Sunday, October 28, 2012

BCG - Reality (meles meles)

We've tickled this subject lightly over the past years, but as it seems to be flavour of the month with the BBC,  the media, an aged rock guitarist and assorted groupies, perhaps we better have another look.  There are several documents and links to the reality of BCG use both in badgers or cattle - or any mammal likely to come into contact with M. bovis so we'll summarise a few.

BCG vaccine for badgers has only applied for, and received what is known as 'Limited Marketing Authority' (LMA) licensing, which means its efficacy was neither shown nor needed to be shown, thus the oft' spoken claim of 74 per cent efficacy should remain moonshine.

 That 'trial' pre-secreened its badgers, catching 844, but only using 262 - an infection rate of around 43 percent we were told. They also anaesthetised those which were vaccinated. All vaccines come with instructions on administration which may include intradermal, subcutaneous, intra-muscular or oral routes. How they are given is very important, so the library pictures of a gowned and masked figure approaching a caged badger with a long hypodermic are quite farcical. But we digress.

On badger vaccination, from Dr. Ueli Zellweger, a Swiss veterinary practitioner with several years of experience dealing with  bTB,  a short paper entitled " Bovine Tuberculosis, Animal Welfare and the BCG Vaccine."
The darkness and sticky air conditions in a badger set is the ideal climate for tuberculosis bacteria to survive for months. Any cub born in a set with TB is likely to get infected in the first few weeks of his shortened and possibly very miserable life. It might be even infected by its own mother. Some will die soon and some will be carrying this Tb infection in latent form until they die. If such an already infected badger is vaccinated with BCG there is the risk that the latent infection opens up with the consequence that this badger is spreading billions of TB bacteria. Where is the animal welfare aspect?
Unlike most other common vaccines the BCG vaccine does not stimulate the huge production of specific antibodies. Therefore the BCG vaccine does not prevent an infection; the only thing it does is reducing the risk of a so called bacteriaemia, which means that the risk of TB bacteria being spread via the blood or lymph-flow is reduced ( but not eliminated ).
It is highly unlikely that the European Veterinary Commission will ever accept that England is using the BCG vaccine for cattle. Why should they expose all other European countries which had managed to eradicate bovine TB ( bTB ) to the risk of reinfection? Much more likely is sooner than later a total import ban of any English livestock, dairy and beef products.
Sure bTB is a matter to be sorted out by veterinary science and not by laymen like politicians and musicians. It is obvious that in this country the way to deal with this very long known disease has utterly failed over the last 10 or even 15 years. There certainly are highly experienced and well respected senior veterinary epidemiologists in Europe. Why not asking one or two of those for advice what to do? It should have happened 10 or more years ago.
Finally I am amazed that in all the discussions about bTB, the testing of dairy and beef herds and biosecurity on farmyards the role of pet cats is never mentioned. Cats can carry bTB and being a veterinary surgeon myself I do remember very well the one single cat we had finally sorted out in my home-country some 35 years ago to have infected and reinfected 3 different dairy herds in one bigger hamlet over almost 2 years. To diagnose TB in a cat the usual intra-dermal test is not reliable. The only way to do it is by radiography or by long lasting cultures of dubious excretions.
Dr. Ueli Zellweger, MRCVS, GST, GThT
We are grateful for Dr. Zellweger's insight.

A further comment from virolgist, Dr. Ruth Watkins can be found on www.warmwell on this link.

No comments: