Within farms transmission model for Schmallenberg Virus

The within-farm dynamics of SBV were described by a stochastic compartmental model, which is an adaptation of Gubbins et al., 2008 and Szmaragd et al., 2009. The model includes a single host species (cattle or sheep), with the total host population divided into the number of susceptible, infected (and infectious) and recovered animals. The duration of viraemia is assumed to follow a gamma distribution. The model sub-divided into stages the infected class. The vector population is as well divided into the number of susceptible, latent (i.e. infected, but not yet infectious) and infectious individuals. To allow for a more realistic gamma distribution for the extrinsic incubation (i.e. latent) period (EIP), the latent class is subdivided into stages each of them with their on mean duration. Once infectious, midges remain so for life. Vector mortality occurs at a constant rate in all classes and is balanced by the recruitment of susceptible vectors, so that the total vector population remains constant.