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April 12, 2024 — Since the recent COVID-19 pandemic, it's unusual to find someone who doesn't know about coronaviruses. Many coronaviruses circulate in many different species of animals and humans, and sometimes, these viruses can take a sinister turn.  

A deadly viral disease known as feline infectious peritonitis has affected wild and domestic cats worldwide for decades. The virus responsible for the disease is a coronavirus, but a peculiar one. The feline contagious peritonitis virus only affects cats. Almost all cats eventually encounter the mutant form of the common feline coronavirus (FCoV). 

In a small percentage of cats, the benign virus mutates for reasons not entirely understood as the deadly FIP virus, resulting in severe and fatal disease. Interestingly, the mutation can differ in different cats and seems to depend on a cat's immune response, genetics, stress, breed and environment.   

Adding to the confusion is that although the mutant virus can be present in cats, according to experts, only a tiny percent of cats get sick, roughly 5%.   

FIP can develop weeks, months, or years after initial exposure to FCoV.  

Male cats appear more likely to develop FIP than females. FIP mainly affects young cats, typically under 3 years old, although older cats can occasionally develop the disease. 

Researchers believe that pure-bred cats face a higher risk, with certain breeds potentially predisposed, such as Abyssinian, Bengal, Birman, Himalayan, ragdoll and Devon rex. 

Not surprisingly, the disease is more common in multi-cat living situations, including shelters, rescues and multi-cat households. However, cats living alone can develop the disease since exposure to FCoV often occurs early in life.  

Signs and symptoms
Many cat owners might be familiar with the terms "wet" and "dry" in relation to the two forms FIP can take. The form relates to an infected cat's immune response against the virus. Different signs are associated with each form, as described below.   

Cats infected with the milder FCoV usually don't show any signs of disease, although a few will develop mild respiratory signs or mild diarrhea.   

The signs of FIP are much more severe and include:  

  • Lethargy  
  • Anorexia or decreased appetite  
  • Swollen abdomen (due to fluid accumulation associated with the wet form of FIP)  
  • Difficulty breathing (due to fluid accumulation associated with the wet form of FIP)  
  • Red eyes, cloudy eyes, blindness  
  • Abnormal behavior, other neurologic signs  
  • Waxing and waning fever  

Despite what we know about FIP, diagnosing the disease can be challenging.  

In many cases, the history and physical exam findings can often suggest FIP. Some practitioners consider FIP a diagnosis of exclusion, meaning your veterinarian may perform tests to rule out other diseases before diagnosing FIP. 

Unfortunately, veterinarians cannot efficiently perform 100% accurate tests on cats to confirm the diagnosis before death.  

For many, many years, there was no treatment available for FIP other than supportive care, with a reported 95% mortality rate. However, in the last few years, this has changed. Some medications can help, but this is where the story gets complicated.  

Foundation-funded researchers discovered a drug, GC376, that could slow the progression of FIP. The drug worked well in field trials but wasn't perfect. However, it represented one of the first times a therapy slowed or stopped the disease. The drug is under review by the FDA.  

Dr. Niels Pedersen, one of the world's foremost authorities on FIP, conducted the field trial of the drug mentioned above. Given the partial success, Pedersen uncovered other effective treatments for slowing progression and achieving cures. Remdesivir (yes, the same drug approved for emergency use of COVID-19 in people) and a closely related drug, GS-441524, are currently in use in other countries (and recently approved in Canada). Another drug that has shown promise in treating the disease (although controversial) is molnupiravir.   

Hopefully, the United States will soon make these drugs available, following the lead of other countries.  

It's important to note that for several years, these drugs were only available illegally from various sources. Not surprisingly, the quality of these medications can vary wildly, and cat owners seeking information about therapy must be cautious.  

What to do if there are other cats in the Household  
Many pet parents who have a cat diagnosed with FIP are understandably worried about disease transmission to other cats in a household. They also may be concerned about losing a cat to the disease but want to get another cat or kitten.  

However, there are steps cat owners can take to minimize the risk of disease. Experts suggest:  

  • Waiting one month after a cat dies in a single-cat household before bringing another cat home.  
  • Waiting three months if a cat dies in a multi-cat household before adding another cat, just to ensure any remaining cats do not become ill.  
  • Ensure adequate numbers of cat boxes are in the Household to minimize exposure.  
  • A dilute bleach solution (bleach to water ratio of 1:32) is enough to kill the virus — disinfect where possible.  

What's The Deal with The Cats in Cyprus? 
In early 2023, there were reports of an outbreak of an FIP-like illness affecting large numbers of cats in Cyprus. Given what we know about FIP, this was both peculiar and alarming.   

In the past year, researchers worldwide have investigated what was happening in Cyprus and determined its significance for cat populations worldwide.  

There are still many questions about the outbreak, which continues to affect cats in Cyprus, but we know a few things. The new virus has been named FCoV-23.  

The disease is spread in feces, similar to how FCoV spreads. However, this virus form does not appear to need to mutate to something virulent in a cat – it's already infectious. Although confirmed case counts are low, a report from Science Magazine (November 14, 2023) suggests 10,000 cats had died from the disease. The virus also seems unique – the new strain of feline coronavirus contains genetic material from a highly transmissible canine coronavirus, likely accounting for the high degree of infection.  

The new virus was found in cats imported to the United Kingdom from Cyprus (yikes), which has understandably caused concern among cat owners in Europe. Although no outbreaks have been reported in other countries yet, scientists are closely monitoring the situation, hoping the reported cases of this deadly variant do not expand to other regions.  

How has Morris Animal Foundation helped?
About 50 years ago, researchers first described FIP. Since 1986, the Foundation has funded 32 FIP grants, giving away more than $2.5 million to fund innovative studies focused on projects ranging from basic bench research to improvements in diagnostic testing to vaccine development.   

We are proud of our funded researchers, especially now as we have seen many of these same researchers recognized for their outstanding work on coronaviruses during the COVID-19 pandemic, lending their expertise and lessons learned from FIP in cats.  

A notable example is Dr. Gregg Dean, Professor and head of Colorado State University's Department of Microbiology, Immunology and Pathology. Dr. Dean's laboratory is developing vaccines and diagnostic tests for FIP.  

Dr. Gary Whittaker is another Foundation-funded coronavirus researcher in the news. He is a Professor of Virology in the Department of Microbiology and Immunology at Cornell University. Researchers worldwide working on solutions for the current pandemic have been drawn to his work on the basic biology of feline coronavirus, including how it infects cells. 

As mentioned above, our funding led to the first antiviral treatment for cats with FIP. Developed by Dr. Yunjeong Kim, Associate Professor in the Department of Medicine and Pathobiology at Kansas State University, GC376 is one potential therapeutic in the FDA approval pipeline.  

We're also working on a collaboration with EveryCat Health Foundation to address the crisis in Cyprus. Stay tuned for more updates.  

Science to Save Animals Starts with YOU 
Without your help, we would not be able to support the research needed to eliminate the impacts of FIP on cats, kittens, and their people. We've made unprecedented strides in treatment in the last few years, but we still need better diagnostics and preventives.  

Learn how to support the science that can help pets live longer, healthier lives. Whether you create a tribute for a beloved furry friend, become a monthly donor, or simply share our message, you're helping us fund the most impactful animal health research tackling today's and tomorrow's health emergencies for our pets and wildlife.  

DONATE TODAY to support science that saves animals.