Johne's disease - Part Three: The Disease in Cattle and deer

deerJohne’s disease is a particular problem in cattle and deer for several reasons.

It causes slowly progressive and incurable scouring and weight loss leading to death or euthanasia.

Infected cattle and deer are likely to give false positive reactions to the skin test for Tb.

  • Johne’s vaccine mustn’t be used in cattle and deer because vaccinated animals can give false positive reactions to the Tb skin test (although in future vaccination may be allowed for certain classes of cattle in low-risk Tb areas).

How common is Johne’s disease in cattle and deer?

  • A study in 2006 of 170 deer farms in New Zealand showed that there were infected deer on about 50% of deer farms, with varying levels of clinical disease.
  • Johne’s disease is much more common in dairy cattle than in beef cattle, and it is likely that over 50% of dairy herds are infected.

What are the signs of Johne’s disease in cattle or deer?

  • Affected animals develop runny diarrhoea and steadily lose weight over a period of weeks or months in spite of treatment and good feeding. 

What types of animal are most likely to be affected?

  • In dairy herds, the disease affects young adult cows from about 3 years of age, and it tends to affect only one or two cattle in the herd at a time. 
  • In deer, outbreaks of severe disease can occur in yearlings, and sporadic cases occur in deer from about 2 years of age. 

How can you be sure the signs are caused by Johne’s disease?

  • There are other diseases that can cause similar signs (e.g. heavy worm burdens).  Confirm (or rule out) the diagnosis by asking a vet to take blood and or faecal samples for laboratory testing.

What can I do if I have cattle or deer with the disease?

  • Develop a prevention and control programme with your vet.  This will include:
  • culling animals with clinical signs
  • blood testing all ruminants (cattle, deer, sheep, goats, camelids) or selected groups and culling test-positive animals

If you don’t have Johne’s disease on your farm, you are in a privileged position and you should try to keep your farm disease free; for example:

  • Buy only from farms where no ruminants have shown signs of Johne’s disease in the last few years.
  • Buy in only animals that have tested negative for the disease.
  • Consult your vet for more specific advice tailored to suit your farm.

How long can the bacteria that cause the disease live in the soil?

  • The bacteria (Mycobacterium paratuberculosis) that cause the disease don’t multiply in soil or faeces once excreted from an animal.  However heavily infected pasture can remain infective for up to 6 months and in some sheltered places for up to 12 months. 

 

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