Questions and answers regarding infection with COVID-19 in mink

Some employees at the mink farms have had symptoms of COVID-19. It appears that the virus was introduced to the mink via these employees.

Mink are very susceptible to the virus circulating in humans. So when infected people get in contact with mink they can very easily infect them.

The virus was detected from the end of April. Since the manditory screening of all Dutch mink farms from 25 May, dozens more farms have been added to that list. Because many animals sensitive to Sars-CoV-2 are kept close together in mink farming, many infections will occur among the mink when infected in a barn.

Read the latest update on our news page about infected mink farms.

The infected mink suffered from gastrointestinal complaints and respiratory problems. The mortality rate at the affected farms was also higher than usual. There is a fatality rate between 1 and 5% (this is not extremely high).

Research from Wageningen Bioveterinary Research shows that the mink died of severe pneumonia.

Closing scheme early on in 2021

Based on the studies carried out and the advice of the Outbreak Management Team Zoönosen (OMT-Z), the Dutch cabinet has decided to introduce a mandatory stopping scheme for all mink farms in the Netherlands. All Dutch mink farms will be closed early on in 2021.

Measures taken from April

Mink farmers were obliged to report symptoms of COVID-19 (respiratory problems and increased mortality) to the national animal disease reporting centre of the Netherlands Food and Consumer Product Safety Authority (NVWA).

Additional protection recommendations were drawn up for mink farms where contamination with SARS-CoV-2 was established.

No transport

The Dutch Ministry of Agriculture, Nature and Food Quality (LNV) has decided that mink were no longer allowed to be transported. Manure from infected mink farms could only be transported to biogas plants where it is heated to at least 70˚C.

Screening of all mink farms

It is likely that the virus has been transmitted from mink to employees. All Dutch mink farms were screened and visitors banned from the stables.

Culling of the infected farms from 5 June

Mink farms infected with COVID-19 were culled from Friday 5 June. The Dutch government took this decision on the basis of the advice of the Outbreak Management Team for Zoonoses and the Administrative Coordination Consultation for Zoonoses. The advice to cull was given because the virus can continue to circulate on mink farms for a long time and can therefore pose a risk to public and animal health.

At all other mink farms an even more stringent control was being instituted, so that any new infections were discovered quickly.

Dutch researchers have shown that ferrets can infect each other via inhalation. Since mink are closely related to ferrets, it is possible that they can also transmit the virus to each other.

Pneumonia was seen in sections on mink and SARS-CoV-2 was detected in organs and throat swabs. Based on the variations in the genetic codes of the virus, it could be concluded that mink farms have transmitted the virus to each other.

• News: Mink with COVID-19 died of severe pneumonia (3 August 2020)

Mink are very susceptible and they are housed with large numbers in relatively small areas. In most farms all the cages are next to each other with a closed wall in-between, but the tops are open. So when the animals cough or sneeze – like mink do – they can easily spread the virus from one top of the cage to the other top of the cage.

It is plausible that employees were infected with the coronavirus by mink. The Dutch government stated this on May 19 and 25.

Further investigation of the increasing number of infected mink farms has shown that many of the employees surveyed were infected with coronavirus (more than 50 percent). Based on the genetic building blocks of the virus, it was possible to establish for some of these employees that this virus was similar to the virus that circulated among the minks on the farm. On this basis, it can be concluded that many of these people are very likely to be directly or indirectly infected by the mink.

Read more about transmission from mink to humans:

• News: Transmission of SARS-CoV-2 on mink farms between humans, mink and back to humans (10 November 2020)
• Article: Occupational and environmental exposure to SARS-CoV-2 in and around infected mink farms (15 January 2021)

Research is being conducted into the source of the infection and the transmission of the virus. It is important to know how the disease develops on the farm, as this provides knowledge about COVID-19 in animals and the transmission from human to animal and animal to animal.

Samples from sick animals are collected on the farms for testing. Samples from healthy animals are also collected for antibodies, so that it becomes clear whether animals without symptoms can also be infected. The research is a collaboration between Utrecht University (UU), GD Animal Health, Erasmus MC and Wageningen Bioveterinary Research (WBVR).

Dogs and cats

Furthermore, dogs and cats on the infected farms are included in the study. Infections were found in cats on the first six farms. The virus was not found in any of the dogs examined. It does not seem very likely that cats play a role in spreading the virus. But given the many households with cats in the Netherlands, it is important to further investigate the role of cats in the potential virus transmission of this respiratory infection.

• Read more about the UU research (Dutch article)

Although the virus is not expected to spread over long distances, air and dust samples were taken in the vicinity of the company as a precaution to see whether the virus is also present here. Research will also be conducted on the manure.

No virus was found in the air samples outside the farms. However, virus has been found in the immediate vicinity of mink on dust particles within the farms. It is still unknown if people can become infected with COVID-19 through these dust particles.

Source: Ministry of Agriculture, Nature and Food Quality (LNV)

In the outbreak regions transmissions between farms were detected. It is still unknown what the main transmission routes were. We are still looking into possible risk factors to find out more about the routes.

The further research on mink farms will be carried out in accordance with internationally applicable standards. Research will be carried out with various institutes in the Netherlands, including Wageningen Bioveterinary Research, and also in cooperation with international partners when necessary.

It is plausible that the virus spreads in animals in the same way as it does between people via droplets in the air. All mink are housed indoors, making it unlikely that the virus will spread over greater distances.

As a precaution, air and dust samples were taken in the vicinity of the farm. The virus was not found in these samples. The advise not to cycle or walk within a radius of about 400 metres around the infected mink farms has therefore been withdrawn.

Pets staying in the vicinity of the farm will be examined for coronavirus infection as much as possible.

The virus was not found in any of the dogs examined. Infections were found in cats on the first six farms, based on virus detection or detection of antibodies against COVID-19. The role of cats in the potential virus transmission of this respiratory infection is under further investigation.

The development of mutations in RNA viruses is a natural phenomenon. The SARS-CoV-2 virus changes in humans, but also when multiplied in mink. In the latter case, it concerns an adaptation to the host.

Because many animals sensitive to Sars-CoV-2 are kept close together in mink farms, many infections will occur when in the case of contamination in a farm. And with every transmission to the next animal, mutation can potentially occur.

In Denmark, a specific variant, the so-called 'cluster 5' variant, has now been found in 12 people. This variant also circulates among mink. It is still unclear whether this variant originated in humans and was transferred to the mink, or vice versa.

The 'cluster 5' variant has a combination of 4 mutations in the Receptor-Binding Domain (RBD) of the virus. This is the part of the virus that binds to the receptor of the host cell (human or animal), after which the virus fuses with the cell and the genetic material can enter the cell.

As a precautionary measure, all mink in Denmark are culled preventively, so that reservoirs in mink farms are prevented. In addition, a strict lockdown has been instituted in the North Jutland region.

The Danish 'variant 5' virus has a combination of 4 changes in the Receptor-Binding Domain (RBD). This variant has not been detected in the Netherlands.

However, various adaptations among mink have been established in the Netherlands. Although the specific combination of these four mutations has not been established in the Netherlands, one of the four mutations on the RBD found in Denmark has also been identified in a number of Dutch mink in the past. At one mink farm, this change was also found among people associated with this farm. The change has not been seen on mink farms after June 21, 2020. It therefore seems that this mutation has faded away in the Netherlands.

Thus the process of adaptation of the virus to the mink is also present in the Netherlands. It is still unclear whether this poses a risk for humans.

It is currently unclear whether the new variant of the virus has consequences for the interaction between the virus and humans, for example because the virus is less neutralised by antibodies after an infection of SARS-CoV-2 or vaccination. Additional studies into this subject will have to be carried out.

On a side note: the severity of the infection and the contagiousness of 'variant 5' of the virus is no different from other SARS-CoV-2 variants.

Mustelids, which include mink, are susceptible to infection with coronavirus, as these animals have specific receptors on their cells that are affected by the virus.

Felines, hamsters and monkeys are susceptible for the same reason, as are bats, from which the virus originates in China. For these animals, coronavirus can also be lethal, but the numbers are still small. Of the twenty or so infected cats worldwide, only one death has been reported.

There are a few cases of infected dogs worldwide, but they have few complaints.

• Read the article about coronavirus in animals

Unlike past cases of swine fever and Q fever, livestock are at little risk. Research shows that pigs are not sensitive to coronavirus, just like chickens. There are also no indications that fish and cows are sensitive to the virus.

The corona virus has been found on imported frozen chicken from Brazil and on the packaging of frozen shrimp from Ecuador. Virologist Wim van der Poel: 'We must assume that the contamination originated in the food production chain, via infected people. Not that they can contaminate the meat or fish: a virus needs a living human or animal to be able to reproduce.'

You cannot contract the coronavirus by eating contaminated food. In theory, if you touch the infected raw chicken and then touch your face, you could get infected, allowing the virus particles to enter your airways. The virologist considers that chance small.

Everywhere where people and animals live close together, there is a risk of zoonoses, so this also includes livestock and pets. The big difference between domesticated animals (both pets and livestock) and wild animals is that we have lived with the former for centuries and that a relatively limited number of animal species are involved. We have a great deal of knowledge about these animals and the pathogens they may be carrying. In addition, there are strict regulations and strict supervision of animal diseases with monitoring systems and, as soon as there are any signals, measures are taken, such as the outdoor ban on poultry in the event of avian influenza.

The coronavirus (SARS-CoV-2) that causes the disease COVID-19, is a virus that originates from wild animals. The number of species and the reservoir of potential pathogens is infinitely greater in wild animals, and we know much less about this. However, we are intervening in the habitat of wild animals in all kinds of ways, such as through mining and cutting down primeval forests, but aspects such as climate change also play a factor, as this causes animal habitats to shift. As a result, there are contacts between animals that previously did not come into contact with each other and people come into contact with animals with whom they previously had no contact. In Europe, for example, the risk of diseases transmitted by mosquitoes is increasing due to climate change.

The Ministry of Agriculture, Nature and Food Quality intends to investigate the extent to which coronavirus occurs in pigs,  cats and mink. Animals will be tested as part of that research.

The reporting of animal diseases is only required for a limited number of animals, and there must be a special reason for this. Because other animals used in livestock farming do not appear to be sensitive to SARS-CoV-2, only mink are now subject to compulsory notification.

As a precaution, animal keepers infected with coronavirus are advised to keep contact with animals to a minimum and to let others take care of them. This applies to pet owners, but also to livestock farmers.

• Read the article about coronavirus in animals

Sick animals with symptoms of COVID-19 should stay inside as much as possible. If you suspect that an animal has COVID-19, we advise you to contact your veterinarian. Wageningen Bioveterinary Research (WBVR) can test animals for the virus.

• More about coronavirus diagnostics