Horse Journal OnCall: Leptospirosis In Horses

What do you know about Leptospirosis in horses? My 6-year-old off-track Thoroughbred was diagnosed with re-occurring uveitis. When this all started, he tested positive for Leptospirosis with the eye fluid and but negative in the blood. We treated him with a series of ointments, Banamine, and steroids for the uveitis, and he was given enrofloxacin for the lepto. Once his eye was clear of symptoms, he received a cyclosporine implant per the ophthalmologist’s recommendations.

Fly masks can filter about 50% of UV light.

He recently had another flare-up. The opthamologist said we could consider a second implant, but we’re not sure if this is financially possible as his eye is no longer covered under insurance. We tested him again for Lepto, and he was positive in the eye but not in the blood.

Is it possible that my horse was re-infected with Lepto or that it never went away? My ophthalmologist is not concerned about the sun affecting his eye, but she does want him to wear fly masks during fly season, but I am not sure why.

Contributing Veterinary Editor Grant Miller DVM responds:

With Leptosporosis, it is thought that Lepto pomona and Lepto Bratislava have been associated with uveitis in horses. The reason that I use the words “thought that” is that a statistically significant number of the horses with recurrent uveitis test positive for these serovars of Lepto.

However, you can also find normal horses that do not have uveitis that test positive for Lepto, so it is unclear whether or not it has anything to do with the uveitis flare-up in affected horses. Could it be that these horses are missing a gene for a certain enzyme that allows the Lepto to set off an inflammatory reaction in the eye? We just do not know at this time.

Regardless, it has become common practice in some parts of the country to test horses with recurrent uveitis for Lepto. If they test positive, the infection has traditionally been cleared using doxycycline systemically, however due to national backorder, it looks like these vets are trying enrofloxacin instead. That may be the reason why it is not testing negative at this point.

Whether you clear the Lepto infection or not, the uveitis can continue to occur. In other words, once the problem starts, it is here to stay. Fly masks can effectively filter about 50% of UV light, which makes them beneficial in reducing recurrence of uveitis.

Early intervention is key – identifying a flare-up early on and getting anti-inflammatories and antibiotic eye meds on board ASAP will help avoid pain, damage and expense down the road. You should keep your veterinarian informed of any flare-ups. 

Some veterinarians provide their client with an emergency kit including contingency instructions on what to do if they think a uveitis flare-up is occurring. You may want to go back to your veterinarian and talk this through. I sometimes authorize my clients to put antibiotic eye ointment in the eye, give Banamine orally, and place the horse in a dark stall with a fly mask. But I also require that they call me to come look at the eye and stain it with fluorescein prior to the application of topical dexamethasone or atropin. We’ve tried to give you enough information to go back to your veterinarian with questions specific to your horse.

Editor’s Note: Read a story about an Appaloosa with painful uveitis, who was helped at the New Bolton Center.

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