Escaped mink carrying the virus that causes Covid-19 could potentially infect Denmark’s wild animals, raising fears of a permanent Sars-CoV-2 reservoir from which new virus variants could be reintroduced to humans.
Denmark, the world’s largest exporter of mink fur, announced in early November that it would cull the country’s farmed mink after discovering a mutated version of the virus that could have jeopardised the efficacy of future vaccines.
Around 10 million mink have been killed to date. Fur industry sources expect the fur from the remaining 5 million to 7 million mink will be sold.
A number of Covid mink variants were identified by Denmark’s state-owned research body the Statens Serum Institut, but only one, known as C5, raised vaccine efficacy concerns. However, Denmark’s health ministry said last week that the C5 mink variant was “very likely extinct“.
Mink are known to regularly escape fur farms and the risk that infected mink are now in the wild was confirmed on Thursday.
“Every year, a few thousand mink escape. We know that because they are an invasive species and every year hunters and trappers kill a few thousand wild mink. The population of escaped mink is quite stable,” said Sten Mortensen, veterinary research manager at the Danish Veterinary and Food Administration.
This year, Mortensen said, there was a risk that about 5% of the minks that escaped from farms were infected with Covid-19.
The risk of the escapees infecting other animals was low, he said, because mink were “very solitary creatures”. But, if they did, the animals most likely to catch the virus would include wild animals such as ferrets and raccoon dogs and “susceptible domestic animals” such as cats.
The most likely transmission route, he said, would be by an animal eating an infected mink or via their faeces.
Mink do not normally die from Covid-19, he added. “Once a mink has had Covid it usually recovers well. Some might have a few days of respiratory difficulty, but most recover and develop immunity.”
The risk of Sars-CoV-2 moving into wild populations has drawn concern from other scientists. Prof Joanne Santini, a microbiologist at University College London, said that, once in the wild, “it will become extremely difficult to control its further spread to animals and then back to humans”.
Transmission to the wild meant “the virus could broaden its host-range [and] infect other species of animals that it wouldn’t ordinarily be able to infect”, Santini said.
Prof Marion Koopmans, head of viroscience at Rotterdam’s Erasmus University, in an email to the Guardian, said: “Sars-CoV-2 could potentially continue to circulate in large-scale farms or be introduced to escaped and wild mustelids [weasels, badgers, otters, ferrets, martens, minks, and wolverines] or other wildlife” and then “in theory, as avian flu and swine influenza viruses do, continue to evolve in their animal hosts, constituting a permanent pandemic threat to humans and animals.”
In the US, there are hopes a mink vaccine will soon be ready. Dr John Easley, vet and research director at the Fur Commission USA said he hoped “one of three vaccine possibilities” would be available by spring for mink farmers in the US and beyond.
However, a mink vaccine is a contentious issue for animal welfare organisations. “Instead of dealing with the fact that the appalling conditions of high-volume, low-welfare fur farming make mink so vulnerable to disease in the first place, it’s easier to distract everyone with talk of a vaccine that could be used like a yearly sticking plaster to compensate for the consequences of those poor welfare conditions,” said Wendy Higgins of Humane Society International.
Sign up for the Animals farmed monthly update to get a roundup of the best farming and food stories across the world and keep up with our investigations. You can send us your stories and thoughts at [email protected]