Johne's disease

Mycobacterium avium paratuberculosis

There are several strains of the organism:

• cattle (also 'C' or bovine) strain, which is found in Australia – mainly in dairy cattle, but also in beef cattle, alpaca, goats, deer and camels
• sheep (also 'S' or ovine) strain, which is found in Australia – mainly in sheep and goats, but increasingly in beef cattle that have co-grazed with infected sheep in southern Australia
• bison (also 'B') strain, which has been found in a small number of beef cattle cases in Queensland.

The disease occurs worldwide. Australia has relatively little JD compared with most developed agricultural countries. It is more commonly found in southern states of Australia, and particularly in dairy cattle herds and in sheep flocks in high rainfall areas.

• Cattle
• Buffalo
• Sheep
• Goats
• Alpaca
• Llama
• Camels
• Deer

The disease can also be maintained in the environment.

The bacteria (Mycobacterium avium paratuberculosis) lives and multiplies in the small intestine and lymph nodes and is shed in the faeces. It is very slow-growing.

JD is spread by faecal excretion of the bacteria and subsequent ingestion by a susceptible animal. Animals are susceptible to infection at any age, but susceptibility is greater in juveniles, especially for cattle. Animals often do not show any symptoms of JD for many years and apparently healthy carrier animals with no signs of disease, as well as clinical cases, can shed the organism.

Bacteria can be transmitted from an infected female animal to its offspring in colostrum or milk, but more commonly from faecal contamination of the teats, udder and environment. Infected bulls, rams and other adult males can also spread infection in their faeces. Ingestion of contaminated pasture, food, milk or water can then cause infection.

Bacteria survive in faecal material and on pastures where other animals can pick up the infection. Although the bacteria live mainly in the animal intestines, they can survive in the outside environment for several months. In wet conditions, the bacteria can survive in the environment for up to 1 year.

JD has a long incubation period. Clinical disease is not usually seen until at least 2 years after infection (except in deer, which can show disease much earlier). Animals are likely to excrete the bacteria before developing clinical signs. Infection causes a thickening of the intestinal wall, which reduces normal absorption of nutrients from grazing, forming the basis for clinical signs.

Clinical signs include:

• gradual loss of weight despite a normal, or increased, appetite (wasting)
• chronic diarrhoea (scouring) in cattle but not routinely in sheep
• 'bottle-jaw' (soft fluid swelling under the lower jaw) in cattle
• drop in milk production in dairy cattle.

The progression and severity of disease may be stimulated by stress, especially nutritional stress during lactation for cows and ewes. In sheep, clinical JD typically shows as a tail of ewes that fail to recover body condition after weaning and then waste away.

Animals showing clinical signs due to JD will inevitably die.

The productivity impacts of JD vary according to stress and husbandry systems. Extensively grazed beef herds typically show lower levels of clinical JD, except in drought or under other stresses. Dairy cattle that are under greater nutritional stress and potentially exposed to high levels of bacteria have a higher prevalence of infection and higher incidence of disease. The incidence of clinical disease in sheep can be marked, especially under conditions of cell grazing.

JD risk status is a common eligibility criterion for export trade and currently for trade to the Northern Territory and Western Australia. Producers whose market success may be affected by JD should protect against entry of infection and manage any infection to prevent spread of disease.

Spread between properties is usually due to the movement of animals (either deliberate or stray), although lateral spread between adjoining properties without known animal movement is common for JD in sheep in Australia.

The highest risks of spread of JD into and within Queensland are the movement of livestock from high-risk populations interstate and from properties where infection is known or suspected.

All year round, noting that older animals, especially cattle, may be less susceptible than younger animals and there is an increased risk for dairy cattle and sheep in high rainfall areas.

Monitor your livestock for signs consistent with JD (see symptoms). If you become aware of JD or reasonably believe JD is present in an animal, you must notify a Biosecurity Queensland inspector as soon as practicable but within 24 hours.

The current national approach to JD management in cattle, the JD Framework, focuses on managing this endemic disease. The livestock industries have each developed risk-profiling tools for managing JD biosecurity risks, including the Johne's Disease Assurance Score (J-BAS) for beef cattle, the Johne's Disease Dairy Score (JDDS) for dairy cattle and the Australian Johne's Disease Market Assurance Programs (MAPs) for goats, sheep and alpaca. These voluntary tools help to identify herds and flocks with a low risk of infection.

When introducing cattle, do not just rely on a JD score. Ask further questions about JD in the herd and other species on the property from which the cattle are sourced.

There is no treatment for JD, and animals showing clinical signs inevitably die. A vaccine is available to aid protection against OJD in sheep and goats, and BJD in cattle.

Responsibility for JD in Queensland shifted in 2016 from a government program of regulatory prevention and control to property-based industry management by producers. This provides flexibility for individuals to responsibly manage JD risks according to the needs of themselves and their market chain. The national industry bodies for beef, dairy, sheep, goats and alpaca have tools and frameworks in place to help producers assess and manage JD risks. These are available through Animal Health Australia.

Producers have an obligation to do what is reasonable and practical to minimise the likelihood and impacts of JD on their property. They should work with their local veterinarian to include measures in their property biosecurity management plan to prevent or minimise the occurrence of JD. Producers introducing livestock onto their properties should also seek assurances about the health of the livestock as part of their property biosecurity management plan. One way to do this is by completing a National Cattle Health Declaration.

Find out more about your obligations to manage JD (PDF, 128KB), especially when buying and selling livestock. Read the simplified guideline fact sheet (PDF, 1.1MB).

A risk-based JD management approach commenced in Queensland on 1 July 2016. This approach provides flexibility for producers managing JD on their property and reduces regulatory burden on the industry. Therefore, the regulation of livestock entry from other Australian states and movement restrictions on JD-affected properties have been discontinued.

Infected Queensland properties are no longer placed under movement restrictions. Producers with an infected or suspect herd must manage the disease under their general biosecurity obligation (GBO).