A SURVEY in 2006 illustrated the value of veterinary surgeons being well-informed about cattle disease and Professor Joe Brownlie laid out a programme, for veterinary practices and their clients, for the realistic control of bovine virus diarrhoea.
Three years later, the experiences of operating disease control by practices have been collated by the RVC and this knowledge, together with management tools, was presented and discussed last month at a workshop at the Bristol veterinary school.
From the farmer’s perspective, culling persistently infected animals and vaccinating has shown an improvement in calf health. Professor Brownlie points out that the BVD virus is immunosuppressive and a reduction in the severity and frequency of respiratory and enteric disease is an expected outcome from a control programme. It is encouraging, however, that participating farmers have recognised that calves are healthier and that more calves are being born and raised.
There is no national movement to control BVD and so it is up to practices and their clients to take the necessary steps to eliminate the disease, which is a real possibility. One of the important realities is to know what is going on “over the neighbour’s gate”.
Involving clients
At present, practices are involving interested farmer clients with a testing programme and then putting controls in place. These initiatives have been applauded from the north of Scotland, Rutland, Norfolk and Suffolk and Somerset, as county schemes, where more than one practice is participating in the BVD programme. But the next challenge is to involve neighbouring farms so that a local area tackles the disease.
So, the search is on for persistentlyinfected animals and then vaccinate to reduce the biosecurity risk. The vaccine standard is that no virus particles cross the placenta. Embryonic mortality occurs when the foetus is infected in early pregnancy from day 1 to 24.
There are other practical points that were raised in discussion regarding the ability for a persistently acutely-infected bull to shed BVDv in semen and that the foetal fluids of a cow with a PI foetus are “a pure culture of BVDv”. This in turn raised a point about calving ropes and their ability to spread the virus between cows.
John Fishwick chaired the sessions, introduced the speakers and encouraged the discussions.
Richard Booth is engaged in support for the practice programmes as a PhD student at the RVC. One of his tasks is to identify the costs and benefits of BVD control, so that the various actions can be discussed between the vet and the farmer with real figures to support management decisions.
Samples are being taken from the cattle on participating farms and virus identification and sequences have been recorded for 120 PIs. Novel developments are taking place to overcome the problem of contaminated samples. The ear notch sampler, which takes tissue leaving an identification tag in place, was discussed.
Of particular interest is not only the success of the farmers who adopt the programme but the reasons why, despite full technical support, some farmers register an initial interest but do not actively take advantage of the opportunity to control the disease.
A major reason is given as the cost of testing, identified at £430 for 100 animals. Dr Nick Bell (University of Bristol) has been developing a solution to the cost issue.
Dick Sibley pointed out that there are over 16,000 cattle holdings in the south-west of England and 1.7 million cattle. The South West Healthy Livestock Initiative is under development and a concept note has been submitted for funding to provide information on the health status of livestock.
If the programme goes forward it is anticipated that a good proportion of the testing costs will be met. Dr Bell was enthusiastic about this opportunity and veterinary surgeons wishing to develop BVD control programmes with lower costs may wish to contact him.
Mick Cranwell (Starcross) ran a workshop on the testing and surveillance strategies for BVD. The two approaches with the test are to detect disease-free animals and disease-positive animals. Vaccinal antibodies are detected for a short time with a low peak, whereas maternally derived antibody lasts six to eight months.
With bulk tank milk samples, a straightforward practical point is to know which animals contribute to the sample. It is not always easy to identify which animals have been vaccinated but attention to these details will allow more accurate assessment of BVD in a herd when the lab results are interrogated.
It was highlighted that the surveillance questions are: was the virus there, is it there and is it still there? Answers are achieved by determining the BVD health status, identification and removal of PIs, vaccinating and then monitoring to confirm BVDv status.
Practice experience
Peter Plate (Damory Group, Dorset) outlined the practice experience. Members of the practice agreed that BVD control was an achievable target, with the vets pulling in one direction and the experienced vets and new graduates working together.
Blood samples from youngstock are taken at the time of TB tests. Use of the Erns ELISA from three weeks of age means that the farmer does not have the cost of rearing PIs to nine months and there is less risk of virus transfer to other animals. A negative test indicates that the dam is also negative.
There are demands from farmers for rapid results and it is necessary to be confident about the technical aspects and the likely outcomes of testing. Time and money can be wasted, with unrealistic expectations leading to frustration and disappointment.
For a veterinary practice it is important to be able to access all the relevant records in order to progress each control programme. Dick Sibley and Peter Orpin gave a demonstration of the myhealthyherd health evaluator. Faced with an individual computer screen, linked to the central server, each participant entered data, looked up supporting information and thought their way through a herd programme.
For those familiar with the traffic light system, and the fact that a herd can be free of disease but does not have a green status because it is susceptible to disease, the in-depth nature of this tool is recognised. For newcomers to myhealthyherd, there is a period of familiarity needed until that eureka moment arrives and it all becomes clear.
Some folk were dashing about the screens and finding due vaccination dates, test results, dates for next tests and the details and interpretation of results, while one or two were struggling with the mouse placement and finding screens of interest that were not immediately relevant.
As the interchanges and discussions continued, it became clear that one vet with one farmer client can probably manage a BVD control programme with individual application.
When there are several vets and many clients involved, the need for a common system becomes essential. Add the point made by Professor Brownlie about the need for technical competence, the value of an instant onscreen referral, offered by an online database, is apparent.
A recent development is the myhealthyherd trading visa. With herd details entered, a full testing and results history for the herd can be offered with a beast for sale. The purchase of BVDv along with the animal is a real problem for farmers and vets, particularly in the south-west with the need to replace herd members slaughtered within the TB test and cull programme.
Technical details, video discussions and issues about BVD are available at the successful RVC website, www.rvc.ac.uk/BVD/Index.cfm, together with the opportunity to share experiences and raise issues. For further details about the online support tool, trading visa and training options contact: enquiries@myhealthyherd.com.
