This is a disease caused by a bacterium called Mycobacterium Avian subspecies Paratuberculosis, (MAP for short)! This disease can affect both sheep and cattle although the strains of MAP appear to be different so they may not infect each other. Many wildlife species may transmit the MAP bacteria in their faeces however so aiding spread. Symptoms are those of a severe diarrhoea, with weight-loss and there is no cure.
In the UK up to 30% of all herds are thought to be infected with Johnes.

Most animals acquire the infection as calves but don’t shown signs of the disease until they are between 3 and 5 years old, (sometimes even older). The most common way for a calf to become infected is by ingesting faeces from an infected cow eg by sucking off dirty teats or by being born in dirty calving boxes. It is also possible though for the bacteria to be present in the colostrum of the dam if she is infected or even pass to the calf whilst it is still in the womb of an infected dam.

The MAP bacterium multiplies slowly in the gut of infected animals causing it to become thickened and less able to absorb nutrients from the diet as well as leaking proteins from the blood. Classically affected animals start to show weight loss with ‘pea-soup’ diarrhoea often with bubbles in it. Any stressful event can bring on the signs of disease quicker eg calving, movement, concurrent disease and poor nutrition. Other signs that affected animals may exhibit are ‘bottle jaw’ where fluid accumulates under the chin, loss of coat pigment and reduced milk yield.

In beef herds this disease is a problem due to earlier culling of affected cows and in dairy reduced milk yields even in the early stages of disease as well as an increased culling rate. Making a diagnosis of Johnes in a cow showing signs of disease is much easier then trying to identify cows infected with MAP that are still looking healthy as the tests available are much more likely to find either the MAP organism or other signs of its presence when cows are showing signs of disease. Tests available include faecal sample, (cheap/simple), blood sample and biopsy. By taking both a faecal and blood sample we are increasing our chances of finding the organism if it is present.

Control options
1. Test and Cull

If you want Johnes free accreditation this is the only option involving testing of all breeding stock more than 24 months old, annually. Positive animals and their progeny are culled/fattened. As the tests are not perfect some infected animals will not be detected on a test, so it takes at least 2 years of finding no positives before eradication can not be proved (i.e. 3 annual tests which show the whole herd to be negative).

2. Control

• CALVING HYGIENE clean calving boxes and sheds
• Dairy units removal of the calf before suckling and feeding ‘clean colostrum’ ie from a cow older than 6 who is unlikely to be infected if in good condition and no scour
• Prevent faecal contamination of feed and water
• Don’t spread slurry and muck on grazing fields 
• Cull any positive animals or those who look like they have the disease and don’t keep their offspring as breeding replacements
• Restock only from problem free herds

3. Vaccination

No current UK vaccine, although a vaccine can be imported. Won’t eradicate disease but will reduce the number of clinically affected animals. The main problem is that vaccination may cause animals to be falsely positive at their TB test.

For more advice and an answer to any further questions you may have please contact one of the large animal vets here at Parkside.