Ecology of West Nile virus across four European countries: review of weather profiles, vector population dynamics and vector control response

Parasites & Vectors, Sep 2016

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.

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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)


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Alexandra Chaskopoulou, Gregory L’Ambert, Dusan Petric, Romeo Bellini, Marija Zgomba, Thomas Groen, Laurence Marrama, Dominique Bicout. Ecology of West Nile virus across four European countries: review of weather profiles, vector population dynamics and vector control response, Parasites & Vectors, 2016, pp. 482, 9, DOI: 10.1186/s13071-016-1736-6