JDRC • FUNDAMENTALS

FUNDAMENTALS

Pathobiology studies are intended to provide an understanding of the complex interactions between the animal, Mycobacterium avium subspecies paratuberculosis (MAP), the organism responsible for causing Johne’s disease, and the environment. Methods and understanding gained through “pathobiology” studies support other JDRC research programmes.

Studies examining the immune response of the gut in dairy cattle in response to natural and experimental infection were completed in 2011. While the gut is the primary site of infection for the disease, very little has been understood about what happens there. The results indicate that there are a number of mechanisms which explain how MAP avoids detection by an animal’s immune system, so that normal responses to infection do not occur.

Advances in strain typing have shown that while there are two major types (strains) of MAP in New Zealand, type C and type S, there are at least 20 sub groups of type C and 8 subgroups of type S, adding complexity to our knowledge of the disease in NZ.

The Deer Age Susceptibility Study has been completed. This project was funded by the Foundation of Research Science and Technology for a number of years prior to the formation of JDRC. The results from the study have been published in an international journal and indicate that practical steps should be taken on farm to isolate young deer from the disease as they are most susceptible to infection.

BACK TO OUR RESEARCH

	Dr Bryce Buddle of AgResearch investigated immune responses in the gut when cattle are exposed to the organism.
	Dr Des Collins of AgResearch is applying the latest techniques for typing organisms to characterise New Zealand strains of MAP.
	Dr Colin Mackintosh of AgResearch has investigated the varying susceptibility of deer to infection as they age.

• Progress Report

(Oct 2011):
Research has been completed demonstrating mechanisms and factors showing how the immune system of the gut responds to MAP infection.

Approximately 350 samples have been examined using the strain typing system developed from 2008-2010. The results from the analysis are given in the 2011 Annual Report. Work is ongoing to refine the analysis and examine if there are obvious differences in disease outcomes that can be related strain type.