Abstract
BackgroundSmall mammals are crucial for the life history of ixodid ticks, but their role and importance in the transmission cycle of tick-borne pathogens is mostly unknown. Candidatus Neoehrlichia mikurensis (CNM) and Anaplasma phagocytophilum are both tick-borne pathogens, and rodents are discussed to serve as main reservoir hosts for CNM but not for the latter especially in Germany. Analysing the prevalence of both pathogens in small mammals and their ticks in endemic regions may help to elucidate possible transmission paths in small mammal populations and between small mammals and ticks.MethodsIn 2012 and 2013, small mammals were trapped at three different sites in Germany. DNA was extracted from different small mammal tissues, from rodent neonates, foetuses and from questing and attached ticks. DNA samples were tested for CNM and A. phagocytophilum by real-time PCR. Samples positive for A. phagocytophilum were further characterized at the 16S rRNA gene locus.ResultsCNM was detected in 28.6% of small mammals and in 2.2% of questing and 3.8% of attached ticks. Altogether 33 positive ticks were attached to 17 different hosts, while positive ticks per host ranged between one and seven. The prevalences for this pathogen differed significantly within small mammal populations comparing sites (χ2: 13.3987; p: 0.0004) and between sexes. Male rodents had an approximately two times higher chance of infection than females (OR: 1.9652; 95% CI: 1.32-2.92). The prevalence for CNM was 31.8% (95% CI: 22-44) in rodent foetuses and neonates (23 of 67) from positive dams, and 60% (95% CI: 35.7-80.25) of positive gravid or recently parturient rodents (9 out of 15) had at least one positive foetus or neonate. Anaplasma phagocytophilum was detected at a low percentage in rodents (0-5.6%) and host-attached ticks (0.5-2.9%) with no significant differences between rodent species. However, attached nymphs were significantly more often infected than attached larvae (χ2: 25.091; p: <0.0001).ConclusionThis study suggests that CNM is mainly a rodent-associated pathogen and provides evidence for a potential transplacental transmission in rodents. In contrast, most of the rodent species captured likely represent only accidental hosts for A. phagocytophilum at the investigated sites.
Highlights
Small mammals are crucial for the life history of ixodid ticks, but their role and importance in the transmission cycle of tick-borne pathogens is mostly unknown
Belonging to the rickettsial family Anaplasmataceae, the tick-borne pathogens Candidatus Neoehrlichia mikurensis (CNM) and Anaplasma phagocytophilum are of considerable risk for human and animal health as they may cause lifethreatening diseases [3,4]
CNM is an emerging pathogen first discovered as an Ehrlichia-like species in I. ricinus ticks from the Netherlands in 1999 [13]- Later, it was found in wild rats (Rattus norvegicus) and I. ovatus ticks from Japan [14]
Summary
Small mammals are crucial for the life history of ixodid ticks, but their role and importance in the transmission cycle of tick-borne pathogens is mostly unknown. CNM is an emerging pathogen first discovered as an Ehrlichia-like species in I. ricinus ticks from the Netherlands in 1999 [13]- Later, it was found in wild rats (Rattus norvegicus) and I. ovatus ticks from Japan [14]. It was observed in 11 humans [15] with immune deficiency from Europe over the last decade causing unspecific symptoms such as fever, septicaemia and weight loss [2,16,17]. CNM could not be cultivated in vitro, and epidemiological research on reservoir hosts is still incomplete
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