Ovine Johne’s disease (OJD) is an incurable, infectious wasting disease of sheep that can result in significant economic losses on infected farms due to sheep deaths and lost production in meat, lambs and wool.
OJD is caused by the sheep strain of the bacterium Mycobacterium paratuberculosis, which leads to the intestinal wall slowly thickening, causing reduced absorption of nutrients from the intestine. This eventually leads to severe loss of condition – infected sheep can waste away and die.
The bacteria are passed in the manure of infected animals, contaminating pasture and water supplies and spreading infection to other susceptible sheep. Once a flock is endemically infected with OJD, it is difficult to eradicate.