identifying the cause of equine abortions

Late-term abortion is one of the most devastating issues horse breeders face. Every pregnancy represents a labor of love with a substantial amount of time, energy, and money put into achieving the perfect foal. Every pregnancy loss raises questions concerning our ability to have prevented that loss and whether we could have done more.

Recently, Dr. Alan Loynachan (DVM, PhD) addressed the underlying causes of the 898 equine abortions examined by the University of Kentucky (UK) Veterinary Diagnostic Laboratory over the 2016 and 2017 breeding seasons. This retrospective look is important to help us identify areas where we can improve management techniques and where we should focus our future research efforts to best benefit horse owners and breeders. As such, it’s critical that breeding farms send their aborted foals to a veterinary diagnostic laboratory, even if the cause of abortion appears obvious.

Approximately 50% of the abortions evaluated were deemed noninfectious. Of these, most are not likely to be management related with the exception of twin pregnancies; however, twins did not comprise a large percentage of the abortions submitted. This is likely due to better management techniques, namely identification and reduction of twin pregnancies early in gestation, but also likely reflects the failure of owners to submit abortions with an obvious cause to the diagnostic laboratory. While this is understandable, it also makes it difficult to accurately measure the frequency of these losses.

Infectious abortions comprised the other 50% of submitted abortions, with placentitis representing the majority of these cases. Unfortunately, we know little about what predisposes a mare to develop placentitis, and we still have trouble with early, accurate, and specific diagnosis. Even so, there are steps that owners can take to aid in early diagnosis, including endocrine monitoring; regular ultrasound evaluation of the placenta; and daily checks for premature mammary gland development, premature lactation, and purulent (pus) vulvar discharge. If anything out of the ordinary is noted, a veterinarian should be called to examine the mare and start treatment if indicated.

As placentitis comprises the majority of the infectious abortions seen, the laboratory of Dr. Barry Ball (DVM, PhD, Dipl. ACT,) at the UK Gluck Equine Research Center has been focusing on better understanding the causes and progression of placentitis. By utilizing state-of-the-art techniques to look at changing gene expression, we have identified several potential targets which we believe will function as diagnostic aids and/or treatment options. Although more work is still needed to confirm our findings, we are optimistic that better options for dealing with placentitis will be available soon.

Again, I cannot stress enough the importance of sending all aborted foals, including fetal membranes and maternal serum, to a veterinary diagnostic laboratory. When breeders fail to submit abortions, it becomes more difficult to spot trends and, in turn, becomes more difficult to identify and respond to emerging threats. It’s easy to justify only submitting abortions without an obvious cause; however, the overall health of the equine breeding industry relies on the submission of every abortion, every time.

CONTACT—Shavahn Loux, PhD—Shavahn.Loux@uky.edu—859/257-4757—UK Gluck Equine Research Center, Lexington

This is an excerpt from Equine Disease Quarterly, funded by underwriters at Lloyd’s, London.