Comparison of serological tests for Trypanosoma evansi natural infections in water buffaloes from north Vietnam

In the present study, a collection of 415 water buffalo serum samples origi nating from the north of Vietnam was used for evaluation of different diagn ostic antibody detection methods available to detect infections with Trypan osoma evansi. The diagnostic sensitivity and speci- ficity of a direct card agglutination test (CATT/T evansi), an indirect card agglutination test (L ATEX/T evansi) and a newly developed antibody detection ELISA (ELISA/T evan si) was calculated on the basis of parasitological results, obtained by mou se inoculation, and compared for all assays. The immume trypanolysis assay with the predominant T. evansi RoTat 1.2 variable antigen type was used as reference test for antibody presence. All parasitologically confirmed anima ls (n=8) were positive in all tests. Diagnostic specificity was highest in CATT/ T. evansi (98%) followed by the ELISA/T evansi (95%) and the LATEX/T. evansi (82%). Concordance of the variant specific immune trypanolysis test with the other tests was calculated and revealed that few (1-8%) false pos itive results were actually due to a specific reactions, and that LATEX/T. evansi and ELISA/T. evansi detected more immune trypanolysis positives than the CATT/T: evansi. It was concluded that, apart from the immune trypanoly sis test, which is not generally applicable, ELISA/T. evansi with a 30% pos itivity cut-off and LATEX/. evansi, thanks to their superior capacity of de tecting T. evansi specific antibodies, would be suitable as epidemiological tools detecting both active infections and persisting T. evansi specific a ntibodies. The ELISA/T. evansi with a 50% positivity cut-off and the CATT/T . evansi on the other hand, seem more appropriate to detect true infected w ater buffaloes. (C) 2000 Elsevier Science B.V. All rights reserved.