Bacterial Conjunctivitis in Cats 🐱💉

By Dr Duncan Houston, BVSc

Bacterial conjunctivitis is a common but treatable eye condition in cats. While feline herpes virus is a frequent cause of conjunctival inflammation, secondary bacterial infections are often involved—especially from Chlamydia felis and Mycoplasma spp.. Learn to spot the signs early and treat effectively with this 2025 feline eye health guide from Dr Duncan Houston. 👁️🐾

🔬 What Is Conjunctivitis?

Conjunctivitis is inflammation of the conjunctiva—the thin tissue covering the white part of the eye and inside of the eyelids. In cats, this often presents with redness, tearing, and discharge. It can be caused by viral, bacterial, allergic, or traumatic factors. 🧪

🦠 Primary Bacterial Causes

While feline herpes virus is the most common root cause, bacterial agents often contribute or act independently:

1. Chlamydia felis

• Causes red, swollen eyes and watery or mucous discharge
• Highly contagious, especially in multi-cat households
• Treatable with antibiotics like doxycycline
• Vaccination exists but is optional based on risk 🧫

2. Mycoplasma spp.

• Part of the eye’s normal flora—overgrowth leads to infection
• Causes similar signs as Chlamydia
• Cannot be fully eliminated—treatment focuses on control
• No vaccine exists 🦠

📋 Clinical Signs of Conjunctivitis

Look for the following symptoms, which may affect one or both eyes:

• 🔴 Red eyes
• 💧 Tearing or watery discharge
• 🧼 Crusting around eyelids
• 🙈 Squinting or frequent blinking
• 🧲 Eyelid swelling
• 🤕 Scratching at the eyes or face
• 📉 Reduced tolerance to light

🔍 Diagnosing the Infection

Your veterinarian will begin with a physical eye exam to rule out trauma or ulcers. Diagnostic tests include:

• 🔬 Cytology: Microscopic exam of conjunctival scrapings to check for bacteria and inflammation
• 🧬 PCR testing: Identifies specific organisms like Chlamydia or Mycoplasma; usually sent to an external lab

💊 Treatment Options

The primary treatment is antibiotics. The most effective drug for both Chlamydia and Mycoplasma is:

• 💊 Doxycycline (oral or topical)
• 🧼 Eye ointments or drops may be prescribed to reduce inflammation
• 😷 Treat all cats in the household if exposure is likely

📈 Prognosis

With proper antibiotic therapy, most cats recover fully. However, if symptoms linger, your vet may investigate other causes or recommend additional testing. Chronic cases may indicate viral reactivation or underlying systemic illness. 🩺

🛡️ Prevention Tips

• 💉 Vaccinate for Chlamydia felis if your cat lives in a multi-cat household or cattery
• 🧍‍♂️ Isolate symptomatic cats to prevent spread
• 🧼 Wash bedding and sanitize bowls frequently
• 🐾 Monitor new cats for signs before introducing them to others

🧠 Fast Facts

• 👁️ Conjunctivitis is the most common feline eye condition
• 🧬 Mycoplasma is always present; overgrowth is the problem
• 💊 Antibiotics are usually highly effective
• 📸 Early vet evaluation prevents complications like corneal ulcers

📱 Ask A Vet App Support

Not sure if your cat’s red eye is an emergency? Use the Ask A Vet app to:

• 📷 Upload pictures of your cat’s eyes for vet evaluation
• 🩺 Get advice on whether to isolate your cat
• 💬 Chat live with licensed vets about treatment plans
• 📤 Track eye symptom improvement over time

🏁 Final Takeaway

Bacterial conjunctivitis in cats is uncomfortable but very treatable. Recognizing early signs—like red eyes, discharge, or squinting—and starting prompt veterinary care ensures a smooth recovery. With good hygiene and preventive steps, your cat’s eyes can stay bright, clear, and healthy. 🐱👁️❤️