introduction and objectives:
Visceral leishmaniosis (Kala-azar) is a fatal sporadic zoonotic disease in many parts of Iran whilst it is endemic in some areas. Dogs constitute the main domestic reservoir for Leishmania infantum in Iran but incidence of the disease in cats in some geographical parts, suggested the feline role in the epidemiology of visceral leishmaniosis in our country. In the present study, molecular and pathological findings, were evaluated in cats experimentally infected by L. infantum.Materials and Methods: Eighteen healthy adult cats were divided in three groups, 6 each. Six cats were intravenously inoculated with 109 and the other group received 108 stationary phase promastigotes of L. infantum and the remaining six cats were used as the uninfected control group. During a 24-week period, after clinical examination, blood was collected from jugular vein and PCR was performed. Bone marrow aspirates were obtained at 2 months intervals and at the end of the study, the cats were euthanized and histopathological examination was carried out. Results: Two weeks after inoculation, nested PCR was able to detect L. infantum in the blood samples of the inoculated cats in two groups and remained positive until 24 weeks. PCR of bone marrow became positive two months later but amastigote phase of parasite was observed in bone marrow by cytological examination three months following inoculation. At the end of the study, three of liver and lymph nodes samples were positive by PCR test. In contrast, in histopathological examination, amastigotes were not observed in the liver, kidney, spleen, lungs, intestine, lymph nodes, and brain samples at the end of the study. Splenomegaly, sinus histiocytosis of spleen, lymphoid hyperplasia and depletion, liver congestion, sinusoidal distension and fatty liver change were detected in some cats.Conclusion: Based on the results of molecular findings, L. infantun infiltrated in the bone marrow 2 months after inoculation; however, it was not observed in reticuloendothelial organs. These findings showed probably the natural resistance and slow progression of kala-azar and the considerable sensitivity of PCR assays in cats. Cats may be implicated as a secondary reservoir for L. infantum transmission due to long lasting parasitemia. Further studies are essential to describe the immune system function and pathogenesis of L. infantum in cats.