Diseases can blow into herds
He said potential for field-to-field disease spread is greater in Ireland than in other EU countries, where cattle are in isolated blocks, and often housed rather than grazed. For example, BVD can blow into the farm — or can be in the foetus of a healthy purchased in-calf animal. If buying in, test, and quarantine until you get test results, he advised. Dr Chavasse said animals which are persistently infected (PI) with BVD drag down the entire herd’s immunity. Hence the need for bulk milk screening and blood testing to identify and cull PIs, which can look healthy and be long lived. Weanlings should be checked from seven months. Vaccination reduces spread.
Human infection is one of the dangers posed by leptospirosis; animals can be vaccinated from four weeks.
Dr Chavasse linked IBR disease in Irish herds to unwise buying of genetics in the 1970s and 1980s. He said Johnes disease takes four or five years to develop, and it’s too late when scour and wasting symptoms appear. Individual milk or blood samples are needed for detection. An estimated 10% to 20% of herds have Johnes.
There is no vaccine or treatment, five to ten years of testing and veterinary work are needed.
Healthy carriers are a feature also of salmonella. All abortions should be investigated. Dr Chavasse said the abortion diagnosis rate has improved to 60% of samples.
