The nematodes are non segmented helminths and have bilateral symmetry.
They possess a complete digestive tract with oral and anal openings.
They have separate sexes the male being smaller than the female.
They range from a few millimetres to over a meter in length.
Nematodes have 5 stages in their life cycle, 4 larval stages and the adult. The third larval stage is usually the infective stage.
Nematode infections are found in both temperate and Tropical climates.
World Health Organisation estimates that 1.5 billion people carry intestinal nematode infections.
The most common nematodes to parasitise man are: