After years, mystery of ‘cat Covid’ solved

It was the dogs’ fault – sort of

The cause behind the ‘cat Covid’ epidemic of 2023 has now been established, according to a UK team led by a Cypriot scientist.

‘Cyprus becomes “island of dead cats” after outbreak of feline coronavirus kills 300,000,’ went the headline in The Telegraph in July of that year. ‘Why deadly cat virus in Cyprus could be “potentially catastrophic for UK”,’ catastrophised Sky News in August. ‘New feline coronavirus blamed for thousands of cat deaths in Cyprus’ was the title of an article in Science.

So-called ‘cat Covid’ was indeed a coronavirus, previously mild and almost never life-threatening, that suddenly mutated into feline infectious peritonitis (FIP), becoming not just contagious – which FIP typically isn’t – but also deadly.

“We were losing animals, one after the other,” recalls Kyriakos Kyriakides of V3ts veterinary clinic in Larnaca.

“I’ve been dealing with strays for 30-35 years,” Dinos Ayiomamitis, head of Cat P.A.W.S. Cyprus, told the Cyprus Mail. “We’ve never had such an epidemic before, on such a scale.”

It was unprecedented. The reason why foreign papers and scientific journals became interested in a cat epidemic in Cyprus, however, is because it really was unprecedented.

This particular strain – this mutation – of coronavirus had never been seen anywhere in the world before. It was as novel as the one behind our own Covid-19.

A research team led by Dr Charalampos Attipa at the University of Edinburgh undertook to investigate the outbreak.

Now, two years later, their paper – titled ‘Feline infectious peritonitis epizootic caused by a recombinant coronavirus’ – has appeared in Nature, published last July.

It’s the first time that prestigious journal has published a paper on a ‘companion animal’ disease (i.e. dogs and cats) in almost 40 years, which “illustrates the significance of this work,” Dr Attipa told the Cyprus Mail.

The surprising result of their analysis is that the virus in question, which they’ve called FCoV-23, is actually a hybrid virus: a genetic mix of a cat coronavirus and a dog coronavirus.

The old feline virus now contains a chunk of RNA from the dog virus pCCoV which is ‘pantropic’, meaning it goes in many different tissues and infects the whole organism.

pCCoV has been known to cause epidemics in dogs, especially in countries of the eastern Mediterranean, according to Demetris Epaminondas, president of the Pancyprian Veterinary Association.

However, this is the first time it’s been linked to a cat epidemic – and, though this kind of cross-species mutation does sometimes happen, it’s unheard-of for “the resulting strain to be so virulent, and cause such a big epidemic,” Epaminondas told the Cyprus Mail.

The epidemic raged for most of 2023. Vets were defenceless, because “there was no clear treatment at the time,” says Kyriakides. FIP, ordinarily a rare disease, was actually considered incurable till a few years ago, and the one treatment was prohibitively expensive.

A black market quickly sprang up, with desperate cat owners turning to the internet for promised cures, despite vets advising that the miracle medicines were probably snake oil.

It was an awful, traumatic time – even more so because FIP is a horrible death, especially in its ‘wet form’ when the cat’s chest and belly swell up with fluid.

Like our own Covid-19, the outbreak never entirely went away. Even now, though stable, cases of FIP remain higher than they were before 2023 – but cats have developed antibodies and, most importantly, vets have treatments now, largely the same drugs that were used to treat Covid in humans, bringing the outbreak to heel when the government finally made them available.

So much for 2023. Two years later, however, questions continue to linger.

One question is related to the actual ‘cat Covid’ death toll – which, despite the Telegraph’s alarmist headline, was contested even at the time.

No-one really knows, says Epaminondas. The one objective data point his association have gathered is that, in the first eight months of 2023, the total number of cats brought to vets with FIP – that’s cases, not even deaths – was 8,500, “a huge number” for this rare disease but considerably lower than 300,000.

Then again, the epidemic mostly hit strays, who’d be unlikely to see the inside of a clinic. Ayiomamitis offers another data point. The volunteers who feed stray cats – especially in large feline colonies in parks, cemeteries, or places like Mackenzie in Larnaca and Dasoudi in Limassol – consistently reported seeing a reduction in numbers of about 30 per cent.

The cat population is supposedly about one million, so 30 per cent is 300,000. But in fact, that one million total – source of the famous claim about Cyprus having ‘more cats than people’ – is just an estimate.

The truth is that no-one, not even the government, knows the extent of our stray-cat problem. “The government doesn’t concern itself with strays,” says Ayiomamitis wryly. “All it does is approve a grant for cats to be spayed.” That annual subsidy is currently around €100,000 – clearly inadequate, when sterilisation costs about €50.

That’s another lingering question – namely, should the state have done more? It did make Covid drugs available, but that was after sustained pressure from vets.

“Unfortunately, things happen a little bit slowly in our country,” says Epaminondas, not wishing to sound ungrateful. Ayiomamitis, though, points out that in Greece, “on many Greek islands, there’s legislation compelling local authorities to take care of strays” – unlike here, where animal welfare is largely in the hands of volunteers and private charities.

Indeed, though no-one actually says so, it’s hard to avoid a suspicion that the authorities viewed a disease decimating the stray-cat population as a solution rather than a problem.

Two years later, we at least know what the mystery virus was – but how did it happen that a cat and dog coronavirus got together so suddenly and aggressively? Could it happen again, and potentially spread to humans?

And was it just coincidence that FCoV-23 appeared, out of nowhere, in cats just a few years after Covid-19 appeared, out of nowhere, in people?

On the last point, Epaminondas is reassuring, noting that cat coronaviruses are in a different ‘family’ from human ones, with a “cross-species barrier” separating the two.

Then again, there were many accounts during the pandemic of people passing Covid to their pet cats – albeit usually without any clinical symptoms – so transference is technically possible.

A Guardian article from July 2023 speculates that human Covid may indeed have influenced cat Covid: “Since cats can be infected with Covid-19, many carry new antibodies that could have driven the evolution of existing feline coronaviruses”.

The coincidence is sufficiently striking that a possible link is being investigated, says Epaminondas. “So far, though, nothing has been confirmed. And it’s looking like nothing will be.”

Research is ongoing. There are two PhD students carrying out further research in Cyprus, says Dr Attipa, while a global consortium has been formed, with $1 million funding, to study our outbreak specifically and FIP generally.

How the mutation began is equally unclear. The Science article speaks of the cat coronavirus having “encountered pCCoV in an unidentified animal host”, while Ayiomamitis thinks it was brought by animals who came over from the Middle East, with Cyprus acting as a hotspot because of our large number of stray cats.

That’s actually quite plausible. According to Attipa in the Guardian article, vets in Lebanon, Israel and Turkey anecdotally reported similar increases in FIP, while imported Cyprus cats subsequently caused a handful of cases in the UK – hence the panicky Sky News article.

Could a future mutation affect humans? “That,” says Epaminondas firmly, “would be a long shot.” The two species are just too different, from proteins to cell types.

Still, it’s worrying to see how a virus – any virus – can mutate so suddenly and dramatically.