Ascaris Worms: Life Cycle & Pictures

Instructor: Danielle Haak

Danielle has a PhD in Natural Resource Sciences and a MSc in Biological Sciences

Ascaris worms are intestinal parasites that can infect the human intestinal tracts, resulting in an infection called ascariasis. Read this lesson to learn about these worms and how humans become infected.

What Are Ascaris Worms?

Ascaris worms are a type of intestinal parasites that can infect humans. In fact, the Center for Disease Control (CDC) has estimated that as many as 1.2 billion people are infected with Ascaris worms worldwide, mainly in tropical regions of developing countries. This makes it the most common intestinal parasitic worm in the world! Once a person is infected, the infection is called Ascariasis. It's amazing to think that as much as 1/7 of the world's population has these worms living in their intestines!

Ascariasis is not a fun infection, at least when there are symptoms (which can include abdominal pain, intestinal blockages, and severe coughing), but the purpose of this lesson is to learn more about the worm and its life cycle. So let's dive in!

Ascaris Life Cycle

Ascaris worms are nematodes (another word for roundworms) that need a host to complete their life cycle; the host may be a human but can be other animals as well. Humans become infected and become hosts by ingesting food or water that is contaminated with Ascaris eggs. Once in the body, the eggs hatch into larvae and start burrowing into the mucus lining of the intestines. They pass through the lining and enter the blood stream, where they then travel to the lungs. Larvae spend around two weeks in the lungs maturing before they make their way out of the lungs and into the throat. When they get to the throat, they are usually swallowed and make their way back to the intestines when they finish maturing into adults.

Adult females are capable of producing up to 240,000 eggs. And this isn't in their entire lifetime. This is every single day! The adult female releases her eggs, most of which are then expelled from the body in the fecal material. Some eggs remain in the body, hatch, and proceed through their life cycle. If someone ingests food or water contaminated with eggs, they become infected and enable the worms to continue their life cycle. Once the worms reach maturity, they live between one and two years.

A diagram of the worm life cycle, including the role of the human host. (From the CDC)

So to briefly review: humans unintentionally swallow eggs which hatch into larvae once in the intestines. The larvae move from the intestines to the lungs, where they continue to mature, and then they make their way to the throat so they can be swallowed and returned to the intestines and reach maturity. At maturity, they begin producing and releasing vast quantities of eggs.

Now that we understand the life cycle, let's take a look at some pictures. Yes, they might be a little gross.

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