Prevalence of brucellosis in cattle slaughtered in a local abattoir in Hammanskraal, South Africa

Abstract

Background: Brucellosis is a contagious zoonotic bacterial disease of worldwide distribution and remains endemic in most low- and middle-income countries (LMICs), including South Africa. The current bovine brucellosis scheme in South Africa predominantly makes use of serological tests for diagnosis which lack 100% accuracy if the gold standard test (culturing) is not performed. Abattoirs can provide information on notifiable and zoonotic disease and can play a pivotal role in disease surveillance and monitoring. This study aimed at demonstrating the usefulness of abattoir surveillance for detection of Brucella spp. using serological, molecular and bacteriological methods. Methods: Serum and tissue samples (liver, spleen and lymph nodes) were collected from slaughter cattle at a local abattoir in Hammanskraal, Gauteng Province in September 2018. A total of 122 serum samples were screened for Brucella antibodies while molecular and bacteriological methods were used to detect Brucella spp. from tissue samples of serological positive animals. Results: The Rose Bengal test (RBT) revealed a seroprevalence of 22.1% (27/122, 95% CI = 15.1-30.5) and iELISA confirmed a seroprevalence of 9.0% (11/122, 95%CI = 4.6-15.6). Genus- specific 16S-23S rRNA interspacer region (ITS) - PCR detected Brucella DNA in 9 of the seropositive tissue samples of animals. From the 9 ITS-PCR positive animals, 44.4% (4/9) Brucella bacteria were isolated and confirmed to species level using the AMOS PCR assay. AMOS-PCR characterized the four Brucella isolates as B. abortus with one mixed culture consisting of B. abortus and B. melitensis in cattle. Conclusion: The findings conclude that abattoirs are facilities that can provide invaluable information on disease surveillance and that the gold standard procedure can be performed on collected tissue samples that yield in a more accurate diagnosis.