Ascariasis

Ascariasis is an infection in your intestines caused by a roundworm called Ascaris lumbricoides (A. lumbricoides). Like other parasites, these worms use the body of a host (like a human) to mature into egg-laying adults. The more the worms thrive, the more harm they can cause the host.

A. lumbricoides is a kind of soil-transmitted helminth (STH). The worms living in someone’s gut lay eggs that exit through their stool (poop). If an infected person poops outside, the eggs transform into their infective form a few weeks later. Accidental ingestion of A. lumbricoides eggs in contaminated soil can create a new infection in that person. Eggs that contaminate food or water can also be accidentally ingested since they’re microscopic. Municipal water filtration treatment won’t allow eggs to get into normal tap water.

Although ascariasis infection is rare in the United States, it’s common in parts of the world with poor sanitation (for example, in places without widespread, easy access to toilets). In these areas, people are more likely to come into contact with contaminated soil, food or water.

What are the types of ascariasis?

The human roundworm (A. lumbricoides) is responsible for most cases of ascariasis. But the pig roundworm Ascaris suum (A. suum) can also cause human infection. You’re more at risk of an infection if you raise pigs or use pig manure for fertilizer.

How common is ascariasis?

Ascariasis is one of the most common human parasitic infections, affecting over 1 billion people worldwide. It’s the most common type of intestinal worm infection. Most infections affect children in tropical and subtropical parts of the world with poor sanitation.