strongyloides

Strongyloides is a genus of nematodes that includes species capable of infecting humans, most notably Strongyloides stercoralis. It is characterized by its ability to complete an autoinfective life cycle, allowing infection to persist for decades without re-exposure. The parasite alternates between free-living and parasitic cycles and has a complex life cycle that can occur entirely within a human host.

Transmission occurs through contact with soil containing infective filariform larvae. These larvae penetrate the skin, migrate via the bloodstream to the lungs, ascend the airways to the pharynx, and are swallowed. In the small intestine, parasitic female worms reproduce by parthenogenesis, producing eggs that hatch into rhabditiform larvae within the intestine. These larvae are excreted in stool but can also molt into filariform larvae inside the host, leading to autoinfection. Autoinfection enables long-term, sometimes lifelong, infections and can be amplified in conditions of immunosuppression.

Clinical features range from asymptomatic carriage to chronic gastrointestinal symptoms such as abdominal pain, diarrhea, and weight loss, as well as pulmonary signs during migration. A characteristic cutaneous manifestation is larva currens, a rapidly moving serpiginous rash. Eosinophilia may be present. In immunocompromised individuals, particularly those on corticosteroids, hyperinfection syndrome or disseminated strongyloidiasis can occur with high mortality if not promptly treated.

Diagnosis commonly relies on demonstration of larvae in stool samples, with specialized techniques like Baermann concentration or agar plate culture. Serology and molecular methods can support diagnosis in some settings. First-line treatment is ivermectin, with albendazole as an alternative or adjunct in certain cases. Prevention centers on reducing exposure to contaminated soil, particularly in endemic areas, and screening at-risk populations, including immigrants, travelers, and immunosuppressed patients.