Location: Invasive Insect Biocontrol & Behavior Laboratory2019 Annual Report
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.
This is the final report for Project 8042-32000-008-00D, which terminates on 11/04/2019. Over the five-year course of this project, progress was made on all objectives and subobjectives, including research with mosquitoes, bed bugs and ticks, despite critical vacancies (one scientist retired and one scientist resigned in 2018). The objectives and subobjectives in this Project - to mitigate the impact of biting arthropods - support National Program 104 (Veterinary, Medical, and Urban Entomology) and fall within Component 1 (Medical Entomology for the Public and the Military) of this National Program. Specifically, the objectives and subobjectives will provide important scientific information to protect animals, humans, and property from the negative effects of pests and infectious diseases. A brief synopsis of the progress would include mosquito control research (Objective 1), where an ARS scientist in Beltsville, Maryland, developed dose-response relationship for fast-acting insecticides, streamlined the synthesis of these fast-acting insecticides, identified novel mosquito toxicants, developed a carbon-dioxide generator that does not rely upon dry ice to trap mosquitoes, and conducted mosquito surveillance using traps designed to collect egg-laying female mosquitoes. In translational mosquito research (Objective 2), ARS scientists in Beltsville, Maryland, showed that nerve cells located on mosquito mouthparts could detect repellents such as DEET, and that other “taste” organs were found on mosquito wings. In bed bug research (Objective 3), an ARS scientist in Beltsville, Maryland, in collaboration with a University of Maryland graduate student determined that a particular insect-killing fungus was not particularly suitable to kill bed bugs. The ARS scientist also determined that the two major defensive secretions are what canines trained to detect bed bugs alert on, and in collaboration with the University of Maryland graduate student determined that bed bug defensive secretions would not only repel bed bugs at high concentrations, but would also attract bed bugs at low concentrations. The ARS scientist also demonstrated that certain essential plant oils are only marginally effective in controlling bed bugs. In tick research (Objective 4), ARS scientists in Beltsville, Maryland, determined that temperature and humidity affect a tick’s response to repellents, refined an artificial membrane to feed certain ticks in the laboratory, which paved the way for testing repellents without the use of humans or laboratory animals, and discovered that ant-derived natural products that were more effective than commercially-available DEET in repelling ticks. In FY2019, despite critical vacancies, progress was made on most objectives and their subobjectives in the Project Plan “Prevention of Arthropod Bites”. However, mosquito control research thrust (Objective 1) was essentially ended when the scientist conducting this research resigned. In translational mosquito research (Objective 2), the ARS scientist in Beltsville, Maryland, retired, also effectively ending this thrust of research. In bed bug research (Objective 3), ARS scientists in Beltsville, Maryland, demonstrated that several potential fumigants were effective in controlling both susceptible and chemically-resistant bed bug strains. These fumigants were considered “green insecticides” and controlled other, agriculturally-important insect pest species. In tick research (Objective 4), ARS scientists in Beltsville, Maryland, interacted with local, County, and State personnel in an area-wide pest management project developed to reduce the incidence of Lyme disease. In Howard Co. Maryland, rodent and white-tailed deer were trapped and collared to determine their movement and any ticks either removed from these animals, or collected by other means, were identified and any pathogens these ticks harbored were also identified. A broader picture of animal movement and tick/pathogen burden is hoped to be determined in this targeted area. In FY15, FY16 and FY17, all milestones were either “Fully Met” or “Substantially Met” except for a single milestone that no longer applied. In FY18, all milestones were met that did not include the retired SY. In FY19, all milestones were either “Fully Met” or “Substantially Met” that did not involve critical vacancies. The new Project slated for November of 2019, will concentrate on ticks, since they transmit human disease, thereby exposing farmers and farm workers to tick-borne pathogens, and agritourism, by exposing the public that choose to “pick their own” crops to tick-transmitted pathogens.
1. Volatile identified from bed bug eggs. New strategies to detect bed bugs are always in demand for both the public and companies involved in detecting these blood-sucking insect pests. Canines trained to detect bed bugs have been used for about a decade and ARS scientists in Beltsville, Maryland, identified the compounds produced by bed bug nymphs and adults that alert the trained dog to their presence. A study was undertaken to determine if the chemical compound in bed bug eggs was similar or identical than the chemical produced by nymphs and adults. Surprisingly, the chemical identified that emanated from bed bug eggs was different. Furthermore, neither of the compounds produced by nymphal and adult bed bugs could be detected in the egg samples. This information will be useful to industry personnel that are attempting to develop new detection methods for bed bugs.
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