GENETIC DIVERSITY OF ECHINOCOCCUS MULTILOCULARIS CESTODES IN EUROPE AS DETERMINED BY MITOCHONDRIAL AND NUCLEAR SEQUENCES

Abstract

Alveolar echinococcosis caused by metacestode stage of the tapeworm Echinococcus multilocularis is considered as one of the most pathogenic zoonoses in temperate and arctic regions. To more thoroughly ascertain genetic diversity in E. multilocularis tapeworms from Europe and to indicate transmission patterns of parasite, 25 isolates from a contiguous territory of eight European countries were subjected to sequencing of mitochondrial and nuclear DNA. A total of 2 715 nucleotide sequences in nad1, cox1, rrnS, atp6 and actII genes were screened in the current study. Whereas in 24 isolates profiles belonging to a previously described European clade were identified, the interesting feature was related to the detection of the form being close to North American strain N1 (that appeared to have lower zoonotic potential) in Austrian patient. The known occurrence of this variant has thus extended from the St. Lawrence Island in the Bering Sea and Russian isolates in Yakutia to central Europe. The finding indicates that N1 genotype has not only circumpolar trans-Beringian distribution, but during glacial events in Pleistocene a more southerly fox dispersal has likely transmitted N1 into central Europe. Further distinguished genotype was confined to four isolates from southern Germany (mountain range of Swabian Jura) and had five substitutions compared to the main European form. One Latvian isolate had two mutations in cox1, one of which was identical to German isolates from Feldstetten. Single nucleotide polymorphisms were detected in single isolates from Slovakia, Hungary and France in cox1 and actIIgenes. Lower genetic diversity detected in the examined isolates in more peripheral zones of its European distribution has supported Knapp ́s model (2009) suggesting that parasite focus in Europe is governed by “mainland-island” transmission where ancestral foci supply hitherto non-endemic areas by dispersal generated by fox mobility and migration.