Fig. 2

Estimated total number of herds infected with bovine viral diarrhoea (BVD) virus (y-axis, log scale) in Ireland in the years following the start of the compulsory national BVD eradication programme, under differing levels of retention of persistently infected (PI) animals. Output of the Irish BVD model (FarmNet 1.0) as of 2015. For modelling details see Thulke et al. [22] or http://www.ecoepi.eu/FarmNet-BVD/. In particular note: The green line (TagRetNone): the predicted fall in total PI numbers assuming all PIs are removed from farms immediately following testing (that is, without any PI retention). Under this scenario, estimated time to eradication is 3–4 years from programme start (2016–17). The yellow line (TagRetUnlim): predicted fall in PI numbers given high levels of PI retention (that is, PI retention continues at a high level each year). Under this scenario, eradication is unlikely to occur. The black line (TagRetLim, generally obscured by the light blue line): the predicted fall in PI numbers, assuming high levels of PI retention during the first three years of the programme, but no PI retention subsequently. Under this scenario, estimated time to eradication is 6–7 years from programme start (2019–20). Three additional lines were included to test sensitivity assumptions, including: the red line (TagRetHighInf, doubling of transmission probabilities), the purple line (TagRetLowMort, doubling of survival time of PI animals) and the light blue line (TagRetNoIU, suppression of movement of animals with in utero infections)