What is the role of these birds and mammals in the life cycle of the parasites?
When cercariae contact a suitable bird or mammal, they penetrate through the skin, migrate through various organs such as the liver and lungs, and then reside in the blood vessels of the host, particularly those surrounding the intestine. The parasites develop to adulthood there even though they are extremely small and thin. The female worms (no bigger than a single hair of a paint brush) then lay eggs that work their way into the host’s intestine. When the host defecates into the water, the eggs of the parasites in the feces hatch into the next stage, the miracidium. Like a cercaria, the miracidium is nonfeeding and can only swim in the water for up to a day, depending on the water temperature.
