Elucidating spread in the Americas by using phylogenetic and phylogeographic analyses.

is a parasitic nematode of domestic and wild canids of the world. This nematode induces esophageal spirocercosis and may eventually lead to carcinomas, aortic aneurisms, and death of the animal. Two genotypes of have been described based on specimens from Europe, Asia, Africa, and Oceania, but no profound analysis has been conducted with from the Americas. To study this, specimens isolated from domestic dogs from Mexico, Costa Rica, and the United States, were molecularly characterized using 18S rDNA and 1 fragments. Bayesian inference (BI) phylogenetic trees, Templeton-Crandall-Sing (TCS) haplotype networks and Principal coordinate analysis on nucleotide distances were constructed for each locus separately. In addition, a phylogeographic study using a fragment of the 1 gene was used to infer the evolutionary history of the genus. BI 1 trees grouped from the Americas in genotype 1, together with Israeli specimens, and showed a high nucleotide identity with those worms. In the TCS network, American specimens clustered next to Israeli . Furthermore, the 18S rDNA gene fragment separated Costa Rican worms from African, Asian, and European specimens and other species of the family Spiruridae. Interestingly, the phylogeographic analysis suggested that the origin of was in Europe, and it later diverged into that spread first to Africa, then to Asia and finally to the Americas. Therefore, we suggest that the worms from the American continent might have originated from Asia by dispersion of infected intermediate, paratenic or definitive hosts.