The first report on natural Enterocytozoon bieneusi and Encephalitozoon spp. infections in wild East-European House Mice (Mus musculus musculus) and West-European House Mice (M. m. domesticus) in a hybrid zone across the Czech Republic-Germany border.

To determine the occurrence of potentially human pathogenic microsporidia (Enterocytozoon bieneusi and Encephalitozoon spp.) in wild mice, we examined 289 East-European House Mice (Mus musculus musculus) and West-European House Mice (M. m. domesticus) trapped at 74 localities in an area across the Czech-German border. Microsporidia were detected at 33 localities, in 34% of M. m. musculus and 33% of M. m. domesticus examined specimens. Single-species infection was detected in 23 mice for E. hellem, 42 mice for E. cuniculi and 25 mice for E. bieneusi. No Encephalitozoon intestinalis positive animals were identified. Moreover, co-infections were detected in 6 animals; E. bieneusi co-existed with E. cuniculi or E. hellem in 3 mice. The natural infection of E. hellem has never been recorded in mice before. No differences were found by a statistical analysis of microsporidia occurrence between the House Mouse subspecies. Although the gender-dependent infestation of microsporidia was statistically supported in M. m. musculus, no significant differences were observed when the occurrence of microsporidia was estimated for all males and females irrespective of the House Mouse subspecies. The results of this report document the low host specificity of detected microsporidia species and imply the importance of synanthropic rodents as a potential source of human microsporidial infection.