The Oakland Zoo in California started this week with bears, mountain lions, tigers and ferrets, the first of about 100 animals that are set to receive an experimental vaccine against the coronavirus over the summer.
Zoetis, a veterinary pharmaceutical company, is donating 11,000 doses of the vaccine to about 70 zoos as well as sanctuaries, universities and other animal conservation sites in 27 U.S. states, and the Oakland Zoo is one of the first to benefit. The vaccine is solely for animals, goes through a different approval process than for people, and cannot be used to protect humans.
“It means a lot more safety for our beautiful animals,” Dr. Alex Herman, said vice president of veterinary services at the Oakland Zoo. “Our very first animals to get vaccinated at the zoo were two of our beautiful and elderly tigers.”
The Oakland Zoo has not had any cases of animals infected with SARS-CoV-2, the virus that causes Covid in humans. But the zoo has taken extraordinary precautions, Dr. Herman said, by requiring that keepers maintain a safe distance from the animals and wear protective equipment.
Big cats and other vulnerable animals like gorillas have, however, been infected at zoos in the United States and elsewhere. The San Diego Zoo in February vaccinated apes with the Zoetis vaccine, first tested in mink.
The company, based in New Jersey, has also provided the same experimental vaccine to mink farmers in Oregon after the state ruled this spring that all farmed mink had to be vaccinated. The U.S. Department of Agriculture has approved the vaccine for experimental use “on a case-by-case basis,” according to Christina Lood, a senior communications director for Zoetis.
The vaccine donation is the latest development in the patchwork reaction to animals that have become infected with the virus.
From the start of the pandemic, pet owners, zookeepers, fur farmers and scientists all had their own particular concerns about animal infections. Pet owners have worried about the health of beloved cats and dogs, while epidemiologists and public health officials have cautioned that some animal species — domestic or wild — could become a reservoir where the virus can live and mutate even as the world tries to stamp it down in people.
The U.S. Department of Agriculture has not considered any vaccine candidates for cats or dogs, and veterinarians have consistently noted that there is no evidence that pets transmit the virus to humans. The virus did, however, pass from farmed mink to humans.
Scientists continue to find, however, that both cats and dogs catch the virus from their owners. Cats are more susceptible and although most have mild symptoms, several studies have reported cats with severe symptoms. One cat in Britain had to be euthanized.
Dr. Dorothee Bienzle, a veterinarian and immunologist at the University of Guelph, in Ontario, who recently completed a study of cats and dogs living in households with humans who had Covid, found several cases of cats with severe symptoms. But she said that to definitively pin the symptoms on the coronavirus, all other illnesses would have had to be excluded; that wasn’t possible in her study, which depended on blood samples and owner descriptions of symptoms.
Dr. Karen Terio, a veterinarian and pathologist at the veterinary school at the University of Illinois at Urbana-Champaign, echoed that sentiment, saying, “I have heard of cats with severe clinical signs but had not seen any cases where they could confirm that the signs were due to SARS-CoV-2.”
At the recent online meeting of the European Congress of Clinical Microbiology & Infectious Diseases, Dr. Bienzle presented preliminary results of the research she and her colleagues had conducted.
They first tested cats and dogs in households where humans had tested positive for the coronavirus. “We targeted a population that was likely to be positive,” Dr. Bienzle said.
They found, as expected, that more cats than dogs tested positive, 67 percent compared with 43 percent. Also, in cats, time spent with owners, particularly sleeping on the same bed, increased their chances of infection. That was not true with dogs.
The researchers then tested cats admitted to shelters and cats brought to low-cost clinics for neutering. These cats, which were not known to have lived with infected humans, had a remarkably lower incidence of infection, 9 percent for cats in shelters, and only 3 percent for cats brought to the clinics.
Dr. Bienzle said the advice for pet owners has remained consistent throughout the pandemic. If you have Covid, you should isolate from your pets as you would from a human. Neither the United States nor Canada support the vaccination of pets. Dr. Bienzle said human transmission to the animals could be prevented with social distancing and masks.
Researchers at sanctuaries and those working with vulnerable species like bats have adopted stricter measures to protect the animals from infection.
For zoos, the question is not whether to vaccinate, but how to approach the patient when it’s a tiger. “With lots of positive reinforcement,” Dr. Herman said. The zoo trains its animals by giving them rewards to voluntarily present themselves to be jabbed. It’s pretty much the same idea as getting a lollipop after a shot, although the animals seem more willing to volunteer than humans.
“The tiger leans against the fence,” Dr. Herman said. “The thousand-pound grizzly bear leans against the fence.”
Good tiger. Good bear.