By Nathalie Fouché, DrMedVet, Dipl. ECEIM, of the Swiss Institute of Equine Medicine, and Vince Gerber, DVM, PhD, Dipl. ACVIM, ECEIM, FVH, of ISME, WEVA treasurer and junior-vice president.

Although many horses are exposed to the bacteria Leptospira interrogans, only a few develop clinical disease. The presence of circulating antibodies against different forms (serovars) of these bacteria suggest anywhere from 10% (in a Canadian study) to 33% (in an Australian survey) to more than 50% of healthy horses (in Swiss research) are exposed to Leptospira species.

The main health concerns associated with Leptospira species are abortion in pregnant mares and equine recurrent uveitis. However, foals can also develop disease, although in much lower numbers, due to exposure to the bacteria. Acute renal (kidney) disease and respiratory failure in foals have been described in the literature due to leptospirosis infection.

“Foals presented with acute renal injury due to leptospirosis usually show nonspecific clinical signs,” said Nathalie Fouché, DrMedVet, Dipl. ECEIM, of the University of Bern, in Switzerland, who recently reviewed the clinical records of these cases. “Those foals are unwilling to nurse, obtunded (lacking alertness), and might have a high rectal temperature