Ascaris lumbricoides

Intestinal Roundworm


Rev 09/23/2022

  Classification Biology and Ecology
Morphology and Anatomy Life Cycle
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Class:    Chromadorea
SubClass: Chromadoria
Order:   Rhabditida
Superfamily: Ascaridoidea
Family:  Ascarididae
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Morphology and Anatomy:

round-wormsA tangled mass of Ascaris worms

Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:



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Economic Importance:



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Intestinal roundworm


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Life Cycle

Adult hookworms (Ancylostoma duodenale and Necator americanus) parasitize the upper part of the human small intestine, whereas Ascaris lumbricoides parasitize the entire small intestine and adult Trichuris trichiura live in the large intestine, especially the caecum

The parasites can live for several years in the human gastrointestinal tract. After mating, each adult female produces thousands of eggs per day which leave the body in the feces.

Ecophysiological Parameters:

For Ecophysiological Parameters for this species, click If species level data are not available, click for genus level parameters


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Contact with soil contaminated with eggs or larvae of nematode parasites is a common form of transmission that results in human infection. The nematodes can live for years as adults in the human intestinal tract. Soil becomes contaminated by fecal material of infected humans and other animal hosts.

More than a billion people are infected with at least one species.  The most important nematode infections of the human gastrointestinal tract are the intestinal roundworm (Ascaris lumbricoides), whipworm (Trichuris trichiura), and hookworm (Necator americanus or Ancylostoma duodenale).

It is common for a single individual, especially a child living in a less developed country, to be chronically infected with all three of the nematode parasites, which results in malnutrition, stunted growth stunting, retarded intellectual development, and cognitive and educational deficiencies.


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Bethony, J., Brooker, S., Albonico, M., Geiger, S.M., Loukas, A., Diemert, D., Hotez, P.J.  2006. Soil-transmitted helminth infections: ascariasis, trichuriasis, and hookworm. The Lancet 9521:1521-1532.


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