Mapping the potential distributions of etiological agent, vectors, and reservoirs of Japanese Encephalitis in Asia and Australia.

Japanese encephalitis virus (JEV) is a substantial cause of viral encephalitis, morbidity, and mortality in South-East Asia and the Western Pacific. World Health Organization recognized Japanese Encephalitis (JE) as a public health priority in demands to initiate active vaccination programs. Recently, the geographic distribution of JEV has apparently expanded into other areas in the Pacific islands and northern Australia; however, major gaps exist in knowledge in regard to its current distribution. Here, we mapped the potential distribution of mosquito vectors of JEV (Culex tritaeniorhynchus, Cx. pseudovishnui, Cx. vishnui, Cx. fuscocephala, Cx. gelidus), and reservoirs (Egretta garzetta, E. intermedia, Nycticorax nycticorax) based on ecological niche modeling approach. Ecological niche models predicted all species to occur across Central, South and South East Asia; however, Cx. tritaeniorhynchus, E. garzetta, E. intermedia, and N. nycticorax had broader potential distributions extending west to parts of the Arabian Peninsula. All predictions were robust and significantly better than random (P < 0.001). We also tested the JEV prediction based on 4335 additional independent human case records collected by the Chinese Information System for Disease Control and Prevention (CISDCP); 4075 cases were successfully predicted by the model (P < 0.001). Finally, we tested the ecological niche similarity among JEV, vector, and reservoir species and could not reject any of the null hypotheses of niche similarity in all combination pairs.

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

BACKGROUND: Ixodes 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. METHOD: We 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. RESULT: The 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.