Monitoring fungal burden and viability of Sporothrix spp. in skin lesions of cats for predicting antifungal treatment response

Skin lesions in feline sporotrichosis usually present a high fungal burden, making cats an important source of infection. This study evaluated the fungal burden and isolation in skin lesions of feline sporotrichosis during treatment with itraconazole (ITZ), combined with or without potassium iodide (KI). Treatment-naïve cats with culture-confirmed sporotrichosis and presenting skin ulcers were treated for up to 40 weeks with oral ITZ alone (n = 74) or combined with KI (n = 56). These cats were submitted to monthly sampling of the same lesion for mycological culture and cytopathology until healing of lesion or up to twelve weeks. The fungal burden was expressed as the mean yeast cell count in three microscopic fields from imprint smears. The fungal burden before treatment was significantly higher in cats in which the lesion persisted and in cases of treatment failure when using ITZ alone. After twelve weeks, the median fungal burden decreased to zero in both treatment protocols, suggesting a potential decrease in the risk of transmission of Sporothrix spp. from cats. These findings encourage the early treatment of feline sporotrichosis as a control measure. Moreover, the fungal burden in feline sporotrichosis lesions can be a prognostic indicator and a parameter for choosing appropriate therapeutic regimen