Veterinary Help

Feline Infectious Peritonitis (FIP) is a progressive and fatal disease of cats caused by a feline corona virus. Typically the feline enteric corona virus replicates in the intestines causing only mild gastrointestinal disease in young cats and kittens. Another form of the virus, FIP corona virus, is more tissue invasive and can cause severe disease in some cases. The enteric corona virus can mutate and become the more virulent FIP form of the virus. While advances in understanding the disease have been made, there is still much that is not well understood in the areas of which cats are infected and why, viral shedding, treatment and vaccination.

The enteric corona virus and the FIP form are shed most effectively in feces and oropharyngeal secretions. Infection is mainly oronasal through contact with infected stool. Infected cats may shed the virus prior to showing clinical signs and carrier cats do exist though their significance is uncertain. The virus can persist in the environment for weeks but is destroyed by most common disinfectants and detergents. Infection with the enteric corona virus is widespread with most infections being mild or asymptomatic. The factors which influence the development of the fatal forms of FIP are not completely understood and include the cats age at infection, the magnitude of the immune systems response, genetics, recent stress and the strain of the virus which has infected the cat. Affected cats are most often between 3 months and 3 years of age. There is also an increased incidence in geriatric cats. Stresses that may be associated with development of the disease include concurrent infections, surgery, pregnancy in a young cat or weaning and moving to a new environment.

There are 2 types of FIP syndromes, wet and dry. Initial clinical signs of both are similar and nonspecific including fever, lethargy, decreased appetite and possibly diarrhea. With time, cats typically lose weight and have a recurrent or persistent fever with resulting lethargy and lack of interest in food. The wet form is so called due to development of effusions in either the abdomen (ascites) or chest (pleural effusion). There can also be fluid buildup around the heart. These cats may have a distended abdomen or difficulty breathing. In the dry form, instead of effusions, granulomas develop in various organs. Almost any organ can be affected including the liver, spleen, lymph nodes, kidneys, nervous system or eyes. The clinical signs depend on the organs affected.

The only way to truly diagnose the disease is by histopathological exam of infected tissues from a biopsy or at necropsy. This being the case, FIP is not a quick diagnosis in the hospital setting as is the case with several other feline viruses. The effusions produced in wet FIP do aid in diagnosing this form of the disease as there are characteristic changes commonly seen in the fluid. There are also lab work changes that are common in FIP infection such as elevated white blood cell counts, elevated protein and liver levels but these changes are not specific for this disease. Viral titers can be used to detect exposure to the feline corona virus but exposure does not equal disease since may cats with positive titers will never develop FIP. Diagnosis is typically made based on clinical signs, consistencies on diagnostic tests and ruling out other diseases.

There is no treatment that addresses the virus directly. Since the disease process involves an abnormal immune response to the viral infection treatment focuses on suppressing the immune system. Steroids are often used for this as is the immunosuppressive drug cyclophosphamide. The disease is ultimately fatal even with immunosuppressive therapy. The best candidates for therapy are animals that are otherwise in good physical condition and still eating. These cats are the most likely to get an extended period of good quality of life from treatment.

In general, household cats in stable environments with no exposure to other cats outside the family are less likely to develop the disease compared to cats in a cattery or shelter. It is unclear at this time if the FIP vaccine that has been developed is prudent to give to household pets.