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Abstract Leishmania infantum is a trypanosomatid that causes parasitic dermatopathy in dogs. Trypanosoma caninum is another trypanosomatid, which infects the skin of dogs, although cutaneous abnormalities are absent. This study aimed to investigate the occurrence of T. caninum infection and its associated cutaneous and histological changes and compare it with the occurrence of L. infantum infection in dogs. The study included 150 dogs, of which T. caninum infection was identified in 3 (2%) and L. infantum infection in 15 (10%) of them, with no association (p>0.05) of these infections with the breed, gender, age, or cutaneous abnormalities. The cutaneous abnormalities were based on 1 (4.8%) and 12 (57.1%) dogs infected by T. caninum and L. infantum, respectively. The dermatohistopathological abnormalities in the dogs infected with T. caninum included mild perivascular lymphohistioplasmacytic infiltrates in the clinically asymptomatic ones, while in those with dermatological abnormalities, acanthosis, epidermal orthokeratotic hyperkeratosis, melanomacrophages, and co-infection with Microsporum sp. and Trichophyton sp. were observed. InL. infantum infected, the histopathological findings included chronic granulomatous inflammatory infiltrates and structures compatible with amastigotes. Despite the low frequency of T. caninum infection, our findings suggest that this trypanosomatid, unlike L. infantum, does not cause any macroscopic skin abnormalities.

Visceral leishmaniasis is an infectious disease of chronic, emerging and zoonotic nature that presents various degrees of severity. In Brazil, this illness is caused by Leishmania infantum (Leishmania chagasi), which is transmitted by the bite of the sand fly Lutzomyia longipalpis, and dogs are its main reservoir. Given the increasing spread of this disease across Brazil, the aim of this study was to report on six cases of canine visceral leishmaniasis, diagnosed in June 2013, in the city of Pedregulho, State of São Paulo, considered to be a non-endemic area and free of phlebotomine sand flies. The diagnosis was based on clinical signs of the patients and additional tests (serological and parasitological). It was concluded that the diagnosis of leishmaniasis is complex because the clinical signs are similar to other systemic diseases, thus justifying the importance of parasitological test of bone marrow, considered "gold standard", in the confirmation of the disease. In addition, the area was not, until now, considered risk place, despite notification.