Concomitant Serological and Molecular Methods for Strongyloides stercoralis Screening in an Endemic Area of Spain

Strongyloidiasis is a widespread parasitic disease that can be life-threatening in immunosuppressed people. In the Mediterranean basin, autochthonous cases coexist with imported ones. We aimed to assess the utility of different screening methods, along with the frequency of strongyloidiasis and its associated risk factors in migrants and the native population. This cross-sectional study took place from 2019 to 2022 in the area of the Vega Baja Hospital in Alicante, Spain. Screening was performed in people who were immunosuppressed, at risk of immunosuppression, with blood asymptomatic eosinophilia, and in asymptomatic people from highly endemic countries. Screening methods were serological techniques (ELISA), stool parasitological tests (fecal concentration methods and agar plate culture), and a stool molecular test (PCR). Of the 168 participants (62.5% males, 53.0% migrants, 36.3% immunosuppressed, median age 57 years), 14 (8.3%) had confirmed strongyloidiasis, where 6 were confirmed by serology, 4 by PCR, and 4 by both methods. Overall, 9% of the migrants and 7.6% of the native-born patients were infected. Elevated IgE and hemoglobin and Latin American origin were associated with strongyloidiasis diagnosis. Screening with serology alone would have missed 28.6% of cases. We conclude that strongyloidiasis prevalence is high in our population, both in native and migrant groups, and stool PCR is a useful tool to increase case detection.