How antifungal treatments kill Microsporum canis on cat hair over time

Abstract

BACKGROUND: Topical antifungal therapy is recommended to disinfect hairs of dermatophyte-infected animals. OBJECTIVE: To determine the immediate and residual (24, 48 and 72 h) antifungal activity of commonly used products for focal (n = 11) and whole body application (n = 3). ANIMALS: Hair samples from naturally infected kittens. METHODS AND MATERIALS: Immediate antifungal activity was assessed using isolated infected spores. In a more robust challenge, toothbrushes containing whole infected hairs were repeatedly treated with products until culture-negative. Residual activity was determined by treating 0.04 g of uninfected hair with test products, allowing hairs to dry and then plating hairs onto fungal culture plates inoculated with Microsporum canis. Residual activity was assessed at 24, 48 and 72 h post-treatment. RESULTS: All products showed good efficacy against isolated infected spores. Two products required three treatments to disinfect whole infected hairs (miconazole 0.2% and ketoconazole 0.15%); all other products were efficacious after one treatment. For each product residual activity at 24, 48 and 72 h was similar. For the whole body products, lime sulfur and enilconazole showed residual activity, but as expected none was detected for 2% miconazole nitrate/ 2% chlorhexidine shampoo. For focal therapy products, residual activity was detected for clotrimazole 1%, terbinafine 1%, miconazole at 0.2, 1 or 2% (with or without chlorhexidine), climbazole 0.5% with chlorhexidine gluconate, and ketoconazole 1% with chlorhexidine gluconate. A ketoconazole 0.15% with 0.15% chlorhexidine gluconate showed no residual activity. CONCLUSIONS AND CLINICAL IMPORTANCE: Findings support twice weekly application of enilconazole and lime sulfur, and application of adjuvant focal topical therapy daily or every other day.