Types of FIP: Ocular vs. Neurological FIP

Feline Infectious Peritonitis (FIP) is a serious viral disease caused by a mutation of feline coronavirus (FCoV). While most FIP cases fall into wet (effusive) or dry (non-effusive) categories, some cats develop atypical dry FIP that affects specific organs, particularly the eyes or nervous system. These forms are called ocular FIP and neurological FIP.

Unlike the more obvious wet FIP, these forms can be subtle, harder to diagnose, and more complex to treat. However, thanks to advances in antiviral treatments like GS-441524, cats with ocular or neurological FIP now have a real chance of recovery—if detected early.

👁️ What is Ocular FIP?

Ocular FIP is a type of dry FIP where the disease causes inflammation within the eye, especially the uvea (the middle layer of the eye that includes the iris, ciliary body, and choroid).

🔍 Symptoms of Ocular FIP:

• Uveitis: Painful inflammation in one or both eyes

• Eye discharge: Often watery or mucus-like

• Change in eye color: Blue or cloudy appearance

• Iris abnormalities: Uneven pupils, blood vessels visible in the iris

• Blindness: Partial or complete, may develop suddenly

Ocular FIP may be the only visible sign of the disease for weeks or months, making it critical to investigate unexplained eye problems in young cats, especially those recently stressed (e.g., adoption, surgery, boarding).

🧠 What is Neurological FIP?

Neurological FIP is the most severe and complex form of dry FIP, where the virus invades the central nervous system (CNS), affecting the brain and/or spinal cord.

🔍 Symptoms of Neurological FIP:

• Ataxia: Loss of balance, wobbly

• Head tilt or abnormal posture

• Tremors or muscle twitching

• Seizures or collapse

• Behavioral changes: Confusion, aggression, pacing

• Incontinence or inability to walk

Neurological signs typically develop later in the disease progression, but they can also emerge suddenly. This form of FIP is often misdiagnosed as epilepsy, stroke, or other neurological diseases.

🔄 How Ocular & Neurological FIP Develop

Both ocular and neurological FIP are considered variants of dry FIP, where the virus does not cause fluid buildup but instead causes granulomatous inflammation in specific tissues.

Pathogenesis Summary:

1. A cat is exposed to feline coronavirus (FCoV).

2. In some cats, the virus mutates into the FIP-causing strain.

3. If the mutated virus bypasses the immune system and reaches the eyes or brain, it causes localized inflammation.

4. The disease may start in another form (e.g., abdominal FIP) and later progress to ocular or neurological involvement.

Some cats may present with both ocular and neurological FIP simultaneously, further complicating diagnosis and treatment.

🧪 Diagnosis Challenges and Signs to Watch

Because these forms of FIP mimic other conditions, diagnosis requires a combination of clinical signs, imaging, and supportive lab tests.

Ocular FIP Diagnostic Clues:

• Eye inflammation not responding to antibiotics or steroids

• High globulin levels and low albumin in bloodwork

• Ocular ultrasound revealing internal eye lesions

• PCR tests (when available) of ocular fluid
  

Neurological FIP Diagnostic Clues:

• Progressive neurological symptoms in a young cat (<3 years old)

• Elevated protein in cerebrospinal fluid (CSF)

• MRI or CT imaging showing CNS inflammation

• Rule-out testing for epilepsy, tumors, or trauma

Note: Definitive diagnosis of neurological FIP is difficult without invasive testing, so many veterinarians proceed based on clinical suspicion, especially when neurological signs follow known FIP exposure or symptoms.

💊 Treatment Approach and Prognosis

Treatment for Both Types:

• GS-441524 remains the most effective antiviral treatment.

  • Oral or injectable form

  • Minimum of 84 days (12 weeks); longer for neurological cases

• Supportive care: Anti-inflammatories, pain management, fluids

• Eye-specific care: Eye drops (e.g., corticosteroids or NSAIDs)

• Neurological monitoring: Seizure control, physiotherapy
  

Key Considerations:

Type	Treatment Notes	Prognosis
Ocular FIP	Responds well to GS; may need topical support	Good if treated early
Neurological FIP	Requires high-dose GS; longer treatment	Guarded but improving with early care

Cats with neurological FIP often need higher doses of GS-441524 and longer courses (12–16+ weeks). The earlier the treatment begins, the better the chances of full recovery, even in severe cases.

🚨 Final Tips for Cat Owners in the USA

• Any eye or nervous system symptoms in young cats, especially those in shelters, catteries, or recent stress, should raise suspicion of dry FIP.

• Don’t delay testing or treatment. Waiting could allow the virus to spread further.

• CureFIP USA offers oral and injectable GS treatments, dosage guidance, and case support to give your cat the best possible chance of survival.
  

💬 Questions or Suspect FIP?

If your cat is showing signs of ocular or neurological FIP, reach out to your veterinarian or contact CureFIP USA for treatment assistance and recovery support.