Ngozi and Kibo, 22 and 23, developed a cough, lethargy and a runny nose at their home in Colorado in November. Soon it was determined their ordinary symptoms were signs of a world first: These residents of the Denver Zoo became the world’s first hyenas known to be infected with COVID-19.
The milestone, nearly 20 months after the start of the pandemic, is part of a pattern in recent months. On October 6, a binturong (“bearcat”) and a fishing cat tested positive at the Chicago Zoo, followed a week later by a coati. Two hippos from a zoo in Belgium were killed on December 5. All were the first of their kind to contract the virus.
They are now part of a group of 315 animals from 15 species in the United States confirmed to have SARS-CoV-2, the virus that causes COVID-19. The list also includes cats, dogs, tigers, lions, snow leopards, gorillas, otters, puma, ferret, white-tailed deer. (Infected mink, almost all on fur farms, are not included in the total).
What do we know about animals that can contract the virus? And what does this mean for them and for us?
Are some animals more sensitive?
These cases mainly affected carnivores. (Carnivores belong to an order of mammals which includes wild and domestic cats, dogs and wolves, bears, etc. Carnivore is an umbrella term for any animal that primarily eats meat. Sharks, for example, are carnivores but not carnivores).
Hyenas, binturong, coati and fishing cat are all carnivores, as are domestic felines and big cats, which have tested positive since the start of the pandemic.
That doesn’t necessarily mean carnivores are more sensitive – there isn’t enough data to judge yet, says Elizabeth Lennon, a veterinarian at the University of Pennsylvania School of Veterinary Medicine.
It’s a different story with the big cats, however. Ninety have tested positive in the United States, according to the United States Department of Agriculture (USDA). âI think if you look at the situation in all the zoos, you can confidently say that there is an increased susceptibility to clinical disease in the big cats,â Lennon said.
Some species are more sensitive to certain variants.
Take mice. They escaped the original SARS-CoV-2 virus, but we know they can be infected with the beta variant.
As variants emerge in humans, the virus could expand its host range – mutate to infect more species and potentially circulate “silently” among them, creating a new reservoir, explains Diego Diel, professor. associate and director of the virology laboratory at Cornell University’s College. veterinary medicine.
But the reverse is also true: It is possible that new variants are harmless to certain species, says Diel, because “as the virus becomes more efficient at transmitting between humans, it may become less efficient at moving between animals. “.
So far, there is no evidence that with the exception of mink, any species, including domestic animals, can transmit the virus to humans, or that variants have appeared after mutating into another species.
Most animals do not appear to get seriously ill from COVID-19.
The majority of animals in the United States, including Ngozi and Kibo, the hyenas, have shown only mild symptoms and have made a full recovery.
The most severe cases have occurred in snow leopards and mink. At Lincoln Children’s Zoo in Nebraska, three snow leopards died in November from complications from COVID-19. It is not known if they had any underlying conditions. And thousands of mink have died on 17 fur farms in Utah and other states. Millions more have been euthanized on farms in Denmark and the Netherlands.
Buddy, the first dog to be confirmed positive for COVID-19 in the United States, died in July, but he likely had lymphoma, which experts say may have played a role.
Studying COVID-19 in animals is important.
âAs soon as you have more than one species that can maintain and transmit a virus, this also has important implications in control strategies and prevention strategies,â explains Diel. It is therefore crucial to know whether a species could become a reservoir of the virus.
âAnimals present different and unknown risks,â says Lennon. âIt is certainly important that surveillance continues in many different species because the virus is so widespread,â which increases exposure and transmissibility.
The tests are biased towards animals that have shown signs of disease.
The number of animal infections in the United States likely exceeds the 315 recorded cases, Diel says. If animals do not show symptoms, they are unlikely to be tested, making it difficult to learn more about potential silent spreaders, animals that can contract and transmit the virus without ever showing symptoms. .
White-tailed deer are a species that scientists are keeping a close eye on. This year, a study analyzing the blood of more than 600 deer in four US states found antibodies to the coronavirus in nearly 40% of the samples. Last month, COVID-19 was detected in three deer in Quebec, Canada. None of the animals seemed sick.
There is no evidence that deer can transmit the virus to humans or other species. But the specter of a silent reservoir makes scientists think. âThat’s why everyone is so concerned about these deer studies,â Lennon says. If a virus spreads quietly and even mutates in a large animal population, “it is much more difficult to control and eradicate.”
The overwhelming majority of zoo animal cases in the United States have been reported by accredited facilities that have strict health protocols.
The Bronx Zoo, where the first tigers and lions tested positive in April 2020, the San Diego Zoo Safari Park, where the first gorilla tested positive in January 2021, and the Lincoln Children’s Zoo, home to the three leopards of the Snows Deceased, are all members of the Association of Zoos and Aquariums (AZA), a US nonprofit organization that sets standards for the care and safety of animals.
AZA’s stricter veterinary protocols mean that caregivers are more likely to detect the disease in their animals and conduct tests, said Dan Ashe, president of AZA. âThey’re constantly watching the animals,â he says. âIf something doesn’t look right, they ask the questions. “
Standard practices during the pandemic include wearing personal protective equipment and minimizing close contact with animals, according to veterinarians at several AZA-accredited zoos with positive cases. âOur members have taken many steps to keep themselves safe, and we are still seeing infections,â says Ashe. “So it’s hard to believe that this doesn’t happen in other establishments where the contact is much more – shall we say – liberal.”
We have no idea what might happen in “roadside” zoos that offer visitors hands-on interactions with animals.
Many roadside zoos, such as the ones featured in Netflix King tiger, offer direct contact with animals, especially lion cubs and tigers, species known to be susceptible to the virus. These zoos must be licensed by the USDA to display animals but are not accredited by the AZA, which does not allow contact between big cats and the public. (Read about King tiger fans who have waited for hours for the chance to pet baby tigers during the height of the pandemic.)
The standards of care set by the USDA are much lower than those of the AZA, and roadside zoos are known for their lax veterinary care and safety protocols. It is not known whether big cats in roadside zoos or at pet facilities have been tested for the virus or have died from it.
âI think the risk is higherâ in roadside zoos, says Diel. âA transmission requirement is close contact, and in any situation where youâ¦ increase the number of people in contact with animals, it increases the risk. “
We need more data and we need to keep studying.
Although COVID-19 is primarily a human disease, Lennon says, the growing number of species known to be susceptible to the virus should be a call to action. âWe need to do a lot of monitoring in different species and in new variants,â such as Omicron, she said. “This virus from the start surprised everyone at every turnâ¦ We cannot let our guard down at any point, as we continue to learn over and over again.”
How can you help
- If you test positive for COVID-19, isolate yourself from your pets, as you would from other humans. If your pet appears ill, call your veterinarian.
- Avoid touching or approaching big cats in petting zoos to prevent the spread of the virus. We know that tigers and lions are susceptible to COVID-19. (And Cubs’ petting poses other risks to animals as well.)
- Get vaccinated if you haven’t already. Vaccination is proven to reduce the spread of COVID-19, protecting humans and animals.