Cats and COVID-19: No Need to Panic Yet
Dr. Ernie Ward
April 2, 2020
NOTE: This video contains complex (and potentially confusing) medical research findings. It is intended primarily for veterinary professionals or interested pet owners. I strongly encourage you to read the original study results linked below. Thanks!
A new study concludes cats can be infected with SARS-CoV-2, the virus that causes COVID-19 in humans. They can also spread the coronavirus to other cats, at least according to a small research study from China published March 31, 2020.
There is no evidence that cats (or dogs) can transmit the virus to people, other than serving as an accidental fomite, in the same way you could potentially contract COVID-19 from a contaminated door handle or handrail.
The overwhelming consensus is that our pets pose no particular threat to infecting us with the novel coronavirus.
What is most interesting about this latest research and a recent feline case study from Belgium is that cats appear to be able to become infected with SARS-CoV-2 and potentially exhibit symptoms of COVID-19.
This isn’t a surprise for veterinarians; cats were also discovered to be weakly susceptible to SARS, the human coronavirus that caused a global pandemic in 2003, and no evidence of cat-to-human transmission was found. This is different than dogs, a species that, based on all scientific evidence, cannot actively infect other dogs (or people) or experience COVID-19 symptoms.
In the latest study, five 8-month old cats were intranasally inoculated with SARS-CoV-2. Three of the infected cats were placed in separate cages beside an uninfected control cat. This was done to determine if respiratory droplets could spread between the cats and cause infection.
The remaining two inoculated cats were kept in separate isolation and euthanized 6 days later for testing. SARS-CoV-2 RNA was found in both cats’ nasal passages, soft palates, tonsils, the trachea of one and small intestine of the other. Notably, neither had viral RNA in their lung tissues. Infectious virus was also present in the nasal passages, tonsils, and soft palates of both cats.
On day 3, two of the three other inoculated cats had viral RNA in their feces, and was found in all three by day 5. In one of the three uninfected control cats housed adjacent to an inoculated subject, fecal viral RNA was discovered on day 3.
The remaining cats were euthanized on days 11 and 12. All of the SARS-CoV-2 inoculated cats had viral RNA in their nasal passages, soft palates, tonsils, and trachea. The sole control cat with fecal viral RNA was also found to have human coronavirus RNA in its nasal passages, soft palate, tonsils, and trachea, indicating cat-to-cat infection by respiratory droplets was possible. The remaining two control cats had no evidence of SARS-CoV-2.
Scientists also concluded that the amount of human coronavirus virus they measured in the study cats was most likely too low to pose an infectious threat to humans, similar to earlier SARS findings.
The researchers also evaluated five 3-month old beagles with two control dogs in a similar manner. Only three of the inoculated dogs showed fecal viral RNA, and none of the dogs had infectious virus in any organ after necropsy. Only two of the study dogs seroconverted to SARS-CoV-2, meaning they produced antibodies against the virus. Overall, these results indicate dogs appear to have low susceptibility to SARS-CoV-2.
The difference between dog and cat COVID-19 responses may be in the cellular receptor the coronavirus uses to infect cells. SARS-CoV-2 uses a cellular entryway named ACE2, most commonly found within the lungs, kidney, and digestive tract. A separate genetic analysis study shows that cats appear to have higher gene expressions of ACE2 receptors in their skin, ear tips, lungs, and retina, while dogs were higher in the skin and retina. Interestingly, the Chinese researches found cats and ferrets to have the highest expression of ACE2 receptor genes in the lungs, indicating they may be better laboratory models for SARS-CoV-2 than rodents. Mice were found to have relatively few ACE2 receptors in their lungs, suggesting they may not be good research candidates for COVID-19, while ferrets may prove to more closely track human coronavirus infections.
The researchers also concluded that human ACE2 receptor expressions were most common in male testes, small intestine, heart, kidney, and lung. These findings are consistent with the global COVID-19 clinical observations so far.
My interpretation and advice remain unchanged:
Dogs and cats pose little, if any, threat of transmitting COVID-19 to people.
If someone in your house becomes infected with coronavirus, they should keep isolated from any dogs or cats as much as possible.
Social distancing applies to our pets, especially during dog walks. Avoid contact with strangers or people potentially exposed to coronavirus.
After any contact with other people or certainly any exposed or infected person, bathe your pet.
More frequent bathing is a good idea after walks in areas where other people may have been.
Keep your cats indoors, eliminating the rare risk of contracting coronavirus when roaming.
Wash your hands after touching any dog or cat.
More research is needed to assess the role of animals, including cats, as natural reservoirs of SARS-CoV-2. Based on the limited data available and from decades of SARS research, cats have not been shown to be a vector for human COVID-19. Keep your cats indoors, practice good hygiene, and keep updated for future developments. I know I’ll continue to snuggle with my cat, especially during these stressful times. Stay safe and give your pets a hug from me!
Link to Susceptibility of ferrets, cats, dogs, and different domestic animals to SARS-coronavirus-2 (pre-print, pre-peer review submission):
https://www.biorxiv.org/content/10.1101/2020.03.30.015347v1.full.pdf
Link to Atlas of ACE2 gene expression in mammals reveals novel insights in transmission of SARS-Cov-2 (pre-print, pre-peer review submission):
https://www.biorxiv.org/content/10.1101/2020.03.30.015644v1.full.pdf+html