MEM INST OSWALDO CRUZ, RIO DE JANEIRO, 108(3) May 2013
PAGES: 328-334 DOI: 10.1590/0074-0276108032013011 Full paper
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

Rafaella Fortini Queiroz Grenfell1, Watson Martins1, Martin Enk1, Áureo Almeida1, Liliane Siqueira1, Vanessa Silva-Moraes1, Edward Oliveira2, Nídia Francisca de Figueiredo Carneiro3, Paulo Marcos Zech Coelho1,+

1Laboratório de Esquistossomose
2Laboratório de Pesquisas Clínicas, Centro de Pesquisas René Rachou-Fiocruz, Belo Horizonte, MG, Brasil
3Centro de Controle de Zoonoses, Montes Claros, MG, Brasil

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.

Received 25 September 2012
Accepted 7 January 2013
Financial support: CNPq-Decit 34/2008), FAPEMIG, FIOCRUZ, CPqRR, PPSUS
PMZC and RFQG are senior fellow and doctoral fellow, respectively, from CNPq.
+ Corresponding author: This e-mail address is being protected from spambots. You need JavaScript enabled to view it.

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