Nematodes: Roundworms

Abstract

Nematodes are cylindrical, or filariform in shape and bilaterally symmetrical. The adults vary greatly in size, from a few millimetres to a metre long. Male is generally smaller than female. The nematodes have separate sexes. Female nematodes may produce eggs (oviparous), larvae (viviparous), or lay eggs containing larvae, which immediately hatch out (ovoviviparous). Modes of infection are ingestion of infective eggs or encysted larvae in muscle. Eggs can also be inhaled and swallowed. Infection can occur via skin penetration by infective filariform larvae or transmitted by blood-sucking insects as seen in filarial worm infection.