What is Strongyloides stercoralis ?
Infection with Strongyloides stercoralis, a nematode parasite, is frequently asymptomatic or may show few clinical signs. However, on occasion it can persist for many years due to autoinfection, and depending on the immune status of the individual, can be life threatening with dissemination and hyperinfection.
Humans get infected with this nematode parasite by its ability to penetrate skin. They may be present in soil as free-living adults or as infective filariform larvae (this is the stage that can penetrate the skin). Hookworms are another parasite that can penetrate the skin to infect people.
The parasite then gets in the bloodstream and is carried to the lungs. They are carried up to the throat where they are swallowed and end up in the small intestine where they develop into adults.
If symptoms are present, you may see dermatitis of the skin at the point of entry, a cough and occasionally pneumonitis as the larvae pass through the lungs. Abdominal symptoms may occur after the parasite matures to adults resembling peptic ulcer, weight loss, vomiting and diarrhea.
Hives-like rashes may be seen in the area of the buttocks and around the trunk. For more infectious disease news and information, visit and “like” the Infectious Disease News Facebook page.
Rarely, patients with chronic strongyloidiasis have complained of arthritis, cardiac arrhythmias, and signs and symptoms consistent with chronic malabsorption, duodenal obstruction, nephrotic syndrome, and recurrent asthma.
The female adult deposits eggs in the duodenum which later hatch as non-infective rhabditiform larvae which exit the body in the feces and later develop in the soil as either infective filariform larvae or free living adults. And the circle of life continues.
This is a situation where the non-infective rhabditiform larvae become infective filariform larvae before leaving the body. The filariform larvae may penetrate the intestinal wall or the perianal skin to continue re-infecting the person. There are two roundworm infections that are capable of doing this; Strongyloides and Capillaria philippinensis. This can keep the individual infected for years (up to 35 years according to one text).
Rarely autoinfection with the increasing worm burden can lead to dissemination and hyperinfection of the individual. This typically occurs in the immunocompromised host, though not exclusively. People with HIV infection or those taking drugs that suppress the immune system are particularly vulnerable.
Disseminating strongyloidiasis can lead to pulmonary involvement, septicemia (secondary Gram-negative sepsis), shock, wasting and death, in fact if left untreated, the mortality rates of hyperinfection syndrome and disseminated strongyloidiasis can approach 90%.
Strongyloides are found worldwide, in tropical and temperate regions; however, it is more frequently seen in warm, wet areas.
Diagnosis of this infection is based on finding the larvae (primarily the rhabdtiform) in feces. Specifically, the Centers for Disease Control and Prevention says serial stool exams may be required. Traditional stool examinations are insensitive and require up to seven stool exams to reach a sensitivity of 100%. Using special techniques such as funnel techniques or by culture can also be used. In addition, examination of duodenal aspirates are very useful. Duodenal aspirates are more sensitive than stool examination, and duodenal biopsy may reveal parasites in the gastric crypts, in the duodenal glands, or eosinophilic infiltration in the lamina propria. Frequently, larvae can be seen by a simple wet-mount in fluid from a bronchoalveolar lavage (BAL).,
Treatment of strongyloides is with ivermectin, with albendazole as an alternative. Those at risk of dissemination and hyperinfection definitely should be treated.
Strongyloides transmission has been documented via organ transplantation. Related: CDC targets five Neglected Parasitic Infections in the US
The CDC advises physicians be particularly diligent to consider Strongyloides in patients who are on or about to begin corticosteroid therapy or other immunosuppressants, known to have HTLV-1 infection, with hematologic malignancies including leukemias and lymphomas, who have had or are being considered for organ transplantation, with persistent peripheral or unexplained eosinophilia or with recent or remote travel histories to endemic areas.
Of note, though persons with HIV/AIDS can have disseminated strongyloidiasis or hyperinfection syndrome, observational studies have not shown an increased risk in this population.
Good hygienic practices and especially the use of footwear can help prevent this parasitic infection. Proper sewage disposal and fecal management are keys to prevention.
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