Genetic heterogeneity of Fasciola hepatica isolates in the northwest of Spain.

The liver fluke Fasciola hepatica is a worldwide distributed trematode parasite of great veterinary importance. In Spain, the prevalence of the infection is up to 56% in sheep. Its control is mainly based on the use of anthelmitics, although some resistant populations have been described. Genetic studies of the genus Fasciola have been focused on the 28S ribosomal deoxyribonucleic acid (rDNA) gene, with no intraspecific variations and a few interspecific nucleotide differences. We have designed a specific polymerase chain reaction to amplify and sequence a 510-bp-long fragment of the gene to characterize several F. hepatica ovine isolates from the northwest of Spain. All the isolates rendered the expected results on the agarose gel, while sequencing revealed some differences in the 34 site. The anthelmintic-resistant specimens showed the same nucleotide differing of the sensitive ones. Comparing to other studies, our results conclude that there are some genetic variations in F. hepatica (at the level of the 28S rDNA), including heterozygous specimens. In conclusion, a genetic heterogeneity has been found in the F. hepatica populations of ovine origin in the northwest of Spain, using an assay that could be useful for further epidemiology and characterization studies.