Detection and molecular characterization of Trypanosoma theileri in cattle from the municipality of Vassouras, Rio de Janeiro, Brazil.

This study aimed to detect, using parasitological and molecular methods, and to genetically characterize Trypanosoma spp. in cattle from the municipality of Vassouras, Rio de Janeiro, Brazil. A total of 226 blood samples were collected from dairy cattle across eight farms, and DNA was extracted for PCR amplification of the 18S rRNA gene of Trypanosoma spp. In parasitological examinations, including blood smears and the Woo's technique, no trypomastigote forms of Trypanosoma spp. were observed. Molecular detection via 18S rRNA identified the parasite in 0.88% (2/226) of the samples. The resulting amplicons were sequenced, aligned, and compared with GenBank sequences for phylogenetic analysis. The analyses confirmed 100% identity with T. theileri, prompting further molecular characterization using the 24Sα rRNA (257 pb) and CatL (295 pb) genes. Phylogenetic analysis of T. theileri indicated circulation of the TthI lineage, encompassing genotype IB, in the municipality of Vassouras, Rio de Janeiro. These findings expand knowledge on the geographic distribution of T. theileri in Brazil and underscore the importance of monitoring cattle herds, considering the economic and health significance of trypanosomatids.