Guide to FIP Disease in Cats: Wet and Dry FIP Symptoms, Early Diagnosis, and Treatment

01Biological Mechanism of Feline Coronavirus (FCoV) and FIP Mutation

At the root of FIP disease lies the Feline Enteric Coronavirus (FeCV), which is extremely common among cats and generally causes mild intestinal infections. A large majority of cats encounter this virus at some point in their lives and usually overcome the process with mild diarrhea or temporary upper respiratory symptoms. However, in about ten percent of infected cats, the virus undergoes a genetic mutation during its interaction with the host's immune system. As a result of this mutation, the virus is no longer a harmless agent multiplying only in intestinal epithelial cells, but gains the ability to infect immune cells called macrophages.

This mutated new form is called Feline Infectious Peritonitis Virus (FIPV). FIPV rapidly multiplies within the macrophages it infects and spreads throughout the body via the bloodstream. Infected macrophages circulating uncontrollably in the body trigger the onset of a severe inflammatory reaction (vasculitis) in the walls of the blood vessels. The extreme and pathological response of the cat's immune system to this situation leads to the deterioration of vascular permeability, the formation of granulomatous lesions in the organs, and ultimately the shaping of the FIP clinical picture. This process is directly related entirely to the cat's individual genetic predisposition, immune system response, and the mutation rate of the virus.

02Symptoms of Wet (Exudative) FIP: Fluid Accumulation in the Abdominal and Chest Cavities

FIP disease basically occurs in two different clinical forms or as a combination of these forms (mixed form). The first of these forms and the one that progresses most rapidly clinically is Wet (Exudative) FIP. The most characteristic feature of the Wet FIP picture is the leakage of plasma out of the vessels due to intense inflammation (vasculitis) in the vessel walls and the accumulation of a protein-rich, sticky fluid in the body cavities.

The most common clinical symptoms encountered in Wet FIP cases are as follows:

• Fluid Accumulation in the Abdominal Cavity (Ascites): A painless, symmetrical, and prominent swelling occurs in the cat's abdominal region. The owner often may think the cat has gained weight or is pregnant, but this is entirely due to fluid accumulation.
• Fluid Accumulation in the Chest Cavity (Pleural Effusion): In the event of fluid accumulation in the chest cavity, the expansion area of the lungs narrows. This causes rapid and shallow breathing, shortness of breath, open-mouth breathing, and profound lethargy in the cat. It is a medical condition requiring emergency intervention.
• Fluctuating Fever and Weight Loss: The cat experiences a persistent and fluctuating high fever that does not respond to antibiotic treatment. Due to loss of appetite, muscle mass wasting and rapid weight loss occur.
• Jaundice (Icterus) in Mucous Membranes: Due to liver involvement or intravascular hemolysis, yellowing may occur in the gums, the whites of the eyes, and the inner part of the ear flap.

03Symptoms of Dry (Non-Effusive) FIP: Neurological Involvements and Ocular Lesions

Dry (Non-Effusive) FIP is the form where there is no significant fluid accumulation in body cavities, but instead, small inflammatory foci (pyogranulomas) form in various internal organs, eyes, and the central nervous system. Dry FIP is considered the hardest form to diagnose due to the slower development of symptoms and the lack of fluid.

The prominent clinical symptoms encountered in the Dry FIP form are:

• Neurological Symptoms (Central Nervous System Involvement): Due to granulomas forming in the brain and spinal cord, unsteady walking (ataxia), loss of coordination in the hind legs, head shaking, walking in circles, nystagmus (involuntary trembling of the eyes), behavioral changes, and epilepsy-like seizures are observed in the cat.
• Ocular Lesions (Eye Involvement): Uveitis frequently develops in cats with Dry FIP. Cloudiness in the intraocular fluid, change in eye color (especially turning brown in light-colored eyes), intraocular bleeding, asymmetry in pupillary sizes, and sudden blindness due to retinal damage can occur.
• Internal Organ Granulomas and Palpation Findings: Enlargement and deformities occur in the kidneys, liver, and mesenteric lymph nodes due to granulomas forming in these organs. Irregular masses may be felt during abdominal palpation during the examination.
• Chronic Growth Retardation: Complete cessation of growth, especially in kittens, severe deterioration in coat quality, lethargy, and a picture of chronic anemia are among the first harbingers of dry FIP.

04Laboratory Diagnosis and Blood Parameters: A/G Ratio, Rivalta Test, and PCR

FIP diagnosis is a pathological process that cannot be definitively made with a single test. The diagnosis is like a jigsaw puzzle put together by combining clinical findings, hematological tests, biochemical analyses, and specific fluid examinations.

The main parameters used in the diagnostic process are:

• Albumin/Globulin (A/G) Ratio: While globulin protein levels increase due to the overstimulation of the immune system in cats with FIP, albumin levels decrease. An A/G ratio below 0.4 extremely strengthens the suspicion of FIP, while a ratio above 0.8 largely rules out the disease.
• Rivalta Test: A simple but highly guiding test applied to the effusion fluid taken from the abdominal or chest cavity. The precipitation reaction (positive Rivalta) that occurs when the fluid is dropped into an acidic solution indicates that the protein ratio of the fluid is high and is caused by FIP.
• RT-PCR (Real-Time PCR) Analysis: It is used to detect coronavirus RNA in samples taken from body fluids or organ biopsies. Performing FCoV mutation-specific PCR tests, especially on the effusion fluid, offers the greatest opportunity to confirm the diagnosis.
• Hemogram and Biochemistry Findings: Moderate-to-severe non-regenerative anemia, leukocytosis (neutrophilia), and lymphopenia are frequently seen in the blood count. In biochemistry, hyperproteinemia, elevated liver enzymes (ALT, AST), and high bilirubin are other medical evidence supporting the diagnosis.

06Current Treatment Protocols: Active Ingredient GS-441524 and Antiviral Applications

While only symptomatic support could be provided in FIP treatment until the recent past, direct treatment of the disease has become possible today thanks to advancements in virology. The main backbone of the treatment is the active ingredient GS-441524, a nucleoside analog that stops the virus from multiplying by inhibiting its RNA synthesis. This antiviral agent has made a breakthrough in FIP treatment, raising the survival rate of patients to over ninety percent.

The basic principles of the current treatment protocol are:

• Treatment Duration and Dosing: The standard antiviral treatment protocol lasts for 84 uninterrupted days (twelve weeks). The dose amount is adjusted millimetrically by the veterinarian according to the cat's weight and the form of the disease (wet, dry, neurological, or ocular involvement). Much higher doses are applied in neurological and ocular involvements since the blood-brain and blood-eye barriers must be crossed.
• Application Methods: In the first days of treatment, the injection (subcutaneous) form is preferred, especially in critical patients experiencing absorption problems; a transition to oral tablet forms can be made as the patient's clinical condition stabilizes and their appetite returns.
• Supportive Therapies: Alongside antiviral therapy, liver protectors, joint supplements, erythropoietin or iron supplements to suppress anemia, and other medical supports that balance the immune system should be included in the treatment.
• Routine Clinical Follow-ups: During the treatment, the hemogram and biochemistry panel (especially albumin, globulin, and liver-kidney values) are repeated on days 30, 60, and 84 to closely monitor treatment success and dose revision.

07Home Care and Quality of Life Steps for Owners of Sick Cats

The success in the treatment process of a cat diagnosed with FIP is directly related to the quality of care at home as much as to clinical applications. Physically and psychologically supporting the cat increases the speed of recovery. The essential steps to be taken at home during this process are as follows:

• Zeroing Out Stress Factors: Stress is the factor that suppresses cats' immune systems the most. Noise in the house, sudden environment changes, new pet introductions, or travel should be completely avoided during this period. A calm and dim room where the cat feels safe should be prepared.
• High-Quality and Appetizing Nutrition: The body's protein and energy needs increase throughout the treatment. Highly digestible wet foods recommended by your physician, fresh boiled meat broths, and immune-supporting foods should be preferred. In cases of anorexia, appetite-stimulating medical supports should be used under physician supervision.
• Hygiene and Isolation in Multi-Cat Households: If there are other cats at home, the FIP cat's litter box, food, and water sources must be completely separated. Because the coronavirus is transmitted through feces, litter boxes should be disinfected every day, and cleaning should be done throughout the house with antiviral disinfectants.
• Millimetric and Hourly Tracking of Medications: Oral or injection forms of antivirals must be administered at the same time every day, without interruption. Missing a dose or shifting the time can cause the virus to develop resistance.

08FIP Diagnosis, Follow-up, and Feline Infection Services in Mezitli, Mersin

In systemic infections like FIP that tend to progress rapidly and require immediate interventions, an equipped clinical infrastructure and an experienced veterinary team are of vital importance. As Anka Veterinary Clinic in our modern center in the Mersin Mezitli region, the diagnosis, follow-up, and management of current treatment protocols for FIP are carried out at international standards.

In our clinic, rapid blood counts, advanced biochemistry panels, effusion fluid analyses, and Rivalta tests for patients arriving with suspicion of FIP are concluded on the same day, preventing any loss of time. The 84-day follow-ups, laboratory controls, and dose adjustments of our patients undergoing antiviral treatment are managed with utmost care. Cat owners in Mersin Mezitli and surrounding areas are guided in their fight against FIP in light of the most up-to-date scientific data, keeping your pet's quality of life at the highest level.

You can visit our general checkup page for comprehensive health controls, and for emergencies, contact our emergency and intensive care service.

Frequently Asked Questions