Microsporidian disease of the invasive amphipod Dikerogammarus villosus and the potential for its transfer to local invertebrate fauna.

12 pagesInternational audienceInvasive species may introduce novel pathogens to a colonised area. Most of the time emerging pathogens are detected a posteriori, but recognition of a priori emergence of an invasive disease by host shift may be useful for predictive purposes. Here, we studied if the microsporidian parasite Cucumispora dikerogammari infecting the invasive Ponto-Caspian amphipod Dikerogammarus villosus, has the potential to become an emergent disease in invaded rivers in Western and Central Europe. We first showed that this parasite decreases the survival of D. villosus in the later stages of infection development. However, the host reproduces earlier in response to the infection, which could potentially reduce the negative impact of the parasite on host populations. Cucumispora dikerogammari is able to infect other crustacean species as revealed by our experimental infections. However, field census showed that it was found in other Ponto-Caspian species of amphipods only when it was observed in high prevalence in its native host, and when this host was at moderate frequencies in the community. Therefore, adaptation of C. dikerogammari to native gammaridean hosts has probably not been realized in the wild yet. However, since several environmental factors may promote future adaptations of the parasite to novel host species, we suggest C. dikerogammari should be included in surveillance networks for emergent disease in freshwater