Canine leishmaniosis: An atypical presentation on the tongue.

Canine leishmaniosis (CanL) is a vector-borne disease caused mainly by the protozoan parasite Leishmania infantum, transmitted to its vertebrate hosts by phlebotomine sand fly insects. Clinical disease and a higher proportion of subclinical infections are endemic in several countries, with a high prevalence in the Mediterranean basin. The clinical signs and lesions of CanL are diverse, but oral manifestations have only been reported occasionally. Here we present an atypical case of Leishmania infection on the tongue of a domestic dog. A 12-year-old neutered male mongrel dog was presented to the University of Trás-os-Montes e Alto Douro Veterinary Teaching Hospital with intermittent lameness of the left pelvic limb and a cutaneous lesion on the nose. Physical examination revealed generalized lymphadenopathy, as well as the presence of an oral mass on the ventral surface of the tongue. Histological examination of this oral lesion showed extensive mucosal ulcerations with granulomatous inflammation in the submucosa. Large macrophages were found, containing intracytoplasmic structures compatible with Leishmania spp. amastigotes. Immunohistochemistry identified several leishmanial amastigote forms both inside macrophages and in the surrounding tissue. In the present case, parasites were unexpectedly identified in the histopathological examination of a tongue mass. Histopathology complemented by immunohistochemistry were fundamental tools for detecting Leishmania parasites and making a definitive diagnosis of CanL in this case. It is also important to conduct a systematic and thorough physical examination, including oral cavity and its floor, for any mass lesions that may be present in dogs with leishmaniosis.