18 F. Olea-Popelka et al.
Furthermore, in support of WHO’s End TB strat-
egy, the Stop TB Partnership released the fourth
edition of its ‘Global Plan to End TB, 2016–
2020: The Paradigm Shift’ (Stop TB Partnership,
2015) identifying cattle herders, farmers, dairy
workers and others as ‘key affected populations’
for the first time. The Global Research Alliance
for Bovine TB (GRAbTB), working under the
umbrella of One Health, is also a heartening
sign of progress. Thus, the current policy envi-
ronment is indeed favourable to pursue greater
awareness and investments in the prevention
and control of zoonotic TB. A One Health
approach to M. bovis that integrates human,
domestic and wild species, and environmental
health is further described in Chapter 3, this
volume.
In this chapter, we highlight the global
public health implications still posed today by
M. bovis as a source of human TB. Additionally,
we discuss the implications of the well-known
characteristics of M. bovis that must be consid-
ered when attempting to improve the preven-
tion, diagnosis and treatment of human TB
caused by M. bovis. Finally, we summarize data
that have become available in the past three
years and provide information regarding recent
activities implemented at a global scale support-
ing the design and implementation of strategies
aiming to address the major challenges remain-
ing related to the prevention, diagnosis and
treatment of human TB caused by M. bovis.
2.2 Estimates of the Global Burden of
Human TB Caused by M. bovis
The available and historical data including esti-
mates of TB caused by M. bovis in people globally,
regionally and nationally have been previously
published. In brief, Cosivi et al. (1998) conducted
a comprehensive global review and summarized
the available data on zoonotic TB due to M. bovis
in developing countries. The author concluded
that disease surveillance programmes for
M. bovis in humans should be considered a
priority and called for evaluation of the scale of
the zoonotic TB problem, especially in rural
communities and in the workplace. Fifteen years
later, Müller et al. (2013) conducted a systematic
review and meta-analysis of available zoonotic
TB data with the purpose of estimating the
global occurrence of zoonotic TB caused by
M. bovis. This latter study concluded that the
same challenges and concerns expressed 15
years previously by Cosivi et al. (1998) remain
valid, including lack of surveillance and appro-
priate diagnostic tools to correctly identify
M. bovis as the causal agent of human TB.
Historically, TB cases caused by M. bovis
have most often been reported as a relative pro-
portion of the total number of human TB cases,
obscuring the fact that even a relatively small
proportion of the approximately 10.4 million
estimated TB cases per year globally (WHO,
2016) still represents a considerable absolute
number of humans suffering from zoonotic TB,
disproportionally affecting poor and marginal-
ized communities. Furthermore, these available
proportions are usually not based on nationally
representative data, and instead they are often
derived from studies involving only specific and
selected groups of patients, such as those pre-
senting to tertiary referral hospitals (Cosivi et al.,
1998; Müller et al., 2013). In the past three
decades, most published data on zoonotic TB in
humans come from studies conducted within
different epidemiological settings (i.e. some stud-
ies have come from areas where bovine TB is or is
not endemic), without any standardization of
study design, such as population demographics,
patient inclusion criteria, sample size and labo-
ratory methods used to isolate and differentiate
M. bovis (Cosivi et al., 1998; Drobniewski et al.,
2003; Thoen et al., 2010; Müller et al., 2013;
Perez-Lago et al., 2014). Because of the lack of
accurate and representative data in developing
regions, incorrect extrapolation of data from
high-income, low TB burden countries has likely
resulted in the misconception that globally only
a small number of humans suffer from pulmo-
nary and extra-pulmonary TB caused by
M. bovis. Extrapolating available figures on zoo-
notic TB from high-income, low TB burden
countries to the global context is not warranted
(Thoen et al., 2010). Additionally, areas where
bovine TB is endemic sometimes overlap with
areas where HIV prevalence is high (i.e. in some
African countries). Consequently, it is not sur-
prising to find a considerable amount of variabil-
ity in the reported proportions of human TB
cases caused by M. bovis in different studies.
Without standardization of study design, the