Mycobacterium bovis, but also M. africanum present in raw
milk of pastoral cattle in north-central Nigeria
Simeon I. B. Cadmus & Mohammed K. Yakubu &
Abdullahi A. Magaji & Akinbowale O. Jenkins &
Dick van Soolingen
Accepted: 12 February 2010
# Springer Science+Business Media B.V. 2010
Abstract Using deletion typing technique, five mycobac-
teria isolated from unpasteurised milk samples from cows
in north-central Nigeria were characterized as Mycobacte-
rium bovis (n=4) and M. africanum (n=1). This report
emphasizes that transmission between the animal and
human reservoir is a serious threat in Nigeria.
Keywords Mycobacterium bovis.Pasteurization.
National Population Commission
Regions of difference
In most African countries, consumption of unpasteurized
milk is a regular practice (Ayele et al. 2004) leading to
considerable risk of zoonotic infection with Mycobacterium
bovis and other mycobacteria. M. bovis has been isolated
earlier from unpasteurized milk and lesions of slaughtered
cattle in Nigeria, as well as from patients with pulmonary
and extrapulmonary tuberculosis (TB; Cadmus et al.
Most cow milk consumed in north-central Nigeria is
from livestock owners who are unaware of the public health
risks associated with bovine tuberculosis (BTB). To
estimate the risk of zoonotic transmission of mycobacteria,
we screened raw milk of pastoral cattle from north-central
Nigeria for these bacteria and identified them using a
Materials and methods
Study area The work was conducted at the South Agricul-
tural Zone of Niger State, north-central Nigeria.
Sample collection About 20 ml of milk was drawn from the
disinfected udder of selected cows into sterile universal
bottles from each of the 400 out of a total of 4,023 cattle
representing 10% of the 416 identified herds. Samples were
selected using the systematic sampling technique while the
herds were identified by physical randomization technique
Isolation of mycobacteria This was done as described by
Cadmus and Adesokan (2007), using Middlebrook 7H11
slopes and incubating at 37°C for 12 weeks.
S. I. B. Cadmus (*)
Department of Veterinary Public Health and Preventive Medicine,
University of Ibadan,
P.O. Box 21452, U.I. Post Office,
M. K. Yakubu:A. A. Magaji
Department of Veterinary Public Health and Animal Production,
Faculty of Veterinary Medicine, Usmanu Danfodiyo University,
P.M.B. 2346 Sokoto, Nigeria
A. O. Jenkins
Department of Veterinary Tropical Disease,
Faculty of Veterinary Sciences, University of Pretoria,
Pretoria, South Africa
D. van Soolingen
National Institute for Public Health and the Environment (RIVM),
3720 BA Bilthoven, The Netherlands
Trop Anim Health Prod
Deletion typing The RD9 deletion was used to distinguish Download full-text
Mycobacterium tuberculosis from other members of the M.
tuberculosis complex (MTC; Warren et al. 2006). Isolates
with a deletion in this region were further investigated with
primers specific for RD4. This reaction distinguishes
between M. bovis, M. caprae, and other MTC.
Results and discussion
Of the 400 milk samples, five (1.25%) were positive by
culture and further molecular analysis identified four M.
bovis and one M. africanum (Table 1). Herd and individual
animal prevalence amounted to 10% (4/40) and 1.25% (5/
We report the first molecular characterisation of M. bovis
and M. africanum from unpasteurised milk of pastoral cattle
in north-central Nigeria. This may be an important finding
considering that although people in this region suffer from
tuberculosis, there are no documented literature to show a
reliable identification of Mycobacterium humans are ex-
The findings indicate that there is high herd prevalence
of BTB in this region, leading to serious public health
implications. Therefore, since BTB is endemic in Nigeria, it
becomes imperative to carry out surveillance programs to
forestall zoonotic spread going by the reports of Hlavsa et
al. (2008) and Ayele et al. (2004) that approximately 1.4%
of human tuberculosis cases in the developed countries and
3.1% in the developing countries, respectively, could be
attributed to M. bovis.
It is noticeable that not only M. bovis, but also M.
africanum was isolated from milk of cows. It is known that
the latter species is more related to M. bovis than M.
tuberculosis, but it remains unclear whether it is also
transmitted among cows, or whether this is an accidental
transmission of M. africanum from humans to cows as
reported several times for M. tuberculosis. However, the
presence of M. africanum in milk hints at a disseminated
infection in the cow, and this is to our knowledge, not
reported for this bacterium.
The limitations of this study (i.e., screening of limited
numbers of animals and lack of collection of specimens
from tuberculosis patients in adjoining hospitals to link
them directly with the animals or consumption of milk
products as recently done by Byarugaba et al. (2009) in
Uganda) notwithstanding, the habit of pooling milk in this
region poses great danger to people who consume them raw
as fresh or fermented product.
In conclusion, there is the need for pasteurization of milk
from pastoral herds in Nigeria to prevent zoonotic trans-
mission of tuberculosis.
Adesokan and Dr. Charity Agada for technical assistance. We are also
grateful to Dr Femi Faleke for his support at the inception of the study.
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Table 1 Result of deletion typing
M. bovis M. africanum
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