What do you need to know about Johne’s Disease in cattle?
Signs do not typically develop until between three and five years of age. However, cases have been reported from 10 months of age and in older cattle.
Animals lose weight and develop persistent diarrhoea, sometimes bubbly, and many animals are culled before they develop full-blown clinical signs due to poor production. The disease is usually confirmed by a blood test as other diseases have similar signs. The number of cases diagnosed has increased over recent years.
Annual number of cases of Johne’s disease in cattle diagnosed by Veterinary Laboratories Agency (VLA) in Wales.
In all herds, the most recent calf from affected cows has a high chance of developing Johne’s disease and should not therefore be retained for breeding. Once Johne’s disease has been diagnosed in dairy herds, control is largely based on preventing exposure of calves by keeping them away from the faeces of older cattle.
Pooling of milk or colostrum to be fed to calves should not be carried out on farms that have seen cases of Johne’s disease, unless the milk is pasteurised before feeding.
Another key part of control programmes in beef or dairy herds is testing adult cattle for antibodies regularly to identify infected animals and either remove them and their recent offspring from the herd or separate them into a separate ‘infected’ group.
Some control schemes use blood samples and others use milk samples, but as cows often develop antibodies only a few months before developing signs of the disease, this has to be carried out at frequent intervals to achieve a benefit. Your veterinary surgeon will be able to advise on these schemes but all require a long term commitment if they are to be useful.
If a farmer believes his herd to be free of disease, it is advisable to try to prevent introduction of Map infection, but this is difficult if cattle are bought-in frequently.
Pre-purchase blood testing is a sensible measure but will only usually detect those infected cattle that are going to develop the disease in the next few months and is not recommended for animals under two years of age.
It may be possible to obtain some assurance from vendors regarding the status of their herd but some owners will not be aware that infection is present in their herds. Buying from herd acrredited free sources provide the best assurance but only a small proportion of herds are accredited free.
There is plenty of information available online including on the Johne's information center website, and specific advice on Johne's disease for dairy herds on the Welsh Government website.