Experimental infection of Eurasian wild boar with Mycobacterium avium subsp. avium

The Eurasian wild boar (Sus scrofa) is increasingly relevant as a host for several pathogenic mycobacteria. We aimed to characterize the first experimental Mycobacterium avium subsp. avium (MAA) infection in wild boar in order to describe the lesions and the immune response as compared to uninfected controls. Twelve 1–4-month-old wild boar piglets were housed in class III bio-containment facilities. Four concentrations of MAA suspension were used: 10, 102 and 104 mycobacteria (2 animals each, oropharyngeal route) and 2.5 × 106 mycobacteria (2 animals each by the oropharyngeal and nasal routes). No clinical signs were observed and pathology evidenced a low pathogenicity of this MAA strain for this particular host. Bacteriological and pathological evidence of successful infection after experimental inoculation was found for the group challenged with 2.5 × 106 mycobacteria. These four wild boar showed a positive IFN-γ response to the avian PPD and the real-time RT-PCR data revealed that three genes, complement component C3, IFN-γ and RANTES, were significantly down regulated in infected animals. These results were similar to those found in naturally and experimentally M. bovis-infected wild boar and may constitute biomarkers of mycobacterial infection in this species.