How to recognize and treat pink eye in horses

Disclaimer: This article, its content, and its related references do not constitute veterinary advice and should not be considered a substitute for veterinary care. If your pet is showing any symptoms that could indicate a medical emergency, please seek immediate emergency care.

Pink eye, or conjunctivitis, is a common condition in horses that affects the conjunctiva, or mucous membrane, lining the inside of the eyelids and the whites of the eyes (sclera). Symptoms include reddened sclera and tissue around the eyes, abnormal eye discharge, and eye discomfort that causes the affected horse to rub the eye or blink repeatedly. It’s important for horse owners to be able to recognize signs of conjunctivitis in order to get prompt veterinary attention. If you have a horse, read on to learn:

• What pink eye infections look like in horses
• How horses get pink eye
• How pink eye in horses is diagnosed and treated
• If conjunctivitis is an emergency in horses

Infectious conjunctivitis can be caused by viral, fungal, parasitic, or bacterial infections that affect the conjunctiva itself (primary conjunctivitis) or as a result of other ocular or systemic disease (secondary conjunctivitis). Noninfectious conjunctivitis can be a result of trauma, allergies, or irritants (dust, pollen) in the eyes or tear ducts.

Treatment options vary depending on the underlying cause and may include antibiotics, antifungals, anti-inflammatory medications, allergy treatment, treatment of infectious disease, and using an eye mask. Signs of pink eye warrant prompt veterinary care to prevent more damage to the eyes and provide symptomatic relief.

Pink eye, or conjunctivitis, is a common eye disease in horses that describes inflammation of the mucous membrane (the conjunctiva) that lines the inside of the eyelids and the whites of the eyes. Conjunctivitis causes redness in the tissues around the eyes. The whites of the horse’s eyes may or may not be reddened as well.

Equine conjunctivitis can be caused by various eye or systemic conditions and diseases. An affected horse may have conjunctivitis in one or both eyes and additional symptoms depending on the underlying cause. Conjunctivitis can be primary or secondary, meaning the issue can be in the conjunctiva itself or secondary to another ocular or systemic disease.

Common signs of conjunctivitis in horses include:

• Pink or reddened eyes or tissue around the eyes
• Abnormal eye discharge
• Eye irritation or pain
• Squinting or blinking excessively
• Swollen eyelids or tissue around the eyes

Occasional clear eye discharge is normal in horses. More clear discharge or tearing than normal can indicate an issue with the eye. Abnormal eye discharge can vary in color and consistency.

Other symptoms associated with equine conjunctivitis

Depending on the underlying condition causing the eye infection, a horse may have additional symptoms. These symptoms may include:

• Cloudy eyes
• Coughing or sneezing
• Nasal discharge
• Itchiness
• Lethargy
• Loss of or decrease in appetite
• Fever

Other signs of illness can vary depending on what’s causing the infection.

There are multiple reasons why a horse may develop pink eye. Different causes can range in severity and will have different prognoses and treatment methods. “Many cases of pink eye infections in horses result from infectious causes, accumulation of foreign material in the eye, or from irritation to the eyes from flies,” states Dr. Jamie Lecky, a veterinarian on the Vetster platform.

Exposure to irritants

Foreign objects and insects can irritate the eyes, causing a horse to rub their eyes. Common environmental irritants include:

• Flies and other insects
• Dirt, dust, and pollen
• Pieces of hay or grass
• Grass seeds
• Airborne chemicals

Some irritants, like flies, can also cause injury to the eye, increasing the risk of infection. Allergies to environmental irritants can cause reddened eyes (allergic conjunctivitis) as well as respiratory symptoms, such as wheezing and coughing.

Eye injuries

A horse’s eyes are prone to injury from foreign material, which can cause corneal scratches or ulcers. Scratches to the eye from insect bites, pieces of hay, grass seeds, and other foreign items can increase the risk of conjunctivitis in horses. Foreign bodies can also get stuck in the eye, causing damage and allowing infectious agents to enter and cause inflammation and infection.

Bacterial, viral, or fungal infections

Contagious diseases that affect the entire body or the eye directly can lead to pink eye. These diseases include:

• Equine herpesvirus (rhinopneumonitis)
• West Nile virus
• Equine influenza
• Equine viral arteritis
• Potomac horse fever
• Fungal infection
• Parasitic infection

A horse that has a disease affecting their entire body is likely to have additional signs of illness.

Other eye conditions

Various other eye diseases can increase the risk of infection in horses, such as:

• Dry eye
• Inflammation of the tear duct or third eyelid
• Moon blindness (equine recurrent uveitis)
• Eyelid or eyelash disorders
• Eye cancer or tumors

Since many eye issues share common symptoms with conjunctivitis, it’s important to get an accurate diagnosis from a veterinarian to determine what’s them.

A veterinarian will use diagnostic testing to rule out common causes of reddened eyes to reach a definitive diagnosis. Testing may include:

• Thorough physical and eye examination
• Fluorescein eye stain to look for corneal ulcers and scratches
• Schirmer tear test to measure tear production
• Bloodwork, including testing for infectious diseases
• Eye pressure test (tonometry)
• Bacterial or fungal culture
• Looking at swabs or tissue samples under a microscope (cytology)
• Biopsy

Most cases of conjunctivitis in horses are caused by damage or irritation to the eyes from flies and other irritants. However, testing for infectious disease is an important part of the diagnostic process to prevent the potential spread of infection to other horses and animals. An accurate diagnosis from a veterinarian is needed to determine an effective treatment plan.

Once a veterinarian has identified the underlying condition causing a horse’s eye infection, a treatment plan can be made. Potential treatment options for pink eye in horses include:

• Flushing the eye or removing any foreign material
• Topical antibiotics, antifungals, or anti-inflammatories
• Oral antibiotic, antiviral, anti-inflammatory, or pain medication
• Use of a fly mask
• Allergy treatment
• Treatment of any infectious disease
• An insect control plan
• Surgery, in rare cases

Most cases of equine conjunctivitis require medical attention, so prompt veterinary care is recommended any time a horse has eye issues. Diagnostic tests with a vet also help rule out contagious diseases that can put other horses or animals at risk. Prompt treatment prevents the condition from getting worse and causing permanent damage to the eye or even blindness.

It’s important to talk to a veterinarian any time you notice:

• Changes in the eye, eyelids, or surrounding area (swelling, color changes, etc.)
• Abnormal eye discharge
• Foreign material in the eye
• Repeated rubbing of the eye
• Holding the eye closed or repeatedly blinking
• Other signs of illness

Prompt veterinary care is warranted if signs of conjunctivitis are observed in a horse. Do not attempt to diagnose or treat your horse’s eye issue without help from a veterinarian. Misdiagnosis is likely without a vet’s help, and ineffective or inappropriate treatment can lead to permanent eye damage, a worsening infection, or, in severe cases, blindness.

If you would like guidance on how to check your horse’s eye health for signs of irritation, online veterinary professionals are available to help in virtual vet appointments through Vetster’s online platform.

Is eye infection or pink eye an emergency in horses?

Signs of an eye infection or conjunctivitis can indicate an emergency in horses. However, it’s impossible to know how severe an infection is or what’s causing it simply by looking at the eye. Diagnostics and an ocular exam with a veterinarian are necessary to determine how severe the condition is and to establish effective treatment.

How do you treat pink eye in horses?

Treatment for pink eye in horses varies depending on the underlying cause. Potential treatment options include oral or topical antibiotics, antifungals, anti-inflammatories, or pain relief; fly masks; allergy treatment; and addressing any other underlying health issues that may be causing the eye symptoms.

Are eye infections in horses contagious?

Some eye infections or systemic diseases that cause ocular symptoms can be contagious between horses.

Will conjunctivitis in horses go away on its own?

Medical care is necessary for the majority of cases of conjunctivitis in horses to treat the infectious agent and provide supportive care to help the eyes heal. Some cases of conjunctivitis can resolve on their own if caused by the horse being temporarily exposed to an irritant or allergen.