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Helminth Infections
Schistosomiasis
Schistosomes are a group of worms known as blood flukes that live in the mesenteric blood vessels of humans. Two species are prevalent throughout sub-Saharan Africa, Schistosoma mansoni, and Schistosoma heamatobium, which live in the mesenteric veins of the intestine and urinary bladder respectively. The worms lay eggs which burrow through the tissues of the urinary bladder or intestine where they may cause considerable damage. Eggs are ultimately passed in the urine of feces, depending on species. When passed into water eggs hatch releasing a free-swimming larval form that penetrates the snail intermediate host. Within the snail the parasites develop into the infective stage to humans, known as cercaria. The cercariae, that are shed by infected snails, enter the human host by penetrating the skin. Worldwide about 200 million people are infected with schistosomes, which cause 20,000 deaths per year. In addition, infection with schistosomes often leads to decreased absorption of nutrients in the intestine, leading to reduced physical and mental development.
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