the prioChECK? bTV dr detects very low titers of anti-BtV antibodies at an early stage of infection. the test detects anti-BtV antibodies at post infection day 6 in sheep and at post infection day 7 in cattle. infection detection dates were determined in a study conducted by the oie reference laboratory in Pirbright, england, where serum samples of cattle and sheep, experimentally infected with BtV, were tested with the prioChECK? bTV dr at various days post infection.