Over the past year, coronavirus vaccines have gone into billions of human arms — and into the fuzzy haunches of an ark’s worth of zoo animals. Jaguars are receiving the jab. Bonobos are being given the jab. Orangutans, otters, ferrets, fruit bats, and, of all things, lions, tigers, and bears are being dosed.).
Two animals that are more familiar to us, domestic cats or dogs, are often left behind.
Pets are observant.
“I get so many questions about this issue,” Dr. Elizabeth Lennon, a veterinarian at the University of Pennsylvania, said. “Will there be a vaccine? When will there be a vaccine?”
Technically, a pet vaccination is possible. Many research groups claim that they have developed promising vaccines for cats and dogs; the shots that zoo animals receive were originally designed for them. dogs.
Experts said that vaccinating pets should not be a priority. Although dogs and cats can catch the virus, a growing body of evidence suggests that Fluffy and Fido play little to no role in its spread — and rarely fall ill themselves.
“A vaccine is quite unlikely, I think, for dogs and cats,” Dr. Will Sander, a veterinarian at the University of Illinois Urbana-Champaign, said. “The risk of disease spread and illness in pets is so low that any vaccine would not be worth giving.”
A positive Pomeranian
A woman from Hong Kong was diagnosed in February 2020 with Covid-19. The virus was quickly confirmed in two other people living at her home, as well as an uninvited Pomeranian senior. The virus was first identified in a 17-year old dog.
But that’s not all. The first positive test was done in Hong Kong by a German shepherd, and the same went for cats in New York, Belgium, Hong Kong and Hong Kong. The cases were exceedingly mild — the animals had few or no symptoms — and experts concluded that humans had spread the virus to the pets, rather than vice versa.
“To date, there hasn’t been any documented cases of dogs or cats spreading the virus to people,” Dr. Lennon said.
However, the possibility of a pet pandemic inspired interest in an animal vaccine. Zoetis is a New Jersey-based veterinary pharmacy company that began working on a vaccine as soon as they heard of the Hong Kong Pomeranian.
“We figured, ‘Wow, this could become serious, so let’s start working on a product,’” Mahesh Kumar, a senior vice president at Zoetis who leads vaccine development, said.
By the fall of 2020, Zoetis had four promising candidates for a vaccine, each of which elicited “robust” antibody responses in cats and dogs, the company announced. (The small studies have not been published.
As vaccine development advanced, it became clear that pets infected with rabies were unlikely to pose a threat to humans or animals.
One study that included 76 pets and their owners found that 17.6 per cent of cats and 1.7 per cent of dogs were positive for the virus. Studies have repeatedly shown that cats are more likely to contract the virus than dogs. This could be due to behavioral and biological reasons. 82.4 percent of the infected animals had no symptoms.
Pets can fall ill with mild symptoms like lethargy, coughing and sneezing. Although most pets make full recovery with no treatment, there are some cases that can be more severe.
Moreover, there is no evidence that cats or dogs spread the virus to humans — and there are few signs that they readily transmit it among themselves. For instance, stray cats are less likely to develop antibodies to the virus that cats who live with humans. This suggests that the animals are more likely to get the virus from us than from one another.
“It doesn’t look like cats or dogs would ever be a reservoir for this virus,” Dr. Jeanette O’Quin, a veterinarian at Ohio State University, said. “We believe that if there weren’t sick people around them, they would not be able to continue spreading it from animal to animal — it would not continue to exist in their population.”
Experts were convinced that a vaccine for pets wasn’t necessary. In November 2020, the U.S. Department of Agriculture, which regulates veterinary medicines, said that it was not accepting any applications for cat or dog vaccines “because data do not indicate such a vaccine would have value.”
Keep mink in the pink
As the pet threat receded, a second problem emerged: mink. The virus was highly susceptible to these sleek, slim mammals that are raised in large numbers. They were also spreading the virus to their fellow animals and to humans.
“I think that the situation in mink absolutely warrants a vaccine,” Dr. Lennon said.
The U.S.D.A. agreed. The U.S.D.A. agreed with this view and, in the same November notice that stated it was not considering vaccines for cats or dogs, it also declared it open to receiving applications for a mink vaccination.
Zoetis repurposed one of its dog vaccines to make mink vaccines. (Several other teams have also been developing mink vaccines. Russia has already approved a shot that can be administered to all carnivores including mink and has reportedly begun giving it to animals.
Studies in mink are ongoing, but when word got out about Zoetis’s work, zoos came calling. Some of their animals — including gorillas, tigers and snow leopards — had already caught the virus, and they wanted to give the mink vaccine a whirl. “We got a huge number of requests,” Dr. Kumar said.
Zoetis, which decided to supply the vaccine to zoos on an experimental basis, has now committed to donating 26,000 doses — enough to vaccinate 13,000 animals — to zoos and animal sanctuaries in 14 countries.
This development means that many domestic animals, including tigers and lions, are getting vaccinated. In part, that’s because these species appear to be more susceptible to the virus; some have died after becoming infected, although the cause of death is often difficult to conclusively determine.
“The big cats seem to be getting sicker than the house cats,” Dr. Lennon said.
Additionally, zoo cats are more likely to be seen than average house cat and are thus highly endangered.
“I don’t want to diminish anybody’s pets,” Dr. Sander said. “I have a cat myself. I think that a lot of these animals are in very high conservation status. They’re genetically very valuable. And so they want to try and provide the best protection possible.”
Calculus for cat vaccination
Scientists acknowledge that although there is evidence to suggest that the virus is not a serious threat to pets’ health, there is still much to learn. It is unclear how often infected humans transmit the virus to their pets. Officials do not recommend routine testing for companion animals. The virus may also have health consequences that are not yet known.
Scientists raised the possibility that the Alpha variant, which has been first identified in Britain in 2005, could cause heart inflammation in pets and dogs. Experts said that although the evidence is not conclusive, the virus has been linked with the same problem in humans. The connection is worth investigating.
“We need to do more research in this area to find out if this is a real association,” Dr. O’Quin said.
There are some pets that are more at risk than others. Dr. Lennon, along with her colleagues, recently discovered an immunocompromised puppy who seemed to have become severely ill due to the virus. This dog also shed high levels for longer than a week, which is unusual among infected dogs.
“Of course, that’s one case, but it really does illustrate that Covid isn’t the same in all pets, just like it isn’t in all people,” Dr. Lennon said.
It is certainly possible that future research — or changes in the virus — could change the calculus on a pet vaccine. Scientists said that if the virus is more prevalent, virulent, and transmissible in pets or dogs than it is currently known, this would make the case to develop a vaccine even stronger. The U.S.D.A. has said that it may re-evaluate its position if “more evidence of transmission and clinical disease” emerges in a particular species.
Dr. Kumar stated that Zoetis is ready to pick up where it left off in its pet vaccines if that happens. He said that if the company’s mink vaccine is licensed, veterinarians might be able to use it off-label in the event of an unexpected outbreak in cats or dogs.
Applied DNA Sciences, a New York-based biotech company, has also developed a promising cat vaccine “as a ‘just in case,’” James Hayward, the company’s chief executive, said. (Like Zoetis the company, which works in partnership with Evvivax the Italian company, is now more focusing on a mink vaccination.
There are steps pet owners can take to protect their pets for now. People who have tested positive for the virus need to isolate their pets and wear a mask while caring for them.
The United States now has a wide range of vaccines for humans. “The best way to prevent SARS-CoV-2 in our pets is to prevent the disease in people,” Dr. O’Quin said. “So please get vaccinated.”
Source: NY Times