Feline infectious peritonitis, commonly known as FIP, is a grave viral disease affecting cats. It arises from specific strains of the feline coronavirus. While most feline coronavirus strains reside in the gastrointestinal tract and are benign, known as feline enteric coronavirus (FeCV), FIP develops from a mutated form. Typically, cats infected with FeCV show no initial symptoms, or only mild, temporary diarrhea or upper respiratory issues, recovering without intervention. Within 7 to 10 days of FeCV infection, cats usually develop antibodies, indicating an immune response. However, in about 10% of FeCV-infected cats, viral mutations can occur, transforming the virus into FIPV. This mutated virus infects white blood cells, enabling its spread throughout the cat’s body. The body’s immune system reacts intensely to FIPV, causing inflammation around blood vessels in affected tissues, often in the abdomen, kidneys, or brain. This interaction between the immune system and the virus leads to the development of FIP in cats.
FIP manifests primarily in two forms: the “wet form,” characterized by fluid accumulation in body cavities such as the abdomen and chest, and the “dry form,” which affects the central nervous system, leading to neurological symptoms. Once clinical FIP develops, the disease is typically progressive and almost invariably fatal if left untreated. Fortunately, effective therapies have emerged. Treatments have been available in countries like Australia and the UK for several years and have recently become accessible in the US as an oral compounded medication, requiring a veterinary prescription. This advancement marks a significant leap in veterinary medicine. If you suspect your cat has FIP, consulting with your veterinarian about these new therapies is crucial. It’s important to note that feline coronaviruses cannot be transmitted from cats to humans.
Cat with pot-bellied appearance due to fluid accumulation, a symptom of wet FIP
Is Your Cat at Risk of FIP? Who are fip cats?
Any cat that carries FeCV, the common and usually harmless intestinal feline coronavirus, is at potential risk of developing FIP. The mutation from FeCV to FIPV is the critical step. Younger cats are significantly more susceptible to FIP, with approximately 70% of cases diagnosed in cats under 18 months old, and half of these occurring in cats younger than 7 months. The primary mode of FeCV transmission is from infected queens to their kittens, typically between five and eight weeks of age. Transmission can also occur among mature cats through fecal contact. Cats in high-density environments like shelters and catteries are more prone to FIP, as are purebred, male, and geriatric cats, although the reasons for these increased risks are not fully understood. Understanding these risk factors is crucial for cat owners to be vigilant about the health of their Fip Cats.
Recognizing FIP Symptoms in Cats
Initially, cats exposed to FeCV often show no symptoms. Some may exhibit mild upper respiratory signs like sneezing, watery eyes, and nasal discharge, or mild gastrointestinal signs such as diarrhea. These symptoms are usually brief and resolve on their own. However, 5-10% of FeCV-exposed cats develop FIP, sometimes weeks, months, or even years after the initial FeCV infection.
FIP presents in two main forms: effusive (wet) and non-effusive (dry). Regardless of the form, cats with FIPV typically first show nonspecific signs like appetite loss, weight loss, lethargy, and fever. It’s important to note that the wet form of FIP can evolve into the dry form and vice versa, making diagnosis challenging.
The dry form of FIP generally progresses more slowly. Symptoms include the nonspecific signs mentioned earlier, alongside neurological signs such as seizures and ataxia (uncoordinated movements).
The wet form of FIP is characterized by a more rapid onset and progression. In addition to nonspecific signs, fluid accumulation in body cavities, particularly the abdomen and chest, is prominent. This fluid buildup can cause a pot-bellied appearance and breathing difficulties if excessive fluid accumulates in the chest. Recognizing these symptoms early is vital for fip cats to receive timely intervention.
Image depicting a cat undergoing a neurological exam, assessing for signs of dry FIP
Diagnosing FIP in fip cats
Unfortunately, there is no single definitive test for diagnosing FIP in fip cats. Antibody tests for coronavirus can measure titers, but they cannot distinguish between FeCV and FIPV exposure. A positive result only indicates prior coronavirus exposure, not necessarily FIPV. Despite this limitation, young cats with antibiotic-resistant fever and high coronavirus titers are often presumptively diagnosed with FIP, especially if characteristic fluid (yellowish, high in protein and white blood cells) accumulates in body cavities. Conversely, a healthy cat with a high coronavirus titer is not necessarily more likely to develop FIP. Immunocompromised cats with FIPV may not even show elevated coronavirus titers due to a weakened immune response.
Other tests aim to detect the virus directly. The immunoperoxidase test detects viral proteins in infected white blood cells in tissue biopsies. The immunofluorescence test detects viral proteins in tissue or body fluids. PCR testing detects viral genetic material in tissue or fluid. While helpful, these tests are not 100% accurate and can yield false negatives or positives.
In most cases, diagnosing FIP in fip cats involves considering the cat’s history, physical exam findings, and laboratory tests. A presumptive diagnosis is often made based on the combination of these factors.
Treatment Options for FIP Cats
Until recently, FIP was considered untreatable and almost always fatal for fip cats. However, recent advancements in antiviral drugs offer hope. While ongoing research continues to refine our understanding of these treatments—including long-term effectiveness, optimal dosage, resistance potential, and mechanisms of action—studies on GS-441524, the most extensively studied drug, indicate it is a safe and effective treatment for FIP. GS-441524 has been available in Australia and the UK for several years and recently became available in the US as an oral compounded formulation, requiring a veterinary prescription.
Prior to this regulated availability, black market sources offered GS-441524, but these products often varied in concentration and purity. The regulated US release is a significant improvement, ensuring reliability. If considering GS-441524 for your fip cat, discussing the risks and benefits with your veterinarian is crucial. Supportive care, including fluid therapy, drainage of fluids, and blood transfusions, may also be necessary.
Veterinarian administering medication to a cat, representing FIP treatment options
Protecting Your Cat from FIP
Preventing FeCV infection is the only definitive way to prevent FIP in fip cats. However, given FeCV’s widespread nature, this is challenging, especially in high-density environments. Housing cats at densities of three or fewer per room can reduce stress associated with overcrowding. While FeCV is highly contagious, spreading through feces and saliva, FIPV is not believed to be contagious itself. FIP develops when FeCV mutates to FIPV within an infected cat. Maintaining your cat’s overall health, including vaccinating against other viruses like feline leukemia virus and calicivirus, may reduce FIP risk. Clean litter boxes, located away from food and water, are also important. Isolating new cats or cats suspected of FeCV infection is sometimes suggested, though its effectiveness is debated.
A licensed FIP vaccine exists, but its effectiveness is questionable, and the American Association of Feline Practitioners Feline Vaccine Advisory Panel does not routinely recommend it. While safe, the vaccine’s benefits should be carefully weighed against its uncertain efficacy in consultation with your veterinarian to decide if vaccination is appropriate for your cat.
Updated 2024
