Coronavirus in a dog: One Pomeranian dog from Hong Kong managed to become famous, after scientists discovered traces of coronavirus on it. After confirmation that the dog owner was positive for the virus COVID-19, the dog was quarantined. They followed many tests performed on fluids collected from the dog's nose and throat and revealed coronavirus.
The results, of course, have raised many questions and concerns. Can our dogs catch the virus? Do we have to worry about our pets getting sick? Could dogs spread the coronavirus to humans?
A positive coronavirus result in this dog simply means that a small viral genome has been detected in a sample. PCR (a test used to detect genetic material) is an extremely sensitive test method, but it is not able to tell if the coronavirus infected the dog or if the dog had just licked infected surfaces in the house.
We do not yet know how long COVID-19, called SARS-CoV-2, can survive in the environment. A study for other coronaviruses states that they can remain contagious for several days if the temperature and humidity are correct. So since we do not even know if the virus that was detected was contagious or not, we have no idea whether a virus reproduced in that particular dog.
We know that SARS-CoV-2 is transmitted by droplets, so it is very likely that dogs could function as "dirty tissues" carrying the virus around if proper hygiene is not maintained.
While the COVID-2 is in the spotlight today, in fact there are many different types of coronaviruses, and coronaviruses that infect dogs are not new.
Although canine coronaviruses differ from SARS-CoV-2, dogs are clearly susceptible to this family of viruses. Nevertheless, there are no previous cases of human coronaviruses infecting dogs or vice versa. In order for a type of virus to jump, there are many obstacles that must be overcome.
The main barrier that stops the virus from infecting a new type of animal is the surface of the host cell. To infect dog cells, SARS-CoV-2 must be able to bind to dog receptors. Thanks to a quick research, we know that SARS-CoV-2 uses proteins ACE2 and TMPRSS2 (PDF) to enter the cells. Dogs have both of these proteins, but they are not identical to humans, so the virus may not be able to use them.
Assuming now that the virus can bind, enter and reproduce in dog cells, then it makes sense for dog owners to worry about whether their dogs will get sick. The reassuring thing is that Pomeranian dog from Hong Kong has not shown any worrying sign. Although it is an isolated case, there is no reason to believe that the human virus can cause disease in dogs at this stage.
Could dogs transmit SARS-CoV-2 to humans?
In order for a dog to transmit the coronavirus, the virus must reproduce in dogs and be present at fairly high levels in the body. However, very low levels of the virus were detected in Pomeranian. What levels does a person need to become infected? We do not know yet.
We know about various other viruses that, although it is theoretically possible to transmit them from person to dog, are much easier to spread from person to person. We know that dogs are sensitive to the human neurovirus, which causes vomiting and diarrhea.
However, despite the millions of cases of this virus each year, only one case of human-to-dog transmission has been reported. Complete genome sequencing was crucial in this case and is probably needed to definitively demonstrate whether dogs can be infected with SARS-CoV-2.
But even if the worst-case scenario is true and the corona can be bred in dogs at reasonable levels, it is safe to assume that you are much more likely to be infected by your neighbor than by your dog. However, it is essential that there is good hygiene around each pet.
This article was republished by The Conversation of Sarah L Caddy, Clinical Research Fellow in Viral Immunology and Veterinary Surgeon, at University of Cambridge licensed under Creative Commons. Read it original article.