Feline Infectious Peritonitis Virus Can Remain Dormant For Years

March 15, 2017

Feline Infectious Peritonitis (FIP) is a serious disease that targets young cats most commonly. It is thought to come from a virus called feline enteric coronavirus (FECV) that normally has no clinical signs or causes mild diarrhea, but it may mutate to a more active disease, causing FIP to develop. 

Signs of FIP

The signs of FIP are seen in less than 10% of FECV-infected cats, and are produced because of a very aggressive immune system reaction to the virus. The virus can cause disease within two weeks after exposure or it can remain dormant in some cats for months to years, or may never produce symptoms of disease. 
There are two forms of FIP infection: 
  1. The wet form results in a build-up of fluid in the chest cavity leading to breathing difficulties, or in the abdominal cavity causing a large, bloated belly appearance. 
  2. The dry form affects the internal organs of the body, but no fluid is produced. 
Because various body systems can be affected by disease, clinical signs of FIP can be quite variable.
Non-specific signs may include:
  • lethargy
  • fever
  • gradual loss of appetite
  • poor hair coat
  • weight loss
Clinical signs often reflect which body system is affected. For example, blindness may be seen with an eye infection, seizures may occur with brain involvement, jaundice with liver dysfunction, or breathing difficulty if fluid surrounds the lungs in the chest cavity.
In the dry form, nodules of inflammation may appear in the abdomen tissues (kidney, intestine wall, mesentery) leading to organ function problems.
The final stage of illness (dry or wet form of FIP) generally lasts only a few weeks and usually ends in death. Recovery is extremely rare.

Risk Factors

Genetics may play a role in FIP susceptibility in certain breeds (Birman and Persian, amongst others).
Cats with FECV infection shed or pass virus into the environment for several weeks to months after initial infection. Shedding normally occurs in the feces, and briefly in saliva. The virus is highly infectious and acquired through oral contact, often indirect through exposure to infected litter. Most cats clear FECV after two to three months of shedding, but may become susceptible to re-infection after a period of time.  
Persistent infection with FECV may occur in 13% of cats causing a chronic carrier state and prolonged fecal shedding. There is no evidence that cats infected with FIP will transmit the virus to another cat, except in rare outbreak conditions. 

Where can a Cat become Infected with FECV?

Catteries or other facilities where cats are mixed together provide a higher risk of infection/transmission of FECV. During the transmission risk period, the infected cat with FECV does not show any signs of disease. This stage before signs show may last for several months or even years.
FIP infection often develops a few months after a period of stress. Increased virus shedding and a reduced immune response may increase the risk for developing FIP infection.  


Diagnosis of FIP can be both difficult and frustrating since there are no specific tests that can reliably differentiate FECV infection from the more aggressive FIP infection. Newer DNA-based tests (RT-PCR) with supportive IFA (immunofluorescent antibody) testing on specific tissue samples are more accurate than previous tests.
A tentative diagnosis is often based on a combination of blood tests, fluid analysis, X-rays and biopsies. There is no effective treatment available for FIP infection and progressive clinical signs are associated with a grave prognosis.  Palliative therapy may be provided, but euthanasia is usually recommended with progressive signs. 

Prevention, Treatment

Even though a vaccine against FIP was developed, veterinarians have not recommended routine vaccination against FIP since the vaccine interfered with disease monitoring and had limited effectiveness.  
Treatments such as interferon, anti-inflammatory therapy and other novel treatment options have been attempted, but no therapies are known to be effective for cure once generalized disease develops. Anti-inflammatory therapy (steroids) and drainage of fluid from the body cavities may provide short-term comfort.
To learn more about disease prevention, talk to your veterinarian. This is particularly important with breeding cats because early weaning, hygiene, and isolation procedures may help to break the transmission cycle. 
Dr. Kathleen Cavanagh, Consulting Online Editor CVMA
Dr. Beth Hanselman, Specialist Consultant
March 31, 2017