Denmark to cull 15 million mink after coronavirus spillover into humans

More than 200 cases of coronavirus appear to be linked to sick mink on fur farms in Denmark, according to new data released by the country’s public health agency. The revelation suggests that mink-to-human transmission is more pervasive than previously thought, though most of the coronavirus cases were likely passed from humans exposed to sickened farm workers and their contacts in the community—not from exposure to infected animals.

Danish officials said that they now want to cull all 15 million mink at the country’s roughly 1,200 fur farms as a precautionary step to protect people from contracting the virus. They plan to kill the mink within the next few weeks. Mink on at least 220 fur farms in Denmark have tested positive for the coronavirus. The culling decision was sparked by findings from the country’s public health authority, the State Serum Institute, which suggested that the virus strain circulating between mink and humans may have mutated enough to compromise future vaccine effectiveness, prompting the need to take immediate action. That work has not yet been peer-reviewed.

“We definitely need to do more studies on this specific variant and its possible effect on future vaccines, but it takes a long time to do these kind of studies,” Tyra Grove Krause, head of the department of infectious disease epidemiology and prevention at the State Serum Institute said at a briefing on November 6. So right now, she said, authorities must act quickly as a precautionary measure,

In a press conference on November 4, Danish Health Minister Magnus Heunicke said that genomic analysis of Danish human cases of coronavirus indicated about half of the 783 human cases of coronavirus in the northern part of the country are related to mink, according to the Associated Press. But by the end of the week a report posted in Danish by the State Serum Institute stated lower numbers: Testing indicated at least 214 people had contracted coronavirus associated with mink. That work has also not been peer-reviewed.

“We are always concerned when a virus has gone from humans to animals, and back to humans. Each time this happens, it can change more,” the World Health Organization told National Geographic in a statement. “So we want to stop this back and forth and the changes that can result.”

Though there isn’t evidence that the virus strain in Denmark is affecting transmissibility, disease severity, or reinfection, “case numbers are currently small and further evidence is needed to fully assess any potential implications of this mink-related variant strain for COVID-19,” the WHO said.

Denmark is one of the world’s largest producers of mink pelts, along with China, so the culling of all its remaining mink will have huge implications for the fur industry. The Netherlands—another leading producer of mink—announced in June that it planned to speed up the timeline for shutting down its mink industry as a result of widespread coronavirus infections among its animals and research suggesting that at least two farm workers had gotten coronavirus from mink. Before the pandemic, the Netherlands had planned to wind down its mink industry by 2024, but now it is expected to shut down all operations by early 2021. China has made no announcements about any changes to its mink industry.

The U.S. situation

The United States, too, has confirmed that mink have contracted coronavirus on fur farms in Utah, Wisconsin, and Michigan, though so far there is no evidence that mink are making humans sick in the U.S. “These investigations are ongoing, and we will release data once available,” says Jasmine Reed, a U.S. Centers for Disease Control and Prevention spokesperson.

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“We are aware of Denmark’s cases and efforts,” U.S. Department of Agriculture spokesperson Joelle Hayden says, noting that the agency is working with the CDC and other partners to monitor the situation outside the U.S.

Unlike Europe, the U.S. has not culled all the mink at farms where animals have contracted coronavirus. There is no federal regulation or requirement concerning methods for handling coronavirus infections at mink farms in the U.S. So far federal authorities have deferred to states to handle outbreaks.

Susceptible species

Denmark first reported that it had discovered sick mink on its fur farms in June, but at that point it appeared that human workers were passing the virus to the animals. At that time, 11,000 animals on the infected farm were culled. More recently, millions of mink have been killed at fur farms in Denmark, Spain, and the Netherlands.

Mick Madsen, the head of communications for Fur Europe, a Brussels-based industry group that represents fur farmers and manufacturers, says, "The government in Denmark has made a decision they did not want to, but public safety must come first. Now the Danish authorities must release their research for scrutiny amongst international scientists." Danish mink production may be allowed to restart in the future, he says, but no decisions have yet been made by the mink farmers.

Mink may be more susceptible to the coronavirus than other animals due to a combination of genetic and environmental factors, the CDC’s Reed explains.

“Farmed mink do not exhibit a large amount of genetic diversity, which can favor infectious disease transmission and susceptibility,” Reed says. “Additionally, farmed mink are often housed in relatively high densities, which favors spread of the virus.”