Immunoassays as an auxiliary tool for the serodiagnosis of Schistosoma mansoni infection in individuals with low intensity of egg elimination

In an attempt to improve the screening of Schistosoma mansoni-infected individuals from a low-transmission area, we established a protocol that includes three independent coproscopy examinations and two serological assays. Three stool samples were examined using the Kato–Katz and free sedimentation methods and serum samples were tested by IgG-ELISA and IgM-immunofluorescence. Two hundred and sixty-nine individuals participated in the survey: 132 individuals (49%) showed positive serological test results. Of these, 16 (6%) had positive results in stool examination in the first sample batch. However, there were also cases with positive serological test results in spite of negative Kato–Katz stool examinations. Additional stool samples were obtained from these subjects and in this way an additional 11 egg-excretors were found. Our findings suggest that a screening method that combines antibody isotype detection and repeated parasitological stool examinations could increase the chances of detecting S. mansoni-infected patients.