Johne’s disease (JD) is a bacterial disease of cattle for which there is no cure and is caused by the bacterium Mycobacterium avium subspecies paratuberculosis (MAP).
In 2016, it was estimated that JD had a presence in 28% of Irish dairy herds as a result of herd expansion post removal of milk quotas and it is reported that the most recent trends in JD are likely to be upwards.
If good management control is not implemented on farms, the diseases widespread prevalence will be inevitable.
Once present in a herd, JD spreads slowly and silently, making it difficult to combat, with the signs of JD being difficult to identify at first, according to Animal Health Ireland (AHI).
Effective biosecurity measures must be put in place, and when you are unsure, take advice from from your vet who will have the knowledge required to minimise its spread.
Risks of Johne’s disease
Animals who appear healthy and even have negative blood test results for JD, have the potential to release a large amount of MAP bacteria in their faeces, which will begin the spread.
Bringing in outside colostrum onto your farm is a huge risk, as if turns out to be contaminated, disease will spread rapidly in calves.
Slurry/manure that is imported onto the farm on which MAP bacteria are present will contaminate the paddocks, and young stock will be especially vulnerable to this infection route.
Animals that have left the home block and are grazing contaminated pastures outside the farm, or out at marts or shows can spread the bacteria upon arrival at the home home farm.
Visitors and workers on the farm can bring contaminated dung on vehicles, equipment or boots as they move between herds.
Reducing the risk
Reduce the number of bought in animals onto your farm, or ideally source the animals from low-risk herds that have shown negative blood test results for several years.
Avoid the introduction of colostrum from an outside source onto your farm unless from a high assurance source.
If it is possible to avoid importing slurry/manure from an outside source, then it should be done while making sure that contractors that come into the farm have clean equipment.
Where there is stock grazing outside of the farm, avoid grazing pastures that have been recently spread with slurry and make sure the likes of your contact-rearing units have good biosecurity measures in place.
The calf area should be treated with diligence and care, making sure anyone on the farm is clean and disinfected before entry, making sure there is accessible cleaning and disinfection points.
Minimise the number of visitors on to your farm and ensure that every visitor has clean equipment and machines before entering your yard.