Feline Infectious Peritonitis (FIP) is a devastating and often fatal disease that affects our feline friends. It’s a progressive condition that can impact various systems within a cat’s body, and it’s caused by a mutation of the feline coronavirus (FCoV). This mutation, from a benign feline enteric coronavirus (FECV) to the more virulent feline infectious peritonitis virus (FIPV), is still a mystery to scientists. What we do know is that FIP is widespread, affecting not just domestic cats but also big cats like cougars, bobcats, lynx, lions, and cheetahs.
Understanding FCoV Infection and FIP Development
It’s quite common for cats to be infected with FCoV, with studies indicating that 25-40% of household cats, and up to 95% of cats in multi-cat environments, have been exposed. However, the progression to fatal FIP is relatively rare, affecting only 1 in 5000 cats in single or double cat households, and about 5% in multi-cat households.
Transmission of the Virus
FCoV is primarily transmitted through cat-to-cat contact and exposure to feces, typically in shared litter boxes. The virus can also be found in an infected cat’s saliva, and contaminated food or water dishes, bedding, and even personal clothing can serve as vectors. Interestingly, FCoV may also be transmitted in utero, although the implications of this are not yet clear. The virus can survive in the environment for up to 7 weeks, but its infectivity decreases significantly after 3 weeks. Regular cleaning and disinfection can help minimize the risk of infection.
The Immune System’s Role in FIP
When a cat encounters FCoV, the outcome hinges on the strength of its cellular immune system. A robust immune response can usually neutralize the virus, while a moderate response might result in a latent infection that could reactivate under stress. A weaker immune system, however, allows the virus to replicate and potentially lead to FIP. The damage caused by FIPV is often due to the body’s inflammatory response rather than the virus itself, with immune complexes and macrophages contributing to the formation of harmful granulomas.
Cats at Higher Risk for FIP
Young kittens, cats with feline leukemia virus (FeLV), and older cats often have the weakest immune defenses and are therefore more susceptible to FIP. Certain breeds, like Persians, may also be more prone to the disease, although the reasons for this are not entirely understood.
Clinical Signs and Symptoms
The clinical presentation of FIP can vary, with a spectrum of symptoms between the “wet” and “dry” forms. Dry FIP tends to progress more slowly, with symptoms like weight loss, fever, and organ damage. Wet FIP, on the other hand, is characterized by fluid accumulation in the chest and abdomen, leading to a rapid decline in the cat’s health.
Diagnosis and Laboratory Findings
Diagnosing FIP can be challenging due to the nonspecific nature of its symptoms and the limitations of antibody testing. A combination of history, clinical signs, lab results, and sometimes imaging studies is used to reach a probable diagnosis. The gold standard for diagnosis is histopathology, which involves microscopic examination of tissue biopsies.
Treatment and Supportive Care
Unfortunately, there is no cure for FIP. However, supportive care can help improve a cat’s quality of life and potentially extend it. This may include fluid drainage, nutritional support, antibiotics for secondary infections, and immunosuppressive drugs to reduce inflammation. Ongoing research is exploring new treatments, including antiviral therapies.
Prevention and Control Measures
Preemptive measures can help reduce the risk of FIP in multi-cat households and catteries. This includes maintaining clean litter boxes, separating cats into small groups, isolating new or potentially infected cats, and