Johne’s Disease in Cattle
Animal Health Australia (AHA) coordinates industry-funded projects to manage Johne’s disease (JD) in cattle. Our projects work to protect Australia’s favourable JD status and reduce the impacts of the disease and its control measures on the livestock industries.
About the disease
JD is an incurable bacterial infection that may cause serious wasting and chronic diarrhoea in cattle. It also affects sheep, goats, camelids and deer in Australia.
Cause of JD
JD in cattle is caused by the bacterium, Mycobacterium paratuberculosis, which lives mainly in animal intestines, but can survive in the outside environment for several months.
M. paratuberculosis infection causes the intestinal wall to thicken and reduces the normal absorption of nutrients from grazing. An infected animal can eventually starve to death.
Although multiple strains of M. paratuberculosis exist (cattle, sheep and bison strains), it is now recognised that these are able to infect a variety of ruminant species.
Cattle infected with JD excrete the bacteria in their manure. The bacteria contaminate pasture and watercourses, spreading infection to other cattle sharing the same paddocks or yards.
Clinical signs and symptoms of JD in cattle
Most cattle are infected as calves but often do not show any symptoms of JD for many years. They are likely to excrete the JD bacteria before developing clinical signs.
The numbers of infected cattle in a herd may start out low, but the rate of infection can increase significantly if it is not controlled. In addition to the risk of spreading the disease, visibly sick and dying animals can cause animal welfare issues and reduce enterprise production.
The most common signs of JD in cattle are:
- chronic diarrhoea (scouring)
- eventual death.
Not all infected cattle show these signs; some just fail to reach their full productive potential.
First signs of JD in dairy cattle are:
- a drop in milk production
- then weight loss and—in most cases—scouring.
This would occur even though you are feeding the cattle well. Bottle jaw (soft fluid swelling under the lower jaw) can also be seen in the early stages.
The first likely sign of JD in beef cattle is weight loss, with or without concurrent scouring.
Why JD prevention and management in cattle are important
Introduction of JD into a cattle herd can severely impact on a business, especially a breeding enterprise. A seedstock producer’s reputation could be damaged if animals sold are subsequently found with JD infection.
Prevention through biosecurity practices is a sound investment because JD in cattle is difficult to eradicate from an infected herd.
JD in cattle enters a herd through the introduction of infected animals, either by purchasing or agisting infected stock.
M. paratuberculosis bacteria are resilient and can live for a long time in the environment. Research in southern Australia showed that heat and sunlight destroyed the bacteria; under normal summer conditions in paddocks and waterways, around 90% of the bacteria die within 6 weeks. But in moist, shaded conditions, the bacteria can survive for longer than 12 months.
Australia’s low prevalence of JD in beef herds is recognised internationally. Large parts of Australia and the majority of Australian beef cattle herds are free of JD, so it is worth continuing to protect this desirable animal health status and reduces the risk of disease spread.
Taking no action to manage and maintain the very low levels of infection in Australian beef herds could undermine Australia’s reputation as an exporter of premium beef products.
Several of Australia’s major markets and competitor countries require certification for JD status of live animal exports, so infected herds could be excluded from particular markets that require certification of absence of disease.
A range of tools are available to producers to help them manage and prevent JD.
- JD factsheets and publications
- JD diagnosis and testing
- JD spread and prevalence
- Disease movement requirements for livestock
- Johne’s disease coordinators in Australian states and territories