Inactivation of Pathogens in Ecological Sanitation latrines in Malawi: An Observational Follow up Study

Introduction
In 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 the 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 the 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.

Results
Average concentrations of all pathogens investigated reduced over a 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 the concentration of helminths. The type of latrine and location were not significant predictors of helminth 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 the Malawi context. A storage period of one year or more is recommended.