JD spread and prevalence
Animal Health Australia (AHA) coordinates the national Johne’s disease in cattle project on behalf of Australia’s beef and dairy industries.
How Johne’s disease enters the herd
Johne’s disease JD enters a herd through the introduction of infected animals, either by purchasing or agisting infected stock.
Animals usually become infected at a very early age. They pick up the infection as they eat or drink from contaminated pastures, water and udders, or drink contaminated milk from infected cows.
When pasture contamination levels are high, older animals may become infected.
Some infected animals can shed billions of bacterial organisms in their dung each day.
Figure 1: How cattle become infected with bovine Johne’s disease
How prevalent JD is in Australia
Johne’s disease was first identified in the late 19th century. In Australia, JD was first recorded in a quarantined imported bull in 1911. The first detection in Australian-born cattle was in a Victorian dairy herd in 1925.
Up until June 30th 2016, approximately 1150 cattle herds had been classified as infected in:
- New South Wales
- South Australia
JD is most common in dairy herds, but it also occurs in beef cattle, goats and alpacas. The first case of JD in deer was detected in Victoria in 1999.
There are relatively few beef herds infected with JD in Australia, but the disease occurs more frequently in the southern beef enterprises. The west and the north of Australia is relatively free of JD in cattle.
How to minimise the risk of introducing BJD
To minimise the risk of JD infection source cattle from herds that can demonstrate a low risk of being infected when introducing new animals:
- herds that have tested negative
- higher Johne’s Beef Assurance Score or Dairy Score cattle