Infection with Ascaris lumbricoides often causes no symptoms. Infections with a large number of worms may cause abdominal pain or intestinal obstruction. Adults feed on the contents of the small intestine and in heavy infections this may compound problems in malnourished individuals (especially children).
Migration of larvae may cause localized
reactions in various organs. Penetration of the larvae from capillaries
into the lungs can lead to Loeffler's pneumonia, in which pools of blood
and dead epithelial cells clog air spaces in the lungs. Resulting
bacterial infections can be fatal.