In our ongoing seroprevalence (antibody) testing, we’ve seen that human-to-pet transmission of SARS-CoV-2 is probably not uncommon. However, we hadn’t yet found a pet that was positive for the virus on swabs in Canada . (Antibody testing tells us if the subject was previously infected, whereas testing swabs by PCR tells us if the virus is there at the time.) The reason for that is likely the short period of time that most infected animals shed the virus, and the logistics of sampling the animal at just the right time: someone has to get infected, then get tested, then get the test result, then call us, then we have to arrange to get a sample from their pet. We’ve assumed that we’re typically getting there too late to catch the pets when they’re shedding the virus.
Anyway, we’ve (finally) identified our first SARS-CoV-2 PCR-positive dog in Canada. The timing of the sample in this case probably accounts for that, since we got into the household a bit quicker than average.
Here’s the story:
The dog is an adult dog in the Niagara region of Ontario. Four of six people in the household had COVID-19, and we detected the virus from the dog’s rectal swab. We had a borderline test result on the dog’s throat swab too, although it was a low enough level that we can’t consider it a true positive.
The other dog in the household also had a borderline result on its rectal swab. My guess is it was truly infected but at a lower level or at the start or end of infection. We’ll follow up on both dogs with antibody testing in a few weeks. I’ll be surprised if both aren’t positive for antibodies.
Both dogs were healthy at the time of sampling and hadn’t had any obvious signs of disease.
What does this mean to the family members?
- Nothing (besides a unique story if they want to talk about it). The people in the household were all infected, and that was almost certainly human-to-human transmission. The dog(s) were infected by the owners and at that point didn’t pose any risk to the already-infected people.
What about other risks?
- The potential risk from pets is if they have contact with other people or animals outside the household, such as going to parks, kennels or veterinary clinics. We don’t know if dogs often shed enough virus to be infectious to others. The Ct result (the number of PCR cycles required for the test to detect the virus) was well under the cutoff in this case, so it was clearly positive, but looking at some human data, a Ct in the same range (from nasal swabs, so maybe not a perfect comparison) was associated with a low likelihood of culturing the virus from the sample, and therefore the risk of infectivity is likely also low.
- We’ve been going on the assumption that dogs are low risk for being infectious, and I don’t think this changes anything. However, we certainly can’t say there’s no risk from contact with an infected dog.
- There’s also a plausible risk of transmitting virus to neighbours through the fence (something we’ve seen with canine influenza and parainfluenza). That’s why our messaging has been to consider pets part of the household in terms of COVID-19 precautions. If people are being isolated, do the same with pets. It doesn’t matter if a dog or cat is infected if they don’t encounter anyone new.
So, from a research standpoint, we found it interesting, but it doesn’t change our messaging or mean there’s any more risk. This was the first confirmed positive for us, but it was certainly not actually the first positive dog in Canada. Lots of dogs have probably been infected before now and more will follow. We’re not testing every dog, and there is no need to do so. We don’t recommend people with COVID-19 get their pets tested outside of organized surveillance studies.
Don’t be afraid of animals in terms of COVID-19, but use common sense.
If you’re infected with COVID-19, limit your contact with anything with a pulse (not just people).
If your household is isolating because of COVID-19 exposure, make sure it includes the whole household. (If you wouldn’t lick your neighbour through the fence, don’t let your dog do the same to the neighbour’s dog… or kid.)