Pinkeye – more properly known as “infectious keratoconjunctivitis” – is a highly contagious disease affecting the eyes.
It can affect cattle, sheep and even humans, but the organisms that infect livestock are not the same as those that affect people, and humans cannot contract it from animals.
Dr. Charlotte Clifford-Rathert, the state Small Ruminant Extension Specialist for Lincoln University Cooperative Extension and Research, told Ozarks Farm & Neighbor pinkeye in goats and sheep is caused by two primary infective bacteria, Chlamydophila pecorum and Mycoplasma conjunctivae.
“Clinical signs are usually obvious tearing of the eye, cloudiness, redness, squinting and sensitivity to sunlight,” she said. “Severe cases can result in corneal ulcers and blindness. Diagnosis is based on clinical signs, conjunctival scraping and positive culture of the organism from the tears. The disease will usually complete its course in three to four weeks.”
Cattle and small ruminants can be treated with eye medications containing antibiotics like tetracycline, and in some individual cases an injectable tetracycline is warranted. When treating cattle, according to University of Arkansas Extension veterinarian Dr. Jeremy Powell, injectables can be administered under a veterinarian’s care if topical treatments have failed. However, while there are no effective vaccines available for sheep or goats, Powell told OFN there are vaccines for cattle; the veterinarian can recommend which vaccine is the best fit for your situation.
Powell said pinkeye in cattle during the summer months has been blamed historically on an organism called Moraxella bovis.
“Over the last few years we’ve seen another organism associated with pinkeye in cattle called Moraxella bovoculi,” he explained. “It seems as though we don’t see it as often as we see M. bovis, but when we do see it, it seems more aggressive and somewhat more resistant to some of the antibiotics we’ve used to treat pinkeye cases in the past.”
While pinkeye is not normally a life threatening issue, it causes economic detriments in terms of weight gains in cattle.
“Instead of being out and grazing pastures, cattle dealing with pinkeye cases are laying over in the shade because the extra light from the summer sunshine hurts their eye,” Powell said. “If it happens in cows that are nursing calves, their milk production will be affected because of lower grazing intake while they’re affected with pinkeye, so that will affect calf weight gains.”
Pinkeye is contagious and can be spread via direct contact, but the main vector is the face fly, and populations are high this year due to all the early moisture. The face fly feeds off discharge from the eyes of cattle and it uses its spongy mouthparts to feed off the eyelid of an infected cow, and when it moves to the next cow it carries the bacteria with it.
Another predisposing factor this time of year can be tall grass in the pasture.
“With an animal that spends a lot of its time with its head lowered, just grazing through the pasture, seed heads and tall grass can cause mild abrasion to the eye, which causes irritation and makes the eye more susceptible to infection,” Powell said. “Dust can also cause irritation to the eye, and just the extended sunlight, cattle with less pigment around the eye, like white-faced cattle tend to have more issue with pinkeye than some other breeds.”
However, he hastened to add, “you’ll see plenty of cases among cattle that have pigment around the eye as well.”
In addition to antibiotics, fly control and clipping grass shorter, sometimes a veterinarian will prescribe a simple patch over the animal’s eye to protect it from the UV light, as well as from flies and grass seed.


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