I had a rancher stop in my office the other day, and he said some of his cows were getting “Pinkeye”. Infectious Bovine Keratoconjunctivitis (IBK) or “Pinkeye” is a costly and exasperating disease for the cattle producer and industry.

A field trial published in 2009 found an average weaning weight difference of 18 pounds less (range 9-27 lbs.) in calves that experienced pinkeye versus those that did not. Calves with corneal scars are often discounted at sale, further increasing the economic cost to producers. 

A recent study found continued impact in the beef industry from pinkeye on production traits. Yearlings that had pinkeye as young calves pre-weaning had less 12th rib fat depth, ribeye area, and body weight than did yearlings without evidence of pinkeye. Despite the well-known economic impact of disease, adequate and timely treatment of cases is challenging because cattle are grazed far away from facilities during peak occurrence in summer months. 

Preventing the disease has proven difficult because so many factors contribute to the development of pinkeye including environment, management, season of the year, concurrent diseases, and the animal’s genetic makeup and immune system. The bacterium Moraxella bovis is considered the primary cause of pinkeye but a newly isolated strain “Moraxella bovoculi” is now believed to play an important role. Vaccines, whether commercial or homemade, have not been found consistently effective in clinical trials. Once pinkeye begins in a herd, it is highly contagious and can spread rapidly. Careful attention to control of contributing factors, especially fly control, and prompt, effective treatment of cases is necessary to reduce the spread and limit the damaging effects of the disease.

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.

Prevention of pinkeye is difficult because it is a complicated, multifaceted disease. The best plan is to reduce or remove as many risk factors as possible that can result in damage to the corneal surface. Any damage will allow the bacteria to cling to the corneal surface and grow. Many different combinations of contributing factors such as ultraviolet rays from the sun, face flies, excessive eye irritation, nutritional deficiencies, and stress may work together within a herd at one time. Prevention is based on maximizing herd immune status, controlling face flies, minimizing exposure to the bacteria, and maintaining as irritant-free environment as possible.

Steps to Preparing for Pinkeye Season:

• Maximize Herd Immune Status – An overall good level of nutrition, adequate vitamin and trace mineral intake, a comprehensive vaccination program including the respiratory viral diseases IBR, BVD, PI3 and BRSV, parasite control, and basic biosecurity practices are all exceptionally important in improving the cow’s or calf’s ability to fight off any disease process (not just pinkeye). 

There is no scientific evidence to support feeding excessive levels of any vitamin or mineral, including Vitamin A, will prevent diseases of the eye. However, if trace mineral levels (especially selenium and copper) are very low in an animal, immune function is severely impaired. Biosecurity measures such as quarantine of new arrivals to the farm (including show animals) for at least 2 weeks before commingling with the herd are important in case any of these animals are carrying the disease.

• Control Face Flies – Face flies can play an important role in the spread of pinkeye. Their abrasive blotting mouthparts irritate the animal’s eyes, stimulating tears and mucus that feed the insects. Bacteria in the secretions of infected cattle can survive on or in face flies for 2 to 3 days and infect other animals when the flies feed again. Face fly control is challenging. The flies spend only a few minutes at a time on or around the head, which is a difficult area to protect. Application methods that regularly place insecticide around the face and eyes provide the best means of protecting cattle. Insecticide impregnated ear tags or force used dust bags provide the most consistent reductions in fly numbers. Insecticide feed-throughs, such as IGRs (insect growth regulators), can reduce the number of fly maggots developing in manure of animals that receive a sufficient daily dose. However, supplemental adult control is often needed to control flies moving in from nearby herds.

• Minimize exposure to M. bovis and M. bovoculi – Early detection of animals with the first clinical signs (tearing, squinting, and blinking) and then prompt, effective treatment are essential to reducing spread to herd mates and limiting damage to the eye. Long-acting antibiotics such as long-acting tetracycline (LA-200) or the prescription antibiotic tulathromycin (Draxxin) are labeled for treatment of pinkeye. A veterinarian may prescribe the antibiotics florfenicol (Nuflor), ceftiofur (Excede), or others to be used in an off-label manner for treatment as well. Injectable antibiotics are generally the best option because of their long duration of activity and effectiveness in eliminating bacteria. Topical sprays only remain in the eye a few minutes before tears wash them away so application is generally required 3-4 times daily to be effective. When severe ulceration exists, the eyeball may need extra protection with either a patch or the eyelids may need to be sutured (stitched) together. Remember, preventing spread by treating affected animals is the single most important factor in controlling a disease outbreak. Active cases of pinkeye with excessive tearing attract flies that widely spread the bacteria. Topical application of a fly repellant to the face will also help reduce spread.

• Does vaccination work? – In clinical trials, approximately half reported significant protection from commercial pinkeye vaccines. A recently published study in August of 2017 involving 214 spring-born calves, half of them vaccinated according to label directions with a commercial pinkeye vaccine and half left unvaccinated, had dismal results. At the end of the trial, pinkeye had been detected in 65 (59.1%) vaccinated calves and 62 (59.6%) unvaccinated calves during the study period and there was no difference in weaning weights for vaccinated versus unvaccinated calves. Clearly, vaccination is not the solution to all pinkeye problems although it may reduce the number of calves affected and lessen the severity of clinical signs. Autogenous vaccines do lose effectiveness within one to two years as the bacteria mutate and a new batch of vaccine needs to be made from new cultures.

In summary, pinkeye is one of the most common diseases of cattle and is of major economic importance to cattle producers. Although much research is ongoing to understand this complex disease, the keys to prevention and control of pinkeye still rely on the basics of maximizing the herd’s immune status, minimizing exposure to Moraxella bacteria, face fly control and maintaining as irritant-free environment as possible. Treatment decisions are influenced by numerous factors such as effectiveness and cost of the antibiotic, labor availability, withholding times, facilities, and availability of a veterinary prescription. Vaccines are not consistently effective in disease prevention and cannot be completely relied upon to prevent pinkeye. The best strategy of treatment, prevention and control of pinkeye for a particular herd is best accomplished with the help of the local veterinarian.

Sources: Watch out for cases of summer pinkeye, University of Nebraska-Lincoln Extension

Preparing for Pinkeye, Michelle Arnold, DVM, University of Kentucky Extension