Bovine trypanosomosis, caused by Trypanosoma vivax has a significant negative impact on livestock. This research was performed with the aim of determining the immunoreactive proteins present in T. vivax. Thus, five sheep were experimentally infected with T. vivax TvZC1 isolate. Animal number 1 was used as the source of the trypanosomes and to prepare the soluble extract of parasites. Sheep numbers 2 to 5 were monitored for eight weeks and sera was obtained every two weeks for immunodetection. Parasites obtained from animal 1 were analyzed for T. vivax proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot (WB). The WB analysis showed three immunodominant proteins with a molecular mass of 42, 64 and 72 kDa, approximately. The 64 kDa protein was recognized by every animal during the complete infection period. The 72 kDa protein only was detected by animals 2, 3 and 5 during the infection course, whereas in animal 4 it was only detected during the 6th and 8th weeks post infection. Moreover, the 42 kDa polypeptide was slightly immunorecognized by animals 2, 3 and 4 during the complete infection period, but in animal 5 only it was identified during the 2nd week post infection. It is assumed that the 42 kDa protein is the VSG of T. vivax, which resulted in a low antigenic capacity, contrary to the protein of 64 kDa which showed a high antigenic capacity and cross-reactivity with Trypanosoma evansi.