Theileria Cattle

Theileria orientalis Ikeda

Theileria orientalis Ikeda is an emerging disease in the United States that predominantly affects cattle and is often associated with ticks. There are many types of Theileria that affect multiple species of animals and cause varying symptoms, however, the genotype Ikeda is associated with more severe disease in cattle.

is a parasite that affects red and white blood cells and is typically spread by ixodid ticks, including the Asian Longhorned tick. There is also a risk of spreading disease through routine husbandry practices between infected animals.

Clinical signs associated with Theileria orientalis include anemia, pale gums, late term abortions, and fever. Theileria symptoms are very similar to Anaplasmosis in cattle. Pregnant heifers and calves are the most susceptible to disease. There is no approved treatment or effective vaccine and cattle that recover from initial illness become chronic carriers of disease. There are no known risks to human health.

For Cattle Owners

Fact Sheet

  • Prevention of disease should be focused on tick control.
  • Effective methods of tick control include keeping pastures mowed short, using veterinary approved tick prevention, restricting movement of grazing cattle, and regularly inspecting cattle for ticks.
  • Cattle exhibiting signs such as pale gums or lethargy should be isolated from the rest of the herd and you should contact your veterinarian.
  • Consider testing animals for tickborne diseases before adding to your herd.

For Veterinarians

  • Clinical signs of Theileria in cattle are very similar to anaplasmosis.
  • Cattle presenting with symptoms such as pale mucous membranes, lethargy, fever, or abortions should be considered for Theileria testing, especially if other causes of disease have been ruled out.
  • If you suspect or confirm the diagnosis of Theileria in cattle, contact the State Veterinarian’s office immediately.
  • PCR testing for Theileria orientalis is available from Cornell Veterinary Diagnostic Lab.

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