Ascaris

Lisa A. Spacek, M.D., Ph.D.
Ascaris is a topic covered in the Johns Hopkins ABX Guide.

To view the entire topic, please or purchase a subscription.

Official website of the Johns Hopkins Antibiotic (ABX), HIV, Diabetes, and Psychiatry Guides, powered by Unbound Medicine. Johns Hopkins Guide App for iOS, iPhone, iPad, and Android included. Explore these free sample topics:

Johns Hopkins Guides

-- The first section of this topic is shown below --

MICROBIOLOGY

  • Ascaris lumbricoides: largest intestinal nematode (roundworm) that is a human pathogen.
    • Soil-transmitted helminth
      • Ova develop on warm, humid soil (about 3 wks) before becoming infective.
      • Adult worms live in lumen of small intestine (up to 2 yrs).
      • Ova excreted in stool.
  • Life cycle: humans ingest infective ova that hatch and release larvae. Larvae invade intestinal mucosa and travel from portal to systemic circulation to lungs in about 4 days. Larvae penetrate through alveoli, ascend the trachea, and are reingested, then mature in intestines and live for 10 to 24 months.[3]
  • Ova are hardy. They can sustain freezing and live up to 6 years in moist soil. Adult female worms can produce 200,000 ova/day.

Epidemiology:

  • Endemic in warm, humid areas especially where human excreta is used as fertilizer, contaminated wastewater is used for irrigation, or geophagy (deliberate/regular consumption of soil) is practiced.
  • Infection most common in young, but affects all ages.
    • Heavy infections can cause malnutrition.[6]
  • Transmission: hand to mouth.
  • Ascariasis due to A. suum is a swine-associated zoonosis.[7]

-- To view the remaining sections of this topic, please or purchase a subscription --

Last updated: October 13, 2016