Page 477 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

452 CHAPTER 2

VetBooks.ir ABORTION

Abortion in the mare is defined as expulsion of the
fetus and its membranes before 300 days of gesta- 2.61
tion (Figs. 2.61–2.63). Expulsion after 300 days is
usually termed a stillbirth. The overall incidence of
abortion varies widely according to surveys, but has
been quoted as between 5% and 15%. The causes of
abortion can be divided initially into non-infectious,
infectious and unknown. There is some dispute in
the literature as to the incidence of these different
aetiologies. Non-infectious causes are usually the
most common (up to 70%), with infectious causes
varying between 15% and 45%. Up to 50% of abor-
tions may be undiagnosed. The majority of abortions
are sporadic, but in some cases infectious causes can Fig. 2.61 Fresh aborted fetus with multiple
lead to disastrous epidemics for a stud farm. It is abnormalities, including the mandible, and small size.
essential to establish the individual aetiology of each
abortion case by a rapid and thorough examination
of the aborted fetus and fetal membranes, using a 2.62
competent diagnostic laboratory. A thorough step-
wise investigation must be performed and immedi-
ate biosecurity measures implemented to prevent
possible spread and contamination. Until proven
otherwise, every aborted mare should be treated
as potentially infectious, as in the case of abortion
caused by EHV-1. Management of an abortion
should follow the guidelines outlined in the coun-
try or region’s disease-control programme (e.g. the
Horserace Betting Levy Board’s Code of Practice in
the UK, http://codes.hblb.org.uk).
In general:
Fig. 2.62 Fetal abortion due to excessive umbilical
cord length and torsion causing umbilical vessel
• Aborted mares and the aborted material should thrombi to develop, leading to fetal death and
be immediately isolated from other mares. abortion.
• All in-contact mares should be examined and
held in isolation until the cause of the abortion is
ascertained. 2.63
• A full history of the mare, its management and
vaccination record should be taken with a view
to establishing any causative factor.
• A post-mortem examination should be carried
out on the fetus and placental membranes
or arrangements should be made to send the
material to a diagnostic laboratory.

The clinical signs of abortion vary with different Fig. 2.63 A grossly normal fetal abortion must still
causes, but in some cases the mare may be found to be investigated fully, but often no cause is identified.