Schistosoma Mansoni Infection: Intestinal Schistosomiasis

Abstract : Man is infected by working in infested water containing living cercariae. The cercariae penetrate the skin or mucous membrane, develop into schistosomules and travel through the peripheral venules to the pulmonary vessels, from where they enter the general circulation. Those reaching the portal venous system develop into male and female adult worms in 6-12 weeks; most adult S. mansoni then migrate to their final habitat in the tributaries of the inferior mesenteric veins. Most eggs laid in the small venules around the colon pass into the tissues, but some are eliminated in the stools. Eggs which are passed in the stools hatch immediately in fresh water and liberate free- swimming miracidia, that penetrate a specific snail host (genus Biomphalaria) within 24 hours. Cercariae developed in 4-6 weeks and are passed into the water where they remain infective for 2-3 days. The cycle is then repeated when man enters fresh water containing the cercariae and becomes infected.