From a virus whose behaviour still involves more questions than answers, there has been another first: A Malayan tiger at New York’s Bronx Zoo has tested positive for SARS-CoV2. Four-year-old Nadia is believed to have caught the virus from a zoo employee, who had not shown symptoms.
So, humans can infect animals?
The virus came from an animal source and mutated; humans have since been infecting humans. It is theoretically possible for the virus to mutate again to survive in certain species after being transmitted by humans. The Bronx Zoo case suggests an employee spread the virus to the tiger, the US Department of Agriculture said in a statement. Several lions and tigers at the zoo, in fact, have shown symptoms of respiratory illness. The others were not tested to limit the potential risks of general anaesthesia.
What about domestic animals?
There have been a handful of cases of pets being infected; the indications are they caught it from humans. There have been reports about two dogs in Hong Kong — a Pomeranian and a German shepherd — testing positive. While their respective humans had COVID-19, the dogs themselves were not showing symptoms.
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In what has more context in the Bronx Zoo tiger testing positive, there has been a domestic cat, too, catching the virus, in Belgium. Unlike the dogs, the cat showed symptoms. After testing positive, it later recovered.
So, are cats at higher risk than dogs, and can they, in turn, infect humans?
Chinese researchers recently published a pre-print paper (not yet peer-reviewed) on this subject. They inoculated cats with the novel coronavirus, placed them alongside uninfected cats, and found that cats can transmit the virus to one other. The good news: the virus replicates poorly in dogs. There has been no evidence about cats infecting humans either.
There may be a possible explanation why felines are more susceptible. SARS-CoV2 infects respiratory cells after entering through a protein, which lies on the surface of the cells. Called ACE2, the protein in felines resembles ACE2 in humans, Steven Van Gucht, the Belgian government’s spokesperson for coronavirus, told Live Science after the cat caught the virus.
As it is, cats are susceptible to feline coronavirus, which is common but generally asymptomatic, although it can cause mild diarrhoea, according to Cornell University.
Should you worry about your pets?
After the tiger tested positive, the US Department of Agriculture advised that people with COVID-19 restrict contact with animals, just as they would with other people. It did not recommend routine tests for pets.
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The Bronx Zoo case led to India’s Central Zoo Authority alerting all zoos to monitor animals 24×7 for signs of abnormal behaviour. It mentioned cats, ferrets and primates.
Primates are of particular concern. In a recent commentary published in Nature, a group of 25 scientists called for urgent discussions on the need to severely limit human interaction with great apes in the wild, and in zoos, until the risk of COVID-19 subsides.
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