The Asian longhorned tick (Haemaphysalis longicornis) is the primary vector for Theileria orientalis ikeda, and it transmits the organism through its saliva while feeding on cattle. This disease has been reported in multiple states, including Alabama, Arkansas, Georgia, Iowa, Kansas, Kentucky, Maryland, Missouri, New York, North Carolina, Pennsylvania, Tennessee and West Virginia.
The increasing incidence of T. orientalis ikeda follows the spread of the Asian longhorned tick. As of July 2025, no positive herds west of Missouri included native-born animals. All affected animals were imported from the eastern U.S. states.
Source: Missouri Ruralist, March 3, 2026. Link.
There are NO antibiotics or vaccines available in the U.S. to treat theileriosis, so options are limited . . . The best method to prevent Theileria orientalis in cattle herds is to control tick and biting fly populations.”
INSIGHTS: In 2026, the importance of controlling ticks and flies will be extremely important with the impending threat from New World screwworms and tick-borne diseases.
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