Blood fluke (Schistosoma mansoni egg)

Adult worms live in the mesenteric venules of humans and other mammals; eggs are passed in feces and develop in freshwater snails (Biomphalaria species) as intermediate hosts. Found in tropical and subtropical regions, particularly Africa, the Middle East, and parts of South America.

Adult worms feed on host blood in the venules. The larval stages within the snail feed on snail tissues.

The life cycle involves humans (definitive host) and freshwater snails (intermediate host). Eggs are released in human feces, hatch in fresh water to release miracidia which infect snails. Inside snails, miracidia develop into sporocysts, then cercariae. Cercariae are released from snails and penetrate human skin, transform into schistosomulae, and migrate to blood vessels where they mature into adult worms. Adults mate and produce eggs, completing the cycle.

Risk: Schistosoma mansoni is a parasitic flatworm that causes intestinal schistosomiasis (also known as bilharzia). Infection can lead to symptoms such as abdominal pain, diarrhea, and blood in the stool. Chronic infection can result in liver fibrosis, portal hypertension, and other severe pathologies. There are no known benefits to humans or the ecosystem from this parasite.