Project Number: 8042-32000-012-025-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 22, 2023
End Date: Sep 21, 2025
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) evaluate efficacy of promising compounds against ticks under semi-field and field conditions.
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 a commercial source. Wild ticks will also be collected from field locations in Maryland for comparative studies and semi-field trials. (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) Semi-field and field trials The most promising chemical compounds identified from laboratory bioassays will be further tested as acaricides or tick repellents under a semi-field condition. Work will be done at a wooded area at the South Farm at the Beltsville Agricultural Research Center. Field plots (enclosures) will be designed and treated with test compounds before or after a known number of ticks are released to the enclosures. Ticks will be recovered to determine tick mortality or avoidance at different time after treatment. If the results from the semi-field tests are convincing, we will repeat the work at backyards of selected residential properties with known high numbers of naturally occurring ticks in Howard County, MD. 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.