Giuseppe
Emeritus
[Source: European Centre for Disease Prevention and Control (ECDC), full PDF document: (LINK). Excerpts.]
TECHNICAL REPORT
Environmental risk mapping: Aedes albopictus in Europe. Proof-of-concept study for the European Environment and Epidemiology Network
This report was commissioned by the European Centre for Disease Prevention and Control (ECDC), coordinated by Jonathan Suk and Jan Semenza, with input from Bertrand Sudre, Wim Van Bortel, Laurence Marrama and Herv? Zeller (all at ECDC), and produced by David Rogers and Willy Wint (University of Oxford, United Kingdom).
Suggested citation: European Centre for Disease Prevention and Control. Environmental risk mapping: Aedes albopictus in Europe. Stockholm: ECDC; 2013. Stockholm, August 2013 / ISBN 978-92-9193-449-2 / doi 10.2900/78239 / Catalogue number TQ-32-13-122-EN-C
Cover photo: John Beetham, Creative Commons-licensed content
? European Centre for Disease Prevention and Control, 2013
Reproduction is authorised, provided the source is acknowledged
Introduction
Scope and purpose
This report has been designed to discuss the usefulness of environmental risk mapping for public health. The report demonstrates the application of non-linear discriminant analysis (NLDA) to examine how the following question could be answered by environmental risk mapping: ?How might we study and monitor Aedes albopictus, in order to be better prepared for outbreaks of diseases vectored by this species in the future??
What is this document for?
This is a technical report published with the intent of informing readers about the ways in which the data contained in the ECDC European Environment and Epidemiology Network (E3) can be used for risk mapping of Ae. albopictus ? as well as infectious disease vectors more generally - in continental Europe. The specific example of risk mapping given in this report is non-linear discriminant analysis.
Who is this document for?
This document has been prepared for public health institutions and scientists experts dedicated to the control of vector-borne diseases. This report should be of particular relevance to those working with vector-borne diseases in EU Member States and neighbouring countries, but it may also be relevant to a broader international audience. It may also be of relevance to those tasked with establishing surveillance protocols for invasive mosquito species.
Why was it commissioned?
This project was commissioned in 2010 in order to provide insight into two streams of ECDC work. One was to support the development of European Environment and Epidemiology (E3) Network, and the other is ECDC work focused on emerging and vector-borne diseases.
The project was financed solely by the European Centre for Disease Prevention and Control (ECDC), and the project was undertaken by the University of Oxford, United Kingdom, in collaboration with ECDC technical staff.
1 * Background
Risk mapping with geospatial data is a rapidly growing area in public health. With the aim of facilitating information exchange on the risk mapping of infectious diseases in Europe, ECDC launched the European Environment and Epidemiology (E3) network in 2013. This network enables users to obtain the latest project results from ECDC and its partner organisations and provides access to hundreds of datasets relevant to the risk mapping of infectious diseases.
To evaluate and demonstrate the practice of risk mapping, this report describes the process involved in modelling the potential distribution of the Asian tiger mosquito (Ae. albopictus) in Europe. The main section describes the selected data sources, the formatting of environmental data, and the production of a series of risk maps. The discussion surveys the technical decisions made when producing risk maps, and the appendix provides a tutorial on risk mapping based upon non-linear discriminant analysis (NLDA).
Ae. albopictus, arrived in Europe in Albania in 1979, and then Italy in the early 1990s via trade in used tires1. Ae. albopictus is, today, principally present in the northwest Mediterranean basin (Figure 1)2. The expansion of the vector in Europe has been driven by global trade and travel between climatically similar regions3, and it has been speculated that future European expansion of Ae. albopictus could be further facilitated by climate change, as altered warming and precipitation patterns might increase the number of suitable niches for the vector4.
Irrespective of future climatic changes, a series of risk maps published by ECDC in 2012 suggest that Ae. albopictus has yet to fill its realisable niche in continental Europe5.
Ae. albopictus is a less effective epidemic dengue vector than Ae. aegypti 6, but in recent years it has nonetheless been responsible for transmitting both dengue and chikingunya fever in continental Europe, including over 200 laboratory-confirmed cases of chikungunya in Italy in 20077 and local dengue transmission in Croatia and France.
Due to its potential public health significance, there are currently numerous activities in Europe to consider the impact that changing climatic and environmental variables could have on the distribution of Ae. albopictus in Europe. Similarly, organisations responsible for public health and vector control will need to be able to interpret the results from such initiatives so as to inform vector surveillance activities8. In this report, the processes for producing risk maps based upon the data stored in the ECDC European Environment and Epidemiology network (E3) and using NLDA methodologies will be discussed, as will the implications of the resultant risk maps for public health initiatives, for example in the areas of monitoring and early warning.
(...)
Conclusion
In this handbook we have taken a risk map produced via the non-linear discriminate analysis methodology and interpreted it in several ways to show the potential for Ae. albopictus to spread further in Europe. These interpretations show the places that are likely to be suitable and the potential spread routes that the vector might use to reach such places. In turn these provide the potential for targeting monitoring resources as efficiently as possible, to check on the spread of this species in the near future.
It should be emphasised that all of these conclusions are based on models which may be wrong, and that there are multiple different possible approaches to risk mapping that have not been discussed here. Therefore a decent monitoring scheme should not only be positioned according to current predictions and be able to capture spread if the model is correct, but also be set up to test whether the model is correct in the first place. It can do so by sampling not only areas of predicted greatest suitability, but also areas of predicted greatest change in suitability. Thus model validation and application occur simultaneously. New records feed back into the modelling process progressively to improve the models locally.
Risk maps can indicate which sites are more likely for local transmission to occur. They are an increasingly important tool in public health, helping to address questions about the possible impact of climatic and environmental change on the potential distribution of vector-borne diseases, and on where vector- or diseasesurveillance initiatives might be most wisely implemented. ECDC intends to facilitate such activities through initiatives such as VBORNET and the E3 network.
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TECHNICAL REPORT
Environmental risk mapping: Aedes albopictus in Europe. Proof-of-concept study for the European Environment and Epidemiology Network
This report was commissioned by the European Centre for Disease Prevention and Control (ECDC), coordinated by Jonathan Suk and Jan Semenza, with input from Bertrand Sudre, Wim Van Bortel, Laurence Marrama and Herv? Zeller (all at ECDC), and produced by David Rogers and Willy Wint (University of Oxford, United Kingdom).
Suggested citation: European Centre for Disease Prevention and Control. Environmental risk mapping: Aedes albopictus in Europe. Stockholm: ECDC; 2013. Stockholm, August 2013 / ISBN 978-92-9193-449-2 / doi 10.2900/78239 / Catalogue number TQ-32-13-122-EN-C
Cover photo: John Beetham, Creative Commons-licensed content
? European Centre for Disease Prevention and Control, 2013
Reproduction is authorised, provided the source is acknowledged
Introduction
Scope and purpose
This report has been designed to discuss the usefulness of environmental risk mapping for public health. The report demonstrates the application of non-linear discriminant analysis (NLDA) to examine how the following question could be answered by environmental risk mapping: ?How might we study and monitor Aedes albopictus, in order to be better prepared for outbreaks of diseases vectored by this species in the future??
What is this document for?
This is a technical report published with the intent of informing readers about the ways in which the data contained in the ECDC European Environment and Epidemiology Network (E3) can be used for risk mapping of Ae. albopictus ? as well as infectious disease vectors more generally - in continental Europe. The specific example of risk mapping given in this report is non-linear discriminant analysis.
Who is this document for?
This document has been prepared for public health institutions and scientists experts dedicated to the control of vector-borne diseases. This report should be of particular relevance to those working with vector-borne diseases in EU Member States and neighbouring countries, but it may also be relevant to a broader international audience. It may also be of relevance to those tasked with establishing surveillance protocols for invasive mosquito species.
Why was it commissioned?
This project was commissioned in 2010 in order to provide insight into two streams of ECDC work. One was to support the development of European Environment and Epidemiology (E3) Network, and the other is ECDC work focused on emerging and vector-borne diseases.
The project was financed solely by the European Centre for Disease Prevention and Control (ECDC), and the project was undertaken by the University of Oxford, United Kingdom, in collaboration with ECDC technical staff.
1 * Background
Risk mapping with geospatial data is a rapidly growing area in public health. With the aim of facilitating information exchange on the risk mapping of infectious diseases in Europe, ECDC launched the European Environment and Epidemiology (E3) network in 2013. This network enables users to obtain the latest project results from ECDC and its partner organisations and provides access to hundreds of datasets relevant to the risk mapping of infectious diseases.
To evaluate and demonstrate the practice of risk mapping, this report describes the process involved in modelling the potential distribution of the Asian tiger mosquito (Ae. albopictus) in Europe. The main section describes the selected data sources, the formatting of environmental data, and the production of a series of risk maps. The discussion surveys the technical decisions made when producing risk maps, and the appendix provides a tutorial on risk mapping based upon non-linear discriminant analysis (NLDA).
Ae. albopictus, arrived in Europe in Albania in 1979, and then Italy in the early 1990s via trade in used tires1. Ae. albopictus is, today, principally present in the northwest Mediterranean basin (Figure 1)2. The expansion of the vector in Europe has been driven by global trade and travel between climatically similar regions3, and it has been speculated that future European expansion of Ae. albopictus could be further facilitated by climate change, as altered warming and precipitation patterns might increase the number of suitable niches for the vector4.
Irrespective of future climatic changes, a series of risk maps published by ECDC in 2012 suggest that Ae. albopictus has yet to fill its realisable niche in continental Europe5.
Ae. albopictus is a less effective epidemic dengue vector than Ae. aegypti 6, but in recent years it has nonetheless been responsible for transmitting both dengue and chikingunya fever in continental Europe, including over 200 laboratory-confirmed cases of chikungunya in Italy in 20077 and local dengue transmission in Croatia and France.
Due to its potential public health significance, there are currently numerous activities in Europe to consider the impact that changing climatic and environmental variables could have on the distribution of Ae. albopictus in Europe. Similarly, organisations responsible for public health and vector control will need to be able to interpret the results from such initiatives so as to inform vector surveillance activities8. In this report, the processes for producing risk maps based upon the data stored in the ECDC European Environment and Epidemiology network (E3) and using NLDA methodologies will be discussed, as will the implications of the resultant risk maps for public health initiatives, for example in the areas of monitoring and early warning.
(...)
Conclusion
In this handbook we have taken a risk map produced via the non-linear discriminate analysis methodology and interpreted it in several ways to show the potential for Ae. albopictus to spread further in Europe. These interpretations show the places that are likely to be suitable and the potential spread routes that the vector might use to reach such places. In turn these provide the potential for targeting monitoring resources as efficiently as possible, to check on the spread of this species in the near future.
It should be emphasised that all of these conclusions are based on models which may be wrong, and that there are multiple different possible approaches to risk mapping that have not been discussed here. Therefore a decent monitoring scheme should not only be positioned according to current predictions and be able to capture spread if the model is correct, but also be set up to test whether the model is correct in the first place. It can do so by sampling not only areas of predicted greatest suitability, but also areas of predicted greatest change in suitability. Thus model validation and application occur simultaneously. New records feed back into the modelling process progressively to improve the models locally.
Risk maps can indicate which sites are more likely for local transmission to occur. They are an increasingly important tool in public health, helping to address questions about the possible impact of climatic and environmental change on the potential distribution of vector-borne diseases, and on where vector- or diseasesurveillance initiatives might be most wisely implemented. ECDC intends to facilitate such activities through initiatives such as VBORNET and the E3 network.
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