- 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.
- 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.
- Transmission: hand to mouth.
- 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.