High haplotype diversity and recent population expansion of Fasciola hepatica in Iran: Insights from cox1 mitochondrial analysis

Fascioliasis is a globally distributed zoonotic disease that poses substantial veterinary and public health concerns, with high endemicity in Iran. Knowledge about the population structure, genetic diversity, and haplotype distribution throughout the country can be effective in control and drug-resistance management strategies. Therefore, the present study was conducted to evaluate the genetic diversity of Fasciola species in slaughtered livestock in Iran and to determine haplotype networks across the country. From 20 parasite samples collected from seven provinces, the mitochondrial cytochrome c oxidase I ( cox1 ) gene was amplified and sequenced. BLAST analysis confirmed the identity of 17 isolates as F. hepatica (94.75 to 99.74% percent identity) and 3 isolates as F. gigantica (98.36 to 99.12% percent identity). In F. hepatica , nine novel haplotypes with 60 variable sites were identified, with haplotype and nucleotide diversities of 0.926 and 0.047, respectively. Three haplotypes were identified in F. gigantica with haplotype and nucleotide diversities of 1.00 and 0.017, respectively. Neutrality tests, including Tajima’s D (-0.606) and Fu’s Fs (3.75), indicated an absence of recent demographic expansion in F. hepatica populations. By combining the F. hepatica sequences obtained from the present study with previously published Iranian sequences, a national dataset of 187 sequences based on the cox1 gene was analyzed, revealing 49 distinct haplotypes with H11 as the evolutionary core in 13 provinces. Significant negative values of Tajima’s D and Fu’s Fs (-2.515 and − 33.27, respectively) reinforced the pattern of recent population expansion. The findings of the present study indicate the genetic richness of Iranian Fasciola populations and provide valuable data for designing targeted epidemiological control and monitoring approaches.