Chapter 74 - Mare reproductive loss syndrome

Abstract

In 2001 and 2002, in the Ohio River Valley, a syndrome characterized by early fetal losses and late-term abortions occurred in mares and resulted in significant financial losses to the local horse industry. Affected mares frequently showed few clinical signs prior to abortion. Lesions were not consistently found, but some of the more common lesions included funisitis, placental edema, and placentitis. The most common microorganisms isolated were non-β-hemolytic streptococci and actinobacilli, which are common commensal organisms in the equine gastrointestinal tract. Increases in the incidences of fibrinous pericarditis, unilateral uveitis, and Actinobacillus meningitis in horses were also noted. The eastern tent caterpillar (ETC) was identified as the primary risk factor, and subsequent experimental studies were able to reproduce abortion in mares through gavage of intact or fragmented ETC. Further studies isolated the pathogenic component of the ETC to the setae (hairs) of the caterpillar.