The minipig as an animal model to study Mycobacterium tuberculosis infection and natural transmission

In endemic countries more than 20% of tuberculosis (TB) cases are in infants and children. Current animal models study TB during adulthood but animal models for infant TB are scarce. Here we propose that minipigs can be used as an animal model to study adult, adolescent and infant TB including natural transmission. In these studies, two-month old minipigs (representing infant age in humans) and six-month old minipigs (representing adolescence in humans) were infected via the aerosol route with hyper-virulent clinical strain W-Beijing Mycobacterium tuberculosis (Mtb) HN878 and were monitored for 11 or 36 weeks post-challenge, respectively. In the same studies, infected and unchallenged animals were housed together. Viable bacteria were recovered from pulmonary and thoracic lymph nodes from both -infected and their initially unchallenged natural contacts. Bacillary load, gross lesions and histopathology revealed similarities to the spectrum of disease observed in human TB. The study did not reach terminal end point, thus it was not possible to annotate definitive clinical symptoms of active TB. The results demonstrated that minipigs are experimental hosts of Mtb HN878, and the pathology developed in their lungs resembles pathological findings described in human TB. Importantly, within communities of Mtb infected minipigs natural transmission occurs.