Bovine TB: Research project summary
Project SE3020: An integrated approach to the application of M. bovis genotyping for the control of bovine tuberculosis in GB.
Project duration: 3 year 6 months
The aim of this project was to investigate the combined use of molecular and phenotypic methods with spatial analysis to aid epidemiological analysis of bovine tuberculosis (bTB) in cattle and wildlife. Analysis of the population structure of M. bovis in GB revealed that 94% of all strains belong to either spoligotype 9 or a descendant spoligotype. Understanding the reasons for such clonal expansion may help to identify ways of controlling the spread of bTB in Great Britain.
The strain-groupings generated by phenotypic analysis, closely mirrored those generated by molecular methods, indicating that the clonal groups of M. bovis share distinct phenotypic characteristics. These differences may result in differences in virulence, transmission, or the ability to evade the tuberculin skin test. Analysis of the genetic makeup of M. bovis AN5, used for production of PPD (Purified Protein Derivative) for the tuberculin skin test, revealed it to have a different profile from all other strains in the database. This suggests that AN5 may not be the optimal strain for detection of M. bovis infection. The distinct phenotypes of different clonal groups may also be relevant to the disease control strategy and may explain why particular M. bovis strain-groupings are more likely to be inconclusive reactors to the skin test. Further investigations into this are being taken forward in Defra project SE3220 - Molecular and Epidemiological Characterisation of the PPD Diagnostic Reagent.
This study has also demonstrated that the TB99 epidemiological questionnaire,
the Vetnet disease management database, CTS (Cattle Tracing System) data,
and the Veterinary Laboratories Agency’s molecular typing database
together provide a powerful tool for investigating the source of bTB breakdowns.
A prototype system has been developed to allow statistical analysis for
the complex spoligotyping dataset, and display maps on the location of
farms on which reactor animals are identified.
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Page last modified:
July 7, 2008