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Johne’s disease

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Ratification Date: 03 Feb 2012

Position statement

The objectives and activities of the National Johne’s Disease Control Program are important in ongoing efforts to contain and control the spread of Mycobacterium paratuberculosis on Australian farms.

Background

Both Bovine Johne’s Disease (BJD) and Ovine Johne’s Disease (OJD) are caused by an M. paratuberculosis infection.

Historically, the diagnosis of Bovine Johne’s Disease (BJD) on farm often led to quarantine of the farm, and the diagnosis of Ovine Johne’s Disease (OJD) often led to forced de-stocking of entire flocks. Diagnosis of both these diseases still has serious potential impacts on the ability of individual farmers to trade livestock in domestic and international markets.

The Australian Veterinary Association (AVA):

  • Recognises both the real and potential impact that OJD and BJD has on the cattle, sheep, goat and alpaca industries at all levels, including:
    • the welfare effects on individual animals
    • the economic effects on farming businesses
    • the social effects on individual farmers, and
    • the potential trade implications on the industry as a whole.
  • Recognises that in many regions of Australia, M. paratuberculosis infection is endemic and needs to be monitored and controlled, and understands the importance of protecting regions of Australia that appear to be free from contamination and infection.
  • Supports the use of a range of management tools, including vaccination (sheep), hygienic calf rearing (dairy cattle), Beef Only declarations (beef cattle), and the use of biosecurity plans (all species) to minimise the risk of spread of infection between flocks and herds in endemic areas.
  • Supports the need for research into improved diagnostic testing methods, and the effects of vaccination against M. paratuberculosis in cattle.

The National Johne's Disease Control Program (NJDCP) is managed by Animal Health Australia (AHA). The principal goals of the NJDCP are to provide effective coordination of Johne's disease programs across all jurisdictions and affected industries, to protect Australia’s favourable Johne's disease status and reduce any adverse impact of the disease and subsequent control measures on the affected industries.

The catalyst for the establishment of the program related to concerns about the potential affect on food safety and public health and the possible impact on market access, brought about by evidence that there may be links between Crohn’s disease and Type 1 diabetes mellitus in humans and Johne’s disease in animals (Cossu A et al. 2011).

Currently a number of trading partners require certification of freedom from Johne’s disease as part of their country’s import protocols.

The program also aims to protect the economic and trade interests of the various domestic livestock industries through a better understanding of the disease, development of effective control and eradication strategies and establishment of market assurance programs and other tools for effective risk management. In recognition of the special needs of particular industry sectors, there are separate sub programs for the management and control of OJD and BJD in all susceptible species.

Australia is well placed internationally in that a minority of herds and flocks are affected with Johne’s disease. This compares favourably with the prevalence of disease in Europe and North America where in some regions 100% of large dairy herds are infected and the within-herd prevalence may approach 50% of animals.

Nevertheless Johne’s disease continues to spread in the sheep population in some regions of southern Australia and is common in dairy herds in south-eastern Australia. The herd prevalence remains very low in the beef and alpaca sectors since both of these sectors trade independently of the dairy sector.

Increasingly Australian livestock and livestock products are scrutinised by importing countries and the former are tested for the presence of M. paratuberculosis. Japan and the European Union have both identified M. paratuberculosis as a food safety issue and have indicated the likelihood of undertaking herd disease eradication programs to reduce the risk of entry of the organism into the food chain.

Management and control programs that use a risk assessment approach have been developed for each industry sector. These are underpinned by a number of industry specific tools such as abattoir monitoring, subsidised testing, and an emphasis on the use of health declarations and on-farm biosecurity practices. Producers are strongly encouraged to buy low risk animals and a Market Assurance Program operates to provide a pool of such animals.

In the sheep industry Johne’s disease continues to spread, causing significant production losses that impact farm profitability and the viability of the sheep meat industries. In the dairy sector producers are reporting clinical disease in young animals and the disease appears to be spreading, placing export markets for live animals at risk.

Uncontrolled spread of Johne’s disease has the potential to cause animal welfare issues for individuals and for the national livestock industries through emaciation and death of grazing stock, or during transit.

References

Cossu, A. et al. MAP3738c and MptD are specific tags of Mycobacterium avium subsp paratuberculosis infection in type I diabetes mellitus. Clinical Immunology 2011;141:49-57.

Animal Health Australia. National Johne’s Disease Control Program. Available at: http://www.animalhealthaustralia.com.au/programs/jd/jd_home.cfm. Retrieved 1 February 2011.

Date of ratification by AVA Board: 3 February 2012