Whole genome sequencing reveals local transmission patterns of mycobacterium bovis in sympatric cattle and badger populations

Biek, R. , O'Hare, A., Wright, D., Mallon, T., McCormick, C., Orton, R.J. , McDowell, S., Trewby, H., Skuce, R.A. and Kao, R.R. (2012) Whole genome sequencing reveals local transmission patterns of mycobacterium bovis in sympatric cattle and badger populations. PLoS Pathogens, 8(11), e1003008. (doi:10.1371/journal.ppat.1003008)

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Whole genome sequencing (WGS) technology holds great promise as a tool for the forensic epidemiology of bacterial pathogens. It is likely to be particularly useful for studying the transmission dynamics of an observed epidemic involving a largely unsampled ‘reservoir’ host, as for bovine tuberculosis (bTB) in British and Irish cattle and badgers. BTB is caused by Mycobacterium bovis, a member of the M. tuberculosis complex that also includes the aetiological agent for human TB. In this study, we identified a spatio-temporally linked group of 26 cattle and 4 badgers infected with the same Variable Number Tandem Repeat (VNTR) type of M. bovis. Single-nucleotide polymorphisms (SNPs) between sequences identified differences that were consistent with bacterial lineages being persistent on or near farms for several years, despite multiple clear whole herd tests in the interim. Comparing WGS data to mathematical models showed good correlations between genetic divergence and spatial distance, but poor correspondence to the network of cattle movements or within-herd contacts. Badger isolates showed between zero and four SNP differences from the nearest cattle isolate, providing evidence for recent transmissions between the two hosts. This is the first direct genetic evidence of M. bovis persistence on farms over multiple outbreaks with a continued, ongoing interaction with local badgers. However, despite unprecedented resolution, directionality of transmission cannot be inferred at this stage. Despite the often notoriously long timescales between time of infection and time of sampling for TB, our results suggest that WGS data alone can provide insights into TB epidemiology even where detailed contact data are not available, and that more extensive sampling and analysis will allow for quantification of the extent and direction of transmission between cattle and badgers.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Trewby, Dr Hannah and O'Hare, Dr Anthony and Kao, Professor Rowland and Biek, Dr Roman and Orton, Dr Richard
Authors: Biek, R., O'Hare, A., Wright, D., Mallon, T., McCormick, C., Orton, R.J., McDowell, S., Trewby, H., Skuce, R.A., and Kao, R.R.
College/School:College of Medical Veterinary and Life Sciences > Institute of Biodiversity Animal Health and Comparative Medicine
Journal Name:PLoS Pathogens
Publisher:Public Library of Science
ISSN (Online):1553-7366
Published Online:29 November 2012
Copyright Holders:Copyright © 2012 The Authors
First Published:First published in PLoS Pathogens 8(11):e1003008
Publisher Policy:Reproduced under a Creative Commons License

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