With sporadic reports in recent weeks of cats infected with the coronavirus that causes Covid-19, a group of researchers set out to determine whether cats can transmit the pathogen to one another.

The answer, the scientists said: They can. The question now is whether felines can transmit SARS-CoV-2 back to people.

Researchers from the University of Wisconsin-Madison and the University of Tokyo noted that none of the cats in their study was visibly ailing, but they shed the virus from their nasal passages for about six days.

advertisement

“Considering the amount of virus we found coming out of the noses of the cats … there is the possibility that these cats are shedding, fomites are being released in a person’s household or at cat shelters or human societies and that somehow people could possibly pick up the virus. I think it’s something people should be aware of,” said Peter Halfmann, a research professor at the University of Wisconsin and first author of the study, published as a letter in the New England Journal of Medicine.

“It depends on the household and the cat, but there could be a lot of close contact with your pet cat on occasion,” Halfmann said.

advertisement

The researchers, led by virologist Yoshihiro Kawaoka, experimentally infected three cats, and then placed an uninfected cat into each of the cages housing the infected animals a day later. The three uninfected cats were all infected within five days.

Halfmann said uninfected cats were also put into cages a foot away from the cages containing the infected cats. None of those felines became infected with the virus.

In early April, Chinese researchers reported that cats and ferrets were susceptible to infection. A few weeks later the U.S. Department of Agriculture announced that two pet cats in New York state had tested positive for the virus. At least eight big cats at the Bronx Zoo — tigers and lions — were also infected with the virus.

Many research groups have reported on virus shedding with Covid-19 by simply conducting testing by polymerase chain reaction, or PCR. A positive PCR hit tells you that the human or animal is shedding something, but it doesn’t reveal if they are emitting viral debris — which poses no risk of infection — or actual infectious viruses.

The researchers responsible for this work did attempt to grow viruses from swabs taken from the noses and rectums of the cats; they found that all the animals were emitting infectious viruses from their noses. None of the rectal swabs produced infectious virus.

Halfmann said there was quite a lot of virus — between 30,000 and 50,000 virus particles per swab. But what that means isn’t clear, he said. It’s not known how big a dose of virus is needed to infect a person. And there’s no ethically acceptable way to construct a trial to see if cats can infect people.

Still the researchers suggested people should be aware of the possibility of transmission from cats to people, and keep cats away from anyone in a household who is suspected of being sick with Covid-19. “I think it’s good practice to have this in people’s minds,” Halfmann said. He and his co-authors also urged people not to abandon cats or give them up for adoption because of such concerns.

They also advised cat owners to keep their cats indoors.

“Cats are still much more likely to get Covid-19 from you, rather than you get it from a cat,” Keith Poulsen, director of the Wisconsin Veterinary Diagnostic Laboratory, said in a statement.

  • Cats are suspected of infecting each other with Coronavirus, through nasal contact, so shouldn’t they be kept away from everyone? I know so many cat lovers!

    • Children are known (not suspected, but proven) asymptomatic carriers and shedders of the coronavirus. Shouldn’t they be kept away from everyone? I know so many people that are fond of children!

  • “Apparently proven facts”! What kind of nonscientific drivel is that phrase? It is not a “proven fact” that cats can become infected with SARS-CoV2. Cats have been artificially infected in a laboratory setting, as have mice and rats. There has been no proof offered that the animals that have been infected in a natural setting do, in fact, have the novel coronavirus. Nothing peer reviewed, nothing showing that the virus was positively identified. As I noted previously, it was amusing that the current article on the artificially-induced laboratory “infection” was juxtaposed with an article noting that some COVID-19 tests have a 50% failure rate. Shedding of viral particles from a test animal that has been artificially infected in a laboratory in no way proves that such a situation can occur in a natural setting. The same applies to the lab-infected cat infecting another animal. In fact, the “researchers” had to force close contact for the artificially-induced infection in the one animal to transfer to the second animal – and this with an infectious agent that is highly transmissible in natural settings. So much for “apparently proven facts”.

    While the use of pre-prints to expedite the sharing of information has some benefits, what has unfortunately happened is that a lot of bogus “science” — on cats, humans, “cures” and any number of other subjects — is thrown into the public domain with no process in place to separate the wheat from the chaff. And then, some people wonder why other people believe that 5G towers spread the virus.

    • I do not want to argue, but to be clear, the cats in Wuhan, which, it was claimed, had about a 10% infection rate, were NOT “artificially” infected. Although I think it is clear the Chinese government officials were dishonest about the epidemic there, and the number of asymptomatic infectees is still not clear maybe, for what it is worth, they claimed the human infections were about 150,000 I think – some number which was far lower than 10% of the population there, a city of around 10 million – so, cats may get it a lot more easily than humans.
      And you can claim the first cats in the labs were artificially infected, but the second cats were infected solely by being close to the infected ones.
      That is a completely natural situation.
      I am not trying to beat it to death, just clear up your assertions do not really hold up.
      Generally speaking, the things we knows cats naturally do are the opposite of what we are told to do to prevent being infected.
      1. We are told to wash our hands and keeps them away from our faces because the virus could easily get on our hands and then if it gets to our faces, get in our mouth, nose, or eyes.

      Cats walk on the ground, where the virus falls, without wearing gloves, then, instead of washing their paws with soap or paw sanitizer, LICK them to get them clean. Direct paw to mouth contact.

      2. People are told virus can get on their bodies simply by settling on them. On their clothes, on their hands, uncovered arms or legs – but we are told it will not infect us unless it comes in some mucus membrane, again, mouth, nose, eyes.

      So, we avoid licking our bodies, or our clothes. Doctors make a point of removing all their work clothes before leaving their garages and going in their houses.

      Cats like all their body parts – meaning, first they get infected from virus which was had settled on their fur, then they put virus all over their fur, so anyone who touches them may get it on their hands.

      I am repeating myself. Good luck and stay safe.

      The exact opposite of

  • ” And there’s no ethically acceptable way to construct a trial to see if cats can infect people.”

    Debatable. Accept only healthy participants without co-morbidity factors and inform them fully of the risks, provide them substantial financial compensation and guarantee them best available medical care at no charge if they develop a serious case. Medical studies of human subjects do not need to be risk free and few if any actually are. In the case of SARS-CoV-2 There is no vaccine, infection is widespread with anti-body tests from NYC indicating that almost 25% of the population is likely infected. In other places infection rates at large appear to be lower but many are still double digit percentages. Based on this, and the exponential nature of spread, the chances of eventual infection of any given person before a vaccine is available is quite high. Participating in a study would give the participants the opportunity to quite possibly develop resistance or even immunity under highly controlled conditions with immediate medical care essentially on standby. It’s a pretty equitable trade off considering the nature of the situation at large.

    • Fact: Cats can become infected with SARS-CoV-2.
      Fact: Cats infected with SARS-CoV-2 shed active viral particles.
      Fact: Cats exposed to shed viral particles from another cat can and did become infected.

      Those are apparently proven facts. If they make you or any other given person afraid is another question.

  • I have 3 cats, which don’t go out, so we don’t have to worry about that! But lots of cats do go out, so it could be a problem. We don’t yet know that we cannot get COVID-19 from a cat, all we know is that we don’t have any confirmed cases. There are many good reasons not to let our cats out of the house, but this one must be the very best.

  • This “study” was merely one more example of animals unnaturally infected in a lab. Animals that are not typically prone to attack by an infectious agent can be infected in a lab setting. Lab infection can be accomplished by an unnatural route of entry, an unnaturally high dose of an infective agent, or even by manipulating an animal’s physiology or genetics. Mice have been infected with the novel coronavirus for some studies, yet rodents are not mentioned as potential vectors. It’s often difficult to determine which species are natural potential hosts from laboratory-induced infections. Sadly, some researchers are so eager to get on the coronavirus publication bandwagon they throw good science aside.

    Yes, Hilde S is correct, there have been reported cases of dogs being infected. Are any of the alleged cases of infection in a non-laboratory setting really one of the human-infecting strains of SARS-CoV-19? Hard data are hard to come by.

    Unfortunately, the mention of “feral cats” – in regard to any situation — elicits an irrational response (latent ailurophobia?) in some folks. And, yes, it is entirely accurate to label it irrational. Although people were infected with the human form of bovine spongiform encephalopathy (mad cow disease), some quite severely and some lethally, from proximity to cows, but people did not stop eating beef. And, while there is a high likelihood for at least fomite-type contamination at meat-processing plants where a high percentage of workers are infected with SAR-CoV2 (humans are a proven vector!), the impetus is to get the meat lines running again, not to stop eating meat.

    There is so much sheer conjecture floating around about this infection. Some researchers postulate that bats can harbor novel viral infections such as SARS-CoV-19 with minimal symptoms because their bodies tamp down their immune response to an infection, going with the school of thought that the potentially lethal effects in humans are due to the overreaction of our own immune systems. Other researchers postulate bats can tolerate said infections because they have super-robust immune systems. OK, you can’t have it both ways. Which is it? Are the alleged nonhuman cases due to one mechanism or the other? Or neither? Who knows? There is no follow up, only breathless and barely scientific allegations that nonhumans are “infected”. And “animals” are a potential reservoir of infection!!!! Strange, isn’t it, that the anthropological record shows that “zoonotic” diseases reached pandemic potential, not when we were hunter-gatherers living in a natural setting teaming with wildlife, but only after we started living in close and intimate quarters with… other humans?

    It’s silly to go the hysterical route of implying we should avoid all contact with animals or, even more foolishly, get rid of certain animals. A more productive and practical approach to the alleged “animal infections” is to, first, establish, for what appear to be naturally-acquired infections of SARS-CoV-19 in nonhuman animals, that the infection is actually a strain of SARS-CoV-19, and not something related that is triggering a positive test. IF the infectious agent in these cases is actually SARS-CoV-19, then document how this was determined, and rate the severity of the infection and its attendant symptoms. In all of the alleged animal cases to date, it appears the infection has been relatively mild, with none of the clotting/cardiac/cytokine overreaction issues seen in humans. Why? Getting that question answered could have an enormous positive impact on treatment/vaccine development for humans. Why do nonhuman animals have such mild cases?

    We have known for decades that cats and dogs, and other animals, have their own specific coronavirus infections. In cats, for example, a coronavirus that normally causes a relatively benign infection occasionally mutates into a form that is pretty much universally lethal to cats, known as feline infectious peritonitis (FIP). Until recently, it was a death sentence for your pet. Now, FIP is being successfully treated with …remdesivir! The same drug recently approved for COVID-19 patients. Coincidence? Why don’t we find out? Wasting time with fake lab-induced infections is not likely to produce much of value, either to humans or to their companion or farm animals.

    • I think you are misinterpreting your obvious extensive reading on this topic.
      First, the cats in Wuhan were reported to be infected, 11% of them, and, even if that is wrong, another study showed cats got infected, from each other, without touching. They put their cages next to each other, that was sufficient.
      Additionally, the idea that an animal that can get a virus has to be forced to get it is kind of generally unlikely, at least a virus which spreads through the air – you could get an herbivore infected with rabies by putting a piece of meat from a rabid animal in it’s food – but that would not happen naturally – but breathing in the same air as an infected animal is natural for cats, if they are naturally near that animal – other cats, humans, etc, would qualify.

      If the lab work has been done right, you got a disease which can spread between cats – some cats are social and will be close enough – and the same disease is shed profusely from infected cats – I can not see any reason to think they are not spreading the disease.

    • Most of your criticisms of laboratory infection methods in general are irrelevant. The test subject cats were infected simply by being placed in a cage where a cat known to be infected was housed. No extraordinary means was used to infect them. Only environmental exposure.

      There is no such thing as “SARS-CoV-19” there is the virus, SARS-CoV-2 and the disease it causes, COVID-19.

      Finally nobody is saying to avoid contact with or get rid of any animals. That is not advised or implied anywhere in the article.

    • “you could get an herbivore infected with rabies by putting a piece of meat from a rabid animal in it’s food”

      Remotely possible maybe but not very likely. Rabies doesn’t typically spread by the oral route and there is generally only rabies virus present in limited PNS tissue, the tissue between the bite site and the CNS as the virus travels to the CNS, and in later infections CNS tissue and finally saliva and the salivary glands. Based on a small number of human to human infections in transplant cases, also the corneas, but not body tissue at large. RABV and other close lyssavirus relatives are also relatively fragile and would be easily destroyed by stomach acid so infection would have to occur before the virus reached the stomach. I certainly wouldn’t recommend eating a rabid animal unless starvation is otherwise imminent, since infection via the oral route in the way you describe might be possible, but it isn’t likely.

    • I agree with your post, outside of the fact that you made a mistake.

      You said, ” They put their cages next to each other, that was sufficient”.

      From the study:

      “Halfmann said uninfected cats were also put into cages a foot away from the cages containing the infected cats. None of those felines became infected with the virus.”

      They had to put the infected cat into the same cage as the uninfected cat in order for the infection to spread.

  • Keith Poulsen instructs us that, “Cats are still much more likely to get Covid-19 from you, rather than you get it from a cat.” I would like to know what data he used to come to that conclusion. I am not aware of any study that determines how likely it is that a cat with the virus will pass it to a human in the household, nor do I think that such a study would be allowed. Someone who reads Mr. Poulsen’s statement might be lead to be unconcerned about contracting COVID-19 from their cat. If a person is being strict about isolating themselves from other people, but owns a cat that goes outside, I would say the probability of that person infecting the cat is virtually zero, but the other way around is another story!

    • No cat or dog owner is EVER going to agree with anything to do with their pet being implicated in the spreading of this virus, or any other of the diseases animals spread!

  • There has been a report of a dog testing positive for Covid 10, so it is not just cats. Also, I believe it is the pangolin in the wet markets of China suspected of being the transmitter to humans, NOT the civit cat.

    • No parent is EVER going to agree with anything to do with their children being implicated in the spreading of this virus, or any other of the diseases children spread! This, despite the proven role of children as asymptomatic vectors of SARS-CoV2, vs. the speculative role of pets.

  • Where has Helen been? Studies have indicated months ago that the virus came from bats that infected Civet Cats (looks like a cross between a cat and a ferret or mink, with raccoon eyes). And that Civet Cats, cats, ferrets, and minks can get (and shed) the new coronavirus. By the looks of the Civet Cat, these species have genetic links. Civet Cats sold in “wet markets” in Wuhan as human food are deemed to be the transmitter to humans. Studies have also shown that cows, horses, pigs and dogs do NOT get Covid-19. Seems to me that opening “animal” Covid discussion warrants more research by STAT writers.

Comments are closed.

Sign up to receive a free weekly opinions recap from our community of experts.
Privacy Policy