Source: Michelle Arnold, DVM (University of Kentucky Ruminant Extension Veterinarian, Martin-Gatton College of Agriculture, Food and Environment Veterinary Diagnostic Laboratory)

Pinkeye, or Infectious Bovine Keratoconjunctivitis (IBK), is one of the most frustrating and costly diseases beef producers face. It negatively affects weaning weights, increases treatment costs and leads to discounts at sale due to corneal scarring. While it spreads quickly once it starts, the key to managing pinkeye lies in reducing risk—long before the first bad eye of the season.

Understanding the Disease

Pinkeye is caused by a complex mix of bacteria, most notably Moraxella bovis, Moraxella bovoculi, and Mycoplasma bovoculi. These organisms can live harmlessly in the eye until certain conditions—like eye injury or irritation—trigger them to become aggressive. M. bovis, for example, uses hairlike pili to attach to damaged corneas and releases toxins that destroy corneal tissue —leading to painful ulcers.

New research shows that pinkeye involves more than just one bacterium, making vaccine development difficult. Some strains are considered harmless, while others are highly virulent and resistant to antibiotics.

Reducing Risk Starts Early

Reducing the risk of pinkeye begins with strengthening your herd’s natural defenses. Good nutrition, especially adequate levels of trace minerals like selenium and copper, is essential. Clean, cool water helps maintain hydration and tear production, which protects the eye. Avoid stagnant water sources and regularly clean automatic waterers.

Environmental irritants are major contributors. Dust, ultraviolet (UV) rays, tall weeds and seed heads can all damage the eye, making it possible for bacteria to take hold. White-faced breeds like Herefords are more susceptible due to increased UV reflection to the eye’s surface. Providing shade and mowing pastures can help reduce these risks.

Face Fly Control

Face flies are the primary transmitters of pinkeye bacteria. They feed on eye secretions and can spread infection from animal to animal. Unlike horn flies, face flies aren’t affected by systemic insecticides. Instead, use a combination of feed-through insect growth regulators (IGRs), insecticide ear tags, dust bags and back rubbers strategically placed in high-traffic areas.

Start IGRs in mid-spring, about 30 days before fly season, and continue until 30 days after it ends. Rotate insecticide products annually, based on mode of action (MOA), to prevent resistance. Aim to keep face fly numbers below 10 per head.

Recognizing Symptoms and Acting Fast

Early signs of pinkeye may include excessive tearing, squinting and blinking. Prompt treatment is critical to prevent spread and minimize damage. Long-acting injectable antibiotics like oxytetracycline (LA-300®) or tulathromycin (Draxxin®) are effective and labeled for pinkeye treatment. In severe cases, eye patches or surgical procedures may be needed to protect the cornea.

Topical fly repellents and isolating affected animals can also help reduce transmission. Always consult your veterinarian for treatment decisions and prescriptions.

The Role of Vaccines

Vaccines can reduce the number and severity of cases but aren’t foolproof. Commercial vaccines work best when the strain in the vaccine matches the strain in your herd. When they don’t, custom-made (autogenous) vaccines may be more effective. 

Timing is key—start vaccinations 4–6 weeks before pinkeye season and follow up with a booster for full protection.

Pinkeye is a complex disease, but control is possible with a proactive approach. Focus on nutrition, clean water, fly control and minimizing eye irritants. Work closely with your veterinarian to develop a treatment and vaccination plan tailored to your herd. With early action and consistent management, you can reduce the impact of pinkeye and keep your cattle healthy and productive.

Contact your local (COUNTY NAME) Extension office or veterinarian for more information on how to address pinkeye in cattle.  

Resource: Pinkeye Fact Sheet 

### 

Educational programs of the Cooperative Extension Service serve all people regardless of economic or social status and will not discriminate on the basis of race, color, ethnic origin, national origin, creed, religion, political belief, sex, sexual orientation, gender identity, gender expressions, pregnancy, marital status, genetic information, age, veteran status, or physical or mental disability.    

The University of Kentucky Martin-Gatton College of Agriculture, Food and Environment news and communications team provides monthly Extension Exclusives in the categories of Horticulture, Agriculture and Natural Resources, 4-H and Family & Consumer Sciences. To see more exclusives, visit https://exclusives.ca.uky.edu.  

---

ANR