20 F. Olea-Popelka et al.
presence of M. bovis in raw milk samples
obtained from cows in Tunisia, and warned that
consumers of raw milk (or dairy products) are at
high risk of zoonotic TB. Ereqat et al. (2013) for
the first time isolated M. bovis from milk of
apparently healthy animals (cattle and goats) in
the West Bank in Palestine. In Brazil, Zarden
et al. (2013), reported the isolation of M. bovis
from milk samples from cows testing negative to
the intradermal tuberculin test, the most com-
monly used test to identify cattle infected by
M. bovis. Franco et al. (2013) concluded that in
Brazil, consumption of raw bovine milk (or dairy
products) may be regularly exposing human
populations to mycobacteria. Roug et al. (2014)
conducted a simulation model to evaluate strat-
egies to reduce human exposure to M. bovis in
pastoralist households of Tanzania. The authors
concluded that heat treatment of milk may be
an effective strategy to reduce human exposure
to M. bovis-infected milk in settings where TB in
cattle is endemic and a bovine TB control pro-
gramme is not available. Michel et al. (2015) in a
study conducted in agro-pastoral farming com-
munities in South Africa, showed that M. bovis
may survive in fresh and souring milk for periods
of time that represent a risk for people consum-
ing these products. Additionally, this study
demonstrated an association between the tem-
perature at which the milk was soured and
stored and the survival time of M. bovis. All of
the M. bovis concentrations inoculated into milk
yielded viable M. bovis in milk at both tempera-
tures (20°C and 33°C). M. bovis survived for at
least 2 weeks at 20°C; however, at all different
M. bovis concentrations tested at 33°C, M. bovis
was absent within 3 days after inoculation. At
higher temperatures (33°C), different M. bovis
tested concentrations survived between 1 to 3
days. Thus, the public health implications of
milk (and milk products) potentially containing
M. bovis should not be underestimated.
On the other hand, there are areas in low-
income countries where pasteurization is
available but yet communities still consume
unpasteurized milk. In Ethiopia, for example,
unpasteurized milk was more consumed in
urban and peri-urban areas where pasteuriza-
tion is expected to be available and accessible
(Desissa and Grace, 2012). In this study the
observed significant difference in consumption
behaviour was due to lack of awareness of the
associated risk as well as engrained cultural con-
sumption habits (Dessissa and Grace, 2012).
Such findings emphasize the fact that socio-
cultural aspects of communities, especially food
consumption habits, are critical but challenging
to change, hence can be barriers to defining and
implementing risk mitigations strategies.2.3.2 Consumption of raw meatConsumption of meat (muscle mass) has not
been documented as a concern regarding trans-
mission of M. bovis to humans. In 2003, the
UK Food Safety Agency reviewed the possible
health risks to consumers of meat from cattle
with evidence of M. bovis infection (Food Stan-
dards Agency, 2003). In this qualitative review,
the authors concluded that: ‘the risk, if any,
from the consumption of meat sold as fresh meat
for human consumption following assessment
and action by the Meat Hygiene Service staff in
UK abattoirs is very low’ (Food Standards
Agency, 2003). In New Zealand, a report con-
cluded that there was no evidence that M. bovis
infections in humans were caused by consump-
tion of meat (Cressey et al., 2006). In the Repub-
lic of Ireland, the Food Safety Authority
indicated that the scientific information avail-
able did not permit a quantitative risk assess-
ment regarding M. bovis in meat (Food Safety
Authority of Ireland, 2008); however, this
report indicated that ‘on the basis of available
evidence, it is reasonable to conclude that the
occurrence of viable M. bovis in the muscle mass
of cattle, and of other food-producing animals
infected with M. bovis, is uncommon’. Addition-
ally, it was concluded that the risk from the con-
sumption of meat sold for human consumption
following official inspection in abattoirs in
Ireland was very low.
Most tuberculous lesions found in cattle at
slaughter are confined to the lymph nodes asso-
ciated with the head, thorax and, less commonly,
abdomen. Other organs including the lungs,
liver, spleen, kidneys and mammary gland along
with the associated lymph nodes and related
serous surfaces (pleura and peritoneum) are
other less common sites of infection (Corner,