Johne's disease is a chronic, granulomatous enteritis of ruminants and some wild-type species that is caused by infection with Mycobacterium avium spp. paratuberculosis (MAP). This inflammatory bowel disease (IBD) is characterised by a lengthy yet variable asymptomatic subclinical phase in which infected animals can transmit MAP to their progeny and herd mates. This is followed by a clinical phase characterised by chronic diarrhoea, wasting, and eventually death. The impact of Johne's disease is particularly evident in the dairy and beef industries, where significant losses due to reduced...