Clinical, epidemiological, histomorphological and histochemical characteristics of the feline sporotrichosis

Abstract

Sporotrichosis is a mycotic infection caused by the Sporothrix complex species, affecting mostly cats, horses, and dogs. The main objectives of this retrospective study were to characterize the histomorphological and histochemical aspects of sporotrichosis in 10 cats, and also to evaluate epidemiological and clinical aspects, and gross findings obtained from the biopsy and necropsy protocols of these ten cases, obtained from the archives of the Laboratório de Patologia Veterinária of the Universidade Federal de Santa Maria. The disease affected mostly male mongrel cats, and was mostly observed in the cutaneous disseminated form. Gross lesions were characterized by cutaneous nodules (ulcerated or not) and by ulcerated masses or plaques. By histopathology, there were a relationship between the fungal load and two patterns of inflammatory response. The first pattern was characterized by high fungal load, and most yeasts were inside of numerous macrophages with abundant, many times vacuolated cytoplasm. The amount of neutrophils ranged from mild to moderate in this pattern. The second pattern was characterized by numerous epiteliod cells and many neutrophils. The fungal load was low and most yeasts were observed in the extracellular space. The yeasts were round, oval or cigar-shaped. Several histochemical techniques, such as Grocott's silver stain, periodic Schiff acid, and Alcian blue were utilized and they made it easier to visualize, to characterize the morphology, and to quantify the organisms. The Giemsa stain allowed visualizing the agent, but it not allowed to sharply highlight them from other intralesional components. Organisms were negative for melanin granules through the Fontana-Masson stain in all cases. The histomorphological and histochemical study allowed demonstrating determinant fungal characteristics to the establishment of the diagnosis by means of this diagnostic tool.

Index Terms:
Feline sporotrichosis; Sporothrix spp. Complex; diseases of cats; subcutaneous mycosis