Genetic diversity of Echinococcus multilocularis on a local scale

Abstract

Echinococcus multilocularis is the causative agent of human Alveolar Echinococcosis (AE), and it is one of the most lethal zoonotic infections in the Northern Hemisphere. In France, the eastern and central regions are endemic areas; Franche-Comté, Lorraine and Auvergne are particularly contaminated. Recently, several human cases were recorded in the French Ardennes area, a region adjacent to the western border of the E. multilocularis range in France. A previous study in this focus described a prevalence of over 50% of the parasite in red foxes. The present study investigated the genetic diversity of adult worms collected from foxes in a 900 km 2 area in the Ardennes. Instead of a conventional mitochondrial target (ATP6), two microsatellite targets (EmsB and NAK1) were used. A total of 140 adult worms isolated from 25 red foxes were genotyped. After hierarchical clustering analyses, the EmsB target enabled us to distinguish two main assemblages, each divided into sub-groups, yielding the differentiation of six clusters or assemblage profiles. Thirteen foxes (52% of the foxes) each harbored worms from at least two different assemblage profiles, suggesting they had become infected by several sources. Using the NAK1 target, we identified 3 alleles, two found in association with the two EmsB assemblages. With the NAK1 target, we investigated the parasite breeding system and the possible causes of genetic diversification. Only one fox harbored hybrid worms, indicative of a possible (and rare) occurrence of recombination, although multiple infections have been observed in foxes. These results confirm the usefulness of microsatellite targets for assessing genetic polymorphism in a geographically restricted local range.