When ruminants are exposed to the organism that causes Johne’s disease (Mycobacterium avium subspecies paratuberculosis) the eventual disease outcome varies.
After a few years, some animals will lose weight and become severely diseased while others can look healthy but be infected and shed the bacterium in faeces (or milk) from time to time. Others may be resistant or recover from disease (Dennis et al 2010).
One factor which influences this spectrum of disease outcomes is how each animal responds to the bacterium. Therefore understanding the nature of the immune response to infection in relation to disease outcome is important. We are studying immune response parameters, at the cellular level and gene expression, to find out which responses are important in protecting an animal from Johne’s disease. Some of our initial results (de Silva et al 2013) show that early cytokine responses can predict future disease outcomes.