The Equine Immune Response to Leptospiral Infection

Leptospirosis is a reemerging zoonotic infection of worldwide importance (1,2,3). Leptospira spp. are found in over 160 mammals worldwide, including dogs, cats, cattle, horses and sea lions (4,5). Approved vaccines are only available for dogs, swine and cattle making infection in other mammals including humans a major health concern in many countries. Horses are accidental hosts for several serovars of Leptospira (6). The bacterium is easily transmitted via urine and fetal membranes/fluids from horse to horse and potentially humans. Veterinarians, farmers, slaughterhouse workers, butchers, sewer workers and others are at risk for contracting the disease either through direct contact (urine or body fluids) or indirect contact (contaminated water or soil) (7). Individuals working on farms are generally considered at highest risk of contracting the disease. Little information is available on the immune response of horses infected with leptospirosis. We propose to elucidate the immune response in horses exposed to and infected with leptospirosis and determine a pattern over time of potentially two key cytokines (tumor necrosis factor alpha and interleukin-10) and one enzyme (heme oxygenase-1). It is hoped that the information gained from this investigation will allow both farm managers and veterinarians time to treat mares at the appropriate time prior to abortion, potentially allowing mares to carry to full term. In addition to the outcome of a healthy foal, decreasing the number of abortions will reduce the risk of exposure of those individuals working on farms and veterinarians exposed to the aborted fetus and placenta. The significance of this is, both the fetus and placenta contain large numbers of pathogenic Leptospira, and therefore reducing exposure, will minimize farm workers and veterinarian’s chances of leptospiral infection.