Figure 1. . . Location of 209 farms in Belgium from which 519 pairs of cow/calf serum samples were obtained from blood drawn by field veterinarians in southeastern (rectangle, 195 farms) or southwestern (square, 14 farms) areas in 2012. The area represented by the rectangle is centered on the village of Béthomont (50°08′N, 5°65′E) and measures ≈150 km from north to south and 100 km from east to west. Areas C (center), E (east), and S (south) refer to 3 distinct spatial clusters within the area represented by the rectangle. The area represented by the small shaded square is centered on the village of Taintignies (50°54′N, 3°34′E); each side measures ≈20 km.