Location: Invasive Insect Biocontrol & Behavior Laboratory
Project Number: 8042-32000-012-025-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 22, 2023
End Date: Sep 30, 2027
Objective:
The objectives of the proposed research are to (1) determine the oral, topical, and contact toxicity of various novel experimental chemical compounds against three major tick species of medical and veterinary importance under laboratory conditions; (2) elucidate the mode of action of those compounds by examining the behavioral and physiological responses of ticks as result of exposure to those compounds at lethal and sub-lethal concentrations; and (3) develop and validate a new mouse bait formulation for elimination of tick-borne pathogens from reservoir hosts and ticks.
Approach:
Novel synthetic and natural test compounds will be obtained by the University of Florida cooperator and ARS scientist. For laboratory bioassays and physiological experiments, nymphs and adults of the blacklegged tick, the lone star tick, and the American dog tick will be obtained from commercial sources.
(1) Laboratory toxicity and repellency bioassays. Topical treatment of ticks with test compounds will be done by using a repeating dispenser. A volume of test solution will be applied, and acetone alone treatment will serve as the negative control. Surface contact assay will be performed by treating glass scintillation vials with an acaricide solution in acetone. Mortality will be determined 24-h post-treatment. Oral toxicity of test compounds will be determined using a capillary feeding method. In vivo screening signs of intoxication will be noted as this may be related to the potential modes of action that will be examined further in mode of action study.
(2) Mode of action studies. The tick membrane feeding system will be used to evaluate effects of test compounds on tick attachment, detachment, blood feeding/salivation by combining the membrane feeding system with the EPG feeding monitor. Effects of test compounds on tick’s nervous system will be evaluated by recording neuronal activities from an isolated ganglion preparation in a petri dish. The effects of the test compound will be compared with those elucidated by well-defined pharmacological agents. The modes of action study will focus on females of the blacklegged tick. Females of the American dog tick or the lone star tick can also be used if its bigger size makes the neurophysiological recording easier.
(3) Develop and evaluate medicated novel mouse bait for elimination of tick-borne pathogens from white-footed mice and ticks feeding on mice. The pathogen-killing compounds and associated biological materials will be provided by ARS scientist for development of novel medicated mouse bait formulations. White-footed mice purchased from commercial sources will be fed with formulated baits to determine mouse serum concentration of the test compound in relation to its concentrations in bait formulations. Mice infected with tick-borne pathogens will subject to feeding with medicated bait to determine pharmacokinetics of the test compound in mice, its efficacy in eliminating the pathogen from mice, as well as its effects on blood-feeding and survival of ticks feeding on mice.
(4) Project assessment, data analysis, and report. The progress of this project will be assessed on a regular basis to identify deficiencies and to solve any issues. This will be achieved through regular email and phone calls between the USDA scientist and the cooperator and site visits. Data will be reviewed/analyzed jointly, published jointly in journals, or used for joint patent application(s). The cooperator will prepare and submit a written report to the USDA scientist at the end of each project year.
