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June’s news that four cows at a Colorado dairy tested positive for bovine tuberculosis (TB) indicates that the disease is still a threat to U.S. cattle herds, despite the nation’s efforts to eradicate it.
At least eight other states have detected bovine TB in herds in the last 12 years, according to the California Department of Food and Agriculture. In addition to Colorado, the highly contagious disease has been found in California, Indiana, Michigan, Minnesota, Nebraska, New Mexico, New York and Texas.
It’s the first time Colorado has seen bovine TB in cattle herds “in quite a number of years,” says Nick Striegel, Colorado’s assistant state veterinarian.
The entire herd at the southern Colorado dairy, which Striegel says milked “a few hundred cows,” was depopulated under an agreement between the owners and USDA’s Animal and Plant Health Inspection Service (APHIS).
“We still have not determined how the infection began in the herd,” Striegel says.
While four cows were originally found to be infected, several others later tested positive for bovine TB.
Colorado had been classified as bovine TB–free before June’s findings. It’s still considered TB-free under USDA-APHIS traditional classification. “No other infected herds have been found in the state,” Striegel adds.
Under a federal order announced earlier this year, USDA-APHIS no longer recommends a whole herd depopulation as the preferred means of disease management. Increasingly large herd sizes make it “difficult to justify depopulation when quarantine and testing may offer an appropriate option,” the order says.
But in the Colorado case, officials supported herd depopulation. The dairy’s owners later performed intensive cleaning and disinfection to eliminate bacteria from the site.
The owners received financial compensation for the depopulation under the USDA-APHIS agreement, but, Striegel says, they are still deciding when or if they’ll resume operation.
Nationwide since 1998, some 82 cattle herds and 10 captive cervid (deer) herds have been found to have bovine TB. Slaughter surveillance has detected 364 infected cattle since 2000: 34 infected adult cattle and 330 infected fed/fat cattle (75% of Mexican origin). The numbers do not yet include the latest finding of infected cows in Colorado.