This past summer I reported on the FIP outbreak among cats on the island of Cyprus, with insight from Charalampos Attipa, DVM PhD, Krystle Reagan, DVM PhD, and Dr. Danielle Gunn-Moore. As thousands of cats quickly sickened and died from signs of feline infectious peritonitis (FIP), experts puzzled over why, with speculation a new FIP virus might have emerged.

While the feline-specific illness tragically kills most infected cats (if not given expensive hard-to-access treatment), pockets of “outbreaks” had previously been limited to handfuls of cats in cattery or shelter population. I reached out again to Dr. Gunn-Moore and received insight from Carol W Johnson DVM PhD DACVP for this update.

FIP Basics

FIP arises from an innocuous feline coronavirus that typically causes diarrhea–cats catch it from contact with infected waste. Sometimes, though, the virus mutates in individual cats into each cat’s unique FIP virus that targets the immune system and causes the deadly disease. Every cat that develops FIP has a slightly different virus, based on their own genetics. But it isn’t contagious, and doesn’t infect other cats.

The Cyprus outbreak affected both pets and community (roaming, unowned) felines, and appeared to spread cat-to-cat. Conservative estimates suggest 8,000 cats died. Experts suspected the Cyprus FIP virus mutated into a contagious form, speeding the spread of the illness.

Researchers Launch Investigation

The University of Edinburgh researchers and others collected fluid samples from over 100 affected cats admitted to clinics in Cyprus, and searched for viral genetic information. Using RNA sequencing, they discovered a new kind of feline coronavirus and called it FCoV-23. It includes RNA from the highly virulent pantropic canine coronavirus (pCCoV) that infects lots of different tissues. The high virulence of the dog virus also points to why the Cyprus cat disease spread so quickly. Read the study by Attipa et al here.

“Unlike the old feline coronavirus that mutates to cause FIP in 1 out of 100 to 200 infected cats, this new virus does not appear to need to mutate or change biotype prior to causing FIP,” says Carol W Johnson DVM PhD DACVP. “It can cause FIP directly. In the study, viral genome sequencing of FIP cases from different island districts showed genetic similarities that supports that the virus is directly causing FIP.”

A Recombinant Virus?

How did this happen? Apparently, coronaviruses swap genetic material and recombine with each other (dog-cat-swine) frequently, but this recombination resulted in unique problems. Researchers believe the new FIP strain arose when a cat coronavirus came in contact with the pantropic canine coronavirus. Rather than a simple mutation, it recombined with the dog virus spike protein (with additional mutations) into its own structure.

Coronaviruses use spike proteins like a key to unlock access to host cells and infect them. Viruses continue to mutate, and this may have set up the new strain to cause FIP disease, while spreading infectious, contagious material in the feces. Researchers have not confirmed exactly how the disease spreads, but have cautioned against exporting any cat from the island.

“If this virus remains in Cyprus, it may spontaneously die out. The prevalence of FIP is already declining there. Unfortunately, there has also been a cat in the UK found with the virus brought to the UK from Cyprus,” says Dr. Johnson. Experts also suspect the new FIP virus has reached Greece, Lebanon, and Turkey.

Cyprus Virus Escapes?

“Sadly, the outbreak does not need to be waning considerably,” says researcher and study co-author Danielle Gunn-Moore, BSc(Hon), BVM&S, PhD. “While there appears to be a fall, this coincides with vets treating based on clinical signs once they recognised what the disease looked like. Hence, fewer RCR tests [replication-competent retrovirus assays], which was followed by an increase once a PCR diagnosis was needed to access treatment. We will be due another update on the epidemiology soon, which will tell us a lot more.”

Dr. Gunn-Moore confirms identifying a case of FCoV-23 in the United Kingdom, and that they’re investigating to confirm other cases. “The Greece vets are reporting an increase in cases there, but, as yet, we have not confirmed that FCoV-23 is involved. The epidemiology of FIP does involve waxing and waning cases, so confirmation is needed before commenting further. That said, we cannot see why only one case would escape from Cyprus.”

Ban on Cyprus Cats?

Researchers see no risk to people with this virus because the viral sequence does not contain any parts of human viruses. “But we have to consider the potential risk to other cats,” says Dr. Gunn-Moore. She says FCoV-23 may have traveled to other places in Europe, but to confirm this, we must sequence more cases to find out if/where this has occurred.

Should an infected cat from Cyprus travel outside the island, it could quickly spread the disease and potentially cause other massive outbreaks. In particular, an infected, adopted cat allowed outside could infect community cats that come in contact with its feces. Animal shelters in Cyprus strive to place their cats in good homes–including those outside of the island. That stopped, at least temporarily, with the FIP outbreak.

Some scientists now call for a ban on cats coming from Cyprus, but politics may not make that possible. “The UK is particularly at risk as there is quite a lot of traffic of cats from Cyprus to the UK, either from the two army barracks, or via rescue centres,” says Dr. Gunn-Moore. Because cat shows often host cats from all over the world, the Governing Council of the Cat Fancy has implemented new rules/cautions for cats imported from at-risk locales.

How to Test Cats

Ideally, testing cats could help protect healthy felines from those infected and shedding the virus. Unfortunately, just because a cat tests positive for feline coronavirus doesn’t mean they have FIP—and tests can’t differentiate between the innocuous form of FCoV and the new FCoV-23, says Dr. Gunn-Moore.

“That said, cats that are serologically negative are less likely to be shedding (but this is not at all guaranteed). And cats with high titers are more likely to be shedding (and we can therefore sequence the virus to see if it is FCoV-23, or not). If you use the quantitative RT-PCR (qRT-PCR) you get an idea of how much FCoV is being shed, which can be very useful as high shedders carry a bigger risk of spreading the infection,” she says.

“So what is an ideal test? We simply don’t know.” Besides, she says some cats may intermittently shed virulent virus and get through the testing without detection.

Best Advice from the Experts

According to Dr. Gunn-Moore, “Perhaps the minimal that should be done is at least serology and faecal qRT-PCR for FCoV.”

The qRT-PCR (Real-Time Quantitative Reverse Transcription PCR) is considered the gold standard for quantifying circulating miRNAs with high sensitivity and specificity and with a wide analytical measurement range. The test enables reliable detection and measurement of products generated during each cycle of PCR process.

“If they are both negative, quarantine the cat for 3 weeks before introducing other cats. Ideally, repeat both tests, or at least the qRT-PCR for FCoV,” she says.

“We certainly need to prevent cases escaping. However, there is no consensus on the best way to do this yet, but here is my advice. The best thing to do by far is not to bring any cats in from Cyprus, or Greece at present or, potentially, more countries in that area.”

“Sadly, it is a case of ‘watch this space,‘” says Dr. Gunn-Moore.

UPDATE: Morris Animal Foundation and EveryCat Health Foundation have partnered to further study this situation. Read more here.