Ascaris lumbricoides is a roundworm that lives in the small intestine of humans. The parasite is found primarily in tropical and subtropical regions of the world where sanitation is poor. Ascaris is the most common human parasitic infection in the world, and affects about 4 million people in the U.S., according to Merck.com. The World Health Organization estimates that Ascaris infection causes about 60,000 deaths worldwide each year.
General Symptoms
Infection with the Ascaris roundworm, called ascariasis, may cause no noticeable symptoms, according to the Mayo Clinic. Symptoms become apparent with heavy parasite infection or when migrating worms affect the lungs, according to the CDC's Division of Parasitic Diseases. Sometimes a worm may be passed, usually in the stool.
Lung Symptoms
After the eggs hatch in the small intestine, the young worms move through the intestinal wall to the liver, heart and lungs, according to Merck.com. Once in the lungs, the young worms lodge in the tiny blood vessels of the air sacs. They also migrate up the airway to the throat. This movement of the worms in and through the lungs causes wheezing and coughing. Sometimes a person may cough up blood, says Merck.com. After the worms travel to the lungs, symptoms may be similar to asthma or pneumonia, according to the Mayo Clinic.
Abdominal Symptoms
After the young worms have traveled through the lungs and up into the throat, they are swallowed and return to the small intestine where they mature and mate, according to Merck.com. Even a moderate infestation can cause symptoms of abdominal pain, nausea, vomiting and diarrhea, according to the Mayo Clinic. Occasionally, an adult worm can block the ducts of the gallbladder or pancreas, causing inflammation or disease of those organs, says Merck.com.
Symptoms of Severe Infestation
The presence of large numbers of worms can cause severe abdominal pain and vomiting, according to the Mayo Clinic. Fatigue and weight loss can occur. Obstruction of the intestine by large masses of worms occurs most commonly in infected children and can be fatal, according to Stanford University. A twisted intestine, a tear or hole in the intestine, or gangrene can occur. Infestation may cause malnutrition in children, with loss of appetite and decreased absorption of nutrients as contributing factors, according to Merck.com.
