Johnes Disease - Don't Ignore It!

We are all involved in an industry that is undergoing continual change. When I commenced veterinary practice more than 20 years ago I had no idea that we would be routinely visiting herds of over 400 cows. When cell counts were first available, few of us realised how large a role they would play in everyday management of the herd.

Attitudes of the farming community to Johnes Disease have undergone a significant change over the last few years and without doubt will undergo significant change in the very near future.

It is now rare to see any group of cattle sold without a reference to the JD status of the herd.

Dairy manufacturing companies are beginning to receive orders for product that is sourced from animals that are free of diseases such as EBL and JD.

The majority of people purchasing cattle are now asking for an indication of the JD status of the cattle they intend to buy. Anyone who is selling cattle needs to be able to provide information indicating whether or not their herd is likely to be infected.

At the moment there are three broad groups of herds.

  1. JD Market Assurance Herds
    These herds have undergone a voluntary assessment that includes testing of the whole herd. They conduct strict control measures and have a nil or very low risk that any cattle are infected. There are two dairy herds in Western Victoria in this category.

     

  2. Known Infected Herds
    1. Control Program Herds:
      These herds conduct control measures of varying levels on farm but do not test.
    2. Test and Control Herds:
      These herds have audited control programs and do annual whole herd tests. A number of these herds have a very low prevalence of disease and groups of animals within the herd are of very low risk of being infected.

     

  3. Non-Assessed or "No Known JD Herds"
    This includes the majority of herds. Some of these herds are JD free. It is also certain that a lot of these herds are infected, mostly without the owners knowledge. We continue to diagnose JD in these "No Known Johnes" herds.
JD is a slowly developing disease and can be present for a number of years before it makes itself apparent. As the test and control program progresses we are finding a significant number of infected cows in these herds that have been introduced from "No Known JD Herds". The good news is that JD can be controlled.

Diligent calf rearing practices alone will control JD in the majority of herds. Next year an official program, probably called "The Calf Accreditation Program" or CAP will be introduced. This program will be voluntary and producer funded and will be available for very low prevalence of JD, or non assessed herds.

The program consists of:

  • The herd owner/manager establishes a set procedure for rearing of replacement calves. This procedure will implement the known disease control measures for JD.
  • The program will be documented and monitored to ensure no "short cuts" are taken.
  • External auditing will be undertaken to provide confidence for intending purchases.
If JD is present at a low level in these herds, the CAP will minimise spread to other cattle.

If JD is inadvertently introduced into a herd on the program, spread to other cattle will be minimised.

What if your herd is already infected with JD?

A diligent calf rearing program is essential to reduce the continued infection of young calves. We strongly advise anyone who has JD in their herd to reassess their calf rearing practices and to implement an effective disease control program. This is particularly important if you intend to sell cattle for breeding purposes, eg at a dairy sale, within the next few years.

Summary

  1. JD can be controlled.
  2. The ability to sell cattle for their true value in the future will rely on purchasers being confident of the JD status of the herd and property.
  3. This can only occur if active steps are taken to control the disease; document the methods used and monitor their effectiveness.
  4. Anyone who wishes to set up and effective program can contact one of our JD accredited vets.


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