At a recent Beef Expo event, Farmers Weekly reported the NBA position - [link] on a couple of these new regulations. Abolition of AFUs (Approved Finishing Units) and the mandatory use of Gamma interferon blood testing, if a herd in a cull area has a breakdown after year two.
AFUs are not really our field, but we have done a bit of digging into the notorious GammaIFN and can find nothing reported in this country after 2005, when scientific papers were full of hope, rather than reports of its limitations and the despair felt by victims of its widespread roll out.
The late John Daykin and Dr. Lewis Thomas had this to say - [link] in 2007, and we pulled apart the 'early detection' line - [link] in a further posting. But despite the warnings of low specificity, many false positives and a pile of dead cattle, Defra went ahead. And this sort of carnage - [link] was the result on many farms.
News from Germany confirms it it not in use in that country due to low specificity. Our correspondent tells the following story:
"The test was used in Bavaria when 40+herds went down with M. caprae. Farmers were up in arms because truckloads of cattle were killed as positives based on the results of the IFN test. Where both tests ( SICCT+IFN) were used only 56.1 % of animals gave the same results in both tests and the majority of cattle slaughtered after IFN didn't show lesions and were culture negative.
Of course this doesn't mean they were not infected but it didn't help to boost acceptance. The reliability of the [blood] test seems to be very much affected by the amount of bacteria circulating.
Another blood test, AB-ELISA, failed completely.
The reason for the problems with IFN in Germany were that there is no way to standardise samples. Even the location where the blood is taken ( tail, neck etc) makes a difference as does temperature, time between sampling and arrival in the lab, storage, time of transport...
In Germany, there is the opinion that the test is not fit for use under field conditions and if used, a positive result must be confirmed by other diagnostics tests. That leaves only SICCT or pm....
Also of interest, is that if skin testing isn't done properly (i.e. subcutaneous inj. instead of intracutaneous) there will be false positive IFN results later, even after a long time. The German reference lab clearly states that the skin test and the IFN have to be done absolutely 'lege artis', (that it is performed in a correct way. ) otherwise the results are not reliable."Nevertheless, and despite the carnage caused by its widespread use a decade ago and the problems of standardisation of its use in the field, Gamma IFn is set to be introduced under the following circumstances:
Criterion 1: The APHA veterinary investigation concludes that the most likely bTB transmission route for the affected herd was contact with infected cattle and measures are in place to prevent further spread of disease from this source;
Criterion 2: The infected herd is located in one of the areas where at least two years of effective licensed badger population control have been completed.
Criterion 3: There is clear evidence that repeated skin testing of the herd has failed to resolve a bTB incident.Now, farmers who have signed up to these scattered, small areas of badger culling, already have a number of Defra / NE hoops to jump through. One could say too many. And we hear that if they do not carry out Defra's duty of eradicating TB infected badgers properly and in a timely manner, then Defra may do the job for them - and charge for the privilege.
So for Defra to bolt on other criteria for cull areas, already signed up and presumably agreed with the organisers, we think is a pretty low blow. Especially a bolt on as brutal as gamma IFN.
In fact we would go so far as to say, it should be subject to legal challenge. But with the NFU and cull organisers comfortable with the concept, while not understanding the reality of this test, that is unlikely to happen.
But what will happen is this: