More cattle found infected with TB on Dane County farm
Farm could be faced with depopulating entire herd based on testing outcome.
MADISON - A series of whole-herd tests have found several more cattle infected with bovine tuberculosis in a Dane County herd. The animal health incident began in late September when a cow at slaughter had lesions in its lungs consistent with TB.
Confirmatory tests were then done in Ames, Iowa at the National Veterinary Services Lab, run by the USDA’s Animal and Plant Health Inspection Service (APHIS).
Because there was what acting State Veterinarian Darlene Konkle called a “strong trace” to Maier Farms LLC in rural Waunakee, several levels of TB testing were done on all of the farm’s cows and young stock – all animals over two months of age.
Konkle gave a report on the unusual incident to the citizen policy board that oversees the Department of Agriculture, Trade and Consumer Protection at a November 15 meeting in Madison.
The incident is unusual since Wisconsin has had TB-free status since 1980. In addition to performing regular drills to rehearse what to do in cases like this, the Division of Animal Health (DAH) staff also has experience doing TB-testing on other farms were TB is suspected. For 2018, through September, DAH field staff have conducted 258 animal disease investigations; 58 of those were related to bovine TB..
Konkle explained that this incident is not going to jeopardize the state’s TB-free status because the case is isolated and there is no evidence that the disease has spread.
In conjunction with the state’s public health authorities, all personnel and service providers at the farm, including breeders, veterinarians, workers, owners and their families were given TB tests.
The genetic testing of the organism isolated from that first cow, which was diagnosed with the disease at slaughter, showed that it matched the DNA of a tuberculosis organism isolated from a worker who had been diagnosed with the disease when he was employed at the farm briefly in 2015.
Testing of the cattle on the farm includes three tests, Konkle said, including a caudal fold skin test, which is the initial screening test. Any animals that are found to be “reactors” in this test are removed from the herd and either necropsied or slaughtered. “All animals reacting to the skin test go to slaughter,” she said.
There were three animals that were reactors that went to slaughter on October 29 and two of them were confirmed to have TB by the National Veterinary Services Laboratory. The genomic testing from those animals’ TB organism wasn’t yet available at the time Konkle spoke to the board.
Another group of animals was being removed from the farm on November 15, as Konkle was giving her report to the board. Genomic testing will be done on all TB organisms isolated from any infected cattle, she said.
Follow-up testing includes comparative cervical tests and blood tests.
Speaking with reporters, Konkle said a total of 48 reactor animals have been removed – ten initially and the remainder of the 48 left the farm on November 15. During the necropsy process, tissues and lymph nodes are taken to test for the TB organism.
When samples come into the USDA’s lab, the organism put through a genome sequencing process. But since the bacterium that causes the disease is so slow-growing, it can take several weeks to get genome sequencing results, she explained.
Working with APHIS officials, state animal health authorities are now looking at any herds that may have had contact with Maier Farms in the last five years.
“Our initial challenges were that this is a large undertaking. We have been working with the Division of Public Health and the Wisconsin Department of Natural Resources on the potential for wildlife involvement,” she said.
Another challenge is that the disease is slow to develop and grow in animals or in humans. The farm is currently under quarantine, which means they cannot move bull calves off the farm nor can they send any cull cows to slaughter. Milk is still being sold from the farm, with the knowledge that pasteurization kills the pathogen that could be carried in the milk. Even if some TB organism were in the milk, the heating of pasteurization is known to kill it.
Though it hasn’t happened in Wisconsin, in anyone’s recent memory, Konkle said that in any given year there are two to eight herds affected by the disease across the United States.
Next steps for Maier Farms “will depend on how many infected cattle we find in the coming weeks,” Konkle said.
One option for the family is depopulation of the whole herd – about 1,000 milking cows and 1,000 head of young stock housed at several locations. Another option would be a test-and-removal protocol, she said, which would require periodic testing.
Board member Paul Bauer commented that the story on this farm broke when national dairy leaders were together at an annual conference of the National Milk Producers Federation. He wondered if it would be possible to give industry partners a heads up before a story like this got into the news.
The department’s head attorney responded that one issue for animal health officials was that when the initial animal was found to have TB in a slaughter plant, it was not immediately known what farm it came from. “If we came out too early it could create difficult circumstances for the farm,” he said.
“There are industry leaders who feel the information could have come to them faster,” Bauer replied. “Maybe it would be possible to find two or three top industry people and give them a heads up when something like this happens.”
Farmers, said Konkle, should always be thinking about biosecurity and “what can be done to do it better” in the wake of this infection.