Figures 6–14. SARS-CoV-2 infection, mink. Figure 6. Lung, adult mink. Diffuse alveolar damage with formation of hyaline membranes. Hematoxylin and eosin (HE). Figure 7. Lung, adult mink. Degeneration and necrosis of bronchiolar epithelial cells with formation of syncytial cells and with type II pneumocyte proliferation. HE. Figure 8. Trachea, adult mink. Diffuse loss of cilia and swelling and flattening of epithelial cells. HE. Figure 9. Nasal conchae, adult mink.Multifocal swelling and degeneration of epithelial cells with a mild infiltrate of inflammatory cells. HE. Figure10.Lung,minkkit. Diffuse alveolar damage with numerous hyaline membranes (inset). Hypercellular appearance of the alveolar walls is normal at this age. HE. Figure 11. Lung, adult mink. Bronchiolar epithelial cells, (desquamated) pneumocytes and macrophages are immunolabeled for SARS-CoV-2 antigen. Figure 12. Lung, mink kit. Pneumocytes as well as desquamated pneumocytes and/or macrophages are immunolabeled for SARS-CoV-2 antigen. Figure 13. Trachea, adult mink. Immunolabeling of epithelial cells. Figure 14. Nasal conchae, adult mink. Immunolabeling of normal and flattened epithelial cells.**

1. Symptoms of the disease and the infection of mink

How did the mink become infected?
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.

How many mink were infected? 
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. A few mink showed symptoms of the disease on the farms. The mink are kept in separate pens, which means that there is little to no contact between the animals.

What symptoms did the mink display? The infected mink suffered from gastrointestinal complaints and respiratory problems. The mortality rate at the affected farms was also higher than usual.  Research from Wageningen Bioveterinary Research shows that the mink died of severe pneumonia.

Was it already known that mink are sensitive to coronavirus?  
Mustelids such as mink are extra sensitive to coronavirus. Like humans, they have a protein on their lungs, the ACE2 receptor, to which the virus likes to attach itself. Humans also have this ‘coronavirus binder’ on the mucous membranes of their mouths, for example. This protein appears to be a good predictor for possible infection with COVID-19.

How was coronavirus diagnosed in mink?
The mink symptoms prompted the veterinarians to have an investigation carried out by the Animal Health Service. Since the animals tested negative for the most obvious bacterial diseases, GD Animal Health also tested for coronavirus (SARS-CoV-2) due to the alleged susceptibility of mink to infection and because individuals with COVID-19 symptoms were working on both farms. The PCR test showed an infection with coronavirus. A similar test at Wageningen Bioveterinary Research (WBVR) confirmed this result.

What are the consequences for mink farms? 
Mink farmers are now 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 have been drawn up for mink farms where contamination with SARS-CoV-2 has been established.

No transport

The Dutch Ministry of Agriculture, Nature and Food Quality (LNV) has decided that mink and their manure are no longer allowed to be transported. The risks presented by the manure seem small but will be investigated further. On 10 July, LNV adjusted the regulations. Manure from infected mink farms may 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 will be screened and visitors are banned from visiting the stables.

Culling of the infected farms from 5 June

The Dutch government announced that the mink farms infected with COVID-19 will be culled from Friday 5 June. The 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.

Closing scheme from spring 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 from the spring of 2021. Infected farms will be culled and at all other mink farms an even more stringent control is being instituted, so that any new infections are discovered quickly. This is stated in a letter to Parliament of 28 August.

Can mink transmit the virus to each other? (via inhalation)
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.

Can mink transmit the virus to humans?
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.

Are further infections on mink farms expected? 
There are approximately 140 fur farms in the Netherlands. Now that mink appear to be susceptible to the virus, there is a chance that the virus will be found on more farms. Mink farmers are obliged to report this to the Netherlands Food and Consumer Product Safety Authority. All Dutch mink farms are screened and visitors are banned from visiting the stables. Infected farms are culled as of June 5. During this screening on more farms in the Netherlands COVID-19 infected mink have been found. A letter to Parliament dated 28 August states that an even more stringent control is being instituted for all Dutch mink farms. And a mandatory closing scheme for mink farms in the Netherlands is introduced from the spring of 2021. Besides the infections found in the mink farms there are currently no known cases where coronavirus has been detected in farm animals.

2.Research on coronavirus in mink

What is being researched at these farms? 
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 Bioveterina. 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

Is there any research taking place in the immediate environment?
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 not unknown that people can become infected with COVID-19 through these dust particles. Source: Ministry of Agriculture, Nature and Food Quality (LNV)

What is the purpose of the research? 
The research will gather knowledge about how the virus behaves in animals. This knowledge may also be important to find out more about the spread of the virus between people.

Is there international coordination in this research? 
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

3. Is there any danger to the environment?

Are there risks for people in the vicinity of the infected farms? 
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.

What is the situation for pets in the area? 
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 outbreak is in the same area which experienced cases of Q fever and swine fever. Is this a coincidence?
This is an area with a great deal of livestock farming, especially of animals such as poultry, pigs and mink. Generally, these areas have more dust in the air. But we see no connection between this outbreak and previous outbreaks of other animal diseases, because these are very different diseases with different modes of transmission. 

4. Other animals and coronavirus

Which kept animals are susceptible to coronavirus? 
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.

Is there cause for concern about coronavirus for livestock farming?
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.

Will more livestock and other animals be tested now? 
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.

Why is there no requirement to report COVID-19 in animals? 
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.

Can animals that now appear to be insensitive to the virus still get coronavirus? 
Yes, they could. If the disease mutates, the virus could possibly infect other species. However, we have currently not seen any indications for this.

What happens if coronavirus is found in farm animals in the Netherlands? 
In the event that a livestock animal becomes infected with COVID-19, the Ministry of Agriculture, Nature and Food Quality and the Ministry of Health, Welfare and Sport will jointly decide on the measures to be taken. Cooperation between the Ministry of Agriculture, Nature and Food Quality and the Ministry of Health, Welfare and Sport will take place in accordance with the beleidshandboek crisisbesluitvorming zoönose (zoonosis crisis decision-making policy manual).

Can cows and other animals still be put out to pasture? 
There is currently no reason at all to keep animals indoors. Cows and other farm animals can simply go outside if this is in line with normal business operations. 

Can food become contaminated?
In some slaughterhouses in the Netherlands, cases of employees with the coronavirus are known. There is no evidence that food, such as meat, is a source of the transmission of the coronavirus. The virus needs humans or animals to stay alive and grow. That is not possible in food. In addition to this, currently no coronavirus infections are known in for example, pigs, cows and poultry.

5. Handling my animal

I have symptoms of COVID-19. Should I stay away from my animals?
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.

I think that my animals might be infected with COVID-19. What should I do? 
Sick animals of patients infected with or with symptoms of COVID-19 should stay inside as much as possible. This also applies to cats, which may infect each other, just like the lions and tigers in a New York zoo. Keep your distance from animals that show symptoms of disease and wear gloves when changing the litter box. If you suspect that an animal has COVID-19, we advise you to contact the veterinarian by telephone. The Netherlands Food and Consumer Product Safety Authority decides together with the veterinarian whether additional research is necessary. Wageningen Bioveterinary Research (WBVR) can test animals for the virus, but only in cases of risk and at the request of the Netherlands Food and Consumer Product Safety Authority.

What are the risks of coronavirus and zoonoses for/by intensive livestock farming? 
Everywhere where people and animals live close together, there is a risk of zoonosis, 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.

Is there an influence of livestock farming and air pollution on the impact of corona on people?
Minister Schouten asked the National Institute for Public Health and the Environment (RIVM) to investigate the possible influence of livestock farming and air pollution on the impact that corona has on people's health. In doing so, she responds to the calls of local politicians and mayors. RIVM submitted this request this week to the consortium Veehouderij en Gezondheid van Omwonenden (VGO), in which it collaborates with Utrecht University and Wageningen Bioveterinary Research (WBVR), among others.

Is there anything I can do to prevent infection and transmission of the virus to my livestock farm? 
Make sure you comply with the general hygiene rules, which also apply to preventing the introduction of animal diseases. Apply the hygiene measures when entering the animal enclosures, do not allow unnecessary visits to the farm and ask someone else to care for the animals if you are a COVID-19 patient. 

*©WBVR, and SARS- CoV-2 infection in farmed minks, Nadia Oreshkova et al. 2020

**Clinical and Pathological Findings in SARS-CoV-2 Disease Outbreaks in Farmed Mink (Neovison vison) https://doi.org/10.1177/0300985820943535