Category: Livestock

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Culling badgers backfires

There’s been a lot of news and discussion recently in the UK on animal diseases such as mad cow, foot and mouth, and bluetongue. Here’s another one to worry about: bovine tuberculosis. A paper just out in the Journal of Applied Biology explores the interaction between agricultural and wild biodiversity in the context of the spread of this disease in the UK ((H.E. Jenkins et al. (2007) Effects of culling on spatial associations of Mycobacterium bovis infections in badgers and cattle. Journal of Applied Ecology 44 (5), 897–908. doi:10.1111/j.1365-2664.2007.01372.x)).

Bovine tuberculosis can be spread by badgers, which have therefore been routinely culled for some years in many areas. But it turns out that badgers are in fact more mobile and adventurous in areas where their numbers have been thinned out. Which means they are most effective in spreading tuberculosis to cattle in exactly those areas where measures have been taken which were supposed to control the disease. The law of unintended consequences in action, I suppose.

Meanwhile, a big cull of feral pigs is on in Australia. ((Our occasional contributor Michael Kubisch wrote an interesting post on feral animals a few months back.)) Is this going to have some unintended consequences too?

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Animal diseases reviewed

Thanks to Danny Hunter for pointing to two recent posts at CABI’s blog, one on bovine spongiform encephalopathy (mad cow disease to you and me), the other on bluetongue disease. BSE seems to be running its course and to be more or less under control, even though many mysteries still surround it. Bluetongue, however, is altogether more menacing, because it seems to have reached Britain at least partly as a result of climate change, which has allowed the midges that spread the virus to expand their range. This could be the start of something big. I don’t believe there is any resistance associated with different breeds of cattle, but I could be wrong.

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The spread of agriculture into Europe

You may recall a post a few days back on how domestic pig keeping spread into Europe. Well, Razib over at Gene Expression, a genetics blog, has a post today which includes a map of the spread of agriculture north and west from the Middle East. He points out that current thinking is that either the practice of agriculture did the spreading (cultural diffusion), or people themselves (demic diffusion) — or both. Both was what the pig work implied, of course. Human genetic studies suggest that Neolithic people have made a fairly low (maybe 20%) contribution to European ancestry, and Razib summarizes the current debate about whether that therefore refutes the hypothesis that movement of people was involved in the spread of agriculture, as well as that of ideas. Bottom line: it probably doesn’t.

He also links to a recent paper that calculates a figure for the rate of movement ((Tracing the Origin and Spread of Agriculture in Europe. Pinhasi R, Fort J, Ammerman AJ. 2005. PLoS Biology Vol. 3, No. 12. doi:10.1371/journal.pbio.0030410)): 1 km/year, give or take. That was arrived at by interpolating radiocarbon dates of Neolithic archaeological sites across Europe, and it fits very well with the results of models using human genetic data. ((As far as I’m aware, however, nobody’s done anything similar with crops.)) An interesting way to think about that speed of movement is that it is roughly a one-day walk per generation.