strongyloidiasis

Strongyloidiasis is a human infection caused by the intestinal nematode Strongyloides stercoralis. The parasite has a complex life cycle that includes free-living and parasitic forms. Infective filariform larvae in soil penetrate the skin, migrate via the bloodstream to the lungs, ascend the tracheobronchial tree, and are swallowed into the small intestine, where adult females lay eggs that hatch into rhabditiform larvae. These larvae can be excreted in feces or become autoinfective filariform larvae that penetrate the intestinal wall or perianal skin, allowing the infection to persist for decades without re-exposure.

The clinical spectrum ranges from asymptomatic carriage to mild gastrointestinal symptoms, diarrhea, and abdominal pain. A serpiginous, pruritic rash known as larva currens may appear around the buttocks or thighs. Pulmonary involvement can cause cough, wheeze, and transient infiltrates. Eosinophilia is common but may be absent in disseminated disease. In immunosuppressed individuals, especially those receiving corticosteroids or with HTLV-1 infection, the infection can progress to hyperinfection and disseminated strongyloidiasis, which carries high mortality if not promptly treated.

Diagnosis relies on identification of larvae in stool or duodenal aspirates, though stool samples may require multiple tests. Serologic tests (antibody detection) and molecular assays can support diagnosis, particularly in low-becited larval shedding. Treatment is primarily with ivermectin, given orally; albendazole is an alternative or adjunct in some cases. Hyperinfection requires longer and more aggressive therapy and careful management of immunosuppression. Prevention focuses on avoiding skin contact with soil, improving sanitation, and screening high-risk individuals before immunosuppressive therapy or transplantation.