Malassezia dermatitis in dogs in Brazil: diagnosis, evaluation of clinical signs and molecular identification.

Skin carriage and quantification of Malassezia yeasts were evaluated in 180 healthy dogs (group 1) and 117 dogs with clinical signs (pruritus, erythema, lichenification/seborrhoea, excoriations and alopecia) that could be related to Malassezia dermatitis (group 2) in Brazil. The lesions in the group 2 dogs were evaluated using CADESI-03 scores. Samples were collected from five different anatomical areas. Direct examination was performed using the tape strip technique, and results were expressed as the mean number of yeasts per ×1000 microscopic field per dog. For mycological culture, a single piece of sterilized carpet was applied to the same areas sampled for cytology, and transferred onto Dixon's modified medium. Yeast populations were expressed as mean colony forming units (CFU)/plate. Malassezia isolates were characterized by polymerase chain reaction-restriction endonuclease analysis of the large subunit (LSU) of ribosomal RNA gene. The probability of culturing Malassezia from dogs with skin lesions was significantly higher (P<0.001) than from healthy dogs. There was a linear trend between CADESI-03 score and mean CFU/plate. Group 2 dogs with positive cultures had higher CADESI-03 scores than those with negative cultures (P<0.05). Almost all isolates were identified as Malassezia pachydermatis. Only one isolate (group 2) was identified as Malassezia furfur. These data suggest that dogs with skin disorders harbouring Malassezia yeasts in quantities higher than 120 mean CFU/plate should be considered as having Malassezia dermatitis. The presence of Malassezia appears to exacerbate clinical lesions in dogs.