Detection and response to Haemaphysalis longicornis and Theileria orientalis Ikeda on a cow-calf farm in Tennessee (USA).

Abstract

Bovine theileriosis is a vector-borne disease poised to become one of the most economically significant diseases of cattle in the United States. The hemoparasite Theileria orientalis Ikeda genotype causes bovine theileriosis (Piroplasmida: Theileriidae), which is primarily transmitted by Haemaphysalis longicornis Neumann (Acari: Ixodidae) (longhorned tick, Asian longhorned tick). Since its initial detection in New Jersey in 2017, H. longicornis has rapidly spread to 24 states and Washington, DC, as of July 2025. Given the exotic and invasive nature of this vector and its unique biological characteristics, cattle producers face a lack of effective management guidelines. This study documents our first response to a T. orientalis Ikeda-positive herd in Maury County, Tennessee (USA). Before our arrival and detection of H. longicornis on the property, we advised the producer to maintain a closed herd, use on-animal chemical control, and reduce overgrown vegetation. Upon arrival, we identified sampling areas where cattle primarily resided or previously had been and targeted these areas using timed tick dragging methods, checking the drag for ticks every 10 meters for a mean of 352 min per visit (~6 h). Collections occurred once in July 2022 and every other week in 2023 (June-November). In total, 166 H. longicornis larvae and 45 nymphs were collected. Nymphs were screened for T. orientalis, and 4.5% (2/44) were positive for T. orientalis Ikeda a year after the herd was initially confirmed positive. This study contributes to the long-term goal of developing first response plans for farms facing H. longicornis infestations and bovine theileriosis infections, thereby limiting the spread of this tick and pathogen.