Some Considerations on the Pathogenesis of Human Ascaris and Hookworm Infections: a Review.

Human ascariasis produces a wide variety of symptoms : lassitude, fever, anorexia, dyspepsia, morbid appetite (geophagia), nausea, vomiting, diarrhoea, constipation, abdominal pain, coughing, headache, disorder of consciousness, spasm, asthma, nasal pruritis, visual disturbance, pollakiuria, urticarial rash, etc., which affect nearly all the organs and tissues of the digestive, respiratory, circulatory and excretory systems, and occasionally cause systemic complaints. These symptoms may be attributed to a toxic substance excreted or secreted by worms in the host, a secondary infection with pyogenic bacteria and viruses, mechanical stimulation due to worm movement and allergic reactions of the host to the worms. Extensive studies on the so-called "Ascaris toxin" were made by Koizumi et al.(1944) which unfortunately fell far short of demonstrating satisfactorily that the worm substances and their culture media were involved in the development of ascariasis symptoms. In recent years, the secondary infection has been the subject of a few reports but many points still remain to be clarified. As is known, clinically symptomless cases of Ascaris infection occur frequently. Some are also described as suddenly presenting marked and serious symptoms, these being exclusively attributed to migration of adult Ascaris in ectopic foci. On the other hand, a growing interest has recently been shown in Japan in the immunological study of parasitic helminths and helminthiasis. Some workers have attempted to elucidate the allergic mechanisms causing manifestations of helminthiasis by comparing them with human allergic reactions to worms. Two series of investigations will be discussed below. One deals with damage caused by adult Ascaris migrating into ectopic foci in the human abdomen (the "surgical type" of ascariasis, described by Maki, 1958), the other with gastroduodenal ascariasis considered as being one of the allergic manifestations of various forms of ascariasis (Matsumura, 1958). These investigations were chosen because the former is concerned with the type of ascariasis producing acute and severe symptoms and requiring immediate surgical intervention, and the latter because it relates to a new etiology. a) Pathological and clinical aspects of ascariasis due to migration of adult worms, especially in the abdomen