Submitted to: Equine Veterinary Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/1995
Publication Date: N/A
Interpretive Summary: Leptospirosis is a cause of abortions, stillbirths, and neonatal deaths in horses and domestic livestock. Horses usually contract leptospirosis via contact with wildlife or domestic animals infected with various serovars of Leptospira interrogans. The most common cause of equine leptospirosis in the United States is infection with serovar pomona. In this study, an outbreak of leptospirosis in horses exposed to flood waters in California is described. Mixed serovar infections occurred with serovars pomona and hardjo isolated from mares. Serovar hardjo is associated with leptospirosis in cattle and this is the first reported isolation of this agent from horses in the United States. The hardjo isolate was further identified to be a subtype of serovar hardjo, type hardjoprajitno, thought to be exotic to the United States. The results of this study confirm that leptospirosis is a significant risk in horses and other species exposed to flood waters. In addition, the isolation of serovar hardjo type hardjoprajitno from animals in the United States is of considerable epidemiologic importance concerning leptospirosis in cattle. The results of this study will be of benefit to practicing veterinarians, diagnostic laboratories, biologics manufacturers, and scientists.
Technical Abstract: During the 1993 foaling season, a Thoroughbred farm with 70 mares was flooded as a result of heavy rains. Fifty-six of the seventy mares on the farm were pregnant. In a six-week period following the flooding incident, there were eight abortions, one stillbirth, two neonatal deaths, and illness in one other neonate. Leptospirosis was diagnosed based on one or more of the following: positive fluorescent antibody test on fetal tissue and urine samples, demonstration of spirochetes in liver and kidney sections stained by the Warthin-Starry technique, high leptospiral antibody titers in aborting mares and in mares with sick or dead foals, or isolation of Leptospira sp. from urine samples. Leptospires identified as serovar pomona type kennewicki and serovar hardjo type hardjoprajitno were isolated. A dual infection with Streptococcus zooepidemicus and Leptospira was diagnosed in the fetus submitted for evaluation.