41 cattle infected with TB in Harding County; local wildlife harvested to prevent spread of disease

The investigation has been ongoing since February. A total of 41 animals were found to be infected with the disease. Thirteen neighboring ranches were quarantined in an effort to prevent the disease from spreading. So far six of those ranches have been released. The remaining seven still have testing to complete, state agriculture officials say.

Three cattle were identified at two Nebraska slaughtering facilities during a routine USDA inspection in February. They had been in three separate feedlots in Nebraska and South Dakota since November 2016.

The National Veterinary Services Laboratory in Ames, Iowa identified the a strain of Mycobacterium bovis, the bacteria strain of tuberculosis, nearly identical to a strain previously only seen in central Mexican dairy cattle.

State Veterinarian Dustin Oedekoven said there is much speculation, and at least two possibilities, as to how that specific strain entered South Dakota.

“One, it came with cattle. A million to a million and a half cattle are imported from Mexico to here. They’re all tested and inspected for animal health issues. We also have additional test requirements if they enter from Mexico into South Dakota. We don’t know if these cattle are of Mexican origin. It’s a possibility, but it’s a long shot,” Oedekoven said.

He said the other possibility is that it was brought in by people. Bovine tuberculosis can infect humans, Oedekoven said.

“Both those possibilities are difficult to prove at this point. We don’t know how this herd was infected at this time,” he said.

As to if the TB-free status would be revoked from South Dakota, Oedekoven said it depends on how and if this tuberculosis strain spreads.

“At this point, our staff at the Animal Industry Board and USDA Vet Services are working with producers in this state, and other states where cattle may be related to this herd. We’re assessing the spread of this disease.”

An initial herd test was done to determine if the cattle contracted TB. All animals that tested positive on the initial herd test were removed from the herd and the remaining tested negative.

The cattle testing negative for the disease at this point does not mean they aren’t infected with TB. The test shows which animals in the herd are infected, but it also has a known false negative rate, Oedekoven said, so there could be more infected animals.

Oedekoven said the way the Animal Industry Board would like to handle the herd is by depopulating it or moving the animals to slaughter.

The ranchers who own the cattle will be paid by the USDA for the loss their animals, Oedekoven said. The state currently is awaiting approval for that step.

As far as wildlife are concerned, harvesting animals to test for tuberculosis is still in progress. Deer and pronghorn antelope in a three-mile radius of the infected herd will be harvested said Mike Kintigh, South Dakota Game, Fish, and Parks regional supervisor for Region I. Traps for possums, raccoons and badgers also were set on the ranch with the infected herd.

“We’ve been advised that coyotes are a pretty good indicator species of how far the disease had spread if it’s in wildlife,” Kintigh said.

For coyotes, there are two kill radius circles around the ranch; one at ten miles and another at 20 miles.

Kintigh said there are no direct links to wildlife yet. “That’s what we’re doing this work for--to see if it’s there.”

Harvesting wildlife either happens on the ground or by air from a helicopter. The goals were to harvest 50 antelope, 100 whitetail and mule deer, and an open number of coyotes.

The animals, older than one year, are targeted, picked up and carried to a lab in their entirety. The big game animals are hung before being processed. Then their lymph nodes are removed from the head, near the heart, and other locations. A federal veterinarian looks at the heart and lungs for signs of external lesions. Once the organs are inspected, the veterinarian will look at the chest walls for abnormalities.

Six to eight samples come from each animal, Kintigh said.

Kintigh said GF&P staff had almost reached their goal on antelope and deer and could finish testing on those animals by Thursday, March 30.