Ascaris
MICROBIOLOGY
- Ascaris lumbricoides is the largest intestinal nematode (nemato from Greek, thread) or roundworm, a human pathogen and helminth or worm-like parasite.
- Soil-transmitted helminths (STH) also include Strongyloides stercoralis, Trichuris trichiura (whipworm), Ancylostoma duodenale (hookworm)and Necator americanus (hookworm).[2]
- A. lumbricoides ova are excreted in stool, are hardy, can sustain freezing, and live up to 6 years in moist soil. Eggs are rounded and may have a thick shell with an external mammillated (bumpy) layer or may appear smooth and lack the mammilated layer.[11]
- Ova develop in warm, humid soil over a period of 3 weeks before becoming infectious; thus, they are known as ’soil-transmitted’ helminths.
- Life cycle- Humans ingest infective ova that hatch and release larvae. Larvae invade the intestinal mucosa and travel from the portal to systemic circulation to the lungs in about 4 days.
- Larvae penetrate alveoli, ascend the trachea, and are reingested, then mature in the intestines and live for 10 to 24 months.[11]
- Adult worms can live in the lumen of the small intestine for up to 2 years; adult female worms can produce 200,000 ova/day.
Epidemiology:
- Ascariasis is endemic in warm, humid areas, especially where human excreta is used as fertilizer or contaminated wastewater for irrigation.[3]
- Infection occurs most commonly in younger individuals but affects all ages.
- Heavy infections can cause malnutrition, especially in children.[5]
- Transmission is from ingesting soil, food, or water contaminated with eggs.
- Ascariasis due to A. suum is a swine-associated zoonosis.
There's more to see -- the rest of this topic is available only to subscribers.
Last updated: July 13, 2024
Citation
Spacek, Lisa A. "Ascaris." Johns Hopkins ABX Guide, The Johns Hopkins University, 2024. 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; 2024. https://peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540034/all/Ascaris. Accessed November 10, 2024.
Spacek, L. A. (2024). 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; 2024. [cited 2024 November 10]. 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
TY - ELEC
T1 - Ascaris
ID - 540034
A1 - Spacek,Lisa,M.D., Ph.D.
Y1 - 2024/07/13/
BT - Johns Hopkins ABX Guide
UR - https://peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540034/all/Ascaris
PB - The Johns Hopkins University
DB - Pediatrics Central
DP - Unbound Medicine
ER -