Development of vaccines for Johne's disease in sheep

Abstract

Extract

Johne's disease of sheep in New Zealand was first reported by Williamson and Salisbury (1952), who confirmed its presence on a sheep property in the South Canterbury district of the South Island. Armstrong (1956) has since reported the disease occurring on 15 further properties in South Canterbury and Ashburton county. Armstrong states that there is no evidence of the disease having suddenly appeared and spread to all these properties in the last few years; history suggests that the properties have been infected for several years, but the mortality on most farms has been so low that little interest has been shown. The incidence of the disease in affected flocks is usually low, but has been as high as 5 per cent, of breeding ewes on one property.