SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH Vol 31 No. 2 June 2000 388 INTRODUCTION Hundreds of millions of people in the world mainly in developing countries, even today, are infected with soil-transmitted helminths (STH) with a significant amount of morbidity and mortality (Chan et al, 1994; WHO, 1997). In some areas, nearly 100% of people are infected (van-Niekerk et al, 1979; Reily, 1980; Rai and Gurung, 1986). One estimate has put 120 million to 215 million cases of morbidity due to Ascaris lumbricoides, 90 million to 130 million due to hookworm and 60 million to 100 million due to Trichuris trichiura infections (Chan et al, 1994) with an annual death numbers of 60,000, 65,000 and 10,000, respectively (WHO, 1997). In addition, helminths of animal origin also pose a potential zoonotic health prob- lem. Elsewhere in the developing world, soil con- tamination rate reportedly range from 20% to 64% (Pezzani et al, 1996; Uga et al, 1997). A relatively stable soil contamination rate with Ascaris eggs throughout the year attributed to open and indis- criminate defecation has also been reported (Peng et al, 1996). Contamination of soil with parasite eggs, thus, constitute a most important risk factor for STH as well as for zoonotic helminth infec- tions. In the industrialized countries, where STH prevalence is very low, investigators have focused their study on zoonotic helminth parasites such as Toxocara eggs contamination of sandpits in public parks (Uga et al, 1989; 1995a; Uga, 1993) includ- ing the measures to prevent their contamination and extermination of the eggs already present in the sandpits (Uga and Kataoka, 1995b). Nepal, located in South Asia, is one of the least developed countries with nearly 22 million population living largely on agricultural subsis- tence. The varied geotopography with diverse climatic condition can be divided into three regions namely, the Mountains, the Hills, and the Terai (plains). The population densities and life style vary according to the region and ethnic groups, respectively. Approximately 70% of the health problems in Nepal are infections. Of them, STH infection alone is most important (Reily, 1980; Estevez et al, 1983; Rai and Gurung, 1986; Rai et al, 1994; 1995) and has been found to signifi- cantly affect on the nutritional status of Nepalese (Rai et al, 1998; 2000). However, the soil con- tamination with STH eggs of both human and animal origin has not been well investigated. Since the soil contamination with A. lumbricoides eggs CONTAMINATION OF SOIL WITH HELMINTH PARASITE EGGS IN NEPAL Shiba Kumar Rai 1 , Shoji Uga 2 , Kazuo Ono 3 , Ganesh Rai 4 and Takeo Matsumura 5 1 Department of Medical Zoology, Faculty of Medicine and 2 Department of Medical Technology, Faculty of Health Science, Kobe University School of Medicine, Kobe, Japan; 3 Division of Microbiology, Hyogo Prefectural Institute of Public Health, Kobe, Japan; 4 Department of Pathology, Birendra Police Hospital, Kathmandu, Nepal; 5 Department of Domestic Science, Minatogawa Women’s College, Sanda, Japan Abstract. Contamination of soil with helminth eggs in Kathmandu Valley (n=122) and outside of Valley (n=34) in Nepal was investigated with the use of centrifugal floatation technique using sucrose solution (sp gr 1.200). The overall soil contamination rate was 36.5% (57/156). The prevalence was uniform in Kathmandu Valley (36.9%) and outside of the valley (35.3%). A mean of six helminth eggs per sample were detected out of which more than half were embryonated (potentially infective). In Kathmandu Valley, soil contamination rate was higher (48.3%) during wet season compared with that observed in dry season (33.3%) but without significant difference (p>0.05). Multiple species of helminth eggs were detected in 22.8% of total positive samples (n=57). Altogether five species of nematoda (Ascaris lumbricoides, Toxo- cara sp, Trichuris trichiura, Capillaria sp and Trichostrongylus sp) and two species of cestoda (Hymenol- epis nana and H. diminuta) were recovered. A. lumbricoides was predominant in Kathmandu Valley while Trichostrongylus was the commonest one in outside of valley. Correspondence: Shoji Uga, Department of Medical Technology, Faculty of Health Science, Kobe University School of Medicine, Tomogaoka 7-10-2, Suma-ku, Kobe 654-01, Japan. Tel/Fax: 0081-78-796-4548, 341-7451; E-mail: ugas@ams. kobe-u.ac.jp