spotlight topic:

COVID-19 and animals

Case reports

Mink – Netherlands, Denmark, Spain and Sweden

Added 27 April 2020 | Updated 9 November 2020

The SARS-CoV-2 virus has been detected in mink at two fur farms in the Netherlands. Workers at both farms had tested positive for the virus, and it is likely that they transmitted the infection to the animals. It is reported that there are around 20,000 mink between the two farms. The infections were confirmed on Friday, 24 April 2020 by researchers from the Wageningen Bio-veterinary research in Lelystad.

Infected animals were reported to have shown gastrointestinal and respiratory signs, but the report does not state how many animals are affected. Areas around the farms have been closed to the public.

Update [18 May 2020]

Outbreaks of SARS-CoV-2 have been detected at a further two mink farms, in the Netherlands bringing the total number of farms affected to four. Initial research on the first two infected farms show that it is likely  that the virus is being transmitted between mink, but that there is currently no evidence that animals play a role in the spread of the virus to humans. It appears that the infection can lead to pneumonia and death among the minks, but the percentage of sick animals and the death rate is limited, with the disease mainly affecting heavily pregnant animals.

Analysis of air samples taken from outside the mink housing found no evidence of the virus. However, the virus has been found in the immediate vicinity of mink on dust particles within the house. It is still unknown whether people can become infected with COVID-19 through these dust particles.

It has also been reported that 3 out of 11 farm cats at one of the mink farms tested positive for SARS-CoV-2 antibodies but tested negative for the virus.

Update [8 June 2020]

Outbreaks of SARS-CoV-2 have been detected at a further 3 mink farms in the Netherlands and is suspected at one other. It has now been announced that the Dutch Government intends to cull all mink at infected farms.

It has also been reported that a further 2 workers on infected farms have been diagnosed with COVID-19, raising the possibility that they had been infected either directly or indirectly from the mink.

Update [3 July 2020]

On 15 June 2020, the National Reference Laboratory informed Danish Veterinary and Food Administration that mink from a farm in Northern Jutland (municipality of Hjørring) tested positive for SARS-CoV-2. There were no symptoms in the animals and no report of increased mortality. The samples were collected, because the Danish Veterinary and Food Administration had been informed that a person with contact to the farm had tested positive.

Update [17 July 2020]

There have now been 24 mink farms in the Netherlands, and three in Denmark, with confirmed infection.

Coronavirus has  also been confirmed at a mink farm in Spain.

Update [28 July 2020]

Molenaar, R.J. et al. (2020)  Clinical and Pathological Findings in SARS-CoV-2 Disease Outbreaks in Farmed Mink (Neovison vison). Veterinary Pathology https://doi.org/10.1177/0300985820943535

This paper provides a report of the clinical and pathological characteristics of SARS-CoV-2 outbreaks on the first four mink farms to be affected in the Noord-Brabant province in the Netherlands.

The most striking post-mortem finding was reported to be an acute interstitial pneumonia, with acute alveolar damage, which was found in nearly all examined mink that died at the peak of the outbreaks. Other organ systems were reported not to be affected in the examined mink.

Histological evaluation showed interstitial pneumonia and lung samples of these mink tested polymerase chain reaction (PCR)-positive for SARS-CoV-2 and PCR-negative for both influenza A virus and canine distemper virus, and no growth on routine aerobic cultures.

SARS-CoV-2 infections were confirmed by detection of viral RNA in throat swabs and by immunohistochemical detection of viral antigen in nasal conchae, trachea, and lung.

Clinically, the outbreaks lasted for about 4 weeks, but some animals were still PCR–positive for SARS-CoV-2 in throat swabs after clinical signs had disappeared.

It was noted that the large variation in morbidity and mortality at each farm suggests that outbreaks can be so mild that they could be easily missed.  The paper concludes with the following recommendations:

  • For diagnosis of SARS-CoV-2 infection on farms where mink have clinical sign throat swabs in combination with histopathology of the lungs are recommended.
  • For surveillance of farms without clinical signs, PCR testing of throat swabs from mink that recently died can be considered, even in the absence of gross lesions.

Update [9 November 2020]

Sweden has also now confirmed 10 cases of infection with SARS-CoV-2 in mink at farms in the southeast part of the country, in the County of Blekinge,  where approximately 20 of Sweden’s 40 mink farms are situated.

The genome sequence analysis of the SARS‐CoV‐2 viruses detected from mink and humans in close contact with the infected animals at the index farm clustered together and belonged to the lineage B1.1.39. None of the amino acid mutations described on the spike protein of the recent Danish mink SARS-CoV-2 viruses is, so far, present in the spike gene of the Swedish mink SARS-CoV-2 viruses

References

  1. NOS (2020) Coronavirus vastgesteld bij nertsenfokkerijen in Noord-Brabant [online] Available at: https://nos.nl/artikel/2331784-coronavirus-vastgesteld-bij-nertsenfokkerijen-in-noord-brabant.html[Accessed 26 April 2020]
  2. NL Times (2020) Mink found infected with COVID-19 at two Dutch fur farms; areas now closed to public [online] Available at: https://nltimes.nl/2020/04/26/mink-found-infected-covid-19-two-dutch-fur-farms-areas-now-closed-public [Accessed 26 April 2020]
  3. ProMED International Society for Infectious Diseases (2020) Netherlands (NB) animal, farmed mink, spread, rabbit susp [online] Available at: https://promedmail.org/promed-post/?id=20200509.7316646 [Accessed 18 May 2020]
  4. NLTimes (2020) Dutch find coronavirus antibodies in first dog, 3 cats; No risk at mink farms [online] Available at: https://nltimes.nl/2020/05/15/dutch-find-coronavirus-antibodies-first-dog-3-cats-risk-mink-farms [Accessed 18 May 2020] 
  5. Successful Farming (2020) Dutch to cull mink farms after corovirus cases – RTL https://www.agriculture.com/markets/newswire/dutch-to-cull-mink-farms-after-corovirus-cases-rtl [Accessed 8 June 2020]
  6. ProMED International Society for Infectious Diseases (2020) COVID-19 update (236): Netherlands (NB, LI) animal, farmed mink, spread, culling [online] https://promedmail.org/promed-post/?id=7427849 [Accessed 8 June 2020]
  7. ProMED International Society for Infectious Diseases (2020) COVID-19 update (230): Netherlands (NB, LI) animal, farmed mink, spread, control [online] https://promedmail.org/promed-post/?id=7420433 [Accessed 8 June 2020]
  8. Ministry of Environment and Food of Denmark (2020) Letter from the Danish Veterinary and Food Administration [online] https://www.oie.int/fileadmin/Home/eng/Our_scientific_expertise/docs/pdf/COV-19/Denmark_Sars-CoV-2_17-06-2020.pdf [Accessed 3 July 2020]
  9. ProMED International Society for Infectious Diseases (2020) COVID-19 update (317): Netherlands (NB) animal, farmed mink, spread [online]  https://promedmail.org/promed-post/?id=7578453 [Accessed 17 July 2020]
  10. Ministry of Environment and Food of Denmark (2020) Letter from the Danish Veterinary and Food Administration: Update 1 on the COVID-19 situation in Denmark [online] https://www.oie.int/fileadmin/Home/MM/Update_1_Letter_to_OIE_about_the_COVID-19_situation_in_Denmark.pdf [Accessed 17 July 2020]
  11. BBC News (2020) Coronavirus: Spain orders culling of almost 100,000 mink [online]  https://www.bbc.co.uk/news/world-europe-53439263 [Accessed 17 July 2020]
  12. ProMED International Society for Infectious Diseases (2020) COVID-19 update (477): animal, Sweden, mink, spread, genotyping [online] Available at: https://promedmail.org/promed-post/?id=7924269 [Accessed 9 November 2020]