b'AFTER THE IMMUNE CHALLENGEAt this time, however, there areOcular manifestationimportant clinical disease we see in insufficient data to support any recom- horses with leptospirosis, with over 60% mendations regarding these strategies,is the most importantof equine recurrent uveitis cases attribut-Pusterla adds. Owners should follow theclinical disease we seeable to this pathogen, says Ann Dwyer, products and veterinarians instructionsDVM, a private equine practitioner at to achieve the best possible outcome.in horses with leptospi- Genesee Valley Equine Clinic, in Scotts-rosis, with over 60% ofville, New York.LeptospirosisExamples of typical ERU signs include The persistent and tenacious cork- equine recurrent uveitisa hot, painful eye (evidenced by the screw-shaped Leptospira bacteria live incases attributable tohorse holding the eye closed) with light water and soil and also reside in infectedsensitivity, excessive constriction of the horses reproductive fluids and urine.this pathogen. pupil (miosis), prominent blood vessels Horses inadvertently ingest the bacteria,DR. ANN DWYER on the surface of the eye, and a green/which gain access to the body throughorange hue in the posterior segment (the the gums and lips. Once theyve penetrat- back of the eye). ed tissues and accessed the bloodstream,Long-term consequencesLeptospira Appaloosas and Warmbloods are they run amok like unsupervised childrenorganisms, predominantly Leptospiragenetically predisposed to ERU, but all at an amusement park. Initial signs ofinterrogans serovars Pomona and Grip- horses living in temperate climates, par-infection include abortion in pregnantpotyphosa, have an affinity for the equineticularly river valley regions, are at risk mares and kidney disease or jaundiceeye. Therefore, veterinarians sometimesfor developing leptospiral ERU. in foals born to infected mares. Manydetect live leptospires in the ocular tissuesResearchers dont yet understand horses, however, show nonspecific mildof horses with recurrent uveitis (ERU), anexactly when horses with leptospiral-signs of disease (described by owners asimmune-mediated process that threatensassociated ERU get infected and how simply fever and malaise) that resolveotherwise healthy horses vision. long it takes for ocular disease to develop. without veterinary intervention. Ocular manifestation is the mostI have always thought it takes months for ocular disease to develop following in-fection, but I do not have a specific num-ber of months to suggest, says Dwyer. In some cases it might take years.The problem with identifying the interval from infection to ocular disease is that acute leptospirosis is often a very mild disease, she continues. Unless it causes abortion or renal (kidney) disease, leptospirosis is very rarely diagnosed in the primary stage. When I have diagnosed acute disease in practice in horses that are not pregnant, usually the horse has just been a little sick and has gotten bet-ter quickly.Following abortion due to Leptospira infection, some mares have gone on to develop ocular disease, whereas others have not. Dwyer admits that treatment options, even with the availability of systemic an-tibiotics, remain limited, making this an extremely frustrating disease to manage. Based on my experiences, prognosis for vision loss is probably around 50%, she says. Researchers at Auburn University have reported that a very low dose of the anti-biotic gentamicin injected into the vitre-ous (back of the eye) might be promising in some cases. Dwyer warns, however, that this is not a procedure for untrained practitioners to try. 20September 2019The Horse | TheHorse.com'