IntroductionIn Malawi, EcoSan sludge from ecological sanitation (EcoSan) latrines has been found to contain helminths,
Salmonella
and
E. coli
above WHO recommended
levels making sludge unsuitable for direct handling and use on food crops. This research investigated survival of pathogens in EcoSan sludge with time
after sealing the pit.
Method
An observational longitudinal follow-up study was conducted where EcoSan latrines were followed from August 2015 to July 2016 in Blantyre and
Chikwawa in Southern Malawi. The study enrolled 51 latrines in total with 35 latrines [13 fossa alterna (FAs) and 22 urine diverting dry latrines (UDDLs)]
remaining at the end of study. Samples were collected five times from each latrine and examined for helminths,
Salmonella and E. coli in the laboratory.
Poisson regression was employed to assess factors that significantly contribute to pathogen die off at p<0.05.
ResultsAverage concentrations of all pathogens investigated reduced over 12-month follow-up period except for
Salmonella which increased. A. lumbricoides,
increased to 2.3 viable eggs during the second sampling and decreased to 0.4 viable eggs per gram after 12 months of follow-up. Time was the only
consistent predictor for concentration of helminths. Type of latrine and location were not significant predictors of helminths concentration (p>0.05).
However,
Salmonella and
E. coli colonies were significantly higher in UDDLs (Blantyre) than FAs (Chikwawa) (p<0.05).
Conclusion
Pathogen concentration was highest after recommended six months of storage posing a public health risk to those handling and using it for agriculture
purposes. It is therefore recommended that the current guidelines be reviewed to suit Malawi context. A storage period of one year or more is recommended.
