Mystromys albicaudatus, the African White-Tailed Rat, as an Experimental Host for Leishmania donovani

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The course of Leishmania donovani infection was studied in the African white-tailed rat, Mystromys albicaudatus, and compared with that in the golden hamster, Mesocricetus auratus. All hamsters died at about 40 days postinoculation but the white-tailed rat survived with high levels of parasites for more than a year with no apparent ill effects or tendency to spontaneous recovery. The easily bred, long-lived white-tailed rat is an excellent experimental host for in vivo maintenance and long-term experiments with L. donovani. The white-tailed rat, Mystromys albicaudatus, a medium-sized rodent indigenous to the temperate, semiarid southeastern African savanna and coastal plains, is the only African representative of the subfamily Cricetinae (Hall et al., 1967). Other Cricetinae, the hamster and cotton rat, are highly susceptible to Leishmania donovani infection and are frequently used as experimental hosts (Stauber, 1958). M. albicaudatus was first adapted to the laboratory in 1941 (Davis, 1963) and later used in research on schistosomiasis (Pitchford and Visser, 1960, 1962) and, as reviewed by Hall et al. (1967), on poliomyelitis and arthropod-borne viruses, Histoplasma capsulatum, Mycobacterium leprae, etc. M. albicaudatus is easy to handle, and can be maintained on standard laboratory rodent diet. It has clean habits, and may produce over 20 litters in its lifetime (Davis, 1963). This rat is useful for long-term experiments since it lives for up to 6 years, longer than other common laboratory rodents (Hall et al., 1967). MATERIALS AND METHODS M. albicaudatus specimens obtained from the Armed Forces Institute of Pathology in 1965 were bred in our laboratory. Leishmania donovani (strain DH 147) isolated in February 1962 from Received for publication 31 January 1973. * From Research Project MR041.09.01-0103B6HJ, Bureau of Medicine and Surgery, Department of the Navy, Washington, D. C. The opinions and assertions contained herein are the private one of the authors and are not to be construed as official or as reflecting the views of the Department of the Navy or of the naval service at large. m n in Upper Nile Province, Sudan, has been maintained by serial passage in hamsters. Sixty white-tailed rats and 42 hamsters were each inoculated intracardially with L. donovani (200,000 parasites per gram body weight). The observation period was 40 days in the hamster (time of death) and 365 days in the white-tailed rat. Six infected animals of each species were killed 1 to 4 hr postinoculation and on days 8, 16, 24, 32, 40, 80, 160, and 365. Each body, spleen, and liver was weighed and examined for ratio of spleen and liver to body weight and for parasite densities in body organs and presence or absence in blood and skin during the course of infection. Stauber's (1958) standardized counting procedure was used to quantitate the inocula and parasite densities. Blood and skin biopsies were examined by culture using NIH medium (Tobie et al., 1950) and modified liquid medium (Mansour et al., 1973). Cultures were checked weekly for 4 weeks.