Ascariasis
Ascariasis is an intestinal worm infection caused by the Ascaris lumbricoides parasite, commonly known as the large common roundworm. This nematode can grow up to 35 centimeters (about 14 inches) in length and is primarily found in tropical regions. The infection occurs when a person ingests food or water contaminated with Ascaris eggs, leading to a complex life cycle that involves migration through various organs, including the lungs and intestines. Symptoms of ascariasis can include pneumonia, abdominal cramps, vomiting, and malnutrition, particularly in children.
This parasitic infection is the most prevalent helminth infection globally, affecting an estimated 772 million to 1.2 billion people, with higher risks associated with young children, travelers to developing countries, and those consuming unsafe food or water. Diagnosis typically involves a doctor's assessment of symptoms and travel history, supported by laboratory tests to identify the presence of eggs in stool samples. Treatment options include antiparasitic medications and, in severe cases, surgical intervention for intestinal blockages. Preventative measures focus on proper sanitation, including washing hands and ensuring food and water safety.
Ascariasis
- ANATOMY OR SYSTEM AFFECTED: Gastrointestinal system, heart, intestines, lungs, respiratory system, stomach, throat
- ALSO KNOWN AS: Roundworm
Definition
Ascariasis is an intestinal worm infestation. It is present worldwide, though mostly in tropical climates. Ascaris lumbricoides is a nematode (roundworm) parasite, also known as the large common roundworm, that can reach up to 35 centimeters (about 14 inches) in length. Like most parasites, Ascaris has a complex life cycle that begins with a person ingesting its eggs. After the parasite hatches in the gut, immature forms of the parasite travel to the heart and lungs, causing a type of pneumonia. They then migrate into the throat, where they are swallowed, reenter the gut, and develop into adult worms. The eggs the adults lay (240,000 per worm per day) pass out with feces to begin their cycle again when contaminated food or water is ingested.
Causes
Ascariasis is caused by ingesting food or water contaminated by feces containing Ascaris eggs.
Incidence and Prevalence
Ascariasis is the most common helminth infection in the world. Helminths are parasitic worms that target the intestines of vertebrates. According to the Centers for Disease Control and Prevention, an estimated 772–892 million to 1.2 billion people are infected by ascariasis worldwide.
Risk Factors
Those persons with an increased chance of developing ascariasis include preschool age or younger children, travelers to developing countries, persons living in the southern United States, persons who eat unsanitary food, and persons who drink unclean water.
Symptoms
A person with any of the following symptoms should not assume the symptoms are caused by ascariasis. Other health conditions may cause these symptoms. Persons who experience any of these symptoms and have been exposed to risks should consult a doctor. The symptoms include pneumonia (dry cough and fever); wheezing; abdominal cramps; vomiting; malnutrition, especially in children; and passing a worm by mouth, nose, or rectum. Symptoms also include those of the diseases caused by Ascaris worms: gallbladder disease, liver abscess, pancreatitis, appendicitis, and peritonitis.
Screening and Diagnosis
A doctor will ask about symptoms, travel, and medical history, and perform a physical exam. The patient may then be referred to a gastroenterologist or a specialist in tropical diseases. Tests may include blood and urine tests, stool specimens to search for worm eggs, intestinal X-rays, or ultrasound imaging.
Treatment and Therapy
It is common to have more than one intestinal parasite, leading to treatment for several. Treatment options include drugs such as mebendazole, albendazole, pyrantel pamoate, and ivermectin, which are all effective medications that kill Ascaris worms, and endoscopy or surgery because an intestinal obstruction of many worms may require further intervention.
Prevention and Outcomes
To help reduce the chance of contracting ascariasis, one should avoid foods prepared without proper sanitary precautions (such as unwashed hands); avoid water and other drinks that might have come from contaminated sources; peel, cook, or wash vegetables in an appropriate cleaning solution if there is a chance those vegetables came from soil fertilized with human excrement; and wash hands when leaving a toilet area.
Bibliography
"About Ascariasis - Soil-Transmitted Helminths." CDC, 13 June 2024, www.cdc.gov/sth/about/ascariasis.html. Accessed 29 Oct. 2024.
Berger, Stephen A., and John S. Marr. Human Parasitic Diseases Sourcebook. Jones and Bartlett, 2006.
Despommier, Dickson D., et al. Parasitic Diseases. 5th ed., Apple Tree, 2006.
"DPDx - Ascariasis." CDC, 19 July 2019, www.cdc.gov/dpdx/ascariasis/index.html. Accessed 29 Oct. 2024.
Holland, Celia, et al. "Global Prevalence of Ascaris Infection in Humans (2010-2021): A Systematic Review and Meta-Analysis." Infectious Diseases of Poverty, vol. 11, no. 1, 2022, p. 113. 18 Nov. 2022, doi:10.1186/s40249-022-01038-z. Accessed 29 Oct. 2024.
Icon Health. Roundworms: A Medical Dictionary, Bibliography, and Annotated Research Guide to Internet References. Author, 2004.
Polsdorfer, Ricker, and David L. Horn. "Ascariasis." Salem Press Encyclopedia of Health, Jan. 2023. EBSCOhost, research.ebsco.com/linkprocessor/plink?id=bd6026f8-6a2a-3c54-aa6a-4438528ae008. Accessed 29 Oct. 2024.
Porter, Robert S., et al., editors. The Merck Manual Home Health Handbook. 3d ed., Merck Research Laboratories, 2009.
Roberts, Larry S., and John Janovy, Jr. Gerald D. Schmidt and Larry S. Roberts’ Foundations of Parasitology. 8th ed, McGraw-Hill, 2009.
Vyas, Jatin M., et al. "Ascariasis." MedlinePlus, 4 Dec. 2022, medlineplus.gov/ency/article/000628.htm. Accessed 29 Oct. 2024.
Weller, P. F., and T. B. Nutman. "Intestinal Nematodes." Harrison’s Principles of Internal Medicine, edited by Anthony Fauci, et al. 17th ed., McGraw-Hill, 2008.