Geographic pattern of genetic variation in the fox tapeworm Echinococcus multilocularis

Area of Science:

• Parasitology
• Molecular Evolution
• Genetics

Background:

• Echinococcus multilocularis is the causative agent of human alveolar echinococcosis.
• Understanding its genetic diversity is crucial for disease control and evolutionary studies.
• Previous studies have indicated potential genetic structuring within the parasite.

Purpose of the Study:

• To evaluate the intraspecific genetic variation of Echinococcus multilocularis.
• To investigate the geographic structuring of parasite populations across Europe, Asia, and North America.
• To assess the evolutionary conservation of the ezrin/radixin/moesin-like protein (elp) antigen for immunodiagnosis.

Main Methods:

• Sequencing of mitochondrial DNA (3 protein-coding genes) and nuclear DNA (elp antigen region).
• Analysis of 76 geographic isolates from Europe, Asia, and North America.
• Phylogenetic tree construction and parsimony network analysis to infer genetic relationships and population structure.

Main Results:

• Low genetic variation observed in mitochondrial DNA, yielding 18 distinct haplotypes (0.03–1.91% divergence).
• Phylogenetic analyses revealed distinct European, Asian, and North American clades, with some exceptions like an Inner Mongolian haplotype.
• Coexistence of Asian and North American haplotypes observed in the Bering Sea region, suggesting complex population dynamics.
• The nuclear DNA sequence of the elp antigen region was highly conserved across all isolates.

Conclusions:

• Distinct Echinococcus multilocularis populations likely evolved in glacial refugia and were maintained by host mammals.
• The genetic structure suggests historical isolation and subsequent admixture events.
• The conserved elp antigen is a promising target for immunodiagnosis applicable to all endemic regions.