Abstract:
Abortions in cattle, sheep and goats represent important economic losses in the agricultural industry. Determining causes of abortions is important for control efforts, but can be challenging.
This study investigated detection methods for and significance of bacteria and fungi as agents of abortion in domestic ruminants in South Africa. Retrospective data was collected by searches of case reports (2006-2016) of participating pathology and bacteriology laboratories. During the prospective study (2017-2019), samples were analysed by a combination of conventional bacteriology methods. Quantitative real-time PCR assays for detection of the Chlamydiales, Chlamydia abortus, Chlamydia pecorum, Parachlamydia acanthamoeba and Waddlia chondrophila were created by combining primers and probes selected from literature. These assays were optimized and employed to analyse samples from 25 cases, with placentitis and/or pneumonia lesions, selected from the prospective study.
The retrospective study reported 288 cases from six provinces. Diagnostic rate was 35.1%. The prospective study reported 135 cases from six provinces. Diagnostic rate was 42.2%. Brucella species were most commonly isolated in both the retrospective and prospective studies at 7.3% and 7.4% of cases, respectively. The qPCR assays detected Chlamydiales in 60% of cases with placentitis and/or pneumonia. Chlamydia abortus, P. acanthamoeba and W. chondrophila were detected in bovine; and C. pecorum and W. chondrophila in ovine and caprine cases. Chlamydiales were detected in three previously inconclusive cases. Identification was improved from genus to species level (C. pecorum).
In conclusion, retrospective laboratory records yielded valuable passive surveillance data. Submission of placenta was an important factor in successful diagnosis. The most effective combination of conventional culture methods was aerobic culture together with selective Brucella, Campylobacter and fungal culture. This combination lead to improvement of the diagnostic rate in comparison with the retrospective study. Brucella abortus was the most common cause of bovine abortion over 12 years in the retrospective and prospective studies. Trueperella pyogenes was the second most common. Real-Time qPCR assays improved detection of Chlamydiales and differentiation to species level. The first detection of P. acanthamoeba and W. chondrophila in abortion cases in South Africa was reported indicating a potential role in abortions in this country.
