Comparison of Fasciola hepatica genotypes in relation to their ability to establish patent infections in the final host

- Sequence analysis of the mitochondrial DNA fragment revealed 7 genotypes.
- Microsatellite analysis revealed 4 alleles at locus Fh15, 2 at Fh23 and 3 at Fh25.
- There was also no difference in the ability of individual genotypes to reach patency.
- Heterozygous flukes may have a selective advantage during tissue migration.

Fasciola hepatica is a common and economically important parasite of sheep and cattle. Although its marked genetic heterogeneity is well recognised, an association between haplotypes and specific phenotypic traits has yet to be identified. Using experimental infections in cattle this study investigated whether a fragment of mitochondrial DNA (coding for cytochrome c oxidase subunit III, transfer RNA histidine and cytochrome b) and 3 nuclear microsatellite loci (Fh15, Fh23 and Fh25) could be used as markers for the parasite's ability to complete its tissue migration and establish in the liver of the final host. While we did not detect any shift in the frequency of the various genotypes in the population of metacercariae used for the infection on the one hand and the flukes collected from the liver on the other, there was an indication that parasites with heterozygous microsatellite alleles may have a selective advantage over homozygote parasites during their migration in the final host.