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A symptomatic cat in Belgium has tested positive for the novel coronavirus, but experts reiterate that there is no proof that animals can transmit the disease.
A cat in Belgium has become the third animal to test positive for the novel coronavirus, according to a report late last week in The Brussels Times. The cat reportedly contracted the virus from its owner, who had recently been to Italy and has herself tested positive for COVID-19.
The cat began showing clinical signs of the virus, including diarrhea, vomiting and difficulty breathing, about a week after its owner became ill, at which time a test of the cat’s feces and vomit revealed traces of the virus. Both the cat and its owner are currently on the mend.
This first case of human-to-cat transmission of COVID-19 has sparked more questions about whether and how pets can become infected with or serve as vectors for the novel coronavirus—and how veterinary professionals should address the issue with concerned clients. For answers, dvm360 spoke with Jane Sykes, PhD, BVSc (Hons), chief veterinary medical officer at the University of California, Davis, School of Veterinary Medicine Veterinary Medical Teaching Hospital and founder of the International Society of Companion Animal Infectious Diseases.
dvm360: What do you think it means that this cat showed clinical signs of COVID-19 while the dogs that tested positive in Hong Kong did not?
Dr. Sykes: During the 2003 severe acute respiratory syndrome (SARS) outbreak in Hong Kong, a small number of pet cats tested positive for the virus but none became sick. Ferrets could also become infected and did develop illness. Infection in dogs was not identified, but it is my understanding that widespread testing was not performed in dogs.
SARS-CoV-2, the virus that causes COVID-19, utilizes two receptors to enter human cells: the angiotensin-converting enzyme 2 (ACE-2) receptor and a type II transmembrane serine protease (this is similar to the original SARS virus in the early 2000s). The virus binding site on ACE-2 receptors in cats and ferrets are very similar to those of humans, so it would not be surprising if SARS-CoV-2 binds to ACE-2 receptors in cats and ferrets.
The canine receptor has a lower homology, which might explain why cats could be more susceptible to infection than dogs. However, given the low numbers of dogs and cats reported to be infected with COVID-19, it is impossible to say at this time whether cats are more susceptible to infection or clinical signs of disease. Recent studies in ferrets have shown that they can be infected with SARS-CoV-2 and develop clinical signs of fever, lethargy and cough. Ferrets could also transmit the virus to other, in-contact ferrets.
dvm360: Does this development change what pet owners with signs of illness should be doing to keep their pets healthy?
Dr. Sykes: The report of an cat infected does not change our recommendations. Currently, we don’t have enough information to know whether cats and dogs have the potential to infect humans. To date, all transmission has been human-to-human, after the initial jump from bats (most likely) to humans. In light of the report about the infected cat, the World Organisation for Animal Health (OIE) updated its Q&A page to note that although some examples of animal infections have been reported to the OIE, currently there is “no evidence to suggest that animals infected by humans are playing a role in the spread of COVID-19. Human outbreaks are driven by person-to-person contact.”
If dogs and cats can shed the virus, it is possible that the quantity of virus shed is too low for transmission to occur, especially if there are no signs of respiratory disease to create aerosols.
Because other infectious diseases can spread between animals and humans, it remains prudent to always exercise good hygiene when people, especially children and the immunocompromised, are around animals. This includes washing your hands (properly) after touching, feeding or cleaning up after your pet, avoiding rough play (especially between children and animals) and not allowing pets to sleep in bed with immunocompromised people or lick faces, wounds or healthcare devices.
Pet owners who a have tested positive for COVID-19, or those who are highly suspected to have it but have not been tested, additional precautions are warranted. These owners should limit contact—ideally having someone else in the household care for the pet—and wear a face mask. The pet should be quarantined with the owner and any signs of illness reported to their veterinarian.
Critically, we need to inform owners that it is important not to over-react and disconnect from their pets. The importance of the human-animal bond and its positive healthcare effects cannot be overestimated. Veterinary clients should be made aware of health benefits of pet ownership, including reductions in mental illness and cardiovascular disease, decreased blood pressure and improved self-esteem in children.
Owners should be advised not to panic about the possibility of pet infection and transmission, and instead enjoy all the positive healthcare benefits of the bond they have with their pets. On the one hand, restriction of human movement is likely to reduce adoption of pets from shelters, and more animals in need of homes may be euthanized as a result; on the other hand, there has been an increase in animal fostering by those looking for companionship during this shelter-in-place period, and this has raised some concerns that these animals will not receive adequate long-term care or will be abandoned when restrictions are relaxed.
dvm360: How should veterinarians advise clients who ask about the potential for their own pets to become infected with COVID-19?
Dr. Sykes: Veterinarians should remain vigilant and watch for signs in animals that might represent COVID-19. However, many animal diagnostic laboratories are not currently set up to test for this specific coronavirus. Some are equipped but are not offering testing at this time. The problem occurs when veterinarians have to perform the testing, because they would need to wear a special high-density face mask and a face shield. Face masks must be fitted in advance by a trained individual, and many veterinarians are not fit-tested on a regular basis, nor do they have high-density surgical masks on hand. Veterinarians should contact their local public health department or the CDC if an infected owner contacts them and requests that their pet be tested.
Should a dog or cat develop respiratory illness, pet owners need to remember that respiratory illnesses (‘kennel cough’ and ‘cat flu’) are extremely common in dogs and cats, especially those that board, attend doggy daycare or are acquired from shelter environments. Owners need to know that more than 10 different viruses and bacteria can cause these signs in dogs and cats, including a canine respiratory coronavirus that only infects dogs.
Any pet that develops respiratory illness is much, much, much more likely to be infected with a canine or feline respiratory virus or bacteria than with the novel coronavirus. These dog and cat viruses do not cause infections in people. Pet owners should be told to have their pet evaluated by a veterinarian if signs of runny nose/eyes, cough or sneezing develop, and they should not allow their pet contact with other animals in the meantime.
dvm360: Do you anticipate that cats, dogs or other pets could become vulnerable as the virus mutates?
Dr. Sykes: Coronaviruses are less likely than influenza viruses to mutate significantly. Based on what we’ve seen in the past with both human coronaviruses and influenza viruses transmitted to pets, it is more likely that cats, dogs and other pets will remain as “dead end” hosts rather than becoming more vulnerable to infection and disease.