Equine Abortion

Equine Abortion

1. Placentitis

   • -Common cause of abortion -Bacteria: Streptococcal species and E. coli -Most common route: ascending infections -Results in inflammation and placental detachment from cervical star region -Placental thickening, separation from endometrium, inflammation Treatment:  -Antimicrobial therapy -NSAIDs (Flunixin meglumine) -Altrenogest (progesterone) to promote uterine quiescence -Clenbuterol (sympathomimetic) to suppress uterine motility -Pentoxyfylline to decrease inflammatory mediators and increase uterine blood flow

2. Viral Abortions

   • -Most common: Equine herpesvirus type 1 (EHV-1), but also EHV-4 and equine viral arteritis (EVA) -Administer vaccine against EHV-1 at 5, 7, and 9 months of pregnancy -EHV-1 can also result in sublinical to clinically relevant respiratory infections -Abortion may occur soon after maternal infection or several weeks after -Fetus infected during viremic episode--> abortion may be induced by rapid placental detachment -Fetus can become infected by chorionic vasculature or by inhalation of infected amniotic fluid Diagnosis: -On aborted fetus: Small necrotic foci on liver, necrotizing bronchiolitis, and intranuclear inclusion bodies on histologic examination -Some fetuses born alive and have neonatal herpesvirus infection-- respiratory distress, icterus, fever, lethargy, death -Virus neutralization tests, indirect immunofluorescence, PCR, and virus isolation Treatment: -No direct treatment -Antivirals (acyclovir and valacyclovir) of theoretical benefit

3. Non-Infectious Causes

   • Twin Fetuses
     • -Unlikely that it will be carried to full-term b/c of the limited endometrial surface available for allantochorion to attach (due to diffuse microcotyledonary placentation) -Compete for adequate nutrition and placentation -Fetal growth becomes rapid and more demanding until one or both of fetuses becomes progressively emaciated and dies -If carried to full term: one or both are stunted in growth and size from intrauterine growth retardation
   • Umbilical Torsion
     • -Relatively uncommon -Fetus is able to rotate within amniotic sac and can result in excessive twisting of umbilical cord -Constriction of normal flow through the umbilical cord along with edema, hemorrhage and thrombosis, culminating in fetal death