Ascaris lumbricoides

Ascaris lumbricoides, an intestinal roundworm, is one of the most common helminthic human infections worldwide. Ascaris lumbricoides is the largest intestinal nematode of man. The female worms are larger than the males and can measure 40 cm in length and 6 mm in diameter. They are white or pink and are tapered at both ends. 

Global spread:

It is estimated that more than 1.4 billion people are infected with A. lumbricoides, representing 25 percent of the world population. A number of features account for its high prevalence including a ubiquitous distribution, the durability of eggs under a variety of environmental conditions, the high number of eggs produced per parasite, and poor socioeconomic conditions that facilitate its spread. Transmission is enhanced by the fact that individuals can be asymptomatically infected and can continue to shed eggs for years, yet prior infection does not confer protective immunity.

Although ascariasis occurs at all ages, it is most common in children 2 to 10 years old, and prevalence decreases over the age of 15 years. Infections tend to cluster in families, and worm burden correlates with the number of people living in a home. Infection rates for ascariasis have not been reported to be higher in patients infected with the human immunodeficiency virus (HIV).

Highest prevalence in tropical and subtropical regions, and areas with inadequate sanitation.

Prevalence in the United States:

In United States, ascariasis is the third most frequent helminth infection, exceeded only by hookworm and Trichuris trichiura (whipworm) .Ascariasis occurs in rural areas of the southeastern United States.

How to get infected?

You can become infected with ascariasis after accidentally ingesting the eggs of roundworm. The eggs can be found in soil contaminated by human feces or uncooked food contaminated by soil that contains roundworm eggs. Children often become infected when they put their hands in their mouths after playing in contaminated soil, according to WHO. Ascariasis can also be passed directly from person-to-person.

Symptoms:

• Abdominal discomfort
• Abdominal cramping
• Abdominal swelling (especially in children)
• Fever
• Coughing and/or wheezing
• Nausea
• Vomiting
• Passing roundworms and their eggs in the stool

Treatment:

Anthelminthic medications (drugs that rid the body of parasitic worms), such as albendazole and mebendazole, are the drugs of choice for treatment of Ascaris infections, regardless of the species of worm. Infections are generally treated for 1-3 days. The drugs are effective and appear to have few side effects.

Prevention:

Infection can be avoided by scrupulous attention to personal hygiene and the careful washing of all fruit and vegetables.
Improved sanitation in developing countries is associated with a reduced risk of transmission of helminthiases to humans.

Resources:

• Ascariasis; DPDx, Centers for Disease Control and Prevention
• Dold C, Holland CV; Ascaris and ascariasis. Microbes Infect. 2011 Jul13(7):632-7. doi: 10.1016/j.micinf.2010.09.012. Epub 2010 Oct 8.
• de Silva N, Brooker S, Hotez P; Soil-Transmitted Helminthic Infection: Updating the Global Picture Disease Control Priorities Project Working Paper No.12 July 2003
• Khandelwal N, Shaw J, Jain MK; Biliary parasites: diagnostic and therapeutic strategies. Curr Treat Options Gastroenterol. 2008 Mar11(2):85-95.
• Ascaris lumbricoides, Martin Walker∗, ... María-Gloria Basáñez∗, in Ascaris: The Neglected Parasite, 2013
• Treatment options in the management of Ascaris lumbricoides., https://www.ncbi.nlm.nih.gov/pubmed/15013922