Saturday, March 11, 2006

Clarification & 'Basic points'.

We have received a very useful comment from 'A. Ross' on the site which we post in full below.

"I sympathise with all of the farmers who have lost well-loved animals to bTB, or the ineffective test we are lumbered with.
While I agree that there is likely to be some infection from badgers to cattle, and that this should be prevented, I think there are some basic points which need to be addressed.The results of the study by the ISG clearly show that unless badgers are exterminated across very large areas of the country, the 'edge effect' will likely cause an increase in bTB. Obviously nobody wants that. To avoid it, ALL badgers in a very large area would need to be killed. This is simply not possible. Therefore, a wholesale badger cull is unworkable as a cure for the problem. What is needed is a decent test for bTB in both badgers and cattle, which does not give the high rate of error of the current test. Once bTB is detected or suspected in an area, all cattle and all badgers would be tested, and only those with the disease would be killed, leaving the healthy animals alive. This would not only minimise the number of cattle which would need to be killed, but would also reduce the 'perturbation' of the badgers' territories. As most of us farmers/landowners are unwilling/unable to catch and kill badgers, this should be done by Defra, and supervised by badger experts. Using this system, in conjunction with a vastly improved movement testing regime (using the new improved test), should quickly reduce the incidence of bTB over large areas, and avoid many of the problems associated with a wholesale cull of wildlife.Initially, the movement testing regime should be stepped up, at Defra's expense, to prevent any movement of infected cattle to new areas. After all, this is how bTB spread to many areas after Foot & Mouth. "

Having experienced the intradermal test for the last - too many - years, we have no problems with it. Neither in fact does the rest of the world who use it as a primary diagnostic tool. That it shows what are referred to as 'false positives' is a measure of its success, in that it measures the immune response in skin of an animal which has had contact withor exposure to m.bovis, and in at least two thirds of the cattle slaughtered, before lesions have been developed or any infectivety established.

You say "there is likely to be some infection from badgers to cattle, and that this should be prevented". On this site we have told how Defra's bio security advice is as much use a wet paper bag in the face of a determined badger. That they can climb up to 16 feet, excavate to 15 feet, slide under sheeted gates only 4 inches off the ground and easily access feed troughs 4 feet off the ground, which Defra admit is "too high for cattle to use" is all known. That their latrines are fencable, but 30 percent of urinations occur at pasture is also logged. And that in that highly infectious dribble, a badger with kidney lesions can void up to 30ml at a time of a liquid containing 300,000 ml of colony forming units of bTb in each single 1 ml.,and just 70 cfu's are needed to infect a cow. Under those circumstances, bio security is impossible. Cheeseman was asked in Shropshire many years ago how to keep infected badgers and cattle apart, and his reply to his horrified audience was " You can't. You get rid of your cattle".

So we are full circle back to dear old John Bourne and the ISG. The 'edge' effect and the need to 'exteriminate, exterminate, exterminate', all the goddam badgers from Cornwall to Hadrians Wall. Absolutely wrong. Emotive claptrap. But it's done its job and widened the opinion gap between people who genuinely want the problem solved for the benefit of all. That way pseudo science can comfortably benefit from more cash in an attempt to fill it. Cynical aren't we? You bet.

We opposed Krebs from day one on the very points that we refer to above. That a raft of epidemiological information was already known and that 'postulating' such information under the gold standard for such excercises (Evans Postulates) made Krebs totally unecessary. A worthless excercise. That 'perturbation' would make things a whole lot worse, and that the way Bourne was going to implement Krebs' proposals would lead to chaos. Why the surprise? But even worse, why believe it?

We quote below from this weeks' Vet. Record where we believe the points you make re. the ISG work are covered admirably.

"The huge scale of the exercise, requirement to train large numbers of trapping staff, interference by animal rights activists, intimidation of landowners and lack of co operation of many of them, all presented problems. (and hotspots left within the Krebs circles of farms under restriction at the time the trial started, and who did not 'qualify')
Now the trial has ended, the interim results (1st and second years only) show that while the ISG claim that 'on farms where trapping was allowed' , the efficiency was 60 - 80 per cent, the overall efficiency of trapping throughout the trial areas was remarkably poor at between 20 -60 percent. (As we have quoted PQ's many times that in 2003, the tally of trashed traps and traps stolen intact, was 69 percent of the ISG target)

In the trials, the trapping of only 20 percent of the badgers implies disturbance and likely disposal of many of the remaining 80 percent of the population of infected badgers. Even a trapping rate of 60 percent would be disastrous, but removal of such a small number of infected animals as 20 per cent is obviously likely to have caused enormous disruption.

However the trials do provide a valuable cautionary tale. They have shown that if the task of culling is done ineffectively for long enough and over a large area, it can produce catastrophic problems. The approach used would have spread Tb amongst the badgers, This would occur not only by causing diseased animals to move outside their territories, but by stressing those latently infected cases to develop, fulminating infection leading to disease. "

This erudite over view of Krebs shows just why the ISG are saying that huge areas need to be culled to have any effect, and to minimise the 'edge' effect. The report concludes:

Having first hand experience of Tb in badgers and cattle and attempts at its control, we strongly caution against any more 'quasi -control ' methods. We fully endorse the ISG's stated opinion that piecemeal snaring or trapping will make matters considerably worse. Despite the misery and disruption farmers have had to endure, and the carnage of their stock, it is unrealistic to expect farmers to carry out an effective cull and nor should they be pushed into doing so. The eradication of Tb, a notifiable disease, is entirely the responsibility of the Government. That also includes controlling its reservoir host the badger. Also, it should not be forgotten that Tb maims and kills badgers and is a welfare problem for them as well.
We disagree with the ISG's assertion that culling would need to be carried out over huge areas to avoid the 'edge effect'. and consider this effect to be the consequence of the very poor trpping efficiency causing the dispersal of infected badgers. This assertion is thus unessessarily alarmist".

That bTb moved to Cumbria and the north in cattle after FMD is well logged. That when the testing regime eventually caught up with these very few cattle, and they were destroyed leaving no residual infection within the herd is not so widely explained. A post movement test of breeding cattle would have found them, and hopefully may still do so. That they failed to transmit within the host herd is noteworthy I think and mirrors Irish cattle- cattle trials.

The vets from whom we quote, are in agreement that carbon monoxide gassing of setts in daylight would prevent any such peturbation, would be efficacious and humane. We favour leaving strong main setts preferably identified by RT-PCR technology as 'biological buffers' to prevent any territorial fighting of 'disperers'. We would keep monitoring 'off sets' that had been gassed, to mop up the badgers that their own social group had excluded.

A mass cull of badgers is emotive rubbish. It is not necessary, counterproductive, unachievable but designed to keep the people who propose it and oppose it, in the manner to which they've become accustomed. The beneficial crisis goes on, and as ever the losers are the badgers and the cattle.

1 comment:

Anonymous said...

To A. Ross.
It is my understanding that in only 31 herds of restocked cattle in the North East, was a 'foreign' cow responsible for the breakdown. When she was identified by the skin test and removed, the rest of the herd (in 26 of these cases), were clear. In 5 herds cattle to cattle transmission did occur, but Defra's proposal to test 'new and re-formed' herds promptly will stop that. Some of these restocks went 3 or 4 years without a test.

I agree with you that Defra should take control, oversee and use their trained expertise to supervise this. But if the posting below is correct, then Defra have no intention of employing the necessary personel.

I agree entirely to clear an area of infection - wherever it may be found. Testing and culling cattle is absolutely a waste of time if constant reinfection is happening, as the editors of this site, and some commentators have explained.

I think that in-field diagnostic tools such as PCR should be used. They are capable of locating infection in about 20 minutes, without the need to submit samples to a laboratory. The latest models are already in use in hospitals to screen patients, and I do not see any reason why they should not be used to screen badger sets to identify the infected ones, which then should be gassed with carbon monoxide, leaving uninfected ones completely alone.

Vaccination is a pipe dream, and ignores the fact that this disease affects far more species than badgers and cattle. We have to control bTb in the environment or it will get even more widespread. To test 'all badgers' in an area where cattle are flagging up infection is unrealistic, if you mean caturing individuals and subjecting them to blood tests. But PCR would identify any infection they or any other carrier species, were leaving behind.