Central Virginia cattle producer Steve Hopkins and his two sons raise beef cattle on about 1,000 acres in Louisa, VA.

“We have approximately 300 fall-calving commercial cows, separated in five groups on different farms, but all farms are within a 10-mile radius,” said Hopkins, explaining the sequence of events that led to the discovery of a serious disease on his farm. “Three of the farms are very close together and two are a few miles away. The farm where I had the most problems was one of the farms a few miles away.”

Hopkins also custom feeds 175 bulls on a separate farm adjacent to the home farm.

In autumn 2018, during the last third of the calving season, Hopkins started losing cows. He knew something wasn’t right.

“During a period of 10 days, we lost about 10% of cows on one farm,” he said while speaking at a tick symposium. “We didn’t lose any cows or calves on the other operations. In addition to the seven cows we lost on that farm, we lost another 10% of our calves that were stillborn. Between the cows lost and stillborn calves, we lost about 20% of calves in the herd on that farm.”

The problem was eventually determined to be Theileria, a protozoan disease spread by the Asian longhorned tick.

Hopkins said there were some stillborn calves in other herds, but nothing as dramatic as on the farm that saw excessive losses. He recalled having stillborn calves in 2017 but wasn’t sure whether those losses were due to Theileria.

“We have also had problems in the past with anaplasmosis,” said Hopkins. “At the time of the problems we had in 2018, we initially thought it was anaplasmosis. But after losing cows of all ages and when the cows I treated didn’t respond to antibiotics, I knew something was different.”

Some of Hopkins’s cows went down and died within 48 hours; others simply dropped dead. “We were feeding chlortetracycline and hadn’t lost any cows to anaplasmosis for at least 10 years,” he said, “so it seemed like something different.” Although Hopkins hadn’t heard of Theileria, he soon learned what it was.

Shortly after hearing concerns about a new tick disease, in the winter after fall calving, Hopkins decided to sample blood from a dozen cows that were open or cows that lost calves from throughout the 300 cows on the five different farms.

“When we got the results back, 11 out of 12 were positive even though we hadn’t experienced any problems in the other herds,” he said. “Also, our conception rates were normal.”

In summer 2019, Hopkins purchased 22 bred cows. Five weeks prior to calving, he added them to the farm where there had been problems in 2018. “I kept them as a separate group until calving, but they were on the same farm where I had most of the problems,” he said. “The week they started calving, I comingled the herds to better check calves. When they started calving, I lost two cows within one hour of each other to Theileria and lost six calves that were stillborn that had been AI-bred. The calves born later that were not AI-bred seemed to be fine, and I didn’t have any more problems with the cows.”

Hopkins didn’t notice any signs of illness in his own cows on that farm that autumn – only the newly purchased cattle.

“We tried to limit stress,” he said. “We knew with Theileria that was critical. We didn’t get the cattle up and tried to have as little stress as possible, but the stress of calving is what triggered it.”

Since 2019, Hopkins hasn’t had significant problems due to Theileria. He lost several cows that showed clinical signs, and those losses could have been either anaplasmosis or Theileria. He also noted very few stillborn calves since 2018 and believes those stillborns were associated with the Theileria outbreak.

When working cattle today, Hopkins takes great care to limit stress. “We have not seen any Theileria problems with calves or calves in our preconditioning program,” he said. “We have not had any reports of calves after being sold into feedlots having problems, and we keep close ties with all cattle all the way to harvest.” Hopkins added that he would have been made aware if there had been any problems.

To control ticks, Hopkins uses a pour-on insecticide on cows at the time of pregnancy checks in spring. He applies fly tags in early June at weaning and uses a pour-on insecticide in November when cattle are vaccinated.

“We also use separate needles on each cow to prevent the spread,” said Hopkins, “even though we have Theileria throughout the herd.”

Although Hopkins had dealt with anaplasmosis he said a much lower percentage of cattle – below 20% – had anaplasmosis, while more than 90% of his cattle had Theileria.

Hopkins has taken some additional preventive measures to limit Theileria infection. He recalled that in 2019, when he added the cows five weeks prior to calving, that’s when the problem surfaced. Today, Hopkins is cautious about adding cows or bred heifers to herds.

“When we’re moving cattle around, we try to do it at least 10 weeks prior to calving or after calving,” he said. “We stay away from the period six to seven weeks before calving – right before they undergo additional stress.” Hopkins believes that his cattle exposed to or having had a clinical case of Theileria have built immunity to the disease.

by Sally Colby