Lufenuron and terbinafine for treatment of Microsporum canis infections in a feline model
Authors: DeBoer D. J. , Moriello K. A. , Volk L. M. , Schenker R. , Steffan J. 
Published: August 2004

Empirical evidence suggests that lufenuron has antifungal properties that may be useful for treatment of dermatophytosis in animals. Field reports have generally implied that lufenuron seems efficacious under some conditions, but ineffective in others. Variables such as environmental conditions, genetics, natural immunity, fungal strain variation, prior treatment, and others may explain the diversity in these reports. Two previous studies concluded that lufenuron was not effective in prevention of dermatophyte infection by direct topical application of fungal spores or by exposure to an infected cat. In addition, lufenuron as used in previous studies did not result in faster resolution of infections, once established. However, lufenuron treatment appeared to induce a delay in initial establishment of the infections. This may have reflected an inhibitory effect on the fungus that was experimentally measurable, but not sufficient to prevent development of infection. This mild inhibition by lufenuron may be valuable as an adjuvant effect in combination with other antifungal therapy. The objectives of the current study were to evaluate lufenuron (1) as a primary treatment (vs. preventative) for already established experimental M. canis infections in cats, and (2) as an adjuvant treatment for such infections, in combination with the antifungal drug terbinafine. Juvenile cats were inoculated topically with M. canis spores to create experimental localized infections. Groups of five or six infected cats were treated with either: (1) lufenuron suspension (Program®), 133 mg orally every 2 weeks; (2) terbinafine, 15–30 mg/kg orally once daily; (3) lufenuron plus terbinafine, both given at the above dosages; or (4) itraconazole, 8 mg/kg orally once daily. A fifth group was left as untreated controls. Cats were scored weekly for clinical signs of dermatophytosis and fungal‐cultured once weekly. Treatment continued for up to 14 weeks, or until the cat was deemed cured by clinical and mycologic evidence. Cats in the following treatment groups had the quickest cure of their infections: itraconazole (7.8 ± 1.3 weeks to cure), terbinafine alone (8.6 ± 1.8 weeks), and lufenuron‐terbinafine (8.7 ± 1.2 weeks). Using the Mann–Whitney test, these values were significantly (P ≤ 0.05) less than untreated control cats (11.3 ± 2.2 weeks). Mean time‐to‐cure in cats treated with lufenuron alone was 9.3 ± 1.6 weeks – a lower mean, but not significantly less than untreated control cats. Clinical sign scores during the course of active infection were most consistently significantly lower in itraconazole‐treated cats. Terbinafine and terbinafine‐lufenuron treatment reduced clinical scores as well, but generally not significantly. Thus, both itraconazole and terbinafine performed equivalently with regard to reduction in fungal culture scores and in time‐to‐cure, yet differently with regard to reduction in clinical signs during infection. This may reflect a suboptimal dose of terbinafine, or an anti‐inflammatory effect of itraconazole. We conclude that the results of this study showed no evidence for a synergistic effect of lufenuron when used along with terbinafine.

Funding: Novartis Animal Health.