Effect of repeated mass chemotherapy for filariasis control on soil-transmitted helminth infections in Sri Lanka.

BACKGROUND: In July 2006 Sri Lanka completed 5 rounds of annual mass drug administration (MDA) with diethylcarbamazine citrate (DEC) and albendazole as part of its national programme for elimination of lymphatic filariasis (LF). Albendazole is highly effective against soil-transmitted helminths (STH). This study was carried out to assess the effect of repeated annual MDA on STH infections in the Western Province of Sri Lanka, an area co-endemic for LF and STH. METHODS: Faecal samples were obtained (during August-September 2006), from grade 5 students in 17 schools in the Western Province that were included in a national survey of schoolchildren's health in 2003, and examined using the modified Kato-Katz technique. The prevalence and intensity of roundworm, whipworm and hookworm infections in 2003 and 2006 were compared. RRESULTS: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%). These differences as well as that between the geometric mean egg counts were not statistically significant. Compliance with MDA in 2006, as reported by the schoolchildren examined, was only 59%. CCONCLUSIONS:Four annual rounds of MDA with DEC and albendazole had virtually no effect on STH infections in the study area.

Microfilarial periodicity of Wuchereria bancrofti and man landing periodicity of the vector Culex quinquefasciatus say in Matara, Sri Lanka.

OBJECTIVE: To compare the microfilarial periodicity of Wuchereria bancrofti, with the man landing periodicity of the vector Culex quinquefasciatus in Matara, Sri Lanka. DESIGN: Periodicity was estimated using a statistical method. 60 microliters finger prick (FP) blood was smeared from a single subject every 2 hours for 24 hours of the day to make 12 samples. Smears were stained with Giemsa and the microfilariae (mff) counted. Man landing catches of mosquitoes were made inside a bedroom of a house in the same area on a sleeping volunteer during the night, between 18.00 and 06.00 hours. Each hourly catch was placed in separate paper cups. Hourly C. quinquefasciatus taken were counted. SUBJECTS: 10 asymptomatic microfilaria (mf) carriers. RESULTS: The individual mf peaks in the 10 carriers varied from 22.00 to 04.00 hours. Using the statistical method the parameter k showing the mf peak hour was 1.19 estimating the peak mf density at 01.11 hours. The influence of different times of blood collection on false negatives among the very low density carriers was estimated by the periodicity curve. It would be desirable to collect blood during the estimated time interval when the mf count was 80% of the peak count, between 21.55 and 04.27 hours in Matara. The results of 25 all-night mosquito landing catches gave a peak activity hours of k as 7.78, corresponding to 01.47 hours. CONCLUSION: The close agreement in the peak hours of mf density and vector activity suggests a perfect adaptation between parasite and vector for optimum transmission.