Johns Hopkins ABX Guide
Ascaris
MICROBIOLOGY
- Ascaris lumbricoides: largest intestinal nematode (roundworm) that is a human pathogen.
- A soil-transmitted helminth, other STHs are Strongyloides stercoralis, Trichuris trichiura (whipworm), Ancylostoma duodenale and Necator americanus (hookworms).
- Ova develop on warm, humid soil over a period of 3 wks before becoming infective.
- Adult worms live in the lumen of the small intestine for up to 2 yrs.
- Ova are excreted in stool, are hardy, and can sustain freezing, and live up to 6 years in moist soil.
- Adult female worms can produce 200,000 ova/day.
- 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.[2]
Epidemiology:
- Endemic in warm, humid areas especially where human excreta is used as fertilizer or contaminated wastewater is used for irrigation.
- Infection most common in the young, but affects all ages.
- Heavy infections can cause malnutrition.[8]
- Transmission: hand to mouth.
- Ascariasis due to A. suum is a swine-associated zoonosis.[9]
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Last updated: July 4, 2021
Citation
Spacek, Lisa A. "Ascaris." Johns Hopkins ABX Guide, The Johns Hopkins University, 2021. Pediatrics Central, peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540034/all/Ascaris.
Spacek LA. Ascaris. Johns Hopkins ABX Guide. The Johns Hopkins University; 2021. https://peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540034/all/Ascaris. Accessed December 6, 2023.
Spacek, L. A. (2021). Ascaris. In Johns Hopkins ABX Guide. The Johns Hopkins University. https://peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540034/all/Ascaris
Spacek LA. Ascaris [Internet]. In: Johns Hopkins ABX Guide. The Johns Hopkins University; 2021. [cited 2023 December 06]. Available from: https://peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540034/all/Ascaris.
* Article titles in AMA citation format should be in sentence-case
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T1 - Ascaris
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BT - Johns Hopkins ABX Guide
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PB - The Johns Hopkins University
DB - Pediatrics Central
DP - Unbound Medicine
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