Figure 1

Structure for a candidate state-transition mathematical model of ovine PTB, based on evidence gathered in this review. The model represents MAP infection and disease dynamics in a sheep flock in a pastoral environment. The boxes Exposed, EarlyN (early disease in the non-progressor track), EarlyP (early disease in the progressor track), Affected, Recovered and Death each represent a stage of infection/disease. Sheep exposed to MAP progress through successive stages according to the plain black arrows. The box “Pasture” represents the environment in which infectious sheep are shedding MAP (according to the dotted black arrows). The transmission of MAP is represented by the red arrows. The boxes annotated with 1 represent sheep sub-clinically infected with MAP, with no visible production effects. The box annotated with 2 represent sheep affected by MAP, sub-clinically then clinically experiencing production effects. References for the pictures: MAP bacterium [60]; histological lesions in the small intestine [22], Figures 2 and 3; Ewe and triplet lambs: [61]; dead ewe: picture credit Stefan Smith; NZ sheep pasture: picture credit primary author.