Ascariasis is infection with the parasitic roundworm Ascaris lumbricoides.

Ascariasis is caused by consuming food or drink contaminated with roundworm eggs. Ascariasis is the most common intestinal worm infection. It is found in association with poor personal hygiene, poor sanitation, and in places where human feces are used as fertilizer.

Once consumed, the eggs hatch and release immature roundworms called larvae within the intestine. The larvae then move through the bloodstream to the lungs, exit up through the large airways of the lungs, and are swallowed back into the stomach and intestines.

During movement through the lungs the larvae may produce an uncommon form of pneumonia called eosinophilic pneumonia. Once they are back in the intestines, the larvae mature into adult roundworms. Adult worms live in the intestine where they lay eggs that are present in feces.

It is estimated that 1 billion people are infected worldwide. Ascariasis occurs in people of all ages, though children are affected more severely than adults.

Most of the time, there are no symptoms. If there are symptoms, they may include:

• Bloody sputum
• Cough
• Low-grade fever
• Passing worms in stool
• Shortness of breath
• Skin rash
• Stomach pain
• Vomiting worms
• Wheezing
• Worms exiting through the nose or mouth

The infected person may show signs of malnutrition. Tests to diagnose this condition include:

• Abdominal x-ray
• Complete blood count
• Stool ova and parasites exam

Treatment includes medications that paralyze or kill intestinal parasitic worms, such as albendazole or mebendazole. If there is a blockage of the intestine caused by a large number of worms, endoscopy or, rarely, surgery may be needed.

Most people recover from symptoms of the infection, even without treatment, although they may continue to carry the worms in their body.

Complications may be caused by adult worms that move to certain organs or multiply and cause a blockage in the intestine.