Strongyloidiasis is infection with the roundworm Strongyloides stercoralis (S. stercoralis).

S. stercoralis is a roundworm that is fairly common in warm, moist areas. In rare cases, it can be found as far north as Canada.

People catch the infection when their skin comes in contact with soil contaminated with the worms.

The tiny worm is barely visible to the naked eye. Young roundworms can move through a person's skin and into the bloodstream to the lungs and airways.

They then move up to the throat, where they are swallowed into the stomach. The worms then move to the small intestine, where they attach to the wall. Later, they produce eggs, which hatch into tiny larvae (immature worms) and pass out of the body.

Unlike other worms, these larvae can reenter the body through the skin around the anus, which allows an infection to grow. Areas where the worms go through the skin can become red and painful.

This infection is uncommon in the United States. Most cases in North America are brought by travelers who have visited or lived in South America or Africa.

Most of the time, there are no symptoms.

If there are symptoms, they may include:

• Abdominal pain (upper abdomen)
• Cough
• Diarrhea
• Rash
• Red hive-like areas near the anus
• Vomiting
• Weight loss

The following tests may be done:

• Blood antigen test for S. stercoralis
• Complete blood count with differential
• Total eosinophil count in the blood
• Duodenal aspiration to check for S. stercoralis
• Sputum culture to check for S. stercoralis
• Stool sample exam to check for S. stercoralis

The goal of treatment is to eliminate the worms with anti-worm medications such as ivermectin or albendazole.

In some cases, people with no symptoms are treated. This includes people who take drugs that suppress the immune system.

With proper treatment, worms can be removed and full recovery expected. Sometimes treatment needs to be repeated.

Infections that are severe or affect many areas of the body (disseminated infection) often have a poor outcome, especially in people with weakened immune systems.

• Disseminated strongyloidiasis, especially in persons with HIV or an otherwise weakened immune system
• Eosinophilic pneumonia
• Malnutrition due to problems absorbing nutrients from the gastrointestinal tract (malabsorption)

Call for an appointment with your health care provider if you have symptoms of strongyloidiasis.

Good personal hygiene can reduce the risk of strongyloidiasis. Public health services and sanitary facilities provide good infection control.

Maguire JW. Intestinal nematodes (roundworms). In: Mandell GL, Bennett JE, Dolan R, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, PA: Elsevier Churchill-Livingstone; 2009:chap 287.

Diemert DJ. Intestinal nematode infections. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011: chap 365.