Climate and environmental change drives Ixodes ricinus geographical expansion at the northern range margin

Abstract

BackgroundGlobal environmental change is causing spatial and temporal shifts in the distribution of species and the associated diseases of humans, domesticated animals and wildlife. In the on-going debate on the influence of climate change on vectors and vector-borne diseases, there is a lack of a comprehensive interdisciplinary multi-factorial approach utilizing high quality spatial and temporal data.MethodsWe explored biotic and abiotic factors associated with the latitudinal and altitudinal shifts in the distribution of Ixodes ricinus observed during the last three decades in Norway using antibodies against Anaplasma phagocytophilum in sheep as indicators for tick presence. Samples obtained from 2963 sheep from 90 farms in 3 ecologically different districts during 1978 – 2008 were analysed. We modelled the presence of antibodies against A. phagocytophilum to climatic-, environmental and demographic variables, and abundance of wild cervids and domestic animals, using mixed effect logistic regressions.ResultsSignificant predictors were large diurnal fluctuations in ground surface temperature, spring precipitation, duration of snow cover, abundance of red deer and farm animals and bush encroachment/ecotones. The length of the growth season, mean temperature and the abundance of roe deer were not significant in the model.ConclusionsOur results highlight the need to consider climatic variables year-round to disentangle important seasonal variation, climatic threshold changes, climate variability and to consider the broader environmental change, including abiotic and biotic factors. The results offer novel insight in how tick and tick-borne disease distribution might be modified by future climate and environmental change.

Modelling the seasonality of Lyme disease risk and the potential impacts of a warming climate within the heterogeneous landscapes of Scotland

“…The ability of two other variables (annual mean temperature and deer density) to act as a proxy of disease risk was also analysed, but their explanatory capability may only be satisfactory within certain intervals: the DIN was predicted to be negatively associated with annual temperature between 68C and 108C and positively with deer density between 15 and 22 head km 22 . Climate warming has been found to accelerate tick phenology [49] and contribute to their geographical expansion [54]. Our model predicted similar overall conclusions from applying scenarios of regional warming to the Lyme disease model.…”

Ecology and Epidemiology of Lyme Borreliosis

“…3,16,17 This increase is secondary to a variety of influences including climate change resulting in the expansion of the Ixodes tick territory including expansion to higher elevations, changes in small mammal and deer populations, changes in deforestation and development, and improved reporting and awareness of disease. 3,8,[18][19][20][21] Some studies have suggested increased B burgdorferi virulence may be contributing to global spread; however, studies looking at B burgdorferi populations in the United States have been unable to validate this. 21,22 …”

Attachment site selection of life stages of Ixodes ricinus ticks on a main large host in Europe, the red deer ( Cervus elaphus )

“…The distribution of ticks and its associated diseases is increasing in many areas [2,3], and understanding the mechanisms provide potential for mitigation measures. Some of these increases can be linked to warmer climate, at least at higher elevation and latitudes [4].…”