Feline infectious peritonitis (FIP) is a viral disease in cats resulting from a mutated feline coronavirus. The disease has two main forms: “effusive” (wet), with fluid accumulation in body cavities, and “non-effusive” (dry). Non-effusive FIP is characterized by inflammatory reactions in various organs without significant fluid buildup. This article will cover the signs, diagnostic challenges, and treatments for this form of the disease.
Clinical Signs of Non-Effusive FIP
The clinical signs of non-effusive FIP are often subtle and develop gradually, making early recognition difficult. The presentation varies depending on which organ systems are affected by inflammatory lesions, known as granulomas. These lesions result from the body’s immune response to the virus.
Initial symptoms are often systemic and non-specific. A cat may present with a persistent fever that does not resolve with antibiotic therapy. This is commonly accompanied by lethargy, a poor or absent appetite, and subsequent weight loss. These general signs can persist for weeks before more specific symptoms develop.
Neurological involvement occurs when the virus breaches the blood-brain barrier, causing inflammation in the brain or spinal cord. This can lead to a variety of signs, including an uncoordinated gait known as ataxia. Owners might also observe seizures, partial paralysis, or uncharacteristic behavioral changes like confusion, disorientation, or sudden aggression.
The eyes are another common site for lesions in non-effusive FIP. Inflammation within the eye, called uveitis, may cause a cloudy or hazy appearance. Other ocular signs include a change in iris color, debris or fluid in the front chamber of the eye, or pupils of unequal size. In some cases, these eye-related symptoms may be the only outward sign of the disease.
The Diagnostic Process
Diagnosing non-effusive FIP is complex as no single test can definitively confirm it. The signs are often vague and mimic other conditions. A veterinarian reaches a presumptive diagnosis by combining the cat’s history and symptoms with results from a series of diagnostic tests.
Bloodwork is a primary step in the diagnostic workup. While no blood marker is exclusive to FIP, certain patterns are suggestive of the disease. Vets look for a high total protein level, specifically elevated globulins, alongside normal or low albumin. This combination results in a low albumin-to-globulin (A/G) ratio; a ratio below 0.4 is a strong indicator for FIP, while a ratio above 0.8 makes it unlikely.
Imaging techniques are used to visualize internal organs. An abdominal ultrasound is useful for identifying granulomas, or inflammatory lesions, on organs like the kidneys, liver, or abdominal lymph nodes. These lesions appear as nodules or irregularities, providing physical evidence that supports other clinical findings.
The only certain diagnosis of FIP is through histopathology, which involves a surgical biopsy of an affected organ. A pathologist examines the tissue for the specific inflammatory patterns caused by the FIP virus. Although definitive, this method is invasive and may not be suitable for cats that are already very ill.
Available Treatment Pathways
The treatment for FIP has changed significantly with the development of antiviral medications that target the virus’s replication. Previously considered fatal, modern therapies now offer a reliable path to recovery for many cats. The focus of treatment is to stop the virus from progressing.
One antiviral compound used is GS-441524, a nucleoside analogue that inhibits the viral RNA polymerase enzyme, halting viral replication. This medication is available as an injection or an oral formulation. The dosage and administration method depend on the disease’s severity and whether there is neurological or ocular involvement, which requires higher doses.
Another treatment option is Remdesivir, a prodrug of GS-441524. It is effective in treating FIP and is sometimes used with GS-441524. Treatment may begin with injectable Remdesivir in a hospital setting for critically ill cats, before transitioning to oral GS-441524 for the remainder of the course.
Alongside antiviral drugs, supportive care is important for managing symptoms and overall health. This can include appetite stimulants to combat weight loss, anti-inflammatory medications to reduce inflammation, and fluid therapy for dehydration. This approach helps stabilize the patient while the antiviral medication works.
Prognosis and Long-Term Outlook
The prognosis for Feline Infectious Peritonitis has improved significantly with modern antiviral treatments. Previously considered fatal, studies now show high success rates, with over 85% of cats that complete a full treatment protocol achieving clinical remission.
A standard course of therapy lasts for a minimum of 84 consecutive days, during which the cat is monitored for clinical improvement and weight gain. After the 84-day treatment, an observation period of another 84 days follows to ensure the disease does not return. Regular bloodwork helps confirm that inflammation is resolved and organ function is normal.
Relapse is not frequent for cats that complete the full treatment course, occurring in less than 10% of cases. Relapses are often associated with treatments that were too short, had inconsistent dosing, or in cases with severe neurological involvement. If a relapse occurs, retreatment at a higher dose is often successful. With appropriate and complete therapy, most cats can expect to live a full and healthy life post-FIP.