Pinkeye, or infectious bovine keratoconjunctivitis (IBK), can be very problematic in cow herds. It is a highly contagious disease, causing inflammation of the cornea (the clear outer layer) and conjunctiva (the pink membrane lining the eyelids) of the eye. It will also cause ulceration, which looks like a hole or depression in the cornea.
The incidence of pinkeye increases in spring, peaks in the summer and decreases in the fall. Pinkeye results in mild to severe disease, blindness if left untreated and can cause significant reductions in performance and cattle value.
AJ Tarpoff, Kansas State University Extension veterinarian, says weaned calves may lose up to 10% of their body weight as a result of the disease. He explains pinkeye is a multifactorial disease that is often initiated by direct irritation to the cornea followed by bacteria invading the lesion. Moraxella bovis has long been considered the key pathogen in pinkeye cases, however, other bacteria such as Moraxella bovoculi, Mycoplasma bovis and Mycoplasma bovoculi have been implicated as well.
Tarpoff says the factors that can contribute to the disease are:
- UV radiation from the sun.
- Dust.
- Grass awns (scratches on the eye from grazing tall grass).
- Face flies — flies feed on discharge from the eye. They can spread the bacteria rapidly from animal to animal.
- Stress.
- Concurrent disease or viral infection (IBR, BVD).
“These factors can cause physical irritation to the surface of the eye initiating the disease or inhibit the body’s natural defense mechanisms,” Tarpoff explains.
The Signs
Excessive tearing, blinking and squinting are all early signs of pinkeye. The excess tears often drain down the face collecting dirt and grime. This can be seen from a distance. As the disease progresses the eye becomes extremely red and the cornea (clear part of the eye) becomes white and cloudy. The clear cornea can form an ulcer and even rupture in severe cases. Healed lesions on the cornea will appear as a white scar, which may clear over time.
Three Stages of Pinkeye
According to Megan Van Emon, Montana State University Extension beef cattle specialist, there are three stages of pinkeye. The disease may resolve at any of these stages, though without treatment the most severe cases will progress through all three stages.
Stage 1: Cattle have excessive tearing and increased sensitivity to light. They will blink frequently, and there is redness along the eyelids. Cattle will often seek shade, which will decrease their grazing time. Pain associated with pinkeye also decreases their feed intake. Stage 1 will progress to a small ulcer in the center of the cornea, which appears as a small white spot. The cornea develops a slightly cloudy gray appearance due to inflammation. One or both eyes may be affected.
Stage 2: The clinical signs described in Stage 1 continue, but the ulcer spreads across the cornea. As more inflammation occurs, the cornea becomes increasingly cloudy. At this point, some of the dark color of the iris can still be seen. Blood vessels from the outside portion of the cornea begin to grow across the cornea to help with healing. These blood vessels make the cornea appear pink, which is how the disease received its name.
Stage 3: The ulcer covers most of the cornea, and the inflammation continues to spread into the inner parts of the eye. When this occurs, the inside of the eye fills with fibrin, which is a pus-like substance that gives the eye a yellow appearance versus the typical brown appearance.
Treatment Tips
If pinkeye is becoming an issue, a veterinarian has the tools and expertise to help in face of an outbreak. Samples may be sent to the diagnostic lab to determine the best course of treatment.
“The biggest treatment option I recommend is to work with your veterinarian as they are familiar with what is happening in the area as well as what is and is not working,” Tarpoff suggests. “Working with your veterinarian also gives producers a chance to establish a veterinarian-client patient relationship, which is extremely important when treating animals with antibiotics.”
Tarpoff adds, “Injectable long-acting oxytetracycline antibiotics are often used for treatment of pink eye cases with good effect. There are labeled veterinary prescription options as well.”
To help with the healing process, it is recommended that a glued eye patch be applied to the affected eye.
“An eye patch does two things to promote healing,” Tarpoff says. “First, it takes away the irritant of the sun’s UV radiation and wind. Eliminating these irritants will increase cattle comfort during the healing process. Second, the patch can help [with] decreasing the spread of the disease by physically blocking flies from feeding on the tears of the affected eye.”
Guy Sheppard, DVM and retired Texas A&M Veterinary Medical Diagnostic Laboratory veterinary diagnostician, suggests affected animals should be separated from non-infected animals, as flies and other vectors can help spread the infection to other cattle.
“Young animals are most often affected, with dust and shipping causing exacerbation of the condition,” Sheppard says. “Treatment of the condition with antibiotics can be very helpful in the early stages of the condition, but corneal ulcers that progress to complete penetration of the cornea are likely to remain permanently blind in the affected eye.”
The length of recovery time generally comes down to the severity of the infection and individual variability. Tarpoff says if the animal is immunocompromised for any reason, it won’t respond like it should regardless of antibiotic use. If the animal is otherwise healthy, it should respond well to early treatment.
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