How to detect Cat FIP?

The diagnosis of Feline Infectious Peritonitis (FIP) can be challenging due to the lack of specific diagnostic tests and the similarity of its symptoms to other feline diseases. FIP is caused by a mutation of the feline coronavirus (FCoV) and comes in two main forms: wet (effusive) and dry (non-effusive). Diagnosing FIP typically involves a combination of clinical signs, laboratory tests, imaging, and, in some cases, biopsy or post-mortem analysis.

Steps in Diagnosing FIP:

1. Clinical Signs

• Wet (effusive) FIP:

Accumulation of fluid in the abdomen or chest, leading to: Distended abdomen (ascites), Breathing difficulties (pleural effusion)
Fever that doesn't respond to antibiotics
Weight loss, lethargy, poor appetite

• Dry (non-effusive) FIP:

Granulomas forming in organs such as the liver, kidneys, brain, and eyes
Neurological signs (e.g., seizures, ataxia, behavioral changes)
Ocular changes (inflammation, retinal detachment)
Less obvious symptoms, making it harder to diagnose than wet FIP

2. Blood Work

• Complete Blood Count (CBC):

Anemia (low red blood cells)
Lymphopenia (low lymphocyte count)
Neutrophilia (high neutrophil count)

• Serum Biochemistry:

Elevated globulins (increased total protein levels, particularly gamma globulins)
Decreased albumin (leading to a high globulin-to-albumin ratio)
Increased liver enzymes and possible signs of kidney damage

3. Immunofluorescence and Immunohistochemistry

• Immunofluorescent antibody testing (IFA) can detect feline coronavirus in cells, though it cannot differentiate between the benign form of FCoV and the mutated FIP-causing form.
• Immunohistochemistry on biopsy tissue or effusion samples is often used to detect the presence of viral proteins, which can confirm FIP.

4. Effusion Analysis (for Wet FIP)

Cytology and biochemical analysis of the fluid collected from the abdomen or chest:
Typically yellow, sticky, and protein-rich fluid with high globulin and low cellularity
Rivalta test: A quick test performed on the effusion to distinguish between FIP and other causes of fluid accumulation. A positive test supports a diagnosis of FIP.

5. Imaging

Ultrasound or X-rays may show fluid accumulation, organ abnormalities, or lymph node enlargement. These can be suggestive of FIP but are not definitive.

6. PCR Testing

• Polymerase Chain Reaction (PCR) can detect viral RNA from tissue or fluid samples, but it often fails to differentiate between harmless feline coronavirus and the mutated FIP form.
• RT-PCR (reverse transcription PCR) designed to detect mutations specific to FIP is more accurate, though not 100% reliable.

7. Histopathology and Biopsy

Biopsy of affected tissues (especially in dry FIP cases) is often considered the gold standard for confirming FIP, particularly when analyzed with immunohistochemistry to detect viral proteins in the tissue lesions (granulomas).

8. Post-Mortem Diagnosis

In cases where a cat has passed away, a post-mortem examination can provide a definitive diagnosis by analyzing tissue samples from affected organs.

Summary:

The diagnosis of FIP is generally based on a combination of clinical signs, laboratory findings (such as high globulin levels, anemia, and a high globulin-to-albumin ratio), and imaging or effusion analysis. A definitive diagnosis often requires tissue biopsy and specialized testing.