Denmark is debating whether to cull its entire stock of farmed mink—some 17 million animals—after a mutated version of the novel coronavirus in mink infected hundreds of people. So far, mink are the only known species that can catch the virus from humans as well as infect humans with it, raising biosecurity concerns in nations that farm minks for their fur.
Danish Prime Minister Mette Frederiksen called for “resolute action” last week, in the wake of multiple coronavirus outbreaks in mink farms across the nation. Experts fear that the spread of the virus among minks could reduce the efficacy of an eventual vaccine for humans, which could exacerbate the Covid-19 pandemic.
“As a government, we will do everything we can to ensure that the mutated infection is contained and does not spread further,” Frederiksen said in a statement on Wednesday. “Therefore, it is—unfortunately—necessary to kill all mink in Denmark.”
The proposed cull has provoked political pushback and it is not clear yet what precise actions the nation will take to address the issue. Coronavirus outbreaks have also occurred on mink farms in the Netherlands, Spain, Sweden, Italy, and the US, resulting in the premature culling of millions of mink, according to the BBC.
Minks belong to a family of carnivorous mammals called mustelids that also includes weasels, ferrets, and martens. Farmed mink are especially vulnerable to viral infections because they tend to be packed in tight quarters with plenty of exposure to both animals and people, accelerating the spread of mutated forms of the disease.
“Mustelids are very easy to infect,” said Christian Sonne, professor of veterinary and wildlife medicine at Aarhus University in Denmark, in an email. “Their density facilitates lots of mutations and their close contact to people makes them jump forth and back in a way to become pathogenic.”
These mink mutations could interfere with the success of an eventual Covid-19 vaccine in humans because they produce variations of the spike protein that the virus uses to enter cells. Vaccines are designed to trigger the immune system to make antibodies that bond to the spike, which neutralizes the infection. However, mutated virus spikes in mink may not respond to a vaccine designed for other iterations of the virus.
“If these mutations alter too much, the vaccine based on these spikes no longer works as the antibodies cannot any longer attach to the spike,” Sonne explained. “It’s like a key. You change the lock (spike proteins) and the key (antibodies) won’t work anymore.”
“So if mink have coronavirus that the vaccine cannot kill through antibody production, you have a pool of SARS-CoV-2 virus that can infect humans and kill them as the vaccine is ineffective,” he said.
It is too early to know whether the viral outbreaks in mink farms would have any impact on a vaccine. But the clear risk of mink-to-human transmission—not only in this pandemic, but in future outbreaks—has spurred nations such as the Netherlands and France to commit to phasing out their mink industries by the mid-2020s.
In a recent article in Science, Sonne and his colleagues urged nations to ban mink production, not only due to these biosecurity risks, but because of concerns for animal welfare and the industry’s climate footprint. For instance, the researchers pointed out that mink fur has a climate footprint that is five times higher, per kilogram, than herbivore-based textiles such as wool.
The decision to ban farmed mink “boils down to the economy,” Sonne said. “But I know that in China, which is the biggest market, the use of mink clothing is declining. And the mink industry has decreased significantly anyway over the last five to ten years.”
He hopes that means that the “market will maybe die out” faster, which would ameliorate the many problems—ranging from animal rights, to environmental damage, to public health—that stem from farmed mink.