Oorsig/Review
Enzootic abortion of small ruminants
Prof. Leon Prozesky
Introduction
Losses due to reproductive failure, including
abortions, have a significant financial impact
on the profitability of stock farming. While it
is not unusual for some ewes to abort, flock
abortion rates more than (2-3 %) percent are
usually considered problematic and farmers are
encouraged to seek professional advice from their
veterinarians to establish a definitive diagnosis.
It is often not possible to identify the primary
cause of abortions and the international success
rate for this is approximately 30%. However,
by excluding the most important infectious
and where possible non-infectious causes, the
expenses incurred are justified. Reasons for the
low success rate are amongst others
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The event responsible for the abortions
occurred days/weeks /months earlier
Usually no gross foetus lesions
Advanced foetal autolysis
Incorrect samples, particularly absence of
placental tissue
Other causes than infectious diseases
The chances to identify the cause of the abortions
are significantly improved if a complete foetus
or preferably foetuses with placental tissue is
submitted to a well- equipped laboratory with
experienced staff.
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Fig 1. Necropsies conducted on aborted foetuses during a Rift
Valley Fever outbreak
In South Africa, the most common infectious
causes of sheep abortion are enzootic abortion
caused by Chlamydia abortus, Rift Valley
fever, Wesselsbron disease, Brucellosis and
Campylobacter spp. (vibriosis). Less common
causes include Bluetongue, Coxiella and
Salmonellosis. There are indications that the
incidence of enzootic abortion in small stock is
increasing in South Africa, for amongst other
reasons, non vaccination of livestock or the poor
protection of vaccines against local strains of C.
abortus.