Published January, 2013

It is leptospirosis abortion season once again in Kentucky. The University of Kentucky Veterinary Diagnostic Laboratory (UKVDL) has confirmed 11 leptospirosis abortions so far in the 2012-2013 reproductive season. Last year, 24 were confirmed for the entire season. Graph 1 (left) shows a delay in confirmation of the first case in comparison to last year. We still can expect abortions for about three more months. Graph 2 (below left) provides a comparison of the last five years of confirmed lepto abortion cases.

Leptospirosis is a transmissible disease of animals and humans caused by infection with the spirochete Leptospira. Pathogenic leptospires were formerly classified as members of the species Leptospira interrogans; however, the genus has recently been reorganized, and pathogenic leptospires are now identified in 17 named species and four genomospecies of Leptospira. There are more than 200 distinct leptospiral serovars recognized, and these are arranged in 23 serogroups. Previous studies in Kentucky suggest that leptospirosis was the leading cause of abortion in domestic animals, mostly horses in 1989, and the third the most common bacterial cause of abortion diagnosed from 1986 through 1991.

Clinical leptospirosis in horses, cattle, and companion animals is often associated with recent exposure, directly or indirectly, to surface water contaminated by rat urine. Affected horses typically live in an environment that combines a pasture and a stable shared with a number of small mammals. In winter most at-risk horses are fed roughage, which is almost inevitably contaminated by mouse, raccoon, and often rat urine. Cattle, dogs, as well as horses, are exposed to animals that can be reservoirs of leptospires.

A definitive leptospirosis diagnosis is very difficult because culture of leptospira takes up to 13 weeks and is often hampered by other bacterial contamination. The gold standard for diagnosing leptospirosis is the microscopic agglutination test (MAT), in which patient sera are reacted with live antigen suspensions of major leptospiral serovars. However, MAT works only with serum, cannot be used with urine or fresh tissues, and it is often difficult to differentiate an active infection from previous exposures. The other methods include serological assays such as ELISA, fluorescence antibody (the UKVDL's method for confirmation on fetal tissues) and immunohistochemistry.

Source: Edited Jan. 10 VDL bulletin. For more information about the UKVDL and its services, please visit http://vdl.uky.edu.