Histological and immunohistochemical study of clinically normal skin of Leishmania infantum-infected dogs

Skin lesions are the most usual manifestation of canine leishmaniosis. The aim of this study was to investigate the histological pattern and parasite load in clinically normal skin of Leishmania-infected dogs. Two groups of Leishmania-infected dogs were studied. Group A consisted of 15 symptomless animals which, although seronegative or only mildly seropositive, gave a positive polymerase chain reaction (PCR) for Leishmania in the skin. Group B consisted of 20 clinically affected dogs which were highly seropositive and PCR-positive. Biopsies of normal skin from all dogs were processed for routine histology and Leishmania immunohistochemistry. The study demonstrated microscopical lesions and the presence of parasites in the skin from dogs of group B, but not group A. The results cast doubt on the relevance of infected but symptomless dogs in the epidemiology of canine leishmaniosis. In contrast, however, the clinically normal skin of sick dogs harbours the parasite and probably plays a role in the transmission of leishmaniosis.