Exploring the application of the WHO guidelines for the public health control of strongyloidiasis through a seroprevalence study in Ethiopia

WHO recently published the first guidelines for the public health control of Strongyloides stercoralis in endemic areas. The commercial availability of serological assays for the diagnosis of infection with S. stercoralis would facilitate the use of antibody-based diagnostics for mapping purposes. This study aimed to explore the application of the recent WHO guidelines through a seroprevalence study in Ethiopia. In addition, the study assessed the potential collateral benefits of existing ivermectin (IVM) mass drug administration (MDA) targeting filarial diseases on the prevalence of strongyloidiasis. Banked serum samples ( n = 6693) from a previous epidemiological study conducted in Ethiopia in 2019 were analyzed. Samples originated from 63 schools across 33 woredas, representing implementation units for neglected tropical diseases control. Antibodies against S. stercoralis were detected using the InBios Strongy Detect IgG ELISA, targeting recombinant NIE and SsIR antigens. Overall seroprevalence of S . stercoralis infection was 10.4% (95% CI 9.7–11.1). Woreda-level seroprevalence ranged from 2.7% (95% CI 0.9–7.7) to 41.0% (95% CI 32.7–49.9). Only seven of the 33 woredas exceeded the WHO threshold (15% observed seroprevalence in school-aged children) for implementing IVM MDA. None of the woredas where IVM had been administered in the five years preceding sampling (2014–2018) exceeded this threshold. With the limits deriving from the study design, these results suggest that dedicated MDA for strongyloidiasis may not be required nationwide in Ethiopia but rather limited to a selected number of woredas and indicate collateral benefits of existing IVM-based programs. To support accurate program decision-making, national health institutes require technical manuals that define survey designs considering the performance characteristics (sensitivity and specificity) of the diagnostic test used. Furthermore, commercial serological assays must include validated cutoffs and information on performance characteristics and clearly specify the target condition and target population for which they were derived. Meeting these requirements will facilitate the application of the recent WHO guidelines using serology.