Invasion of skin by Schistosoma cercariae.

Schistosomiasis caused by Schistosoma spp. remains a major global health problem affecting >200 million people. The success of these parasites is a result of their adaptation to several different environments, including snail tissue, fresh water and mammalian blood; and their ability to switch between these environments rapidly. The initial step in infection of the human host involves penetration of the human skin by the aquatic form of Schistosoma, the cercaria. This aspect of host invasion is remarkable because no wounds or insect vectors are required and cercariae can penetrate through intact skin rapidly. The mechanisms of host finding and invasion represent fascinating and complex biological phenomenon, which are discussed here.