Abstract
BackgroundClimate change can affect the activity and distribution of species, including pathogens and parasites. The densities and distribution range of the sheep tick (Ixodes ricinus) and it’s transmitted pathogens appears to be increasing. Thus, a better understanding of questing tick densities in relation to climate and weather conditions is urgently needed. The aim of this study was to test predictions regarding the temporal pattern of questing tick densities at two different elevations in Norway. We predict that questing tick densities will decrease with increasing elevations and increase with increasing temperatures, but predict that humidity levels will rarely affect ticks in this northern, coastal climate with high humidity.MethodsWe described the temporal pattern of questing tick densities at ~100 and ~400 m a.s.l. along twelve transects in the coastal region of Norway. We used the cloth lure method at 14-day intervals during the snow-free season to count ticks in two consecutive years in 20 m2 plots. We linked the temporal pattern of questing tick densities to local measurements of the prevailing weather.ResultsThe questing tick densities were much higher and the season was longer at ~100 compared to at ~400 m a.s.l. There was a prominent spring peak in both years and a smaller autumn peak in one year at ~100 m a.s.l.; but no marked peak at ~400 m a.s.l. Tick densities correlated positively with temperature, from low densities <5°C, then increasing and levelling off >15-17°C. We found no evidence for reduced questing densities during the driest conditions measured.ConclusionsTick questing densities differed even locally linked to elevation (on the same hillside, a few kilometers apart). The tick densities were strongly hampered by low temperatures that limited the duration of the questing seasons, whereas the humidity appeared not to be a limiting factor under the humid conditions at our study site. We expect rising global temperatures to increase tick densities and lead to a transition from a short questing season with low densities in the current cold and sub-optimal tick habitats, to longer questing seasons with overall higher densities and a marked spring peak.
Highlights
Climate change can affect the activity and distribution of species, including pathogens and parasites
Ticks were recorded at high elevation on the same day as the first flagging in 2012 (May 23rd), and the last tick was recorded on October 10th, 13 days before flagging ceased
Three ticks were found at temperatures
Summary
Climate change can affect the activity and distribution of species, including pathogens and parasites. The effects of climate change on vector-borne diseases may be difficult to predict because of the complexity of their transmission systems [5,6]. The changes in such systems are important for both animal and human welfare because of the zoonotic nature of many vector-borne diseases, including malaria [7], Lyme disease [8], and tick-borne encephalitis [9,10]. It is important to understand how the vector is affected by the prevailing weather patterns in different climatic regions
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