Cats are susceptible to SARS-CoV-2. That’s been shown experimentally and in a limited number of documented natural infections. However, there’s still a lot we need to know to better understand the feline and human health implications of this virus. While limitations of experimental studies always have to be considered (since they’re based on an artificial situation), they can answer some questions a lot quicker than field studies.
A new correspondence in the New England Journal of Medicine (Halfmann et al. 2020) provides a bit more information about this virus in cats, largely supporting what’s been reported before . I found it pretty surprising to see this report in a prominent human medical journal, since it only involves cats. I also found it surprising how superficial the information was. I guess they were trying to squeeze everything into a letter to the editor, but they sacrificed providing good information for publication in a high profile journal. They did provide more details are in the supplementary appendix file, but there are still lots of gaps.
The study looked at experimental infection with SARS-CoV-2 in three cats:
- The day after the three cats were inoculated with the virus, another cat was co-housed with each of them.
- There is no mention of what, if anything, they did to make sure there was no viable virus on the haircoat of the infected cats after experimental inoculation.
- Nasal and rectal swabs were collected daily to test for the virus.
- By day 3, virus was recovered from all inoculated cats.
- There is no mention if the virus was found on the nasal swabs, rectal swabs or both.
- It appears that the infected cats were healthy, although how they were monitored isn’t clear beyond saying they didn’t lose weight or have abnormal body temperatures. However, their graph shows 2 of 3 infected cats had a 1C temperature jump by 24 hours post-infection, and one of the co-housed cats seemed to spike a fever on day 7.
- Virus was ultimately detected in all three cats co-housed with the inoculated cats.
- Virus was detectable for several days in all cats (see graph below).
- All cats developed antibodies to the virus, further confirming they were truly infected.
My take home messages from this study aren’t really anything we didn’t know before, but it’s still useful confirmation:
- Cats can be infected with SARS-CoV-2.
- Infected cats don’t necessarily get sick.
- Cats can spread the virus to other cats.
Since cats can spread the virus to other cats, the logical question is whether they can spread it to people. It’s logical to assume that they could, so it makes sense to take some basic precautions around exposed cats (like we’ve been saying for months). This is nothing new or scary, just a reminder to keep using some common sense preventive measures.
As the authors state, earlier reports, “coupled with our data showing the ease of transmission between domestic cats, [show] there is a public health need to recognize and further investigate the potential chain of human–cat–human transmission.”