الفهرس 
AcknowledgmentOnly 14 pages are availabe for public view
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Abstract
P arasitology today is not only ruled by morphological and systematic investigations as before, but attention has been focussed upon the ecology of parasitic cycles, the population biology of parasites and the behavioral aspects of parasite transmission. Each individual parasite is highly influenced by a group of ecological factors which control its survival and transmission. These factors differ from one parasite to the other according to the stages of development and life cycle of each parasite. Generally speaking, these factors should be looked upon from three aspects, human aspect, socioeconomic aspect and environmental aspect. The most vulnerable group for parasitic diseases are school children. Their increased activities, their lack of inhibition and self control, and their poor hygienic habits make them the most exposed group to parasitic infections. Schools are the major socializing environment at which children spend a long time of their lives. Therefore, healthy school sanitary conditions are very essential for protecting children against infections generally and parasitic infections specifically. Parasites are not solely influenced by different ecological factors, but also their intermediate hosts. Snails as an intermediate host should be focussed upon, because their presence and survival means the survival of the dependant parasites. The present work was performed to determine the prevalence of some parasitic infections among elementary school children, to detect the larval stages of intestinal parasites infesting the soil and to study the snail intermediate host of trematode parasites present in the canals and drains of the studied village. Two schools in El-Ola El Sharkia village, were the subject of this study, a primary school and a preparatory one. One class from each grade was randomly selected. Demographic and socioeconomic data were collected from each child in the selected class. Also data about the schools sanitary conditions were collected. A single fresh stool sample was obtained from each child and examined using the following methods: 1- Filter paper strip culture technique. 2- Formol-ether sedimentation technique (two drops were examined). A single fresh urine sample was obtained from each child and examined using the sedimentation technique. Fifty soil samples were collected over the four seasons of the year and were examined using the following methods: 1- Baermann’s technique for larval diagnosis. 2- Sugar flotation technique for diagnosis of ova. 3- Two soil samples were analysed in Laboratories of Faculty of Agriculture. Snail samples were collected monthly from the canals and drains of the village, they were examined using the following techniques: 1- Shedding technique. 2- Dissecting technique. The results obtained are summarized in the following: • Out of 335 school children, 222 (66.3