| Summary: | Two <I>T. evansi </I>Ag-ELISAs based on different monoclonal antibodies (2G6 Ag-ELISA and Tr7 Ag-ELISA) were evaluated using buffaloes in Southeast Asia, where <I>T. evansi</I> is endemic. The repeatability and robustness of the two Ag-ELISAs were shown to be high. Profiles of antigenaemia varied between individual buffaloes and between the two Ag-ELISAs. Antigen and antibody responses were first detected 7 to 42 days after infection, but in some buffaloes responses fluctuated below cut-off values during infection, whilst in other buffaloes antigen and antibody responses persisted after trypanocidal drug treatment. With the naturally-infected buffaloes, the diagnostic sensitivity estimate of the Tr7 Ag-ELISA (81%) was significantly higher than that of the 2G6 Ag-ELISA (71%), and the IgG ELISA sensitivity (89%) was significantly higher than either the IgM ELISA or CATT sensitivities (78%). In Central Java, 2387 buffaloes were blood sampled in 59 villages, and estimates of test prevalence were 4% with the MHCT, 9% with MI, 58% with the 2G6 Ag-ELISA and 70% with the Tr7 Ag-ELISA, but prevalence values differed between districts and between villages. True incidence rates per animal-year at risk were 0.44 with the Tr7 Ag-ELISA and 0.22 with the 2G6 Ag-ELISA. of 239 market buffaloes sampled, 10% were parasitaemic, 39% antigenaemic, 56% positive by IgG ELISA and 47% positive by CATT, representing an important source of <I>T. evansi</I>. The <I>T. evansi</I> Ag-ELISAs and antibody-detection tests used in this study have many advantages as screening tests over commonly used parasitological tests, in terms of their diagnostic sensitivity and ability to rapidly test large numbers of samples. The two <I>T. evansi </I>Ag-ELISAs could be applied in high prevalence areas, whilst antibody-detection tests (in particular, the IgG ELISA or CATT) would be more appropriate to test buffaloes in low prevalence areas or to confirm the negative-status of buffaloes prior to movement within Indonesia or export. Future work should aim to improve the specificities of the Ag-ELISAs, which were low in this study in contrast to previous reports.
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