Schistosoma Mansoni in the Cecum (9 of 9)

The geographic distribution and pathophysiology of schistosomiasis reflect the unique life cycle of these parasites. Schistosomes infect particular species of susceptible freshwater snails in endemic areas. The infected snails release cercariae, which are fork-tailed free -swimming larvae approximately 1 mm in length. The cercariae survive in freshwater up to 48 hours, during which time they must attach to human skin or to that of another susceptible host mammal or die. Cercariae attach to human hosts utilizing oral and ventral suckers. They then migrate through intact skin to dermal veins and, over the next several days, to the pulmonary vasculature. During this migration, the cercariae metamorphose, shedding tails and outer glycocalyces while developing double-lipid-bilayer teguments that are highly resistant to host immune responses.