Role of Wildlife in the Epidemiology of Mycobacterium bovis 101
7.4 ConclusionsM. bovis has one of the widest host ranges of any
known zoonotic pathogen (O’Reilly and Daborn,
1995). Compounding the complexity of multi-
species transmission dynamics is the inter- and
intra-species variation in pathology, excretion
potential, susceptibility, and interactions
between infected and susceptible individuals.
With a multitude of hosts and profusion of
potential transmission mechanisms, resultant
patterns of transmission within ecosystems are
complex and remain poorly understood. Charac-
terization of a species’ role as a maintenance or
spillover host is not static – it varies with a pleth-
ora of local factors. For example, as host status is
often density dependent, classifications as main-
tenance or spillover are likely to be indistinct as
densities fluctuate with time, space and
management. Consequently, the epidemiology
of M. bovis across different host communities
can be seen as highly variable, with potentially
unique conditions underlying its emergence and
persistence in each ecosystem. That wild boar
are considered spillover hosts in North-West
Italy (Dondo et al., 2007) but are considered as
maintenance hosts in parts of Spain (Naranjo
et al., 2008) reflects this variability. Similarly,
deer are thought to be spillover hosts in New
Zealand, yet they are considered as true mainte-
nance hosts in Michigan. Such variations have
repercussions for control and surveillance strat-
egies, which should be tailored to fit the host
community composition and structure in each
region. Although it remains primarily a disease
of cattle there is huge potential for wildlife to
play a role in the epidemiology of M. bovis in live-
stock. Perhaps the best evidence of this is that
disease control in livestock is more difficult in
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