Case Report: Retrospective discovery of Theileria orientalis Ikeda in Haemaphysalis longicornis Neumann ticks on a cow-calf farm in Tennessee (US)

<i>Theileria orientalis</i> Ikeda is a protozoan parasite that has recently been detected in <i>Haemaphysalis longicornis</i> Neumann ticks and bovine serum samples in the United States (US). This parasite is known to cause theileriosis in bovine hosts and has negatively impacted the cattle industry worldwide. The transmission of this pathogen at the livestock-wildlife interface in the US is not fully understood. <i>Theileria orientalis</i> Ikeda was reported by producers on a cow-calf farm in eastern Tennessee. A retrospective analysis of field- and host-collected <i>H. longicornis</i> resulted in the detection of <i>T. orientalis</i> Ikeda in nymphal <i>H. longicornis</i> ticks collected from cattle (<i>Bos taurus</i>), domestic cats (<i>Felis catus</i>), raccoons (<i>Procyon lotor</i>), and Virginia opossums (<i>Didelphis virginiana</i>). Notably, the protozoan DNA was not found in the blood of these hosts. Multiple hosts (cattle, raccoons, Virginia opossums, and a domestic cat) contributed to the presence of <i>T. orientalis</i> Ikeda-infected <i>H. longicornis</i> ticks on the farm. Treating these hosts with acaricides could be important for reducing tick abundance and pathogen transmission. Additionally, biosecurity practices, such as changing gloves and syringes between handling bovine hosts, are important for preventing the accidental mechanical transmission of <i>Theileria</i> parasites.