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Science’s COVID-19 reporting is supported by the Pulitzer Center and the Heising-Simons Foundation.
SARS-CoV-2 has never been an exclusively human problem. Since the early days of the pandemic, scientists have been concerned about the impact of the virus responsible for COVID-19 on pets, livestock, and wildlife. Cats and dogs can become infected, and cats appear to transmit the coronavirus to other cats, at least in the lab. Mink at hundreds of farms around the globe have suffered outbreaks, leading to massive culling, and in some cases, human infections. And scientists worry people or domestic animals could transmit the virus to wildlife, creating an uncontrollable reservoir of the disease.
Fortunately, very effective human vaccines have arrived (though it may take a while for everyone to get one). But are vaccines for pets and other animals necessary? How will they be developed? And how quickly could they become available? Here’s what we know so far.
There’s no urgent need for a pet vaccine.
It’s still not clear how many dogs and cats have been infected with SARS-CoV-2, although the rates may be similar to those of people. Yet pet symptoms seem to be mild, if they appear at all.
In addition, “Cats and dogs don’t play an important role in the maintenance or transmission of the disease to humans,” says William Karesh, executive vice president for health and policy at EcoHealth Alliance, a nonprofit that tracks emerging diseases in animals. As a result, he says, “There’s no need for a vaccine from a public health standpoint.”
Indeed, the U.S. Department of Agriculture (USDA), which grants commercial licenses for pet vaccines, is not currently approving any for COVID-19. The “data do not indicate that such a vaccine would have value,” according to the agency. “Companies are still free to do research and development on these vaccines,” USDA spokesperson Joelle Hayden tells Science, “but without a license, they can’t sell or distribute them.”
What about vaccines for other animals?
Lab studies suggest SARS-CoV-2 can infect a wide range of animals, from squirrels to sheep to sperm whales. Jonathan Epstein, vice president for science and outreach at EcoHealth, has one concern at the top of his list: great apes. Human respiratory viruses have in the past been fatal in chimpanzees and gorillas, he notes, and researchers worry the new coronavirus could decimate endangered primate species in Africa and Asia.
Karesh is also concerned about endangered animals such as black-footed ferrets, which are likely at high risk for COVID-19, given the susceptibility of lab ferrets to the disease. He’s also worried about great apes at zoos and sanctuaries—places where tigers and other animals have become infected.
Epstein is concerned about mink, too. Given the outbreaks on mink farms, he says, “There’s the potential for the virus to mutate and not only jump to people, but to wildlife as well.”
With both mink and apes, however, Epstein argues the best approach would be to change how we interact with them. Mink are kept in high densities, he says, which likely fosters the transmission of the virus. “Should we continue to farm them this way?” And he says that, regardless of whether people themselves are vaccinated against COVID-19, they should always take extra precautions around animals that could be susceptible to SARS-CoV-2. “Anyone who’s going to come into contact with gorillas should wear a mask.”
COVID-19 animal vaccines should be relatively easy to make at this point. Indeed, we may already have some.
This week, Russia announced it was close to completing clinical trials on a COVID-19 vaccine for mink and domestic animals such as cats. The details of the vaccine were not made public, but the government center developing the vaccine said doses could be widely available in a few months.
A U.S. veterinary pharmaceutical company, Zoetis, is also working on a vaccine for mink and pets. Like human vaccinemaker Novavax’s approach, Zoetis’s strategy delivers a shot of a modified form of the SARS-CoV-2 spike protein. Recent data presented by the company show cats and dogs mounted a strong immune response to the viral molecule, or antigen, although it’s not yet clear whether it was enough to protect them against infection.
John Hardham, who runs the emerging infectious disease program at Zoetis, says his company is in talks with USDA to license its mink vaccine, and that it could rapidly adapt the candidate for dogs and cats. He says Zoetis has also had conversations with zoo vets, who have expressed interest in the vaccine.
Meanwhile, vaccines for some other animals may effectively be here. The human COVID-19 vaccines that have been approved or clinically tested required safety and efficacy tests with hamsters, mice, or monkeys, meaning we may already know how to protect those creatures.
Karesh says translating the vaccines across species should be relatively straightforward. “Different species have different immune responses, so you may need to double or triple the antigen level in, say, dogs versus cats,” he says. “But the fundamentals of the vaccine approach wouldn’t change.”
It’s never too early to start thinking about the next pandemic.
Vaccinated people who are protected from COVID-19 could still become infected with SARS-CoV-2 and transmit it to others. The same likely holds true for other animals who receive COVID-19 vaccines. That means constant vigilance and regular vaccinations, Karesh says. “There’s a perception that COVID-19 is going away,” he says. “It’s not. It will be with us forever. So the risk to animals won’t go away, either.”
Epstein worries about future viral pandemics, especially as the wildlife trade, deforestation, and other human activities continue to bring us into close contact with wild animals. “There’s a high degree of certainty that there’s going to be a SARS-CoV-3,” he says.
As such, he hopes scientists will put more effort into a universal coronavirus vaccine—one that won’t just arm the immune system against SARS-CoV-2, but against any of its relatives. “We need to protect against the viruses we don’t know about yet,” he says, “in addition to the ones we do.”
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