Babesia gibsoni in Brazil: First multilocus molecular characterization in a domestic dog with clinical, hematological and morphological data.

Canine babesiosis is a disease caused by protozoa of the genus Babesia, an important hemoparasite in veterinary clinical practice. In Brazil, Babesia vogeli predominates; however, Babesia gibsoni, common in Asia and the United States, has emerged globally with distinct diagnostic, therapeutic, prophylactic, and prognostic features. In the present study, we report the first multilocus molecular characterization of B. gibsoni in Brazil with supported clinical, laboratory and morphological data. A Dachshund dog from the Federal District presented with nonspecific clinical signs, including fever, dehydration, and persistent anemia. Babesia infection was confirmed by PCR and further characterized using four molecular markers (cytb, cox3, hsp70, and 18S rRNA). Phylogenetic and sequence identity analyses confirmed the species as B. gibsoni. Haplotype networks were constructed, and diversity indices were calculated, revealing significant genetic variability within the species. The Brazilian isolate clustered within the dominant haplotype for the 18S rRNA gene. This network suggests a possible recent population expansion of the pathogen. The cytb and cox3 genes exhibited high genetic variability, demonstrating their suitability as markers for intraspecific diversity analyses. Our findings suggest that B. gibsoni infections may be underdiagnosed in Brazil. Furthermore, considering the genetic diversity and widespread distribution of this pathogen, epidemiological, phylogenetic, and phylogeographic studies are essential to enhance understanding of its occurrence and impact within the country. Although this study is limited by the evaluation of a single case, it emphasizes the importance of molecular surveillance in canine babesiosis and highlights B. gibsoni, an emerging pathogen, as a critical differential diagnosis in the clinical evaluation of dogs in Brazil.