Shortly after coming to Gorey, Co Wexford (more years ago than I care to remember), I went out to read a TB test for two brothers. One of the brothers had been painting some gates since the first day of the test – he also had an interest in amateur dramatics. Written over the crush in red paint, it said “TB or not TB, that is the question”.

Recently, we started to do some herd investigations under the Targeted Advisory Service on Animal Health (TASAH) scheme on farms that have had positives with the BVD ear tag test and it reminded me of this quote.

In some cases, there was an ongoing BVD problem and so the source was obvious, but, in other cases, the farm had been clear for two or three years and then a single persistently infected (PI) calf turned up. In these cases, the source might not have been obvious, leading one to wonder if there was BVD at all.

Animal Health Ireland ran training courses for vets so that they could do these investigations and I was a bit sceptical as to whether the investigations were worthwhile. However, the feedback I am getting from my clients having done some of the investigations is positive.

BVD is not an easy disease to understand. For a PI calf to be born, the mother has to be infected between day 30 and day 120 of her pregnancy, so the infection has to occur at least five months before the calf is born.

The investigation involves looking at where that dam (or all the dams if there is more than one PI) was when she was at this stage of pregnancy.

For spring-born calves, the danger period was usually the previous summer grazing season. If the cow had been bought-in, she might not even have been on the farm at that point.

There is also a review of biosecurity as part of the investigation and this proved interesting for the farmers.

Points that came up included any quarantine for bought-in animals, the farmers’ disinfection routine after being to the mart or other farms and the disinfection routines of others entering the farm, including farm workers, hoof trimmers, AI technicians and vets. The collection points for the knackery lorry also frequently arose, as it is not ideal that a lorry full of dead animals (with the possibility of carrying some PIs) would drive into the middle of the yard beside the animal housing.

Shane McGuckin is a partner in The Vet Hospital, a five-person mixed practice in Gorey, part of XLVets, a group of progressive practices working to achieve a better future for agriculture and veterinary in Ireland. For further information, go to www.xlvets.ie.