Confirmed cases of Asian Longhorned Tick and Theileria orientalis

Theileria orientalis is a tickborne parasite that causes infectious anemia in cattle. The disease is transmitted by ticks, primarily the Asian longhorned tick, first recognized in the U.S. in 2017 and identified in Missouri in July 2021.

The Asian longhorned tick is known to infest a wide range of species, including livestock, dogs, cats and North American wildlife species. If too many ticks attach to one animal, the loss of blood can kill the animal.

Clinical signs include weakness, reluctance to walk and abortion. T. orientalis infections have been reported to cause mortality in up to 5% of infected cattle. Pregnant heifers and calves are particularly susceptible to the infection. Once infected, cattle can be lifetime carriers.

Ticks can remain infected on a pasture for up to two years under favorable conditions.

There is no approved treatment for Theileria orientalis infection.

Management practices include:
Use a consistent tick management protocol
Keep pasture grass short
Regularly inspect cattle for ticks
Use pesticide-impregnated ear tags
Keep cattle out of wooded areas

For more information, visit USDA Emerging Risk Notice and Bovine Theileriosis Information Sheet or University of Missouri Extension publication Theileria orientalis: An Emerging Cattle Disease in Missouri.

The map below shows the confirmed cases of Theileria orientalis and the confirmed locations of Asian longhorned tick in Missouri.

Green – Theileria orientalis confirmed
Purple – Asian longhorned tick confirmed