Objective 1: Design and synthesize novel chemicals such as toxicants, repellents, and attractants that can be used to mitigate the impact of blood-feeding arthropods. Objective 2: Determine physiological and molecular mechanisms involved in the detection of attractants, repellents, and feeding deterrents by mosquitoes in order to facilitate discovery of novel behavior-modifying chemicals. Sub-objective 2.A: Characterize gustatory receptors (GRs) and other chemosensory genes in the major gustatory appendages of Aedes aegypti, localize their expression and relative abundance, and determine their function through heterologous expression studies. Sub-objective 2.B: Determine the specificity of gustatory receptor neurons (GRNs) expressing identified GRs with emphasis on detection of feeding stimulants and repellents, and their role in Ae. aegypti feeding and avoidance behavior. Objective 3: Develop improved surveillance and control techniques for bed bugs. Sub-objective 3.A: Identify and elucidate the role of chemicals involved in the behaviors of dispersal (repellency) and aggregation (attractancy), and develop new detection techniques. Sub-objective 3.B: Develop new chemical or biological control agents to reduce or eliminate bed bug infestations. Objective 4: Discover and develop new tools for the control of ticks affecting humans, and evaluate their effectiveness at a range of conditions associated with climate change. Sub-objective 4.A: Develop new tick repellents/formulations and characterize the physiological mechanisms involved in repellent detection by ticks. Sub-objective 4.B: Determine if certain abiotic and biotic factors affect the responses of deer ticks to repellents.
New toxicants, repellents and attractants will be synthesized using quantitative structure-activity relationship analyses. This component will also focus on the development of novel inhibitors of detoxifying enzymes that are found in insects. Candidate compounds obtained from existing chemical libraries and commercial sources will be screened for bioactivity against blood-sucking arthropods. Gustatory receptors and genes in the appendages of the yellow fever mosquito Aedes aegypti will be characterized. Molecular studies will also determine the specificity of gustatory receptor neurons with emphasis on feeding stimulants and repellents. Chemicals that attract and repel bed bugs will be identified, and their role elucidated. To develop new monitoring devices, behavioral studies will use a photographic tracking system to monitor bed bug responses to behavior-altering compounds. New chemical and biological control agents will also be developed under this objective to mitigate the impact of this blood-sucking pest. New tick repellents and formulations will be developed and the mechanism of repellent detection by ticks characterized. This will involve the optimization of an in vitro feeding system for ticks, as well as the use of electrophysiological techniques to characterize tick responses to repellents and antifeedants. The effect of pathogen infection status, temperature, humidity, and geographic origin of ticks will also be investigated with regard to repellents.
In mosquito control research, ARS scientists in Beltsville, Maryland, concluded large scale synthesis of the selected fast acting pyrethroids were developed on suitable matrices to enhance vapor pressure at ambient temperature. With the assistance of industrial collaborators preliminary toxicological evaluation was accomplished for five selected fast acting pyrethroids. In translational mosquito research, ARS scientists in Beltsville, Maryland, showed that the major mosquito vector of the Zika virus have cells on a structure located near the mouthparts that can detect the repellent found in catnip oil. Catnip oil could also be detected by specific taste cells on the mosquito’s mouthparts, which deterred feeding. Understanding of the mechanisms by which the major mosquito vector for Zika virus detects repellents and feeding deterrents provides nerve targets for development of chemicals aimed at disrupting orientation of the mosquito to human hosts, thereby decreasing mosquito bites. ARS scientists also used gene editing techniques to construct mutant mosquitoes lacking individual receptor genes likely involved in sensing repellents. These mutant mosquitoes will be useful in determining the role of individual genes in feeding behavior. In bed bug research, ARS scientists in Beltsville, Maryland, showed that the fumigation actions of certain essential oils are only marginally useful in controlling bed bugs. Only rosemary oil proved to be an effective fumigant when compared to a commercially-available fumigant. ARS scientists in Beltsville, Maryland, in collaboration with University of Maryland scientists also demonstrated that bed bug defensive secretions could attract adult bed bugs at low concentrations. This information will be useful to industry personnel that are attempting to design effective lures and monitors for detecting bed bugs. In tick research, ARS scientists in Beltsville, Maryland, obtained over 10 new essential oil samples from collaborators and determined their repellency and toxicity properties, using a vertical paper repellency and glass vial contact bioassay, respectively. Individual essential oils and mixtures of several promising essential oils were evaluated, and dose-repellency relationships determined; one particular formulation mixture was found to perform better and last longer than the commercially-available repellent DEET. ARS scientists in Beltsville, Maryland, also achieved full success in using an artificial membrane to feed the lone star tick, a vector of several important human diseases, and the system is being used to test several tick control product and a number of novel compounds as tick toxicants and chemical tick removing agents, as well as to study tick blood feeding physiology. In addition, ARS scientists in Beltsville, Maryland, tested ticks for their responses to DEET under varying temperature and humidity conditions in the laboratory. No clear patterns were identified that would allow a definitive determination on if and how temperature and humidity may affect ticks’ response to DEET. Further experiments are being planned to repeat the tests by using environmental chambers where temperature and humidity settings can be more-precisely controlled.
1. Bed bug defensive secretions can attract adult bed bugs. Detection of bed bugs and monitoring for their presence are an important first step in any control strategy aimed at controlling these blood-sucking insects, yet no current monitoring device has gained widespread use. Using a video tracking system, ARS scientists in Beltsville, Maryland, in conjunction with scientists at the University of Maryland, demonstrated that bed bugs produced chemicals normally thought of as defensive secretions that cause the dispersal of bed bugs will actually attract adult male and female bed bugs at lower amounts. This information will be useful for commercial organizations that wish to develop cost-effective, reliable means of monitoring and detecting bed bugs.
2. Control of mosquito disease vectors using novel and effective ‘attract and kill’ strategy. The use of chemical pesticides to control mosquito disease vectors has raised both environmental and human health concerns. By combining stable attractants with eco-friendly toxicants and biopesticides, ARS scientists in Beltsville, Maryland, have developed ‘attract and kill’ technologies for mosquito control that have consistently been shown to be effective in the field. This strategy reduces our reliance on synthetic pesticides, thereby reducing any associated public health risks. It also has the important added benefit of using long-lasting attractants, without the need to use carbon dioxide cylinders or dry-ice in the field to mimic the host. This information will be useful to those companies and individuals involved in mosquito control and prevention of transmission of mosquito-born pathogens.
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Li, A.Y., Perez De Leon, A.A., Linthicum, K., Britch, S.C., Bast, J.D., Debboum, M. 2015. Baseline susceptibility to pyrethroid and organophosphate insecticides in two old world sand fly species (diptera: psychodidae). Army Medical Department Journal. p. 3-9.
Donaldson, T.G., Perez De Leon, A.A., Li, A.Y., Castro-Arellano, I., Wozniak, E., Boyle, W.K., Hargrove, R., Wilder, H.K., Kim, H.J., Teel, P.D., Lopez, J.E. 2016. Assessment of the geographic distribution of Ornithodoros turicata (Argasidae): climate variation and host diversity. PLOS Neglected Tropical Diseases. 2:1-19. doi:10.1371/journal.pntd.0004383.
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Ulrich, K.R., Kramer, M.H., Feldlaufer, M.F. 2016. Ability of the bed bug (Hemiptera: Cimicidae) defensive secretions (E)-2-hexenal and (E)-2-octenal to attract adult bed bugs. Physiological Entomology. 41:103-110.
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Esteve-Gassent, M.D., Castro-Arellano, I., Feria-Arroyo, T.P., Patino, R., Li, A.Y., Medina, R.F., Perez De Leon, A.A., Rodriquez-Vivas, I. 2016. Translating ecology, physiology, biochemistry and molecular biology research to meet grand challenge of tick and tick-borne diseases in North America. Archives of Insect Biochemistry and Physiology. 92(1):38-64.