Feline Corona Virus and FIP in Cats

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. Strategies that eliminate stress on the immune system and prevention of transmission by isolating kittens have helped by preventing FIP from ever getting established.


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


Corona virus 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 (WBC) and macrophages of the immune system. Inside these cells, it travels through the blood stream moving FIP out of the gut. The infected viral cell attaches to vessel walls or organs while virus replicates in the WBC and ruptures, releasing thousands of viruses. This release of virus and rupture of cell causes inflammation and vasculitis.
  • Vasculitis causes fluid leakage and is responsible for fluid buildup in body cavities known as the Effusive form.
  • When inflammation happens in the cavity linings and organs, the non-effusive or Dry form of FIP happens.


Diagnosis is difficult as fewer than 10% of the cats with feline corona develop FIP! Why one cat and not another get FIP when both carry corona virus is not well understood. 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 Corona virus that makes it become FIP. That will set the stage for effective diagnostics, treatments and preventions for FIP in the future.


Testing for corona does not help manage away from FIP because we can’t distinguish the enteric corona from FIP!
  • There is an FCoV antibody test that is said to be faster and is being used by breeders. 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 still difficult to interpret. This test is often used for 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.


Treatment 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. Responses are generally considered transient and the diagnosis of FIP is accompanied with a negative prognosis long term.

Recently, Polyprenyl Immunostimulant has been used successfully with the dry form with 2 of 3 cats alive at 24 months but more work is needed to be done to call this a treatment. Supportive care and decrease in the inflammatory response is basis of treatment. Most FIP patients are euthanized because of disease course side effects.


  • Don’t introduce a new cat into a household where an FIP cat has died for 3 months. Corona virus survives for weeks in environment.
  • Remember older cats are more resistant to corona infection than 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 corona virus.
  • Purebred kittens get exposed from mom or contaminated environment with most infections happening around 9-10 weeks. Isolation for “bio-security” after weaning (6-12 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 kitten healthy.

Dr. Whittaker and Cornell’s Veterinary college 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 need help, call us at 1-800-786-4751.

-Dr. B
Don Bramlage, DVM, Director of Veterinary Services at Revival Animal Health

The materials, information and answers provided through this website are not intended to replace the medical advice or services of a qualified veterinarian or other pet health care professional. Consult your own veterinarian for answers to specific medical questions, including diagnosis, treatment, therapy or medical attention.

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