Roundworm Infection

Roundworm infection, also known as ascariasis, is caused by Ascaris lumbricoides. It’s the most common type of intestinal worm infection, occurring worldwide. Most patients recover without treatment, but complications can occur when adult worms move into certain organs and multiply, resulting intestinal obstruction.

Roundworm is most common in tropical areas with poor sanitation and in Asia, where farmers use human feces as fertilizer. In the United States, it’s more prevalent in the South, particularly among children ages 4 to 12. However, international travelers and immigrants (especially from Asia and Latin America) are at an increased risk for infection.

Causes

A. lumbricoides is a large roundworm that resembles an earthworm. It’s transmitted to humans by ingestion of soil contaminated with human feces that harbor A. lumbricoides ova. Such ingestion may occur directly (by eating contaminated soil) or indirectly (by eating poorly washed raw vegetables grown in contaminated soil). Hand-to-mouth transmission is also possible—hands that are contaminated by touching soil or other contaminated surfaces transmit the infective eggs to the mouth. The larvae can also enter the human body directly through a break in the skin. Roundworm infection never passes directly from person to person, although whole families may be infected as a result of shared food or living conditions.

After ingestion, A. lumbricoides ova hatch and release larvae, which penetrate the intestinal wall and reach the lungs through the bloodstream. After about 10 days in the pulmonary capillaries and alveoli, the larvae migrate to the bronchioles, bronchi, trachea, and epiglottis. There they are swallowed and returned to the intestine to mature into adult worms. This cycle takes approximately 2 to 3 months.

Complications

Complications of roundworm include biliary or intestinal obstruction as well as pulmonary disease. It may also be associated with malnutrition, iron deficiency anemia, and failure to thrive. Death may occur from bowel obstruction or perforation.

Assessment Findings

The patient’s history may reveal ingestion of poorly washed raw vegetables. Most patients with roundworm are asymptomatic. For those who are symptomatic, roundworm produces two phases: early pulmonary and prolonged intestinal.

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