Various studies report that 8-19% of equine pregnancies result in abortion for reasons ranging from placentitis to equine herpesvirus-1 (EHV-1). While not pleasant to think about, a post-mortem examination is crucial in these cases to determine what caused the abortion; confirming disease is the catalyst for taking appropriate biosecurity measures to halt its spread.

For this reason, Luke Bass, DVM, MS, Dipl. ABVP, a field service veterinarian at Colorado State University’s Veterinary Teaching Hospital, in Fort Collins, reviewed the steps practitioners should take when performing a post-mortem examination on an aborted fetus in a presentation at the 2015 American Association of Equine Practitioners Convention, held Dec. 5-9 in Las Vegas.

“There are many causes of abortion, and identifying them could aid in further prevention of subsequent abortions,” said Bass.

He described some of the common causes based on four retrospective studies of 7,800 cases:

  • The majority (58.5-67.3%, depending on the study) of causes were infectious;  
  • Noninfectious causes included twinning (5%), placental insufficiencies, umbilical cord problems (torsions making up 5-60%), congenital abnormalities, and fetal resorption;
  • The cause of 17% of abortions was unknown;
  • Bacterial placentitis (inflammation of the placenta) is the most common cause of infectious abortion at 21%, with the primary causative bacteria being Streptococcus zooepidemicus;
  • Viral causes of abortion include equine herpesvirus (EHV) -1 and -4 and equine viral arteritis, with EHV-1 being most common (4%); and
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