Prevalence and serovars of leptospira involved in equine abortions in central Kentucky during the 1991-1993 foaling seasons

Department of Veterinary Science, College of Agriculture, University of Kentucky, Lexington 40511, USA.

In this study, the prevalence of leptospira-induced abortions/stillbirths for the past 3 foaling seasons (1991-1993) was determined, and fetal tissues and/or the mare's urine from positive cases were cultured in an attempt to isolate and identify the leptospira serovars responsible for the abortions. The sensitivity and specificity of the primary diagnostic tests, the fluorescent antibody test (FAT) and the microscopic agglutination test (MAT), used for the diagnosis of leptospirosis were also determined. For the 3 years, 74 (3.3%) of 2,264 abortion/stillborn submissions were diagnosed as leptospirosis. Twelve cases occurred in the 1991, 19 in the 1992, and 43 in the 1993 foaling seasons. Leptospires were isolated from 45 (60.8%) of the 74 cases, and they were identified as serovar kennewicki (43 cases), serovar grippotyphosa (1 case), and a serovar similar to pomona (1 case). Of the 29 culture-negative cases, serologic results indicated that leptospires in the Pomona serogroup (kennewicki is a member of this serogroup) were responsible for 25 abortions, leptospires in the Grippotyphosa serogroup for 1 abortion, and leptospires in the Sejroe serogroup for 1 abortion. The specificities of the FAT on fetal tissues and mare's placenta and of the MAT on fetal fluid were 100%. The sensitivity of the FAT was 98.7%, and that of the MAT was 81.3%.