Dermatophitosis by trichophyton Spp. causing generalized skin lesions in a bottlenose dolphin (Tursiops truncatus): first report in a free-ranging cetacean

Abstract

A male calf bottlenose dolphin (Tursiops truncatus) stranded alive in Tarifa (Cádiz, Spain). After several attempts of reintroduction, the animal was transported to a rehabilitation centre (Regional Government of Andalusian). It was still dependent on the mother’s milk and its body condition was progressively declining. After being under human care for eleven days, the animal finally died. A complete standardized necropsy was performed and tissue samples were collected and fixed in 10% neutral buffered formalin for histopathological analysis. Grossly, multiple rounds to oval, sometimes rectangular, irregular, slightly raised and discolored skin lesions were diffusely distributed from the head to the caudal peduncle of the specimen. A peripherical and central depression of the skin was a characteristic feature of the lesions. Histologically, a regular hyperplasia was observed characterized by the presence of mitotic figures at the basal layer (stratum germinativum). A slight interstitial edema was present at the midsuperficial layers of the stratum spinosum and a marked hyperkeratosis with abundant death cells was present at the upper layer (stratum externum) of the epidermis intermixed with some tortuous empty or slightly basophilic tracks. The PAS and the Grocott stains revealed the presence of abundant hyphae-like structures within the hyperqueratotic layers. These hyphae positively reacted with an anti-Trichophyton antibody, and it came out negative with a panel of other primary reagents against different fungi. Dermatophytes are fungi that grow on the outermost layers of the skin of animals, including muco-cutaneous membranes, genitalia, external ears, as well as dead skin or hair. Infections caused by dermatophytes, seem to be rare in marine mammals, and therefore also in cetaceans. Up to date a single case of Trichophyton spp. isolated from widespread superficial nodules on the trunk of an Atlantic bottlenose dolphin kept in captivity in Japan has been reported.