Abstract

This paper summarises current knowledge of Johne`s disease (JD) in farmed deer in New Zealand and discusses prevention and control options. JD in deer is caused by "bovine strains" and "ovine strains" of Mycobacterium avium subsp. paratuberculosis. Two clinical syndromes are recognised; sporadic cases in mixed age deer and serious outbreaks, affecting up to 15% of groups, in 8 to 15 month old deer. Over 300 deer farms are known to be infected and the number is increasing. Studies have shown that the gel diffusion test is the most reliable test for confirming JD in clinically affected deer. However, none of the currently available serological or cell-mediated immunological tests is sufficiently sensitive or specific for detecting subclinical paratuberculosis in deer. Farms free of JD should prevent its introduction. Control options on infected deer farms are limited to management options: culling affected stock, culling test-positive animals or depopulation and restocking after 2 years. Vaccination may be the most cost-effective long term control option if a suitable vaccine can be developed. A voluntary market assurance programme for deer farms has been proposed, but implementation depends on the benefits to farmers and on the national deer farm JD prevalence being low enough to warrant it.

CG, Mackintosh

Proceedings of the New Zealand Society of Animal Production, Volume 62, Palmerston North, 303-306, 2002