Leishmaniasis in the Sudan Republic. 29. Comparison and epidemiological implications of experimental canine infections with Sudanese, Mediterranean, and Kenyan strains of Leishmania donovani.

Three strains of Leishmania donovani from different geographic areas [Sudan, Mediterranean (Sicily), and Kenya] were studied comparatively in puppies and adult dogs under controlled laboratory conditions. Hematological, serological, and endocrinological investigations were included. However, only the course of infection is discussed here. The growth curve of the parasites in the liver was studied, as well as the pattern of infection in different organs at different periods. The pattern of both liver and spleen infections caused by the Mediterranean strain proved to be different from and more variable than that caused by the Sudan and Kenya strains, which developed similarly except for an earlier decline of parasite numbers followed by spontaneous cure in the Kenya strain. Assuming the results from these strains to be fully representative of their respective areas, it is suggested that the dog may be excluded as a probable natural reservoir of L. donovani in Kenya and that its role as a vertebrate reservoir in the Sudan is doubtful. The results confirm that the dog is an efficient reservoir of the pathogen in the Mediterranean area. In areas where kala azar is endemic, dogs are frequently abundant and closely associated with man. They play an important role as reservoir hosts of Leishmania donovani in China, several foci in the USSR, Brazil, and many localities in the Mediterranean basin. Canine leishmaniasis has been reported but is inadequately documented in several areas of Africa. No canine infections have been reported from Kenya (Henderson, 1937; Heisch, 1954, 1963) or the Sudan (Archibald and Mansour, 1937; Kirk, 1956; Hoogstraal et al., 1963; Hoogstraal and Heyneman, 1969). The paradoxical discrepancies between recorded distributions of human and canine infections require experimental investigation to evaluate the interrelationships between different geoReceived for publication 8 January 1970. * Parasitology Department, U. S. Naval Medical Research Unit Number Three, Cairo, Egypt, UAR. This work was undertaken at the Bureau of Biological Research, Rutgers-The State University, under the auspices of Office of Naval Research Postgraduate Research Grants NONR00038-65 and NONR-0137-66. From Research Project MF12.524.009-3001B, Bureau of Medicine and Surgery, Department of the Navy, Washington, D. C. The opinions and assertions contained herein are the private ones 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. t Bureau of Biological Research, Rutgers-The State University, New Brunswick, New Jersey 08903. graphical strains of the organism and the dog, and to assess the role of the dog in kala azar epidemiology in different areas. This report, abstracted from a more extensive study to be published elsewhere, is intended chiefly to elucidate factors influencing the epidemiological role of the dog in Central Sudan and to contribute to the results of an extensive field and laboratory study of kala azar in that country (Hoogstraal and Heyneman, 1969). Although several studies have been devoted to L. donovani infection in the dog, none has used standardized procedures for inoculation, sampling, and evaluation. Stauber (1955) established a quantitative procedure that makes it possible to follow the course of infection with reasonable accuracy. Stauber et al. (1966) emphasized the importance of standardized quantitative procedures and Stauber (1966) applied these criteria to a comparison of interstrain variation in L. donovani. These studies established that intravascular inoculation of relatively large numbers of organisms is required to produce infections of relatively low variability for accurate estimates in vivo of L. donovani strain differences. These techniques have been employed in the present study. MATERIALS AND METHODS Three groups of 4 adult dogs (average age 5 years) and 5 groups of puppies, at least 4 in each group from the same litter (average age 4 weeks), were infected with the following strains of Leishmania donovani.