Immunology of infective preterm delivery in the mare

Placentitis is reported to be the cause of 9.8-33.5% of abortions, stillbirths and perinatal losses in horses. Bacterial infections are responsible for 53% of placentitis cases with Streptococcus equi ssp. zooepidemicus being isolated in 28% of these cases. Clinically, mares may have a vaginal discharge, show udder development, lactate prenatally and deliver a premature or dead foal. Major aspects of the pathogenesis of infectious preterm delivery that may require more effective therapeutic targeting are myometrial contraction, immunological aspects of preterm delivery, and the effects of proinflammatory cytokine signalling on activation of the fetal hypothalamic-pituitary-adrenal axis. This article focuses on current knowledge of inflammatory signalling secondary to equine placentitis, and the interplay among inflammation, loss of myometrial quiescence and activation of the fetal hypothalamic-pituitary-adrenal axis.