Altitudinal Distribution, Seasonal Dynamics and Borrelia burgdorferi Sensu Lato Infections in Hard Ticks (Acari: Ixodidae) in Different Forest Communities in Inland Croatia

Abstract

Altitudinal distributions, population structures and seasonal dynamics of tick fauna at three localities in Continental Croatia (Medvednica and Papuk) and an alpine biogeographic region (Gorski Kotar) were studied. Sampling of questing ticks was performed twice a year (spring and autumn, from 2019 to 2021) at different altitudes (200, 400, 600, 800 and 1000 m above sea level) using the flagging method. In total, 2942 ticks (53.9% larvae, 40.1% nymphs, 6.0% adults) were sampled and 2937 (99.83%) were determined as Ixodes ricinus, 4 (0.14%) as Haemaphysalis concinna and 1 (0.03%) as Ixodes frontalis. Ixodes ricinus was the only species found at all altitudes and sampling sites. The highest tick abundance was recorded at higher altitudes (800–1000 m asl.) on Medvednica and in Gorski Kotar within mixed forests of European beech and European silver fir, while on Papuk most of the ticks were sampled at lower altitudes (200 m asl.) in Sessile oak forest. From 27 pools containing 305 ticks, 1 (3.7%) was positive for Borrelia burgdorferi sensu lato infection. Borrelia burgdorferi s.l. was detected in 20% (1/5) of the pools containing nymphs and adults collected in Gorski Kotar (600 and 800 m asl.). Sequencing of the ospA gene and phylogenetic analysis revealed the presence of the Borrelia burgdorferi sensu stricto genotype.

Seasonal Dynamics and Physiological Age of Ixodid Ticks Collected from Dogs

“…Our results demonstrated similar seasonal patterns in ticks found attached to dogs with those described for ticks collected from nature, especially for I. ricinus and two Dermacentor species. Numerous studies on seasonal dynamics of ixodid ticks collected from vegetation in the temperate climate regions indicate the presence of two population density peaks, in spring and autumn [47][48][49], although there is also evidence for a unimodal activity pattern in some countries [50]. I. ricinus and D. reticulatus are considered to be cold-resistant species in contrast to D. marginatus which is usually described as cold-sensitive and freeze-intolerant [38,41].…”

Current Status of Vector-Borne Diseases in Croatia: Challenges and Future Prospects

“…Records of ticks correlate with the number of reported human cases. Ixodes ricinus was recorded in localities in all three biogeographic regions (Mediterranean, Alpine, and Continental), and has been recorded in 207 localities covering the 159 fields on the UTM grid (Universal Transverse Mercator coordinate system) of Croatia [ 27 , 51 , 54 , 55 , 57 , 58 , 68 , 69 , 70 , 71 , 72 ]. Many different wild and domestic animals serve as hosts for I .…”

“…was detected in 3.7% of ticks collected in the continental region and 20% of ticks collected in Gorski Kotar. Sequencing of the ospA gene demonstrated the presence of the B. burgdorferi s.s. genotype [ 72 ].…”