If not badgers, then how is bTB spread?
Recycling infection in the herd through inaccurate testing:
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The Government policy depends heavily on the skin test which Government scientists estimate to be only 50-80% accurate. So up to half of the bTB-infected cattle go undetected & therefore remain in the herd.
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Even where accurate, the skin test only detects infection at an advanced stage once antibodies have developed. By this time, the animal may well have spread infection.
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Cattle identified as infected are not removed immediately; farmers have up to 10 working days to remove infected cattle, during which time they can spread the disease to other cattle.
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Inaccurate testing leaves an undetected reservoir of infection in the herd, carrying a high risk of repeat outbreaks even after a herd has had the ‘all clear’. Infection can also be spread to unborn calves.
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Cattle farmed intensively in stressful conditions in the close confines of a barn are thought to be more susceptible to disease.
Manure and slurry:
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bTB can be spread through ingestion as well as via respiration. Infected cows shed bacteria in their dung at a very high rate, with just 1 gram containing enough bTB organisms to infect another cow (Sibley)
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Bacteria can survive for months in slurry which may be spread on pasture and can be washed into streams.
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There is thus a high risk of infection spreading to:
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cattle kept in barns.
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cattle grazing on pastures on which slurry has been spread.
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badgers eating earthworms, slugs, snails etc, infected by slurry.
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Infection may also spread to neighbouring farms via transmission on slurry lorries or via the watercourse.
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Fears have also been raised that hunts traversing farms may be spreading infection to previously bTB free farms.
Cattle movements – bTB on tour:
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The huge number of cattle movements every year within and between different risk areas (eg. over 1.7 million in 2016) risks new infections.
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Live auctions bring together hundreds of cattle from a wide regional catchment.
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Risk-based trading, whereby purchasing decisions are informed by cattle and environmental data, is currently voluntary and poorly supported;
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The same unreliable skin test is used for testing the vast number of annual cattle movements. If only 50% of infected cattle are identified by the test, this leaves huge numbers of infected cattle moving from county to county. Hence, the disease is spreading throughout the UK.