AABP Executive Director Dr. Fred Gingrich is joined by Dr. Kevin Lahmers, a veterinary pathologist from Virginia Tech, to discuss a disease recently introduced into the US. Theileria orientalis, and specifically the genotype ikeda, can cause clinical disease in affected cattle that present similarly to anaplasmosis. The majority of infected cattle are asymptomatic, however death can occur in 1-5% of cattle and anemia, fever, abortion and icterus. Lahmers states that often the disease is seasonal and associated with the calving season. One clinical syndrome that is different than anaplasmosis is that any age of animal can be affected with clinical disease. The transmission rate is high and many affected herds have 75-100% of the animals testing positive. The Asian Longhorn Tick is the primary biological vector for Theileria orientalis, however, mechanical transmission can occur through common use needles and biting insects. There is currently no effective treatment other than supportive care for clinically ill animals. The Asian Longhorn Tick can become hyperendemic and reproduces asexually, therefore it is common to find heavy infestations on animals. Tick control, pasture management, and maintaining a good plane of nutrition are important preventive measures that can be implemented. Currently a PCR test is available on blood (purple top tubes) or by submitting the spleen of necropsied animals to differentiate the disease from anaplasmosis. If you suspect the disease in your area, Lahmers is willing to discuss it with you by contacting him at [email protected]. 

Relevant links:

A U.S. isolate of Theileria orientalis, Ikeda genotype, is transmitted to cattle by the invasive Asian longhorned tick, Haemaphysalis longicornis

Kelcey D. Dinkel, David R. Herndon, Susan M. Noh, Kevin K. Lahmers, S. Michelle Todd, Massaro W. Ueti, Glen A. Scoles, Kathleen L. Mason & Lindsay M. Fry

Parasites and Vectors March 2021

Co-Infection of cattle in Virginia with Theileria orientalis ikeda genotype and Anaplasma marginale

Vanessa J. Oakes, S. Michelle Todd, Amanda A. Carbonello, Pawel Michalak, Kevin K. Lahmers

BioRxiv April 2021

Information from the Virginia Tech Veterinary Diagnostic Lab can be found here.