March 2026
Update on Theileria Testing in Cattle
By Gregg A. Hanzlicek, DVM, PhD, PAS
The graph below indicates the number of Theileria PCR tests completed in the KVDL and the percentage of positives being reported.
We have communicated with almost 200 owners and or veterinarians concerning field cases. Very few reports of major adult cow issues have been received. The most severe cases (high morbidity and mortality) cases continue to involve weaned beef calves experiencing BRD that are also T. orientalis ikeda positive.
This does indicate a POSSIBLE association between Theileria and respiratory disease (or calf health), but this association has not been proven to date. Certianly no causation has been established.
