Note: If you are looking for information regarding COVID-19 in pets, please check out our blog post Coronavirus in Humans vs. Dogs and Cats written by Dr. Greer, DVM.

Feline Infectious Peritonitis (FIP) is one of the leading causes of infectious death in young cats. What causes Feline Enteric Corona, a common intestinal bug, to mutate to FIP, a deadly killer? We do not know. FIP is an inflammatory disease that has no definitive diagnosis and no definitive treatment. However, strategies that eliminate stress on the immune system and prevention of transmission by isolating kittens have helped prevent FIP.

How is Feline Coronavirus Transmitted

Feline Coronavirus is endemic in multi-cat households, shelters and catteries; meaning it is usually present! Corona replicates in the GI and causes at most a mild diarrhea with the virus passing in the feces for months after diarrhea subsides. Because feline Coronavirus survives in the environment for several weeks after recovery, the potential to transmit the virus directly is high. Coronavirus is spread through litter pans, grooming, toys and humans moving from area to area.

How Does Coronavirus Turn Into FIP

Coronavirus in cats routinely mutates and changes. Most are not an issue but when the mutation changes to FIP virulent-type Corona, it attacks the white blood cells (WBCs) and macrophages of the immune system. Inside these cells, the virus travels through the blood stream, moving FIP out of the gut. The infected viral cell attaches to vessel walls or organs while the virus replicates in the WBCs and ruptures, releasing thousands of viruses. This release of virus and rupture of cells causes inflammation and vasculitis.

• Vasculitis causes fluid leakage and is responsible for fluid buildup in body cavities known as the effusive form. Symptoms of this form include weight loss, fever, loss of appetite, lethargy, swelling of the abdomen and diarrhea. Most cats with the effusive form die within two months of showing symptoms.
• When inflammation occurs in the cavity linings and organs, the non-effusive or dry form of FIP is the result. Symptoms of this form include weight loss, fever, loss of appetite, lethargy, jaundice, disorientation, tremors, urinary incontinence and inflammation of the eye.

How to Diagnose FIP in Cats

Diagnosis of FIP in cats is difficult as fewer than 10 percent of the cats with feline Corona develop FIP. It is not well understood why some cats get FIP while others don’t. Cornell University is close to solving the issue. It appears purebred cats are predisposed to FIP, but one must be cautious with that statement as purebreds may be more likely to follow FIP disease.

Cornell University has found a set of spiked proteins and the genes that code them unique to FIP. These spiked proteins are responsible for the changes in the Coronavirus that make it become FIP. That will set the stage for effective diagnostics, treatments and preventions for FIP in the future.

Is There a Definitive Test for FIP in Cats

Testing for Corona does not help us avoid FIP because we can’t distinguish the enteric Corona from FIP.

• There is an FCoV antibody test used by breeders that is said to be faster. However FCoV antibody is not specific for FIP but picks up all Corona. So what do you do with a (+) cat?
• PCR testing is also non-specific; it will test (+) for any Corona but not specific for FIP. False (+) issue is still difficult to interpret. This test is often used with cavity fluid to confirm the presence of FIP out of GI area.
• Antec lab is trying to develop a specific test for FIP. It too has had false (-) results with report of (-) cats with clinical signs that were positive for FIP on necropsy. With Cornell’s new information, I am confident the research will get there at some point – not there yet.
• Most feline practitioners do not test, except to confirm virus outside the GI in face of FIP clinical signs. PCR for Corona RNA in the abdominal fluid is most commonly used.

How to Treat Cat FIP

Treatment of FIP in cats is not successful long-term, though steroids and other anti-inflammatory treatment is helpful short-term. Some reports of spontaneous remissions have occurred, and medical intervention has had a positive effect on the disease course. Positive responses are generally considered temporary; the diagnosis of FIP is accompanied with a negative prognosis long-term.

Recently, Polyprenyl Immunostimulant has been used successfully with the dry form. It has resulted in two of three cats alive at 24 months, but more work needs to be done to call this a treatment.

Supportive care and decrease in the inflammatory response is the basis of treatment. Most FIP patients are euthanized as side effects progress.

How Do You Prevent FIP in Cats      

• Don’t introduce a new cat into a household where a FIP cat has died in the past three months. Coronavirus survives for weeks in the environment.
• Practice routine disinfection of food and water bowls, cages and litter boxes.
• Remember older cats are more resistant to a Coronavirus infection than a new kitten. Bringing in an older cat has less risk and is often a better option.
• Most cats in catteries and rescues are infected with feline Coronavirus.
• Separate new litters of kittens and any cats that might be infected from the other cats.
• Purebred kittens get exposed from mom or contaminated environment with most infections happening around nine to 10 weeks. Isolation for bio-security after weaning (six to 12 weeks) has been helpful to avoid infection.
• Genetic factors are thought to influence the development of the virulent form of Corona or FIP. When a tom or queen has two or more infected litters, consider replacing with lower risk queen or tom.
• Prevent and treat respiratory disease and mild diarrhea to prevent chronic inflammation. We know chronic inflammation plays a role in FIP development. Breeders use L-lysine to prevent herpes virus (Rhinotracheitis virus) until vaccination immunity is completed. That will take chronic herpes virus out of the mix, helping to keep the kitten healthy.

Dr. Whittaker and Cornell’s Veterinary College’s research will set the stage for control and prevention of FIP. Stay tuned to the research as we are not there yet, but closer than ever before.

If you have more questions on feline FIP, call us at 800.786.4751.