Despite the compulsory test and slaughter campaigns in cattle, bovine tuberculosis
(bTB) is still present in Spain, and the role of wildlife reservoirs is increasingly
recognized. We provide an update on recent progress made in bTB control in Spanish
wildlife, including aspects of epidemiology, surveillance, host-pathogen interaction
and wildlife vaccination. At the high densities and in the particular circumstances
of Mediterranean environments, wild ungulates, mainly Eurasian wild boar and red deer,
are able to maintain Mycobacterium bovis circulation even in absence of domestic livestock.
Infection is widespread among wild ungulates in the south of the country, local infection
prevalence being as high as 52% in wild boar and 27% in red deer. Risk factors identified
include host genetic susceptibility, abundance, spatial aggregation at feeders and
waterholes, scavenging, and social behaviour. An increasing trend of bTB compatible
lesions was reported among wild boar and red deer inspected between 1992 and 2004
in Southwestern Spain. Sporadic cases of badger TB have been detected, further complicating
the picture. Gene expression profiles were characterized in European wild boar and
Iberian red deer naturally infected with M. bovis. The comparative analysis of gene
expression profiles in wildlife hosts in response to infection advanced our understanding
of the molecular mechanisms of infection and pathogenesis, revealed common and distinctive
host responses to infection and identified candidate genes associated with resistance
to bTB and for the characterization of host response to infection and vaccination.
Ongoing research is producing valuable knowledge on vaccine delivery, safety and efficacy
issues. Baits for the oral delivery of BCG vaccine preparations to wild boar piglets
were developed and evaluated. The use of selective feeders during the summer was found
to be a potentially reliable bait-deployment strategy. Safety experiments yielded
no isolation of M. bovis BCG from faeces, internal organs at necropsy and the environment,
even after oral delivery of very high doses. Finally, preliminary vaccination and
challenge experiments suggested that a single oral BCG vaccination may protect wild
boar from infection by a virulent M. bovis field strain.
Copyright © 2011 Elsevier B.V. All rights reserved.