THE PATHOGENESIS OF MANSON'S SCHISTOSOMIASIS

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Abstract
A prolonged, detailed study of 400 cases of acute and chronic Manson''s schistosomiasis indicates that the earliest phase is mainly dominated by a hyper sensitivity state of abrupt onset. The acute disease is of variable duration and severity, generally mild, and at times subclinical. In most instances it is mistaken for a mild enteritis, attributed mainly to dietary indiscretions, and at times it is mistaken for a salmonellosis. The explosive disease is observed only among those who are heavily infected and poorly nourished, and who have defective body defenses. After a variable asymptomatic incubation period (21 to 42 days), allergic manifestations appear with oviposition. The continuous production of allergens by the ova and/or adult parasite may serve to perpetuate the hypersensitivity reaction. The local reaction produced by the eggs and/or adult parasites leads to variable degrees of vascular changes in the liver, intestine and lungs. Actual destruction of tissue and foreign body reaction of allergic origin may also occur. Although most of the cases are mild and remain undiagnosed, extensive pathologic alterations may occur with heavy infestations when accompanied by a poor dietary. In some instances the picture may be dominated by portal hypertension with fragile esophageal varices and congestive splenomegaly with signs of hypersplenism. Cirrhosis of the liver is mainly governed by poor nutrition, but is undoubtedly influenced by the parasitosis. In some cases the prominent feature is chronic cor pulmonale, with pulmonary hypertension from arteriolitis (egg embolization and superimposed pneumonitis). The severity of the clinical picture is chiefly influenced by socio-economic factors, and by the adequacy of the defensive mechanism of the host, rather than by the parasitosis per se. Thus, death with but not from Manson''s schistosomiasis is the general rule. Since there are no adequate anti-schistosomal agents, it seems that curability depends mainly on the development of immunity.