Preventing the spread of Johne’s disease within your herd this spring-calving season requires the use of control measures.
Johne’s disease is caused by the bacterium Mycobacterium avium subspecies paratuberculosis (MAP). The bacteria affects the gut of cattle, causing diarrhoea and wasting.
MAP can easily be spread from one animal to another, particularly if you feed a calf colostrum from an infected cow – which is easily done due to Johne’s disease often not showing symptoms until it is too late.
Johne’s disease
If you have the disease in the herd, infected cows should be marked for culling. If they are in-calf and due in the coming months, colostrum and milk from these cows should not be fed to calves.
If there are cows within your herd that you suspect to be infected or their dam had the disease, their colostrum and milk should also not be fed to calves.
The Irish Johne’s Control Programme (IJCP), operated by Animal Health Ireland (AHI), is developing a long-term programme to control Johne’s disease within the Irish cattle industry.
According to AHI, cattle usually become infected as calves early in life by drinking milk or eating food contaminated with the bacteria, which are shed in the dung or milk of infected adult cattle.
On occasion, calves are already infected at birth, with this being most common when their dam is in the advanced stages of the disease.
Due to their undeveloped immune system calves are most susceptible to contracting the disease.
Control measures
The best way to prevent the spread of any disease is through control measures, particularly if the disease is already on your farm.
Some Johne’s disease control measures you should consider include:
- Regular screening of your herd for the disease;
- Culling positive or inconclusive cows from the herd;
- Feed calves colostrum from negative cows;
- Maintain high levels of hygiene in calving pens and calf shed;
- Avoiding buying in stock from herds that are known to have Johne’s disease;
Testing
Johne’s disease is often not detected on farms until it is too late. Although animals become infected at a young age symptoms are often not expressed until later in life.
By the time it is detected is it possible that the disease has been spread to other animals within the herd.
Regular screening of your herd is the best way to detect the presence of MAP bacteria within your herd.
The three main ways of testing for the disease are through:
- Blood testing;
- Individual milk sampling; or
- Individual faecal sampling.
It is recommend that you wait at least three months after bovine tuberculosis (TB) testing before testing for Johne’s disease.
Johne’s disease has been present in Ireland since at least 1956. Although a closed herd may have been operated for many years, it is possible that the disease might already be on your farm.