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    Ascaris

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

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    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]

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    Last updated: October 13, 2016

    Citation

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    TY - ELEC T1 - Ascaris ID - 540034 A1 - Spacek,Lisa,M.D., Ph.D. Y1 - 2016/10/13/ BT - Johns Hopkins ABX Guide UR - https://www.hopkinsguides.com/hopkins/view/Johns_Hopkins_ABX_Guide/540034/all/Ascaris PB - The Johns Hopkins University DB - Johns Hopkins Guide DP - Unbound Medicine ER -