Leishmaniose Visceral Canina (LVC): estudo histológico e imuno-histoquímico comparativo da dermatite crônica e parasitismo cutâneo com a inflamação crônica granulomatosa sistêmica (cutânea, hepática e esplênica)

Abstract

The aim of this study was to investigate the associations between chronic dermatitis, cutaneous parasite load, and chronic systemic granulomatous inflammation of the skin, liver, and spleen in Canine Visceral Leishmaniasis (CVL). For this purpose, 46 paraffin-embedded samples of skin fragments from the ear (pinna), liver, and spleen of dogs naturally infected with L. (L.) infantum were used. Histological analyses of slides prepared with fragments of the aforementioned tissues and stained with Hematoxylin-Eosin (H&E) were performed in a qualitative, semi-quantitative, and quantitative manner (morphometric analyses by optical microscopy) to assess histological alterations, such as regressive processes (e.g., degeneration) and inflammatory processes (e.g., chronic inflammation and chronic granulomatous inflammation). For the latter, the number and area of granulomas were analyzed. The cutaneous parasite load was determined by immunohistochemical staining of amastigote forms of Leishmania. Regarding the associations between chronic dermatitis and histological changes in the skin, it was observed that dogs with severe chronic dermatitis had a higher proportion of moderate to intense granulomatous inflammation in the skin, often presenting a greater number and larger average area of granulomas. Additionally, the intensity of chronic dermatitis was concomitant with the cutaneous parasite load. Histological analyses of the liver revealed, among other changes, granulomatous hepatitis, ranging from mild to intense, characterized by the formation of intralobular granulomas. Moderate to intense granulomatous hepatitis was frequently associated with moderate to intense chronic dermatitis. Furthermore, a greater number and larger area of hepatic intralobular granulomas were associated with severe chronic dermatitis. The increased cutaneous parasite load was also associated with moderate to intense granulomatous hepatitis. Finally, histological analyses of the spleen revealed granulomatous splenitis, ranging from mild to severe. Moderate to severe granulomatous splenitis was positively associated with severe chronic dermatitis. In conclusion, it can be inferred that histological and immunohistochemical analyses of skin biopsies (pinna) in veterinary practice can aid in understanding the pathogenesis of CVL, particularly regarding the presence or absence of chronic dermatitis and chronic granulomatous inflammation in internal organs such as the liver and spleen.