The renal infections can occur in any age horse. The disease in foals causes weak foals that might be term or premature. There is not an approved vaccine for the horse against leptospirosis. Maintaining as hygienic an environment as possible, and isolating mares with confirmed leptospiral abortions, might prevent spread of the disease. However, I should mention that the disease is not common and varies in distribution through the country depending on environmental conditions.
Antibiotics can be effective in treatment of some forms of leptospirosis.
Newborn foals with leptospirosis have been treated successfully with penicillin intravenously. Older foals and adult horses with renal disease have also been effectively treated with antibiotics. The ocular disease is not likely a result of direct infection in the eye, therefore antibiotics might not be effective. Treatment of uveitis usually consists of topical, symptomatic therapy that will vary depending on ocular examination by your veterinarian. Unfortunately, mares infected with leptospirosis usually abort without premonitory signs.