How leptospirosis and ERU are related

Leptospirosis is caused by Leptospira bacteria. Horses can be exposed through environments contaminated by infected animal urine, including water, mud, feed, or surfaces. Exposure does not create the same outcome in every horse. Some infections may cause no obvious signs, while others can involve systemic illness, pregnancy loss, kidney or liver concerns, or eye disease.

Equine recurrent uveitis, often shortened to ERU, is repeated inflammation inside the eye. Leptospira-associated disease is one important part of the ERU conversation, but it is not the only possible cause or pathway. The veterinarian must separate uveitis from ulcers, trauma, infection, glaucoma, cataract, and other eye problems that can look similar from the barn aisle.

What to do before the veterinarian arrives

1. Stop work and protect the horse. Move the horse away from hazards and bright glare if this can be done safely.
2. Call and describe the eye. Report onset, squinting, tearing, cloudiness, swelling, discharge, pupil appearance, vision concern, fever, recent travel, wildlife exposure, and previous episodes.
3. Do not medicate from the old bottle. Eye medication that helped another episode may be wrong or harmful for the current problem.
4. Do not apply topical products near the eye. Keep liniment, grooming spray, skin cream, shampoo, fly spray, and home mixtures away unless the veterinarian directs a specific product.
5. Prevent rubbing without improvising pressure. Follow veterinary instructions for safe restraint, a mask, or another protective step.
6. Preserve the timeline. Note when signs began and take a clear photo only if it does not delay care or create risk.

What the veterinary workup may include

The veterinarian may evaluate vision, eyelids, cornea, pupil, pressure, and internal eye structures using an ophthalmic examination and selected tests. Bloodwork, ocular samples, ultrasound, or referral may be considered based on the horse and findings. Testing choices differ, and a laboratory result must be interpreted with the complete eye examination.

Treatment aims to control inflammation, manage pain, address the identified cause when possible, and protect the eye. Medication type, dose, frequency, and duration are case-specific. Some horses require frequent early treatment, specialist care, procedures, or long-term monitoring. Never shorten or restart medication without veterinary direction.

Why follow-up matters

An eye can look more open before inflammation is fully controlled. Keep recheck appointments and learn the horse's subtle early signs. A recurrent episode may begin with mild squinting, increased tearing, avoiding light, rubbing, or a change in attitude. Early contact gives the veterinarian a chance to assess the eye before the episode becomes louder.

Reduce barn exposure without promising prevention

• Provide clean drinking water and protect feed from contamination where practical.
• Manage rodents and wildlife access with a realistic barn plan.
• Reduce standing water and urine-contaminated areas when possible.
• Use gloves and hygiene guidance when handling urine, aborted material, or drainage.
• Ask your veterinarian about local leptospirosis risk, testing, and vaccination.

No barn can remove every exposure. Risk reduction supports the veterinary plan, but it does not replace urgent eye care or guarantee that ERU will not occur. For broader vetted horse-care routing, use the Horse Health Library.

Common mistakes

• Waiting overnight to see whether a painful eye clears.
• Using leftover steroid or antibiotic eye medication without an examination.
• Putting liniment, skin cream, or herbal preparations near the eye.
• Assuming every uveitis episode has the same cause or treatment.
• Stopping medication when the eye first looks better.

Educational note: This article does not diagnose or treat eye disease. Equine eye pain and vision change are time-sensitive and require veterinary examination.