June 13, 2011
If your horses are kept anywhere near cattle, it’s possible they could contract equine recurrent uveitis from leptospirosis-infected cattle.
One of our best “cow” mares was diagnosed a few years ago with recurring uveitis. She has been treated and seems to be doing fine, although we watch for recurring symptoms so we can treat it if it reappears.
I now read that cattle may carry leptospirosis, which can cause uveitis. Since this mare works cattle and lives pastured right next to them, is this what caused it? Will my other horses be at risk?
Yes, you are correct that cattle can be infected with leptospirosis. It is shed in urine and fetal fluids and fetal tissues. The relationship between leptospirosis and equine recurrent uveitis (ERU) is complicated and not fully understood. When a horse is infected with leptospirosis, it most commonly causes fever, decreased appetite, acute uveitis, mild colic signs and kidney disease. The current theory about lepto and ERU is that some horses either develop persistent intraocular infection with the organism or they develop an unusual immune reaction to the organism without becoming persistently infected. The duration of time it would take to develop ERU after being infected with lepto is unknown.
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Most well-managed cattle farms monitor for lepto and vaccinate their herds. Lepto is a cause of abortion in cattle, so any unexpected cases of abortion should be investigated by a veterinarian. Lepto can also live in water sources like ponds, so testing those water sources is also an option if you are concerned about lepto on your farm. If your other horses aren’t having the clinical signs listed above and you don’t have multiple horses affected with ERU on your property, it would be hard to justify all this expensive testing. If you do have multiple horses with ERU or unexplained abortions in cattle or horses, then testing the cattle and other horses may be worthwhile. There is a lepto vaccine for cattle, but it has not been demonstrated to be useful in horses with ERU, and if you do not have other cases of ERU on the farm, I wouldn’t recommend the vaccine.
— Dr. Amber Labelle, member of The American Association of Equine Practitioners