A new scientific report confirms that cats and dogs can be infected by thenovel coronavirus, and that neither animal is likely to get sick. Cats,however, do develop a strong, protective immune response, which may make themworth studying when it comes to human vaccines.

There is still no evidence to suggest that pets have passed the virus tohumans, although cats do shed the virus and infect other cats.

Infected dogs in the new study didn’t produce the virus in their upperrespiratory tracts and didn’t shed it at all, although some other studies havefound different results. Neither the cats nor the dogs in the study showed anyillness.

The authors of the report in the Proceedings of the National Academy ofSciences published Tuesday point to real world transmission to emphasize whypets are not a significant concern for human infection. Angela M. Bosco-Lauth,Airn E. Hartwig, Stephanie M. Porter and other researchers at Colorado StateUniversity’s College of Veterinary Medicine and Biomedical Sciences note thatwhile millions of humans have been infected with the virus worldwide and 1million have died, there are only a handful of reports of pets that havebecome infected naturally.

If cats can shed the virus, why aren’t they infecting people, which is atheoretical possibility? One reason is that the number of humans who havecontracted the virus is so large, and they are the ones giving it to cats.Another possible reason is that infection in everyday life is very differentfrom infection in the lab.

In the new experimental work, scientists inserted pipettes in the nasalcavities of cats and dogs to give them the virus. The animals receivedanesthesia before the procedure, but the point is that this doesn’t happen inmost homes. Later, other cats were put into close contact with the infectedcats, who were shedding virus.

Does this happen in the real world? There is some evidence of street cats inWuhan, China, having been exposed to the virus. But it may be that in theUnited States, because many cats are kept indoors, transmission is minimal.

Or, Bosco-Lauth said, cat infection with the virus could be relatively commonwithout humans noticing, because of a lack of symptoms. “Those cats that wereinfected in the experiment?” she said. “You would never have known.”

Cats might also pass the virus on to wildlife. Bosco-Lauth said that an as yetunpublished work shows that deer mice may become infected with the novelcoronavirus.

Also, outside a lab, infection depends mainly on breathing in viral particlesfrom an infected person and normal contact doesn’t necessarily translate intoinfection for animals. Ferrets have been shown in the laboratory to besusceptible to infection with the virus, and to spread it to other ferrets.

But scientists at Tufts reported, in a paper that has yet to be peer-reviewed,that in one house with 29 pet ferrets and two humans with COVID not one ferretbecame infected with the virus.

The 29 ferrets roamed freely in the house, and both human adults were illenough with COVID to show symptoms, so there was ample opportunity forinfection. Kaitlin Sawatzki, a virologist at Tufts University and one of theauthors of the ferret paper, said, “Isn’t that incredible? It was a beautifulnatural experiment.”

The researchers concluded that there could be genetic barriers to infectionthat are overcome in a lab with concentrated doses of virus. Minks, which arein the same family as ferrets, appear to be very easily infected, and to getsick from the disease. Researchers have also reported transmission fromanimals to humans at mink farms in the Netherlands in a paper not yet peer-reviewed. Sawatzki said the paper showed, “very strong evidence of multiple,independent mink-to-human transmission events.”

The Colorado State researchers advise keeping cats indoors, particularly if ahuman in a household has become infected, because they could spread it toother cats. Also, if a person with COVID needs to be admitted to a hospitaland has pet cats, Porter suggested, the cat’s caretakers should know toobserve social distancing as they would with a person.

The infected cats that showed immunity, Bosco-Lauth said, were animals thatwere infected by contact with other cats, not by pipette. And, she said theimmune response was stronger than in some other laboratory animals, althoughhow long that protection might last is completely unknown.

Source: James Gorman The New York Times

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