Bovine tuberculosis (BTB)
Author: Prof Anita Michel
Licensed under a Creative Commons Attribution license.
Introduction
detection. While clinical signs are non-specific and
Bovine tuberculosis is a chronic, debilitating disease
often remain unnoticed in the early stages of the
primarily of livestock, which causes production losses
disease,
and constitutes a zoonotic risk to humans. Economic
emaciation and coughing.
advanced
cases
are
characterized
by
losses are due to condemnation of carcasses at
abattoirs as well as national and international trade
barriers for infected cattle. The aetiological agent,
Mycobacterium
bovis,
is
closely
related
to
Mycobacterium tuberculosis, the cause of human
tuberculosis.
Salient features of BTB
Apart from cattle which serve as the main reservoir for
bovine tuberculosis, the disease can affect a wide
Severe tuberculous pneumonia
range of other domestic and wild animal species. A
number of different wildlife reservoirs, inter alia the
African buffalo (Syncerus caffer), European badger
(Meles meles) and possum (Trichosurus vulpecula)
have successfully established themselves and are
responsible for spillover infections to other free-ranging
species living in the same ecosystem. The impact of
bovine tuberculosis on the population dynamics of
these spillover species can vary significantly and has
only recently been researched. In domestic and wild
Tuberculous pleuritis. Areas of the lung have adhered to the
ruminants the pathology of bovine tuberculosis is
parietal pleural surface
characterized by granulomatous lesions (tubercles)
typically located in the respiratory tract, owing to the
Where does BTB occur?
fact that aerosol transmission is the primary mode of
Bovine tuberculosis was present in the Mediterranean
infection. Generalised disease following the spread of
area before the rise of the Greek Empire and spread
the bacilli via the blood stream is observed during the
from there to the rest of Europe. In the mid 1800s it
terminal stages of bovine tuberculosis. Visible lesions
spread to many other parts of the world, including
generally take several months to develop during which
Africa. During the 20th century the disease had a
animals may escape both ante- and post mortem
worldwide distribution, but as a result of the
implementation of eradication programmes, especially
herds
classified
as
infected
are
placed
under
in the developed world, many countries have now
quarantine with repeat testing and slaughter of all test
achieved a bovine tuberculosis free status. In large
positive animals until the herd is considered free of
parts of the developing world, however, no eradication
infected animals. The interferon gamma assay is an
or control measures for bovine tuberculosis exist and
ancillary test which can be used for increased
often no information on the occurrence of the disease
sensitivity in the eradication of bovine tuberculosis from
is available. Under these circumstances the risk of
so-called problem herds.
spillover infection of M. bovis to humans is highest as
milk is largely consumed unpasteurised. At the same
Once bovine tuberculosis has established itself in a
time a high incidence of human tuberculosis is the
wildlife population it is considered impossible to
reason that diagnostic services generally do not make
eradicate
provision for differentiation between tuberculous
impractical and too expensive to apply. Vaccination
agents.
has been discussed as the only practical option to
as
a
test-and-slaughter
approach
is
control bovine tuberculosis in countries where a wildlife
Despite the success in the eradication of bovine
reservoir of the disease is present. Although at present
tuberculosis in cattle the establishment of wildlife
no vaccine with proven efficacy exists for immunizing
reservoirs has led to the recurrence of the disease in
animals or humans, recent research has shown
some countries (e.g. UK and New Zealand) and is
promising results in animal experiments.
posing a new threat to the livestock sector.
Find out more
What triggers an outbreak of BTB?
The CPD module on bovine tuberculosis describes, on
Movement of infected cattle to previously uninfected
the
herds is the main cause of new outbreaks of bovine
pathogenesis to refresh the basic knowledge on the
tuberculosis. This may be facilitated by the lack of
topic. On the other hand the module places a large
reliable diagnostic tools for early identification of
emphasis on the epidemiology and implications of the
outbreaks, a lack of adequate quarantine measures or
disease on the wildlife/lllivestock/human interface
non-compliance by farmers with quarantine measures.
including its socio-economic effects.
In situations of uncontrolled contact between livestock
Other relevant CPD courses
and wildlife, also referred to as the wildlife/livestock

interface, bovine tuberculosis can be freely transmitted
between them. As disease monitoring and intervention
is extremely difficult at the interface, outbreaks often
remain undetected.
Prevention and control
The control of bovine tuberculosis in cattle traditionally
relies on the use of the tuberculin skin test in
combination with the slaughter of positive reactor
animals. For this purpose, the control scheme requires
all cattle herds to be tested at regular intervals and
one
hand,
the
disease
Laboratory Diagnostics
characteristics
and