Herpes Viral Conjunctivitis in Cats 🐱👁️

By Dr Duncan Houston, BVSc

Feline herpesvirus-1 (FHV-1) is the most common cause of conjunctivitis in cats. This contagious virus can cause red, watery eyes, squinting, and recurring respiratory symptoms. While the virus never truly goes away, flare-ups can be managed effectively. 🧪

🔬 What Is Conjunctivitis?

The conjunctiva is the pink membrane lining the eyelids and eye socket. When inflamed, it causes:

• 🔴 Redness and swelling
• 💧 Watery discharge
• 😿 Squinting and eye rubbing
• 👁️ Corneal ulcers or cloudy eyes in severe cases

Herpes conjunctivitis is viral, recurring, and often accompanies upper respiratory infections (URIs). The initial infection is usually the most severe. 😷

🦠 Understanding Feline Herpesvirus

FHV-1 infects mucosal tissues (eyes, nose, mouth). After the first episode, the virus becomes dormant in a nerve cluster (the trigeminal ganglion). Later, stress triggers flare-ups of conjunctivitis and sneezing. 🤧

Typical Triggers:

• 🚚 Moving homes
• 🏥 Vet visits
• 🐱 Adding a new pet
• ❄️ Weather or illness

👶 Herpes in Kittens

Young or neglected kittens (feral, shelter, or outdoor) are at high risk. They may suffer from:

• 🧼 Eyes glued shut with discharge
• 👁️ Severely swollen conjunctiva hiding the eye
• ⚠️ Corneal rupture if left untreated

Manual eye cleaning and early vet treatment can prevent blindness. Hospitalization may be needed for antibiotics, fluids, and feeding. 🐾

🐾 Symptoms in Adult Cats

• 😿 Squinting or partial eye closure
• 💧 Brownish or watery discharge
• 🔴 Red or swollen conjunctiva
• 🔁 Flare-ups after stress or illness

🧪 How Is It Diagnosed?

PCR testing can detect herpes DNA in eye swabs—but herpes is so common that most cats test positive even when healthy.

Diagnosis is usually based on:

• 👀 Symptoms
• 🧫 Response to treatment
• 🧬 Optional PCR or antibody testing

💊 Treatment Options

1. 🧫 Topical Antibiotics

• 💉 Do not affect the virus itself
• 🦠 Help manage secondary bacterial infections
• ✅ Often enough for mild flare-ups

2. 👁️ Topical Antivirals

• 💧 Cidofovir (twice daily)
• 💧 Trifluridine (Viroptic®) – 4-5x daily
• ⚠️ Must be compounded or special-ordered

3. 💊 Oral Antivirals

• 💊 Famciclovir (human herpes med)
• 💧 Secreted in tears for localized effect
• ✅ Good option for cats that resist eye drops

4. 🌿 Supportive Options

• 🍽️ Fortiflora® probiotics may reduce severity
• 💧 Hyaluronate drops keep eyes moist and support mucous membranes

⚠️ Long-Term Complications

1. 👁️ Eosinophilic Keratitis

Immune system reaction to the virus causes white plaques on the cornea. Diagnosed by identifying eosinophils under the microscope. 🧪 Requires immune-suppressing eye meds and lifelong treatment.

2. 🧱 Corneal Sequestrum

Most common in Persian breeds. A portion of the cornea dies and turns black. May require surgical removal and grafting. Specialist referral advised. 🏥

💉 Can It Be Prevented?

• 💉 Vaccination reduces severity but does not prevent infection
• 😺 Most cats are exposed early in life
• 🧼 Minimize stress, crowding, and illness to reduce flare-ups

📱 Ask A Vet App Support

Unsure if your cat has herpes or another eye issue? The Ask A Vet app can help you:

• 📸 Upload photos for quick vet review
• 💬 Discuss antiviral options for chronic cases
• 🧾 Learn when to see a specialist
• 🕐 Set reminders for medication dosing

🏁 Final Takeaway

Herpes conjunctivitis is chronic—but manageable. With the right treatment and care, most cats recover quickly and live comfortably despite flare-ups. If your cat shows eye redness, squinting, or discharge, get them examined promptly—and don’t forget, stress management and immune support go a long way. 🐱👁️❤️