Using the genetics of Echinococcus multilocularis to trace the history of expansion from an endemic area.

Alveolar echinococcosis, caused by the cestode Echinococcus multilocularis, is the most serious parasitic disease for humans in Europe, with a sylvatic life cycle generally between small rodents and red foxes. General expansion of the range of E. multilocularis has been observed across Europe over the last 15years. In France, a westward spread of the known endemic areas of the parasite was described recently. For genotyping, the microsatellite EmsB was used to trace expansion in five French areas. A total of 22 EmsB profiles were identified, with five similar to those previously described in other parts of Europe. An imbalance of genetic diversity was observed between the five areas which also revealed their interconnection with the presence of common profiles, notably the two main profiles both present in all regions except one in the North. These two findings are similar to those described at the European level, highlighting transmission of the parasite by a mainland-island system. A spatio-temporal scenario of the expansion of E. multilocularis can be proposed with spread from the French historical focus in eastern France to the Lorraine, the Champagne-Ardenne and finally the North, while simultaneously another expansion has occurred from the historical focus into the West. The colonization by the parasite into the West and North areas from the historical focus was probably due to the migration of foxes several decades ago. Recent detection of the parasite in new endemic "départements" may be due to more active research rather than a recent spread of the parasite. Regarding the numerous data obtained by the different EmsB analyses, principally across Europe, centralization of all the profiles described in a public databank appears necessary in order to obtain a precise understanding of transmission of the parasite from one country to another.