Zeil
Neelsen staining of magenta-coloured colonies of MAP in gut of a cow
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.
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
