Friday, May 06, 2011

Not guilty.

We have received sight of a press release from the Badger Trust in which our posting about the TB outbreak in Cumbria is quoted.

We're very grateful to Jack Reedy of the Badger Trust, for the heads up. Perhaps if people read the posting, they will see that we are treading water very carefully with this one, as we just do not know the source as yet.

However Mr. Reedy has voiced his own opinions on cattle farmers, and our animals, quite forcefully.

The press release is less than clear on a number of points, and we will summarise;

Badger numbers are tricky, but if populations are controlled then you do not see RTA badgers or badgers dead in fields. In fact you rarely see a badger at all. And that is how it should be. We stand by our statement that farmers in Cumbria have reported to us increasing numbers of road kill badgers and badgers dead in fields.
That was a precursor to our own TB outbreaks.

The Mammal Society (which the trust quote) did a survey on badger numbers and found that the population density had increased by 77% in a decade. That was what was reported in 1997. (14 years ago.)
(Ref: "Changes in the British badger population, 1988 to 1997" (1997). G. Wilson, S. Harris and G. McLaren. People's Trust for Endangered Species (ISBN 1 85580 018 7))
Nothing has changed since, except more growth.

Ernest Neal who helped frame the Protection of Badgers Act 1972, described 'good badger country ' and an 'excellent population' as about 1 adult per sq. km.
Roll forward 40 years of good intentions and our PQs noted that the highest recorded density in England (in 2003) was Witham Woods on Oxon, at 38 per sq km.
The vaccination trial last autumn cage trapped 16 adults per in Glos.
PQs also note that as populations become larger, individual animals within them tend to get smaller as pressure on food supplies and space become higher.

We have been very careful not to hammer on the wildlife side for this outbreak, because we just don't know. But as we said, TB doesn't fly in with the tooth fairy. For the amount of cattle involved here, exposure has been high or continuous or both. This could be an open lung case cow (or udder lesion case with pooled milk) or a wildlife / other mammal continuing interface. And that could be a badger, alpaca or any other mammal with open lesions containing and shedding m.bovis.

But until that source is found and removed, tested cattle will continue to react and continue to get slaughtered.

AHVLA spoligotyping will nail the strain. Further investigation may nail the source.
Cumbria has its own unique strains, when further levels of DNA are examined down to VNTR. (Variable Number Tandem Repeats) And the county is certainly not TB free, as the Dunnett report quoted in our update, commented. But levels are low as shown by the tested, sentinel cattle.

From PQs:
Spoligotyping is used to determine molecular type for all isolates of the bovine tuberculosis bacillus (M. bovis) obtained from badgers and cattle. Variable Number Tandem Repeats (or VNTR), a technique able to subdivide some spoligotypes, is also used. Generally the different strain types of M. bovis that these techniques identify exhibit distinct and probably longstanding geographical clustering. Within each geographical cluster the same strains tend to be found in badgers and cattle .
It was found in 2002/03 that some FMD restock reactors did not carry the strain of the consigning farm, but had picked up the Cumbrian variety. (AHVLA info)

M. bovis isolates are routinely typed using a DNA fingerprinting technique called spoligotyping. In Great Britain 30 different spoligotypes have been identified in cattle and in 16 badgers. Of those in cattle, 12 of those account for 99 per cent. of the isolates.

Badgers can wander several miles, especially if they are 'dispersers' chucked out of a group - but many more if they are 'sanctuary' releases or caged transfers moved by car. Mandatory records are not required to be kept by such sanctuaries or rescuers of the location of released badgers. Just the permission or passive acquiescence of the landowner.

Alpacas may also figure, as they are capable of onwards transmission both within a herd, and to wildlife, and thus should be considered a possible source.

Finally, the number of cattle slaughtered as TB reactors, the Trust say is down.
But as shown in Defra's January figures for GB, reactor slaughterings are up by 34 percent on 2010.
AH tell us that this trend is continuing and they are having difficulty coping.

We think the man Trust doth protest too much.