The Mitogenome of the Haecon-5 Strain of Haemonchus contortus and a Comparative Analysis of Its Nucleotide Variation with Other Laboratory Strains

<i>Haemonchus contortus</i> (the barber's pole worm)-a highly pathogenic gastric nematode of ruminants-causes significant economic losses in the livestock industry worldwide. <i>H. contortus</i> has become a valuable model organism for both fundamental and applied research (e.g., drug and vaccine discovery) because of the availability of well-defined laboratory strains (e.g., MHco3(ISE).N1 in the UK and Haecon-5 in Australia) and genomic, transcriptomic and proteomic data sets. Many recent investigations have relied heavily on the use of the chromosome-contiguous genome of MHco3(ISE).N1 in the absence of a genome for Haecon-5. However, there has been no genetic comparison of these and other strains to date. Here, we assembled and characterised the mitochondrial genome (14.1 kb) of Haecon-5 and compared it with that of MHco3(ISE).N1 and two other strains (i.e., McMaster and NZ_Hco_NP) from Australasia. We detected 276 synonymous and 25 non-synonymous single nucleotide polymorphisms (SNPs) within Haecon-5. Between the Haecon-5 and MHco3(ISE).N1 strains, we recorded 345 SNPs, 31 of which were non-synonymous and linked to fixed amino acid differences in seven protein-coding genes (<i>nad</i>5, <i>nad</i>6, <i>nad</i>1, <i>atp</i>6, <i>nad</i>2, <i>cyt</i>b and <i>nad</i>4) between these strains. Pronounced variation (344 and 435 SNPs) was seen between Haecon-5 and each of the other two strains from Australasia. The question remains as to what impact these mitogenomic mutations might have on the biology and physiology of <i>H. contortus</i>, which warrants exploration. The high degree of mitogenomic variability recorded here among these strains suggests that further work should be undertaken to assess the nature and extent of the nuclear genomic variation within <i>H. contortus</i>.