Clinical features, fungal load, coinfections, histological skin changes, and itraconazole treatment response of cats with sporotrichosis caused by Sporothrix brasiliensis

Abstract

Zoonotic sporotrichosis caused by the fungus Sporothrix brasiliensis is usually severe in cats. This study investigated the associations between clinical features, fungal load, coinfections, histological skin changes, and response to itraconazole in cats with sporotrichosis caused by S. brasiliensis. Fifty-two cats with skin lesions and a definitive diagnosis of sporotrichosis were treated with itraconazole for a maximum period of 36 weeks. The animals were submitted to clinical examination and two subsequent collections of samples from the same skin lesion for fungal diagnosis and histopathology, as well as serology for feline immunodeficiency (FIV) and leukaemia (FeLV) viruses. Thirty-seven (71%) cats were clinically cured. Nasal mucosa lesions and respiratory signs were associated with treatment failure. Cats coinfected with FIV/FeLV (n = 12) had a lower neutrophil count in the lesion. A high fungal load in skin lesions was linked to young age and treatment failure, as well as to a longer time of wound healing, poorly formed granulomas and fewer neutrophils, macrophages and lymphocytes in these lesions. These results indicate that itraconazole is effective, but nasal mucosal involvement, respiratory signs and high fungal loads in skin lesions are predictors of treatment failure that will assist in the development of better treatment protocols for cats.

Monitoring Fungal Burden and Viability of Sporothrix spp. in Skin Lesions of Cats for Predicting Antifungal Treatment Response

“…Similarly, in humans and dogs, the occurrence of lesions with high fungal burdens is usually associated with immunosuppressive conditions, such as malnutrition, use of steroid, and the presence of underlying diseases, especially those that induce immunosuppression, such as AIDS [ 27 , 28 , 29 , 30 , 31 , 32 ]. In cats, Miranda et al [ 7 , 33 ] and Souza et al [ 13 ] have already observed that different immune response patterns determine the intensity of the fungal burden in skin lesions of feline sporotrichosis and that large numbers of fungal cells generally occur in lesions with a poorly organized inflammation. In addition, a negative correlation has been observed between fungal burden and the number of lymphocytes, neutrophils, and macrophages [ 13 ].…”

“…In cats, Miranda et al [ 7 , 33 ] and Souza et al [ 13 ] have already observed that different immune response patterns determine the intensity of the fungal burden in skin lesions of feline sporotrichosis and that large numbers of fungal cells generally occur in lesions with a poorly organized inflammation. In addition, a negative correlation has been observed between fungal burden and the number of lymphocytes, neutrophils, and macrophages [ 13 ].…”

“…Additionally, persistent positivity in both CPE and fungal culture until the third month of treatment was related to negative outcomes in cats under ITZ monotherapy. Souza et al [ 13 ] also observed that high fungal burdens in skin lesions before treatment with ITZ were linked to treatment failure as well as a longer time of wound healing in cats. Thus, the follow-up of fungal burden and fungal viability in skin lesions may identify cats that are refractory to ITZ and for which therapeutic alternatives should be considered.…”

“…Previous studies have shown that some therapeutic protocols may reduce the fungal burden in sporotrichosis, even when the infection is caused by S. brasiliensis [ 10 , 11 , 12 , 13 ]. Recently, Souza et al [ 13 ] reported a significant reduction in the fungal burden within 5 to 11 weeks after start of antifungal treatment in cats with sporotrichosis caused by S. brasiliensis . However, these authors had evaluated a small number of cats ( n = 22) treated with itraconazole (ITZ) at only two time points and had used histopathology of biopsied skin samples, which is a more invasive method and does not confirm the viability of the fungus.…”

Feline sporotrichosis in Asia

“…The preponderance of lesions to aggregate at these cooler sites, especially at the ear tips, may be due to the lack of thermotolerability of S. s. sensu stricto and S. globosa isolates compared with S. brasiliensis which has the propensity to disseminate in a susceptible feline host [24][25][26] (Fig. 5).…”