Overview
- Pinkeye is a common, contagious bacterial eye disease in cattle.
- Caused primarily by Moraxella bovis (M. bovis).
- Found worldwide and has significant economic impact.
- Spreads rapidly within herds.
- Estimated U.S. losses were $150 million in 1993; current figures likely much higher.
Causes
- M. bovis is the main infectious agent.
- Other bacteria (Moraxella bovoculi, Mycoplasma spp.) and viruses (IBR virus) can contribute.
- The normal bovine eye has defenses, but irritation allows bacteria to invade.
Environmental Triggers:
- Ultraviolet (UV) Light:
- Sensitizes the eye, increasing infection risk.
- White-faced cattle are more vulnerable due to lack of pigmentation.
- Face Flies (Musca autumnalis):
- Irritate eyes and spread bacteria.
- Can remain infected for up to three days.
- Wind, Dust, and Plant Material:
- Grasses, weeds, and hay dust cause irritation.
- Round bales and overhead feeders increase risk.
- Confined Feeding Operations:
- Higher dust exposure but lower impact compared to UV, flies, and plant debris.
Transmission
- M. bovis is carried by asymptomatic cattle (carriers), spreading to new animals.
- Transmission occurs via:
- Direct contact (eye and nasal secretions).
- Flies.
- Contaminated surfaces.
- Peak transmission in summer and fall due to UV exposure, flies, and pollen.
- Stressors like weaning, high stocking density, and other infections increase risk year-round.
Clinical Signs
- More common in younger cattle due to lack of immunity.
- Infection rates can vary from minor outbreaks to 80% herd infection.
- Incubation: 2–3 days (up to three weeks experimentally).
- Symptoms:
- Swollen, red conjunctiva.
- Excessive tearing, squinting, frequent blinking.
- Reduced appetite due to pain.
- Corneal ulcers (small opaque spot progressing to full corneal discoloration).
- Severe cases: corneal rupture, blindness (infrequent).
- Recovery typically within 3–5 weeks, but some cases leave corneal scars.
Treatment & Management
- Isolation: Remove affected animals to prevent spread.
- Veterinary Treatment:
- Systemic antimicrobials.
- Topical or conjunctival antibiotics (with prescription).
- Non-steroidal anti-inflammatory drugs (NSAIDs) for pain relief.
- Protection from UV Light:
- Provide shade.
- Use eye patches or eyelid sutures (with veterinary guidance).
- Fly Control:
- Implement insecticide sprays, tags, and backrubbers.
- Feed Management:
- Avoid feeding from overhead feeders.
- Reduce chaff and seed head exposure.
- Dust Control:
- Manage dust levels in confined feeding environments.
Prevention
- Fly Control:
- Insecticide tags, sprays, backrubbers, and dust bags.
- Feed-through growth regulators.
- Manure management for fly reduction.
- Vegetation Management:
- Mowing and weed control to reduce eye irritants.
- Hay & Feed Practices:
- Lower overhead hay feeders.
- Spread hay to reduce concentrated exposure.
- Avoid hay with mature seed heads.
- UV Protection:
- Breed for pigmented eye areas.
- Introduce Brahman influence for better pigmentation.
- Provide adequate shaded areas.
- Disease Control:
- Isolate infected animals.
- Improve herd nutrition and vaccination programs.
- Reduce stress from weaning, shipping, and handling.
Vaccination
- Commercial and autogenous vaccines are available but vary in effectiveness.
- Best results occur when vaccines match the specific bacterial strain in the herd.
- Culture and serotyping help identify the best vaccine.
- Consult a veterinarian for vaccine recommendations.
Key Prevention Strategies
- Early Detection & Treatment: Prompt antibiotic treatment improves outcomes.
- Isolation: Separate new and infected cattle to prevent spread.
- Environmental Management: Reduce UV exposure, flies, dust, and plant irritants.
- Vaccination: Use as part of a comprehensive disease control strategy.
- Optimize Herd Immunity: Proper nutrition, stress reduction, and vaccination programs enhance resistance.
By implementing these strategies, producers can significantly reduce pinkeye incidence and economic losses in their herds.
