Ascaris Roundworms

Ascaris Roundworms

Mitsuki Okino, Journalist

⚠There is a gross picture

Ascaris is an intestinal parasite of humans. It is the most common human worm infection. The larvae and adult worms live in the small intestine and can cause intestinal disease.


Ascaris lives in the intestine and Ascaris eggs are passed in the feces of infected people. If the infected person defecates outside (near bushes, in a garden, or fields), or if the feces of an infected person are used as fertilizer, then eggs are deposited in the soil. They can then mature into a form that is infecticous.

Ascariasis is caused by ingesting infective eggs. This can happen when hands or fingers that have dirt contaminated on them are put in the mouth or by consuming vegetables or fruits that have not been carefully cooked, washed or peeled.  


Infection occurs worldwide in warm and humid climates, where sanitation and hygiene are poor, including in temperate zones during warmer months. People in these areas are at risk if soil contaminated with human feces enters their mouths or if they eat vegetables or fruit that have not been carefully washed, peeled or cooked. Luckily, Ascariasis is now uncommon in the United States.


People infected with Ascaris often show no symptoms. If symptoms do occur, they can be light and include abdominal discomfort. Heavy infections can cause intestinal blockage and impair growth in children. Other symptoms such as cough are due to migration of the worms through the body.


Health care providers can diagnose Ascariasis by taking a stool sample and using a microscope to look for the presence of eggs. Some people notice infection when a worm is passed in their stool or is coughed up. If this happens, bring in the worm specimen to your health care provider for diagnosis.