. 2019. Field trials to evaluate the effectiveness of the Biogents Sweetscent lure in combination with several commercial mosquito traps and to assess the effectiveness of ABiogents Mosquitaire trap with and without carbon dioxide. Journal of the Mosquito Control Association. 35 (1): 32-39, 2019.
Bibbs, C.S., Kline, J., Kline, D.L., Estaver, J., Strohschein, R., Allan, S.A., Kaufman, P.E., Xue, R., Batich, C.D. 2019. Olfactometric comparison of the volatile insecticide, Metofluthrin, through behavioral responses of Aedes albopictus (Diptera: Culicidae). Journal of Medical Entomology. 57(1):17–24. https://doi.org/10.1093/jme/tjz160.
Britch, S.C., Cilek, S.C., Lindroth, E.J., Aldridge, R.L., Golden, F.V., Weeston, J.R., Fajardo, J.D., Richardson, A.G., Blersch, J.S., Linthicum, K. 2020. Earth fill increases efficacy and longevity of ¿-cyhalothrin residual insecticide treatment of HESCO® blast wall geotextile. Journal of the American Mosquito Control Association. 67:36-50.
Aldridge, R.L., Britch, S.C., Linthicum, K., Golden, F.V., Dao, T.T., Rush, M.J., Holt, K., White, G., Gutierrez, A., Snelling, M. 2020. Pesticide misting system enhances residual pesticide treatment of HESCO geotextile. Journal of the American Mosquito Control Association. 36(1):43-46. https://doi.org/10.2987/19-6897.1.
Campbell, L.P., Reuman, D.C., Lutomiah, J., Peterson, A.T., Sang, R., Linthicum, K., Britch, S.C., Anyamba, A. 2019. Predicting abundances of Aedes mcintoshi, a primary Rift Valley fever virus mosquito vector. PLoS One. 14(12):e0226617. https://doi.org/10.1371/journal.pone.0226617.
Cilek, J.E., Aldridge, R.L., Britch, S.C., Fajardo, J.D., Linthicum, K., Richardson, A.G. 2020. Effectiveness of Aquatain AMF and cocobear larvicidal oil against Culex quinquefasciatus larvae and pupae in an organically enhanced aquatic habitat. Journal of the American Mosquito Control Association. 36(1):47-50. https://doi.org/10.2987/19-6862.1.
Demiray, H., Tabanca, N., Estep, A.S., Becnel, J.J., Dermirci, B. 2019. Chemical composition of the essential oil and n-hexane extract of Stachys tmolea subsp. tmolea Boiss., an endemic species of Turkey, and their mosquitocidal activity against dengue vector Aedes aegypti. Saudi Pharmaceutical Journal. 27(2019) 877–881. https://doi.org/10.1016/j.jsps.2019.05.009.
Aryaprema, V.S., Blore, K., Kline, J., Aldridge, R.L., Linthicum, K., Xue, R. 2020. Laboratory evaluation of boric acid sugar baits against irradiated Aedes aegypti. Journal of the Florida Mosquito Control Association. 67:76-79.
Cunningham, C.A., Aldridge, R.L., Kline, J., Bibbs, C.S., Linthicum, K., Xue, R. 2020. Sub-lethal effects of irradiation on the blood feeding of Aedes aegypti (Diptera: Culicidae). Journal of Vector Ecology. 45(1):140-141. https://doi.org/10.1111/jvec.12382.
Yang, L., Liu, Y., Richoux, G.M., Bernier, U.R., Linthicum, K., Bloomquist, J.R. 2019. Induction heating coil heating improves the efficiency of insect olfactory studies. Frontiers in Ecology and Evolution. 7:247. https://doi.org/10.3389/fevo.2019.00247.
Yang, L., Norris, E.J., Jiang, S., Bernier, U.R., Linthicum, K., Bloomquist, J.R. 2019. Reduced effectiveness of repellents in a pyrethroid-resistant strain of Aedes aegypti (Diptera: culicidae) and its correlation with olfactory sensitivity. Pest Management Science. https://doi.org/10.1002/ps.5562.
Yang, L., Agramonte, N., Linthicum, K., Bloomquist, J.R. 2020. A survey of chemoreceptive responses on different mosquito appendages. Journal of Medical Entomology. https://doi.org/10.1093/jme/tjaa154.
