[Gr. askaris, pinworm]
A genus of worms belonging to the family Ascaridae. They inhabit the intestines of vertebrates.

Ascaris lumbricoides

A species of Ascaris that lives in the human intestine; adults may grow to 12 in long. Eggs are passed with the feces and require at least 2 weeks' incubation in the soil before they become infective. After being swallowed, the eggs hatch in the intestinal tract, and the larvae enter the venous circulation and pass to the lungs. From there they migrate up the respiratory passages, are swallowed, and reach their site of continued residence, the jejunum. In a 1- to 2-year life span, the female is capable of producing 200,000 eggs a day. The eggs are passed with the feces, and a new cycle is started. Children up to the ages of 12 to 14 are likely to be infected. Intestinal obstruction may be a complication in children under 6 years of age.

Albendazole and mebendazole are the drugs most commonly used to treat infection with Ascaris.

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ASCARIS LUMBRICOIDES (A) Smaller male encircled by female, (B) Mass of worms removed from the intestine