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 • • • • • 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. 4 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.