Relationship between Canine Visceral Leishmaniosis and the Leishmania (Leishmania) chagasi Burden in Dermal Inflammatory Foci

The skin is the first point of contact with organisms of the genus Leishmania from sand fly vectors, and apparently normal skin of sick dogs harbours amastigote forms of Leishmania chagasi. In relation to canine visceral leishmaniosis ( CVL), the ear skin was examined in 10 uninfecte d dog s ( UD s ) and in 31 dog s dog s naturally infected with L. chagasi . The infected animals consisted of 10 symptomless dogs ( SLDs ), 12 mildly affected dog s ( M A D s ) and nine affected dog s ( A D s ). A higher parasite burden was demonstrated in A D s than in SLD s by anti-Leishmania immunohistochemistry (P o0.01), and by Leishman Donivan Unit ( LDU ) indices ( P ¼ 0.0024) obtained from Giemsa- stained impression smears. Sect ions stained with haematoxylin and eosin demonstrated a higher intensity of inflammatory changes in ADs than in SLD s ( P o0.05), and in t he latter group low cytometry demonstrated a correlation (P ¼ 0. 0 5/ r ¼ 0.7454) between the percentage of CD14 + monocytes in peripheral blood and chronic der mal inflammation. Extracellular matrix assessment for reticular fibres by staining of sect ions with Masson trichrome and Gomori ammoniacal silver demonstrated a decrease in collagen typeI and an increase in collagen type III as the clinical signs increase d. The data on correlation between cellular phenotypes and histological changes seemed to reflect cellular activation and migration from peripheral blood to the skin, mediated by antigenic stimulation. The results suggested that chronic dermal inflammation and cutaneous parasitism were directly related to t he sever it y of clinical disease.