Human trichostrongylosis and its relationship to ancylostomiasis in southern Iraq, with comments on world incidence

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Abstract
An investigation of the occurrence of helminthic intestinal parasites in the population of central and southern Iraq led to the discovery that human trichostrongylosis is relatively common in man along the banks of the Shatt-al-Arab and the lower course of the Tigris and Euphrates rivers. In the Basrah area the incidence is 25·4% and at Nasriyah 14·2% but it falls rapidly along the northward course of the rivers and is absent in the centre and north of the country. This is correlated with the occurrence of heavy shade cast by palm forest, high humidity due to the presence of perennial swamps, and the occurrence of grass and other carpet plants in the south; which jointly provide the conditions necessary for the development and survival of the free-living stages ofTrichostrongylus.Hookworm (Ancylostoma duodenale) is more evenly distributed over the area and is common farther north where conditions are more arid; owing to the fact that the free-living stages can develop under much drier conditions than those ofTrichostrongylus, probably mainly on moist defaecation sites near irrigation channels.The species ofTrichostrongylusinvolved is not known but is probablyT. colubriformiswhich is common locally in sheep and has been found in man at Abadan by Marsh (1949). Infection is presumably contracted by ingestion of greenstuff carrying infective juveniles.Since infections are light, symptoms minimal and treatment ineffective care should be taken to differentiate trichostrongylosis from ancylostomiasis in order that no unnecessary medication be undertaken.The world incidence of human trichostrongylosis is higher than was formerly believed. The available reports are reviewed, and it is concluded that not less than fifty million persons harbour this worm throughout the globe.