Are Babesia vogeli genotypes associated with Rhipicephalus sanguineus and Rhipicephalus linnaei distribution?

BACKGROUND

In South America, Babesia vogeli is the primary causative agent of canine babesiosis, and brown dog ticks (Rhipicephalus sanguineus sensu lato) are the vectors. The recent separation of brown dog ticks into Rhipicephalus sanguineus sensu stricto ("temperate lineage") and Rhipicephalus linnaei ("tropical lineage") raised suspicions of the possibility of two distinct Babesia genotypes or even species being transmitted by these tick species.

METHODS

To investigate this hypothesis, dog blood samples from Brazil (eight states), Paraguay, and Uruguay were collected to determine the genetic diversity of B. vogeli in South America. The samples were collected from temperate regions (southern Brazil and Uruguay), where the putative vector is R. sanguineus, and from the tropical areas (southeastern, midwestern, northeastern, and northern Brazil and Paraguay), where R. linnaei is the vector. DNA samples from B. vogeli-positive dogs were extracted to amplify the 18S ribosomal RNA, internal transcribed spacers 1 and 2, heat shock protein 70, cytochrome c oxidase subunit 1, cytochrome oxidase c subunit 3, and cytochrome b genes. The sequences obtained were aligned with available B. vogeli sequences in GenBank and other homologous sequences to construct phylogenetic trees, haplotype networks, and matrices.

RESULTS

Our haplotypic and phylogenetic analyses congruently indicated the existence of one genotype in temperate areas and another in tropical areas, where R. sanguineus and R. linnaei act as vectors, respectively. While the percentage of similarity varied among the evaluated genetic markers, the results indicated a clear differentiation between the B. vogeli genotypes associated with temperate and tropical regions.

CONCLUSIONS

Our data indicate the existence of two B. vogeli genotypes in South America, associated with temperate and tropical areas. This contributes to a better understanding of B. vogeli's genetic diversity and opens new avenues for researching the ecology and coevolution of B. vogeli genotypes and their tick vectors. Owing to their correlation with the climatic region and the historical nomenclature of their vectors, we suggest the nomenclature of "temperate" and "tropical" B. vogeli genotypes.