Disease carried by ‘self-cloning’ ticks kills cattle in two Kentucky counties

A new disease carried by an invasive species of tick has killed cattle in two counties, and the Kentucky Department of Agriculture is alerting farmers of the emerging risk to their herds.

The illness, caused by a protozoan called Theileria orientalis Ikeda, caused the death of one beef breed bull in Hart County and another in Fleming County. The Asian longhorned tick is known to carry the disease.

The agriculture department said Friday that there was no relationship between the two affected herds. The illness does not affect people.

“Though a threat to cattle, the disease is not a threat to human health,” the agriculture department’s news release stated. “Humans cannot become sick from contact with affected cattle, and consuming meat from affected cattle is safe provided the meat has been cooked to an appropriate temperature.”

Theileria “infects red and white blood cells causing severe anemia in cattle as well as abortions, stillbirths, weakness, reluctance to walk, and death. Physical examination may reveal pale mucus membranes, high fever and elevated heart and respiratory rates,” the ag department said.

A blood test can confirm the disease. Cattle that are infected can then become carriers affecting other members of the herd, the state said.

Because “there is no approved effective treatment or vaccine for the disease,” the state said it’s important to work to prevent it.

The Kentucky Department of Agriculture is working with the University of Kentucky and Murray State University and the Virginia-Maryland College of Veterinary Medicine Diagnostic Laboratory to set up a “passive surveillance system” to help identify the presence of the tick and the disease in Kentucky.

The state veterinarian is conducting free blood testing for Theileria, and the state said affected farms and owners will be kept confidential.

“Results are available to producers. Information gathered will be used to create maps that depict the spread of the ALT (Asian longhorned tick) and Theileria across Kentucky,” the news release stated. “Those who want to submit tick samples for identification or cattle blood samples for Theileria testing can contact Kentucky Deputy State Veterinarian Dr. Kerry Barling at Kerry.Barling@ky.gov or call (502) 782-5291 for more information.”

Farmers are encouraged to take measures to keep ticks off their livestock, such as keeping pastures mowed, keeping cows out of wooded areas and inspecting for ticks on cattle regularly.

Acaricides, or chemicals that kill ticks and mites, can be applied with ear tags, or poured or rubbed onto the backs of livestock. The state said long-acting treatments such as ivermectin, moxidectin and eprinomectin “have shown to be effective in tick control in field research trials.”

Producers should also use a clean needle for every injection to help keep blood-borne illnesses from spreading and get a veterinarian involved if an animal is weak or lethargic, the agriculture department said.

Aside from livestock, the Asian longhorned tick also can attach itself to wildlife, birds, cats, dogs and humans, sometimes in large numbers.

The ticks, which are known for their ability to “clone” themselves, were first found in the United States in New Jersey in 2017, and they were found to have spread into Kentucky in 2020.

“This tick is an aggressive biter and frequently builds intense infestations on domestic hosts that can cause stress, reduced growth and severe blood loss,” Jonathan Larson, UK extension entomologist, said in a 2020 news release. “One reason for their rapid buildup is that the female ticks can lay eggs without mating. It only takes a single fed female tick to create a population of ticks. Potentially, thousands can be found on an animal.”

That summer, they were found in large numbers on a bull in Metcalfe County and in smaller numbers on elk in Martin County and black bear in Floyd County.

Since then, they’ve also been located in Boone, Madison, Breathitt and Perry counties, though the agriculture department says they may be in other counties as well but have just not been identified yet.

“The Kentucky Department of Agriculture and the Office of the State Veterinarian is working closely with agriculture producers to contain these incidents and protect our herds across the state,” Agriculture Commissioner Ryan Quarles said in a news release. “Protecting the health of livestock in the commonwealth is a top priority of the Kentucky Department of Agriculture.”