Friday, February 21, 2014

Farmed deer and Tuberculosis.

We are grateful for any insight into the strange world of zoonotic Tuberculosis control and eradication in this country, and from time to time a new bit of news (to us) pops up.
As cattle farmers we are used to regular TB tests, usually carried out by the farmer's own vet and with the exception of pre Movement tests, paid for by AHVLA / Defra.
But TB control in other farmed mammals is substantially different and with no control on wildlife vectors, is an increasing problem..

 In 2010, we explored TB in pigs - [link] and like pigs, zTuberculosis in farmed deer is usually found at slaughter. But what happens then is substantially different from the regime for cattle.

Testing is not mandatory in the UK for any farmed mammal other than cattle:  thus sheep, pigs, alpacas and farmed deer rely on a post mortem diagnosis. The exception is breeding animals destined for export which need a skin test.

If zTuberculosis is found, then herd restrictions are applied and the intradermal bovine skin test is used as the primary diagnostic test. Whether it is sensitive or specific enough for mammals other than bovines is another story. - [link]

But for farmed deer, there, the similarity to cattle outbreaks takes a significant twist. If zTB is found, a herd of farmed deer faces the same restrictions as a cattle herd and skin tests are demanded by AHVLA. But owners pay. Furthermore only veterinary personnel trained in handling deer can conduct testing, and they are few and far between, belonging to specialist testing 'panel'.

Tests are at 120 day intervals, and two clear herd tests are needed to lift movement restrictions - which in practice is almost impossible as it interferes with the breeding seasons of these animals and apparently may still not pick up the source of the outbreak.

Compensation is 50% of current market value or a maximum figure of £650, whichever is the lower. But this is paid only if the animals are compulsory slaughtered as test failures. No compensation is paid for any animals which owners may choose to slaughter in an effort 'to clean up their own herd' - even if zTB is found at any subsequent post mortem.

Current legislation - [link] is culled from European directives and gives AHVLA power to test for TB in certain circumstances but does not appear to specify by which test. So if a serological test were to be used as a replacement or in addition to the skin test,  would a change in legislation be needed to allow that?

That is a question currently posed by some UK deer farmers to Defra, so that they may trial other diagnostic tests. Some blood assays  used in other EU countries appear to be giving a tad more confidence to the testing regime with farmed deer, and yet Defra appear to be dragging their collective feet over their use, even when owners are paying. 

We seem to have heard this scenario before...

Different tests may also work better with the current 120 interval of skin testing for deer, which we hear can be very difficult to accommodate due to the seasonality of the deer breeding cycle.

Many of these problems with  current TB diagnostics will be discussed on March 12th / 13th in Edinburgh when the Veterinary Deer Society - [link] holds its Spring meeting.

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