Figure 1. Frequency distribution of results of a competitive ELISA for detecting antibodies against bluetongue virus in serum samples from roe deer (white columns) and red deer (black columns) during the hunting seasons of A) 2005, B) 2006, C) 2007, and D) 2008, Belgium. Hunting was conducted in 30 (area 12,851 km2) of 37 (area 16,844 km2) forest districts known to contain wild cervids. The study population of wild cervids in southern Belgium (49°30′N–50°48′N) is estimated to be ≈11,000 red deer (Cervus elaphus) and ≈33,000 roe deer (Capreolus capreolus). Serum samples with a percentage negativity value (relative to the negative control serum) <66 were considered positive.