By John Lovett
As cases of a deadly cattle disease rise in Arkansas, researchers with the Arkansas Agricultural Experiment Station are testing two treatments they hope will help ranchers protect their herds.
The disease is bovine theileriosis and is caused by the parasite Theileria orientalis Ikeda, carried primarily by the invasive Asian longhorned tick. Arkansas cases of the disease increased drastically in 2025, just a year after being confirmed in the state, said Emily McDermott, an assistant professor in the department of entomology and plant pathology for the experiment station, the research arm of the University of Arkansas Division of Agriculture.
No approved drugs or vaccines to treat or prevent the pathogen are currently available in the United States, but research on the two methods to control it is now underway at the experiment station thanks to a two-year, $492,218 grant from the U.S. Department of Agriculture’s National Institute of Food and Agriculture.
Arkansas cattle ranchers are reporting “significant losses of the herd, resulting in economic hardship,” said McDermott, project director of the NIFA grant titled “Rapid response strategies to mitigate Theileria orientalis Ikeda spread in Arkansas.”
As part of the research, McDermott and her collaborators will evaluate a prescription anti-tick vaccine from the company Medgene for long-term protection and the slow-release parasiticide eprinomectin, used with currently labeled acaricides for the Asian longhorned tick. The eprinomectin will be compared to two available pyrethroid products.
Both treatments are commercially available and can be adopted quickly by producers, she said.
‘I thought it was anaplasmosis, but it was weird’
In cattle, the symptoms of bovine theileriosis tend to mirror those of anaplasmosis, a bacterial disease also transmitted by ticks to cattle. Symptoms in the cow may include weight loss, reduced milk production, loss of appetite, anemia and reproductive losses.
“One of the tricky things about Theileria is that it looks so much like anaplasmosis that I think a lot of producers might not be aware they have a new disease,” McDermott said. “We’ve heard the same story a lot over the last year … ‘I had a bunch of cows die, and I thought it was anaplasmosis, but it was weird.’
“The more that we’re getting information out there about Theileria, a lot of producers are starting to think that something else was going on,” she said.
A major difference between the two diseases is that bovine theileriosis can cause symptoms in cattle of any age, whereas anaplasmosis symptoms and illness typically occur in older cattle, said Kelly Loftin, extension entomologist for the Division of Agriculture and a collaborator on the research.
Source : uada.edu