Daylight photodynamic therapy using methylene blue to treat sheep with dermatophytosis caused by Arthroderma vanbreuseghemii

Abstract

Arthroderma vanbreuseghemii has been identified molecularly as the causative agent of dermatophytosis in a flock of sheep. It is necessary to explore new treatment alternatives because antifungals are not approved for use on small ruminant animals in the European Union. Antimicrobial photodynamic therapy (aPDT) has been shown to be effective for the treatment of dermatophytosis in humans. It is based on the application of a photosensitizer such as methylene blue (MB) that is activated by visible light to generate reactive oxygen species that are cytotoxic to cells. The use of daylight to perform aPDT (aDL-PDT) avoids the requirement of specific equipment because it uses sunlight to activate the photosensitizer. The aim of our study is to determine the efficacy of aDL-PDT using a 1% MB solution to treat dermatophytosis caused by A. vanbreuseghemii in ewes. Two different topical protocols (1% MB solution spray applications once or twice a week) were assayed in two groups of five infected animals. Twenty-five infected sheep were untreated. All the sheep were exposed to sunlight every day for an approximate duration of 10h for a total of four weeks. At the end of the study, all the animals treated with aDL-PDT showed the same clinical response to both protocols. In contrast, the animals exposed only to sunlight required an additional two to four weeks before their infections resolved.Conclusion: aDL-PDT with 1% MB solution demonstrates efficacy, safety and efficiency in the treatment of dermatophytosis in sheep.