1a. Objectives (from AD-416)
Objective 1: Develop new toxicants and application methods (e.g., attract-and-kill formulations) that provide novel modes of action or that have other properties desirable for efficacy, safety, and commercialization. Objective 2: Develop new repellent active ingredients and combinations that provide protection and product potential. Objective 3: Determine the fine scale elements of mosquito behaviors (e.g., host-seeking) and associate them with particular chemicals (agonists and antagonists) and physiological detection mechanisms, in order to develop novel behavior-altering chemicals. Objective 4: Develop and refine bioassay methodologies for blood-sucking arthropods that can serve as standards for EPA labeling of toxicant and repellent compounds.
1b. Approach (from AD-416)
Applied research will use the expertise of entomologists and a synthetic organic chemist to produce, develop and evaluate new toxicant and repellent products effective against blood-sucking arthropods. Fundamental research will elucidate the underlying mechanisms involved in mosquito attractancy and repellency, thereby leading to the discovery of even newer classes of chemicals that alter arthropod behavior. Consistent with these efforts, bioassays will be developed and refined that can be used by the research community and industry for discovery, product development and federal registration purposes.
3. Progress Report
The focus of our research is to discover and develop new methods to protect people from biting arthropods. Priority arthropods targets are mosquitoes, ticks, and the common bed bug. Fundamental research involving mosquito host attraction demonstrated that the specific chemical structure of a key attractant is critical in the yellow fever mosquito’s ability to detect mammalian hosts. This research contributes to a better understanding of the elements that affect mosquito attraction to a vertebrate host and will hopefully lead to novel methods of mosquito control. Natural product and synthetic compounds supplied by collaborating ARS scientists have been evaluated for their efficacy in either repelling ticks or modifying tick behavior. Several essential oils as well as compounds structurally-similar to DEET showed repellent activity against the lone star tick, a vector of human ehrlichiosis. Repellent bioassays are being modified and refined in an attempt to harmonize assays aimed at evaluating new tick repellents. Data from six different in vitro bioassays utilizing lone star ticks exposed to the same range of concentrations of the repellent DEET are currently being analyzed. Research with bed bugs has revolved around efficacy testing of proprietary compounds from ARS chemists and compounds obtained from industry, and comparing the toxicity of these new compounds to the toxicity of known insecticides such as deltamethrin and chlorfenapyr. Refinement of rearing and maintenance protocols have allowed for the production of sufficient biological material for efficacy testing. ARS scientists are attempting to obtain field strains of bed bugs that are resistant to commercially-available pesticides to include in efficacy testing.
1. Mosquito host-seeking. Topical repellents applied to the skin are widely used to prevent mosquitoes from biting, and there is a need to develop newer, more effective methods to protect humans from mosquitoes. The molecular mode of action of insect repellents has only recently been studied, yielding seemingly contradictory theories on how they work. ARS researchers at Beltsville, MD showed that insect repellents may differentially activate odorant receptors in the absence of key odorants or inhibit responses of odorant receptors to key odorants when these odorants are present. The research demonstrates that repellents can have positive and negative activities acting on different sites of the odorant receptor complex, thus bringing concordance to conflicting models for their mode of action. A better understanding of the elements that affect mosquito host-seeking such as attraction and inhibition will lead to the development of novel methods to control these blood-sucking insects.
2. Fast acting pyrethroids: The accomplishment concerns identification and utilization of new fast acting insecticides in public health. Interesting feature revealed for these candidate pyrethroids was susceptibility to numerous resistance species of mosquitoes. An invention disclosure for patent application, ‘Improved repellent-treatment clothing system for prevention of art’, has been applied for. We believe that these compounds induce desirable toxic effect to vectors in minutes with high vapor pressure.
Pound, J.M., Miller, J.A., George, J.E., Fish, D., Carroll, J.F., Schulze, T.R., Daniels, T.J., Falco, R.C., Stafford III, K.C., Mather, T.N. 2009. The United States Department of Agriculture's northeast area-wide tick control project - summary and conclusions. Vector-Borne and Zoonotic Diseases. 9(4):439-447.