It is generally accepted that SARS-CoV-2 (COVID-19) has spilled into the human population from a wildlife reservoir, likely bats. In recent months human to ferret, ferret to ferret, human to mink, mink to mink and mink to human transmission have all been demonstrated. The ability of an animal to become infected with COVID-19 is a result of the shape of certain receptors on cells in the lining of the respiratory tract (ACE2 receptors). The shape of these receptors tends to be similar in related species, meaning the species closely related to ferrets and mink could potentially be at risk of infection.
Ferrets have shown to become infected by human owners who are COVID-19 positive. These ferrets become unwell, with a fever, and loss of appetite. While unwell ferrets can pass infection to other ferrets via direct contact, there has been no proven transmission from a ferret back to a human.
Mink have been infected via contact with infected workers in an intensive farming situation. These mink become unwell, and an increased mortality rate is noted. Mink can infect other mink via direct (same cage) and indirect (adjacent cage) contact. Within the captive mink population, a mutation in SARS-CoV-2 occurred, which has been passed back into the human population. Humans are able to pass this infection to other humans. Immunity to the original SARS-CoV-2 does not give good immunity to the mink mutation form. Currently the mink mutation SARS-CoV-2 is not circulating in the UK, and 17 million mink in Denmark and the Netherlands have been culled in order to stop the spread of this mutation within the captive and to the wild mink population.
Within the wildlife rehabilitation situation, it may become important to understand the implications of SARS-CoV-2 potentially spilling into an alternative wildlife reservoir and to take appropriate steps to avoid this. Mustelids such as mink, polecats, otters, pine martens and weasels are all potential candidates, although those species that are more habituated to living near humans would present the greatest risk.
While the risk of spread into wildlife is small, we know from our experience with badgers and tuberculosis in the UK, and raccoon/skunk and rabies in the US that the potential for a wildlife reservoir should be avoided if possible. It is essential that wildlife rehabilitators take appropriate steps to avoid infection within their facilities.
Steps that a wildlife rehabilitation centre should consider:
- Isolating all ferrets/polecats from other mustelids.
- Any staff showing clinical signs should self-isolate, and the importance of these staff not coming into contact with mustelids (eg in a foster or hand-rearing situation) should be emphasised.
- Suitable PPE should be used in all cases and changed between mustelid patients.
- Cage furniture should not be shared between mustelid patients. Any cage furniture that is re-usable (such as bowls, litter trays) should be cleaned and then disinfected between patients. Cage furniture that cannot be adequately cleaned (ie anything wooden) should be discarded after use.
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