Bacteroides fragilis - an overlooked cause of abortion in the mare?

A near late-term pregnant mare developed purulent vaginal discharge, fever and peripheral edema. Preterm foaling was medically induced, and the mare delivered a weak foal that was subsequently euthanized. Necropsy revealed an extensive, severe allantochoroiditis affecting the entire corpus segment. Necrosuppurative choroiditis with multiple colonies of gram-negative bacilli and suppurative bronchioalveolitis was found at histology. Anaerobic culture of the chorion revealed a mixed culture clearly dominated by Bacteroides fragilis. B. fragilis has not previously been associated with abortion in mares but is a known abortifacient in cattle and women. Limited use of anaerobic culturing in equine abortion investigations may have led to an underestimation of the importance of B. fragilis and other anaerobes as causes of abortion.