What are the Common Causes of Canine Eye Infection?

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  • Written By: Marjorie McAtee
  • Edited By: W. Everett
  • Last Modified Date: 11 August 2019
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Canine eye infection is considered one of the most common eye problems in dogs. Eye infection symptoms in dogs can include redness, discharge, lesions of the cornea, and swelling. Left untreated, canine eye infection can cause vision loss and blindness in dogs. Common causes of canine eye infection can include bacterial, fungal, and viral agents, while parasites and protozoa are also responsible for some dog eye infections. Certain medical conditions may make dogs more vulnerable to eye infections.

Canine conjunctivitis, or dog pink eye, usually occurs as a result of eye infection. Usually conjunctivitis in dogs causes the inner membranes of the eye to become swollen, itchy, and inflamed. Thick eye discharge may be present in more severe cases. Blepharitis, a similar eye condition, causes the outer skin of the eyelid to become swollen and tender.

Bacterial and viral agents are most often responsible for canine eye infection. Injuries to the eye, allergic reactions that cause eye symptoms, and conditions that affect the immune system can increase a dog's risk for eye infection. Bacteria spread by parasites, like ticks, can cause eye symptoms in dogs. These include Borrelia burgdorferi, the bacterium responsible for Lyme disease, and Rickettsia rickettsii, the bacterium responsible for Rocky Mountain spotted fever. Canine herpesvirus can cause eye symptoms in dogs, as can the virus responsible for distemper. If canine eye infection is a symptom of a more serious illness, additional symptoms are usually present.


Fungal infections such as blastomycosis can cause eye symptoms in dogs. Single-celled organisms known as protozoa can cause serious infections, such as toxoplasmosis, that affect the eyes, as well as other body systems. Parasites such as heart worms and eye worms can actually infest the eye. Ocular surgery is generally required to remove eye parasites and treat the infestation.

Any medical condition that causes inflammation of the eye, or damage to the eye or surrounding structures, can make canine eye infection more likely. Dogs suffering eye symptoms due to allergies may experience recurrent eye infections. Flea bites, cuts, and scratches on or near the eye, or burns to the eye can make it easier for bacteria, viruses or other pathogens to penetrate the dog's immune defenses and cause eye infection.

Dogs with suppressed immune systems may be more vulnerable to eye infections. Conditions such as diabetes, lupus, hypothyroidism, and hyperadrenocorticism can affect the immune response, making infections of all types more likely. These diseases can also cause eye complications, making the eyes more vulnerable to infection.


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Post 3

@ankara-- Absolutely.

My puppy has an eye infection right now because of a scratch. He hasn't learned how to be around our cat yet and he got his cornea scratched playing with her. The doctor said the scratch is not very bad but some bacteria got in and caused an infection. We're applying some ointment right now. Hopefully this clears up soon, he's too young to be dealing with eye problems.

Post 2

Can a scratch on the eye cause an eye infection?

Post 1

My dog had a fungal eye infection. I know that there are a lot of different kind of canine eye problems but I had no idea that a fungal infection is possible in the eye!

His eyes were red, swollen and had discharge for weeks. His vet gave eye drops first which didn't help at all. When we went back to the vet, they took some of the discharge from his eye and sent it to the lab. That's how we found out that it's a fungal infection.

He used anti-fungal medication for a week and continued with the eye drops. His symptoms went away soon after.

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