More questions than answers surround area cattle deaths
The first cows started dying Feb. 28 on Avery and Elizabeth May’s ranch on Potato Creek east of Kyle, SD.
In the weeks that followed, more cows dropped dead, without first showing any obvious symptoms. Most of them were big, healthy cows, Avery said. “There’s no warning,” Elizabeth said. “They just drop.”
One 1,400-pound cow died standing up against a tree, she said.
Some of the dead cows had ticks on them.
As of Tuesday, April 7, the Mays had lost 51 cows. Many other area ranchers have lost cattle, too, with an early appearance of ticks suspected as a culprit. Four ranches within a 30-mile radius lost a total of 145 cows, Elizabeth said.
The Mays found one dead cow with ticks on her on a day that was 14 below zero, she said.
But veterinarians investigating the outbreak caution that ticks might not be the only factor. So far, they have more questions than answers, although they have confirmed the presence of a winter deer tick, which apparently is new to this region. So far, tests have not identified a particular infectious agent carried by the ticks.
So far, about 175 cows from 24 owners have died in the region ranging from the Kadoka-Belvidere area to the White River to the south and beyond, according to Dr. Russ Daly, South Dakota State University Cooperative Extension Service veterinarian at Brookings.
The Mays say the real number is much higher because a lot of ranchers haven’t reported cattle deaths.
Meanwhile, state Game, Fish & Parks officials have found that tick-borne anaplasmosis, a disease that causes anemia, has killed at least 30 deer in the region. Anaplasmosis is infectious but it is not contagious, and there is no evidence that it is being spread from deer to cattle, Daly said.
The veterinarians leading the effort to stem the cattle deaths in the Jackson/Mellette county area are Drs. Norma and Bill Headlee of Kadoka. The Headlees have also been working with Dr. D.G. Luther, DVM, of Louisiana State University, who invented the vaccine for anaplasmosis.
The Headlees have made numerous visits to area ranches, including the Mays’, to take blood and tissue samples from sick and dead cows.
So far, the tests haven’t shown the presence of anaplasmosis in cattle, Norma Headlee said. The tests have also not found the presence of other diseases that could have caused the deaths, she and Daly say. For example, the tests are finding the presence of Blue Tongue, which, by itself, shouldn’t be killing the cows, Headlee said.
But Headlee is still taking samples and sending them to four labs, including the Animal Disease Research and Diagnostic Lab at Brookings; the National Animal Disease Center at Ames, IA; and labs in Kansas and at Colorado State University.
Even if they aren’t carrying disease, the unusually early ticks suck blood from the cows, which are already stressed by pregnancy and a hard winter, Daly said. “There may be several things ganging up on these cows. The most unusual is the tick hatch.”
Headlee said the ticks generally don’t get on cows until after they’ve calved. “These ticks are getting on them while the cow is in the last stage of pregnancy,” says Headlee. “The main thing is we’re seeing an earlier hatch, and we’re probably seeing a nymph stage at a more toxic stage.”
She said tests have ruled out other factors, including “in utero” infections.
The Colorado State lab on March 31 positively identified the presence in the South Dakota samples of the winter deer tick, known scientifically as Dermacentor albipictus, Headlee said.
Headlee said the cattle deaths didn’t appear to be directly related to nutritional deficiencies. She said low calcium levels are typical in cows getting weak just before calving. But the calcium levels with the sick and dead cows she’s investigated were within the normal range, she said. Headlee has painstakingly tested for other possible causes, such as copper deficiencies and lead additives, and hasn’t found a smoking gun, yet.
“The ticks have been the common denominator,” Headlee said. “It seems that where we’re having our biggest problems, there are ticks there, too.”
But Headlee said the areas of highest cattle losses – in Shannon County – haven’t had sick deer.
“But there have been ticks on the cows,” she said.
She said she cannot conclude, based on the data so far, that the ticks brought disease from the deer to the cows.
Headlee praised Game, Fish & Parks staff for sharing helpful information about the tick factor in the deer die-offs. She said GF&P biologists came out in early February after ranchers asked them to check on large numbers of sick and dead deer. The GF&P staffers asked for and followed her suggestions for testing. “They let me know what the results were, and their cooperation with us has helped,” she said.
GF&P wildlife biologist Steve Griffin of Rapid City said an estimated 30 deer are known to have died in the area from Kadoka on south to Shannon County. “That means there’s way more out there,” Griffin said this week. “We’re finding they’re loaded with ticks.”
Griffin said biologists haven’t isolated the type of tick, but their lab work has found anaplasmosis in some sick deer.
He said the winter tick is known to spread anaplasmosis to deer, elk, moose, cattle and sheep. He said other ticks can carry it, too. But he said the lab work so far hasn’t found concrete evidence that the ticks are infecting the deer with it.
No other wildlife in South Dakota has been reported with the disease so far, Griffin said.
Dr. Headlee said she and her rancher clients are treating cattle with antibiotics and insecticide pour-ons having some success. “That makes it look like we’ve got an infectious organism here,” Headlee said.
She said treating cattle with tetracycline or putting it in their feed if they look weak seems to have slowed the incidence of cattle going down. “Once they go down, it’s hard to get them back up,” Headlee said.
The Mays have tried to treat some of their sick cattle. But once they went down, Elizabeth said, “We haven’t saved one.”
Headlee cautioned, “We’re not claiming we’ve got a cure. But because we’re getting a good response to that treatment, we’re going with that.”
Meanwhile, she urges ranchers to keep a watchful eye on their cattle for signs of weakness such as suddenly looking old, quick weight loss or a rough hair coat. And if they have more than the usual one or two older cows die, Headlee urges them to call their local vet right away.
And, she said, ranchers need to start pouring insecticide in January to get the ticks off their cows in the last few weeks before calving.
Daly said he hasn’t seen reports of any other types of livestock dying off or suffering major tick infestations.
Acting South Dakota State Veterinarian Dr. Dustin Oedekoven said he has seen no reports of out-of-the-ordinary death losses elsewhere in the state.
Daly says the cattle affected so far appear to be cows that haven’t calved yet. “I’m crossing my fingers that this is going to end with the cows and not carry over to the calves,” he said.
The Mays say they first started noticing an increase in ticks last year, which saw more moisture for most of South Dakota than earlier in the decade.
“We had ticks crawling on our kitchen floor, you could see them crawling in the grass,” Elizabeth said. “We’ve always had ticks here. But by the first of June, they’re usually gone. Not last year. We had them all summer long.”
And they poured insecticide on their cattle late last fall, she said.
The Mays have been ranching for 30 years. “We’ve never gone through anything like this,” she said.
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