Drug Sensitivity of Trypanosoma evansi and the Use of Immunoassays in Diagnosing Infections with T. evansi in Buffaloes in Vietnama

: The biological characteristics of isolates of T.evansi collected from buffalo in different provinces in North Vietnam was determined in terms of their sensitivity to drugs currently used in the treatment of trypanosomosis. Five isolates were collected from buffalo, cloned and then tested against Trypamidium, Samorine, Naganol and Veriben. All isolates were sensitive to Naganol and Veriben. An isolate from a buffalo in Ha bac province (Hb1) was the least sensitive with trypamidium at a CD80 > 128mg/kg, more than 8 times the CD 100 of the remining isolates (16mg/kg). An antigen-detection enzyme immunoassay (Ag-ELISA) based on a T.evansi-specific monoclonal antibody was evaluated for its ability to detect infections with T.evansi in buffalo. The sensitivity of the Ag-ELISA was 63% and the specificity 75%. The positive predictive value of this assay was too low to allow identification of individual infected animals on the results of a single test in the districts investigated. For definitive diagnosis, a serial testing protocol was used, where a more specific test, the card agglutination test (CATT) was used initially and any positive samples was then checked by the Ag-ELISA.