Serological markers applied in schistosomiasis surveillance in low-transmission areas: relationship between IgA antibodies and circumoval precipitin test in recent infection

In areas where the prevalence and intensity of infections are low for schistosomiasis mansoni, parasitological methods have reduced sensitivity, underestimating the number of positive cases. Immunodiagnostic techniques complement epidemiological studies and can be applied to monitoring control programmes. However, serological diagnosis alone, based solely on antibody detection, is insufficient for identifying active and treated cases, and its application is limited in post-treatment monitoring. These limitations have led to the development of new methodologies or the improvement of existing ones for antibody detection. This study proposes an association between the search for IgM and IgA class antibodies against polysaccharide antigens from the intestinal wall of adult male Schistosoma mansoni worms detected by indirect immunofluorescence assay in paraffin sections (IFA-IgM and IFA-IgA) and the circumoval precipitin test (COPT), with the aim of complementing the identification of active infections, discriminating recent from chronic infections. The positive association between 82.5% of reactive sera in the COPT with irregularly shaped, variable-sized, granular-content globular precipitates and positive sera for IFA-IgA highlights these serological markers for identifying recent infections in low-transmission areas.