An unknown Trypanosoma species was isolated from an axenic culture of intact skin from a domestic dog captured in Rio de Janeiro, Brazil, which was co-infected with Leishmania (Viannia) braziliensis. Giemsa-stained smears of cultures grown in different media revealed the presence of epimastigotes, trypomastigotes, spheromastigotes, transitional stages, and dividing forms (epimastigotes or spheromastigotes). The highest frequency of trypomastigotes was observed in RPMI (15.2%) and DMEM (9.2%) media containing 5% FCS, with a mean length of these forms of 43.0 and 36.0 mum, respectively. Molecular analysis by sequential application of PCR assays indicated that this trypanosome differs from Trypanosoma cruzi and T. rangeli when specific primers were applied. On the other hand, a PCR strategy targeted to the D7 domain of 24salpha rDNA, using primers D75/D76, amplified products of about 250 bp in that isolate (stock A-27), different from the amplification products obtained with T. cruzi and T. rangeli. This organism differs from T. cruzi mainly by the size of its trypomastigote forms and kinetoplasts and the absence of infectivity for macrophages and triatomine bugs. It is also morphologically distinct from salivarian trypanosomes reported in Brazil. Isoenzyme analysis at 8 loci demonstrated a very peculiar banding pattern clearly distinct from those of T. rangeli and T. cruzi. We conclude that this isolate is a new Trypanosoma species. The name T. caninum is suggested.

Trypanosoma caninum is a parasite of the Trypanosoma genus recently described in the natural infection of dogs in the municipality of Rio de Janeiro, Brazil. Suspecting the existence of a natural cycle and the circulation of this new species, the objective of this study was the taxonomic identification of samples of Trypanosoma spp. isolated from dogs in different Brazilian regions. Parasites were solely obtained from skin fragments culture and characterized by nested-PCR targeting the partial sequence of 18S rRNA gene and PCR products were sequenced. Thirty-three samples, obtained in São Paulo, Minas Gerais, Goiás, Mato Grosso and Rio de Janeiro states were analyzed. PCR and sequencing showed that the isolates were genetically identical or closely similar and confirmed T. caninum identity. This report broadens the geographical distribution of T. caninum in Brazil and discusses the impact of the presence of this parasite in areas of canine leishmaniasis occurrence.

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Trypanosoma caninum constitutes the most recent trypanosomatid species infecting dogs in Brazil. Due to the limited data available about this parasite, this study aims to disclose clinical and laboratory findings from 14 dogs naturally infected. The dogs were diagnosed during a cross-sectional survey in Cuiabá (Mato Grosso, Brazil) and followed up at an interval of 3, 6, and 12 mo in order to evaluate the clinical evolution and to investigate the parasite, the DNA, or both in different biological samples (intact skin, cutaneous scar, blood, bone marrow, and lymph node aspirate) by parasitological (culture and smear exam) and molecular (DNA-based tests) methods. Specific anti-T. caninum and anti-Leishmania antibody production was also evaluated. Ten of 14 dogs infected by T. caninum showed a good general state at the time of diagnosis, and this status did not vary during the follow-up. Anti-T. caninum and anti-Leishmania IgG antibodies were detected by IFAT in 10 and 2 animals, respectively. Concomitant infection by Leishmania chagasi was confirmed in 2 dogs, indicating an overlap of endemic areas in Cuiabá. Trypanosoma caninum (parasite or DNA) was found only in the intact skin in all animals examined. Our results suggest that T. caninum infection can be manifested as an asymptomatic case with low humoral immune response.

Molecular phylogenetic studies have revealed the growing diversity of bat trypanosomes. Here, 14 isolates from blood samples of the vampire bat Desmodus rotundus (Phyllostomidae) from Rio de Janeiro, Southeast Brazil, were cultivated, and morphologically and molecularly characterized. All isolates represent a novel species named Trypanosoma madeirae n. sp. positioned in the Neobat lineage of the clade T. cruzi. The Neobat lineage also comprises closely related trypanosomes of clades Neotropic 1, 2 and 3 from diverse phyllostomid species. Trypanosomes of Neotropic 1, found in Trachops cirrhosus and Artibeus jamaicensis (phyllostomids), likely represent a different species or genotype closely related to T. madeirae. Consistent with its phylogenetic positioning, T. madeirae differs from Trypanosoma cruzi in morphology of both epimastigote and trypomastigote culture forms and does not infect Triatoma infestans. Similar to its closest relatives of Neobat lineage, T. madeirae was unable to develop within mammalian cells. To date, PCR-surveys on archived blood/liver samples unveiled T. madeirae exclusively in D. rotundus from Southern to Northern Brazil. The description of a new species of bat trypanosome associated with vampire bats increases the repertoire of trypanosomes infecting D. rotundus, currently comprised of Trypanosoma cruzi, T. cruzi marinkellei, Trypanosoma dionisii, Trypanosoma rangeli, Trypanosoma pessoai, and Trypanosoma madeirae.