Infection Dynamics of the Tick-Borne Pathogen “Candidatus Neoehrlichia mikurensis” and Coinfections with Borrelia afzelii in Bank Voles in Southern Sweden

Abstract

ABSTRACTThe tick-borne bacterium “CandidatusNeoehrlichia mikurensis” has recently been recognized as a human pathogen. Together withBorrelia afzelii, it is one of the most common pathogens found in the tickIxodes ricinus. Here, we compared the epidemiologies of “Ca. Neoehrlichia mikurensis” andB. afzeliiby longitudinal sampling from May to September in one of their most abundant vertebrate hosts, the bank vole (Myodes glareolus), using real-time PCR for detection and quantification. The prevalences of “Ca. Neoehrlichia mikurensis” andB. afzeliiwere determined to be 19% (50/261) and 22% (56/261), respectively. The prevalence of “Ca. Neoehrlichia mikurensis” increased significantly during the sampling season. The clearance rate of “Ca. Neoehrlichia mikurensis” was significantly higher than that ofB. afzelii. We found a high frequency of double infections; 46% of all samples infected with “Ca. Neoehrlichia mikurensis” also had a coinfection withB. afzelii. The frequency of coinfections was significantly higher than expected from the prevalence of each pathogen. The high level of coinfections can be caused by interactions between the pathogens or might reflect variation in general susceptibility among voles.