Molecular comparison of Gasterophilus intestinalis and Gasterophilus nasalis from two distinct areas of Poland and Italy based on cox1 sequence analysis

In this study, Gasterophilus intestinalis and Gasterophilus nasalis collected from horses in northeastern Poland and southern Italy were genetically compared. The cox1 sequences of the Polish and Italian G. nasalis larvae revealed a higher degree of geographic genetic diversity, with an intra-specific variation rate of 1.27%, than the G. nasalis specimens collected in Poland (intra-specific variation rate: 0.49%) and those collected in Italy (intra-specific variation rate: 0.58%). However, the level of genetic homology of the Polish and Italian G. intestinalis specimens (intra-specific variation rate: 1.27%) was similar to that of the G. intestinalis larvae collected in northeastern Poland (intra-specific variation rate: 0.94%) and those collected in southern Italy (intra-specific variation rate: 1.16%). Analysis of the restriction enzyme sites in the coxI gene of G. nasalis and G. intestinalis showed that the nucleotide polymorphism (NP) at position 1050 of this gene determines cleavage by MnlI only in G. nasalis, making it possible to differentiate the two species using PCR-RFLP. Interestingly, comparison of the nucleotide sequences of the PCR-amplified coxI gene fragments from the Italian specimens of G. nasalis with other analyzed cox1 genes revealed an additional NP at position 1236 of cox1 gene, recognized by MnlI. The present study shows that G. nasalis specimens from different geographical areas display a level of genetic diversity which can influence PCR-RFLP analysis.