Fig. 1

The results of the initial herd screens of the 26 study farms. The figure illustrates the results of the initial herd screens for the 26 farms presented in this manuscript. ^ indicates the 19 herds where WHTs were performed. The left y-axis displays the number of PIs identified at the WHT (where performed) depicted for each farm by the solid bars - the Farm 2 bar is hashed to represent in-utero PI animals. For the 7 farms that did not undertake WHTs because their regular surveillance did not indicate exposure, it was assumed that no PIs were present. The right y-axis displays the BM Ab OD ratio. Along the x -axis, each column represents an individual farm stating both the percentage of antibody positive youngstock (YS) at the Check Test (* all farms except Farms 24, 27 & 28 submitted ten animals who presented 9, 8 & 7 youngstock respectively) and the Farm number. (Graph Key attached to the bottom of Fig. 1)