Intestinal Nematodes

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Rhoanjayvee BS-Bio 4 September 24, 2012

Parasitology Lab Exercise:



To examine the morphology of the eggs, larva, and adult forms, and to study the life history, taxonomy, pathology, and epidemiology of some of the commonest intestinal nematodes infecting man


Nematodes are commonly known as roundworms. As their name implies, they have unsegmented cylindrical bodies, which are tapered are both ends and covered with cuticle. Unlike the platyhelminthes which have (or sometimes lack) incomplete digestive system, the roundworms are equipped with complete oral-to-anal alimentary canal. Sexes are separate, with females generally larger than males. Nematodes are medically important parasites of the intestines, skin, lymphatics, and other tissues. In the laboratory, we studied eight representative nematodes that parasitize human intestines. Although considered a muscular parasite, Trichinella spiralis is nevertheless included as it has an important albeit transitionary stage in the intestines. These eight roundworm species are taxonomically ranked as following:


Phylum Nematoda

Class Aphasmida

Family Trichinellidae Trichinella spiralis

Family Trichocephalidae Trichuris trichiura

Capillaria philippinensis

Class Phasmida

Family Strongyloididae Strongyloides stercoralis

Necator americanus

Ancylostoma duodenale

Family Oxyuridae Enterobius vermicularis

Family Ascaridae Ascaris lumbricoides

Trichuris trichiura

The whipworm is distributed worldwide, especially in area with poor sanitation and hygiene. Adults of both sexes are characterized by a slender anterior section and thickened posterior and resembling a whip. Male posterior end is tightly coiled. Female size ranges 3-5 cm while male is <4cm. The infective stage is embryonated egg (by ingestion). The eggs are eliminated with...