Bovine tuberculosis

214 B.M. Buddle et al.

Consumption of oral bait BCG vaccine by pos-
sums resulted in the shedding of relatively low
concentrations of BCG, 10^2 –10^4 CFU/g faeces
for up to a week (Wedlock et al., 2005b).
An encouraging result from a recent 2-year
field trial involving oral vaccination of possums
was that BCG vaccine had a 95% efficacy in pre-
vention of TB (Tompkins et al., 2009). This result
was different to that observed in experimental
challenge studies where BCG vaccination
resulted in a significant reduction in the severity
of the pathology, but did not prevent infection
(Aldwell et al., 2003; Buddle et al., 2006). These
results indicated that the experimental chal-
lenge with M. bovis was more severe than that
from natural exposure with M. bovis. There is
potential for the development of new tuberculo-
sis vaccines for wildlife that perform better than
BCG. Collins et al. (2011) have produced a newly
attenuated M. bovis vaccine that gave more mea-
sures of protection in possums against aerosol
M. bovis challenge than BCG.

14.5.2 Vaccination of badgers

The European badger is the major wildlife reser-

voir of M. bovis infection in the British Isles due to

their relative abundance and ecology, the preva-

lence of infection and presentation of TB pathol-

ogy compared to other sylvatic species (Delahay

et al., 2007; Godfray et al., 2013). Badgers are

relatively resistant to the development of TB fol-

lowing infection with M. bovis, and latent infec-

tion without clinical signs or visible lesions at

necropsy is not uncommon (Corner et al., 2011).

In badgers, TB is a chronic, slowly progressing

disease. As such its presentation can vary along a

spectrum from latent infection through to lesions

widely spread throughout the body (Corner et al.,

2011). As lesions are found predominantly in the

lungs it is believed that aerogenic acquisition and

transmission of infection is the principal mode

of transmission. More disseminated infection is

thought to occur through bite wounding via the

transmission of M. bovis within saliva.

Table 14.2. Summary of TB vaccine efficacy studies in wildlife.

Species/
country

Vaccine/

routea Challenge type

Vaccine

efficacybNotes/particular issues Key references

Brushtail
possum/New
Zealand

BCG/

O,M,P

Aerosol,

natural

exposure

+

+

High vaccine cost compared

to that for poisons

Aldwell et al., 2003;
Tompkins et al.,
2009
European
badger/UK,
Ireland

BCG/

O,M,P

Endobronchial,

natural

exposure

++ Parenteral vaccine licensed

(BadgerBCG™)

For an oral vaccine:

demonstration of

consistent protection and

definition of minimal

efficacious dose

Chambers et al.,

2014

Murphy et al., 2014;

Carter et al., 2012

White-tailed
deer/USA

BCG/O,P Intratonsilar + BCG persistence in tissues,

bans on supplementary

baiting, non-target update

Nol et al., 2008;

Palmer et al.,

2009

Eurasian wild
boar/Spain

BCG/O,P

Killed

M. bovis/

O,P

Oral

Oral,

Natural

exposure

+

+

+

Non-target bait uptake

Regulatory issues

Gortázar et al.,
2014
Beltrán-Beck et al.,
2014a, 2014b;
Díez-Delgado
et al., 2016
Ferret/New
Zealand

BCG/O,P Oral ± Rarely maintenance host for

M. bovis

Qureshi et al., 1999;
Cross et al., 2000
African buffalo/
South Africa

BCG/P Intratonsilar - Practicality of vaccine

delivery in the field

De Klerk et al.,

2010

a Vaccination route: O, oral; M, other mucosal; P, parenteral.
b Vaccine efficacy: +, protection; ±, partial protection; −, no protection