Keeping bovine Johne’s disease off your property

Introduction

Bovine Johne’s disease (BJD) is a chronic, incurable wasting disease in cattle. The disease has been slowly spreading since it was first recognised in Australia in Victoria in 1925. Recent figures indicate that in December 2002 there were about 1150 infected herds in Victoria, 136 in New South Wales, 51 in South Australia and 11 in Tasmania. ‘New’ detections are continuing.

There is little doubt that there are infected herds in some areas that have not yet been detected, so these figures underestimate the real numbers.

Some countries, including the United States and New Zealand, have been unable to effectively deal with Johne’s disease once it has become widespread. As the prevalence of the disease within each herd increases, significant economic losses start to occur. Management practices are different in these countries, and the path that this disease will follow in Australia is hard to determine. In Australia, because the overall prevalence of BJD is not yet high, we still have the opportunity to keep this disease under control if we put a strategy in place now to prevent its spread.

Within New South Wales at this stage, the great majority of herds are almost certainly not infected.

Could my herd already be infected?

The herd is probably not infected if:

• the herd is basically ‘closed’;
• there have been no introductions of dairy cattle or dairy goats;
• purchases have only been from a few herds with a reliable history, or from low-risk areas such as Queensland and western and north-western New South Wales;
• there is little chance of strays, or drainage, from possibly infected neighbouring properties, especially dairies, or travelling stock.

The herd may be infected if:

• there have been occasional cases of chronic scouring that were not due to the usual causes;
• the herd has received introductions from high-risk areas, especially dairy cattle from Victoria or Tasmania;
• neighbouring cattle or goat herds have been infected for a long time, and fences are not stockproof;
• there has been a lot of drainage coming onto the property from high-risk neighbouring properties.

Your herd is more likely to be infected if it is a dairy herd rather than a beef herd.

Protecting clean herds

Bovine Johne’s disease does not spread as readily as the sheep strain of the disease. Nevertheless, BJD is slowly spreading. There are a number of commonsense strategies for protecting clean herds from infection:

• Do not send cattle (especially those younger than 12 months) away on agistment, to shows, to artificial breeding centres or to rearing/preparation centres, and then bring them home — unless you are sure they will not be mixing with infected cattle while away. A good policy would be to follow the Beef Only rules when assessing and managing the risks involved in agisting cattle.
• Maintain boundary fences in good condition. Keep an eye out for straying stock, and check fences regularly for the presence of breaks, especially at floodgates and public road gates. Direct contact with infected animals and their faeces through straying is far more likely to expose cattle to an infectious dose of bacteria than exposure to runoff.
• Water running off areas of high cattle concentration (such as feedlot areas, cattleyards, dairy milking bails) can carry infection. Take steps to divert any such runoff; on high-risk boundaries, consider constructing a timber belt with double-fencing. Keep the most susceptible stock (calves younger than 12 months) away from those boundaries that present a risk from neighbouring cattle or runoff.
• Only buy cattle when you have some assurance that they are not infected with Johne’s disease. This applies especially to breeders that you will retain for some time; it is not as important for short-term young trade cattle.
• Wherever possible, check out the ‘credentials’ of the property of origin.
• Wherever possible, purchase cattle from gazetted low-risk Protected Zones.
• Do not buy cattle from a Control Zone unless the herd is certified under the Australian Cattle Johne’s Disease Market Assurance Program, or the cattle are from herds qualified as Beef Only or BC-TAS. (See also Order of risk of buying stock in Bovine Johne’s disease (BJD) zoning.)
• Insist that truck drivers pick up stock with a clean truck when they are carting replacement stock to your property.

An explanation of the usage of the terms ‘Zone’ and ‘Area’ is given below.

Market Assurance Program

The Australian Johne’s Disease Market Assurance Program for Cattle (CattleMAP) provides a sound, standardised basis for assuring that herds have a low risk of being infected. This assurance is provided by combining negative testing of the whole herd (rather than just a few head) with management practices to reduce the risk of introduction of disease.

Vendor declarations give some assurance, and you can now ask for a specific Animal Health Statement in relation to BJD, but sometimes the owners of a herd are not aware that their herd is infected.

Breed societies and special breed sale organisers are in a position to look at the options for making enrolment in the Market Assurance Scheme a necessary requirement for membership or participation. The ARCBA-BIAA (Australian Registered Cattle Breeders Association / Beef Improvement Association of Australia) Seedstock Code of Practice is taking a lead in this issue by requiring declaration of a herd’s Johne’s status and by making it desirable for the herd to be enrolled in the Market Assurance Program.

Try to purchase your restockers from herds that are entitled to display the approved sign shown at right. You can search the AHA database.

For more information, contact:

• your local Rural Lands Protection Board (RLPB)
• NSW Department of Primary Industries (NSW DPI) office
• your private veterinarian
• NSW DPI Technical Specialist (BJD), Sally Spence, phone (02) 6391 3630.

Note: ‘Protected Zone’ and ‘Control Zone’ are the terms used in this document to refer to the areas named under the NSW Stock Diseases Act 1923 as ‘Protected Area’ and ‘Protected (Control) Area’ respectively. Other states refer to these areas as ‘Zones’ — it is only in NSW that they are called ‘Areas’.

Acknowledgment

The assistance of RLPB Veterinarians Dan Salmon and Keith Hart is appreciated.