Anaplasma marginale is the causative agent for bovine anaplasmosis (BA) and Ehrlichia ruminantium is the causative agent for heartwater, 2 devastating diseases of cattle. BA is common in the United States and frequently reported in western Tennessee cattle; however, cases of heartwater are not yet established in the continental United States. Because both pathogens are transmitted via the bites of infected ticks, the objective of this study was to survey cattle and pastures for ticks and for each pathogen. University of Tennessee AgResearch has 7 research and education centers (REC) located throughout the state at which they manage cattle. Ticks were collected from selected cattle (every fourth to sixth animal) and pastures (via dragging) associated with the herd from each REC during the summer of 2013. A total of 512 ticks were collected from cattle (n = 386) and pastures (n = 126) and were PCR-screened for Anaplasma and Ehrlichia using genus-specific primers. Collections consisted of 398 (77.7%) Amblyomma americanum, 84 (16.4%) Amblyomma maculatum, and 30 (5.9%) Dermacentor variabilis. Ticks were not recovered from pastures or cattle east of the Tennessee Plateau. The North American vectors for An. marginale and E. ruminantium were identified (D. variabilis and A. maculatum, respectively), but neither pathogen was recovered. A large proportion of ticks were collected from cattle and, of these, a majority were attached to their host (compared to questing on their host or engorged on the host). Four A. americanum were positive for Ehrlichia spp. (Ehrlichia ewingii, Ehrlichia chaffeensis, and Panola Mountain Ehrlichia), all in western Tennessee. With the identification of a few Ehrlichia infections in cattle-associated ticks and current A. marginale rates in Tennessee beef cattle nearing 11%, additional research is needed to establish baseline tick, Anaplasma, and Ehrlichia data for future management studies.
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Vol. 102 • No. 1