Bovine tuberculosis is wreaking havoc on the UK’s farming industry and the badger has been targeted as a culprit. But is it really to blame?
Peter King, Executive Committee Chair at the European Livestock Association, NFU Director, Anthony Gibson, and Animal Health and Welfare Minister Ben Bradshaw, are among those Neil Davey speaks with to find out.
Evidence suggests that trace element deficiencies induce a susceptibility to M.bovis, which can be corrected by restoring the nutrients to depleted soils, particularly in the hot spot areas that occur on soil types intrinsically deficient. Furthermore, inadequate trace element intakes are a risk factor for false negatives—cattle that do not respond to the TB skin test because their circulating lymphocytes are suppressed, a condition known as anergy. These are silent carriers, healthy in themselves, but whose undetectable infectivity could explain the persistence of the hot spots. Suppressive factors include zinc, selenium and cobalt deficiency. Adequate trace element intakes would lift the suppression and allow the silent carrier to be identified by the skin test.
Control of bovine tuberculosis (bTB) using vaccination could be one step closer in the UK, with the development of a test able to distinguish between vaccinated and infected animals.
TB is on the increase in the UK cattle herd, costing more than £90m a year and vaccination is under ‘active consideration’, say the Institute of Animal Health. This would involve using the same vaccination used to immunise humans against the disease, BCG.
A vaccine to protect cattle against highly infectious bovine tuberculosis is to be tested in national herds within three to five years, following successful trials in laboratory animals.Government vets plan to use a modified form of the human BCG vaccine to protect cattle from the disease, which was responsible for at least 20,000 animals being sent for slaughter last year.
The disease was almost eradicated from the national herd in the 1980s but there has been a dramatic resurgence since, with cases rising 14% year on year. The disease cost the taxpayer £80m last year in compensation paid to farmers.
Bovine Tuberculosis (bTB) was a major problem in cattle herds earlier this century but was virtually eradicated by tuberculin testing and slaughter of infected cattle. However, bTB has persisted in southwest England, its traditional stronghold, some parts of Wales and the West Midlands, and is now increasing in other parts of Britain. Since the mid-1970s tens of thousands of badgers have been culled in response to bTB outbreaks because of circumstantial evidence that badgers spread the disease.
* Badgers are the most significant wildlife reservoir of bovine TB in the UK,
followed by Red Deer in some areas such as Exmoor, and when the Wild Boar population increases they may also be a reservoir in the Forest of Dean for instance.
I have been surprised to learn that veterinary public health microbiology is not conducted in the same way as in human medicine and there are no trained clinical specialists nor is there peer reviewed best practice. The only veterinary laboratory in the UK doing work on TB funded by government grants is Weybridge, and in order to get funding for their work the scientists, few of whom are vets, must formulate
hypotheses to competitively bid for research funding or carry out government, DEFRA, commissioned work to devise a new test such as to detect the gamma interferon response specific for M bovis infection using peptides derived from proteins absent in the BCG vaccine (Bacille Calmette Guerin) but expressed by M bovis.