A nematode parasite, called Trichinella spiralis is found to occur in pigs, bears, horses, rodents and humans. It is the causative agent of a disease known as trichinosis. In humans, Trichinella spiralis is the smallest identified nematode parasite. The size of male in length ranges in between 1.4mm to 1.6mm while the size of female is double as compared to the size of the males. The anterior side of the body is more slender than the posterior side. In females, hatching of the larvae occurs at the anterior side while the posterior side contains the developing eggs.On the other hand, Ascaris lumbricoides, Ancylostoma duodenale and Enterobius vermicularis are endoparasites which lay eggs.