More than 15,000 minks in the United States have died of the coronavirus since August, and the authorities are keeping about a dozen farms under quarantine while they investigate the cases, state agriculture officials said.
Global health officials are eyeing the animals as a potential risk after Denmark the previous week embarked on a plan to cull all of its 17 million minks, saying a mutated coronavirus strain could move to humans and evade future Covid-19 vaccines.
The US states of Utah, Wisconsin and Michigan said they do not plan to cull animals and are monitoring the situation in Denmark.
"We believe quarantining affected mink farms in addition to implementing stringent biosecurity measures will succeed in controlling Sars-CoV-2 at these locations," the US Department of Agriculture (USDA) said on Tuesday.
It added it's working with the US Centres for Disease Control and Prevention (CDC), state officials and the mink industry to test and track infected farms.
The US has 359,850 minks bred to produce babies, known as kits, and produced 2.7 million pelts the previous year.
Wisconsin is the largest mink-producing state, followed by Utah. Sick minks in Wisconsin and Utah were exposed to people with probable or confirmed Covid-19 infection, the USDA said. In Michigan, it's still unknown if the minks were infected by humans, it added.
In Utah, the first US state to confirm mink infections in August, about 10,700 minks have died on nine farms, said state veterinarian Dean Taylor. "On all nine, everything is still suggesting a one-way travel from people to the minks."
Coronavirus testing has been done on minks that die and randomly on the affected farms, said Dr Taylor. Some minks are asymptomatic or mildly affected.
The CDC said it's supporting states' investigations into sick minks, including testings. "These investigations will help us learn more concerning the transmission dynamics between minks, other animals around the farms and people. Currently there is no evidence that animals play a significant role in the spread of Sars-CoV-2 to people."
Coronavirus is thought to have first jumped to humans from animals in China, possibly via bats or another animal at a food market in Wuhan, although several outstanding questions remain.
Monitoring US minks for virus symptoms and quarantining infected farms should limit the disease's spread if cases are caught early, said virologist Richard Webby.
The US authorities are urging farmers to wear protective gear when handling minks to avoid infecting the animals.
One farm in Wisconsin is composting the dead minks to dispose of the carcasses without spreading the virus, state veterinarian Darlene Konkle said. The authorities are working with another farm to decide how to dispose of the minks, and dead animals are being kept in a metal container in the meantime.
State officials said they are working with the USDA to determine whether farmers can sell the pelts of infected minks. The pelts are used to make fur coats and other items.
REUTERS