Effect of mass chemotherapy for filariasis control on soil-transmitted helminth infection in Western Province of Sri Lanka

Abstract

In July 2006, Sri Lanka completed five rounds of annual mass drug administration (MDA) with diethylcarbamazine citrate and albendazole as part of its national programme for elimination of lymphatic filariasis. Albendazole is also highly effective against soil-transmitted helminths (STH). This study was carried out to assess the impact of repeated annual MDA on STH infections in the Western Province of Sri Lanka, an area that is co-endemic for lymphatic filariasis and STH. A total of 17 schools in the Western Province were selected because they were included in a national survey of the health of school children in Grade 5 in 2003, when one round of MDA had been completed. Faecal samples were obtained again in 2006 (after five rounds of MDA), from one randomly selected class of Grade 5 students in the same schools. In both surveys, faecal samples were examined using the modified Kato-Katz technique. The prevalence and intensity of roundworm, whipworm and hookworm infections in 2003 and 2006 were compared using chi-square or Z-test for a difference between two percentages. Faecal samples from 255 children were examined in 2003; 448 were examined in 2006. Roundworm prevalence was marginally lower in 2006 (4.0%) than in 2003 (4.7%), as was hookworm (0.2% vs 0.4%) whereas whipworm prevalence was higher (13.8% vs 9.4%). Mean egg counts for all three infections were marginally higher in 2006. However, none of these differences were statistically significant. Compliance with MDA in 2006, as reported by the school children examined, was only 59%. These results indicate that four annual roundsof MDA with diethylcarbamazine and citrate and albendazole had virtually no impact on STH infections in the study area. It is likely that inclusion of of albendazole in MDA for lymphatic filariasis does not have much impact on STH infections in areas of low endemicity, unless very high coverage rates are achieved.