Blood samples were collected by jugular venipuncture and periferic blood smears horses maintained in tree breed system: confined, semi confined and extensive. The blood of this animals was analyzed for immunofluorescent antibody test (IFAT) for B. equi, and the prevalence obtained were the 89.58%, 87.89% and 45.24%, in extensive system, on semi confined system and confined system, respectively. For the direct exam in blood smear, the values was 16.7%, 16.13% and 4.78%, respectively in extensive system, on semi confined system and confined system