2013 Annual Report
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.
The focus of our research is to discover and develop new methods to protect people from blood-sucking arthropods that either transmit disease pathogens, or are a nuisance. Priority arthropods include mosquitoes, ticks, and the common bed bug. The mosquito research involves both a fundamental and applied approach. In an attempt to unravel the underlying basis of mosquito attraction to hosts and repellency to certain chemicals, ARS scientists in Beltsville, MD used molecular techniques to characterize a specific taste cell on the mouthparts of the yellow fever mosquito that is sensitive to a feeding deterrent, as well as to DEET and other insect repellents. Identification of these taste receptors may prove useful in designing new assays to discover new, more effective mosquito repellents. In other fundamental studies, ARS scientists in Beltsville, MD used behavioral and molecular approaches to show that the behavioral responses of the yellow fever mosquito to attractive odors released by a host are dependent upon the age of the mosquito. These results provide a better understanding of the most likely targets that can be exploited for chemical disruption of mosquito behavior. In applied mosquito research, scientists in Beltsville MD chemically-optimized a series of fast-acting insecticides, of their design, for the treatment of surfaces used by mosquitoes for resting. These scientists also identified chemicals from natural products that could play a role in the management of pesticide resistance, by stemming the development of resistance in mosquitoes. Tick research by ARS scientists at Beltsville in collaboration with other ARS units and industry has addressed objectives to develop new toxicants, attractants, and repellents. Natural products and synthetic compounds have been used in behavioral bioassays involving several problem tick species, including the lone star tick, the American dog tick, the brown dog tick, as well as the black-legged or deer tick. Those compounds exhibiting repellency have been compared to commercially-available DEET to determine if the tested compounds are more effective. An unexpected offshoot of these studies and has shown that different laboratory solvents used to dilute tick repellents, and usually considered inert, can affect the outcome of laboratory repellent assays. In bed bug research, chemicals developed by ARS scientists at Beltsville were shown to be more effective than certain commercially-available insecticides. Laboratory assays also demonstrated that treating bed bugs with other chemicals at concentrations suggested to control infestations were oftentimes insufficient. Depending on the concentration used, some bed bugs survived treatment, and those that did could subsequently feed.
Bed bug bioassays. Developing new chemicals to control bed bugs relies initially on laboratory testing, though field-collected strains are difficult to rear and maintain in the laboratory. Furthermore, laboratory testing is generally directed at all stages and sexes of the bed bug, though using adult females in a chemical assay reduces the number of bed bugs available for future testing, by eliminating the reproductive core of the colony. ARS researchers in Beltsville, MD completed a study demonstrating that adult male bed bugs could be used exclusively in laboratory bioassays, thereby preserving female bed bugs for colony purposes. The study also showed that bed bugs sickened by the chemical treatment (but not killed), can recover and blood-feed. This information impacts laboratories and industries that maintain bed bug colonies for testing purposes and should make it easier to develop new chemicals and strategies to mitigate bed bug infestations by insuring sufficient biological material for laboratory testing purposes.
Mosquito taste receptors. Mosquitoes serve as vectors for many human pathogens, which can cause diseases such as malaria, dengue, yellow fever and West Nile fever. Therefore, there is a need to develop effective repellents, which would reduce contacts between mosquitoes and their human or animal hosts. ARS researchers at Beltsville, MD discovered that a specific taste cell on the mouthparts of mosquitoes that is responsible for the feeding-deterrent effects of mosquito repellents. Successful characterization of these molecular receptors will facilitate their use as templates for discovery of new, more effective repellents. This information will ultimately benefit the American public and military by providing new means for individuals to protect themselves from blood-feeding mosquitoes and other arthropods.
Oh, J., Bowling, J., Carroll, J.F., Leininger, T.D., Demirci, B., Can Baser, K., Bernier, U.R., Hamann, M.T.2012. Natural product studies of U.S. endangered plants: volatile fraction of lindera melissifolia (lauraceae) repels mosquitoes and ticks. Bioresource Technology. 80:28-36.
Bohbot, J.D., Dickens, J.C. 2012. Selectivity of odorant receptors in insects. Frontiers in Cellular Neuroscience. 6:29.
Feldlaufer, M.F. 2013. Bed bug detection: Current technologies and future directions. American Journal of Tropical Medicine and Hygiene. 88(4):619-625.
Feldlaufer, M.F., Ulrich, K.R., Kramer, M.H. 2013. A laboratory study of sex- and stage-related mortality and morbidity in bed bugs (hemiptera: cimicidae) exposed to deltamethrin. Journal of Economic Entomology. 106(2):988-994.
Sanford, J.L., Shields, V.D., Dickens, J.C. 2013. Gustatory receptor neuron responds to DEET and other insect repellents in the yellow fever mosquito, aedes aegypti. Naturwissenschaften. 100(3):269-273.
Bohbot, J.D., Durand, N.F., Vinyard, B.T., Dickens, J.C. 2013. Functional development of the octenol response in aedes aegypti. Frontiers in Invertebrate Physiology. DOI: 10.3389/fphys.2013.00039.
Dickens, J.C. 2013. Mode of action of insect repellents. Journal of Pesticide Biochemistry and Physiology. DOI:10.1016/j.pestbp.2013.02.006