Questing abundance of adult taiga ticks Ixodes persulcatus and their Borrelia prevalence at the north-western part of their distribution

• Published in: Parasites & Vectors
• Main Authors: Veli-Matti Pakanen, Jani J. Sormunen, Ella Sippola, Donald Blomqvist, Eva R. Kallio
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2020
• Subjects: Finland; Coastal forest; Co-infection; Ixodes persulcatus; Temporal tick dynamics; Infectious and parasitic diseases; RC109-216; Strong Peak; taiga
• Online Access: https://doi.org/10.1186/s13071-020-04259-z; https://doaj.org/article/234ec4b3d89a47bfb1403d21fb45136b

Abstract Background Because ixodid ticks are vectors of zoonotic pathogens, including Borrelia, information of their abundance, seasonal variation in questing behaviour and pathogen prevalence is important for human health. As ticks are invading new areas northwards, information from these new areas are needed. Taiga tick (Ixodes persulcatus) populations have been recently found at Bothnian Bay, Finland. We assessed seasonal variation in questing abundance of ticks and their pathogen prevalence in coastal deciduous forests near the city of Oulu (latitudes 64–65°) in 2019. Methods We sampled ticks from May until September by cloth dragging 100 meters once a month at eight study sites. We calculated a density index (individuals/100 m2) to assess seasonal variation. Samples were screened for Borrelia burgdorferi (sensu lato) (including B. afzelii, B. garinii, B. burgdorferi (sensu stricto) and B. valaisana), Borrelia miyamotoi, Anaplasma phagocytophilum, Rickettsia spp., Neoehrlichia mikurensis, Francisella tularensis and Bartonella spp., Babesia spp. and for the tick-borne encephalitis virus. Results All except one nymph were identified as I. persulcatus. The number of questing adults showed a strong peak in May (median: 6.5 adults/100 m2), which is among the highest values reported in northern Europe, and potentially indicates a large population size. After May, the number of questing adults declined steadily with few adults still sampled in August. Nymphs were present from May until September. We found a striking prevalence of Borrelia spp. in adults (62%) and nymphs (40%), with B. garinii (51%) and B. afzelii (63%) being the most common species. In addition, we found that 26% of infected adults were coinfected with at least two Borrelia genospecies, mainly B. garinii and B. afzelii, which are associated with different host species. Conclusions The coastal forest environments at Bothnian Bay seem to provide favourable environments for I. persulcatus and the spread of Borrelia. High tick abundance, a low ...