Pinkeye should be a solved disease. We have spent decades refining vaccines, antibiotics and fly control programs for infectious bovine keratoconjunctivitis (IBK), yet the disease continues to challenge cattle operations across North America. The U.S. cattle industry loses more than $100 million annually through reduced weight gain, treatment costs and labor, according to the U.S. Department of Agriculture’s Agricultural Research Service.
The disease has taken on added significance with the spread of New World screwworm. Because female screwworm flies lay eggs in open wounds and around mucous membranes, untreated corneal ulcers and severe ocular lesions caused by pinkeye could provide sites for infestation should the parasite become established in the United States.
The lack of progress is not due to a lack of research. In a 2026 study, North Dakota State University researchers observed that “despite widespread use of antimicrobials and vaccines, the incidence of IBK continues to increase in North American beef cow-calf operations.”
Rather than asking how to better control Moraxella bovis, scientists are increasingly asking a different question: Have we been thinking about pinkeye too narrowly?
Looking Beyond a Single Pathogen
Moraxella bovis remains the only organism for which there is clear experimental evidence of causation, although researchers continue to investigate the roles of other bacteria, including Moraxella bovoculi and Mycoplasma bovoculi, in disease development. Increasingly, however, evidence suggests that bacteria alone do not fully explain why IBK develops.
Today, IBK is viewed less as the result of a single pathogen and more as the product of interactions among bacteria, host immunity and environmental risk factors. Ultraviolet radiation, dust, tall grasses, face flies and other sources of ocular irritation can damage the cornea, creating opportunities for bacterial invasion. At the same time, scientists continue investigating how differences among bacterial strains and the eye’s normal microbial community influence whether disease develops.
The role of Moraxella bovoculi illustrates this complexity. Since its discovery in 2007, the bacterium has frequently been isolated from cattle with pinkeye, but is also commonly detected in healthy eyes. Whether certain strains contribute directly to disease or simply exploit damaged tissue remains an active area of investigation.
That shift in thinking has reshaped IBK research over the past two years in several important ways:
- IBK is increasingly recognized as a multifactorial disease, influenced by bacterial pathogens, host immunity, ultraviolet light, face flies and environmental stressors.
- The ocular microbiome may influence disease susceptibility, with researchers identifying naturally occurring bacteria capable of suppressing Moraxella growth.
- Moraxella bovoculi remains an important but poorly understood player, suggesting the disease cannot be explained by a single pathogen alone.
- Vaccine research is moving beyond traditional approaches, with scientists identifying new bacterial capsule structures that could improve future vaccine design.
The Microbes We Weren’t Looking For
Perhaps the most intriguing development in recent IBK research has little to do with Moraxella itself.
Instead of focusing solely on disease-causing bacteria, scientists at North Dakota State University turned their attention to the eye’s entire microbial community. As the researchers explained, they wanted to better understand “the interplay between pathogenic and beneficial bacteria” within the bovine eye.
The study analyzed 143 ocular swabs collected from 102 cattle with IBK and 41 clinically healthy cattle, identifying 351 bacterial isolates representing 61 bacterial genera. Shotgun metagenomic sequencing revealed significant differences in microbial composition between healthy and diseased eyes, suggesting the microbial community itself may influence disease susceptibility.
Researchers also identified 17 bacterial isolates capable of inhibiting the growth of M. bovis or M. bovoculi during laboratory testing. Eight bacterial species were significantly more abundant in healthy eyes, raising the possibility that naturally occurring microbes may help resist colonization by IBK-associated pathogens.
The findings represent a notable departure from decades of pinkeye research. Rather than asking only how to eliminate Moraxella, scientists are beginning to investigate whether maintaining or enhancing beneficial bacteria could someday become part of IBK prevention.
New Targets for Better Vaccines
The evolving understanding of IBK is also changing how researchers approach vaccine development.
For years, vaccine research has focused largely on targeting Moraxella itself. Yet field results have often been inconsistent, suggesting we may need to rethink not only which bacteria to target but how to target them.
A five-year randomized controlled trial compared a commercial Moraxella bovis vaccine with an autogenous vaccine containing M. bovis, Moraxella bovoculi and Mycoplasma bovoculi. Although the autogenous vaccine numerically reduced the cumulative incidence of IBK compared with the commercial and sham vaccines, the differences were not statistically significant. The researchers also found that stronger antibody responses did not necessarily translate into better protection under field conditions, highlighting the complexity of developing consistently effective vaccines.
Scientists are also searching for entirely new vaccine targets. Researchers with the USDA Agricultural Research Service recently identified two distinct capsular polysaccharides produced by M. bovis: a chondroitin-like capsule found in most strains and an α(2-8) polysialic acid capsule identified in a less common strain. Because bacterial capsules have served as effective vaccine targets for other pathogens, the discovery could help guide development of broader, more effective IBK vaccines.
The work remains in its early stages, but it reflects a broader trend in IBK research. Rather than refining the same approaches, scientists are beginning to explore entirely new aspects of the pathogen’s biology.
A Different Way of Thinking About Pinkeye
Taken together, the recent research points to a fundamental shift in how scientists view IBK.
For decades, the primary question was straightforward: Which bacterium causes pinkeye?
Today’s research is asking more complex questions:
How do microbial communities influence disease? Why do some cattle carrying Moraxella remain healthy while others develop severe corneal ulcers? Which bacterial strains are truly pathogenic? Can beneficial bacteria help prevent infection before it begins?
Rather than simply searching for better ways to eliminate Moraxella, scientists are increasingly exploring how microbial communities, bacterial genetics, host immunity and environmental risk factors interact to determine whether disease develops.
This shift in thinking may ultimately prove just as important as the next vaccine or treatment. Pinkeye remains one of the cattle industry’s most stubborn diseases, but researchers are finally asking different questions. If those questions lead to a better understanding of why some eyes stay healthy while others do not, they may also bring the industry closer to solving one of cattle medicine’s oldest challenges.
