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VIII.13 - Ascariasis

from Part VIII - Major Human Diseases Past and Present

Published online by Cambridge University Press:  28 March 2008

Kenneth F. Kiple
Affiliation:
Bowling Green State University, Ohio
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Summary

The giant intestinal roundworm, Ascaris lumbricoides, is a very common parasite with a worldwide distribution. The adult worms are 15 to 35 cm (6 to 14 inches) long and reside in the lumen of the small intestine. Sometimes, however, they are passed in the feces and, if vomited into the oral cavity, may exit from the host’s mouth or nostrils; thus they have been known to medical observers for millennia. Female worms produce up to 200,000 fertilized eggs daily, which are passed in the feces. Eggs incubate in the soil for at least 2 to 3 weeks to produce an infective larval stage within them. The eggs are very resistant to chemicals, desiccation, and extreme temperatures, but they mature or “embryonate” most rapidly in warm, moist, shady conditions in clay soils. People become infected by eating embryonated eggs in food or water contaminated with feces; or, in the case of toddlers, infection occurs by direct ingestion of eggs with dirt. Poor rural sanitation and the use of human feces for fertilizer obviously favor transmission. Mature eggs hatch in the small intestine, and the larvae then undergo a remarkable series of migrations in the host. They penetrate the intestinal wall and are carried in blood or lymph vessels to the liver and heart, and then the lungs. Here they break out into the air sacs, develop, and molt for about 3 weeks, and then climb up the trachea to the throat, where they are subsequently swallowed to establish themselves as adults in the small intestine.

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Publisher: Cambridge University Press
Print publication year: 1993

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References

Jeffery, G. M., et al. 1963. Study of intestinal helminth infections in a coastal South Carolina area. Public Health Reports 78.Google Scholar
Kean, B. H., Mott, Kenneth E., and Russell, Adair J., eds. 1978. Tropical medicine and parasitology: Classic investigations, Vol. II, 346–59. Ithaca and London.Google Scholar
Latham, L., Latham, M., and Basta, S. S.. 1977. The nutritional and economic implications of ascaris infection in Kenya. World Bank Staff Working Paper No. 277 (September). Washington, D.C..Google Scholar
Pawlowski, Z. S. 1984. Strategies for the control of ascariasis. Annales de la Société Beige de Médecine Tropicale 64.Google ScholarPubMed
Stoll, N. R. 1947. This wormy world. Journal of Parasitology 33.Google ScholarPubMed
,World Health Organization. Parasitic Diseases Programme. 1986. Major parasitic infections: A global review. World Health Statistics Quarterly 39.

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  • Ascariasis
  • Edited by Kenneth F. Kiple, Bowling Green State University, Ohio
  • Book: The Cambridge World History of Human Disease
  • Online publication: 28 March 2008
  • Chapter DOI: https://doi.org/10.1017/CHOL9780521332866.075
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  • Ascariasis
  • Edited by Kenneth F. Kiple, Bowling Green State University, Ohio
  • Book: The Cambridge World History of Human Disease
  • Online publication: 28 March 2008
  • Chapter DOI: https://doi.org/10.1017/CHOL9780521332866.075
Available formats
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  • Ascariasis
  • Edited by Kenneth F. Kiple, Bowling Green State University, Ohio
  • Book: The Cambridge World History of Human Disease
  • Online publication: 28 March 2008
  • Chapter DOI: https://doi.org/10.1017/CHOL9780521332866.075
Available formats
×