Well it’s been an interesting, if slightly depressing day. Went out to check a sett at lunchtime, with one of our committee. A dedicated lady who has checked the setts on this site every day for months. This was her first return since a two week holiday. It had been dug in her absence. Rotten luck.
It’s the kind of site I have come to recognise. Big, lots of setts, but low badger activity, and an abundance of evidence of digging. Sigh. What more can we do??
I come home and open my email, where there are more reports of NFU scientific statements. I’m sorry, but this does not constitute peer review. But it depresses me because I know if it looks like science, then it can pass for science if it’s pushed hard enough on an unwitting public.
But then I opened hootsuite, and a tweet jumped out at me. There is a badger supporter by the name of Brockwatcher, he knows his stuff, and sometimes he pulls out a gem of information that I’m grateful to read. His latest is regarding anergy.
“Anergy is a term in immunobiology that describes a lack of reaction by the body’s defense mechanisms to foreign substances, and consists of a direct induction of peripheral lymphocyte tolerance.” – Wikipedia
Or in simple terms, the body does not produce a reaction to pathogens. Effectively, the cells in the body responsible for recognising pathogens, don’t. Where is all this leading?
Well, it’s like this. The skin test works by testing for the mild reaction to tb within the needles. If a cow’s lymphocytes recognise the bacterium, they will go into defence mode, and a reaction shows on the surface of the skin. Thereby showing that the cow has already been in contact with the disease, it is then termed a ‘reactor’ and must be destroyed. If the cow is anergic, it will not react to the bacterium. Even if it has tb.
If a cow can take 11 (yes 11) tb skin tests, and pass as negative, thus going on to infect her calves over a period spanning 5 years (2003-2008) before the gamma interferon test picks up that she has tb (shown here; TB Anergic Cow With Tuberculin Mastitis)…..could this not have something to do with the mystery herd breakdowns currently being attributed to badgers?
Not only that, but it’s not just one cow…..
“A severe outbreak of bovine tuberculosis in a 1300-head, multisite dairy herd in Great Britain had several unusual features, including anergy to the tuberculin skin test, milkborne disease in calves and a farm cat, and a risk of human infection. The outbreak was controlled by culling 221 cattle over 15 months, by using the
-interferon (
But that’s still not all…apparently cows can become anergic at certain times, namely when giving birth, due to a reduction in their immune response.
“It has long been known that early and late cattle TB cases are the usual cause of recrudescence in herds supposedly tested as clear of the disease. A study some twenty years ago claimed that some 0.30 of cows go temporarily anergic or non-reactor after parturition. Pregnancy certainly modifies the immune response, allowing a proliferation of lesions, followed by their regression post-partum. Young heifers may carry latent TB until their first pregnancy activates the disease (Francis 1947). And so seemingly, a significant minority become permanently anergic yet active TB spreaders (Blood 1989). In fact three such anergic cases caused some 18 herd breakdowns in one parish in the West Penwith or Lands End area of Cornwall (Richards 1972).” M Hancox The Great Badger and Bovine Tb Debate
So what does this mean?
To me, it means that the skin test is not effective enough. It means that cattle that have tested negative, may be positive, and when there seems to be no reason at all for a herd breakdown, except the local badgers, in fact, there could be a cow with tb, or could have been a cow with tb, now sold on to pass the bacterium on somewhere else.
Not only that, but I also discovered today that tb can be passed in water, downstream perhaps? And since a cow can pass 38 million bacilli/day in their faeces, that’s a lot of potential baccilli passing into the local stream. How do we know that this isn’t causing outbreaks?
Anergy, how is it that this is such a little known concept in the tb debate?
