Feline infectious peritonitis

Newsletter European Advisory Board On Cat Diseases
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What is feline infectious peritonitis?

• Feline infectious peritonitis (FIP) is caused by feline coronavirus (FCoV).
• Infections caused by FCoV occur in all environments, but above all they are common in environments with a high cat population density.
• FIP will only develop in a certain proportion of infected cats.
• Cats that have suffered stress are susceptible (adoption, neutering, shelter).
• FIP occurs mainly in cats aged <1 and in environments with a high population density of cats.
• Purebred cats seem to be more susceptible.
• FCoV can survive for about 2 months in a dry environment
• FCoV is easily inactivated with cleaning and disinfecting agents.

Infection

• The main source of FCoV infection is the faecal secretions of infected cats. Transmission of infection through saliva or during pregnancy is rare.
• FCoV can also be transmitted indirectly (waste trays, shoes, clothing)
• Cats begin to shed the virus within the first week after infection and continue to shed for the following weeks or months, sometimes throughout their lives.
• FIPs cause FCoV variants (mutants) that multiply more rapidly in macrophages and monocytes.
• The development of FIP depends on the viral load and the immune response of the cat.

Clinical signs

• Most FCoV-infected cats remain healthy or show only mild signs of enteritis.
• Common initial symptoms of FIP are fluctuating fever, weight loss, anorexia, and depression.
• As the disease progresses, FIP manifests itself
  • in its effusive (wet) form, characterized by chronic inflammation of the membranes (accumulation of fluid in the abdomen, thoracic and / or pericardial effusion) and inflammation of the vessels;
  • in its non-fusion (dry) form, characterized by granulomatous lesions of various organs (enlargement of the kidneys, chronic diarrhea, swollen lymph nodes).
• These forms are considered to be clinical extremes of the same condition.
• Symptoms in the eyes include uveitis, corneal clots ("lamb fat") in the anterior chamber of the eye, perivascular retinal infiltrate and pyogranulomatous chorioretinitis.
• Neurological symptoms (in ~ 10 %) include ataxia, hyperesthesia, eye twitching, convulsions, behavioral changes, and cranial nerve disorders.
• Clinical symptoms are highly variable and vary depending on the distribution of the lesions.

Diagnosis

• There is no non-invasive test available to confirm the disease in its dry form.
• Laboratory findings suggestive of FIP include lymphopenia, non-regenerative anemia, elevated serum total protein, hyperglobulinemia, low albumin / globulin ratio, high α-1 acid glycoprotein levels, and high FCoV antibody titers.
• The high value of FCoV antibody titers alone is not significant for diagnosis.
• Effusions suggestive of FIP show positive Rivalt test results, high protein values, and low albumin/globulin ratio and contain neutrophils and macrophages.
• FCoV antigen-positive cells (immunofluorescence, immunohistochemistry on biopsy material from pyogranulomas or cell sediment from accumulated fluid in the abdomen) confirmed in specialized laboratories will confirm FIP.
• FCoV RT-PCR of blood samples is not sufficient to make a diagnosis: FIP-inducing mutants and "normal" FCoV cannot be distinguished.

What to do when the disease occurs

• The FIP forecast is very poor. The average survival time after diagnosis of the disease is 9 days.
• Euthanasia should only be considered after the final diagnosis of the disease.
• Supportive care is aimed at suppressing inflammation and the damaging immune response, usually corticosteroids. Nevertheless, its benefits have not been proven.
• In a household where a cat has undergone FIP, it is recommended to wait 2 months before bringing a new cat. Other cats in the same household are probably FCoV carriers.
• FIP is a problem of joint breeding of several cats (rearing of young and shelters), it only rarely occurs in domestic cats and in free-range cats.
• A reduction in the risk of contamination can be achieved by maintaining strict hygiene and keeping cats in small, well-adapted groups, whose waste trays are often cleaned and where cats have free movement.
• Cats shedding FCoV can be identified by real-time quantitative RT-PCR screening of faecal secretions, but multiple sampling (4 x over 3 weeks) is necessary.

Vaccination

• FIP is not part of the basic vaccines.
• There is only one (intranasal) FIP vaccine available in the US and some European countries.
• The vaccine is not effective in cats that have already been infected with FCoV, but may be useful in seronegative kittens before they enter the endemic environment.
• If vaccination is considered, the first dose should be given before the age of 16 weeks.