Testing household disinfectants for the inactivation of helminth eggs on surfaces and in spills during pit latrine emptying

Abstract

The lack of potable water, poor hygiene practices and inefficient sanitation systems in developing countries pose a risk to human health. Pit latrines aim to break the link between human faecal waste and human contact by serving as improved sanitation. The eThekwini Municipality has developed a programme that employs workers to empty pits every 3 to 5 years. This study aimed to find a cost-effective, easy way of disinfecting household surfaces and inactivating Ascaris eggs using household disinfectants, so that transmission of helminths is minimised when pits are emptied. Disinfectants tested in this study were based on sodium hypochlorite or carbolic acid. Experiments simulated inactivation of Ascaris eggs by wiping contaminated surfaces with disinfectants and by soaking small spills in disinfectants. Samples were processed using standard helminth egg enumeration methods for soil and sludge. Wiping of contaminated surfaces removed Ascaris eggs, facilitating egg transfer but not egg inactivation. Prolonged exposure to disinfectants, at concentrations of 50% and above, were required to inactivate eggs. Sodium hypochlorite–based disinfectants were the most successful for inactivation, whilst those based on carbolic acid were mostly ineffective. It is recommended that faecal sludge spills are soaked in a sodium hypochlorite–based disinfectant and contaminated surfaces be wiped with a sodium hypochlorite–based disinfectantsaturated cloth, which should then be soaked for 1 h in a similar disinfectant solution (50% dilution) to inactivate any eggs picked up on the cloth.

Keywords: Ascaris, carbolic acid, disinfectant, eggs, inactivation, pit latrine, sanitation, sodium hypochlorite