Chronology of events during the 12-week cohabitation period. Clinical, serological, and PCR findings in female animals of the pasture group are shown. The acutely Besnoitia besnoiti (Bb)-infected Limousin cows SA 20 and 22 were introduced into the experiment on trial days 3 and 51, respectively. Simmental heifers SA 4, 6, and 8 became infected with B. besnoiti during the experimental period. In the reference system used, a blood sample was regarded as seropositive if it revealed a positive result in at least two of the three tests applied: IFAT, tachyzoite and bradyzoite immunoblot.