The Carrier Rate of Colorado Tick Fever in the Rocky Mountain Wood Tick, Dermacentor andersoni

Abstract

The adult Rocky Mountain Wood Tick, Dermacentor andersoni, is capable of transmitting several diseases to humans, including Colorado Tick Fever (CTF). The abundance and distribution of the virus that causes this disease is largely unknown. Ticks were collected at multiple sites in Western Montana using drag sampling methods in order to test my hypothesis that the carrier rate of CTF was within the range of previous studies. Ticks were tested for CTF by extracting their viral RNA, converting this RNA to DNA and amplifying it using Reverse Transcriptase PCR (RT-PCR). The RT-PCR product was then run on an agarose gel to visualize the DNA. Eighteen and a half percent of ticks tested were carriers of the virus. The virus was heterogeneously distributed with certain sites having virus carrier rates as high as 56% and others as low as zero percent. Although the total percentage of ticks containing the virus is within the ranges of past studies, it is not known what additional factors might account for the uneven distribution observed. Additional data should be collected in the future to determine factors influencing the virus’ distribution. Data from this study and future studies can be used to generate a risk assessment map in order to decrease the risk of humans being bitten by a virus-carrying tick, and to better diagnose those who may be infected.