Evaluation of whole fresh blood and dried blood on filter paper discs in serological tests for Trypanosoma evansi in experimentally infected water buffaloes

In this study we investigated if whole blood could substitute for serum in the direct card agglutination test (CATT/Trypansosoma evansi) and the indirect card agglutination test (LATEX/T. evansi) for the sero-diagnosis of T. evansi in buffaloes. Likewise blood spots on filter paper were compared with sera for use in the indirect enzyme-linked immunosorbent assay/T. evansi (ELISA) and immunotrypanolysis test (T.L./T. evansi). Samples were collected weekly from experimentally T. evansi infected- and non-infected water buffaloes. To estimate test agreement between serum and respectively whole fresh blood and dried blood spots on filterpaper of the tests, κ values with 95% confidence intervals were calculated, 0.75±0.11 for the CATT/T. evansi; 0.80±0.11 for the ELISA/T. evansi; 0.84±0.11 for the LATEX/T. evansi and 0.93±0.11 for the T.L./T. evansi. In addition κ values with 95% confidence intervals were computed to assess agreement between results obtained in the reference T.L./T. evansi test and those obtained in the other assays; 0.70±0.10 for the CATT-Serum; 0.75±0.11 for the LATEX-Blood; 0.77±0.11 for the LATEX-Serum; 0.81±0.10 for the CATT-Blood; 0.81±0.11 for the ELISA-Serum and 0.84±0.11 for the ELISA-Confetti. Based on the high κ values as calculated, we conclude that serum can be replaced by fresh whole blood for the agglutination assays or blood on filter paper for the ELISA/T. evansi and T.L./T. evansi.