It's a small world for parasites: evidence supporting the North American invasion of European Echinococcus multilocularis

Abstract

Echinococcus multilocularis ( Em ), the causative agent of human alveolar echinococcosis (AE), is present in the Holarctic region, and several genetic variants deem to have differential infectivity and pathogenicity. An unprecedented outbreak of human AE cases in Western Canada infected with a European-like strain circulating in wild hosts warranted assessment of whether this strain was derived from a recent invasion or was endemic but undetected. Using nuclear and mitochondrial markers, we investigated the genetic diversity of Em in wild coyotes and red foxes from Western Canada, compared the genetic variants identified to global isolates and assessed their spatial distribution to infer possible invasion dynamics. Genetic variants from Western Canada were closely related to the original European clade, with lesser genetic diversity than that expected for a long-established strain and spatial genetic discontinuities within the study area, supporting the hypothesis of a relatively recent invasion with various founder events.

Echinococcus multilocularis genetic diversity based on isolates from pigs confirmed the characteristic haplotype distribution and the presence of the Asian-like haplotype in Central Europe

“…Unusual geographical locations of E. multilocularis genotypes in terms of the continent have also recently been observed in North America, where the presence of genotypes characteristic for Europe was noted in adult tapeworms detected in coyotes ( 11 ) and in larvae derived from a dog ( 13 ). This was also confirmed by recent studies conducted in red foxes and coyotes in Canada, where various European-like haplotypes were found among North American haplotypes ( 32 ). Phylogenetic analysis showed some differences among European-like haplotypes isolated in North America, which suggests different scenarios with multiple introductions of European strains of E. multilocularis to Canada, probably occurring over several hundred years ( e.g.…”

“…Phylogenetic analysis showed some differences among European-like haplotypes isolated in North America, which suggests different scenarios with multiple introductions of European strains of E. multilocularis to Canada, probably occurring over several hundred years ( e.g. through dogs originally imported from Europe) ( 32 ).…”

“…Knowledge of genetic diversity provided the means to observe the mixing of genotypes characteristic for one continent with those characteristic for others. Example of this are the finding of Asian-like haplotypes in Europe ( 18 , 37 ) or European-like examples in North America ( 12 , 32 ).…”

Molecular phylogenetic analysis of Echinococcus multilocularis from horses raised in Canada or Japan, using mitochondrial cytochrome b gene–targeted PCR

“…These findings, and the results of this study, suggest that the definitive hosts of E. multilocularis in Alberta, Canada may carry a high proportion of the European haplotypes of E. multilocularis . This idea was supported by a recent report ( Santa et al, 2023 ).…”

Infection of sheep by Echinococcus multilocularis in Gansu, China: evidence from mitochondrial and nuclear DNA analysis

“…Genetic characterization using mitochondrial deoxyribonucleic acid ( mt DNA) markers, the microsatellite EmsB, and a multi-locus nuclear DNA markers were applied to E. multilocularis genotyping studies [ 23 ]. Although E. multilocularis is less diverse than E. granulosus sensu lato, recent taxonomic studies have shown intra-specific variations within E. multilocularis at the global scale, allowing the identification of four genetic subgroups that are restricted to specific geographic regions: European, North American, Asian, and Mongolian [ 8 , 24 – 26 ].…”