Pinkeye is a highly contagious infectious disease that not only affects cattle in Nebraska but worldwide. The incidence and severity of this common disease can vary widely from year to year. Although pinkeye rarely causes the death of affected cattle, it can cause substantial losses to the cattle industry through decreased weight gain, lowered milk production and treatment costs.
Pinkeye is known to occur at all seasons of the year and in all breeds of cattle. Excessive weeping of the affected eye and closure due to pain are the two signs most commonly observed. As the disease progresses, the cornea becomes cloudy or white. An ulcer frequently develops near the center of the cornea. Cattle with pinkeye keep the affected eye or eyes closed because of pain and to avoid bright sunlight. The course of the infection may run for several weeks.
Pinkeye is primarily caused by Moraxella bovis (M. bovis); however, other organisms have been isolated from eyes with infections resembling pinkeye. It remains unclear whether these other organisms are primary pathogens or opportunistic, secondary invaders. Pinkeye is caused by a combination of factors. Other suspected risk factors that contribute to clinical pinkeye are excessive ultraviolet light (sunlight), biological vectors (primarily face flies), plant material and dust.
Efforts to prevent pinkeye are directed at reducing transmission and minimizing irritation. Fly control can minimize both transmission and irritation; however, it is not a guarantee for prevention. Face flies can remain infected with M. bovis up to 3 days following feeding on infected material. Under experimental conditions, disease transmission is uncommon without the presence of face flies and is common with flies present. Fly control does have the added benefit of limiting the fly avoidance behavior that reduces productivity in cows and calves on pasture. The infection can also be spread by direct contact when the eye secretions of an infected animal are rubbed into the eye of an uninfected animal.
While other fly species like stable and house flies can transmit pink eye, face flies are the primary biological vector. Fly control methods should target the region of the face with daily exposures of the control product. Both cows and calves must be treated if control is to be realized. Dust bags, oilers, sprays, or insecticide ear tags are all adequate control options. Be sure to follow label directions for the product used, and rotate the insecticide mode of action during the fly season to prevent resistance.
Reducing dusty conditions and providing protection against sunlight also aids in control. Cattle often have grass or weed seeds in their eyes, and these materials can irritate the eye and contribute to the development of pinkeye.
Cattle with pinkeye can be helped by prompt treatment which usually includes an antibiotic and often includes eyepatches to limit further irritation. Since the cornea heals slowly, any ulceration is likely to require several weeks for complete recovery. Vaccinations for pinkeye have met with variable results.
There are other infections that look like pinkeye so it is recommended that you consult with your veterinarian to assist you in the diagnosis, treatment and control of pinkeye if you suspect it in your herd.
-Ben Beckman is a beef systems Extension Educator serving the counties of Antelope, Cedar, Knox, Madison, and Pierce. He is based out of the Cedar County Extension office in Hartington. You can reach him by phone: (402) 254-6821 or email: ben.beckman@unl.edu.