Climatic Factors Limiting the Distribution of Dermacentor andersoni in Montana’s Rocky Mountain Region

Abstract

The Rocky Mountain Wood tick, Dermacentor andersoni, serves as the primary vector for the Colorado tick fever virus in Montana’s Rocky Mountain region. This disease presents symptoms such as fever, headaches, and myalgia; and generally lasts for approximately three weeks. Factors affecting the distribution of D. andersoni in Montana are not well known, limiting our ability to locate areas endemic to the CTF virus. To determine if various climatic factors influenced the distribution of D. andersoni Montana’s Rocky Mountain region, tick samples from Western Montana were collected and relative tick abundance was tested for association with six different climatic variables using ANOVA. CTF infection rate was also measured at each sampled site through RTPCR. I hypothesized that increasing moisture content will decrease the relative abundance of D. andersoni ticks. I also hypothesized that the infection rate would fall within the range of 10-15% in accordance with previous findings. The results of this study indicate that soil temperature, precipitation, and average annual air temperature may influence the distribution of D. andersoni in Montana’s Rocky Mountain Region. Elevated soil temperature and precipitation correlated with high relative tick abundance, while decreased average air temperature correlated with high relative tick abundance. The results also show an overall CTF infection rate of 1.05% for sampled sites.