Infections identical with Leishmania donovani on the basis of appearance in culture and pathogenesis in hamsters were recovered from 2 rodents, Rattus rattus and Acomys spp., trapped in Malakal town, Upper Nile Province. It appears that a rodent-sandfly-rodent cycle of leishmaniasis occurs in this town, but that in the absence of man-biting sandflies, humans do not become infected in this urban center.
In Paloich District, approximately 100 miles north of Malakal, 2 definite and 2 equivocal Leishmania infections were found among 117 Nile Grass Rats (Arvicanthis niloticus luctuosus), out of a total of 242 wild rodents from this district. Three were isolated by hamster inoculation and one (equivocal) by direct culture of spleen tissue. These animals were trapped in an area where human kala-azar is endemic and in the same spots in Acacia forests where Phlebotomus orientalis was found to bite man and to be commonly infected with Leishmania. One person assisting in trapping sandflies and rodents in Paloich District subsequently developed a severe case of kala-azar. In Paloich District, leishmaniasis may be a true zoonosis, with A. niloticus luctuosus as a vertebrate reservoir and P. orientalis as the chief vector to humans.