Abstract
BackgroundChagas disease is a parasitic disease caused by the protozoan parasite Trypanosoma cruzi. In Mexico, the burden of the disease is difficult to estimate and improving surveillance for Chagas disease is an important priority. We aimed here at determining the seroprevalence of T. cruzi infection in humans in a rural community in Veracruz.MethodsSerum samples (196) were analyzed for T. cruzi infection using five enzyme-linked immunosorbent assay (ELISA) tests: two in-house tests based on crude parasite extract and three commercial ELISA kits. Because of highly discordant results, we further explored the importance of parasite antigens and strains by western-blot analysis.ResultsA total of 74 samples (37.7 %) were reactive with at least one ELISA, but discordance among tests was very high. The best agreement was between Chagatest recombinant and Chagatek ELISA (Kappa index = 0.798). The agreement between other combinations of tests ranged from 0.038 to 0.518. Discordant samples were confirmed by western-blot analysis using up to nine parasite strains, giving a seroprevalence of 33.7 %.ConclusionsCommercial tests had a very limited ability to detect T. cruzi infection in the study population. In-house tests based on crude parasite antigens showed a greater sensitivity but were still unable to detect all cases of T. cruzi infection, even when based on a local parasite strain. The high seroprevalence confirmed the hyper-endemicity of T. cruzi infection in the region. Reliable epidemiological surveillance of Chagas disease will require the development of improved diagnostic tests.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-015-1072-2) contains supplementary material, which is available to authorized users.
Highlights
Chagas disease is a parasitic disease caused by the protozoan parasite Trypanosoma cruzi
We previously found a good agreement between commercial tests, including a rapid test and a recombinant enzyme-linked immunosorbent assay (ELISA) test, and an inhouse ELISA based on a crude extract from a local parasite strain from Mexico [15], suggesting that all these tests may be useful for the serodiagnostic of T. cruzi infection in Mexico [16]
ELISA assays A total of 196 blood samples were collected from inhabitants of the village of Las Josefinas, Veracruz, and tested with five ELISA tests for T. cruzi antibodies (Fig. 1)
Summary
Chagas disease is a parasitic disease caused by the protozoan parasite Trypanosoma cruzi. The disease in endemic in the Americas, where vector species are widespread [3], but it is becoming globalized due to Serologic diagnostic for T. cruzi infection has undergone great progress in recent years, with the development and commercialization of many assays based on different parasite antigens. Guzmán-Gómez et al Parasites & Vectors (2015) 8:466 of most of these assays appears very high (often >98 % for both). Their actual performance has been found to be somewhat lower [11] and no goldstandard has been identified for an accurate and reliable diagnostic of T. cruzi infection. The World Health Organization and most National guidelines in Latin American countries still recommend the use of two tests based on different principles and antigens, and in case of discordance, a third test can provide a final diagnostic
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