Seropositivity and diagnostic challenges of bovine brucellosis in Limpopo and Free State (2013–2022)

Brucellosis, a contagious zoonotic bacterial infection affecting livestock and wildlife, is primarily caused by Brucella abortus, globally. However, in South Africa, the true prevalence of bovine brucellosis remains unknown because of a lack of epidemiological data. Therefore, this study used diagnostic data to evaluate and determine the seropositivity of bovine brucellosis based on Rose Bengal test (RBT) screening and confirmation with complement fixation test (CFT) in Limpopo and Free State provinces between 2013 and 2022. The use and limitations of this data were also evaluated based on the bovine brucellosis scheme in South Africa. The study revealed the overall seropositivity of 4.2% (n = 8980/212 440) for bovine brucellosis based on RBT and CFT in series. In Limpopo province, the brucellosis seropositivity was slightly higher at 4.3% (n = 7488/173 011) compared to 3.8% (n = 1492/39 429) in Free State province. Analysis of brucellosis distribution over the study period indicated significant variation (p 0.001) both between and within the provinces. Notably, the highest prevalence in Limpopo occurred during 2013-2017, whereas in Free State, peak prevalence was observed in 2013 and 2016. Challenges preventing an accurate reflection of the brucellosis seropositivity in these provinces for the period include a lack of data on vaccination history and herd status of the samples submitted, as well as the inability to match the CFT results from different laboratories, because some laboratories are only accredited to perform the RBT.Contribution: Insights gained from retrospective studies such as this study can play crucial roles in shaping effective control and preventative measures against bovine brucellosis. Given the challenges in obtaining confirmatory test results, we suggest that brucellosis tests be conducted at a single central laboratory or that the government provides a central database where all laboratories can enter their data. Furthermore, information submitted to the laboratories must make herd and vaccine history compulsory for sample submission to ensure more accurate data.