Predicting habitat suitability for Ixodes ricinus and Ixodes persulcatus ticks in Finland

• Published in: Parasites & Vectors
• Main Authors: Uusitalo, Ruut, Siljander, Mika, Linden, Andreas, Sormunen, Jani J., Aalto, Juha, Hendrickx, Guy, Kallio, Eva, Vajda, Andrea, Gregow, Hilppa, Henttonen, Heikki, Marsboom, Cedric, Korhonen, Essi M., Sironen, Tarja, Pellikka, Petri, Vapalahti, Olli
• Other Authors: Department of Virology, Department of Geosciences and Geography, Medicum, Veterinary Biosciences, Faculty Common Matters (Faculty of Medicine), Helsinki One Health (HOH), Viral Zoonosis Research Unit, HUSLAB, Emerging Infections Research Group, Helsinki Institute of Sustainability Science (HELSUS), Institute for Atmospheric and Earth System Research (INAR), Veterinary Microbiology and Epidemiology, Olli Pekka Vapalahti / Principal Investigator
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2022
• Subjects: Ixodes ricinus; Ixodes persulcatus; Species distribution modelling; Ensemble prediction; Tick-borne pathogen; Borreliaburgdorferi sensu lato; IXODES-RICINUS TICKS; BORNE ENCEPHALITIS-VIRUS; BURGDORFERI SENSU-LATO; POPULATION-DYNAMICS; QUESTING ACTIVITY; ABUNDANCE; IXODIDAE; BORRELIA; VECTOR; CLIMATE; 11831 Plant biology; 11832 Microbiology and virology; 1171 Geosciences; mountain hare
• Online Access: http://hdl.handle.net/10138/349735

Background Ticks are responsible for transmitting several notable pathogens worldwide. Finland lies in a zone where two human-biting tick species co-occur: Ixodesricinus and Ixodespersulcatus. Tick densities have increased in boreal regions worldwide during past decades, and tick-borne pathogens have been identified as one of the major threats to public health in the face of climate change. Methods We used species distribution modelling techniques to predict the distributions of I.ricinus and I.persulcatus, using aggregated historical data from 2014 to 2020 and new tick occurrence data from 2021. By aiming to fill the gaps in tick occurrence data, we created a new sampling strategy across Finland. We also screened for tick-borne encephalitis virus (TBEV) and Borrelia from the newly collected ticks. Climate, land use and vegetation data, and population densities of the tick hosts were used in various combinations on four data sets to estimate tick species' distributions across mainland Finland with a 1-km resolution. Results In the 2021 survey, 89 new locations were sampled of which 25 new presences and 63 absences were found for I.ricinus and one new presence and 88 absences for I.persulcatus. A total of 502 ticks were collected and analysed; no ticks were positive for TBEV, while 56 (47%) of the 120 pools, including adult, nymph, and larva pools, were positive for Borrelia (minimum infection rate 11.2%, respectively). Our prediction results demonstrate that two combined predictor data sets based on ensemble mean models yielded the highest predictive accuracy for both I.ricinus (AUC = 0.91, 0.94) and I.persulcatus (AUC = 0.93, 0.96). The suitable habitats for I.ricinus were determined by higher relative humidity, air temperature, precipitation sum, and middle-infrared reflectance levels and higher densities of white-tailed deer, European hare, and red fox. For I.persulcatus, locations with greater precipitation and air temperature and higher white-tailed deer, roe deer, and mountain hare densities were ...