Ascariasis is a debilitating human disease caused by the roundworm Ascaris lumbricoides; other species of Ascaris are parasitic in domestic animals (see Nematode). Perhaps as many as one fourth of the world's people are infected, but ascariasis is particularly prevalent in tropical regions and in areas of poor hygeine. Infection occurs through ingestion of food contaminated with fecal matter containing Ascaris eggs. The larvae hatch, burrow through the intestine, reach the lungs, and finally migrate up the respiratory tract. From there they are then reswallowed and mature in the intestine, growing up to 30cm (12in) in length and anchoring themselves to the intestinal wall.
Infections are usually accompanied by inflammation, fever, and diarrhea, and serious problems may develop if the worms migrate to other parts of the body.
