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The objective of this review was to outline an epidemiological profile of Strongyloides stercoralis by parasitological and serological diagnosis in inhabitants, and to associate this profile with different immunosupression situations, in Brazil, over 20 years (1990-2009). The occurrence of S. stercoralis using parasitological methods was 5·5%, being 4·8% in rural and 5·0% in urban areas, characterizing the country as hyperendemic. There was a diversity of techniques used as a diagnostic tool and only 39·1% of the studies presented results based on at least 1 specific method. The occurrence increased with age, being 12·1%, for those over 60 that suggests an epidemiological condition of concern for the elderly population. Of the seroepidemiological studies in the general population the mean positivity in serum samples was 21·7% and 29·2%, using an immunofluorescence antibody test and enzyme-linked immunosorbent assay (ELISA), respectively. The occurrence of strongyloidiasis in immunosuppressed individuals was 11·8% by parasitological methods and 19·5% using immunological methods. Considering that Brazil is a tropical country and that the character of chronicity and autoinfection of the parasite that can result in severe forms of hyperinfection or dissemination makes strongyloidiasis an important medically and socially neglected problem.
The objective of this review was to outline an epidemiological profile of Strongyloides stercoralis by parasitological and serological diagnosis in inhabitants, and to associate this profile with different immunosupression situations, in Brazil, over 20 years (1990-2009). The occurrence of S. stercoralis using parasitological methods was 5·5%, being 4·8% in rural and 5·0% in urban areas, characterizing the country as hyperendemic. There was a diversity of techniques used as a diagnostic tool and only 39·1% of the studies presented results based on at least 1 specific method. The occurrence increased with age, being 12·1%, for those over 60 that suggests an epidemiological condition of concern for the elderly population. Of the seroepidemiological studies in the general population the mean positivity in serum samples was 21·7% and 29·2%, using an immunofluorescence antibody test and enzyme-linked immunosorbent assay (ELISA), respectively. The occurrence of strongyloidiasis in immunosuppressed individuals was 11·8% by parasitological methods and 19·5% using immunological methods. Considering that Brazil is a tropical country and that the character of chronicity and autoinfection of the parasite that can result in severe forms of hyperinfection or dissemination makes strongyloidiasis an important medically and socially neglected problem.
RESUMENOBJETIVO: Estandarizar la técnica de ELISA para diagnóstico de la infección humana por el parásito Strongyloides stercoralis. MATERIAL Y MÉTODOS: Se preparó antígeno crudo usando larvas filariformes obtenidas de muestras de heces positivas cultivadas con carbón vegetal. Las larvas fueron trituradas mediante sonicación y lavadas por centrifugación para obtener extractos de proteínas para usarlos como antígeno. La concentración proteica final fue de 600 µg/mL. Se probó varios tipos de placas de ELISA y se determinó las concentraciones de antígeno, sueros, conjugado y puntos de corte, para permitir la diferenciación de la infección. Los controles positivos fueron sueros de pacientes con síndrome de hiperinfección e infección intestinal, comprobados mediante exámenes parasitológicos de heces; y los controles negativos fueron sueros de personas provenientes de zonas no endémicas y con comprobación mediante exámenes parasitológicos de la ausencia del parásito. RESULTADOS:Los valores óptimos fueron 5 µg/mL para el antígeno, 1/64 para el suero, 1/1000 para el conjugado; los valores de densidad óptica para las muestras positivas fueron en promedio 1,2746 (1,1065 -1,4206, DS = 0,3284) y de las muestras negativas 0,4457 (0,3324 -0,5538, DS = 0,2230). Se examinó 20 muestras de suero de sujetos positivos y 100 de sujetos negativos, obteniéndose sensibilidad de 90% y especificidad de 88%. CONCLUSIÓN: Los resultados muestran que esta técnica puede constituirse en una prueba de tamizaje de estrongiloidiosis en estudios de población. Palabras clave: Strongyloides stercoralis; estrongiloidiosis; ELISA; serología; diagnóstico de laboratorio. ELISA TECHNIQUE STANDARDIZATION FOR STRONGYLOIDIASIS DIAGNOSISSUMMARY OBJECTIVE: To standardize ELISA technique for human Strongyloides stercoralis infection diagnosis. MATERIAL AND METHODS: A crude antigen was prepared using filariform larvae obtained from positive stool samples cultured with charcoal. Harvested larvae were crushed by sonication and washed by centrifugation in order to obtain protein extracts to be used as antigen. Final protein concentration was 600 µg/mL. Several kinds of ELISA plates were tested and antigen concentration, sera dilution, conjugate dilution and cut off were determined to identify infection. Sera from patients with both hyperinfection syndrome and intestinal infection demonstrated by parasitological examination were positive controls and sera from people living in non-endemic areas with no infection demonstrated by parasitological examination were negative controls. RESULTS: Best values were 5 µg/mL for antigen, 1/64 for sera, 1/1000 for conjugate; optical density values for positive samples were 1,2746 (1,1065 -1,4206, DS = 0,3284) and for negative samples 0,4457 (0,3324 -0,5538, DS = 0,2230). Twenty sera samples from positive subjects and one hundred from negative subjects were examined, obtaining 90% sensitivity and 88% specificity. CONCLUSION: The results show this technique could be useful as strongyloidiasis screening test in population studies.
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