First evidence of Ehrlichia sp in wild Microtus arvalis from Poland

We examined a total of 73 Microtus arvalis, 168 Clethrionomys glareolus and 17 Apodemus flavicollis trapped in the Mazury Lakes district of North-East ern Poland, in the spring, summer and autumn of 1998. Three M. arvalis, (2 in summer and 1 in autumn) carried Ehrlichia sp. (overall prevalence = 4.1% ), whereas infection was not detected in the other rodent species. We hypot hesize that Ixodes ricinus (the most common tick in the region) with which the animals were heavily infested, constitutes the likely natural vector fo r this pathogen and that M. arvalis are its natural reservoir.