Strongyloides stercoralis: there but not seen.

PURPOSE OF REVIEW: Diagnosis of Strongyloides stercoralis is often delayed owing to patients presenting with nonspecific gastrointestinal complaints, a low parasite load and irregular larval output. Although several diagnostic methods exist to detect the presence of S. stercoralis there is no gold standard. In immunocompromised hosts (patients with malignancy, organ transplantation or concurrent human T-cell-lymphocytic virus 1 infection or those on corticosteroid therapy), autoinfection can go unchecked with large numbers of invasive Strongyloides larvae disseminating widely and causing hyperinfection with dissemination, which can be fatal. This review will highlight current published research on improved diagnostic methods for S. stercoralis and the immune mechanisms thought to be responsible for hyperinfection syndrome.

RECENT FINDINGS: Recent advances in diagnosis of S. stercoralis include a luciferase immunoprecipitation system that shows increased sensitivity and specificity to detect S. stercoralis-specific antibodies and a real-time quantitative PCR method to detect S. stercoralis in fecal samples. The severe clinical manifestations of S. stercoralis observed in human T-cell-lymphocytic virus 1 coinfected patients has been associated with an increased proportion of regulatory T cells that may be responsible for blunting otherwise effective granulocyte responses.

SUMMARY: Strongyloidiasis is a major global health challenge that is underestimated in many countries. Novel diagnostic methods are expected to improve epidemiological studies and control efforts for prevention and treatment of strongyloidiasis. More studies are needed to unveil the mechanisms of severe clinical manifestations of human strongyloidiasis.