Utility of recombinant Schistosoma bovis 22.6 kDa antigen for diagnosis of human urogenital schistosomiasis by ELISA: a cross-sectional study in Yewa North LGA, Ogun State, Nigeria

In many endemic regions, accurately diagnosing urogenital schistosomiasis remains challenging, particularly in cases of low-intensity infection and limited laboratory capacity. Exploring antigens that cross-react between related schistosome species provides a promising alternative to conventional diagnostic approaches. Schistosoma bovis —an animal parasite closely related to S. haematobium and sharing the same Bulinus snail hosts in overlapping habitats— is a strong candidate for such studies. This work therefore assessed whether the recombinant S. bovis 22.6 kDa antigen (rSb22.6 kDa) could detect anti-schistosome antibodies in urine samples from individuals living in S. haematobium -endemic communities in Nigeria. Urine samples from 559 individuals (290 adults and 269 children; 235 males and 313 females) from four communities and schools in Yewa North Local Government Area, Ogun State, Nigeria, were collected. Samples were examined for S. haematobium eggs by microscopy, screened for anti-schistosomal antibodies using r Sb 22.6 kDa ELISA, and analyzed for haematuria, leukocyturia, and proteinuria using reagent strips. Prevalence by microscopy was 13.9% (78/558), while 54.1% (299/553) of samples were seropositive by ELISA. Among ELISA-positive individuals, 29.8% had haematuria, 47.9% had leukocyturia, and 37.1% had proteinuria. Of 480 microscopy-negative individuals, 221 (46.0%) were ELISA-positive. When microscopy was used as the reference standard, the r Sb 22.6 kDa-ELISA showed 46.2% sensitivity and 45.8% specificity. However, ELISA positivity correlated significantly with clinical markers of urogenital pathology ( P < 0.05). The r Sb 22.6 kDa antigen demonstrated cross-reactivity with antibodies in urine from individuals in S. haematobium -endemic communities. The high seropositivity compared to microscopy prevalence may reflect detection of low-intensity infections, past exposure with persistent antibodies, or ongoing transmission intensity in these communities. While the current performance of the assay does not support its use for individual diagnosis, it shows potential for sero-epidemiological surveillance in endemic areas. Further validation studies incorporating molecular diagnostics and longitudinal follow-up will clarify the significance of antibody positivity in the absence of detectable eggs. Not applicable.