What is Ascariasis? - Symptoms & Pathophysiology

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

This lesson goes over a pretty disgusting but rare (in the United States) parasitic infection known as ascariasis. Find out the pathophysiology as well as the signs and symptoms behind this condition.

What is Ascariasis?

Ascarids are parasitic worms from the order Ascaridida. You might hear them being referred to simply as 'roundworms.' However, they are only one type of roundworm. Roundworm is the general and common term for any type of parasitic worm from the phylum Nematoda which includes, among others, the ascarids.

Thus, ascariasis is the pathological state ('-iasis') caused by ascarids. Specifically, in humans, it refers to the disease caused by parasites such as Ascaris lumbricoides. Let's find out more about the pathophysiology of this condition as well as some of its signs and symptoms.

Ascaris lumbricoides
Ascaris lumbricoides


Environmental Cycle

For this lesson, we're going to use little Timmy as a good (but unfortunate) example of ascariasis. Little Timmy is a 5 year old boy. His mom just took him to play on a nearby river bank on a nice, warm day. What little Timmy doesn't know is that not far away there was a massive sewage spill about three weeks ago. That sewage spill contained fertilized Ascaris eggs that were defecated out by an infected person.

See, A. lumbricoides worms live inside the small intestine of a person. A female worm can produce around 200,000 eggs a day! These eggs are then often fertilized by nearby male worms and passed in a person's feces into the environment. When a fertilized egg finds itself in ideal conditions (warm, moist, and shaded soil), it'll become infectious in as little as 5 days although it can take several weeks.

And what do little kids do? They put dirty hands and soil in their mouth like it's Nutella or something. Timmy might be in trouble. This time, that soil contained infectious Ascaris eggs. But let's not pick on Timmy for a second. People can be exposed when someone infected defecates outside or infected human feces is used in fertilizer. As a result, infectious eggs can then make their way onto produce that people eat. If this produce is not washed properly, even adults can be infected.

Internal Cycle

Anyway, once Timmy swallows those eggs, they eventually reach his small intestine. Here, the eggs hatch and little baby worms come out. But they don't just sit there. They burrow into the intestines and actually make it into the bloodstream. Once they are inside the bloodstream, they are then carried to the liver and then the lungs. Here, in the lungs, the little worms mature. Once they mature enough, they actually burrow through the lung tissue and climb their way up Timmy's airways.

Timmy's airways, being irritated by this, force Timmy to cough the worms up in order to get rid of them. But what do many people do with stuff they cough up? They swallow it, right? Well, little Timmy does the same. He swallows the still developing worms, which then make it back to the small intestine, where they develop into adult worms in about 65 days. Here, they make more eggs, which are defecated out, and so the cycle continues.

These worms live for 1-2 years inside the person's body but they do not multiply within the person! In other words, fertilized eggs will not hatch and turn into adult worms without first being passed out in the stool. Thus, if a person is infested with adult worms for more than 2 years, they are somehow being re-exposed to infectious eggs in their environment over and over again.

A large tangled mass of worms inside this person

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