Mycobacterium bovis as the Agent of Human Tuberculosis: Public Health Implications 17
Müller et al., 2013; Perez-Lago et al., 2014).
Additionally, even where cultures are performed,
culture on standard Löwenstein-Jensen medium
cannot distinguish the two species (Afghani,
1998; Keating et al., 2005). Culture must be per-
formed using either pyruvate-supplemented
solid media or liquid culture systems. Thus, not
only are true incidence and burden poorly
understood, but there is also a general lack of
awareness (Thoen et al., 2010) on the impor-
tance, challenges and public health implications
posed by M. bovis as a causal agent of human TB
(Perez-Lago et al., 2014). This has resulted in
M. bovis being neglected and underestimated as
relevant data are not routinely captured by the
majority of national tuberculosis control
programmes.
In recent years, there has been a growing
number of publications highlighting the impor-
tance of M. bovis as a cause of TB in humans. For
example, in 2014, two reviews concluded that
effective diagnostic policies using existing (and
new) molecular epidemiology tools with the
integration of veterinary, human health and
wildlife sectors are needed in order to better
understand the true challenge posed by M. bovis
(Pal et al., 2014; Perez-Lago et al., 2014). In
2016, El-Sayed et al. (2016) published a review
highlighting the seriousness of M. bovis at the
human–animal interface, focusing mostly on
the importance of molecular epidemiological
studies related to M. bovis. Olea-Popelka and col-
leagues ‘called for action’ to address the global
challenges regarding the prevention, diagnosis,
treatment and control of human TB caused by
M. bovis (Olea-Popelka et al., 2017). All these
publications emphasize the need to consider the
microbiological, epidemiological and clinical
characteristics of M. bovis in order to improve
the prevention, diagnosis and treatment of
zoonotic TB patients.
Initially, the impetus for action to control
bovine TB came from evidence indicating that
M. bovis was zoonotic in nature and as such, a
threat both to the farming family caring for its
infected cattle and the wider population con-
suming meat and unpasteurized dairy products.
In high-income countries, the success of the
early bovine TB control campaigns (Michel et al.,
2009; Palmer and Waters, 2011), the introduc-
tion of universal meat inspection programmes
and the implementation of milk pasteurization
have shifted the emphasis away from the health
and social relevance of the disease in cattle to
the economic and trading implications of the
disease for both the beef and dairy industries
(Collins, 1999). Today, the number of humans
becoming infected by M. bovis and suffering
from zoonotic TB is relatively low (compared to
the number of those infected by M. tuberculosis)
in most high-income countries. However, the
scenario is likely to be very different in low- and
middle-income countries where bovine TB is
endemic and uncontrolled, and where animal
management practices, socio-economic and
cultural factors facilitate M. bovis transmission
to humans (Ayele et al., 2004; Michel et al.,
2009).
From a public health perspective, it is
imperative to understand, recognize and address
the challenges faced by TB patients infected with
M. bovis as patient treatment and care differ
in comparison to the most common form of
TB caused by M. tuberculosis. For example,
M. bovis is naturally resistant to pyrazinamide
(O’Donohue et al., 1985; Nieman et al., 2000),
one of first-line medications in the standard
treatment regimen of TB, and zoonotic TB
caused by M. bovis in humans is more commonly
associated with extra-pulmonary rather than
pulmonary TB (Dürr et al., 2013). Furthermore,
the epidemiology and most common transmis-
sion dynamics of M. bovis differ significantly
from those of the airborne disease caused by
M. tuberculosis. Furthermore, the risk for zoo-
notic TB increases in rural areas in developing
regions of the world where bovine TB is endemic
and/or people live in conditions that favour
direct contact with infected animals or animal
products, especially with consumption of unpas-
teurized milk and untreated animal products.
As we move from the era of the United
Nation’s Millennium Development Goals (United
Nations, 2016) into the Sustainable Develop-
ment Goals for the period 2016–2030, greater
emphasis is being placed on the importance
of adopting multidisciplinary approaches to
improving health. This is particularly relevant
for zoonotic diseases. In the context of the SDGs,
the World Health Organization’s (WHO) End TB
Strategy (WHO, 2015a) seeks to end the global
TB epidemic by 2035 and calls for diagnosis
and treatment of every TB case regardless of
the Mycobacterium species causing disease.