Evaluation of a sanitation programme using eggs of Ascaris lumbricoides in household yard soils as indicators

Soil samples were analysed for the presence of Ascaris lumbricoides eggs as indicators of environmental pollution in household yards in Maputo, Mozambique, with the objective of evaluating the impact of a programme for the promotion of improved latrine construction. The locations for soil sample collection were defined by a random grid on which household activities were mapped. In addition, parasitological examinations were carried out amongst household residents. No significant difference was found between the type of latrine in use and the presence of Ascaris eggs in the soil or human Ascaris infection. Households with at least one infected person appeared more likely to have Ascaris eggs in the yard. It was notable that egg counts around the latrines were only slightly greater than in other areas of the yard and less than those immediately in front of the dwelling. This is taken to indicate that faecal pollution of the household environment is due more to promiscuous defecation than to poor construction or maintenance of the latrines. The findings highlight the need to complement sanitation 'hardware' with the necessary health education 'software'. Ascaris eggs are useful indicators but robust standardized methods are needed for their extraction from household soils.