Fungal Dermatitis Caused by Aspergillus sydowii in a Thoroughbred Horse

A 5-year-old male Thoroughbred horse was referred with alopecia, along with severe incrustation, scaling, and pruritus on the left flank and back, which had been in contact with a saddle for 1 year. Treatment with topical antibiotics by the owner was not effective. A fungal culture using the hair roots and exudates under the scabs showed blue-green colonies surrounded by a white band. Microscopic examination and molecular analyses of the internal transcribed spacer region, partial β-tubulin, and calmodulin genes confirmed this fungus as Aspergillus sydowii. Topical treatment with econazole ointment for 2 months was effective. This is the first report of a natural A sydowii infection in a horse.