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Ecology of West Nile virus across four European countries: review of weather profiles, vector population dynamics and vector control response
Chaskopoulou et al. Parasites & Vectors
Ecology of West Nile virus across four European countries: review of weather profiles, vector population dynamics and vector control response
Alexandra Chaskopoulou
Gregory L'Ambert
Dusan Petric
Romeo Bellini
Marija Zgomba
Thomas A. Groen
Laurence Marrama
Dominique J. Bicout
West Nile virus (WNV) represents a serious burden to human and animal health because of its capacity to cause unforeseen and large epidemics. Until 2004, only lineage 1 and 3 WNV strains had been found in Europe. Lineage 2 strains were initially isolated in 2004 (Hungary) and in 2008 (Austria) and for the first time caused a major WNV epidemic in 2010 in Greece with 262 clinical human cases and 35 fatalities. Since then, WNV lineage 2 outbreaks have been reported in several European countries including Italy, Serbia and Greece. Understanding the interaction of ecological factors that affect WNV transmission is crucial for preventing or decreasing the impact of future epidemics. The synchronous co-occurrence of competent mosquito vectors, virus, bird reservoir hosts, and susceptible humans is necessary for the initiation and propagation of an epidemic. Weather is the key abiotic factor influencing the life-cycles of the mosquito vector, the virus, the reservoir hosts and the interactions between them. The purpose of this paper is to review and compare mosquito population dynamics, and weather conditions, in three ecologically different contexts (urban/semi-urban, rural/agricultural, natural) across four European countries (Italy, France, Serbia, Greece) with a history of WNV outbreaks. Local control strategies will be described as well. Improving our understanding of WNV ecology is a prerequisite step for appraising and optimizing vector control strategies in Europe with the ultimate goal to minimize the probability of WNV infection.
West Nile virus; West Nile fever; Europe; Ecology; Control; Modelling
Background
West Nile virus (WNV) is an arthropod-borne pathogen
transmitted by mosquitoes that was first isolated in 1937
from the blood of a febrile woman in the West Nile
district of Uganda [
1
]. It was in 1958 when WNV was
detected in Europe from a patient in Albania and since then
has been repeatedly detected in the continent with human
and equine infections reported from many countries [
2
].
WNV infection represents a serious burden to human
and animal health because of the capacity of the virus to
cause unforeseen and large epidemics. Until 2004, only
lineage 1 and 3 WNV strains had been found in Europe.
Lineage 2 strains were initially isolated in 2004 (Hungary)
and in 2008 (Austria) and for the first time caused a major
epidemic of WNV infection in 2010 in Greece with 262
clinical human cases and 35 fatalities [
3
]. Since then,
outbreaks involving WNV lineage 2 have been reported in
several European countries including Italy, Serbia and Greece.
In nature the virus circulates in a sylvatic/rural cycle,
between birds and ornithophilic mosquitoes particularly
members of the genus Culex, and under certain
environmental conditions it spills over to human
settlements where it infects humans and equines causing large
epidemics. Precipitation, temperature and landscape use/
management are among the most important environmental
parameters that influence the life-cycles of the mosquito,
the virus, the amplifying and accidental hosts and the
interactions between them [
4
]. Because of these features,
outbreaks of WNV infection are highly sporadic and focal in
nature exhibiting high variability in their development and
incidence across different regions [
5
]. Studies are needed at
local levels that compare different habitats and mosquito/
vertebrate communities to determine how environmental
parameters influence vector population and disease
transmission dynamics and how mosquito control interventions
may alter these dynamics.
To mitigate WNV transmission risk to humans and
animals, European governments have been investing
significant resources in medical and vector control
interventions [
6
]. The majority of these efforts are reactive
emergency response measures to reported human cases
with unclear effect on the containment of the epidemic
[
3
]. There is only a limited number of studies about the
impact of vector control applications on the propagation
of epidemics of WNV infection and most of them have
been conducted in North America [
7–9
]. There is a need
to build on our understanding of vector control
practices against WNV vectors in Europe and analyze local
experiences on the prevention and control of outbreaks
in order to optimize the use of resources while
minimizing the probability of WNV infection [
10
].
Vector Control Analysis (VeCA) is an ECDC-funded
vector control research project aiming to increase our
knowledge on WNV vector ecology and control in Europe.
The project utilizes field data collected from three
ecologically different study environments, urban (...truncated)