What is the infective stage of Schistosoma?

The infective stage of Schistosoma is the cercariae. These are free-swimming larvae that emerge from the snail intermediate host into freshwater environments. When humans come into contact with contaminated water, the cercariae penetrate the skin and enter the bloodstream, leading to infection.

Understanding the lifecycle of Schistosoma is key to recognizing why cercariae are significant. After the eggs are laid by adult worms in the human host, they hatch in water to release miracidia, which then infect snails to develop into cercariae. This crucial transition from snail to free-living stage represents the point at which the organism becomes capable of infecting a new host. Once again, it is the cercariae that serve as the infective form, highlighting their role in transmission of the disease.

The other stages mentioned, like metacercariae, are involved in different parasites (like trematodes) and do not pertain to the Schistosoma life cycle specifically. Meanwhile, adults refer to the mature worms that reside in the human host, while miracidia are only the initial stage that does not directly infect humans.