At the start of the COVID-19 pandemic, many major agencies took a head-in-the-sand approach to concerns about the potential for SARS-CoV-2 to infect different animal species. Fortunately,  over the last year a considerable amount of work has been done to help figure out the range of species that are susceptible to this virus, and shed some light on how animal populations might ultimately impact control of the virus, based on the potential for for infecting wildlife in particular (which comes with the risk of creating  wildlife reservoirs, and potential sources of new virus mutants). We now know of a few wildlife species that are susceptible (and can transmit) SARS-CoV-2, but there are so many wildlife species that our knowledge still just scratches the surface.

A recent study in pre-print posted on bioRxiv (Bosco-Lauth et al. 2020) looked at SARS-CoV-2 susceptibility in deer mice, bushy-tailed wood rats, striped skunks, cottontail rabbits, fox squirrels, Wyoming ground squirrels, black-tailed prairie dogs, house mice and raccoons. They did this by catching wild animals and experimentally exposing them to the virus, and then monitoring them in captivity. The study was pretty small (2-9 animals per species) but provides some useful information.

  • Deer mice, bushy-tailed woodrats, and striped skunks were susceptible to infection and shed the virus after infection, but they didn’t get sick (i.e. all infections were subclinical).
  • Cottontail rabbits, fox squirrels, Wyoming ground squirrels, black-tailed prairie dogs, house mice, and raccoons were not susceptible to infection.

That’s a bit of a mixed bag of results. The more wildlife species that are susceptible, the greater the potential problems.  We’re also more concerned about species that may have more contact with people (e.g. urban wildlife), those that live in large groups (where an infected individual can spread the virus to lots of others, potentially leading to sustained transmission in the population and creation of a reservoir), and those that can travel long distances (and could thereby carry the virus to new areas).

One highlight of this study for me is that raccoons were not susceptible, because they’re a very common, social wildlife species that lives in large urban centres where COVID-19 is (at the moment typically) rampant in people. Raccoons are one of the species I’ve been most concerned about in terms of a jump to wildlife.

The authors sum things up nicely “… we will undoubtedly continue to discover more susceptible species as the search for zoonotic reservoirs continues. COVID-19 is just the latest in a series of examples of how the human-wildlife interface continues to drive the emergence of infectious disease.”