Johne's Disease

The bacterium (M. paratuberculosis) which grows in the intestine of infected animals, causes damage which reduces the efficacy of nutrient absorption resulting in chronic weight loss.

Signs of Johne’s include:

• Chronic weight loss
• Persistent ‘tail’ in mobs that doesn’t respond to drenching (sheep)
• Diarrhoea (more commonly in cattle)
• Drop in milk production (cattle)
• Emaciation
• Death
• In a flock or herd there may be only a few animals with clinical signs but production losses will be occurring in many more.

The disease has a long incubation period, taking over a year before clinical signs become apparent after infection. Despite this, infected animals can be shedding the bacteria before clinical signs are noticeable.

If you suspect Johne’s disease you must notify either Local Land Services (1300 795 299) or the Department of Primary Industries (animal.biosecurity@dpird.nsw.gov.au) within one working day.

A veterinarian can investigate suspect cases of Johne’s disease and provide advice on management specific to your property.

Remember, you have a biosecurity duty to prevent the spread of diseases, such as Johne’s, from your animals to anybody else’s animals.

Diagnosis of Johne’s disease is suggested by history, gross pathology and serological and/or molecular testing, and is confirmed by histopathology with special stain (Zeihl-Neelson) and isolation of M. paratuberculosis from faeces or tissues by culture.

There are a wide range of tests available on blood, faeces, fixed and fresh tissues. The selection of diagnostic test will vary depending on the individual circumstances, purpose of testing and required turn-around times. 

Available diagnostic tests and laboratory submission forms

Infected animals shed the bacteria in faeces, colostrum, and milk. The bacterium which causes Johne’s is very persistent, with the bacteria able to survive in the environment for over 12 months which is one factor making it a difficult disease to eradicate.

Infection is most commonly acquired in young animals through contamination of the environment or ingestion of contaminated milk. It can also be transmitted from an infected pregnant animal to its foetus.

A non-infected flock or herd generally becomes exposed through expansion or replacement purchases of animals that are carriers of the disease. Adult animals that are exposed are much less likely to become infected; however, young animals are highly susceptible.

Johne’s disease/paratuberculosis has not been demonstrated as a zoonosis. However, the organism that causes Johne’s disease (M. paratuberculosis) has been found on occasions in patients with Crohn’s disease. Crohn’s disease is a chronic, painful, diarrhoeal inflammatory disease of the intestinal tract in humans that resembles Johne’s disease. (Source: https://www.woah.org/en/disease/paratuberculosis/)

Anyone who suspects they might have a zoonotic disease should contact their doctor or NSW Public Health (1300 066 055)

Prevention and management

On properties without JD, measures should be taken to prevent entry of the disease. On properties with JD, measures should be undertaken to minimise the risks posed by the disease.

• Implement strong farm biosecurity to prevent entry of JD
• Always request a National Health Statement such as a National Cattle Health Declaration or National Sheep Health Declaration from the vendor when purchasing or agisting susceptible animals
• Only purchase of agist animals at low-risk of JD infection
• Consider the use of vaccine to prevent or manage JD infection
• Consider the role of grazing management to minimise potential exposure of susceptible animals to M Paratuberculosis
• Cull any animals showing signs of JD. This is important on welfare gorunds and it also helps to reduce contamination of land.

Vaccination against Johne’s disease is available for sheep and goats (Gudair) and cattle (Silirum). Neither vaccination is a silver bullet but they are useful tools in the prevention and management of JD in Australia. In NSW, Silirum^® Vaccine can only be supplied on the authority of the NSW Chief Veterinary Officer to approved people or their approved veterinarian. To apply for an authority, print and follow the instructions on the Application and authority to use Silirum® vaccine in NSW.

Australia also has Johne’s Disease Market Assurance Programs (MAPs) which are voluntary programs for Alpaca, Sheep and Goat producers to identify animals with a level of assurance of their Johne’s disease status. General information on these programs can be found at Animal Health Australia – Market Assurance Programs and for information on their administration in NSW - Market Assurance Programs (MAPs) administration.

The Australian beef industry has a low level of JD and uses the Johne’s Beef Assurance Score (J-BAS) as a risk profiling tool. The dairy industry has a higher level of JD and uses the JD Dairy Score (JDDS). Further information on these scoring systems can be found at Animal Health Australia – Johne’s disease in cattle.

Resources

• Form - Application and authority to use Silirum® vaccine in NSW
• Animal Health Australia – Johne’s disease
• Definitions and guidelines - Johne’s disease in sheep and goats
• Definitions and guidelines – Johne’s disease in cattle
• WOAH – Paratuberculosis

Coming soon.