Worm infections caused by soil-transmitted helminths differ from insect-, water- and food-borne helminthiases chiefly by the direct development of most of their agents. Having been passed out with the stool, their eggs or larvae develop on the ground or in its surface layers to the infective stage, either remaining in their shell, being swallowed and causing infection (Ascaris lumbricoides, Trichuris trichiura, for example), or entering man percutaneously as a free larva (e.g. hookworms).
KeywordsIncome Sewage Manure Straw Alkalinity
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