Effects of culling on spatial associations of Mycobacterium bovis infections in badgers and cattle

Authors

  • HELEN E JENKINS,

    1. Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, St. Mary's Campus, Norfolk Place, London W2 1PG, UK;
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  • ROSIE WOODROFFE,

    Corresponding author
    1. Department of Wildlife, Fish & Conservation Biology, University of California, One Shields Avenue, Davis, California 95616, USA;
    2. Independent Scientific Group on Cattle TB, c/o Department for Environment, Food & Rural Affairs, 1A Page Street, London SW1P 4PQ, UK;
      *Author to whom correspondence should be addressed: Tel. 530-754-9513; Fax: 530-752-4154; E-mail: rwoodroffe@ucdavis.edu.
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  • CHRISTL A DONNELLY,

    1. Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, St. Mary's Campus, Norfolk Place, London W2 1PG, UK;
    2. Independent Scientific Group on Cattle TB, c/o Department for Environment, Food & Rural Affairs, 1A Page Street, London SW1P 4PQ, UK;
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  • D.R COX,

    1. Independent Scientific Group on Cattle TB, c/o Department for Environment, Food & Rural Affairs, 1A Page Street, London SW1P 4PQ, UK;
    2. Nuffield College, New Road, Oxford OX1 1NF, UK,
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  • W.T JOHNSTON,

    1. Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, St. Mary's Campus, Norfolk Place, London W2 1PG, UK;
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  • F.J BOURNE,

    1. Independent Scientific Group on Cattle TB, c/o Department for Environment, Food & Rural Affairs, 1A Page Street, London SW1P 4PQ, UK;
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  • C.L CHEESEMAN,

    1. Central Science Laboratory, Sand Hutton, York YO41 1LZ, UK,
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  • R.S CLIFTON-HADLEY,

    1. Veterinary Laboratories Agency, Woodham Lane, Surrey KT15 3NB, UK,
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  • G GETTINBY,

    1. Department of Statistics and Modelling Science, University of Strathclyde, Richmond St, Glasgow G1 1XH, UK; and
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  • P GILKS,

    1. Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, St. Mary's Campus, Norfolk Place, London W2 1PG, UK;
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  • R.G HEWINSON,

    1. Veterinary Laboratories Agency, Woodham Lane, Surrey KT15 3NB, UK,
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  • J.P MCINERNEY,

    1. Independent Scientific Group on Cattle TB, c/o Department for Environment, Food & Rural Affairs, 1A Page Street, London SW1P 4PQ, UK;
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  • W.I MORRISON

    1. Centre for Tropical Veterinary Medicine, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Roslin, Midlothian EH25 9RG, UK
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*Author to whom correspondence should be addressed: Tel. 530-754-9513; Fax: 530-752-4154; E-mail: rwoodroffe@ucdavis.edu.

Summary

  • 1Bovine tuberculosis (TB), caused by Mycobacterium bovis, has serious consequences for Britain's cattle industry. European badgers (Meles meles) can transmit infection to cattle, and for many years the British government culled badgers in a series of attempts to reduce cattle infections.
  • 2We investigated the impact of badger culling on the spatial distribution of M. bovis infection in badger and cattle populations in replicated areas in England.
  • 3M. bovis infection was significantly clustered within badger populations, but clustering was reduced when culls were repeated across wide areas. A significant spatial association between M. bovis infections in badgers and cattle herds likewise declined across successive culls. These patterns are consistent with evidence that badgers are less territorial and range more widely in culled areas, allowing transmission to occur over greater distances.
  • 4Prior to culling, M. bovis infections were clustered within cattle populations. Where badger culling was localised, and in unculled areas just outside widespread culling areas, cattle infections became less spatially clustered as badger culling was repeated. This is consistent with expanded badger ranging observed in these areas.
  • 5In contrast, clustering of infection in cattle persisted over time on lands where badgers were repeatedly culled over wide areas. While this lack of a temporal trend must be interpreted with caution, it might reflect persistent infection within, and continued transmission between, cattle herds in areas where transmission from badgers to cattle had been reduced by badger culling. Continued spatial association of infections in cattle and badgers in such areas might partly reflect transmission from cattle.
  • 6Synthesis and applications: Our findings confirm that badger culling can prompt spatial spread of M. bovis infection, a phenomenon likely to undermine the utility of this approach as a disease control measure. Possible evidence of transmission from cattle, both to other cattle and to badgers, suggests that improved cattle controls might yield multiple benefits for TB management.

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