Comparison of Capture Methods and Infection Rates for the Tick, Dermacentor andersoni, in Montana

Abstract

Montana is home to the tick Dermacentor andersoni which serves as a vector for Colorado tick fever. It is important to study ticks in the field to improve capture rates for the purpose of testing infection rates. To determine the most effective way to capture ticks, four separate capturing methods were assembled in two tick prevalent locations. These methods include AAAP pheromones, CO2, drag netting, and AAAP in combination with CO2. I hypothesized that the combination of AAAP and CO2 would yield the best capture results. I implemented a mark-recapture study using fluorescent powder and hypothesized that CO2 and pheromones combined would provide the best population estimates. My findings indicate that drag net sampling and CO2 alone were the best tick attractants which could be due to pheromone amounts high enough to repel ticks rather than attract them. CO2 and drag netting had similar efficacy, whereas AAAP attracted no ticks throughout all trials. I developed an RT-PCR protocol to detect the presence of Colorado tick fever in D. andersoni and hypothesized that infection rates would be within the range of 10-25%. At Woodlake Campground and Dearborn the infection rate of Colorado tick fever was 12%. The infection rate at Beaver Creek drainage was 10%. My results suggest that drag netting, perhaps combined with CO2 , lead to higher capture rates and the most effective means of estimating population density. Also, my results show that the infection rate of ticks was within 10-12% at three sites in Lewis and Clark County.