New research brings fresh hope for pinkeye prevention

Infectious bovine keratoconjunctivitis, better known as pinkeye, remains one of the most economically important diseases affecting beef and dairy cattle. Every summer, producers battle lost performance, treatment costs and frustration as cases spread through calves and cows. While vaccines, antibiotics and fly control remain the cornerstones of prevention, new research suggests the future of pinkeye management may involve strengthening the eye’s own natural defenses.

Recent research has highlighted the importance of the bovine ocular microbiome — the community of beneficial bacteria naturally living on a healthy eye. Maintaining this healthy bacterial population may become an important tool in preventing pinkeye while reducing reliance on antibiotics in the future.

Pinkeye is far more than an eye infection. It causes pain, tearing, squinting, corneal ulcers, impaired vision and, occasionally, permanent blindness. Cattle eat less, calves gain weight more slowly and dairy cows often experience reduced milk production because of discomfort. Studies have shown calves affected with pinkeye wean nearly 20 pounds lighter than unaffected herdmates. Industry losses exceed $150 million annually when treatment costs, labor, reduced performance and culling are considered.

For years, Moraxella bovis was considered the primary cause of pinkeye. Today, we recognize the disease is much more complex. Pinkeye develops through the interaction of disease-causing bacteria, environmental stressors and the animal’s immune system. Face flies, ultraviolet light, dust, pollen, tall grass seed heads and eye trauma all create opportunities for bacteria such as M. bovis, M. bovoculi and Mycoplasma species to infect the cornea. Recent research has also shown healthy eyes contain beneficial bacteria that may naturally suppress these pathogens. When that normal microbial balance is disrupted, disease-causing bacteria gain the advantage.

Although this research is exciting, the most effective prevention today still relies on excellent management.

Reducing eye irritation is the first step. Clip mature grass seed heads before they become abrasive, control weeds around fence lines and water tanks, minimize dust in dry lots and feed alleys, provide adequate shade to reduce ultraviolet exposure and maintain balanced nutrition, including adequate Vitamin A. Avoid overcrowding whenever possible, as increased animal contact accelerates disease transmission.

The second — and arguably most important — component is an aggressive, integrated fly control program.

Face flies are the primary mechanical vector of pinkeye because they feed on eye secretions and readily transfer bacteria between cattle. They are also difficult to control because they spend only 10%-20% of their time on the animal, resting instead on fences, buildings, vegetation, and manure. That is why no single fly product provides adequate control.

One of the most common mistakes we see in practice is waiting until the first case of pinkeye appears before beginning fly control. By then, face fly populations have already exploded, and bacteria are moving rapidly through the herd. Fly control should begin before fly numbers increase in late spring and continue throughout the fly season.

Feed-through insect growth regulators, such as Clarifly (diflubenzuron) or Altosid (methoprene), provide an excellent foundation by preventing fly larvae from developing in manure. These products should be started approximately 30 days before fly emergence and fed consistently throughout the season.

On-animal protection should include products such as CyLence Pour-On or Permectrin CDS Pour-On, applied according to label directions during periods of heavy fly pressure. For pasture operations where gathering cattle frequently is difficult, VetGun AiM-L VetCaps containing permethrin offer another practical treatment option.

Insecticide ear tags remain one of the most economical season-long control tools. Products such as Corathon, PYthon Magnum, XP 820 and several Y-Tex tags provide extended control when applied before fly numbers peak. Most mature cattle require two ear tags per animal for optimal face fly control, according to label directions. Rotating insecticide classes each year is essential to slow resistance, particularly as pyrethroid resistance becomes more common.

Dust bags and back rubbers also work well when cattle are required to pass through them to reach water or mineral feeders.

Because face flies spend much of their day away from cattle, premise management is equally important. Residual insecticides such as Permectrin II, Tempo SC Ultra or Elector PSP can be applied to barn walls, fence lines, calf housing, loafing sheds and holding pens according to label directions. Managing manure well, reducing spilled feed and improving drainage further reduces fly breeding sites.

Don’t overlook the bulls. Studies consistently show bulls carry significantly higher face fly populations than cows, making them an important source for maintaining fly pressure throughout the breeding season. Treating bulls aggressively often improves whole-herd fly control.

Early recognition and treatment remains critical. Prompt veterinary treatment not only improves healing but may reduce bacterial spread to herdmates. Severely affected animals should be monitored closely and, when practical, temporarily separated until healing begins.

Perhaps the most exciting development in pinkeye research is the growing understanding of the bovine ocular microbiome. Much like the rumen microbiome has become central to nutrition and animal health, researchers now recognize that a healthy eye is home to its own community of beneficial bacteria. These naturally occurring microbes appear to play an important role in maintaining eye health by competing with disease-causing bacteria, supporting the local immune system and maintaining the eye’s protective surface. When that balance is disrupted by ultraviolet light, dust, flies, eye irritation, stress or injury, harmful bacteria gain the opportunity to establish infection.

Researchers are now exploring ways to use this knowledge to prevent pinkeye before it develops. Laboratory studies have already identified several naturally occurring bacteria from healthy bovine eyes that inhibit the growth of M. bovis and M. bovoculi. Other promising areas of research include ocular probiotics that restore beneficial bacteria, bacteriophage therapy that selectively targets harmful bacteria while preserving beneficial microbes, targeted essential oil formulations and nutritional strategies that support both gut and eye health through the emerging gut-eye axis.

These microbiome-based approaches represent a fundamental shift in disease prevention. Rather than simply treating infection after it occurs, future therapies may enhance the eye’s natural defenses and make cattle more resistant to disease. As concerns about antimicrobial resistance continue to grow and current vaccines provide variable protection, these therapies could become an important addition to comprehensive pinkeye prevention programs.

While these technologies are still under development, producers can make a tremendous impact today by focusing on proven management practices. Minimize eye irritation, provide balanced nutrition, implement a comprehensive season-long fly control program before fly numbers build and work with your veterinarian to identify and treat clinical cases early.

The science behind pinkeye prevention is evolving rapidly, but one principle remains unchanged: Healthy eyes start with proactive management. Until the next generation of microbiome-based tools becomes available, integrated fly control, sound pasture and facility management and early intervention remain the best defenses against one of the cattle industry’s costliest diseases.

Portia Seckerson is the owner of Nortnern Valley Livestock Services in Plainview, MN. Their office of six veterinarians cover Minnesota and Wisconsin. She can be reached at pseckerson@nvls.vet