Herpes Viral Conjunctivitis in Cats 👁️🐱

By Dr Duncan Houston, BVSc

Feline herpesvirus-1 (FHV-1) is a common culprit behind chronic and recurring eye infections in cats. Known as herpesviral conjunctivitis, this condition affects the conjunctival membranes of the eye—causing redness, discharge, and discomfort. In this 2025 guide, Dr Duncan Houston breaks down the causes, symptoms, treatment, and long-term management of this widespread feline condition. 🧬💧

🔬 What Is Conjunctivitis?

Conjunctivitis is inflammation of the conjunctiva—the pink tissue inside the eyelids and under the eyelid margins. In cats, herpesviral conjunctivitis affects this tissue and may also involve the cornea (the clear part of the eye), reducing tear production and increasing irritation. 👁️

🦠 What Causes Feline Herpesviral Conjunctivitis?

Feline herpesvirus-1 infects the eyes, nose, and throat. After the initial infection, the virus lies dormant in the trigeminal ganglion (a nerve center in the head). Under stress or illness, the virus can reactivate and cause repeat flare-ups. 😿

Key Features:

• 😷 Initial infection is most severe
• 🔁 Recurrences occur during stress or immune compromise
• 🧍 Contagious between cats—spread by contact or shared items

📋 Symptoms of Herpes Eye Infection

• 👁️ Red, irritated conjunctivae
• 💧 Watery or mucoid eye discharge (often brownish)
• 🙈 Squinting or partial eye closure
• 🫁 Sneezing, nasal discharge, or mild fever (respiratory signs)

🐾 Kittens Are Especially Vulnerable

Orphaned or outdoor kittens, especially under stress, often experience severe signs. Their eyes may crust shut, hiding infected discharge and risking blindness. 🔍

• 🧼 Eyelids may need to be manually opened for cleaning
• 💊 Immediate treatment can prevent eye rupture
• 🏥 Severe cases may need hospitalization and antibiotics

👨‍⚕️ Diagnosing Herpes Conjunctivitis

Veterinarians typically diagnose based on signs and history. PCR testing can confirm herpes DNA, but since most cats carry the virus, a positive result doesn’t always indicate active infection.

Diagnosis often rests on:

• 📖 History of stress + eye issues
• 📉 Non-response to standard antibiotics
• 🔍 Corneal involvement suggesting herpes

💊 Treatment Options

Treatment aims to relieve symptoms, prevent complications, and control viral replication. Multiple therapies are often combined:

1. 🧫 Topical Antibiotics

• Used to prevent or treat secondary bacterial infections
• Help reduce discharge and inflammation
• Examples: erythromycin, terramycin

2. 🧬 Topical Antivirals

• Target the herpes virus directly
• Examples: trifluorothymidine (Viroptic®), cidofovir, vidarabine (Vira-A®)
• Cidofovir allows twice-daily dosing—others need 4–5x/day

3. 💊 Oral Antivirals

• Famciclovir is commonly prescribed
• Provides systemic and tear-based antiviral coverage
• Well-tolerated in most cats; dosing still evolving

4. 🌿 Supportive Treatments

• 🧴 Hyaluronate eye drops to improve comfort and tear quality
• 🧃 Fortiflora® probiotics may reduce severity when added to food
• 😺 Stress reduction is key—quiet environments help reduce recurrences

⚠️ Complications from Chronic Herpes Infection

🩻 Eosinophilic Keratitis

Chronic infection can lead to white plaques on the eye. Diagnosis via cytology shows eosinophils. Requires long-term immune suppression (e.g., topical steroids or cyclosporine). 🔬

🧱 Corneal Sequestrum

A section of the cornea may die and turn black—especially in Persians. Treatment may involve surgical grafting. Referral to a veterinary ophthalmologist is often needed. 🏥

🛡️ Can It Be Prevented?

• 💉 Vaccination reduces symptom severity but does NOT prevent infection
• 🧽 Keep food bowls, bedding, and litter clean
• 🐈‍⬛ Reduce stress in multi-cat homes
• 💊 Consider prophylactic famciclovir during known stressors (boarding, moving, etc.)

🙅 Can Humans Get It?

Thankfully, feline herpes is species-specific. It cannot be spread to humans, and human herpes cannot infect cats. 🧍🐱

📱 Ask A Vet App for Support

Recurring feline eye flare-ups? The Ask A Vet app makes managing herpes conjunctivitis easier:

• 📷 Upload eye photos and receive expert input
• 💬 Chat with licensed vets about antiviral and antibiotic options
• 🧾 Track treatment progress and symptom logs
• 📅 Set reminders for meds and recheck exams

🏁 Final Takeaway

Herpes viral conjunctivitis is common, manageable, and usually not dangerous if treated early. With a combination of antiviral therapy, antibiotics, and supportive care, cats can live comfortably—even with this chronic condition. Work closely with your vet, minimize stress, and use the Ask A Vet app to stay on top of flare-ups and care. 🐱👁️❤️