A tiger at New York City’s Bronx Zoo has tested positive for the novel coronavirus, in what is believed to be a case of what one official called “human-to-cat transmission, officials at the US Department of Agriculture said Sunday, raising new questions about how the virus that causes coronavirus spreads in animals, and whether other animals are at risk of becoming infected with the virus.
“Zoo Tiger Is Sick With the COVID-19, This is the first instance of a tiger being infected with COVID-19,” according to the federal Agriculture Department, which noted that although only one tiger was examined, the virus appeared to have infected other animals as well.”
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 verified 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 the virus. All of the pets were owned by people with verified COVID-19 cases.
Zoo officials believe the Zoo Tiger Is Sick With the COVID-19 — as well as her sister, two Amur tigers, and three African lions that are all showing similar signs — may have been affected by a keeper who has the virus but is asymptomatic, given that the zoo has been shut down to the public since March 16.
“There is no evidence that other animals in other areas of the zoo are showing symptoms,” the Agriculture Department said.
The tiger was the only animal-tested because the procedure involved general anesthesia, the Agriculture Department said. While there were other tigers and lions displaying similar symptoms, the veterinarian wanted to limit the potential risks of general anesthesia to one creature, it said.
“We had a sick tiger and we needed to treat the tiger and know what the cause of the illness was so we could care for it,” Dr. Calle said.
A pet cat in Belgium recently tested positive for the coronavirus, but the American Veterinary Medical Association said that not enough was known to turn the current view that neither cats nor dogs appear to be able to pass the virus to people.
Here’s what we know — and don’t — about Nadia aka the infected tiger, and how Covid-19 spreads in animals.
What we know
- The Bronx Zoo announced a 4-year-old Malayan Zoo Tiger Is Sick With the COVID-19, Nadia, tested positive for COVID-19 on Sunday
- Six other animals at the zoo — all large cats — are believed to have the COVID-19 virus as well
- All seven animals have displayed a dry cough and low interest in appetites
- None of the animals showed other symptoms noticed in humans, including fever or shortness of breath
- Other than the two signs, the zoo said Nadia and the other cats thought to be infected are “bright, alert, and interactive with their wardens”
- Neither of the dogs that tested positive in Hong Kong — a Pomeranian and a German Shepherd — showed any symptoms
- The infected cat in Belgium, like the zoo’s cats, did display symptoms, including diarrhea, vomiting, and respiratory problems
- The Belgian cat’s case was confirmed using specimens from its feces
- For her test, Nadia was sedated with common anesthesia; samples were taken from the
- back of her throat, nasal cavities, and trachea. The molecular examination confirmed she has COVID-19.
- The dogs and cat lived with owners with COVID-19 and are considered to have been infected by their owners
- Similarly, Nadia is assumed to have been infected by a keeper who was asymptomatic, or who cared for the cats before showing symptoms
- Animals are thought to be able to affect humans with the coronavirus in some cases; as SARS expert Jonathan Epstein told Brian Resnick, experts think the coronavirus may have started 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 got some praise from scientists but that was done following 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 a community spread amongst cat populations, the same study found the same is not true of dogs
- There have, however, been no verified cases of a pet or animal in captivity infecting a human
- Because of this, the US Department of Agriculture (USDA) has suggested coronavirus testing be done on a restricted basis in animals
- Nevertheless, the Centers for Disease Control and Prevention (CDC) requests those who deal with pets and other creatures wash their hands after interacting with them and that pet owners and keepers ensure their pets maintain proper health
What we don’t know
- Why one Amur tiger that lived with the Bronx Zoo’s other four affected tigers has not shown any symptoms — it is not clear whether this tiger is asymptomatic or does not have the coronavirus
- Whether tigers and lions are at bigger risk of infection than other creatures
- Why the Bronx Zoo’s other large cats have not shown symptoms
- Whether infected cats display symptoms and dogs do not
- Whether cats really are more easily affected than dogs (as the Harbin study suggests) and if this is why a mixed-breed dog that lived with the German Shepherd tested negative for the virus
- Scientists like Linda Saif have noted other coronaviruses, like bovine CoV, can infect various species. But whether the coronavirus that causes COVID-19 can move from animal varieties to animal varieties (for instance, if it could move from a lion to an elephant) is not yet realized.
- It also is not yet clear whether transmission in animals must occur from humans — that is, whether the Bronx Zoo’s cats gave it to one another or if all exhibiting indications were infected by their keeper
- Whether COVID-19 diseases among animals make it more likely this coronavirus will become a yearly one or whether animals might serve as carriers that could lead to a resurgence of the virus; this is something scientists are investigating
- Experts currently do not believe pets can transmit the virus to humans — but whether this remains the case is currently poorly understood