Genetic diversity and relatedness of Fasciola spp. isolates from different hosts and geographic regions revealed by analysis of mitochondrial DNA sequences.

Abstract The present study examined sequence variability in a portion of the mitochondrial cytochrome c oxidase subunit 1 (p cox 1) and NADH dehydrogenase subunits 4 and 5 (p nad 4 and p nad 5) among 39 isolates of Fasciola spp., from different hosts from China, Niger, France, the United States of America, and Spain; and their phylogenetic relationships were re-constructed. Intra-species sequence variations were 0.0–1.1% for p cox 1, 0.0–2.7% for p nad 4, and 0.0–3.3% for p nad 5 for Fasciola hepatica ; 0.0–1.8% for p cox 1, 0.0–2.5% for p nad 4, and 0.0–4.2% for p nad 5 for Fasciola gigantica , and 0.0–0.9% for p cox 1, 0.0–0.2% for p nad 4, and 0.0–1.1% for p nad 5 for the intermediate Fasciola form. Whereas, nucleotide differences were 2.1–2.7% for p cox 1, 3.1–3.3% for p nad 4, and 4.2–4.8% for p nad 5 between F. hepatica and F. gigantica ; were 1.3–1.5% for p cox 1, 2.1–2.9% for p nad 4, 3.1–3.4% for p nad 5 between F. hepatica and the intermediate form; and were 0.9–1.1% for p cox 1, 1.4–1.8% for p nad 4, 2.2–2.4% for p nad 5 between F. gigantica and the intermediate form. Phylogenetic analysis based on the combined sequences of p cox 1, p nad 4 and p nad 5 revealed distinct groupings of isolates of F. hepatica , F. gigantica , or the intermediate Fasciola form irrespective of their origin, demonstrating the usefulness of the mtDNA sequences for the delineation of Fasciola species, and reinforcing the genetic evidence for the existence of the intermediate Fasciola form.