Ovine Johne's disease

Page last updated: Wednesday, 4 May 2016 - 11:17am

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Ovine Johne's disease (OJD) is a serious wasting disease that affects mainly sheep, and to a lesser extent goats. It is caused by the sheep strain of the bacteria Mycobacterium paratuberculosis. The bacteria affect the intestines, preventing absorption of nutrients, and the bacteria are shed in the faeces of infected animals.

Sheep infected by the OJD bacteria may take three to six years to show signs of the infection. Once the disease is seen, affected sheep progressively lose condition and die over a six to 12 week period. Scouring may also be seen.

The disease

The OJD bacteria can survive for up to 12 months on shaded pasture or up to 24 months in water. Young sheep are particularly susceptible to becoming infected when they come into contact with infected faeces on teats, pasture or water.

Sheep infected by the OJD bacteria may take three to six years to show signs of the infection however once the disease is noticed, affected sheep lose condition despite adequate feed and parasite control, and usually die within a 12-week period. Scouring may be seen but is not always present.

Clinically normal sheep may actually be infected with OJD and can be shedding the bacteria in their faeces.

National OJD management plan

The national sheep industry has a National OJD Management Plan 2013-2018, which is coordinated by Animal Health Australia. The plan funds inspections in abattoirs around Australia. These inspections are used to estimate the prevalence of OJD in regions, and the risk of sheep in different regions and states being infected with the disease. The estimate of OJD in Western Australia (WA) is currently less than 5%, although this varies between areas. State prevalence is reviewed nationally every two years.

The Department of Agriculture and Food, Western Australia (DAFWA) advises owners of flocks identified as infected at abattoir inspection, and encourages them to contact their private veterinarian or farm consultant to develop a property disease management plan to manage the disease.

There is no regulatory control of OJD-infected flocks in WA.

Vaccination

Vaccination for OJD can be an important management tool. It can reduce the number of sheep showing signs of infection by 90% and greatly reduce the number of sheep that shed the infection in their faeces.

Movement of sheep

Completing a National sheep health statement (SHS) is not mandatory when buying or selling sheep in WA. However, DAFWA advises its use whenever buying or selling sheep, as it is an important risk management tool.

An SHS is required to accompany consignments of sheep being moved to some states in eastern Australia.

How to provide greater assurance on the SHS

There are four ways to provide greater levels of assurance about OJD on the SHS:

  • negative abattoir inspection results
  • negative flock testing using pooled samples of faeces
  • vaccination as set out in the SHS
  • entry into the sheep market assurance programme (SheepMAP).

Contact information

Anna Erickson
+61 (0)8 9881 0211