The Asian longhorned tick, slightly larger than a poppyseed, can carry a rare pathogen that has been identified in cattle in multiple Virginia counties.
Theileria orientalis Ikeda strain is a tick-borne disease that causes anemia, death and abortion in cattle. While it is not a risk to human health, it carries the potential for significant economic impacts on cattle farms.
Because the longhorned tick can reproduce asexually, “one tick can produce thousands of ticks,” said Dr. Kevin Lahmers, a veterinary pathologist with the Virginia-Maryland College of Veterinary Medicine.
The tick is native to the Pacific Rim but has spread globally. “It will feed on lots of different hosts … including migratory birds that travel hundreds of miles,” Lahmers explained.
While T. orientalis infection may have been misdiagnosed for years, it has been documented in Virginia cattle since September 2017, when seven cows died in Albemarle County. Since then, the pathogen has been detected in at least 31 Virginia counties—from Northern Virginia to the Shenandoah Valley and into Southwest Virginia, and six other states.
Australian cattle ranchers lose $20 million annually to the pathogen. If left unchecked in the U.S., its estimated economic losses could reach $300 million per year.
In January, the U.S. Department of Agriculture Animal and Plant Health Inspection Service issued an emerging risk notice, reporting there is currently no disease treatment available. Agricultural organizations, including Virginia Farm Bureau Federation, are calling for prioritization of research and educating farmers on mitigation strategies.
“Cattle producers are encouraged to practice ‘intentional observation’ of cattle. Because T. orientalis is a parasite that destroys red blood cells, infected cows may exhibit jaundice, fever, lethargy, difficulty breathing, anemia and gum discoloration,” said Dr. Carolynn Bissett, program manager of the Virginia Department of Agriculture and Consumer Services Office of Veterinary Services.
“The death rate is about 0% to 5%, which is relatively low,” she said. “But once it’s in your herd, cattle stay permanently infected.”
While the disease can’t be treated, ticks can be mitigated through common control methods. Farmers should tuck pants into their socks, apply DEET to themselves, and conduct tick checks on people and pets. For small animals, routine tick control prescribed by a veterinarian works well.
“And for livestock as a whole, most of the pyrethroid-based tick controls seem to be effective at killing the Asian longhorned tick,” Bissett said. “Keep pastures mowed down, particularly in areas you’ve seen lots of ticks. Once we kill the tick, we stop spreading T. orientalis.”
Farmers worried about their herds should call a local veterinarian, who can take blood samples and send them for testing.