Experimental leprosy with Mycobacterium lepraemurium in hairless mice (Mus musculus).

Forty-three homozygous albino hairless mice (Mus musculus) were inoculated intradermally on the head, back, sides and base of the tail with suspensions of lepromatous tissue containing numerous Mycobacterium lepraemurium (Hawaiian strain). Visible nodules were noted in all mice. These lepromatous nodules enlarged slowly and often merged with each other, covering up to two thirds of the dorsum. Several mice became blind during the course of the infection. All of the mice died or were killed 68 to 287 days following inoculation. Post-mortem examinations on representative mice showed, in addition to observed cutaneous lesions, generalized systemic murine leprosy. Smears and histological sections from nodules, skin, lymph nodes, spleen, liver, kidney, heart and lung were positive for acid-fast bacilli. The cysts in the skin (which are degenerated hair follicles filled with keratin-like material and which are one of the characteristics of hairless mice) contained scattered acid-fast bacilli, but no acid-fast globi. Ten mice with hair (M. musculus) which were used as controls did not reveal noticeable cutaneous nodules; however, all developed generalized visceral leprosy similar to that of the hairless M. musculus. Thus, hairless mice (with thymus) can be looked upon as a model for studying experimental cutaneous leprosy.