Bovine tuberculosis

70 R.A. Skuce et al.

whole-genome approaches are likely to become
the new standard for molecular epidemiology
(Didelot et al., 2012).

5.9 Conclusions

The population structure of M. bovis and the
performance characteristics of molecular and
genomic epidemiology support their use in
molecular surveillance and to answer detailed
epidemiological questions of direct policy rele-
vance. They should offer powerful and practical
‘decision-support’ tools for investigating the
maintenance and spread of bovine TB. These
approaches should more accurately identify
clusters and unsuspected transmission events,
particularly where the breakdown index case
can be identified as an ‘out of home range’ cattle
movement. This provides a unique opportunity
to monitor and quantify the extent, if any, of
secondary (cattle–cattle) spread within and
between herds, and any spillover/spillback
involving local wildlife.
The M. bovis population structure is partic-
ularly, maybe even uniquely, amenable to this
approach. Molecular and genomic epidemiology
has the performance characteristics to support
its use as a surveillance and investigative tool,
to monitor the efficacy of current control

programmes and future interventions. It has the

potential to refine the modelling and analysis of

detailed epidemiological questions. The applica-

tion to epidemiological and evolutionary studies

provides unique and valuable insights into the

current bovine TB epidemic.

There remain opportunities to investigate,

in a structured manner, what molecular and

genomic epidemiology data tell us about TB in

sporadic, multi-reactor, persistent, recurrent

and restocked herds, etc. It is predictable that

this technology will become more useful as the

epidemic (hopefully) declines. One reason why

human TB genomic epidemiology can currently

make stronger inferences about transmission

dynamics is that the epi-system is significantly

less complex. For bovine TB, there are multiple

exposed hosts (cattle and wildlife) and the poten-

tial for the environment to be contaminated.

Consequently, it is currently very challenging to

disaggregate these, especially at a local scale.

However, should TB in cattle be substantially

reduced, it will become relatively more straight-

forward to assess spillover and which wildlife

hosts/populations are spilling over. Pathogen

genotyping continues to unravel the biology of

mycobacteria and offers significant promise in

the fight against and prevention of the diseases

caused by these troublesome pathogens

( Wlodarska et al., 2015).

References

Aarestrup, F.M., Brown, E.W., Detter, C., Gerner-Smidt, P., Gilmour, M.W., et al. (2012) Integrating genome-
based informatics to modernize global disease monitoring, information sharing, and response. Emerg-
ing Infectious Diseases 18(11), e1.
Abernethy, D.A., Upton, P., Higgins, I.M., McGrath, G., Goodchild, A.V., et al. (2013) Bovine tuberculosis
trends in the UK and the Republic of Ireland, 1995–2010. Veterinary Record 172(12), 312.
Allen, A.R., Minozzi, G., Glass, E.J., Skuce, R.A., McDowell, S.W., et al. (2010) Bovine tuberculosis: the
genetic basis of host susceptibility. Proceedings Biological Sciences 277(1695), 2737–2745.
Allen, A.R., Dale, J., McCormick, C., Mallon, T.R., Costello, E., et al. (2013) The phylogeny and population
structure of Mycobacterium bovis in the British Isles. Infection, Genetics and Evolution 20, 8–15.
Allix, C., Walravens, K., Saegerman, C., Godfroid, J., Supply, P. and Fauville-Dufaux, M. (2006) Evaluation
of the epidemiological relevance of variable-number tandem-repeat genotyping of Mycobacterium
bovis and comparison of the method with IS6110 restriction fragment length polymorphism analysis
and spoligotyping. Journal of Clinical Microbiology 44(6), 1951–1962.
Ameni, G., Aseffa, A., Sirak, A., Engers, H., Young, D.B., et al. (2007) Effect of skin testing and segregation
on the prevalence of bovine tuberculosis, and molecular typing of Mycobacterium bovis, in Ethiopia.
Veterinary Record 161(23), 782–786.
Ameni, G., Desta, F. and Firdessa, R. (2010) Molecular typing of Mycobacterium bovis isolated from tuber-
culosis lesions of cattle in north eastern Ethiopia. Veterinary Record 167(4), 138–141.