Comparative Genomic Analysis and Species Delimitation: A Case for Two Species in the Zoonotic Cestode Dipylidium caninum.

Dipylidium caninum (Linnaeus, 1758) is a common zoonotic cestode of dogs and cats worldwide. Previous studies have demonstrated the existence of largely host-associated canine and feline genotypes based on infection studies, differences at the 28S rDNA gene, and complete mitochondrial genomes. There have been no comparative genome-wide studies. Here, we sequenced the genomes of a dog and cat isolate of Dipylidium caninum from the United States using the Illumina platform at mean coverage depths of 45× and 26× and conducted comparative analyses with the reference draft genome. Complete mitochondrial genomes were used to confirm the genotypes of the isolates. Genomes of D. caninum canine and feline genotypes generated in this study, had an average identity of 98% and 89%, respectively, when compared to the reference genome. SNPs were 20 times higher in the feline isolate. Comparison and species delimitation using universally conserved orthologs and protein-coding mitochondrial genes revealed that the canine and feline isolates are different species. Data from this study build a base for future integrative taxonomy. Further genomic studies from geographically diverse populations are necessary to understand implications for taxonomy, epidemiology, veterinary clinical medicine, and anthelmintic resistance.