Comparative genomics and phylogenomics of Trichostrongyloidea mitochondria reveal insights for molecular diagnosis and evolutionary biology of nematode worms

Haemonchus placei (Nematoda:Trichostrongyloidea:Haemonchidae) is a parasite of cattle and other ruminants that reduces the weight gain and increases mortality causing significant economic losses to livestock worldwide. Here we sequenced and annotated its complete mitochondrion (mt) genome, obtaining a circular molecule of 13,664bp long and 78.8% A+T content (KT955899). Besides, all 10mt genomes publicly available for the Trichostrongyloidea superfamily were downloaded from GenBank database. In the comparison between the complete mt genome sequences of the 3 species from the Haemonchidae family, an AT-rich region of variable size was observed. A primer pair that amplifies this region was proposed to allow the molecular diagnostic and differentiation between H. placei and H. contortus infections. Furthermore, the evolutionary relationship between H. placei and other members of Trichostrongyloidea was inferred based on a phylogenomics approach. All mitochondrial gene sequences were aligned and then concatenated into a supermatrix dataset. A maximum likelihood tree was produced and confirmed the monophyly of Haemonchidae family. The superfamily Trichostrongyloidae was also recovered as a monophyletic clade. The complete mt genome sequence reported here may be used to develop new genetic markers and investigate phylogenetic and geographic relationships between isolates as well as to assess population diversity and allow health control programs monitoring.