What is the cause of Swimmers Itch?
Several species of parasites known as blood flukes (all in the genus Schistosoma) are known to cause swimmers itch. The adult parasites live in the bloodstream of a host animal, which may be a bird, fish, turtle or muskrat. The adults produce eggs which are released from the host and are subsequently ingested by snails. A free-swimming larva later emerges from the intermediate-host snail looking for a suitable host animal. If it encounters one, it burrows through the animals skin and enters its bloodstream, completing the life cycle. If the larva encounters a human, however, it attempts to invade but is unable to get further than penetration of the skin. The human immune response rapidly kills the fluke, which releases an allergenic substance that causes the characteristic rash.
