‘Myth busting’ on bovine tuberculosis - Veterinary Practice
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InFocus

‘Myth busting’ on bovine tuberculosis

RICHARD GARD hears about the latest developments in the battle against bTB

THIS autumn may prove rather challenging for the many veterinary surgeons visiting farms to test cattle for bTB and for the many veterinary surgeons who then explain the findings to clients.

After years and years of dealing with the effects of bTB at farm level following testing, and the subsequent consequences to the management of an infected herd, the indications are that veterinary surgeons are expected to be advising actions to control the disease.

It has always been a difficulty that, unlike other infectious diseases, infection with M. bovis has had a different point of contact for the farmer than his own vet.

If the farmer is concerned about infection with BVD or Johne’s, then talk to the practice, but for TB talk to, well, just who exactly? In the south-west, the NFU is planning to engage specialist advisers to visit farmers and discuss this disease. Other activities are also being developed.

In early October and November in Somerset, Cornwall, Gloucestershire, Staffordshire and Cumbria, veterinary surgeons are expected to undertake “myth busting” and “leave the meeting with a clearer understanding with which to address advice surrounding herd breakdowns, biosecurity issues for ‘clean’ and restricted herds and upon which to offer informed opinion to anyone who may wish to know more about this intractable disease”.

With over 5,000 cattle farmers in 2009 farming under TB restrictions, there are many people looking for help, guidance and solutions.

The TB Roadshows are being arranged by the BCVA and are open to all veterinary surgeons, not only BCVA members. Whatever the size of premises booked for each location, there is likely to be a squash. Delegates are invited to consider the myths that prompt questions that clients will want answered about bTB.

Four examples are offered concerning false positives, vaccination of badgers and cows, the assurance from premovement testing and the slaughter of TB immune cows.

There will be many other points that require clarification and Andy Biggs will be considering diagnostics, Glyn Hewinson the science of vaccination and Carl Padgett aspects of practical politics. This all leads into a structured, open discussion, so arrive prepared to engage in a topic that you think you know well and leave with additional information and a positive outlook to client discussions.

Members of veterinary practices in six catchment areas have already had an evening of TB information concerning The Badger Vaccine Deployment Project. Badgers are to be trapped and injected with a BCG vaccine that is said to be 10 times the strength of the human product.

One of the practices in the heart of two selected areas is the Vale Veterinary Group at Tiverton and Cullompton in Devon. Andy Biggs is a partner based at the Tiverton end and although he wears many TB hats nowadays, it was as the local vet on the ground that we discussed his expectations from the use of a badger vaccine.

Various comments have been highlighted in the regional and national farming press about the expenditure of, reportedly, £5 to £10 million on the deployment project but, from the veterinary aspect, the inadvisability of applying a vaccine in an infected population is of more technical concern.

Andy understands that inquisitive young badgers will be targeted with the trapping and vaccination and that gradually a population will build that does not carry M. bovis and does not pass the infection to the cattle.

As for increasing the number of super excretors, by injecting infected badgers with the vaccine, there is no evidence from the development work to support this. Similarly, there is no evidence that trapping badgers in a cage either stresses the animals, to the extent that it makes them more susceptible to infection, or causing the trapped badger to be excluded from re-entering the sett by other badgers.

We were not able to arrive at a definitive performance figure for the vaccine in uninfected animals. A reported 40% effectiveness finding was considered to be inaccurate and figures of up to 70% have been mentioned. In infected badgers the vaccine is not expected to be beneficial.

Included in the presentation to the practices is the option for clients to purchase the badger vaccine. The vaccine is to be licensed in 2010 and efficacy data will then be made available. If a farmer wishes to have badgers vaccinated this will have to be carried out by licensed contractors.

Andy points out that the development of a badger vaccine is the outcome from long-term decisions and not a response to current conditions with bovine TB. Hopefully, further work with baits will offer a cost-effective way to control infection.

An important issue is whether farmer clients will welcome involvement with the project. Participation is on a voluntary basis. Meetings with farmers are planned for September. The training of contractors will start next year with a gradual build-up in each area followed by five years of trapping. It is too early to get too excited and there has been little reaction from the farmers to date.

There are a couple of points that were made in the presentation to vets that will need further clarification in due course. In the local area it is recognised that many cattle herds utilise land spread over a couple of parishes that are not geographically linked. The cattle occupy this land at various times related to stocking numbers, weather and cropping. Badgers occupy this land and specific badger communities forage across various land ownerships.

The presentation indicates that it “doesn’t matter if farms aren’t joined up, most of the benefit is on the farm where the vaccinating is done”. It appears that local conditions may mean that infected badgers will continue to visit vaccination project farms and that there would be important benefits if neighbouring farms were encouraged to participate, assuming that the performance of the vaccine is under scrutiny rather than just checking deployment practicalities.

The whole subject of whether badgers die from TB is addressed in the presentation. It is assumed that few badgers living with TB-positive cattle herds die from TB. If this is correct, then vaccinating the badgers will not increase their life span. But if badgers do die from starvation or other causes because of the disease, the potential for an increase in the already high badger population in TB hotspots may be a real concern.

High badger populations may be a limited problem until food shortages or flooding causes movement and then ingress from animals of unknown health status. Monitoring the local wildlife could become a very important component for cattle disease control.

Any value from vaccination is years away. For the farmers and vets in the TB hotspot areas there are issues to be addressed now. Andrew Cobner of the Penbode Group, with clients in Devon and Cornwall, has the advantage of utilising TB Master to record the details of TB.

Andrew is very concerned about the rise in the numbers of cattle being slaughtered within the practice. Farmers with herds that have suffered TB for long periods are learning to cope with the restrictions but with 14 new herds a day becoming restricted in Devon and Cornwall, there is a great deal of angst.

This autumn, a film identifying the way forward for veterinary practices working with wildlife assessors and groups of farmers is to become available. This is a new approach, unsupported by any of the established studies but offering an increased level of understanding and participation, which works alongside all other activities.

Perhaps it would also be worthwhile to consider who gains and who loses with bovine TB? Does TB testing enhance or restrict the performance of a cattle veterinary practice? It may be that to reduce TB in cattle may require bigger and better and more frequent testing and the volume of testing and frequency of farm visits needs to increase. But farmers generally dislike the testing process because of the time and disruption.

Restricting the cattle-badger interaction may become a veterinary skill. How about TB herd health visits funded as part of the eradication programme – or is that option just another myth?

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