Are Apodemus spp. mice and Myodes glareolus reservoirs for Borrelia miyamotoi, Candidatus Neoehrlichia mikurensis, Rickettsia helvetica, R. monacensis and Anaplasma phagocytophilum?

In Europe, in addition to Borrelia burgdorferi sensu lato and tick-borne encephalitis (TBE) virus, other zoonotic pathogens, like B. miyamotoi, a species related to the relapsing fever spirochaetes, Candidatus Neoehrlichia mikurensis (N. mikurensis), Rickettsia helvetica, Rickettsia monacensis, and Anaplasma phagocytophilum have been reported in the ixodid tick Ixodes ricinus. No study was conducted to identify reservoir hosts for these pathogens. Here, we investigated the role played by wild rodents in the natural transmission cycle of B. miyamotoi, N. mikurensis, R. helvetica, R. monacensis, and A. phagocytophilum in Switzerland. In 2011 and 2012, small mammals were captured in an area where these pathogens occur in questing ticks. Ixodes ricinus ticks infesting captured small mammals were analysed after their moult by PCR followed by reverse line blot to detect the different pathogens. Xenodiagnostic larvae were used to evaluate the role of rodents as reservoirs and analysed after their moult. Most of the 108 captured rodents (95.4%) were infested by I. ricinus ticks; 4.9%, 3.9%, 24.0%, and 0% of the rodents were infested by Borrelia, N. mikurensis, Rickettsia spp., and A. phagocytophilum-infected larvae, respectively. Borrelia afzelii, B. miyamotoi, N. mikurensis, Rickettsia spp., and A. phagocytophilum were detected in 2.8%, 0.17%, 2.6%, 6.8%, and 0% of the ticks attached to rodents, respectively. Borrelia afzelii was transmitted by 4 rodents to 41.2% of the xenodiagnostic ticks, B. miyamotoi by 3 rodents to 23.8%, and N. mikurensis was transmitted by 6 rodents to 41.0% of the xenodiagnostic ticks. None of the tested rodent transmitted Rickettsia spp. or A. phagocytophilum to I. ricinus xenodiagnostic larvae. This study showed that rodents are reservoir hosts for B. miyamotoi and N. mikurensis in Europe.