Genetic differentiation in eastern European and western Asian populations of the liver fluke, Fasciola hepatica, as revealed by mitochondrial nad1 and cox1 genes

Partial sequences of mitochondrial genes nad1 (316 bp) and cox1 (429 bp) were analyzed to estimate the variability of the liver fluke samples collected in 20 localities in Russia, Belarus, Ukraine, Bulgaria, Armenia, Azerbaijan, Georgia, Turkey, Turkmenistan, and China. The sequences had 4.1% (nad1) and 2.3% (cox1) of variable sites, and 13 and 10 haplotypes were identified among nad1 and cox1 genes, respectively. Spatial analysis of genetic and nucleotide diversity indicated little or no structuring of genetic variation between hosts or regions. The analysis of distribution of both separate and combined (nad1 + cox1) haplotypes revealed the existence of 2 well-defined lineages with 2 main haplotypes and a number of shared divergent haplotypes. Our study showed that the first lineage included the main N1-C1 haplotype, which was found in Australia, China, Georgia, Turkey, Armenia, Azerbaijan, and in all European populations (from Russia, Belarus, Ukraine, Bulgaria). The second lineage was found in all European populations and in populations from Armenia and Azerbaijan. It was suggested that one of the lineages (I) has an Asian origin. The possible source of mtDNA variability and associations between lineage divergence of parasite and its definitive hosts (cattle and sheep) are discussed.