Ascaris lumbricoides

Large Intestinal Roundworm of Humans

Sep 26, 2007 Rosemary Drisdelle

Ascaris lumbricoides evolved with humans, and it lives in the intestines of millions of people. Large and active, it has inspired many tales and considerable folklore.

Ascaris lumbricoides is otherwise known as the large intestinal roundworm of humans. It looks a lot like a large earthworm, but the two are not related. The earthworm is an annelid; it lives in the soil, feeding on organic debris. A. lumbricoides is a parasitic nematode, or roundworm; adults are found only in the intestines of humans, feeding on intestinal contents as they flow past. If you were to compare the two very carefully, you would note that the earthworm has little tufts of bristles and its body is marked with many rings, as though it was built a slender ring at a time. The body of ascaris is smooth and hairless, and the worm has three lips at the mouth end, arranged like the leaves of a three leaf clover.

Ascaris lumbricoides worms have a reputation for wandering, and often do so if the body they are in-the host-is ill or taking certain medications. Adult roundworms sometimes spontaneously exit the host through the anus, mouth, or nose. They are found in the bathtub, toilet bowl, in diapers, or even on the pillow upon waking. Females can be well over a foot long; males are smaller. For many people, the appearance of a large worm is a traumatic experience, and no doubt the source of many tales about worms.

Misconceptions and myths about Ascaris lumbricoides

Because of it's frequent appearances, A. lumbricoides has been familar to people for thousands of years. Here are some commonly held, but incorrect, beliefs about ascaris:

• You can catch Ascaris lumbricoides from your dog or cat. False: the intestinal roundworms of dogs and cats are different species that are never found as worms in the human intestine. The large intestinal roundworm of pigs may be able to live in humans but this has not been proven. Ascaris infection is acquired when the host swallows worm eggs that have matured in warm moist soil after an infected person defecated on the ground.
• Putting a piece of bread or raw steak by a person's mouth will lure the worms out. False: ascaris worms do sometimes exit the mouth but they do not eat bread and steak. These animals are adapted to get nutrients by taking in liquid intestinal contents.
• Having ascaris worms will make you lose weight. False: a few worms in the intestine generally cause no obvious symptoms at all. Many worms may lead to nutritional deficiency, particularly in children, or bowel blockage due to worms forming balls and knots of many individuals.

Ascaris lumbricoides in history

People have known about A. lumbricoides for a long time. Since antiquity we have been trying to understand them, prevent them, and cure infections. Here are some interesting facts from the history of ascaris:

• Prior to about 1600, many people believed that ascaris was spontaneously generated in the intestine; in other words, that people actually produced the worms themselves.
• In both Europe and the Far East it was long believed that an ascaris worm entering the heart would cause sleep walking on moonlit nights and, sometimes, sudden death.
• Ascaris worms-ground, juiced, burned to ash, dried, or even partially decomposed-were used in ancient Chinese medicine to treat eye problems. They were used in many countries to treat worm infections, and in some cultures as an aphrodisiac.
• Ascaris lumbricoides eggs have been found in fossilized human feces all over the world. The oldest are thought to be nearly 30,000 years old.

Because of ascaris' potential to wander and do damage to internal organs, and because it is associated with malnutrition and learning problems in children, an ascaris infection should always be treated. If you suspect you have intestinal worms, see your doctor.

Related content:

Ascaris lumbricoides - Life Cycle

Read about other nematodes that infect humans:

Capillaria spp. - Tiny Worms

What is River Blindness

Other interesting articles about human infections are available in Microbiology

Sources:

Parasites and Parasitic Infections in Early Medicine and Science. Hoeppli, R. Singapore: University of Malaya Press, 1959.

Foundations of Parasitology 6th Ed. Roberts, Larry S. and John Janovy Jr. Boston: McGraw Hill, 2000.

The copyright of the article Ascaris lumbricoides in Microbiology is owned by Rosemary Drisdelle. Permission to republish Ascaris lumbricoides in print or online must be granted by the author in writing.

Ascaris lumbricoides adult

Ascaris lumbricoides egg

16 Comments

Comments

Sep 28, 2008 8:15 PM

Guest :

true not false: you can catch ascaris sp from your dog or cat.

Sep 29, 2008 5:09 AM

Rosemary Drisdelle :

There is a commonly held misconception that people catch roundworms from dogs and cats. Dogs and cats do become infected with intestinal roundworms that are very similar to A. lumbricoides but are entirely different species. If a human swallows eggs of a dog or cat roundworm (Usually Toxocara sp.) the eggs can hatch and migrating larvae can cause serious health problems, especially in children. These larvae do not mature to adult worms however - you cannot get intestinal worms of either Ascaris or Toxocara sp. from a dog or cat.

Jan 28, 2009 4:15 AM

Guest :

it also depends on the person's personal hygiene... if u are a "ready to eat" type person then their is a great possibilities in acquiring those said worm.. simple precaution is the best... Always wash hands before and after doing a certain activities.

Apr 21, 2009 5:01 PM

Guest :

it is possible to get other kinds of womrs from your dog or cat which is the reason why most sandboxes have covers now to keep the cats from using the sand box, but you CAN NOT get ascaris lumbricoides from dogs and cats

Apr 21, 2009 5:38 PM

Rosemary Drisdelle :

The main concerns with contaminated sandboxes are Toxocara sp. - an intestinal roundworm of dogs and cats that can infect people but does not result in intestinal worms in people (the larvae migrate to other parts of the body), and Toxoplasma gondii - which is not a worm (protozoan) but nevertheless can cause serious illness in some people. Dogs and cats, of course, carry other diseases that affect people and it's always wise to avoid contact with their feces.

Apr 28, 2009 7:41 AM

redangel58 :

How is this treated if pregnant and can it or the treament cause problems for mother and/or baby?

Apr 28, 2009 8:38 AM

Rosemary Drisdelle :

Some antiparasitic drugs are safe to use in pregnancy and some are not recommended. A pregnant woman who thinks she is infected with A. lumbricoides should see her medical doctor for confirmatory testing and treatment if indicated.

May 11, 2009 9:07 AM

Guest :

Rosemary, you indicated that there are treatments for pregnant woman with ascaris. Diagnosed 10 inch female roundworm. Midwife, doctor and infectious disease specialist are all offering different advice. What do you think? 6 months pregnant. What can be done now as opposed to waiting until after the birth? And is there any danger to the baby if the decision is to wait on treatment?

May 11, 2009 9:40 AM

Rosemary Drisdelle :

Sorry, I'm not a doctor and wouldn't dream of giving medical advice. Of the three medical professionals you mention, the infectious disease specialist is the one with the most knowledge and experience of both parasites and antiparasitic drugs.

May 11, 2009 1:41 PM

Guest :

Ok, that makes sense... thank you.
Can you offer any insight as to whether any remaining roundworms in her system could harm the unborn baby? (no one seems to know?)
Thanks!

May 12, 2009 4:07 AM

Rosemary Drisdelle :

Well these are definitely questions for the medical experts. I did a quick search of the literature and didn't find anything significant, which suggests, to me anyway, that it's not a big issue (given the number of people with ascaris in the tropics, its presence during pregnancy must be fairly common). To be fair, there's always some risk. On the other hand, new evidence suggests that there may also be some benefit (http://autoimmunedisease.suite101.com/article.cfm/parasites_and_the_hygien e_hypothesis). Our specialists don't have all the answers, but they are the most knowledgeable people we have at times like this. I'd follow medical advice. All the best.

Jul 12, 2009 11:49 AM

Guest :

Hi I recently became infected with this parasite. I spend a lot of time in the Cayman Islands. Do you think I could have acquired it there? Second question: I recently did a lot of pot planting and used my bare hands in the dirt. I think a lot of the packaged potting soil may be infected with fecal matter these days. Is it possible I could have gotten it that way? thanks.

Jul 13, 2009 4:10 AM

Rosemary Drisdelle :

Either one of those sources is a possibility, although I suspect the potting soil is less likely. Many commercial potting soils are sterilized. Always wash your hands after handling soil and wash vegetables thoroughly.

Keep in mind that it takes 2 - 3 months from the time you become infected before adult worms are producing eggs in your intestine. Assuming a diagnosis based on eggs in a stool specimen, you'd need to think about where you were 2 - 3 months prior, or longer.

Sep 4, 2009 10:16 AM

Guest :

Does anyone know does is spread easliy to other humans in the house ? I have two kids and one has it and i was wondering if I should be conerned if the other could cacht it?

Sep 5, 2009 10:57 AM

Rosemary Drisdelle :

Ascaris doesn't spread directly from one person to another because the eggs need time to mature in a warm moist environment. When more than one person in a family has the worms, it's not because they caught them from each other, but often because they've all been exposed to the same source of eggs.

Sep 11, 2009 12:49 AM

Guest :

Its definitely very ironic to catch the ascaris lumbricoides for even a little bit of eposure to the larvae one maybe contaminated with the said specie of parasite.

16 Comments