Abstract

Control of Johne`s disease caused by Mycobacterium avium subspecies paratuberculosis (MAP) in dairy cattle has assumed significantly greater attention over recent years. The primary reasons are; possible increasing prevalence, an increase in the number of overseas control programmes, the continued scientific debate about the link with Crohn`s disease in humans, and the reported presence of MAP in commercial pasteurized milk sold in retail markets. Johne`s disease is a chronic wasting disease of ruminants worldwide. Accurate prevalence data does not exist for New Zealand. The best estimates available currently estimate the annual cost in New Zealand for dairy farmers to be between $3.8 million (based on 12% herd infection) and $31.7 million annually. It is likely that with the current control technology available the cost of control would exceed the on farm benefits, and therefore significant market access issues will have to be the basis for implementing a national control programme. For New Zealand to achieve control it is essential that the current prevalence be established and an understanding of the epidemiology within the New Zealand farming system be developed. Unlike many other diseases current tests available for Johne`s disease have low sensitivity which results in any testing programme failing to detect significant numbers of infected animals. Current areas being examined include test methods, vaccine and management practice modification. Additionally the possibility of genetic selection for resistant animals may be possible with the molecular genetic capabilities that are currently being developed in the bovine.

L, Burton, and H Voges

Proceedings of the New Zealand Society of Animal Production, Volume 62, Palmerston North, 299-302, 2002