A tiger at New York City’s Bronx Zoo has tested positive for the novel coronavirus, officials at the US Department of Agriculture said Sunday, raising new questions about how the virus that causes Covid-19 spreads in animals, and whether other animals are at risk of becoming infected with the virus.
The Bronx Zoo’s tiger — a 4-year-old Malayan tiger named Nadia — is the first animal in the US and the first non-domesticated animal globally to have a confirmed Covid-19 case. At least two pets, a cat and a dog, were infected in Hong Kong; and a cat in Belgium is also believed to have had the virus. All of the pets were owned by people with confirmed Covid-19 cases.
Zoo officials believe the cat — as well as her sister, two Amur tigers (also known as Siberian tigers), and three African lions that are all exhibiting similar symptoms — may have been infected by a caretaker who has the virus but is asymptomatic, given that the zoo has been closed to the public since March 16.
“It’s the first time, to our knowledge, that a [wild] animal has gotten sick from Covid-19 from a person,” Paul Calle, chief veterinarian for the Bronx Zoo, said Sunday.
Calle added that his team took samples from Nadia that were sent to scientists and veterinarians at Cornell University, the University of Illinois, and the USDA National Veterinary Services Laboratory. All samples tested positive. Animal testing for Covid-19 requires a specialized protocol that differs from the testing done in humans. For example, testing a tiger includes placing the big cat under anesthesia; the complexity of the procedure led zoo officials to decide only one cat should be tested.
The new confirmed case is a reminder that although scientists have worked rapidly to understand the new coronavirus there is still much that isn’t known about how the virus can and cannot spread between species — and how it spreads among animals that aren’t human.
Here’s what we know — and don’t — about Nadia, and how Covid-19 spreads in animals.
What we know
- The Bronx Zoo announced a 4-year-old Malayan tiger, Nadia, tested positive for Covid-19 on Sunday
- Six other animals at the zoo — all large cats — are believed to have the coronavirus as well
- All seven animals have exhibited a dry cough and decreased appetites
- None of the animals exhibited other symptoms seen in humans, including fever or shortness of breath
- Other than the two symptoms, the zoo said Nadia and the other cats believed to be infected are “bright, alert, and interactive with their keepers”
- Neither of the dogs that tested positive in Hong Kong — a Pomeranian and a German Shepherd — exhibited any symptoms
- The infected cat in Belgium, like the zoo’s cats, did exhibit symptoms, including diarrhea, vomiting, and respiratory issues
- The Belgian cat’s case was confirmed using samples from its feces
- For her test, Nadia was sedated with general anesthesia; samples were taken from the back of her throat, nasal cavities, and trachea. Molecular testing confirmed she has Covid-19.
- The dogs and cat lived with owners with Covid-19 and are believed to have been infected by their owners
- Similarly, Nadia is believed to have been infected by a caretaker who was asymptomatic, or who cared for the cats before exhibiting symptoms
- Animals are thought to be able to infect humans with the coronavirus in some cases; as SARS expert Jonathan Epstein told Vox’s Brian Resnick, experts believe the coronavirus may have originated in an animal market in China and could have first appeared in bats
- A study from Chinese researchers at the Harbin Veterinary Research Institute in China — that has received some praise from scientists but that was done under conditions that did not approximate those of the real world, had a small sample size, and has not yet been peer reviewed — found there is community spread among cat populations
- The same study found the same is not true of dogs
- There have, however, been no confirmed cases of a pet or animal in captivity infecting a human
- Because of this, the US Department of Agriculture (USDA) has recommended coronavirus testing be done on a limited basis in animals
- Nevertheless, the Centers for Disease Control and Prevention (CDC) requests those who deal with pets and other animals wash their hands after interacting with them and that pet owners and caretakers ensure their animals maintain proper hygiene