RESUMEN
It is discussed first autoctonous prenatal case of Babesia bovis in Brazil. After a normal birth a male Brown Swiss calf, had not sucked colostrum and died at three days after birth. Clinical and laboratory examinations revealed petechial hemorrhages in oral and conjuntival mucosas, red urine and parasitemia due to B. bovis as shown in blood smears Giemsa stained. Post-mortem examination revealed hepato-splenomegaly, congestion and edema in lungs, brain and kidneys. Optical and eletronic microscopies showed severe congestion, edema, red cells aglutination, and most of the erythrocites in the brain capillaries contained Babesia organisms, which were also detected outside the cells. In the kidneys interlobular interstitial nephritis, glomerulonephritis mesangioproliferative diffuse and rare parasites in the capillaries were observed. 1.8 per cent of the erythrocites in peripheral circulation were parasitized in the brain capillaries more than 90 per cent of those cells had Babesia organisms