Purpose: The purpose of this study was to investigate the public health risks associated with the consumption of producer-distributor (PD) bovine bulk milk and estimate the resulting burden of illness that may occur under the current production and marketing conditions in South Africa.
Methods: A total of 258 PD bulk milk samples were collected from purchase points in 8 different geographical regions around South Africa. Shiga toxin-producing E. coli (STEC) were isolated and identified using molecular techniques. Data for the risk models was obtained from the recently completed studies in South Africa. Inputs for the models was complemented with data from published and unpublished literature. Hazard characterization was based on dose-response from literature. A probabilistic exposure model with Monte Carlo simulation was developed taking into account prior collected prevalence data of STEC in raw and pasteurized PD bulk milk, and survey information from farms, retail and households. Sensitivity analysis for the assessment of the uncertainty and variability associated with the model was also carried out
Results: Prevalence of STEC in milk samples was 10.9 % (n=258). The study revealed that even though STEC is eliminated by pasteurization, it appears that the risk of infection persists due to post-contamination at retail stage. The baseline study quantifies the risk of STEC from informally marketed producer-distributor milk and estimates the incidence rates in SA.
Significance: Information obtained can be used to formulate risk-based mitigation strategies and policies in informal markets.