Johne's disease in New Zealand: the past, present and a glimpse into the future.

Johne's disease is endemic in cattle and sheep in New Zealand and is spreading in farmed deer. - Procedures for the control of Johne's disease in New Zealand have been sporadic and often ineffective. Characterisation of strains of Mycobacterium paratuberculosis using molecular biological techniques have revealed two distinct strain types. One type has been found in cattle, goats and deer, and the other in sheep, goats and deer. Vaccination has been identified as an important method for the control of Johne's disease in New Zealand but the side effects of the current oil-based vaccines severely limit their use. There is increasing international concern that M. paratuberculosis may cause Crohn's disease in humans. Demands for food free of M. paratuberculosis would have very serious consequences for the meat and dairy industries in New Zealand and overseas. The cattle, sheep, goat and deer industries need to jointly develop a strategy for the control of Johne's disease in New Zealand.