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Johne's disease

Johne’s Disease

We are seeing an increasing number of cases of Johne’s disease in cattle. It is caused by the bacteria Mycobacterium paratuberculosis and results in chronic diarrhoea, milk drop and weight loss.

Infection occurs at or around birth but do not usually succumb to clinical disease until at least 2 - 6 years old. This means that there is a long period of time when the animal could be shedding the bacteria for years before becoming ill.

The most common route of infection is through an infected cow’s milk. There is also potential spread from faeces and from wildlife (rabbits and deer). The bacteria have been shown to survive in soil and water for up to a year, making a pasture spread with infected faecesa potential source of infection.

There is no treatment for Johne’s disease. Control depends on preventing calves becoming infected in the first place: 

  • Removing calves from infected cows before they’ve fed and DO NOT FEED POOLED COLOSTRUM
  • Slurry management– clean calving pens, avoiding contamination of water courses, avoid contamination of feed troughs.
  • Breeding– bulls are a potential source of infection so ensure they are bought from a Johne’s negative herd.
  • Identify and cull infected animals– to ensure eradication from an infected herd the cows need to be blood sampled annually. Any positive animals should be culled, along with their offspring.

It is difficult to assess your herd status as bulk milk samples are unreliable as the antibodies become diluted. The best way to identify the potential infection in your herd is to blood sample 30 “at-risk” animals. These include cows over 2 years old that are:

  • Not achieving their potential milk yield
  • Losing weight
  • Scouring
  • Cows prone to other diseases


If you are interested in finding out more, please phone us.