Genetic variation and population structure of <i>Haemonchus contortus</i>: an <i>in-silico</i> analysis

<i>Haemonchus contortus</i> is a parasitic nematode that causes significant economic losses in ruminant livestock worldwide. In this study, we assessed the global genetic diversity and population structure of <i>H. contortus</i> using mitochondrial <i>COX1</i> and ribosomal <i>ITS2</i> sequences retrieved from the NCBI GenBank database. In total, 324 haplotypes of the <i>COX1</i> and 72 haplotypes of the <i>ITS2</i> were identified. The haplotype diversity values were all higher than 0.5, and the nucleotide diversity values were higher than 0.005. The Tajima's D value for <i>COX1</i> (-1.65634) was higher than that for <i>ITS2</i> (-2.60400). Fu's Fs, Fu and Li's D (FLD), and Fu and Li's F (FLF) values also showed high negative values, indicating a high probability of future population growth. In addition, the high fixation index (FST) value suggests significant genetic differentiation among populations. The haplotype networks of <i>H. contortus</i> populations based on <i>COX1</i> sequences revealed clear geographic clustering, whereas <i>ITS2</i> sequences showed more haplotype admixture across regions. The results of phylogenetic analyses were consistent with the haplotype networks. These findings highlighted that <i>H. contortus</i> populations exhibit significant genetic variation and are undergoing rapid population expansion, with clear genetic differences across geographic regions. This study established critical baseline data for future molecular epidemiology studies, which could guide region-specific parasite surveillance and targeted control strategies, thus helping to mitigate the risk of cross-border parasite transmission and drug resistance.