Understanding Johne's Disease in cattle
Johne's disease is a chronic wasting disease of cattle.听It is caused by infection with a bacteria Mycobacterium avium subspecies听paratuberculosis (MAP).听Johne's Disease is听a听welfare and economic concern to farmers as it听doesn't听just cause disease and death in cattle but also results in production losses.听听
The challenge of Johne鈥檚听
A key challenge with Johne鈥檚 is that听clinical signs take a long time to develop and "silently infected" cows can spread the infection before they begin to show obvious signs of clinical disease听(diarrhoea and weight loss)听at two to five years of age or more.听听As听the disease is often not detected until years after the听initial听infection,听some听farmers听call听it听a 鈥榯icking timebomb鈥�.听It is important not to wait for symptoms to appear because,听in the meantime, the herd听is likely to be听less productive.鈥�听
While cattle听remain听susceptible to infection throughout their life, they are at their most vulnerable in the first few months of life.听There is听currently听no cure currently for Johne鈥檚,听but there are steps farmers can take to reduce the risk in their herd.听Early detection and, if resources听allow,听the鈥痵egregation of infected animals as early as possible, whilst taking management steps on the farm to reduce the spread of infection, for example,听not breeding from animals or their offspring which have tested positive听are the keys to control.听
Testing for Johne鈥檚听
The aim of testing is to听identify听infected animals in the herd as soon as possible so that management decisions may be taken to prevent听the听spread of infection from infected cows to the rest of the herd. When infected animals start shedding the MAP bacteria in their faeces, they become 'infectious'. However, this shedding can be intermittent and can听actually occur听before antibodies can be detected by the test adding to the challenge of the disease.听听
The main test used to diagnose Johne's disease is a blood test to look for the antibodies that the animal has produced in response to infection with the bacterium that causes Johne's disease. Blood testing is the most suitable sample format for beef suckler herds. A blood test can detect听Johne鈥檚听infected animals听which look perfectly healthy听earlier than faecal tests are able to. This allows听identification of infected animals as early in the course of infection as possible.听听
Dung sampling helps to听determine听whether听an听animal is shedding bacteria and听is听infectious to others,听helping with听decision听making听听on听whether to听cull positive animals.听It is important to consider that a blood positive animal may have a clear dung test, which听doesn鈥檛听mean the animal is not infected, they may not听be听currently听shedding but听have the potential to shed听in the near future.听
In addition,听the听tuberculin skin test for TB can interfere with the blood test for Johne's disease. Current guidelines听state听that blood testing for Johne's disease should not be performed within a minimum of听three听months after a cow has received a tuberculin skin test.听
Accreditation听and听health听schemes听
听The Johne鈥檚 Disease Risk Level Accreditation programme (the standards set by CHeCS) enables herds to maintain or move towards clear herd tests鈥�(for breeders) and provides assurance that an effective test and control programme is in place (for buyers). Find out more information regarding 厂搁鲍颁鈥�Veterinary Services Premium Cattle Health Scheme (PCHS).
It can听take time,听but by following the听CHeCS听guidance, farmers can lower the level of disease and will reduce the risk of it spreading now and to future generations in their herd.听听
Johne鈥檚 Disease survey听
伊人直播听is听currently听working听on听Johne鈥檚 Disease as part of a larger biosecurity听research听project funded by the Scottish Government.听听
A survey has been designed to build a better understanding of the management practices that help prevent infection, as well as the factors that may make herds more vulnerable to the disease.听
The survey is primarily aimed at beef producers, although dairy farmers are also encouraged to take part. The survey can be completed on a phone,听tablet听or computer, with most responses collected through simple drop-down menus. A paper copy is also available on request.听听
Take part: app.onlinesurveys.jisc.ac.uk/s/sruc/survey-about-johnes-disease-2026听
Kate Lamont, Senior Lecturer,听Kate.Lamont@sruc.ac.uk听听
Posted by SAC Consulting on 21/07/2026
