Abstract
BackgroundStrongyloidiasis is a persistent human parasitic infection caused by the intestinal nematode, Strongyloides stercoralis. The parasite has a world-wide distribution, particularly in tropical and subtropical regions with poor sanitary conditions. Since individuals with strongyloidiasis are typically asymptomatic, the infection can persist for decades without detection. Problems arise when individuals with unrecognized S. stercoralis infection are immunosuppressed, which can lead to hyper-infection syndrome and disseminated disease with an associated high mortality if untreated. Therefore a rapid, sensitive and easy to use method of diagnosing Strongyloides infection may improve the clinical management of this disease.Methodology/Principal FindingsAn immunological assay for diagnosing strongyloidiasis was developed on a novel diffraction-based optical bionsensor technology. The test employs a 31-kDa recombinant antigen called NIE derived from Strongyloides stercoralis L3-stage larvae. Assay performance was tested using retrospectively collected sera from patients with parasitologically confirmed strongyloidiasis and control sera from healthy individuals or those with other parasitoses including schistosomiasis, trichinosis, echinococcosis or amebiasis who were seronegative using the NIE ELISA assay. If we consider the control group as the true negative group, the assay readily differentiated S. stercoralis-infected patients from controls detecting 96.3% of the positive cases, and with no cross reactivity observed in the control group These results were in excellent agreement (κ = 0.98) with results obtained by an NIE-based enzyme-linked immunosorbent assay (ELISA). A further 44 sera from patients with suspected S. stercoralis infection were analyzed and showed 91% agreement with the NIE ELISA.Conclusions/SignificanceIn summary, this test provides high sensitivity detection of serum IgG against the NIE Strongyloides antigen. The assay is easy to perform and provides results in less than 30 minutes, making this platform amenable to rapid near-patient screening with minimal technical expertise.
Highlights
Strongyloidiasis is a persistent human parasitic disease caused by the intestinal nematode, Strongyloides stercoralis
Due to the subclinical nature of most infections with S. stercoralis and its ability to auto-infect, strongyloidiasis is a persistent disease that can remain undetected for decades following initial exposure
With increasing use of corticosteroids and other immunosuppressive/immunomodulatory therapies for the treatment of a wide variety of disease states [12,34,35,36], there is considerable cumulative life-time risk of release of S. stercoralis from immune control. Disseminated disease in these individuals can be associated with high mortality [12,37,38,39,40]
Summary
Strongyloidiasis is a persistent human parasitic disease caused by the intestinal nematode, Strongyloides stercoralis. It is endemic in the tropical and subtropical regions of the world where sanitary conditions are poor, and is increasing in prevalence even in resource-rich settings due to widespread travel and migration [1,2,3]. The exact prevalence of strongyloidiasis is not known because in many tropical and subtropical countries S. stercoralis can infect up to 60% of the population [5]. Strongyloidiasis is a persistent human parasitic infection caused by the intestinal nematode, Strongyloides stercoralis. The parasite has a world-wide distribution, in tropical and subtropical regions with poor sanitary conditions. Since individuals with strongyloidiasis are typically asymptomatic, the infection can persist for decades without detection. A rapid, sensitive and easy to use method of diagnosing Strongyloides infection may improve the clinical management of this disease
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