Johne’s programmes within AFBI Cattle Health Scheme
Agent/cause
- Bacterial infection caused by Mycobacterium avium subspecies paratuberculosis (MAP).
Disease
- Chronic, progressive wasting and scour in adult cattle.
- High rate of wastage in heavily infected herds at three to five years of age.
- MAP is shed in large numbers in faeces and can also be found in colostrum and milk.
Introduction and spread
- Usually introduced by purchasing infected replacement breeding stock, including bulls.
- Cattle are usually infected by mouth early in life from milk or a contaminated environment, although disease does not normally occur until at least two years of age. Infection prior to birth can also occur.
Impact
- Production losses.
- Early culling.
- Negative impact on cattle sales (especially bulls).
- MAP has been linked to Crohn's, a human bowel disease, although no direct link has been proven. Food Standards Agency and the Department for Environment, Food and Rural Affairs (DEFRA) advise that measures should be taken to minimise the numbers of Johne's Disease organisms that enter the food chain, with current strategies focussing on milk.
Control programme
- Testing programmes based on blood, milk and faeces samples.
Screening and eradication
- Biosecurity to avoid reintroduction
- Repeated negative tests at annual intervals allow herds to be categorised as free from Johne's disease.
- The slow nature of the infection means that eradication from affected herds can be a long process. It is important to identify and protect uninfected herds to maintain their disease-free status.
- Tests on blood and faeces only reliably detect infection in the later stages of the disease, when clinical disease has become apparent, or shortly before. Therefore, infected animals may test negative on several occasions at annual tests before they test positive. Testing individual animals is therefore of very limited value, although the tests are very useful as an indicator of herd infection.
- Removal of offspring of any positive dam from the breeding herd as these are at particularly high risk of developing the disease
- Good hygiene and control of colostrum.
