schistosome

Schistosome refers to a genus of parasitic flatworms belonging to the phylum Platyhelminthes and the class Trematoda. These are commonly known as blood flukes. They are the causative agents of schistosomiasis, a debilitating tropical disease that affects millions of people worldwide. The life cycle of schistosomes is complex and involves two hosts: a freshwater snail and a vertebrate, typically humans.

The adult schistosomes live in the blood vessels of their vertebrate host. Females burrow into small venules, while males hold them in their gynecophoral canal. They reproduce sexually within the host, and the fertilized eggs are either shed in the host's feces or urine, or they become trapped in host tissues. If the eggs reach freshwater, they hatch into free-swimming larvae called miracidia.

The miracidia penetrate specific species of freshwater snails, where they undergo asexual reproduction and develop into cercariae. These cercariae are fork-tailed larvae that are released from the snail into the water. When human skin comes into contact with contaminated freshwater, the cercariae can penetrate the skin and enter the bloodstream. They then migrate to their specific blood vessel location within the human body, where they mature into adult worms and the cycle continues. Different species of schistosomes infect different blood vessels and cause varying clinical manifestations of schistosomiasis, impacting organs such as the liver, intestines, and bladder.