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Foot-and-mouth disease
Since its first detection in Australian sheep in the 1980s, Johne’s disease (JD) has posed a significant challenge to the sheep industry, costing millions in production losses and preventative measures each year.
JD is a chronic wasting disease affecting cattle, sheep and goats. Infections are caused by the bacterium Mycobacterium paratuberculosis, which mainly lives in animal intestines but can also survive in the environment for several months.
These bacteria cause a thickening of the infected animal’s intestinal wall, reducing the normal absorption of food. The animal is hungry and eats but can’t absorb nutrients, and as a result, it slowly wastes away and dies.
JD in sheep is primarily passed on through faeces, with young animals being the most susceptible.
JD’s long incubation period, lack of early signs, ability to survive in the environment, and silent spread make it a difficult disease to prevent and manage.
Dr Rob Barwell, Head of Program, Biosecurity at Animal Health Australia (AHA), highlighted the importance of an integrated biosecurity approach to prevent and manage JD.
‘Property managers need a flock disease management program that considers their unique flock disease and risk status.’
Understanding your flock’s risk of exposure to JD is essential to developing an effective management plan. The first step is remembering that JD is typically introduced through the purchase or agistment of infected sheep.
‘It’s a buyer-beware market,’ said Dr Barwell. ‘Ultimately, it’s up to you to ensure the animals you’re purchasing are healthy and productive. That’s why we recommend requesting a National Sheep Health Declaration every time you buy or agist livestock. It gives you a much clearer idea about their history, any testing carried out, whether they are part of an assurance program and their vaccination status. This can help identify and manage potential risks before animals enter your property.’
Additional measures, such as grazing management, fence maintenance and isolating straying stock, can also help protect flocks and minimise bacterial contamination.
Dr Barwell believes vaccination is also an important tool for managing JD in a flock.
‘Vaccination against JD is essential for maintaining the health and productivity of sheep flocks in areas where JD occurs, which is much of southern Australia,’ said Dr Barwell.
‘It doesn’t prevent infection entirely, but it has been shown to significantly reduce the level of clinical disease, decrease mortalities, and delay and reduce the shedding of bacteria. This reduces environmental contamination and provides less opportunity for disease transmission.’
Currently, Gudair® is Australia’s only vaccine for the control of Johne’s disease in sheep. This vaccine is administered as a once-only injection to lambs before they reach 16 weeks of age.
Dr Barwell says it’s vital that producers don’t underestimate JD’s long-term impact on flocks. Prior to the vaccine becoming available, annual death rates in infected flocks had been as high as 25%, with some self-replacing lambing percentages falling to unsustainable levels.
‘Over the last year or so, we’ve heard that the number of flocks vaccinated against JD has decreased. The difficulty with JD is that it spreads slowly and is often undetected for quite some time before it starts to cause obvious losses. Once detected, it’s usually well established, and it can take a long time to manage and control the disease.’
‘I encourage all sheep producers to remain proactive when it comes to vaccination against JD. Besides enhancing animal wellbeing, healthy flocks are more productive and have fewer losses. By protecting your sheep, you’re also protecting your livelihood.’
For more information about managing JD in flocks, visit Animal Health Australia.
For details about Gudair, visit zoetis.com.au
