Histopathological and parasitological analysis of skin tissues biopsies from two distinct anatomical areas of the ears of dogs naturally infected with Leishmania (Leishmania) chagasi.

Abstract

Canine visceral leishmaniasis is an endemic disease in Latin America caused by Leishmania (Leishmania) chagasi and transmitted to man and animals by infected blood-sucking sandflies) of the genus Lutzomyia. Dogs are considered to be the primary domestic reservoir of disease because they present an intense cutaneous parasitism. The aim of this study was to evaluate the intensity of the inflammatory process and to compare it to the parasite load of tissue from two different sites of the ear skin of dogs naturally infected with Leishmania chagasi. We think that exist a specific anatomical region that exhibits a relatively higher rate of parasitism. For diagnostic analysis, serological tests were carried out using the indirect fluorescence antibody test (IFAT) and the enzyme-linked immunosorbent assay (ELISA). Twelve animals naturally infected with Leishmania chagasi were euthanatized with a lethal dose of Sodium Thiopental™ and T61™. During the necropsy, fragments of the extremity and middle anatomical regions of the ear were collected. All tissues were fixed in a 10% formalin solution and then paraffin-embedded for histopathological (HE) and immunohistochemical analysis. The streptoavidin-peroxidase immunohistochemistry method was used to detect tissue amastigotes using optical microscopy. Our results indicated a chronic inflammatory reaction, ranging from discrete to an intense magnitude. The inflammatory process was more frequently observed in the extremity of the ear than in the middle portion of the ear (p<0.05). The presence of parasites in the ear extremity was higher than in other evaluated regions. A positive correlation between the tissue inflammation, parasitism, and serological data was confirmed at both ear positions (p<0.05). Skin biopsies are an important tool for CVL diagnosis and the ear extremity represents an appropriated area to perform the assays.