Distribution and Habitat of Ixodes pacificus (Acari: Ixodidae) and Prevalence of Borrelia burgdorferi in Utah.

Ryan S. Davis
Ricardo A. Ramirez
J. Laine Anderson
Scott A. Bernhardt, Utah State University


Knowledge about the distribution and abundance of the western black-legged tick, Ixodes pacificus Cooley and Kohls, in Utah is limited. Recent concerns over tick-borne diseases in Utah, primarily Lyme disease, have reinvigorated the need to understand the distribution and habitats favored by this tick species. We surveyed 157 sites throughout Utah to examine the distribution, abundance, and habitat of I. pacificus. In total, 343 adult ticks were collected from 2011 to 2013. Specifically, 119 I. pacificus, 217 Dermacentor andersoni Stiles, six D. albipictus Packard, and one D. hunteri Bishopp were collected. Overall, tick abundance was relatively low in the areas evaluated in Utah. I. pacificus collections were limited to sites above 1700 m. Ninety-two percent of I. pacificus were captured in the Sheeprock Mountains in Tooele County. I. pacificus positive collection sites were characterized by Gambel oak (Quercus gambelii Nuttall), juniper (Juniperus spp. L.), big sagebrush (Artemisia tridentata Nuttall) and black sagebrush (A. novaNelson), and mixed grass habitat. All I. pacificus ticks were tested for the presence of Borrelia burgdorferi(Johnson, Schmid, Hyde, Steigerwalt, and Brenner, sensu stricto) using real-time PCR. All ticks tested negative for B. burgdorferi. The likelihood of encountering I. pacificus and acquiring Lyme disease in the areas evaluated in Utah is considerably low due to low tick abundance and limited distribution, as well as low prevalence (or absence) of B. burgdorferi in Utah.