Determination of virulence and pathogenesis of a canine strain of Leishmania leishmania infantum in hamsters and dogs.

Visceral leishmaniasis was experimentally induced in hamsters by the intracardiac inoculation of 10(7) amastigotes of Leishmania leishmania infantum of canine origin. At postinoculation (PI) days 7, 21, 42, and 63, hamsters were euthanatized. Body weights and total parasite numbers of the liver and spleen were determined. Gross and histologic evaluations of tissues were done. Dogs also were inoculated IV with 10(8) amastigotes/kg of body weight. Samples were obtained from dogs prior to infection and at biweekly PI intervals for CBC and serum chemical analysis, for lymphocyte blastogenic assay by use of blood leukocytes, and for ELISA to determine antileishmanial antibody titers. At PI week 12, dogs were necropsied; organ weights, tissue imprints of the liver and spleen, and histologic interpretations of tissues were obtained. Hamsters developed high parasite numbers within 7 days after inoculation, at which time the total parasite numbers in the liver (3.51 x 10(7) amastigotes) was observed to be approximately 11 times that in the spleen (2.93 x 10(6)). The liver had the highest parasite numbers throughout the infection period. Some infected hamsters became either cachectic and emaciated or ascitic. Two of the 10 infected hamsters died at PI days 54 and 58. Moderate to severe hepatosplenomegaly with granulomatous inflammatory reactions characterized by the presence of varied numbers of parasitized macrophages, giant cells, and hepatic Schaumann bodies were observed in infected hamsters. Infected dogs developed significantly altered hematologic values consisting of mild anemia and moderate leukopenia at PI weeks 8 to 12. Hyperproteinemia characterized by hyperglobulinemia (4.5 g/dl) was noticed at PI week 4.(ABSTRACT TRUNCATED AT 250 WORDS)