Haplotypic analysis of cox1 from Toxocara canis demonstrates five distinct clades that are not geographically defined

Abstract

BackgroundToxocara canisis a cosmopolitan parasite of dogs that is transmitted transplacentally to puppies resulting in widespread shedding of eggs in the environment. However, it is not clear if there are dominant parasite genotypes that are more common, pathogenic, or likely to be zoonotic.Methods/principle findingsSequences of mitochondrialcox1gene from adult worms were used to compare parasites from the United States with submitted sequences from parasites isolated from dogs in different countries. Our analysis revealed at least 55 haplotypes. While we expected the North American worms to form a distinct cluster, we found haplotypes ofT.canisreported elsewhere existing in this population. Interestingly, combining the sequence data from our study with the available GenBank data, analysis ofcox1sequences results in five distinct clades that are not geographically defined.ConclusionsThe five clades ofT.canisrevealed in this study potentially have unique life histories, traits, or host preferences. Additional investigation is needed to see if these distinct clades represent cryptic species with clinically useful attributes or genotypes with taxonomic value. Evaluation of common mitochondrial genes may reveal distinct populations of zoonoticT.canis.