Vasculature hepatic veins

Once schistosome cercariae penetrate the skin of their host, they can remain in this environment as schistosomula for up to 5 days before entering the vasculature and beginning their migration to the lungs and, subsequently, the hepatic portal vein (Wilson, 1987). During this journey, which may take 3 weeks (Wilson, 1987), and thereafter, schistosome parasites must contend with an assortment of host immune factors. Yet, as is well known, these parasites are able to complete the journey to their final destination and live for years. Research has shown that schistosomes have adapted a variety of mechanisms that enable them to evade a strong and potentially lethal host immune response. 

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