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Coronavirus in cats - Evidence of infected cat populations in Wuhan

Uncategorized Apr 06, 2020

More evidence that cats can get SARS-CoV-2

Good afternoon. My name is Dr. Cameron Jones, and I'm an environmental microbiologist. I wanted to make a quick follow-up video to a video I did the other day that was focusing on the issue of SARS-CoV-2and pets, and more particularly, we're going to be focusing on cats because a fascinating paper just came out overnight and that is the topic of today's Livestream. Coronavirus in cats. There has been a lot of talk about whether or not this is a myth or whether there is some scientific validity to this and I wanted to make this video because I think that this topic has a great deal of merit. I think there's a lot of very interesting research which is going on focusing on the pets as a reservoir for SARS and whether or not these animals are capable of transmitting the virus between themselves, whether or not people are able to transmit the virus to the pet, and of course, the very worrying question, is it possible for the pets to transmit the virus to humans?

What we already know about virus transmission in pets

So let's review what we know about this in the literature. And so I'm just going to switch this now. A couple of days ago, back on March 31st, a paper came out on one of the pre-print servers and this was focusing on the fact that SARS-CoV-2 had in fact been demonstrated to be transmissible in cats and ferrets. And whilst this is really the first paper which contradicted what people thought to date was that pets were not involved. This paper, nonetheless, is very important because it is the foundation paper and when this came out, obviously, the title of this was Susceptibility of Ferrets, Cats, Dogs, and Different Domestic Animals to SARS Coronavirus-2. And what the conclusions of this paper were that the authors found that SARS-CoV-2 does, in fact, replicate poorly, thankfully, in dogs, pigs, chickens, and ducks, but efficiently in ferrets and cats.

Their next conclusion was that the transmission mechanism between these animals is through respiratory droplets and that's certainly similar for human to human transmission as well. And the conclusion that the authors made was that this first study provided important insights into the animal reservoirs for SARS-CoV-2 and really make some quite significant foundational statements about how animals should be managed to control the disease of COVID-19. Now a new paper just came out overnight on April 3rd again on the pre-print server. I've got it up here. You can search the URL or download the paper and read it for yourself. I'm going to summarize the key findings here today and the summary of the evidence from this April 3rd research.

The latest research about coronavirus in cats

Essentially, it starts off setting the context for what we're talking about because this previous study suggests that cats could be a potential susceptible animal for SARS-CoV-2 worldwide. There was earlier research on different types of Coronaviruses being present in cats and then they are going on to look at specific serum antibodies in cats.

So this is very different to the first paper and this makes it very, very important. Now, I'm going to explain why. Basically, what they did is they got a group of cats, 102 were sampled after COVID-19 in Wuhan, China and 39 cats were tested before the outbreak of SARS-CoV-2. So essentially you've got two populations, before the virus and after the virus, and they are looking at for differences in how their serum actually responds when it's analyzed, and they're looking for evidence of, firstly, the protein being present in the serum, and similarly antibodies being raised against that protein, because obviously the animal needs to mount an immune response to the invading virus and that's exactly what they're looking at in this publication. And what they did is that they found that out of the 102 cats that were tested after the outbreak had begun, that 15 of these or approximately 14.7% were positive for the receptor binding domain of the SARS-CoV-2using enzyme linked immunosorbent assay or ELISA.

The sick cats showed a positive immune reaction to the coronavirus

And what they found in those positive samples that 11 of these pets, 11 of the cats, had SARS-CoV-2 neutralizing antibodies. And I'm now going to explain why these neutralizing antibodies are particularly important because the data demonstrates them. This is their core conclusion, that SARS-CoV-2 has definitely infected the cat population in Wuhan during this outbreak. Now, you might be thinking, well, why does this matter? These are cats in Wuhan. And to put some context to the world population of domestic dogs and cats, I've pulled up some research that again has just come out in March 2020 and it's been determined that there are 471 million pet dogs worldwide and approximately 373 million cats. So that is an awful lot of domestic cats as pets, which could be potential reservoirs for SARS-CoV-2, and of course the very worrying concern, are the cats cross contaminating and infecting each other? Are infected humans contaminating the cats? And is it possible for the cats to actually contaminate other humans?

How many pet cats are there versus the number of pet dogs?

So all of those questions will be discussed to some extent in this short video and no doubt over the coming weeks and months and years in the academic research literature. But if we drill down now into the April 3rd research and look at the results and take a closer look at this, as I said, 15 of the 102 cats were positive after the outbreak with five of them being strongly positive. Now, the ELISA or enzyme linked immunosorbent assay test shows that the cats had an antibody reaction against a spike protein of the SARS-CoV-2 virus. Well, what they did is that they then confirmed this initial result by doing what's called a virus neutralizing test. And what is that? A serum virus neutralizing test is a serological test that detects the presence and magnitude of functional antibodies that prevent the infection by the virus. So this is measuring how the immune system responds to the virus being present inside the cat. And this is the gold standard method for recognizing and measuring the levels of antibodies that are capable of neutralizing the virus.

So this is a very important and sensitive assay and gives us a lot of information about the infection of the virus within the cats. And again, of those 15 positive cats, 11 were found to have the SARS-CoV-2 neutralizing antibodies. Four of these cats had no neutralizing activity. This is a worrying component of this paper as well because four of those cats were not able to mount an immune challenge to the virus. So it would be very interesting if the authors followed up with further explanations about the four cats that had no ability to mount an immune challenge or at least with the assays that these scientists use. Three of the cats, however, did show very strong neutralizing activity, and all of the cats that showed the strong neutralizing activity, that means getting rid of the virus, had owners who had been positively diagnosed as suffering from SARS, that is they had COVID-19, they had the illness and these were the pet owners.

Now, if we look at the data in their table one, this is really fantastic that we've got this information. Not only have they plotted the 15 cats, but they have shown the ELISA results and they've also shown a numerical neutralizing titer results. And I've highlighted with red arrows the three cats that were owned by the COVID-19 patients and you can see that their ELISA levels are very high. I wish they had included data for cat number 12 because that was a stray cat and that had a reasonably high ELISA level as well. But as you can see, no neutralizing titer. So that cat, unfortunately, number 12, was really unable to show an immune response. But the purpose of this paper was to focus a lot of attention on cats number 4, 14, and 15. These were the owned cats by owners who had tested positive for COVID-19. And let's have a look at what their Western blotting results showed.

Look at the lab results validating the coronavirus infection in cats

And if you'd never seen a Western blot before, this is basically drilling into the DNA, which is a type of electrophoresis gel, and this Western blotting result allows you to visualize the DNA. And what they've done here, and this is very important, they've gotten a negative cat, so a cat that does not have the SARS-CoV-2, and that is in the third lane over from the right hand side, and you can see that essentially it's blank. And when you read these Western blots from top to bottom, they're in units of something called kilodaltons. This is the molecular weight of the proteins which make up the DNA which is being blotted to visualize it. And you can see that the negative cat that doesn't have the illness doesn't show any protein bands whereas the serum from recovered people, which is located in H-P, which is the second one over from the right hand side. You can see a very strong band for the protein somewhere between 40 and 55 kilodaltons.

And then if you look over to cat number 14, 15, and 4, which are the first three lanes of the Western blot, you can see that, that matches the same molecular weight for the end protein. And what this means is that the cat owners who had recovered, they no longer had the illness, it's in the one-to-one correspondence. And similarly, people who have not had SARS-CoV-2 they also have nothing showing up in the Western blot lane. So this is really dynamite research, making a one-to-one connection between exposure to SARS-CoV-2 in recovered persons who still show circulating antibodies to SARS and the pets that then became infected. And the author's position is that people have infected the cats. And so if we look at the conclusions that these authors make in their paper, their conclusion is that the cat population of Wuhan has definitely been infected by SARS-CoV-2.

No evidence yet of cat-to-human transmission but evidence of human-to-cat transmisison

The next conclusion is that this risk could extrapolate to other outbreak regions elsewhere, not just in China, but potentially worldwide. And the ELISA positive results suggest the cats could have become infected from virus transmission from humans to cats, and at present, there is no evidence for SARS-CoV-2 being transmitted from cats to humans. It was only the other way around, from humans to cats, and that's what their data supports, that chain of reasoning or thinking. Now, we can also say a few more things. Other conclusions are that because of the recent report demonstrating that respiratory droplets spread in cats occurs, this cannot be ignored. And the authors make the point of linking their results to the preceding a paper on cats and SARS-CoV-2stating that this should serve as a warning that regulation should be issued to block this potential transmission route and no doubt there will be further emerging changes in the news and legislation and local how local organizations deal with the potential of reservoirs in pets.

Now, the difference between stray cats and those from pet hospitals, this is another component of this paper, suggests that the close contact between COVID-19 patients and cats is definitely the source of infection. When the authors examine the potential of a commercial Q-PCR kit, it failed to detect SARS-CoV-2 in both nasal pharyngeal and anal swabs from the cats. And the conclusion made by the authors is that potentially these kits are not sensitive enough for cat detection or there may be some other reason why the method failed to detect this particular protein fragments in the serum of cats. So that's something for another group of scientists, no doubt. The end conclusion is that the paper is the first report showing the cats produce neutralizing antibodies against SARS-CoV-2 under natural conditions. And there is obviously the disclaimer that a lot more research needs to be undertaken to find out the true extent of whether or not this is a significant reservoir of SARS-CoV-2 and what the ramifications and implications of this data are.

If you're diagnosed with COVID-19 maintain social distancing from your pet cat

But the takeaway message and certainly from a risk management perspective is that, "Immediate action should be implemented to keep a suitable distance between humans and companion animals such as cats and dogs and maintain strict hygiene and quarantine measures should also be carried out for these animals." That is a quote taken from the paper that has just come out in the pre-print literature.

I think it is very important to make the point that there has not been proof of cats causing transmission to people, but there has been good evidence showing that there is transmission from people to pets of SARS-CoV-2. And I am sure many people will be deciding on the implications of these findings and it will be very interesting to watch the literature very closely over the next couple of days to weeks to months. In any case, my name is Dr. Cameron Jones. I'm an environmental microbiologist and I look forward to bringing you more videos on infection control soon. Bye for now.

YouTube Link:


SARS-CoV-2 neutralizing serum antibodies in cats: a serological investigation
Qiang Zhang, Huajun Zhang, Kun Huang, Yong Yang, Xianfeng Hui, Jindong Gao, Xinglin He, Chengfei Li, Wenxiao Gong, Yufei Zhang, Cheng Peng, Xiaoxiao Gao, Huanchun Chen, Zhong Zou, Zhengli Shi, Meilin Jin
bioRxiv 2020.04.01.021196; doi:

Chen H. Susceptibility of ferrets, cats, dogs, and different domestic animals to SARS-coronavirus-2. 2020. doi:10.1101/2020.03.30.015347

Bedford E. Dog and cat pet population worldwide 2018 | Statista. Statista. Published 2020. Accessed April 5, 2020.

Watch the Livestream discussing the evidence we have for COVID-19 infection in pet cats:

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Dr. Cameron Jones


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