Leptospirosis and Blindness

I am just discovering one of my broodmares is virtually blind. No spook etc when I make sudden movements etc. She seems to be 100% blind on the left and at least 75% on the right (or FREAKISHLY unspooky!!!). I was told she was quite ill for a number of weeks several years ago. No definite diagnosis was ever given, but another horse on that property DID contract lepto and did go blind.

My mare has no squinting, no lacrimation (that is not normal for a healthy eye) and it really doesn’t seem to bother her pain wise.

Will this get worse (if in fact it’s lepto induced blindness) or would it likely settle to what it is now?

Leptospirosis is a bacteria that can indirectly cause blindness if it gets into the fluids inside the eyeball and triggers repeated bouts of immune-mediated uveitis (moon blindness). We routinely check lepto titres on horses with repeated uveitis episodes, and will treat those with signs of active infection. Leptospirosis comes in many strains (called serovars) and can cause a variety of health problems including kidney disease and abortion. It is spread in the urine of infected wildlife, so it is easy to pick up from contaminated wetlands and water troughs. In endemic areas, especially in breeding operations, the small animal vaccine can be used off-label to provide some immunity to the horses.

Your mare’s history of illness could indicate she had contracted this bacteria, but I would check a titre before assuming she has an active case at this moment. The blindness that she has now would be from secondary effects of inflammation in the eye- cataracts, detached retina, corneal opacities, etc. rather than from active infection. Your vet can determine how much vision she retains by examining the eye and testing the pupil reflexes, and discuss whether vaccination might be advisable considering she is a broodmare and this bacteria can cause abortion. Quickly controlling any future episodes of inflammation is the most important thing you can do to preserve her vision going forward. Horses can adapt amazingly well to blindness, especially if it is slow to develop, and a solid old broodmare is probably not surprised by much anymore either way. You can certainly bell the foal, but be careful of course to use a quick release collar in case the little monkey gets caught J

Melissa McKee DVM