Pinkeye: Causes, Prevention, and Treatment

A Common Problem That Costs More Than You'd Think

Pinkeye, technically known as Infectious Bovine Keratoconjunctivitis (IBK), is one of the most common diseases affecting cattle worldwide. It rarely kills, but it causes real economic losses through reduced weaning weights, treatment costs, labor, and permanent eye damage in severe cases. In Texas, pinkeye is especially problematic during hot summer months when face flies are most active.

What Causes Pinkeye

The Pathogens

The classic pinkeye pathogen is Moraxella bovis, but Moraxella bovoculi is increasingly recognized as a significant player. Other bacteria may also contribute to the disease complex.

Key characteristics of Moraxella bovis: It produces toxins that damage the cornea, has pili (hair-like structures) that attach to eye tissue, is highly contagious between cattle, and survives in eye secretions and on flies.

The Disease Triangle

Pinkeye outbreaks require three factors working together:

``` SUSCEPTIBLE HOST (cattle with vulnerable eyes) /\ / \ / \ / \ / PINKEYE \ / OUTBREAK \ / \ PATHOGEN ______________ ENVIRONMENT (Moraxella) (UV, dust, flies, grass seeds) ```

How Pinkeye Spreads

Face flies are the primary vehicle. They feed on eye secretions, carry bacteria from infected to healthy cattle, and can transmit the organism for several days after exposure.

Direct contact also plays a role through nose-to-nose contact, shared feed and water sources, and grooming behaviors. Fomites like halters, handling equipment, contaminated hands, and shared face fly control devices can spread the bacteria as well.

Predisposing Factors

Recognizing Pinkeye

Early Signs (Stage 1)

• Sensitivity to light (photophobia)
• Squinting, holding eye closed
• Reddening of conjunctiva (white of eye)
• Slight swelling of eyelids
• Clear discharge
• Clouding begins at a spot on the cornea

Progressing Disease (Stage 2-3)

• Corneal ulcer develops (visible pit/crater)
• White/yellow appearance of cornea
• Increased discharge (may become thick, yellowish)
• Obvious pain behavior
• Blood vessels grow into cornea (pink streaks)
• Severe swelling
• Pus accumulation
• Risk of corneal rupture

End Stage (Stage 4)

• Corneal rupture: Eye deflates, permanent blindness
• Phthisis bulbi: Eye shrinks, non-functional
• Panophthalmitis: Entire eye infected

Typical Disease Timeline

Prevention Strategies

1. Fly Control

Dust bag and oiler placement matters. Water access points are ideal locations, and mineral feeders work well for voluntary use. Keep devices filled and functional throughout fly season.

2. Pasture Management

Clipping pastures eliminates the seeds and awns that scratch eyes and also reduces fly habitat. Providing shade is important for cattle with unpigmented eyelids, though shade structures do concentrate cattle and increase fly contact, so there's a trade-off to consider. Managing traffic patterns through dusty areas and working cattle on cool mornings can also help reduce risk.

3. Vaccination

Several vaccine options exist, including commercial Moraxella bovis vaccines, autogenous (custom-made from herd isolates) vaccines, and some combination vaccines.

Vaccination works better for reducing severity than outright preventing cases, and autogenous vaccines may be more effective for specific herds. Complete the series before fly season, and booster annually before fly season starts. Keep in mind that vaccines may not match circulating strains, and immunity to pinkeye is neither complete nor long-lasting.

4. Genetic Selection

Breeding bulls with dark eye pigment and culling cows that consistently produce calves with white faces and no pigment will improve your herd over time. Repeated pinkeye cases in the same animal suggest genetic susceptibility, and culling repeat offenders makes sense both economically and genetically.

5. Minimize Transmission

During an outbreak, separate severe cases if practical and step up fly control. Consider moving the herd to a different pasture to get away from contaminated ground. Avoid dusty conditions when possible, and consider treating all eyes preventively during the peak of a high-risk season.

Treatment

Treatment Principles

Treat early (before ulceration is best), use appropriate antibiotics, provide UV protection, control pain and inflammation, and prevent secondary infection. Those five priorities guide every pinkeye treatment decision.

Antibiotic Options

Eye Patching

Patches shield from dust and flies, hold medication in contact with the eye, and reduce pain from light. Options include glue-on patches (easiest, may fall off), suture-in patches (more secure, skill required), and third eyelid flaps (surgical, done by the veterinarian).

When patching, apply the patch firmly but not too tight, leave adequate ventilation, remove or replace in 2 to 3 days, and always check for worsening under the patch.

When to Call the Veterinarian

Call when you suspect rupture, see severe eye swelling, get no improvement after treatment, or have multiple severe cases. Your vet can suture the third eyelid over the cornea, perform surgical debridement, provide advanced pain management, and assess for other underlying causes.

Chronic Cases

Corneal scarring may affect vision permanently but usually doesn't prevent the animal from grazing. It is a cosmetic defect that affects sale value, and no treatment reverses the scarring once it forms.

Economic Impact

Direct Costs

Indirect Costs

Weaning weight reductions of 15 to 30 pounds per affected calf are common. At $1.50/lb, that's $22.50 to $45 per calf walking out the gate. Condemnation of affected eyes at slaughter adds to the total.

Prevention ROI

Ear tags run $1.50 to $4 per head, pour-ons cost $2 to $5 per application, and dust bags or oilers run $50 to $150 for setup plus refills. When you stack those numbers against treatment costs and weight loss, prevention almost always pays for itself.

Special Considerations

Calves vs. Adults

Calves carry more risk because their lower body weight means disease stress hits them harder. They may not be vaccinated yet, and many (depending on breed) have lighter eye pigmentation. Adults may be carriers, and new introductions are particularly vulnerable.

Breed Differences

Breeds at higher risk include Herefords (classic "bald-faced"), Simmental (variable), Charolais (light pigmentation), and any breed with unpigmented eyes. Breeds at lower risk include Brahman and Brangus (dark pigment) and most dark-colored breeds. Through selective breeding over generations, herd pigmentation improves steadily.

Concurrent Diseases

IBR (Infectious Bovine Rhinotracheitis) may appear similar or run concurrently with pinkeye. Vaccination helps distinguish the two, especially in IBR-vaccinated herds. Vitamin A deficiency increases susceptibility, so check cattle on dry, brown forage.

Outbreak Management Checklist

When Pinkeye Breaks Out

Immediate:

• Treat promptly (within 24-48 hours of first signs)
• Intensify fly control measures
• Separate severe cases if practical

• Consider pasture move (away from high grass)
• Evaluate dust and UV exposure
• Treat all new cases promptly
• Record all cases and treatments

• Re-treat non-responders
• Track recovery vs. complications
• Document outbreak for future reference

• Evaluate treatment success
• Plan improved prevention for next season
• Consider autogenous vaccine if commercial vaccine failed

Bottom Line

Face flies are the primary vector for pinkeye, so aggressive fly control is the single most important prevention tool you have. Early treatment (within 48 hours of first signs) prevents most of the serious complications, and UV protection through patches and shade makes a real difference in healing.

Vaccination has variable success, so use it as part of your overall program rather than relying on it as the sole line of defense. Genetics matter over the long haul; selecting for pigmented eyes across generations steadily reduces your herd's vulnerability. On the environmental side, managing pastures to reduce dust and controlling tall weeds cuts down on the eye irritation that gives bacteria their opening.

When you run the economics, prevention almost always comes out ahead. Treatment costs and weight loss add up fast during a bad pinkeye year. Involve your vet early for severe cases and for planning your prevention program before next season.

Resources

Further Reading

• Texas A&M AgriLife Extension - Pinkeye Management
• Beef Quality Assurance - Treatment Guidelines
• Local veterinarian for autogenous vaccine options

Emergency Contacts

• Your veterinarian: _______________
• Texas A&M Veterinary Diagnostic Lab: (979) 845-3414

Related Resources

• 5.1.1 Bovine Respiratory Disease Prevention
• 5.2.6 Eye and Ear Health Indicators
• 5.5.7 Disease Symptom Quick Reference
• 5.3.2 Core Vaccines for Texas Cattle