Johne's (pronounced "Yo-nees") is a disease caused by a bacterium called Mycobacterium
Avian subspecies Paratuberculosis (MAP for short!). This is a chronic, contagious disease affecting all ruminants. Many wildlife species transmit the infection however. It is thought that up to 30% of all herds in the UK are infected with Johne's, causing a huge financial loss to some farmers.
Animals will acquire the infection as calves in one of three ways:
- Through the placenta
- Through the colostrum and milk from an infected cow
- Through faeces by suckling on dirty teats or being born in a dirty calving box
Although the infection is acquired as calves, the disease has a long incubation period and cattle don't generally show signs of disease until they are 3-5 years old or more.
The bacteria embeds itself in the wall of ileum (part of the small intestine). Here, the bacteria multiplies slowly causing thickening of the gut meaning it is less able to absorb nutrients from the diet and leads to leaking of important proteins. Over time this results in 'pea-soup' diarrhoea, weight loss and a milk drop. Animals with chronic disease may also develop a fluid swelling under the jaw, known as 'bottle jaw'. Any stressful event can bring on the signs of disease e.g. calving, movement, concurrent disease and poor nutrition.
Making a diagnosis of Johne's can be difficult if the animal is not showing signs of disease and shedding the bacteria. Tests available include faecal sample, blood sample and biopsy. We will usually take a faecal and blood sample to increase our chances of finding the bacteria if it is present.
1. Test and Cull
To become Johnes free accredited this is the only option involving testing of all breeding stock more than 24 months old, annually. Positive animals and their offspring are culled/fattened. Since the tests used for making a diagnosis 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 be confirmed. (i.e. 3 annual tests which show the whole herd to be negative).
- Rapid culling of known positive animals
- CALVING HYGIENE clean calving boxes and sheds - This is of the utmost importance
- In Dairy units - removal of the calf before suckling and feeding only it's dam's colostrum by bottle or tube. If you know the mother to be Johnes positive, feed the calf known "clean colostrum (from a cow older than 6 who is unlikely to be infected if in good condition and has no scour) to try to minimise the risk of infection via this route.
NEVER FEED POOLED COLOSTRUM TO HEIFER CALVES LIKELY TO BE KEPT FOR BREEDING!!!
- Do not feed waste/dump milk to calves
- Prevent faecal contamination of feed and water by raising feed and water troughs, strip grazing in the summer and using piped/mains water rather than ponds or streams
- 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 Johnes free herds
There is no current UK vaccine, although a vaccine can be imported. The vaccine will not
eradicate disease but will reduce the number of clinically affected animals. The main problem is that vaccination may cause animals to test falsely positive at their TB test.