GEO-HELMINTH INFECTIONS IN SRI LANKA Vol 32 No. 1 March 2001 23 INTRODUCTION The World Health Organization estimates that more than one billion of the world’s population is chronically infected with soil transmitted helminths and these infections are associated with poverty and poor living conditions (WHO, 1998). It is widely recognized that school children carry the heaviest burden of morbidity due to intestinal helminthiasis and schistosomiasis infection (WHO, 1998). Apart from the morbidity associated with acute infections, the burden of chronic parasitic infections may affect physical fitness (Stephenson, 1990), cognitive performance (Connolly and Kvalsvig, 1992), nutritional status and growth (Stephenson, 1994), and school attendance (Nokes and Bundy, 1993) of school age children. Other studies conducted throughout Sri Lanka have shown that prevalence rates of intestinal parasitoses vary widely with time and location because they are influenced by environmental, social and cultural factors and the economic conditions in a given community. Atukorale and Lanerolle (1999) have reported the prevalence of geo-helminth infections in adolescent schoolgirls to be 2.2% in a rural area of Sri Lanka and 16.7% in an urban area. In another study conducted in the plantation sector of Sri Lanka, 89.7% of the children aged 3-12 years of age were infected with at least one type of soil transmitted nematodes (Sorenson et al, 1994). The objective of our investigation was to study the prevalence of geo-helminth infections in a rural area of Sri Lanka. MATERIALS AND METHODS The study population comprised 349 GEO-HELMINTH INFECTIONS IN A RURAL AREA OF SRI LANKA SD Fernando 1 , H Goonethilleke 1 , KH Weerasena 1 , ND Kuruppuarachchi 2 , D Tilakaratne 2 , D de Silva 3 , AR Wickremasinghe 4 1 Department of Parasitology, Faculty of Medicine, Colombo, Sri Lanka; 2 Department of Parasitology, Faculty of Medical Sciences, University of Sri Jayawardenepura, Nugegoda; 3 Department of Psychological Medicine, Faculty of Medicine, Colombo; 4 Department of Community Medicine and Family Medicine, Faculty of Medical Sciences, University of Sri Jayewardenepura, Nugegoda, Sri Lanka Abstract. School children carry the heaviest burden of morbidity due to intestinal helminth infection. The objective of this investigation was to study geo-helminth infections in 349 school children aged 6 to 13 years living in a rural area of Sri Lanka. Stool samples were examined by direct saline smear in an initial survey to determine the prevalence of intestinal parasitic infections and thereafter the children were followed up over a two year period with cross sectional surveys of stool samples being carried out at yearly intervals. Following collection of a stool sample, all the subjects were treated with mebendazole 500 mg as a single dose. Weights and heights were measured using standardized procedures. 2 ml of venous blood were collected from each subject under aseptic conditions to determine hematological indices. The prevalence of geo- helminth infections was low, and the prevalence declined during the two-year period from 5.4% in 1997 to 2.2% in 1998 and 2.0% in 1999 following yearly mass anti-helminth treatment. The incidence density was 0.021 cases per child year. The reduction in the prevalence from the baseline to the second survey is probably due to the reduction of the reservoir of infection among children as a result of mass treatment at baseline. The prevalence of infection during the second and third surveys were almost the same probably due to infections originating from other segments of the untreated population.