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 an irritant-free environment as possible.
Pinkeye, more clinically known as Infectious Bovine Keratoconjunctivitis (IBK) is a costly and exasperating disease for producers. Michelle Arnold, DVM and Ruminant Extension Veterinarian at the University of Kentucky noted 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. 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 yearlings without evidence of pinkeye.
Despite the well-known economic impact of the disease, adequate and timely treatment of cases is challenging. Cattle are grazed far away from facilities during peak summer months. Preventing the disease is tough because so many factors contribute to the development of pinkeye. The best plan of defense includes reducing or removing as many risk factors as possible.
Maximize Herd Immune Status
An overall sound 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 prevents diseases of the eye.
However, if trace mineral levels (especially selenium and copper) are deficient in an animal, immune function is severely impaired. In these instances, an injectable mineral (Multimin®) may be necessary to bring these minerals back within a reasonable range so vaccines and antibiotics can work.
Control Face Flies
Face flies can play an essential 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 flies may move as far as four miles during their life so they can easily transfer pinkeye from herd-to-herd and farm-to-farm.
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 offer 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 the manure of animals that receive a sufficient daily dose. However, supplemental adult control is often needed to control flies moving in from nearby herds.
Maintain an irritant-free environment
Any irritation to the eye allows Moraxella organisms to invade and cause pinkeye. Prevent eye irritation with good face fly control, mow tall grass with seed heads, provide shade and ample clean, cool water, and reduce sources of stress (such as overcrowding). Provide shade to protect from the harmful UV rays of the sun. Cool, clean drinking water is critical because the intake is greater with clean water and this helps provide plenty of fluid to the corneal surface, especially crucial in dry, dusty, and/or windy conditions. Tears are essential in eye defense mechanisms as tears wash away pathogens and tear proteins are an integral component of protection. Do not forget to check and clean automatic waterers regularly.
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 is 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. Your vet 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 productive. 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 crucial 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?
Immune responses to pili have been shown to be protective in some studies where animals are vaccinated with pili of a particular type and then challenged with a similar strain. A high degree of diversity among pilin genes is likely responsible for why some herds might see a benefit from vaccination while other herds do not; if the vaccine strain stimulates immunity to a pilus type that is also present in the herd, there should be good protection.
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.
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.
In summary, 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 an irritant-free environment as possible. The best strategy of treatment for a particular herd is best accomplished with the help of the local veterinarian.