FILARIAL WORM

any of a group of parasitic worms of the class Nematoda (phylum Aschelminthes) that usually require two hosts, an arthropod (the intermediate host) and another animal (the primary host), to complete the life cycle. The larval phase occurs within the body of a biting insect. The mature phase occurs in the body of an animal bitten by the insect. The female worm produces large numbers of microscopic, active embryos called microfilariae that pass into the bloodstream of the primary host. These then enter the body of an insect as the insect bites the infected animal. The microfilariae grow into larvae in the insect's muscles, then are passed to the primary host when the insect bites an animal, and the cycle repeats. In mammals filarial worms cause a group of infectious disorders known collectively as filariasis.