Microbial source tracking of faecal pollution in the water sources of Taita-Taveta County: Relationship between faecal pollution specific to livestock or humans and human related public health risks

Mitigation of faecal pollution is still a challenge in sub-Saharan areas where the few water resources are shared directly by human, livestock and wildlife. This makes it difficult to identify the most worrisome sources of faecal contamination as it requires the distinction of different pollutants. Different methods of Microbial Source Tracking (MST) that target different host specific Bacteroides have been developed to identify host-specific faecal contamination in different water sources. Mwatate, a sub-county of Taita-Taveta County found in south eastern part of Kenya with different climatic zones and land uses was chosen for the study. Twenty-six sampling sites were analysed from different water sources for three sampling campaigns experiencing different rainfall intensities. E. coli, Bacteroides and MST markers targeting human, ruminant, and bovine-specific Bacteroides were analysed. Physical chemical parameters were also analysed with an aim to understand the sources and variations of faecal contaminant and related health risks in this region. The significant difference observed in the concentration of E. coli, Bacteroides and MST markers at different elevations was highly attributed to the different agricultural systems and the rainfall season at the time of sampling. Ruminants contributed the highest concentrations of faecal bacteria however this varied with different agricultural systems. Human contribution to faecal pollution was highest in densely populated areas and least in wildlife conservancies. This variability contributed highly to the risk of infection from a particular source. The probability of contracting a disease from either human or ruminate was the same in areas dominated by both livestock and human. Therefore Land use and landscape are very important aspects that should be considered in the mitigation of faecal contamination in such regions