Bovine Pinkeye (Infectious Bovine Keratoconjunctivitis) in Cows

Bovine pinkeye is the common name for infectious bovine keratoconjunctivitis (IBK), a contagious and painful disease of the eye in cattle. It affects the conjunctiva and the cornea, and the hallmark early change is often a central corneal ulcer. Cattle with pinkeye may tear excessively, squint, avoid bright light, and develop a cloudy or white-looking eye.

IBK matters because it is more than a cosmetic problem. Affected cattle can have significant pain, reduced grazing time, lower weight gain, and temporary or permanent vision loss. Calves are often affected more commonly than adults, especially during fly season, but cattle of any age can develop disease.

Most cases improve with timely veterinary care, but the course can vary. Mild cases may heal with limited scarring, while more severe cases can progress to deep ulcers, corneal rupture, or blindness in the affected eye. Because outbreaks often involve both infection and environmental irritation, treatment and prevention usually need a herd-level plan as well as care for the individual cow.

IBK is usually a multifactorial disease, which means infection and eye irritation work together. Moraxella bovis is the classic primary bacterial cause. Other organisms, including Moraxella bovoculi and Mycoplasma species, may be involved in some herds, but their exact role can vary. This is one reason outbreaks can behave differently from farm to farm.

The bacteria spread most easily when the eye surface is already irritated. Common risk factors include face flies, dust, wind, pollen, tall grass or seedheads, and ultraviolet sunlight. Face flies are especially important because they can move between animals and mechanically spread organisms while also irritating the eye.

Some cattle are more susceptible than others. Calves often have higher disease rates than adults. Cattle with less pigment around the eyelids may be more sensitive to sunlight, and nutritional or management stress can make outbreaks harder to control. In practice, your vet will usually look at both the infected animal and the herd environment when building a treatment and prevention plan.

Your vet usually starts with a physical exam and close eye exam. Many cases can be strongly suspected based on the history, season, herd pattern, and classic findings such as tearing, blepharospasm, conjunctivitis, and a central corneal ulcer. The depth of the ulcer and whether the eye is at risk of rupture help guide urgency and treatment choices.

In some cases, your vet may collect samples from the eye for culture, cytology, or PCR testing. These tests can help identify organisms associated with the outbreak, especially if cases are severe, recurrent, or not responding as expected. Testing can also be useful when a herd-level prevention plan is needed.

Diagnosis also means ruling out look-alike problems. Eye trauma, foreign material, infectious bovine rhinotracheitis-related eye disease, cancer eye, and other causes of corneal ulceration or opacity can resemble pinkeye. Because treatment choices and withdrawal times matter in food animals, it is important to have your vet confirm the likely cause before starting or changing medications.

Prevention works best when it targets both infection pressure and eye irritation. A practical plan usually includes face fly control, reducing dust, clipping tall seedheads, removing sharp pasture hazards, and providing shade when possible. These steps help protect the cornea so bacteria have fewer chances to take hold.

Check cattle regularly during high-risk months, especially calves and animals with pale eyelids or a history of pinkeye. Early detection matters. Promptly identifying and treating affected cattle can reduce pain and may decrease spread within the herd. When practical, moving affected animals to a cleaner, lower-irritation area can help.

Vaccination may be part of prevention in some herds, but results are variable and should be discussed with your vet well before fly season. Herd history, local organism patterns, timing, and product choice all matter. Good overall herd health, including sound nutrition and mineral balance, also supports eye health and disease resistance.

Because pinkeye outbreaks are often driven by several factors at once, there is rarely one single fix. The most effective prevention plans combine environmental management, fly control, early case recognition, and a herd-specific protocol developed with your vet.