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Prevalence of Strongyloides stercoralis infection in a remote Indigenous community as determined by ELISA testing from dried blood spot for antibodies to the recombinant antigen NIE
Conference presentation

Prevalence of Strongyloides stercoralis infection in a remote Indigenous community as determined by ELISA testing from dried blood spot for antibodies to the recombinant antigen NIE

Kate E Mounsey
USC Research Conference, 2013 (Sunshine Coast, Australia, 01-Jul-2013–05-Jul-2013)
University of the Sunshine Coast
2013
url
https://www.usc.edu.au/View
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Abstract

Clinical Sciences Strongyloides stercoralis Indigenous community health ELISA testing
Parasitological diagnosis of infection with the intestinal nematode Strongyloides stercoralis is relatively insensitive and logistically challenging. Serologic assays based on detection of antibodies to crude larval antigen offer increased sensitivity, but specificity is hampered by cross-reactive antibodies and persistence after cure. Further, standardization of antigen for assays is problematic. The use of recombinant antigen can potentially overcome these problems, and the NIE antigen from S. stercoralis has been used widely with good diagnostic sensitivity and specifi city.Detection of antibody eluted from dried blood spots has shown utility in large-scale seroepidemiologic studies, and is appealing in children where venipuncture or stool collection is problematic. We adapted an existing NIE-ELISA protocol for the testing of strongyloides antibody response on dried blood spots collected as part of an ivermectin mass drug administration conducted in a Northern Territory community. The NIE ELISA was first validated using representative positive, negative, and equivocal time-matched serum samples previously tested using S. ratti antigen ELISA. Optimal assay and storage conditions were determined using positive control blood spots, and samples screened with the adapted NIE-DBS-ELISA. Blood spots were stable for several days at 37oC, or following longer-term storage at 4oC, -20oC or -80oC. The sensitivity of the NIE-DBS-ELISA was determined by ROC analysis to be 82%. Of the 219 blood spots tested, 18% were positive for S. stercoralis, a similar prevalence to that documented by standard S. ratti serology. In representative samples positive for S. ratti-specific antibodies, a significant decline in NIE optical density was observed at 6 and 12 months following ivermectin MDA (p <001). No time-associated differences were seen in negative or equivocal samples. This further confirms the high seroprevalence of S. stercoralis in remote Australian Indigenous communities, and suggests that collection of dried blood spots may be useful approach for field-friendly diagnosis of strongyloidiasis.

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