Figure 1

General conceptual modelling framework of regional BVDV spread, coupling within- and between-herd infection dynamics. On the left, the within herd dynamics with health states: S (susceptible), T (transiently infected), P (persistently infected), R (recovered, with the possibility of carrying a P foetus), M (protected by maternal antibodies). Dotted arrows represent birth, red arrows represent the influence on the force of infection, and black arrows correspond to transitions between states. On the right, the between-herd dynamics: herds are connected by directed trade movements (black arrows) and neighbourhood contacts (within radius R_nb).