Producers, veterinarians, agents, carriers and others in the cattle industry should familiarise themselves with the New Approach to JD in cattle.
What is Johne's Disease (JD)?
Johne's Disease (JD) is a chronic, incurable bacterial disease of cattle, goats, alpaca and deer and sheep. It is caused by Mycobacterium paratuberculosis.
Infected animals scour, lose weight, and die. Essentially, the intestine walls thicken and that prevents the normal absorption of food, thereby causing the animal to starve.
There is no cure for JD.
In Australia, JD is much more common in certain sectors such as dairy herds than in others such as beef herds.
What is the difference between strain types of JD?
There are separate strains of Johne's Disease. bovine JD is generally caused by the cattle ('C') strain of the bacteria and ovine JD is caused by the Sheep ('S') strain of the bacteria.
It is possible for sheep to become infected with C strain and for cattle to become infected with S strain, however this is very rare. Cattle producers who graze cattle with sheep need to be aware of the risk that S strain poses to cattle.
There is a vaccine available to help manage S strain JD in sheep. There is also a vaccine available for C strain JD infected cattle herds The C strain vaccine is available under permit and there are conditions regarding its use. Contact your vet for further advice.
Why is JD a problem?
As JD is, essentially, a starving disease, there are significant animal welfare issues as the disease progresses. Even sub-clinical disease can have an impact on milk production and animal growth.
Ongoing freedom from JD is important for producers that want to export cattle to the mainland or internationally.
If JD is allowed to spread widely throughout Tasmania's beef industry, it will tarnish the Tasmanian brand for the Tasmanian beef cattle industry as a whole.
What causes JD?
JD is caused by bacteria called Mycobacteria paratuberculosis (sometimes shortened to Mptb). This bacteria can survive outside the cow or sheep for a long time. In ideal conditions, such as boggy or wet areas of a farm, it may survive for 12 months or more.
What does JD look like?
Cattle are infected, usually in the first few months of life and rarely after 12 months of age. However, an infected animal often does not start showing signs of infection until it is 4 or more years old, though cattle can show clinical signs as early as 2 years of age.
In dairy cattle, the first sign you are likely to notice would be a drop in milk production. If you miss that sign, the next signs would be 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.
In beef cattle, the first sign you are likely to see would be weight loss. There may or may not be scouring at the same time.
If you see these signs in an animal 2 years of age or older*, you should consider the possibility of JD. You should straightaway get your vet to check the affected animals and take appropriate samples for testing. Most situations can be resolved if action is taken promptly.
(* There have been rare cases of the signs being seen in cattle less than 18 months old)
How is JD spread?
In most cases, JD is spread from farm to farm and from region to region by the movement of infected cattle. That is, infected cattle being brought into a herd that was previously JD-free.
Faeces of an infected cow contains the bacteria Mycobacteria paratuberculosis. Where pasture is contaminated by faeces from infected cattle, goats, deer or alpaca, susceptible animals (in particular calves up to12 months old, but also deer, alpacas and goats of any age) grazing it are exposed to the bacteria in sufficient quantity to become infected. Contaminated water sources can also infect cattle.
It is possible for infected cattle on one farm to contaminate the water supply for cattle on other farms downstream. However, it is thought that long distance spread by this means is unlikely.
How do I minimise the risk of JD in my herd?
There are some National JD programs and tools provided by the dairy and beef industries to help you reduce the risk of this disease.
- The National Dairy BJD Assurance Score can help you identify the level of BJD risk in dairy cattle you are contemplating buying or agisting onto your property. The score ranges from 0 to 10, and the higher the score the lower the risk. For more information about this, visit the Animal Health Australia website. In short, calculate your own score and buy or agist only those cattle that have the same or a higher score.
- The 3 Step Calf Plan and the Johne's Disease Calf Accreditation Program (JDCAP) can help by minimising the risk of JD spread from adult cow to calf. For more information about this, visit the Dairy Australia website
- Available on the AHA website, are the following tools for producers to manage and prevent JD in their cattle.
- AHA is also regularly updating its webpages – New approach to JD in cattle and JD in cattle tools.
- CattleMAP has ceased, former cattle MAP herds may transition into JBAS.
What should I do if I suspect JD in my herd?
If you have any persistent scouring or weight loss in your herd, or otherwise suspect JD, contact your vet promptly and discuss your situation. Your vet may then take samples for testing.
You are required by law to report any suspicion of JD to DPIPWE. Your vet can do this on your behalf.
Please note that infected or even suspect properties are NOT placed under quarantine. The only restriction placed on farmers with an infected or suspect herd is that any potential receivers of cattle from such herds must be informed of the herd's JD status. The best way to do this is by completing a National Cattle health Declaration.
What are the JD tests?
JD tests detect the actual bacteria or the body's response to their presence. Animals are tested in two stages - screening tests of the whole herd or a large proportion of it and follow-up tests of reactors.
There are four types of screening tests available to test for JD in live animals.
What are my management options if my herd is infected?
It is most important that producers with a JD-infected herd have an on-farm management or eradication program and that they involve a vet who is very familiar with Johnes Disease in that process.
Johne's disease is difficult to eradicate from a farm. It is much better to avoid the disease through sensible purchasing decisions and careful biosecurity planning than to try to eradicate it. Every property disease control program should be based on a comprehensive animal health risk assessment - and a vet who is very familiar with Johnes Disease is the person best placed to help you complete this assessment and develop the most effective program for your herd.
The management and control options are quite different for dairy and beef herds. This is because dairy herds are yarded and handled much more frequently, are grazed more intensively and this means that the risks of disease spread are greater, however there are more options for control with regards to hygienic calf rearing herds.
Control in a dairy herd
JD resistance develops with age in cattle and cattle over 12 months old are unlikely to become infected. Further, infected cattle under 2 years of age rarely shed sufficient bacteria to spread the disease. These "circuit breakers" can be incorporated into an on-farm JD management program. The three key features of a JD on-farm management program for a dairy farm are
- Dairy hygiene
- Rearing heifers offsite on pasture not grazed by adult dairy cattle in the last 12 months, away from other dairy cattle, and away from dairy cattle effluent.
- Culling all animals testing positive
There is a lot of good information on the Animal Health Australia BJD Website.
Control in a beef herd
JD resistance develops with age in cattle and cattle over 12 months old are unlikely to become infected.Further, infected cattle under 2 years of age rarely shed sufficient bacteria to spread the disease. These "circuit breakers" can be incorporated into an on-farm JD management program.
- Minimising new infections (in particular, protecting calves born on-farm from sources of infection)
- Avoiding the introduction of infected animals (ie sourcing low risk animals)
- Decontamination strategies completed in advance of susceptible animals grazing that area. (ie grazing a paddock that you intend putting calves on the following year with young steers under 2 years of age that are intended for slaughter; or growing a crop on that area, followed by new pasture to put susceptible stock on.)
Destocking breeding animals from an infected property is an option for eradicating JD. However, it is unlikely to be an attractive option for many producers because the destocking would have to be long term to be effective. If you are considering this option, you should consult your veterinarian.