Abstract
BackgroundUnderstanding the variation in prevalence of Borrelia burgdorferi sensu lato (Lyme Borreliosis Spirochaetes, LBS) and Anaplasma phagocytophilum (causing tick-borne fever in ruminants and human granulocytic ehrlichiosis) in ticks is vital from both a human and an animal disease perspective to target the most effective mitigation measures. From the host competence hypothesis, we predicted that prevalence of LBS would decrease with red deer density, while prevalence of A. phagocytophilum would increase.MethodsBased on a sample of 112 adult and 686 nymphal Ixodes ricinus ticks collected with flagging during questing from 31 transects (4–500 m long) corresponding to individual seasonal home ranges of 41 red deer along the west coast of Norway, we tested whether there were spatial and seasonal variations in prevalence with a special emphasis on the population density of the most common large host in this area, the red deer (Cervus elaphus). We used a multiplex real-time PCR assay for detection of A. phagocytophilum and LBS.ResultsPrevalence of LBS was higher in adult female ticks (21.6%) compared to adult male ticks (11.5%) and nymphs (10.9%), while prevalence was similar among stages for prevalence of A. phagocytophilum (8.8%). Only partly consistent with predictions, we found a lower prevalence of LBS in areas of high red deer density, while there was no relationship between red deer density and prevalence of A. phagocytophilum in ticks. Prevalence of both bacteria was much higher in ticks questing in May compared to August.ConclusionsOur study provides support to the notion that spatial variation in host composition forms a role for prevalence of LBS in ticks also in a northern European ecosystem, while no such association was found for A. phagocytophilum. Further studies are needed to fully understand the similar seasonal pattern of prevalence of the two pathogens.
Highlights
Understanding the variation in prevalence of Borrelia burgdorferi sensu lato (Lyme Borreliosis Spirochaetes, LBS) and Anaplasma phagocytophilum in ticks is vital from both a human and an animal disease perspective to target the most effective mitigation measures
The tick-borne disease Lyme borreliosis, caused by certain genotypes of the Borrelia burgdorferi sensu lato complex, hereafter called Lyme Borreliosis Spirochaetes (LBS), is one of the ones having the highest potential of severity to human society [2]
The innate immune system of cervids may even kill LBS in infected ticks feeding on them [21,22]. This is supported by the lower prevalence of LBS reported from ticks collected on roe deer (Capreolus capreolus) and moose (Alces alces) compared to ticks collected in the landscape [23]
Summary
Understanding the variation in prevalence of Borrelia burgdorferi sensu lato (Lyme Borreliosis Spirochaetes, LBS) and Anaplasma phagocytophilum (causing tick-borne fever in ruminants and human granulocytic ehrlichiosis) in ticks is vital from both a human and an animal disease perspective to target the most effective mitigation measures. Among emerging infectious diseases linked to climate change in Europe, the tick-borne disease Lyme borreliosis, caused by certain genotypes of the Borrelia burgdorferi sensu lato complex, hereafter called Lyme Borreliosis Spirochaetes (LBS), is one of the ones having the highest potential of severity to human society [2] Another important disease agent in ticks is Anaplasma phagocytophilum. Passerine birds are the main reservoir for B. garinii [28] and rodents for B. afzelii [29] These are the two most common genospecies of LBS circulating in ticks in Europe, followed by B. burgdorferi sensu stricto and B. valaisiana [30], while prevalence of B. burgdorferi sensu stricto is lower in Norway [31]. Both B. afzelii and B. garinii, which are the dominating genotypes found in questing ticks in Norway [30], can cause human disease and LBS as a group are important and are our focus here
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