Molecular epidemiology of rabies virus in France: comparison with vaccine strains.

A molecular epidemiological study of the rabies virus currently prevalent in France was carried out by directly sequencing polymerase chain reaction-amplified genes. The rabies virus pseudogene psi was chosen as the most divergent genomic area, and as such the best 'clock' for measuring virus evolution. Sequence comparisons between 12 wild rabies virus isolates indicated strong conservation whatever the host and wherever the virus had been isolated. This holds true for a unique wild reservoir, the fox. On the other hand, a good correlation between genetic and geographical criteria indicates a slow evolution of the wild virus in parallel with the spatio-temporal progression of the epizootic. In contrast to their intrinsic homogeneity (about 2% divergence), the wild isolate sequences showed a marked divergence from those of vaccine seed strains (about 14.7%). This finding invites world-wide molecular epidemiological studies, particularly in countries in which vaccination failures have been reported.