Leishmania infantum Specific Humoral and Cellular Immune Responses in Cats and Dogs: A Comparative Cross-Sectional Study

SIMPLE SUMMARY: The role of the cat as a reservoir of Leishmania infantum and the characteristics of the immune response to this infection remains limited, contrary to the dog. This study aimed to compare the rate of L. infantum infection and parasite-specific humoral and cell-mediated immune responses in cats and dogs living in an area endemic to canine leishmaniosis (Córdoba, Spain). About one-third of the dogs and cats studied were positive for at least one molecular or serological diagnostic test. The immunopathogenesis of L. infantum infection in cats showed similarities when compared to dogs, although the parasite-specific immune response level in dogs was generally higher than in cats. This study shows that stray cats are exposed to L. infantum infection similarly to dogs in endemic areas, are able to mount a specific anti-Leishmania humoral and cell-mediated immune response as dogs, and can contribute to the endemicity of infection. ABSTRACT: Dogs are the main reservoir of Leishmania infantum and display different immunological patterns correlating with the progression of infection to disease. Data about feline L. infantum adaptive immune response are scant. This study aimed to compare the prevalence and immune response in cats and dogs from the same endemic area of canine leishmaniosis. Stray cats (109) and rescued dogs (59) from Córdoba (Spain) were enrolled. Data about their exposure to L. infantum were analyzed by detection of parasite DNA, measurements of Leishmania-specific interferon-γ (whole blood assay in 57 cats and 29 dogs), and antibodies (enzyme-linked immunosorbent assay and immunofluorescence antibody test). An overall L. infantum prevalence of 30.5% in dogs and 30% in cats were found according to serology and PCR tests. Prevalence was 44.8% in dogs and 35.1% in cats tested also for interferon-γ production. Dogs showed higher anti-L. infantum antibody levels compared to cats. More than one-third of cats had contact with or were infected by L. infantum and they may contribute to the endemicity of leishmaniosis in the investigated region. The immunopathogenesis of feline L. infantum infection has similarities with dogs but cats show a lower level of adaptive immune response compared to dogs.