Project Number: 8042-32000-008-26-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 28, 2016
End Date: Dec 31, 2018
The project has three objectives: (1) to determine if pathogen infection changes behavioral response of the blacklegged tick to DEET and other major repellent compounds; (2) to investigate how pathogen infection may affect tick’s questing response at population level in environment; (3) to determine if ticks’ susceptibility to acaricides can be reduced or enhanced by pathogen infection status; and (4) to support specific objectives of the USDA’s Areawide Tick IPM Project through collaboration with CDC.
1. Evaluation of ticks’ response to DEET using a laboratory repellency bioassay technique. Nymphs and adult ticks will be collected, at their respective peak seasons, from various field locations and will be maintained in a laboratory incubator under proper temperature and humidity conditions prior to behavioral tests. A vertical filter paper repellency bioassay technique will be used to measure response of individual ticks to different concentrations of DEET. The minimum effective DEET concentration that repels each tick will be determined. Ticks will be individually preserved in 80% ethanol. 2. Detection of pathogen DNA in blacklegged ticks by TaqMan real-time PCR. Previously described primers and probes will be used to detect Borrelia burgdorferi and other tick-borne pathogens. TaqMan real-time PCR assays will be performed in two duplex formats with small reaction volumes using the Brilliant II qPCR Master Mix in a Stratagene MX3000P qPCR System. The first duplex detects tick DNA and B. burgdorferi, and the second duplex detects A. phagocytophilum and B. microti. In the first duplex, a probe that hybridizes to the 16S mtDNA gene in all hard tick species will be used as an internal control. 3. Effect of pathogen infection on susceptibility of field collected ticks to permethrin. A glass vial contact toxicity bioassay will be used to measure ticks’ susceptibility to permethrin. The baseline susceptibility will be established using laboratory reared blacklegged ticks. The permethrin concentration that kills 50% of the test subjects will be determined and used to screen field collected ticks. Subsets of 30 ticks will be randomly selected from a pool of field collected ticks. Three subsets will be used as control (solvent only treatment), and six to nine subsets will be exposed to permethrin treated vials. The live and dead ticks will be counted at the end of 24-h exposure time. Live ticks will be collected from each vial, preserved in ethanol, and subjected to PCR assays. B. burgdorferi infection rate will be determined. Sufficient numbers of blacklegged tick samples will also be obtained from Maryland and one of the Southern States, such as North Carolina or Florida. The ticks will be shipped to Dr. Xu at University of Massachusetts to perform above behavioral and molecular tests. Results will allow comparisons of behavioral responses and impact of pathogen infection on behavior in Northern and southern tick populations. 4. Support of USDA collaborative research with CDC in molecular detection of tick-borne pathogens in animal hosts and anti-tick vaccine evaluation. Through a sub-agreement with Center for Disease Control and Prevention in Fort Collins, Colorado, the University of Massachusetts researcher will help conduct molecular tests to detect tick-borne pathogens in tissue and blood samples collected from white footed mice from Maryland field locations by USDA researchers. The data will be analyzed to evaluate Lyme pathogen prevalence in the tick hosts that may impact pathogen prevalence in host-seeking ticks. The work at CDC also includes evaluation of novel anti-tick antigens using rabbit as the animal model.