Experimental cutaneous leishmaniasis with Leishmania tropica in albino hairless mice, Mus musculus

Abstract

Cutaneous leishmaniasis was produced in 90 hairless mice, Mus musculus, with cultures of two strains of Leishmania tropica (one isolated from an exogenous human case in Texas, and the other a gerbil strain from the USSR). The mice were inoculated intradermally in five areas of the dorsal side of the body. Most of the inoculated mice developed visible cutaneous leishmaniasis. The early lesions at the sites of inoculation were small red papules appearing within one to two months following inoculation; some of these papules disappeared after a few weeks, others became nodular or pustular. These lesions gradually enlarged and became ulcerated, measuring about 5 to 10 mm in diameter, and some persisted as long as 386 days. The edges of the lesions were usually raised, indurated, and pink; the adjacent skin showed no visible reaction. The centre of the ulcer was either moist or covered with a dry brownish-grey crust. In a few cases the lesions were very extensive and merged with each other, covering nearly two thirds of the dorsal body surface. Smears from the edges of the lesions were positive for the amastigote (aflagellar) form of L. tropica, which produced infections when inoculated into other hairless mice and grew readily in promastigote (flagellar) form on NNP-2 medium ( Packchanian, 1959 ) with suitable antibiotics ( Packchanian, 1957 ). Although mice were inoculated intradermally with L. tropica, several animals with extensive skin lesions of cutaneous leishmaniasis also developed generalized leishmaniasis. This was proved by positive blood culture tests for promastigotes (from 15 mice) and by demonstration of the amastigote form of L. tropica in various organs such as the spleen, liver, kidney, heart and lymph nodes. On the other hand, heart blood from 18 mice with small skin lesions when tested during 62 to 269 days following infection, yielded negative results for promastigotes. The mice were kept under observation (60 to 478 days) before they were killed or died. The results of this study have demonstrated that the hairless mouse, Mus musculus, is a suitable laboratory animal for studying experimental cutaneous leishmaniasis.