SARS-CoV-2 Outbreaks on Mink Farms

If there is anything 2020 has taught us, it is that misinformation on social media and irresponsible headlines from news outlets can cause unnecessary fear, anxiety, and confusion. This article summarises the saga of SARS-CoV-2 (the virus that causes COVID-19) outbreaks on mink farms.

Article last updated: 03 July, 2021

Photo by Nettverk for dyrs frihet (Network for Animal Freedom)

Like many other wild and domestic animals, American mink are susceptible to SARS-CoV-2 infection, and there have been numerous outbreaks reported on mink farms in Canada, the United States, the Netherlands, Italy, Spain, Sweden, and Denmark.(1)

Europe

The Netherlands was one of the first countries to report an outbreak, where more mink were dying than usual, with some showing symptoms of nasal discharge or difficulty breathing. Tens of thousands of farmed mink in the country were gassed with carbon monoxide over fears of mink-to-human transmission. It is believed the virus may have spread amongst the mink via droplets, on feed or bedding, or in dust containing faecal matter.(2)

The Dutch government had initially scheduled to ban mink farming in the country by 2024, but due to the mink’s susceptibility to SARS-CoV-2 and possibility of mink-to-human transmission, this deadline was moved forward to March of 2021.(2)(3)

North America

Other outbreaks on mink farms have occurred in the US states of Wisconsin, Utah, and Oregon.(4)(5) It has been reported that the virus tends to burn itself out at every farm once more than 90% of the mink have contracted the virus and developed antibodies.(3) It is important to emphasize that all of these outbreaks on mink farms are “spill-overs” from the human pandemic, and that there is no evidence the virus originated in American mink. Farmed mink likely contracted the virus from infected staff before spreading it amongst themselves.

Epizootic concerns

A wild American mink tested in the US state of Utah was the first known free-ranging, native wild animal to test positive for Covid-19; further raising concerns and calls to end mink farming. The virus strain detected was the same as the strain found in captive mink on a nearby infected mink farm. Domestic mink frequently escape from fur farms, but it is unclear how this wild mink became infected. Currently, there is no evidence suggesting that SARS-CoV-2 is being passed from mink to mink in the wild near infected mink farms.(6)

Although little research has been conducted on the issue, it is unlikely that feral American mink will spread the virus in the wild. Unlike mink on fur farms which are kept in close quarters and can come into contact with infected mink or humans, both feral and wild mink are territorial and primarily solitary animals, and tend to only interact when breeding. There is a concern that feral cats and other susceptible animals could eat infected mink or come into contact with their feces,(7) but it is unclear how contagious these exposures would be in a non-artificial environment, since the coronavirus’ primary mode of transmission is via respiratory droplets.(8)

On the whole, we are still in the early stages of understanding a complex virus. We should allow more evidence to surface before we, once again, misplace blame on the American mink. Although there is currently no evidence linking SARS-CoV-2 to an intermediate animal reservoir, keeping large groups of animals in industrial farming create perfect breeding grounds for viruses.(9)

Cluster 5 / ΔFVI-Spike mutation

There were reports that the SARS-CoV-2 virus—which humans transmitted to farmed mink—had mutated in these animals in Denmark. This new variant of the virus (termed Cluster 5) was able to be passed back to humans, and was detected in a small number of the Danish population. While not found to be more severe than other strains of the virus, the Danish government believed this variant could be less sensitive to antibodies, and pose a risk that future vaccines will not work if it was allowed to spread within the human population. To lessen fears, the Danish government attempted to pass emergency legislation to cull all of the country’s 15-17 million farmed mink,(10) but nearly a week later this plan was supposedly dropped after receiving opposition from MPs over if the cull order was legal or properly scientifically based.(11) We say supposedly, because despite this political backlash, and the claim by the Danish Health Ministry that the SARS-CoV-2 mink variation had likely died out, the mass cull order commenced.(12)

Some scientific experts found Denmark’s claim that the mutation could undermine vaccination efforts to be a bold statement. According to molecular epidemiologist Emma Hodcroft “It’s almost never the case that it’s such a simple story of one mutation and all your vaccines stop working”. Further, Francois Balloux, the director of University College London’s Genetics Institute, stated that the virus is not likely to increase transmission nor should it be more severe.(13) The term “mutate” often carries negative connotations, but some mutated strains can actually be weaker than earlier versions of the virus, so they are not necessarily always worse. Viruses mutate frequently during their life cycle, and while it is possible a new strain could reduce the effect of COVID-19 vaccines currently under development, the vast majority will not.(14)

On 19 November 2020 the Danish State Serum Institute (SSI) announced that Cluster 5, in all probability, had become extinct.(15)

Mass burials in Denmark

Since Denmark buried millions of mink in mass, shallow graves, built up gases from decomposition later caused their bodies to swell and be push out of the ground.(16) Social media went into a frenzy, with some news outlets using sensationalistic and nonsensical headlines such as “Zombie Mink Rising”, when it was nothing more than a case of poor burial planning (or lack thereof).

Several months later, Denmark’s environmental protection agency raised concern over pollution caused by the mass burials. The main pollutants found at some of the burial sites were ammonia and an excess of nitrogen. The government agency stated that there was no risk of drinking water becoming contaminated. Once the risk of contagion from the killed mink lowers, Denmark plans to unearth the carcasses and incinerate them instead.(17)

Proposal to ban mink fur farms in the United States

A bipartisan proposal in the U.S. House of Representatives aims to ban the sale, purchase, import, and export of mink in the United States over cruelty concerns, and to prevent possible future mutations of the coronavirus.(18)(19)

References
  1. Migdal, Alex. 09 December, 2020. CBC News. Minks at farm in B.C.’s Fraser Valley test positive for coronavirus. Accessed 09 December, 2020.
  2. Enserink, Martin. American Association for the Advancement of Science. 12 June, 2020. Coronavirus rips through Dutch mink farms, triggering culls. Accessed 12 October, 2020.
  3. FOUR PAWS Australia. 31 August, 2020. “The Dutch government announced to shut down the mink farming industry in the country by March 2021“. Accessed 26 October, 2020.
  4. Lewis, Sophie (2020) CBS NEWS. Thousands of mink dead from COVID-19 outbreaks in Utah and Wisconsin“. Accessed 12 October, 2020.
  5. Chávez, Jenn. December 2020. OPB. Mink are catching the coronavirus on farms — including one in Oregon“. Accessed 09 December, 2020.
  6. Davidson, Lee. 14 December, 2020. The Salt Lake Tribune. A wild mink in Utah is the first wild animal anywhere to test positive for COVID-19, researchers say. Accessed 15 December, 2020.
  7. Lanese, Nicoletta. Live Science. November 2020. Escaped mink could spread the coronavirus to wild animals. Accessed 02 December, 2020.
  8. Centers for Disease Control and Prevention. 2020. COVID-19 Overview and Infection Prevention and Control Priorities in Non-US Healthcare Settings“. Accessed 03 December, 2020.
  9. Greger, Michael. May 2009. Factory Farms: Recipe for Disaster“. Accessed 13 October, 2020.
  10. Reuters. 04 November, 2020. Denmark plans to cull its mink population after coronavirus mutation spreads to humans“. Accessed 06 November, 2020.
  11. Kevany, Sophie and Carstensen, Tom. The Guardian. 09 November, 2020. Denmark drops plans for mass mink cull after Covid mutation fears. Accessed 09 November, 2020.
  12. Kevany, Sophie and Carstensen, Tom. The Guardian. 19 November, 2020. Danish Covid mink variant ‘very likely extinct’, but controversial cull continues. Accessed 26 November, 2020.
  13. BRANSWELL, H. STAT. 05 November, 2020. Spread of mutated coronavirus in Danish mink ‘hits all the scary buttons,’ but fears may be overblown. Accessed 09 November, 2020.
  14. Ries, Julie. Healthline. 15 June, 2020. COVID-19 Will Mutate — What That Means for a Vaccine. Accessed 03 December, 2020.
  15. Sundheds- og Ældreministeriet. 19 November, 2020. “De fleste restriktioner læmpes i Nordjylland”. Accessed 06 April, 2021.
  16. Balk, Tim. New York Daily News. 25 November, 2020. Dead mink, killed over COVID concerns, resurface in Denmark. Accessed 26 November, 2020.
  17. AFP in Copenhagen. The Guardian. 05 March, 2021. Pollution fears over mink buried after Covid culling in Denmark. Accessed 06 March, 2021.
  18. Kinnard, Meg. The Associated Press. 02 July, 2021. Proposal would ban mink farming to stem coronavirus mutation. Accessed 03 July, 2021.
  19. Keeley, Matt. Newsweek. 02 July, 2021. Bipartisan Proposal Would Ban Mink Fur Farms Over COVID, Cruelty Concerns. Accessed 03 July, 2021.

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