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United States Department of Agriculture

Agricultural Research Service

Research Project: EVALUATION OF REPELLENTS AND CONTROL COMPOUNDS IN MOSQUITOES, SAND FLIES, AND TICKS INFECTED WITH MILITARILY IMPORTANT HUMAN PATHOGENS

Location: Mosquito and Fly Research Unit

Project Number: 6615-32000-045-01
Project Type: Specific Cooperative Agreement

Start Date: Mar 21, 2007
End Date: Mar 20, 2012

Objective:
To determine if virus-infected arthropods are repelled by new mosquito repellents and killed by new control products.

Approach:
Hypothesis: Insect vectors infected with human pathogens react differently to insect repellents, inhibitors and insecticides than vectors that are not infected. Experimental Design: Initially adult females mosquitoes will be inoculated initially intrathoracically with West Nile virus (Aedes albopictus), RVFV (Culex pipiens), or Venezuelan Equine Encephalomyelitis virus (Ae. taeniorhynchus). Female mosquitoes from each species will also be inoculated with diluent to serve as negative controls. In addition, non-inoculated control mosquitoes will be tested in the behavioral assays as a control for the inoculation procedure. Inoculated mosquitoes and non-inoculated mosquitoes will be held for 7-10 days at 26 degrees C before being used in the behavioral assays. Behavioral assays will be conducted in several bioassay systems such as (1) olfactometers, (2) Petri dish contact insecticide assays, and (3) the HITSS chambers by Grieco et al. Novel compounds to be tested in the behavioral assays are proprietary repellents, inhibitors, and insecticides being evaluated at CMAVE. Appropriate concentrations in ethanol will be made according to instructions provided for each compound. Compounds will be compared with untreated controls and to other known repellents or toxicants. The number of mosquitoes responding to different treatments in a standard period of time will be counted, and the percent changes in response between the tested compound and the standard control will be analyzed. Future behavioral assays will be developed for evaluation non-mosquito vectors infected with relevant human pathogens. Military Relevance: The United States military relies upon insect repellents and insecticides to prevent or reduce the transmission of arthropod-borne diseases such as malaria, dengue, and leishmaniasis. However, arboviral infections are neurotrophic in many organisms, to include their insect vectors, and mosquitoes infected with the dengue viruses and Rift Valley fever virus (RVFV), and other viruses, have altered feeding behavior as compared to their uninfected cage mates. Although insect repellents inhibit mosquito biting when used appropriately, it is known that as they wear off, they can become attractants. Therefore, it is possible that while repellents may protect a soldier from mosquito bites, it may protect them only from bites from uninfected mosquitoes and not fully protect them from the bites of virus or other pathogen-infected mosquitoes and sand flies. The impact of arbovirus and other pathogen infection on the efficacy of insecticides to knock down and kill arthropods is not known but this needs to be elucidated to assure protection for deployed troops.

Last Modified: 4/18/2014
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