Location: Mosquito and Fly Research2010 Annual Report
1a. Objectives (from AD-416)
Objective 1: Discover and evaluate new toxicants and biological control agents for control of biting Nematocera. • Sub-objective 1.A. Discover new adulticides and larvicides for mosquitoes. (Becnel, Bernier, Clark, Linthicum) • Sub-objective 1.B. Develop RNAi molecules for control of mosquitoes. (Becnel) Objective 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. • Sub-objective 2.A. Determine factors that affect and enhance protection from insect bites through military and civilian repellent-treated clothing. (Bernier) • Sub-objective 2.B. Examine factors that contribute to the efficacy of aerosol application of pesticides in various environments, with emphasis upon dry arid climates. (Linthicum) • Sub-objective 2.C. Examine factors that contribute to the efficacy of residual pesticide application, including use of insecticides in impregnated materials and as barrier sprays for mosquitoes and other biting flies. (Kline, Linthicum, Bernier, Hogsette, Clark, Allan) • Sub-objective 2.D. Develop and evaluate approaches to disinsection of aircraft. (Hogsette, Clark, Linthicum) Objective 3: Conceive and test new methods of managing vector and pest populations through the use of behavior-altering chemicals, including repellents, attractants, and inhibitors. • Sub-objective 3.A. Conceive and test the efficacy of attractants, inhibitors and repellents on the control of Nematocera. (Allan, Bernier, Barnard, Clark, Kline, Hogsette, Linthicum) • Sub-objective 3.B. Develop and examine a “push-pull” system for biting fly control through use of a combination of behavior-modifying chemicals, such as repellents and inhibitors, in trapping systems baited with attractants. (Bernier, Kline, Allan, Hogsette, Barnard) Objective 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. (Barnard, Bernier)
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, including RNAi and dsRNA, will be used to identify new targets for control and resistance management by challenging mosquitoes with pesticides, microbial organisms, or other stressors to identify critical mosquito genes/proteins. Improved delivery/formulation of dsRNA to effectively penetrate the mosquito cuticle will be developed. 2. Factors affecting measurement of bite protection provided by permethrin-treated clothing will be examined. Alternative repellents applied to military uniforms will be studied. Improved binding of repellents into the fabric will be researched, followed by laboratory validation of the factory-treated fabric and semi-field studies. Aerosol application of control compounds, formulations, equipment, application techniques, and strategies as Ultra-Low Volume (ULV) insecticides will be explored. Studies will extend from laboratory-based with colonized insects to experimental field plots. 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. Parameters (i.e., state of target insect, barrier composition and environmental factors) will be examined to identify the critical factors to achieve optimal control efficacy. Semi-field tests will involve colonized insects while field trials with GIS will involve natural populations. Air curtains will be designed and evaluated in simulated aircraft fuselage modules. 3. Resource-finding behaviors will be studied to devise a toxic bait (attract-and-kill) for testing in the laboratory, semi-field, and field. Comparison of pathogen-infected to uninfected mosquito responses to behavior-altering chemicals, including repellents, inhibitors, and toxicants, will be examined. Commercial traps, identical in placement, physical characteristics, and baited with attractants will be used as human/livestock surrogates. The manner in which compounds affect host-seeking behavior will be measured by quantifiable responses (i.e., percent repellency or duration of repellency, knockdown, mortality, attraction or inhibition percentage) and insect physiological responses (i.e., GC-EAD), and by qualitative behavioral responses (i.e., flight pattern observed by video recording). Using a screened cage, catches in attractant-baited traps will be compared to catches in control traps located near devices releasing spatial repellents or inhibitors. The experimental design in the large cages will be adapted to evaluate this concept in the field. 4. The effect of mosquito fatigue on repellent protection time (CPT) will be evaluated using female Aedes aegypti. A study comparing different methods for measuring repellent efficacy will be conducted. Laboratory results of repellent efficacy will be compared to performance of products tested in the semi-field environment.
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, rural, 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 showed that RNA interference (RNAi) can be transferred through the insect cuticle. This further advances the novel field of molecular pesticides. Results from larvicidal and adult screening with insecticides resulted in two promising models for the development of novel insecticides to be tested against the house fly and yellow fever mosquito. The impact on genes by viruses that infect mosquito larvae have been studied and continuing work is being done to identify the mechanism by which the virus works on the mosquito. “Bite protection” evaluation of permethrin-treated Fire-Resistant Army Combat Uniforms (FRACUs) indicated that factory-treatment of this uniform resulted in a uniform that gave excellent protection against mosquitoes throughout its expected lifetime. The results of the studies with uniforms were used by the U.S. Army to award contracts to suppliers of these uniforms. The protocol used for generation of this data is now being accepted by the U.S. Environmental Protection Agency as the appropriate way to evaluate the protection from insects afforded by permethrin-treated clothing. Demonstrated efficacy of insecticide-treated barrier treatments on native vegetation and artificial substrates in desert, tropical and subtropical habitats for controlling mosquitoes and sand flies. Evaluated four spatial repellents against mosquitoes and flies to determine if the systems protect individuals in tents or other similar enclosed dwellings. It was discovered that a certain spatial repellent may work well with one insect species, but not work as well against others. Tested efficacy of net doors rather than air curtains as a means to prevent entry of insects into the passenger cabin of commercial aircraft. Novel synthetic carboxamide repellents were predicted, designed, and tested against malaria-transmitting mosquito species An. gambiae and An. quadrimaculatus. Two of these novel repellents performed as well as the standard repellent N,N-diethyl-3-methylbenzamide (DEET). Identified two carboxamides that were as potent as DEET against these species. In July, 2010, the World Health Organization Pesticide Evaluation Scheme (WHOPES) held its 50th Anniversary conference and recognized a number of institutions that have made significant contributions to WHOPES throughout the past 50 years. The contributions of the Center for Medical, Agricultural, and Veterinary Entomology (CMAVE) were recognized by WHOPES by the presentation of a plaque to the CMAVE Center Director and invitations for three CMAVE researchers to give oral presentations in Geneva, Switzerland.
Clark, G.G. 2008. Dengue and Dengue Hemorrhagic Fever in Northeastern Mexico and South Texas: Do they really respect the border? American Society of Tropical Medicine and Hygiene. 78(3):361-362.