Low susceptibility of domestic cats to experimental Leishmania infantum infection

Background and objectives: The dogs are considered the main reservoir of visceral leishmaniasis (VL), but lately the disease incidence has been reported in cats also. In this study, the susceptibility of domestic cats to experimental Leishmania infantum infection was assessed by different diagnostic methods. Methods: A total of 12 healthy adult male cats were captured by double door live trap cages containing baits. Of them eight cats were intraperitoneally inoculated with 10(7) L. infantum promastigotes (stationary phase), and four cats were used as controls. Whole blood and scrum samples were collected at weekly intervals for 16 wk after inoculation for testing by polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) methods. Aspirates of prescapular lymph nodes and bone marrow were obtained at monthly intervals. Clinical examination was performed twice weekly and histopathological evaluation was done on necropsy samples at the termination of the study. Results: One week after inoculation, blood nested PCR was able to detect the L. infantum infection and it remained positive until 16 wk. ELISA test remained negative during the study. Amastigote phase of parasite was not observed in bone marrow aspiration and necropsy samples. Interpretation and conclusion: The feline model described in this work would be useful in further understanding of L. infantum immunopathogenensis in cats. The results of this preliminary study suggest that cats might be resistant to VI, as the inoculation dose which induces pathognomonic clinical features in dogs, just creates asymptomatic parasitaemia in cats. Though, due to long-lasting parasitaemia, cats may act as appropriate reservoir for transmission of VL to human population. Further studies are needed to describe the possible role of cats in the epidemiology of VL in endemic areas.