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Ecological Niche Modeling to Estimate the Distribution of Japanese Encephalitis Virus in Asia
Robin H. Miller1*, Penny Masuoka1, Terry A. Klein2, Heung-Chul Kim3, Todd Somer4, John Grieco1
1 Department of Preventive Medicine and Biometrics, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America, 2 65th Medical Brigade/USAMEDDACKorea, Unit 15281, Force Health Protection and Preventive Medicine, Yongsan Army Garrison, Seoul, Republic of Korea, 3 168th Multifunctional Medical Battalion, 65th Medical Brigade, Unit 15247, 5th Medical Detachment, Yongsan Army Garrison, Seoul, Republic of Korea, 4 NST, National Geospatial-Intelligence Agency, Fort Detrick, Maryland, United States of America
Abstract
Background
Culex tritaeniorhynchus is the primary vector of Japanese encephalitis virus (JEV), a leading cause of encephalitis in Asia. JEV is transmitted in an enzootic cycle involving large wading birds as the reservoirs and swine as amplifying hosts. The development of a JEV vaccine reduced the number of JE cases in regions with comprehensive childhood vaccination programs, such as in Japan and the Republic of Korea. However, the lack of vaccine programs or insufficient coverage of populations in other endemic countries leaves many people susceptible to JEV. The aim of this study was to predict the distribution of Culex tritaeniorhynchus using ecological niche modeling.
Methods/Principal Findings
An ecological niche model was constructed using the Maxent program to map the areas with suitable environmental conditions for the Cx. tritaeniorhynchus vector. Program input consisted of environmental data (temperature, elevation, rainfall) and known locations of vector presence resulting from an extensive literature search and records from MosquitoMap. The statistically significant Maxent model of the estimated probability of Cx. tritaeniorhynchus presence showed that the mean temperatures of the wettest quarter had the greatest impact on the model. Further, the majority of human Japanese encephalitis (JE) cases were located in regions with higher estimated probability of Cx. tritaeniorhynchus presence.
Conclusions/Significance
Our ecological niche model of the estimated probability of Cx. tritaeniorhynchus presence provides a framework for better allocation of vector control resources, particularly in locations where JEV vaccinations are unavailable. Furthermore, this model provides estimates of vector probability that could improve vector surveillance programs and JE control efforts.
Author Summary
Japanese encephalitis virus (JEV) is transmitted predominately by the mosquito, Culex tritaeniorhynchus. The primary reservoirs of the virus are wading birds, with swine serving as amplifying hosts. Despite the development of a JEV vaccine, people remain unvaccinated in endemic countries and are susceptible to JEV infection. The distribution of the JEV vector(s) provides essential information for preventive measures. This study used an ecological niche modeling program to predict the distribution of Cx. tritaeniorhynchus based on collection records and environmental maps (climate, land cover, and elevation). The model showed that the mean temperatures of the wettest quarter had the greatest impact on the model. Of the 25 countries endemic for Japanese encephalitis (JE) endemic countries, seven possessed greater than 50% land area with an estimated high probability of Cx. tritaeniorhynchus presence. Our model provides a useful tool for JEV surveillance programs that focus on vector control strategies.
Citation: Miller RH, Masuoka P, Klein TA, Kim H-C, Somer T, et al. (2012) Ecological Niche Modeling to Estimate the Distribution of Japanese Encephalitis Virus in Asia. PLoS Negl Trop Dis 6(6): e1678. doi:10.1371/journal.pntd.0001678
Editor: Assaf Anyamba, NASA Goddard Space Flight Center, United States of America
Received: January 17, 2012; Accepted: April 25, 2012; Published: June 19, 2012
This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.
Funding: This project was funded by the Armed Forces Health Surveillance Center, Division of Global Emerging Infections Surveillance & Response System (GEIS) Operations (http://afhsc.mil/geis), grant: C0648_12_MH. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
* E-mail: robin.miller@usuhs.edu
Full paper available at; http://www.plosntds.org/article/info...l.pntd.0001678
Robin H. Miller1*, Penny Masuoka1, Terry A. Klein2, Heung-Chul Kim3, Todd Somer4, John Grieco1
1 Department of Preventive Medicine and Biometrics, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America, 2 65th Medical Brigade/USAMEDDACKorea, Unit 15281, Force Health Protection and Preventive Medicine, Yongsan Army Garrison, Seoul, Republic of Korea, 3 168th Multifunctional Medical Battalion, 65th Medical Brigade, Unit 15247, 5th Medical Detachment, Yongsan Army Garrison, Seoul, Republic of Korea, 4 NST, National Geospatial-Intelligence Agency, Fort Detrick, Maryland, United States of America
Abstract
Background
Culex tritaeniorhynchus is the primary vector of Japanese encephalitis virus (JEV), a leading cause of encephalitis in Asia. JEV is transmitted in an enzootic cycle involving large wading birds as the reservoirs and swine as amplifying hosts. The development of a JEV vaccine reduced the number of JE cases in regions with comprehensive childhood vaccination programs, such as in Japan and the Republic of Korea. However, the lack of vaccine programs or insufficient coverage of populations in other endemic countries leaves many people susceptible to JEV. The aim of this study was to predict the distribution of Culex tritaeniorhynchus using ecological niche modeling.
Methods/Principal Findings
An ecological niche model was constructed using the Maxent program to map the areas with suitable environmental conditions for the Cx. tritaeniorhynchus vector. Program input consisted of environmental data (temperature, elevation, rainfall) and known locations of vector presence resulting from an extensive literature search and records from MosquitoMap. The statistically significant Maxent model of the estimated probability of Cx. tritaeniorhynchus presence showed that the mean temperatures of the wettest quarter had the greatest impact on the model. Further, the majority of human Japanese encephalitis (JE) cases were located in regions with higher estimated probability of Cx. tritaeniorhynchus presence.
Conclusions/Significance
Our ecological niche model of the estimated probability of Cx. tritaeniorhynchus presence provides a framework for better allocation of vector control resources, particularly in locations where JEV vaccinations are unavailable. Furthermore, this model provides estimates of vector probability that could improve vector surveillance programs and JE control efforts.
Author Summary
Japanese encephalitis virus (JEV) is transmitted predominately by the mosquito, Culex tritaeniorhynchus. The primary reservoirs of the virus are wading birds, with swine serving as amplifying hosts. Despite the development of a JEV vaccine, people remain unvaccinated in endemic countries and are susceptible to JEV infection. The distribution of the JEV vector(s) provides essential information for preventive measures. This study used an ecological niche modeling program to predict the distribution of Cx. tritaeniorhynchus based on collection records and environmental maps (climate, land cover, and elevation). The model showed that the mean temperatures of the wettest quarter had the greatest impact on the model. Of the 25 countries endemic for Japanese encephalitis (JE) endemic countries, seven possessed greater than 50% land area with an estimated high probability of Cx. tritaeniorhynchus presence. Our model provides a useful tool for JEV surveillance programs that focus on vector control strategies.
Citation: Miller RH, Masuoka P, Klein TA, Kim H-C, Somer T, et al. (2012) Ecological Niche Modeling to Estimate the Distribution of Japanese Encephalitis Virus in Asia. PLoS Negl Trop Dis 6(6): e1678. doi:10.1371/journal.pntd.0001678
Editor: Assaf Anyamba, NASA Goddard Space Flight Center, United States of America
Received: January 17, 2012; Accepted: April 25, 2012; Published: June 19, 2012
This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.
Funding: This project was funded by the Armed Forces Health Surveillance Center, Division of Global Emerging Infections Surveillance & Response System (GEIS) Operations (http://afhsc.mil/geis), grant: C0648_12_MH. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
* E-mail: robin.miller@usuhs.edu
Full paper available at; http://www.plosntds.org/article/info...l.pntd.0001678