The first sign of trouble was that the mink stopped eating, said Hugh Hildebrandt, one of two main mink vets in Wisconsin. Next came coughing and sneezing, lethargy and labored breathing. Hildebrandt had worked with mink for 30 years. He wrote the Merck Veterinary Manual section on mink. But he had never seen anything like this.
Captive mink have a flu season in the fall, just like people — they get it from us, in fact. But what appeared in the two Taylor County, Wisconsin, mink farms that saw outbreaks in October was not flu, which tends to sicken the weakest animals. This took out the strongest mink, the mature adult females.
Over a few days, it killed hundreds per day and about 5,500 total on the two ranches. It whipped through by coat color, light to dark: The lighter-coat mink, ranch-bred to bring out recessive genes, have long been more delicate.
Five to seven days in, the ranchers thought that most of the mink were going to die, said Hildebrandt. “And they wake up the next morning, and it's just stopped. They all start eating. They eat more than they ever did before.”
It wasn’t hard to guess the cause. Wisconsin was a coronavirus hotspot from late summer on, and workers at mink ranches had already tested positive. The Wisconsin Veterinary Diagnostic Laboratory in Madison confirmed the suspicion within days. The mink almost certainly got it from farmworkers, a jump called “reverse zoonosis.”
The outbreaks shone light on a industry that has for years operated so discreetly in Wisconsin — the nation’s top pelt producer — that even the officials in charge of animal health didn’t know where all of the state’s 19 mink farms were. Those farms are neither regulated nor licensed by the state.
Officials have caught up fast amid concerns that a mutation of the species-hopping virus could pose danger to humans. In fact, the state just added mink farmers to the category of residents next in line for vaccination along with teachers, child care workers and grocery store employees.