Milk-and-Dairy-Products-in-Human-Nutrition-FAO

Chapter 6 – Safety and quality 247
Box 6.1
Mycobacterium bovis and tuberculosis
In developed countries, bovine tuberculosis (bTB) has been almost eradicated after
the implementation of control measures such as testing, culling of cattle and pasteurization
of milk. Properly controlled heat treatment of milk, e.g. pasteurization,
inactivates M. bovis and has had a major impact on reducing transmission. However,
bTB is re-emerging in some developed countries and there is a limited threat to public
health where unpasteurized raw milks and cheeses are consumed. In many developing
countries controls and surveillance systems are often inadequate or unavailable, bTB
is still highly prevalent in cattle, pasteurization is not widely practiced or is replaced
by boiling unpasteurized milk prior to consumption and milk hygiene and environmental
controls are insufficient; in such countries it is estimated that 10–15 percent
of human TB cases are caused by bTB (Ashford et al., 2001). Leite et al. (2003) report
that M. bovis accounts for about 5 percent of human tuberculosis cases in Brazil.
Most human tuberculosis cases caused by M. bovis occur in young people and result
from drinking or handling contaminated milk (Thoen, Lobue and de Kantor, 2006).
Furthermore, the HIV/AIDS pandemic poses an additional serious public-health threat
due to increasing incidence of tuberculosis/HIV/AIDS co-infection, especially where
bTB is prevalent in domestic and wild animals (Cosivi et al., 1998).
The proportion of tuberculosis cases in humans caused by bTB depends on the
prevalence of the disease in cattle, socio-economic conditions, consumer habits, food
hygiene practices and medical prophylaxis measures (Shitaye, Tsegaye and Pavlik,
2007). Reducing the prevalence of bTB in cattle in Ethiopia, for example, would
require improved knowledge on actual prevalence of the disease, addressing the
prevailing technical and financial limitations, provision of veterinary infrastructure
and overcoming cultural and/or traditional beliefs and geographical barriers (Shitaye,
Tsegaye and Pavlik, 2007). High prevalence of bTB in endemic areas is expected to
restrict sale and movement of livestock because of sanitary requirements of importing
countries.
present in raw milk and soft cheeses (Swaminathan and Gerner-Smidt, 2007), is
of significant public health concern as infection in pregnant women may result in
spontaneous abortions or stillbirth. An important factor in food-borne listeriosis is
that the pathogen can multiply at refrigeration temperatures when given sufficient
time (FAO and WHO, 2004a).
Outbreaks of pathogenic E. coli, including STEC and enteraggregative E. coli
(EAEC), have been attributed to a variety of dairy products, most often those
involving unpasteurized or inadequately pasteurized milk or raw milk products
(Fegan and Desmarchelier, 2010). STEC are carried by healthy adult dairy cattle and
have been detected in raw milk on farms although the enterohaemorrhagic E. coli
strains of STEC such as serotype 0157 have a much lower occurrence.
Cronobacter spp. have been linked with serious infections in infants (FAO and
WHO, 2004b, 2006a; Mullane et al., 2007), notably following the consumption of