Spatial and seasonal variation in the prevalence of Anaplasma phagocytophilum and Borrelia burgdorferi sensu lato in questing Ixodes ricinus ticks in Norway

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.

The prevalence of Borrelia burgdorferi sensu lato in questing Ixodes ricinus ticks in Norway

“…We detected lower prevalence of Borrelia infection in questing ticks from western regions with high density of red deer compared to the southeast, that could be due dilution of Borrelia in feeding ticks. Another study recently conducted in the west of Norway (Mysterud et al, 2013) confirmed the hypothesis of the dilution of B. burgdorferi s.l. in ticks in areas with high density of red deer.…”

“…We detected a significantly higher prevalence of Borrelia in adult ticks compared with nymphs and a higher infection rate among females than males (Table 2). Such differences were also registered in the study of Mysterud et al (2013) conducted along the western coast of Norway in 2011.…”

“…in ticks in areas with high density of red deer. The migration of red deer, however, may play an important role in the dispersal to new locations of ticks and to keep a high abundance of ticks in certain areas (Qviller et al, 2013).…”

Seroprevalence of antibodies to tick-borne encephalitis virus and Anaplasma phagocytophilum in healthy adults from western Norway

“…A. phagocytophilum was detected in 8.8% of I. ricinus in Sogn and Fjordane in a survey performed in 2011 [16], while an earlier study performed in 2006-7 found a lower prevalence (1.4% and 0.0% in two different locations, respectively) [17].…”

The wild life of tick-borne pathogens

“…This is in line with previous studies in Europe that found a dilution effect of deer abundance on NIP for Borrelia burgdorferi s.l. 259,262,263 . In contrast, NIP for the two B. burgdorferi s.l.…”