
26/02/2025
We have recently had a spree of cases caused by a novel pathogen affecting cattle in our area - Bovine Theileriosis. The cases have been spread from Ritchie to Preston counties.
Here is some basic information and what to look for:
What is it?
Theileriosis is a disease caused by the blood-borne protozoa Theileria orientalis Ikeda. The protozoa is transmitted primarily via Asian Longhorn Ticks (pictured below). It can be passed between cattle through sharing needles or through blood transfusions.
What is the disease process?
The blood-borne protozoa infects the body’s red and white blood cells, ultimately causing a hemolytic anemia and systemic infection.
What cattle are susceptible?
All cattle are at risk, but not all those infected will develop clinical signs. As more cases are reported, it seems that those with underlying diseases (BLV, Johne’s, etc.) are at an increased risk to developing clinical signs. Pregnant heifers and calves seem to be more susceptible, as well.
What are the clinical signs?
The anemia leads to pale to yellow mucous membranes. Other signs include generalized weakness, loss of appetite, and difficulty breathing with nasal discharge. Reduced milk production and abortion can also be seen. This disease has a presentation that is similar to Anaplasmosis.
How is it diagnosed?
Theileriosis is diagnosed via blood samples:
- PCR (most specific) - Detects the protozoa’s DNA within the blood sample.
- ELISA - Detects either the protozoa’s antigens or the body’s antibodies against the protozoa.
- IFA - Detects the body’s antibodies against the protozoa.
How is it treated?
Currently, there is no specifically approved treatment in the United States.
How is it prevented?
Currently, there is no vaccination against T. orientalis.
Implementing proper management strategies is the best way to prevent Theileriosis:
- proper tick control
o keeping pastures cut short
o EPA-approved insecticide treatments
o FDA-approved tick-managing drugs
- proper needle/equipment management
- proper herd management
o keeping disease-free herds
Is there any zoonotic risk?
This protozoa is not known to be transmissible to humans.
What do I do if I suspect Theileriosis in my herd?
If you have suspicions of Theileriosis, please contact your veterinarian or State Deptartment of AG for testing and further instruction!
Sources
“Bovine Theileriosis Information Sheet.” Aphis.Usda.Gov,
www.aphis.usda.gov/sites/default/files/bovine-theileriosis-infosheet.pdf. Accessed Feb.
2025.
Strickland, Lew. “Theileria Orientalis Ikeda in Tennessee.” UT Institute of Agriculture, 10
June 2022, vetmed.tennessee.edu/theileria-orientalis-ikeda-in-tennessee/.
https://www.aphis.usda.gov/sites/default/files/bovine-theileriosis-infosheet.pdf