Strongyloidiasis Infection FAQs
What is strongyloidiasis?
Strongyloidiasis is a disease caused by a nematode, or a roundworm, in the genus Strongyloides. Though there are over 40 species within this genus that can infect birds, reptiles, amphibians, livestock and other primates, Strongyloides stercoralis is the primary species that accounts for human disease. The larvae are small; the longest reach about 1.5mm in length -- the size of a mustard seed or a large grain of sand.
How do people get infected with strongyloides?
Strongyloides is classified as a soil-transmitted helminth. This means that the primary mode of infection is through contact with soil that is contaminated with free-living larvae. When the larvae come in contact with skin, they are able to penetrate it and migrate through the body, eventually finding their way to the small intestine where they burrow and lay their eggs. Unlike other soil-transmitted helminths such as hookworm and whipworm whose eggs do not hatch until they are in the environment, the eggs of Strongyloides hatch into larvae in the intestine. Most of these larvae will be excreted in the stool, but some of the larvae may molt and immediately re-infect the host either by burrowing into the intestinal wall, or by penetrating the perianal skin. This characteristic of Strongyloides is termed auto-infection. The significance of auto-infection is that unless treated for Strongyloides, persons may remain infected throughout their lifetime.
In addition to contact with soil and auto-infection, there have been rare cases of person-to-person transmission in:
- organ transplantation
- institutions for the developmentally disabled
- long-term care faciliites
- daycare centers.
Where do most cases of strongyloidiasis occur in the United States?
In the United States, Strongyloides has classically been associated with uniformed-service veterans who returned from tropical regions such as Southeast Asia and the South Pacific during World War II. Small domestic studies have shown locations of infection in rural Appalachia. The highest rates in the United States have been documented in immigrant populations.
Strongyloides is more commonly found in areas that are relatively warm and moist, in rural areas, and areas associated with agricultural activity, but it can occur anywhere. It is found more frequently in socio-economically disadvantaged persons and in institutionalized populations.
What are the signs and symptoms of strongyloidiasis?
The majority of people infected with Strongyloides are without symptoms. Those who do develop symptoms tend to have non-specific, or generalized complaints. Some people develop abdominal pain, bloating, heartburn, intermittent episodes of diarrhea and constipation, a dry cough, and rashes. Rarely people will develop arthritis, kidney problems, and heart conditions.
Strongyloidiasis can be severe and life-threatening in persons who:
- are on oral or intravenous steroids -- such as those with asthma or chronic obstructive pulmonary disease (COPD) exacerbations, lupus, gout, or in persons using steroids for immunosuppression or symptomatic relief
- are infected with the virus HTLV-1
- have hematologic malignancies such as leukemia or lymphoma
- are transplant recipients.
How soon after the exposure do symptoms develop?
Most people do not know when their exposure occurred. For those who do, a local rash can occur immediately. The cough usually occurs several days later. Abdominal symptoms typically occur approximately 2 weeks later, and larvae can be found in the stool about 3 to 4 weeks later.
What should I do if I think I might have strongyloidiasis?
See your health care provider.
How is infection with Strongyloides diagnosed?
Strongyloides is classically diagnosed by visualization of larvae on microscopic stool examination. This may require that you provide multiple stool samples to your doctor or the laboratory. Some laboratories are capable of diagnosing Strongyloides with blood tests.
How is strongyloidiasis treated?
Safe and effective drugs are available to treat infection with Strongyloides.
How can strongyloidiasis be prevented?
The best way to prevent Strongyloides infection is to wear shoes when you are walking on soil, and to avoid contact with fecal matter or sewage. Proper sewage disposal and fecal management are keys to prevention.
This information is not meant to be used for self-diagnosis or as a substitute for consultation with a health care provider. If you have any questions about the parasites described above or think that you may have a parasitic infection, consult a health care provider.
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