2011 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. Priority arthropod targets are mosquitoes, ticks, and the common bed bug.
ARS scientists in Beltsville, MD have identified and synthesized new, fast-acting insecticides that have been shown to be toxic to numerous types of mosquitoes of public health importance. These new compounds presumably induce their toxic effect based on their on their high vapor pressure, which allows them to vaporize quickly, resulting in toxicity to exposed mosquitoes in minutes. An invention disclosure has been filed, which will hopefully result in a new product to control insects of medical importance.
Fundamental research involving mosquito host attraction has characterized a receptor in the yellow fever mosquito for a host-produced attractant. ARS scientists in Beltsville MD have shown that mosquito receptors are quite specific to compounds involved in host attraction. This research has created a better understanding of odor reception in mosquitoes that may ultimately be used in the rational design of mosquito repellent compounds.
Natural product compounds supplied by collaborating ARS scientists and other partners have been evaluated by ARS scientists in Beltsville, MD for their efficacy in repelling a tick species of veterinary and medical importance. Repeated testing of individual ticks, showed how often ticks can be reused in behavioral tests and how a tick’s responses to a repellent may vary. A considerable effort has been directed at bioassays of tick attractants, which have been more difficult to characterize. Tick attractants could potentially be used in conjunction with toxicants, resulting in an “attract and kill” strategy that would contribute to an overall, tick management program.
Research with bed bugs has revolved around efficacy testing of proprietary compounds obtained from ARS chemists, and of compounds obtained from industry. Most compounds tested have proven ineffective in killing bed bugs, though several promising compounds are being further evaluated for immediate and residual activity. ARS scientists have also obtained several field infestations of bed bugs thought to be resistant to commercially-available pesticides, though further testing indicated only two of these strains were resistant at levels that make them useful for chemical screening purposes. However, rearing of these field-collected strains has proven to be difficult as these bugs seemingly lack feeding avidity, which results in decreased reproduction and lower numbers available for testing.
Mosquito attractant. Understanding the underlying mechanisms of mosquito attraction is a critical component in developing new compounds that alter mosquito behavior. Octenol is a compound found in human breath and sweat and is considered an important attractant component for many mosquitoes, though little was known about the specificity of the mosquito’s receptor for octenol and potential effects of repellents on its activity. ARS researchers in Beltsville, MD, demonstrated that the octenol receptor in a mosquito is sensitive to only one of two mirror image compounds comprising octenol; small changes in this molecule resulted in large decreases in responses elicited by the resulting analogs. For the first time, a known repellent, 2-undecanone, was shown to stimulate the octenol receptor, while other repellents, such as DEET, IR3535, and picaridin were inactive. These results contribute to a better understanding of fundamentals involved in mosquito attraction, and will ultimately contribute to the design of new repellents.
Bed bug compounds. The resurgence of bed bugs has led to the need for a better understanding of bed bug behavior in the hope that this will contribute to the design of more efficient lures and traps. While certain bed bug-produced chemicals have been shown to be involved with the behaviors of attraction and aggregation, little information exists on the specific identity of these chemicals. ARS scientists at Beltsville, MD, have identified 17 individual chemicals that were collected from male and female bed bugs. The identification of these bed bug-produced compounds will be useful to other researchers and industry scientists trying to understand bed bug behavior and design better traps for bed bug monitoring and control.
New mosquito and tick repellent. New, safer and more-effective repellent products are needed to mitigate the dangers and discomforts posed by biting arthropods such as mosquitoes and ticks. ARS scientists at Beltsville, MD, have discovered a new repellent from a commercially available natural product. Once commercially-developed, it is expected that this compound, also used as a commercial food ingredient, will be safe to use as a repellent, and offer consumers an additional repellent product.
Thanispong, K., Achee, N., Grieco, J., Chauhan, K.R., Bangs, M.J., Suwonkerd, W., Prabaripai, A., Tanasinchayakul, S., Chareonviriyaphap, T. 2010. A high throughput screening system for determining the three actions of insecticides against Aedes aegypti (Diptera: Culicidae) populations in Thailand. Journal of Medical Entomology. 47(5):833-841.
Weldon, P., Carroll, J.F., Kramer, M.H., Bedoukian, R., Coleman, R., Bernier, U.R. 2011. Anointing chemicals and ectoparasites: responses by ticks and mosquitoes to Citrus (Rutaceae) peel exudates and monoterpene constituents. Journal of Chemical Ecology. 37(4):348-359.
Feldlaufer, M.F., Loudon, C. 2011. Undesirable dispersal of eggs and early-stage nymphs of the bed bug Hemiptera: cimicidae) by static electricity and air currents. Journal of Entomological Science. 46(2):1-2.
Bohbot, J.D., Dickens, J.C. 2010. Insect Repellents: Modulators of mosquito odorant receptor activity. PLoS One. 5(8):e12138.
Bohbot, J.D., Fu, L., Le, T.N., Chauhan, K.R., Cantrell, C.L., Dickens, J.C. 2011. Multiple activities of insect repellents on odorant receptors in mosquitoes. Medical and Veterinary Entomology. dx.doi.org/10.1111/j.1365-2915.2011.00949.x.
Grant, A.J., Dickens, J.C. 2011. Functional characterization of the octenol receptor neuron on the maxillary palps of the yellow fever mosquito, Aedes aegypti. PLoS One. 6(6):e21785.