title: Schistosoma mansoni in a low-prevalence area in Brazil: the importance of additional methods for the diagnosis of hard-to-detect individual carriers by low-cost immunological assays.
abstract: Schistosomiasis diagnosis is based on the detection of eggs in the faeces, which is laborious and lacks sensitivity, especially for patients with a low parasite burden. Immunological assays for specific antibody detection are available, but they usually demonstrate low sensitivity and/or specificity. In this study, two simple immunological assays were evaluated for the detection of soluble Schistosoma mansoni adult worm preparation (SWAP) and egg-specific IgGs. These studies have not yet been evaluated for patients with low parasite burdens. Residents of an endemic area in Brazil donated sera and faecal samples for our study. The patients were initially diagnosed by a rigorous Kato-Katz analysis of 18 thick smears from four different stool samples. The ELISA-SWAP was successful for human diagnosis with 90% sensitivity and specificity, confirming the Kato-Katz diagnosis with nearly perfect agreement, as seen by the Kappa index (0.85). Although the ELISA-soluble S. mansoni egg antigen was 85% sensitive, it exhibited low specificity (80%; Kappa index: 0.75) and was more susceptible to cross-reactivity. We believe that immunological assays should be used in conjunction with Kato-Katz analysis as a supplementary tool for the diagnosis of schistosomiasis for patients with low infection burdens, which are usually hard to detect.
authors.affiliation: Fiocruz, Centro de Pesquisas René Rachou, Laboratório de Pesquisas Clínicas, Belo Horizonte, MG, Brasil.
authors.forename: Rafaella Fortini Queiroz
authors.initials: RF
authors.lastname: Grenfell
authors.forename: Watson
authors.initials: W
authors.lastname: Martins
authors.forename: Martin
authors.initials: M
authors.lastname: Enk
authors.forename: Aureo
authors.initials: A
authors.lastname: Almeida
authors.forename: Liliane
authors.initials: L
authors.lastname: Siqueira
authors.forename: Vanessa
authors.initials: V
authors.lastname: Silva-Moraes
authors.forename: Edward
authors.initials: E
authors.lastname: Oliveira
authors.forename: Nídia Francisca de Figueiredo
authors.initials: NF
authors.lastname: Carneiro
authors.forename: Paulo Marcos Zech
authors.initials: PM
authors.lastname: Coelho
mesh_terms: D000328:Adult; D000818:Animals; D000909:Antibodies, Helminth / Q000097:blood; D000947:Antigens, Helminth / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005243:Feces / Q000469:parasitology; D005260:Female; D006801:Humans; D008297:Male; D012550:Schistosoma mansoni / Q000276:immunology*; D012555:Schistosomiasis mansoni / Q000175:diagnosis* / Q000453:epidemiology; D012680:Sensitivity and Specificity
chemical_list: D000909:Antibodies, Helminth; D000947:Antigens, Helminth