Figure 4

Expected risk (probability) of PCVAD in the Ontario study population containing 278 herds based on a generalized additive model with a smooth bivariate term for herd locations ( P _{s(x, y)} = 0.05) and porcine reproductive and respiratory syndrome (PRRS) virus herd status ( P < 0.01). The map shows the expected risk in PRRS-positive farms as a simple linear trend with decreasing risk in the western direction.