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What Is Strongyloidiasis?

Reviewed by Dan Brennan, MD on April 23, 2021

‌Strongyloidiasis is an intestinal infection caused by a type of roundworm called Strongyloides stercoralis. It can live and reproduce in your intestines for decades without causing symptoms. However, in people with weak immune systems, it can be life-threatening. It lays eggs in your intestines, and when the larvae hatch, they immediately re-infect you. This is how the infection can continue for so long. 

What Causes Strongyloidiasis?

‌Strongyloidiasis is caused by a parasite, which is an organism that lives on another organism for food. The roundworm that causes strongyloidiasis lives in soil, water, or feces as larvae. When you come in contact with these larvae, they penetrate your skin and make their way into your small intestine. 

Once they are in your small intestine, they lay their eggs. Adult females can lay up to 40 eggs per day. These eggs are either passed out in the stool and continue to contaminate the soil, or they remain inside of you and cause autoinfection. This is when they burrow back into your intestines or the skin around your anus to re-infect you. This may not cause any symptoms, even with a persistent infection.

What Are the Symptoms of Strongyloidiasis?

‌Up to half of all people with strongyloidiasis have no symptoms. People with symptoms show digestive tract-related issues that include the following: ‌

People with advanced cases may have more severe symptoms, including the following: ‌

How Is Strongyloidiasis Diagnosed?

‌Strongyloidiasis can be difficult to diagnose because examining the stool under a microscope doesn't always show the infection. Examining the stool on five occasions at different times can be more reliable. Strongyloidiasis can sometimes be diagnosed with a blood test. More advanced cases may be diagnosed by testing fluid from your lungs or small intestine. 

What Are Complications of Strongyloidiasis?

‌People with a compromised immune system are at risk of hyperinfection syndrome. Hyperinfection syndrome can occur from a new infection or from a previous one that was dormant. It happens when organs that are not normally part of the parasite's lifecycle become infected. 

In cases of hyperinfection syndrome, the larvae travel to other parts of the body such as the lungs, liver, heart, and central nervous system. In these cases, the death rate can be as high as 80%. 

People with the following conditions have a higher risk of hyperinfection syndrome:‌

How Is Strongyloidiasis Treated?

‌Strongyloidiasis is treated with medicine. The best medicine to treat it is ivermectin. The standard treatment is 200 micrograms per kilogram of ivermectin once daily for 2 days. You may not be able to take ivermectin if you've recently traveled to areas of central Africa. In that case, strongyloidiasis can be treated with 400 milligrams of albendazole orally twice a day for 7 days. 

People who have a weakened immune system or hyperinfection syndrome need to be treated until a sputum or stool culture is negative for 2 weeks. In some cases, antibiotics are required to treat bacterial infections as well. 

What Are Risk Factors for Strongyloidiasis?

‌Strongyloidiasis is most often found in wet, moist areas, including South America, Africa, and the Southeastern United States, particularly rural Appalachia. You are most at risk if you've lived or traveled in those areas for a long period of time. Immigrants, refugees, and military veterans are most at risk. 

Strongyloidiasis is found more often in the following people:‌

  • Those who are socioeconomically disadvantaged 
  • Those living in institutions
  • Those living in rural areas
  • Those working in agriculture 

‌Because the parasite that causes strongyloidiasis lives in contaminated soil, activities that increase your contact with soil increase your chance of getting infected. These include walking barefoot, contact with sewage or human waste, or contact with contaminated soil due to occupations like farming or coal mining.

How Can Strongyloidiasis Be Prevented?

‌Strongyloidiasis has mostly been eliminated in countries where sanitation and human waste disposal have improved. Additional strategies to prevent strongyloidiasis include the following: ‌

  • Wearing shoes when you walk on soil
  • Avoiding contact with sewage and fecal matter
  • Cleaning up after dogs
  • Ensuring proper disposal of sewage and fecal management 
WebMD Medical Reference

Sources

SOURCES:

‌Centers for Disease Control and Prevention: “Parasites - Strongyloides," "Strongyloidiasis Infection FAQs."

Gastroenterology and Hepatology: "Strongyloidiasis."

Medscape: "Strongyloidiasis."

Merck Manual: "Strongyloidiasis."

World Health Organization: "Strongyloidiasis."

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