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Identification of Suitable Areas for West Nile Virus Circulation in Tunisia
T Ben Hassine1, A Conte2, P Calistri2
1Centre National de Veille Zoosanitaire, Tunis, Tunisie.
Abstract:
West Nile virus (WNV) is a mosquito-transmitted Flavivirus belonging to the Japanese encephalitis antigenic complex of the Flaviviridae family. It is transmitted primarily by the bite of infected mosquitoes, particularly Culex spp. and Aedes/Ochlerotatus spp., which acquire the virus by feeding on viraemic birds. Humans, horses and other mammals are regarded as incidental or dead-end hosts. In the last decades, an increasing number of cases of WNV infection in horses and humans have been notified in the Mediterranean basin. In Tunisia, human cases of WNV-related meningoencephalitis were detected in 1997, 2003, 2007, 2010, 2011 and 2012. Based on the analysis of climatic and environmental conditions found in the locations where human cases have been reported in 2012, the aim of this study was to identify similar areas in Tunisia potentially at risk of disease occurrence. Data related to 85 neuroinvasive West Nile fever (WNF) human cases were georeferenced and a set of environmental and climatic variables (wetlands and humid areas, normalized difference vegetation index (NDVI), temperatures and elevation, migratory bird settlements) were used in the analysis. Areas, ecologically similar to those where human cases were detected, were identified using the Mahalanobis distance statistic. A leave-one-out cross-validation was performed to validate the sensitivity of the model, and 78 of 85 points were correctly classified.
Insights
West Nile virus (WNV) poses a growing risk in Tunisia. This study identified high-risk areas for WNV neuroinvasive disease by analyzing environmental factors associated with human cases.
Area of Science:
- Medical Entomology
- Epidemiology
- Environmental Science
Background:
- West Nile virus (WNV) is a mosquito-borne Flavivirus with increasing incidence in the Mediterranean basin.
- Tunisia has reported numerous human WNV-related meningoencephalitis cases since 1997.
- Understanding WNV transmission dynamics is crucial for public health interventions.
Purpose of the Study:
- To identify areas in Tunisia at risk for West Nile fever (WNF) occurrence.
- To analyze climatic and environmental factors linked to human WNV cases.
- To develop a predictive model for WNV risk assessment.
Main Methods:
- Georeferencing of 85 neuroinvasive West Nile fever (WNF) human cases.
- Analysis of environmental variables: wetlands, NDVI, temperature, elevation, and bird settlements.
- Application of Mahalanobis distance statistic to identify ecologically similar high-risk areas.
Main Results:
- Ecologically similar areas to those with reported human WNF cases were identified.
- A leave-one-out cross-validation model showed high sensitivity.
- The model correctly classified 78 out of 85 human case locations.
Conclusions:
- The study successfully identified potential WNV hotspots in Tunisia.
- Environmental and climatic factors are key indicators for WNV risk.
- This predictive approach can guide targeted surveillance and control strategies.
