Immunological and molecular characterization of susceptibility in relationship to bacterial strain differences in Mycobacterium avium subsp paratuberculosis infection in the red deer (Cervus elaphus)

Johne's disease (JD) infection, caused byMycobacterium aviumsubsp.paratuberculosis, represents a major disease problem in farmed ruminants. Although JD has been well characterized in cattle and sheep, little is known of the infection dynamics or immunological response in deer. In this study, typing ofM. aviumsubsp.paratuberculosisisolates from intestinal lymphatic tissues from 74 JD-infected animals showed that clinical isolates ofM. aviumsubsp.paratuberculosisfrom New Zealand farmed red deer were exclusively of the bovine strain genotype. The susceptibility of deer toM. aviumsubsp.paratuberculosiswas further investigated by experimental oral-route infection studies using defined isolates of virulent bovine and ovineM. aviumsubsp.paratuberculosisstrains. Oral inoculation with high (109CFU/animal) or medium (107CFU/animal) doses of the bovine strain ofM. aviumsubsp.paratuberculosisestablished 100% infection rates, compared to 69% infection following inoculation with a medium dose of the ovine strain. The high susceptibility of deer to the bovine strain ofM. aviumsubsp.paratuberculosiswas confirmed by a 50% infection rate following experimental inoculation with a low dose of bacteria (103CFU/animal). This study is the first to report experimentalM. aviumsubsp.paratuberculosisinfection in red deer, and it outlines the strong infectivity of bovine-strainM. aviumsubsp.paratuberculosisisolates for cervines.