Location: Mosquito and Fly Research2011 Annual Report
1a. Objectives (from AD-416)
1. Discover and evaluate new toxicants and biological control agents for control of biting Nematocera. 2. Develop new application methods for pesticides to biting Nematocera that minimize environmental exposure and that optimize lethal or repellent effect, including presentation on clothing, aerosol application in or outdoors, residual application, disinsection of aircraft, and delivery of spatially repellent compounds. 3. Conceive and test new methods of managing vector and pest populations through the use of behavior-altering chemicals, including repellents, attractants, and inhibitors. 4. Examine the parameters of behavioral bioassay methods that influence practical comparisons of personal protection products, with a view to determining those elements of commercial testing that influence reliability of results. 5. Determine chemical and other cues associated with regulation and orientation of specific behaviors by Aedes albopictus, Culex pipiens group species/hybrids, and other biting arthropods that can be applied to the solution of operational surveillance and control problems. 6. Discover and characterize environmental predictors of the distribution of mosquitoes in order to assess the risk of invasive species and pathogen transmission. Apply to the development of methods and techniques to accurately assess mosquito population density, to deploy vector surveillance systems, and to detect exotic invasive species.
1b. Approach (from AD-416)
1. High throughput bioassays will be used to screen candidate toxicants from libraries of synthetic compounds and natural products. Bacterial toxins, baculoviruses, and biorationals will be evaluated in new formulations in standard assays. Molecular methods (RNAi and dsRNA) will be used to identify targets for control and resistance management. Improved formulation and delivery of dsRNA will be developed to penetrate the mosquito cuticle. 2. Factors affecting measurement of bite protection by permethrin-treated clothing will be examined. Alternative repellents applied to military uniforms and improved binding of repellents to fabric will be researched, followed by laboratory validation of factory-treated fabric and semi-field studies. Aerosol applications of control compounds, using different formulations, equipment, techniques, and strategies will be explored. Existing and novel chemical compounds, formulations, equipment, impregnated materials, application techniques, and strategies for barrier applications will be evaluated under laboratory, semi-field and field conditions. Factors needed to achieve optimal control will be identified. Air curtains will be designed and evaluated in simulated aircraft fuselages. 3. Comparison of pathogen-infected and uninfected mosquito responses to behavior-altering chemicals will be examined. Baited commercial traps will be used as surrogates for human and livestock hosts. The manner in which compounds affect host-seeking behavior will be quantified. Catches in control and attractant-baited traps located near devices releasing spatial repellents or inhibitors will be compared. 4. The effect of mosquito fatigue on repellent protection time will be evaluated with female Aedes aegypti and a study comparing methods for measuring repellent efficacy will be conducted. Laboratory results of repellent efficacy will be compared to products tested in the semi-field environment. 5. Factors that result in positive resting site selection responses by adult mosquitoes, volatile chemical cues associated with mate location, and cues used for location and utilization of sugar and nectar sources will be determined. Plant-derived compounds that attract mosquitoes will be evaluated in the field. Factors that influence host-finding behavior based on host odors and olfactory cues will be used to enhance traps. Novel strategies for mosquito surveillance that utilize oviposition site cues will be devised. New chemical attractants will be identified and evaluated in the field using behavioral and chemical analyses. The response to toxicant exposure on arthropod behavior will be evaluated to improve toxicant impact. 6. Methods and techniques to assess mosquito population density will be developed. Environmental predictors of mosquito distribution will be characterized to provide improved strategies for assessment of mosquito populations. Discover ecologic and climatic factors to assess population densities of vector mosquitoes in the US and, using Rift Valley fever, evaluate the risk of exotic species and disease introduction into the U.S.
3. Progress Report
Biting Nematocera transmit pathogens that cause diseases such as West Nile virus, dengue, malaria, leishmaniasis and filariasis to humans and animals in urban, suburban, and rural areas and in agricultural, recreational, and military environments. This research project is focused on improving the control of biting Nematocera through a better understanding of their biology and the development of novel products, technologies, and control strategies. Research with gene silencing technology has led to the development of RNA interference (RNAi) strategies through the use of Highly Specific Pest Control (Hi-SPec) substances in combination with attractant sugar sources. This type of trapping system can be used as part of an integrated pest management control strategy to reduce disease risk to humans and animals. Results from larvicidal and adult screening with insecticides resulted in promising new compounds that may become alternative insecticides for mosquito and fly control. Current and new U.S. Army uniform materials were evaluated for their ability to prevent mosquito bites. The protection of U.S. military personnel from diseases transmitted by insect bites is critical to the success of our military missions. The bite protection of Fire-Resistant Army Combat Uniforms (FRACUs) treated with permethrin by factory-treatment was completed. The results of the studies with uniforms were used by the U.S. Army to award contracts to suppliers of these uniforms. The data generated for U.S. Marine Corps was submitted to the U.S. EPA for label registration of permethrin-treated uniforms. Historically, a control strategy for use against mosquitoes that transmit malaria in Africa has been through the treatment of the inside walls of dwellings with Indoor Residual Sprays (IRS). As an alternative to IRS, Durable Residual Wall Linings (DL) have been evaluated and found to produce 100% kill of mosquitoes, 8 months after initial usage. Ultra-Low Volume (ULV) tests of a sumithrin/prallethrin combination insecticide was found to be superior to other ULV insecticides for the control of mosquitoes and flies in Sub-Saharan Africa. Additionally, camouflage netting treated with bifenthrin significantly decreased mosquito and fly populations in areas where the netting was deployed. Laboratory tests indicated that the treated netting was still effective 18 months after the initial application. Novel spatial repellent appliqués that contained either nepetalactone or rosemary oil where shown to be effective at suppressing the ability of mosquitoes to find attractive odors.
1. Highly Specific Pest Control (Hi-SPeC). Mosquitoes transmit diseases that can lead to disease and death of millions of people and animals worldwide. HiSPeC substances are highly specific for target pests, such as mosquitoes, and do not affect other insects. This novel approach is based on the technology that allows for the specific silencing of genes critical to survival of the target pest. This technology uses double stranded RNA (dsRNA) and the process of RNA interference (RNAi) to selectively silence gene products (proteins) that debilitate the mosquito and prevent it from transmitting several disease agents. Because adult mosquitoes need sugar sources for survival, researchers at ARS Gainesville, FL, have developed HiSPEC dsRNA constructs. These highly specific compounds that knock-out the targeted protein in the mosquito's body have been successfully delivered to adult mosquitoes using sugar baited traps. Traps baited with sugar and Hi-SPeC substances kill or debilitate mosquitoes and can compliement current vector control strategies such as insecticide treated bednets (ITNs) and indoor residual spraying (IRS) programs to control important vectors of malaria and arboviruses to man and animals.
2. Transition to factory produced repellent-treated United States Army fire-resistant combat uniforms. Mosquitoes, ticks and sand flies are a threat to deployed military personnel because of the diseases transmitted when they bite. The diseases can result in substantial costs to U.S. taxpayers for medical treatment of infected personnel, lead to death of our U.S. military personnel, and lead to unsuccessful military operations during critical missions. As a means to reduce the disease risk to our deployed service personnel, their uniforms are treated with permethrin to repel insects from biting through the clothing. Researchers at the USDA Agricultural Research Service, Center for Medical, Agricultural, and Veterinary Entomology in Gainesville, FL, performed the bite protection studies that enabled the U.S. Army as it transitioned to stocking the Fire-Resistant Army Combat Uniforms (FRACUs) that have been treated once with permethrin. These factory-treated uniforms are designed to provide our soldiers with a reliable, high level of protection from mosquito, tick, and fly bites, over the lifetime of the uniform.
3. Durable residual wall lining for control of mosquitoes that transmit vector borne diseases. Mosquitoes infect humans with malaria, yellow fever, and West Nile fever. These pests may fly into houses and bite humans and other animals leading to a transmission of the disease pathogens. One approach to reducing the risk of disease is by using an insecticide-treated wall lining for control. The efficacy of insecticide-treated ZeroVector™ (Vestergaard Frandsen) Durable Lining (DL) was evaluated as an alternative to Indoor Residual Sprays (IRS) for indoor control of Anopheles mosquitoes and prevention of malaria. ZeroVector™, a thin, blue sheet of woven shade cloth impregnated with deltamethrin, was evaluated against 3 species of mosquitoes (Anopheles quadrimaculatus, Culex quinquefasciatus, and Aedes aegypti) under semi-field conditions (small huts). The studies were conducted at the USDA Center for Medical, Agricultural and Veterinary Entomology in Gainesville, FL. The World Health Organization cone bioassay touch test was used to evaluate mosquito knockdown and mortality caused by the insecticide-treated durable wall lining against 3 mosquito species. A second test method, which utilized 100 free-flying female mosquitoes of each species, was also used. During the first 9 months of the study, 100% mortality was observed with the cone test and there was approximately 90 percent mortality among the free-flying mosquitoes released in the huts. Both of these results reflected the capability of the treated wall lining to kill mosquitoes over a 9-month period.
4. Improved protection of deployed military personnel from mosquitoes and flies in Sub-Sahran Africa. Control of mosquitoes and flies that bite our deployed personnel is a critical component to the success of the U.S military operations. Currently, a significant number of our military operations are conducted in desert environments. One way to control these pests is by using chemical insecticides to kill the adults that carry disease pathogens. Thermal fog and Ultra-Low Volume (ULV) studies conducted in Kenya in disease endemic habitats demonstrated that both malathion and synergized prallethrin/sumithrin based products were highly efficacious in killing caged populations of adult sand flies. Wild sand fly populations were monitored using CO2-baited light traps and indicated effective population suppression or population displacement following ULV and thermal fog applications. Repeated trials revealed that thermal fog applications of sumithrin/prallethrin based pesticides were substantially more efficacious than similar ULV applications against sand flies.
5. Suppression of mosquitoes and flies using camouflage netting. Control of mosquitoes and flies is critical in areas where our U.S. military are deployed. These pests transmit diseases that impact mission success and can result in significant financial costs for medical treatment. One control strategy is to use the United States military desert radar-scattering ultra-lightweight camouflage netting system (DRSULCANS) material which is typically preset in the area of military operation. Experiments were conducted with the netting suspended around wood 10 ft by 10 ft by 6ft high open topped cubic frames in a hot semi-arid tropical environment in western Kenya. The material had been treated with bifenthrin prior to shipping to Kenya. Mosquito population sampling within and outside of treated and untreated netting perimeters and laboratory bioassays with mosquitoes on samples of cut camouflage netting material indicated significant reductions of mosquitoes and sand flies in field counts and lab assays for 18 months.
6. Semi-field evaluation of spatial repellent appliqués. Mosquitoes that transmit diseases are able to locate humans and animals for biting through the use of the chemical odors released by these hosts. A means of interrupting this host-finding process is through the use of control strategies that involve repellents. Researchers at the Agricultural Research Service, Center for Medical, Agricultural and Veterinary Entomology in Gainesville, FL, evaluated spatial repellent appliqués using mosquitoes in large outdoor screened cages containing military tents. Appliqués that contained either nepetalactone or rosemary oil reduced attractancy of the traps by less than 25%.
Xue, R., Muller, G.C., Kline, D.L., Barnard, D.R. 2011. Effect of application rate and persistence of boric acid sugar baits applied to plants control of Aedes albopictus. Journal of the American Mosquito Control Association. 27(1):56-60.