There are various reasons we’re paying attention to SARS-CoV-2 in domestic animals. One important one is the potential for transmission of the virus from domestic animals to wildlife (because animals tend to have more direct contact with wildlife than people do). More specifically, we’re concerned about transmission to wildlife and then persistence of the virus in wildlife populations. For that to occur, you need susceptible wildlife species in large enough numbers and in close enough contact with each other for transmission of the virus to be sustained over time.
There is emerging information about the susceptibility of a few common wildlife species, so there is basis to those concerns and a need for more study.
A lot of the concern about SARS-CoV-2 in animals has revolved around mink. They’re highly susceptible and farmed mink are kept close together in large numbers. That’s a recipe for virus transmission (and potentially virus mutation, but that’s a different story). Farmed mink are also good at escaping. “Wild” mink found around mink farms tend to be escaped mink, or the offspring of escaped mink. Escaped farmed mink and wild mink can often be distinguished by certain physical characteristics including size (larger) and coat color (some farmed mink are bred for coat colours that don’t commonly occur in wild mink) .
When it comes to SARS-CoV-2, escaped mink create a few concerns. One is they could take the virus with them when they escape if they’re infected, creating another potential exit point from the farm for the virus. We don’t want that. The virus getting onto the farm is bad, but if it stays there and burns out, it’s not as big deal compared to the farm becoming a source of infection for other animals. Mink don’t shed the virus for long, so there would only be a short window of time after escape that a runaway mink would pose a transmission risk to other animals. Another concern is that if escaped mink continue to hang around the area (e.g. coming back to find food), they could become a longterm bridge for infectious diseases (e.g. SARS-CoV-2, and others) from the farmed mink to wildlife. Or worse, if escaped mink move between properties in areas where mink farms are close together, they could spread diseases from farm to farm.
That’s my long-winded introduction to the latest concern with mink, identification of SARS-CoV-2 in a wild mink in Utah, USA. Some mink farm outbreak investigations have included testing of wildlife around the farm. Infected cats have been found in Europe, and testing of wild mink around an affected farm in Utah identified an infected animal there too. They’re considering it the first case in a “free ranging, native wild animal,” which I guess is correct, but I’m not sure it’s much different than the spillover to cats on and around mink farms that’s been seen before. Not surprisingly, the viral sequence from the affected mink was identical to that of virus from mink on the nearby farm.
What does this mean? It’s too early to tell. One good thing about the SARS-CoV-2 virus is there’s no long-term carrier state, that we know of (at least outside of bats… that’s yet another story that still needs to be sorted out). If the virus makes it into wild mink or other wildlife, the relevance depends on whether that species can maintain and spread it. Infection of solitary species, species that have low population density, or species that aren’t very susceptible and don’t shed a lot of virus likely ends quickly. The concern is infection of large groups of susceptible animals, where infection might be self-sustaining in the population, circulating within and between groups (just like it does in people). At this point, we have no idea if that’s a realistic concern in wildlife, but it’s better to look and find out than just hope for the best.
Still, the best way to prevent this from becoming an issue is to prevent exposure of all animals as much as possible, especially wildlife. The best way to prevent that is to control it in people.