COVID-19 Is Also A Pandemic For Animals
Thought of as a human epidemic, COVID-19 is much more than that. SARS-CoV-2, the disease-causing virus, may infect a diverse and expanding variety of animals, both domestic and wild.
According to the U.S. Department of Agriculture, COVID-19 is also a pandemic for animals, like captive tigers, lions, gorillas, snow leopards, otters, and spotted hyenas. One positive case has been reported by zoo workers in the United States in a squirrel monkey, lynx, fisher cat, cougar, binturong, coati, and domestic ferret.
According to the USDA, only three wild species in the country—mink, mule deer, and white-tailed deer—have tested positive. There have been cases found in wild black-tailed marmosets, large hairy armadillos, and a leopard elsewhere in the world.
However, testing on wild animals is uncommon, and new research is starting to suggest that COVID-19 has likely affected a great number of other species. According to Virginia Tech disease ecologist Joseph Hoyt, “I suspect the dissemination to wildlife species is considerably larger than previously assumed.”
What are the effects of SARS-CoV-2 infection on such a diverse variety of species?
The receptor connection
A complex receptor termed ACE-2, which is present in all animals, is a significant factor. This receptor is crucial for controlling physiological processes including blood pressure.
When the SARS-CoV-2 spike protein enters the body, it begins to infect host cells by attaching to the ACE-2 receptor, which is present in large quantities in the sinuses and upper airways of humans and many other animals.
According to Craig Wilen, a virologist at Yale University, the physical structure of the ACE-2 receptor differs from vertebrate species to species relatively little in comparison to other proteins of the same nature. Nevertheless, there are enough minute differences that researchers first believed some mammals would be extremely rare to contract the infection.
But when creatures that were previously believed to be less sensitive have shown to be everything, that way of thinking has altered. It now seems that many, if not the majority of mammalian ACE-2 receptors are vulnerable and do not operate as a viral limiting factor.
Professor Rick Bushman, an expert on host-microbe interactions at the University of Pennsylvania School of Medicine, says that even if it isn’t a perfect match, “it appears like it’s good enough.”
Instead, there are probably a great number of additional factors—the specifics of which are essentially unknown—at work that affect vulnerability.
A vast range
We already know that the virus can infect and propagate among wild mink and white-tailed deer, and for both species, there has been at least one confirmed incidence of the virus traveling from people to the animals and back again. In addition to mink, domestic ferrets and golden hamsters also seem to disseminate the illness to one another easily in captivity.
Future research that was pre-publication in BioRxiv found likely cases of SARS-CoV-2 infection in a variety of wild species, including deer mice, raccoons, opossums, grey squirrels, white-footed mice, striped skunks, and more.
Hoyt, conservation scientist Amanda Goldberg, and Carla Finkielstein, who is a co-author of the study, were taken aback when they first discovered SARS-CoV-2 infection in Virginia opossums.
According to Finkielstein, “We were concerned because it suggests it’s jumping” to unrelated animals. According to Goldberg, “opossums are significantly different from humans physiologically.”
Opossums are marsupials that produce offspring the size of honeybees who nurse from teats in their mothers’ pouches. More than 150 million years ago, marsupials split from placental mammals, which contain many common mammals.
They reasoned that if SARS-CoV-2 can infect opossums, it is plausible that it may infect a wide range of animals. In fact, researchers in southwest Virginia discovered antibodies against SARS-CoV-2 in large amounts of six urban wildlife species. Additionally, they found positive PCR hits in two of these species as well as four other ones, including red foxes and bobcats. These hits are suggestive of infection but do not confirm it.
Another recently published article discovered evidence of the disease infecting 17% of the rats tested from the sewers of New York City. Additionally, research conducted by Yale University doctorate student Rebecca Earnest found that a tiny proportion of wild white-footed mice in Connecticut have also contracted the disease.
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