What is the life cycle of swimmers itch causing parasites?
The causative agent for swimmer’s itch is the larval, free-living and aquatic stage of a group of flatworms that are called schistosomes. Most species that cause swimmer’s itch use bird hosts for the adult parasite and aquatic snails as intermediate hosts for the larval stages. The life history of the dermatitis-producing worms is cyclic. Eggs released from the adult worms that reside in the blood vessels (usually veins around the intestine) of the bird host, make their way into the digestive tract of the bird and then pass out of the host with the feces. If the eggs are deposited in water, they will hatch within an hour if conditions are right. The miracidium, an aquatic stage, is free-swimming, but nonfeeding. It has enough energy to keep it moving for about a day. Once the miracidium comes in contact with the proper snail it will either penetrate into the snail via the integument or it may enter through its mouth. Within the snail, the miracidium will elongate to form a reproductive
