Pinkeye in Cattle

Pinkeye is a highly contagious infectious disease.
Pinkeye is a highly contagious infectious disease.

by Richard F. Randle, DVM, UNL Extension Beef Cattle Veterinarian

Pinkeye is a highly contagious infectious disease affecting the eyes of cattle. This common disease can vary in its severity 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 but is most common during the summer months. Pinkeye can occur in one or both eyes. 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. The course of the infection may run for 4 to 8 weeks, or even longer.

Pinkeye is primarily caused by Moraxella bovis (M. bovis) however multiple organisms such as Mycoplasma bovoculi and IBR virus have been found in eye infections resembling pinkeye. Other factors instrumental in causing eye irritation, thereby allowing for invasion of M. bovis and subsequent disease, are excessive ultraviolet light (sunlight), the face fly, plant material, and dust. Pinkeye is caused by a combination of factors. Dry, dusty environmental conditions or wet, warm environmental conditions play a role. Taller grass and seedheads can damage the eyes. The wet, warm conditions also lead to heavier fly populations that irritate the eyes and spread the organisms.

The face fly has been associated with an increased incidence of pinkeye in recent years. Research at the University of Nebraska's West Central Research and Extension Center has demonstrated that face fly feeding produces mechanical injury to the conjunctiva and spreads IBR virus and Moraxella bovis from animal to animal as the fly feeds on eye and nose secretions of cattle. Flies not only serve as irritants as they feed on secretions from the eye they also serve as a means of transmitting M. bovis from infected to non-infected animals. 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.

Vitamin A deficiency and inadequate protein intake may be other factors that possibly contribute to lessened resistance to eye infections. Vitamin A deficiency results in excessive watering of the eye, night blindness, and may cause cloudiness of the cornea in severe cases, giving the eyeball a dry, lusterless appearance.

A good control program should incorporate procedures to reduce initial eye irritation. An intensive fly control program is essential to limit the spread of pinkeye in a herd of cattle. Cattle often have grass or weed seeds in their eyes, and these materials no doubt irritate the eye and contribute to the development of pinkeye. Cattle with pinkeye can be helped by prompt treatment. There are other infections that look like pinkeye so it is recommended that you consult with your veterinarian to assist you in the diagnosis and treatment of pinkeye.