Monday, April 06, 2020

WCS: A Tiger at Bronx Zoo Tests Positive for COVID-19

Credit: © WCS














#15,174

Four days ago in Susceptibility of Ferrets, Cats, Dogs & Other Domestic Animals to SARS-CoV-2, we looked at preprint study by Dr. Hualan Chen et al. which looked at the susceptibility of a variety of domestic animals to the SARS-CoV-2, the virus that causes COVID-19 in humans.

They wrote:
We found that SARS-CoV-2 replicates poorly in dogs, pigs, chickens, and ducks, but efficiently in ferrets and cats. We found that the virus transmits in cats via respiratory droplets. Our study provides important insights into the animal reservoirs of SARS-CoV-2 and animal management for COVID-19 control.
This study came on the heels of a small number of reports of companion animals in Hong Kong (see AFCD: Dog Tests `Weakly Positive' For COVID-19 and Pet cat tested positive for COVID-19 virus) having contracted the virus from a human companion.
While there is currently no evidence that companion animals can - or have - transmitted the SARS-CoV-2 virus to humans, it is important to know which animals species are susceptible to the virus, whether it sickens them, and whether they shed the virus enough to be infectious to humans, their own kind, or any other species. 
Late yesterday, the Wildlife Conservation Society’s Bronx Zoo announced (see below) the first known tiger infection with SARS-CoV-2 - which, somewhat surprisingly - isn't the first time captive big cats (lions, tigers & leopards) have been featured in this pandemic-centric blog. 

First the press release, then a quick stroll through the curious history of dogs and cats and pandemic virus threats in the 21st century. 

A Tiger at Bronx Zoo Tests Positive for COVID-19

The Tiger and the Zoo’s Other Cats Are Doing Well at This Time

Bronx NY, April 5, 2020 -- The following information was released today by the Wildlife Conservation Society’s Bronx Zoo:
Nadia, a 4-year-old female Malayan tiger at the Bronx Zoo, has tested positive for COVID-19. She, her sister Azul, two Amur tigers, and three African lions had developed a dry cough and all are expected to recover.

This positive COVID-19 test for the tiger was confirmed by USDA’s National Veterinary Services Laboratory, based in Ames, Iowa.

We tested the cat out of an abundance of caution and will ensure any knowledge we gain about COVID-19 will contribute to the world’s continuing understanding of this novel coronavirus.

Though they have experienced some decrease in appetite, the cats at the Bronx Zoo are otherwise doing well under veterinary care and are bright, alert, and interactive with their keepers. It is not known how this disease will develop in big cats since different species can react differently to novel infections, but we will continue to monitor them closely and anticipate full recoveries.

The four affected tigers live in the zoo’s Tiger Mountain exhibit. One male Amur tiger that also lives at Tiger Mountain has not exhibited any clinical signs, and a Malayan tiger and two Amur tigers at the zoo’s Wild Asia exhibit have also not exhibited any clinical signs.

None of the zoo’s snow leopards, cheetahs, clouded leopard, Amur leopard, puma or serval are showing any signs of illness. Our cats were infected by a person caring for them who was asymptomatically infected with the virus or before that person developed symptoms. Appropriate preventive measures are now in place for all staff who are caring for them, and the other cats in our four WCS zoos, to prevent further exposure of any other of our zoo cats.

We are grateful for the cooperation and support of the New York State Diagnostic Laboratory at Cornell University and the University of Illinois College of Veterinary Medicine Veterinary Diagnostic Laboratory, where the initial COVID-19 testing of samples from the tiger were performed; the USDA National Veterinary Services Laboratory where confirmatory testing was conducted; USDA Animal and Plant Health Inspection Service; and the New York and Illinois State Veterinarians and the New York City Department of Health and Mental Hygiene for their assistance.

COVID-19 is a disease caused by the coronavirus known as SARS-CoV-2. It is believed that the virus was first transferred to people at a food market that trades in wildlife in Wuhan, China. There is no evidence that animals play a role in the transmission of COVID-19 to people other than the initial event in the Wuhan market, and no evidence that any person has been infected with COVID-19 in the US by animals, including by pet dogs or cats.

We will issue additional information as warranted. Our four zoos and aquarium have been temporarily closed since March 16.
###

Max Pulsinelli
Executive Director, Communications,
WCS Zoos and Aquarium
Bronx Zoo/New York Aquarium/Central Park Zoo/Prospect Park Zoo/Queens Zoo

While SARS-CoV-2 is a zoonotic disease, this is a case of reverse-zoonosis; the transmission of a disease from a human to another animal species.  During the 2009 H1N1 we saw both dogs (see US: Dog Tests Positive For H1N1) and cats (see Companion Animals And Novel H1N1) infected following close contact with a sick humans.
Cat-to-human transmission of a novel respiratory virus appears to be exceedingly rare, but it has been reported (see EID Journal: Avian H7N2 Virus in Human Exposed to Sick Cats).
Seventeen years ago the world was facing two novel, potentially pandemic-sparking, viruses; H5N1 avian flu and the SARS Coronavirus. 
While SARS would be contained within months, and a decade later the H5N1 threat would give way to other avian flu threats (H7N9, H5Nx), for most of the first decade of the 21st century all eyes were on H5N1. 
After sparking a mini-epidemic in Hong Kong in 1997, H5N1 went to ground until February of 2003, when a family arrived in Hong Kong from the Mainland (Fujian Province), infected with the virus. Although human cases remained sparse until 2004, in December of 2003 2 tigers and 2 leopards, died unexpectedly at a zoo in Thailand.
Subsequent investigation revealed the cause to be the H5N1 virus, which had infected from the raw chicken they were being fed. This is the first report of an influenza infection in big cats, but it would be far from the last.
The following comes from a World Health Organization GAR report from 2006.
H5N1 avian influenza in domestic cats
28 February 2006
(EXCERPTS)

In February 2004, the virus was detected in a clouded leopard that died at a zoo near Bangkok. A white tiger died from infection with the virus at the same zoo in March 2004.
In October 2004, captive tigers fed on fresh chicken carcasses began dying in large numbers at a zoo in Thailand. Altogether 147 tigers out of 441 died of infection or were euthanized. Subsequent investigation determined that at least some tiger-to-tiger transmission of the virus occurred.
(Continue . . . )
These reports gave rise to concerns about smaller cats as well. A partial list of cat flu stories we've looked at includes:
Prior to 2004, it was generally assumed that both dogs and cats weren't susceptible to influenza. Today we know better.  To the above list we can add numerous reports of dogs being infected with both canine (H3N8 or H3N2) and avian (H5N1 & H5N8) flu viruses (see Study: Dogs As Potential `Mixing Vessels’ For Influenza).

Last August, in IJID: Animal Influenza Virus Infections in Humans - A Commentary, we looked at an open-access review - published in the International Journal of Infectious Diseases - of zoonotic influenza threats, along with recommendations on future surveillance.
The authors proposed that swine, followed by avian species, pose the greatest pandemic threat - with companion animals like dogs, cats, and horses - while having some potential, are much further down the list.
We now have evidence that cats and dogs are susceptible to our novel coronavirus as well. While their contribution to the spread of these viruses so far has been negligible - and their potential for doing so in the future is considered low - it is possible they could serve as important `sentinel' species for early detection of emerging viruses.

All of which means their continued study could warn us about other pandemic threats that are all but guaranteed to emerge in the years to come.

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