A 13-year retrospective study of equine abortions in Canada.

Objective: The purpose of this study was to identify the most common causes of equine abortion in Canada, and to compare findings to similar reports from other countries.

Animal: Equine.

Procedure: Necropsy reports from 901 equine abortion cases were acquired from provincial veterinary diagnostic laboratories across Canada. The final diagnosis was classified into basic abortion causes (infectious, non-infectious, unknown) and into primary and secondary categories for analysis.

Results: Non-infectious causes of abortion were the most frequently identified in Canada, with fetoplacental causes, including umbilical cord torsion or placental insufficiency, being the most common primary diagnosis category. and were the bacterial species most often identified as causing infectious abortions, whereas equine herpesvirus-1 was implicated in all viral abortions identified.

Conclusion: The high rate of non-infectious causes of abortion was similar to previous studies conducted in the United Kingdom. This finding was somewhat dissimilar to the USA, which had higher rates of infectious abortions, despite Canada's geographic proximity to the USA. The reason for variations among countries in equine abortion causes is unknown.

Clinical Relevance: The large number of fetoplacental-related abortions identified in this study emphasized the need for submission of both the fetus and placenta, if possible, to increase the probability of a diagnosis. In addition, the high rate of unidentified diagnoses suggests a need for further study into both non-infectious and infectious causes of equine abortion, including potential development of new diagnostic tests or markers.