Abstract
This study assessed the pathogenicity of source waters in the Nwanedi River catchment surface waters including rivers as well as its related non perennial tributaries (storm run-off) by determining the presence of diarrhoeagenic Escherichia coli pathotypes namely Enteropathogenic Escherichia coli, Enterotoxigenic Escherichia coli, Enterohaemorrhagic Escherichia coli, Enteroaggregative Escherichia coli and Enteroinvasive Escherichia coli.
The faecal pollution levels in the surface waters was assessed by measuring indicator Escherichia coli numbers in water samples at various sampling sites carried from its land-based faecal sources into the receiving surface water bodies.
Sampling sites were selected to represent the human, livestock as well as wildlife sources of faecal generation and the possible infection risk posed to domestic, full body contact, agriculture uses as well as for abstraction intended for drinking were determined by comparing the Escherichia coli numbers with the guidelines summarised in Table 2.6: Chapter 2.
A total of 199 proposed water samples were collected and analysed by the Miniaturised Most Probable Numbers method using 96-well micro-titre plates to enumerate Escherichia coli from the water samples.
Twenty eight of 199 water samples were also analysed with a multiplex polymerase chain reaction using specific primers for the identification of diarrhoeagenic Escherichia coli related virulent genes namely – Mdh for commensal E. coli, Eagg and pCVD for Enteroaggregative E. coli, ST1 and LT1 for Enterotoxigenic E. coli, Stx1 and Stx2 for Enterohaemorrhaegic E. coli, EaeA for Enteropathogenic E. coli and Enterohaemorrhagic E. coli, Ial for Enteroinvasive E. coli. River water samples were directly filtered and 100-mℓ of filtered water samples were extracted while 1-mℓ pre-cultured Escherichia coli from storm run-off samples were extracted for use in the multiplex polymerase chain reaction.
Because of the villages along the Nwanedi River catchment, Enteropathogenic E. coli followed by Enterotoxigenic E. coli was suspected to be the dominant diarrhoeagenic Escherichia coli. Contrary to this Enteroaggregative E. coli (54%) was dominant followed by Enterohaemorrhaegic E. coli (29%), Enteroinvasive E. coli (7%), Enteropathogenic E. coli (4%) and Enterotoxigenic E. coli (4%) respectively, in the surface water samples. The Escherichia coli numbers were significantly higher in storm run-off compared to the river water samples.
Literature report Enteroaggregative E. coli to be associated with diarrhoea in HIV/AIDS patients, to whom its dominance in the surface water samples could pose serious infection risk to the Nwanedi River catchment communities, more especially the young, elderly and the immuno-compromised at
the period of sampling if the waters are used untreated. The high Escherichia coli numbers could possibly be the results of continuous faecal contamination into the water sources and the rain storm events carrying faecal materials from land surface.
Results show that Nwanedi River catchment waters harbour pathogens indicated by diarrhoeagenic Escherichia coli occurrence as well as commensal Escherichia coli numbers , which suggest the possible infection risk posed to the consumers if the waters are used untreated.
Prof. P. Jagals
Dr. T.G. Barnard