Domestic cats and dogs are much more likely to get Covid-19 than their stray conspecifics – and cats are more susceptible to the virus than their dog-like conspecifics, new research suggests.
In the new study, researchers from the University of Guelph in Ontario tested 48 cats and 54 dogs from 77 different households that had a positive Covid-19 case in the past nine months. They compared the results to those of 75 dogs and cats living in an animal shelter and 75 stray cats seen in an inexpensive veterinary clinic. The preliminary results, which have not yet been published in a peer-reviewed journal, will be presented at the European Congress on Clinical Microbiology and Infectious Diseases in July.
Full coverage of the coronavirus outbreak
Almost 70 percent of house cats and more than 40 percent of house dogs tested positive for antibodies, compared to just under 10 percent of dogs and cats from the animal shelter. In the case of stray cats, this number fell to 3 percent. The majority of the cases were mild and only 20 percent of the dogs and 30 percent of the cats had symptoms. Dogs tended to have poor appetite and sluggishness, while cats had runny nose and difficulty breathing.
The researchers also found that the amount of time a pet owner spent with their dog didn’t affect their chances of getting Covid-19, but cats didn’t. The more time cats spent with their human companions, the more likely they were infected. In particular, cats that slept on their owner’s bed were at higher risk of infection.
It’s still unclear why cats are more likely to get Covid-19 than dogs, but some research has found that cats have a higher capacity for the virus to grow in their cells than dogs or even laboratory mice, making them more susceptible.
“It could be something as simple as most dogs have long noses, or the virus doesn’t bind as well to the receptor in dog cells or something with the immune system,” said Sue VandeWoude, professor at Colorado State University College of Veterinary Medicine Biomedical Sciences who was not involved in the new research.
Since the most likely route of infection is from humans to pets and not the other way around, pet owners shouldn’t worry about getting Covid-19 from their pets, said Dorothee Bienzle, professor of veterinary pathology at the University of Welfen and co-author of the study.
In fact, a second study, also presented at the July science meeting, concluded that humans are likely to infect their pets. This study by researchers from the University of Utrecht in the Netherlands looked at 311 cats and dogs in 196 households with a Covid-19 positive person. Just under 1 in 5 pets tested positive for antibodies, and a small handful – six cats and seven dogs – had a positive PCR test, which means they had an active infection.
Download the NBC News app for full coverage of the coronavirus outbreak
People with Covid-19 should take steps to protect their pets, Bienzle said. That means wearing a mask and avoiding contact with your cats and dogs as much as possible.
“At this point we should assume that if infected, our pets are also susceptible and should be treated like any other member of the household,” she said.
According to VandeWoude, two questions remain: Can pets infect people who are not yet infected, and if they do, the virus mutates, as it did in a mink farm in Denmark last year.
Mutations are more likely to occur when a virus is transmitted rapidly between many hosts, such as livestock or wildlife populations, or people who live in densely populated cities. Transfers between a pet and a human, on the other hand, are less of a concern.
“Even so, every time there is a spillover event, from animal to human, there is always the risk of it getting more virulent, so we need to keep that in mind,” said VandeWoude.
Follow NBC HEALTH on Twitter and Facebook.