Progress in Oral Vaccination against Tuberculosis in Its Main Wildlife Reservoir in Iberia, the Eurasian Wild Boar

Abstract

<jats:p>Eurasian wild boar (<jats:italic>Sus scrofa</jats:italic>) is the main wildlife reservoir for tuberculosis (TB) in Iberia. This review summarizes the current knowledge on wild boar vaccination including aspects of bait design, delivery and field deployment success; wild boar response to vaccination with Bacillus Calmette-Guérin (BCG) and inactivated Mycobacterium bovis; and wild boar vaccination biosafety issues as well as prospects on future research. Oral vaccination with BCG in captive wild boar has shown to be safe with significant levels of protection against challenge with virulent<jats:italic>M. bovis</jats:italic>. An oral vaccination with a new heat-killed<jats:italic>M. bovis</jats:italic>vaccine conferred a protection similar to BCG. The study of host-pathogen interactions identified biomarkers of resistance/susceptibility to tuberculosis in wild boar such as complement component 3 (C3) and methylmalonyl coenzyme A mutase (MUT) that were used for vaccine development. Finally, specific delivery systems were developed for bait-containing vaccines to target different age groups. Ongoing research includes laboratory experiments combining live and heat-killed vaccines and the first field trial for TB control in wild boar.</jats:p>

Assessment of an Oral Mycobacterium bovis BCG Vaccine and an Inactivated M. bovis Preparation for Wild Boar in Terms of Adverse Reactions, Vaccine Strain Survival, and Uptake by Nontarget Species

“…However, several issues related to protection against infection but also animal and environmental biosafety need to be addressed before this becomes a feasible option (1,4,8). In this work, we report on relevant safety issues related to administration of the vaccine to wild boar and to bait deployment.…”

“…Wildlife vaccination is increasingly being considered among the different options available for TB control at the wildlife-livestock interface (4)(5)(6)(7).…”

“…Important points to take into account with BCG vaccination are that (i) viability must be maintained until delivery and uptake and (ii) the consequent immune response must confer protection (10). In addition, key considerations in designing a vaccine bait delivery strategy are (i) adverse reactions and potential effects of high vaccine doses on the health of target animals, (ii) potential survival of M. bovis BCG in vaccinated individuals, (iii) potential excretion of M. bovis BCG by vaccinated animals, and (iv) vaccine-containing bait uptake by nontarget species (4).…”

“…Wild boar (Sus scrofa) is the main wild reservoir of TB in Spain (1); therefore, recent research has focused on immune responses in this species and the protection conferred after oral immunization with BCG and a prototype based on a heat-inactivated M. bovis preparation (4,33,34). Target animals for vaccination are 3-to 4-month-old piglets (28,32) (an age usually achieved by early summer).…”

Animal Tuberculosis as a Potential Danger to Men

“…In the United Kingdom, the biggest natural reservoir of M. bovis is the population of the badgers [9], while in Spain of the boars [10]. Transmission of bTB can occur on joint pastures, or rarely, through the bite of a sick animal.…”