Skin lesions caused by Mycobacterium ulcerans have been detected in several wild and domesticated animals like possums, alpacas, koalas, horses, cattle, cats and dogs. They occur mainly at places where no or only sparse fur is present: the ears, paws and the nose. To date such naturally infected animals have only been detected in Australia. In order to tackle specific research questions in vivo, several experimental M. ulcerans infection animal models have been developed, of which the majority is in mammals (armadillos, grass cutters, guinea pigs, mice, rats, pigs and monkeys). The mouse model, in which bacteria are usually inoculated into the foot pad, the ears or the tail, is by far the most commonly used experimental animal infection model to study Buruli ulcer (BU). In most mouse strains the injected M. ulcerans are successfully multiplying, allowing a multitude of applications for the model, as for example the testing of new antimicrobial compounds or vaccine candidates for BU. The histopathological appearance of the lesions and the spreading of the bacteria to the lymph nodes, however, are quite different to what is observed in the human disease. In order to overcome these disadvantages, the pig as a model for BU was recently introduced and appears to mimic the early stages of the infection of the human skin more accurately. Lesions comparable to human BU lesions develop in pigs after inoculation of M. ulcerans, although over time bacilli do not seem to be able to cause a chronic infection.
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