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

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

People catch the infection when they come 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. As the worms grow older, they bury themselves in the walls of the intestines. Later, they produce eggs in the intestines. Areas where the worms go through the skin may become red and painful.

This infection is uncommon in the United States. Most cases seen 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
• Unintentional weight loss
• Vomiting

The following tests may be done:

• Blood antigen test for S. stercoralis
• Complete blood count with differential
• 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.

In some cases, such as in those who will be taking immunosuppressive drugs, people with no symptoms are treated.

Full recovery with eradication of parasites is expected with adequate treatment. Sometimes treatment needs to be repeated.

Infections that are widespread often have a poor outcome, especially in people with weakened immune systems.

• Acute pulmonary eosinophilia (Loeffler's syndrome)
• Disseminated strongyloidiasis, especially in patients with HIV or an otherwise compromised immune system
• 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. Adequate public health services and sanitary facilities provide good control of infection.