University of Missouri Director of Veterinary Extension Craig Payne urges cattle producers to watch for signs of disease associated with Theileria orientalis, a protozoal organism recently detected in Missouri.

The organism, which primarily affects cattle and is spread by the invasive Asian longhorned tick, infects red blood cells. The immune system attacks the infected cells, resulting in anemia.

First diagnosed in a cow-calf herd in 2017 in Virginia, the disease was detected in June 2023 in Missouri’s Howell County. By the end of June 2024, 10 counties reported cattle testing positive, and as of October, that number is up to 48.

With mild infections, cattle may show elevated temperature, depression and pale mucous membranes. With severe infections, they can show severe depression, and

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