Mare reproductive loss syndrome

This chapter discusses the mare reproductive loss syndrome (MRLS). It is an unique disease syndrome of early fetal loss and late fetal loss (EFL/ LFL) during a specific period of time occurring with smaller numbers of fibrinous pericarditis (FP), unilateral uveitis (UU) and Actinobacillus encephalitis (AE). Multiple risk factors were identified by epidemiological investigations, one of which is presence of ETCs in pastures. Clinical findings of fetal loss was observed in the first trimester and in the last trimester of gestation; the signs observed included sero-sanguineous or purulent vulvar discharge, and fetal membranes protruding from their vulva with fetuses located either in the vagina or vulva. There was no substantial evidence to suggest that MRLS had a long-term effect on fertility. For pathological findings, EFL placentas and fetuses samples were submitted for examination to different referral laboratories. Various investigations have been done to rule out toxic etiological and various animal models have been examined. Comparison of isolates from different mares demonstrates dissimilarities suggesting that the source of fetal and placental infection in each mare is derived from its own bacterial population and that this bacterium may not be the primary etiological agent. The observations of experiments with irradiated ETCs suggest that MRLS may be caused by an unidentified toxin present in ETCs, which leads to the separation of placenta from the uterus leading to hypoxia with secondary invasion of bacteria found in the oral and gastrointestinal tract of the mare.