Climate change influences on the potential geographic distribution of the disease vector tick Ixodes ricinus.

Abdelghafar A Alkishe,A Townsend Peterson,Abdallah M Samy

doi:10.1371/journal.pone.0189092

Abstract

BackgroundIxodes ricinus is a species of hard tick that transmits several important diseases in Europe and North Africa, including Lyme borreliosis and tick-borne encephalitis. Climate change is affecting the geographic distributions and abundances of arthropod vectors, which in turn influence the geographic distribution and epidemiology of associated vector-borne diseases. To date, few studies have investigated effects of climate change on the spatial distribution of I. ricinus at continental extents. Here, we assessed the potential distribution of I. ricinus under current and future climate conditions to understand how climate change will influence the geographic distribution of this important tick vector in coming decades.MethodWe used ecological niche modeling to estimate the geographic distribution of I. ricinus with respect to current climate, and then assessed its future potential distribution under different climate change scenarios. This approach integrates occurrence records of I. ricinus with six relevant environmental variables over a continental extent that includes Europe, North Africa, and the Middle East. Future projections were based on climate data from 17 general circulation models (GCMs) under 2 representative concentration pathway emissions scenarios (RCPs), for the years 2050 and 2070.ResultThe present and future potential distributions of I. ricinus showed broad overlap across most of western and central Europe, and in more narrow zones in eastern and northern Europe, and North Africa. Potential expansions were observed in northern and eastern Europe. These results indicate that I. ricinus populations could emerge in areas in which they are currently lacking, posing increased risks to human health in those areas. However, the future of I. ricinus ticks in some important regions such the Mediterranean was unclear owing to high uncertainty in model predictions.

Highlights

Ixodes ricinus is the most common arthropod vector of human disease in Europe and nearby regions [1]
Calibrating models for I. ricinus based on the 5 subgroups of occurrence points yielded predictions that gave area under the curve (AUC) ratios above null expectations in all five partial ROC analyses (P < 0.001; S2 File)
Models based on present-day conditions revealed areas with high suitability for I. ricinus across Central and Western Europe including the countries of Great Britain, France, Germany, Belgium, the Netherlands, Greece, and Italy

Summary

Introduction

Ixodes ricinus is the most common arthropod vector of human disease in Europe and nearby regions [1]. Ixodes ricinus transmits a wide variety of tick-borne pathogens, including the spirochete bacteria of the Borrelia burgdorferi sensu lato (sl) species complex and the tick-borne encephalitis virus. These pathogens are transmitted to humans mostly by bites of immature nymphs, which are more abundant, smaller and harder to notice than adult ticks [3]. TBE occurs in eastern, western, and central Europe, as well as in Russia [5, 6] Active surveillance of both diseases in Europe indicates a need to study the distributional ecology of their vector, I. ricinus. We assessed the potential distribution of I. ricinus under current and future climate conditions to understand how climate change will influence the geographic distribution of this important tick vector in coming decades

Methods

Results

Conclusion