Evaluating the Risk for Usutu virus circulation in Europe: Comparison of Environmental Niche Models and Epidemiological Models

Yanchao Cheng1, Nils Tjaden1, Anja Jaeschke1, Renke Lühken2, Ute Ziegler3, Stephanie Thomas1, Carl Beierkuhnlein1
1 Department of Biogeography, University of Bayreuth, Universitätsstr. 30, 95447 Bayreuth, Germany
2 Bernhard Nocht Institute for Tropical Medicine, World Health Organization Collaborating Centre for Arbovirus and Hemorrhagic Fever Reference and Research, Hamburg, Germany
3 Friedrich-Loeffler-Institut, Institute of Novel and Emerging Infectious Diseases, Südufer 10, 17493 Greifswald – Insel Riems

O 3.1 in Tracking Spatial Patterns: From Mosquitos to Biomes

11.10.2018, 14:00-14:15, H36, NW III

Introduction

Usutu virus (USUV) is a mosquito-borne flavivirus, reported in many countries of Africa and Europe, with an increasing spatial distribution and host range. Recent outbreaks leading to regional declines of European common blackbird (Turdus merula) populations and a rising number of human cases emphasize the need for increased awareness and spatial risk assessment.

Material and Methods

Modelling approaches in ecology and epidemiology differ substantially in their algorithms, potentially resulting in diverging model outputs. Therefore, we implemented a parallel approach incorporating two commonly applied modelling techniques: 1) Maxent, a correlation-based environmental niche model and 2) a mechanistic epidemiological susceptible-exposed-infected-removed (SEIR) model.

Across Europe, surveillance data of USUV-positive birds from 2003 - 2016 was acquired to train the environmental niche model and to serve as test cases for the SEIR model. The SEIR model is mainly driven by daily mean temperature and calculates the basic reproduction number R0. The environmental niche model was run with long-term bio-climatic variables derived from the same source.

Results

Large areas across Europe are currently suitable for USUV transmission. Both models show patterns of high risk for USUV in parts of France, in the Pannonian Basin as well as northern Italy. The environmental niche model depicts the current situation better, but with USUV still being in an invasive stage there is a chance for under-estimation of risk. High R0 values predicted by the SEIR model in areas without evidence for real-life transmission suggest that it may tend towards over-estimation of risk.

Conclusions

The results from our parallel-model approach highlight that relying on a single model for assessing vector-borne disease risk may lead to incomplete conclusions. Utilizing different modelling approaches is thus crucial for risk-assessment of under-studied emerging pathogens like USUV. 

Potential geographic distribution of USUV in Europe, projected by Maxent and SEIR model
Potential geographic distribution of USUV in Europe, projected by Maxent and SEIR model



Keywords: Usutu, Maxent, SEIR, vector-borne disease, risk map, Europe, basic reproduction number, R0, ENM

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