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West Nile Virus: High Transmission Rate in North-Western European Mosquitoes Indicates Its Epidemic Potential and Warrants Increased Surveillance.

Fros JJ, Geertsema C, Vogels CB, Roosjen PP, Failloux AB, Vlak JM, Koenraadt CJ, Takken W, Pijlman GP - PLoS Negl Trop Dis (2015)

Bottom Line: We found that NWE mosquitoes are highly competent for both WNV lineages, with transmission rates up to 25%.Compared to NA mosquitoes, transmission rates for lineage 2 WNV were significantly elevated in NWE mosquitoes due to better virus dissemination from the midgut and a shorter extrinsic incubation time.This emphasizes the need for intensified surveillance of virus activity in current WNV disease-free regions and warrants increased awareness in clinics throughout Europe.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Virology, Wageningen University, Wageningen, The Netherlands.

ABSTRACT

Background: West Nile virus (WNV) is a highly pathogenic flavivirus transmitted by Culex spp. mosquitoes. In North America (NA), lineage 1 WNV caused the largest outbreak of neuroinvasive disease to date, while a novel pathogenic lineage 2 strain circulates in southern Europe. To estimate WNV lineage 2 epidemic potential it is paramount to know if mosquitoes from currently WNV-free areas can support further spread of this epidemic.

Methodology/principal findings: We assessed WNV vector competence of Culex pipiens mosquitoes originating from north-western Europe (NWE) in direct comparison with those from NA. We exposed mosquitoes to infectious blood meals of lineage 1 or 2 WNV and determined the infection and transmission rates. We explored reasons for vector competence differences by comparing intrathoracic injection versus blood meal infection, and we investigated the influence of temperature. We found that NWE mosquitoes are highly competent for both WNV lineages, with transmission rates up to 25%. Compared to NA mosquitoes, transmission rates for lineage 2 WNV were significantly elevated in NWE mosquitoes due to better virus dissemination from the midgut and a shorter extrinsic incubation time. WNV infection rates further increased with temperature increase.

Conclusions/significance: Our study provides experimental evidence to indicate markedly different risk levels between both continents for lineage 2 WNV transmission and suggests a degree of genotype-genotype specificity in the interaction between virus and vector. Our experiments with varying temperatures explain the current localized WNV activity in southern Europe, yet imply further epidemic spread throughout NWE during periods with favourable climatic conditions. This emphasizes the need for intensified surveillance of virus activity in current WNV disease-free regions and warrants increased awareness in clinics throughout Europe.

No MeSH data available.


Related in: MedlinePlus

Mean diurnal summer temperature correlates with European WNV outbreaks.Mean diurnal temperature during July-August of (A) 2011, (B) 2012 and (C) 2013. Dots represent human WNV cases reported in the respective year. (D) Scatter plot displays the mean temperature during July and August of the indicated year at each individual location with WNV activity. The mean temperatures and standard deviations are indicated.
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pntd.0003956.g006: Mean diurnal summer temperature correlates with European WNV outbreaks.Mean diurnal temperature during July-August of (A) 2011, (B) 2012 and (C) 2013. Dots represent human WNV cases reported in the respective year. (D) Scatter plot displays the mean temperature during July and August of the indicated year at each individual location with WNV activity. The mean temperatures and standard deviations are indicated.

Mentions: Comparison between the spatial arrangement of recent WNV outbreaks in Europe per annum and the corresponding mean temperature during peak transmission season strengthens this hypothesis by displaying a strong correlation between WNV outbreaks and the mean diurnal summer temperature throughout Europe (Fig 6A and 6B and 6C). The mean temperatures at which WNV outbreaks occurred in 2011, 2012 and 2013 were 24.6°C, 25.3°C, and 23.5°C, with standard deviations of 2.4°C, 2.7°C, and 2.1°C, respectively (Fig 6D). Together, the mean temperatures at the respective locations of individual outbreaks give an indication of the average summer temperatures at which there is an elevated risk for WNV activity.


West Nile Virus: High Transmission Rate in North-Western European Mosquitoes Indicates Its Epidemic Potential and Warrants Increased Surveillance.

Fros JJ, Geertsema C, Vogels CB, Roosjen PP, Failloux AB, Vlak JM, Koenraadt CJ, Takken W, Pijlman GP - PLoS Negl Trop Dis (2015)

Mean diurnal summer temperature correlates with European WNV outbreaks.Mean diurnal temperature during July-August of (A) 2011, (B) 2012 and (C) 2013. Dots represent human WNV cases reported in the respective year. (D) Scatter plot displays the mean temperature during July and August of the indicated year at each individual location with WNV activity. The mean temperatures and standard deviations are indicated.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4520649&req=5

pntd.0003956.g006: Mean diurnal summer temperature correlates with European WNV outbreaks.Mean diurnal temperature during July-August of (A) 2011, (B) 2012 and (C) 2013. Dots represent human WNV cases reported in the respective year. (D) Scatter plot displays the mean temperature during July and August of the indicated year at each individual location with WNV activity. The mean temperatures and standard deviations are indicated.
Mentions: Comparison between the spatial arrangement of recent WNV outbreaks in Europe per annum and the corresponding mean temperature during peak transmission season strengthens this hypothesis by displaying a strong correlation between WNV outbreaks and the mean diurnal summer temperature throughout Europe (Fig 6A and 6B and 6C). The mean temperatures at which WNV outbreaks occurred in 2011, 2012 and 2013 were 24.6°C, 25.3°C, and 23.5°C, with standard deviations of 2.4°C, 2.7°C, and 2.1°C, respectively (Fig 6D). Together, the mean temperatures at the respective locations of individual outbreaks give an indication of the average summer temperatures at which there is an elevated risk for WNV activity.

Bottom Line: We found that NWE mosquitoes are highly competent for both WNV lineages, with transmission rates up to 25%.Compared to NA mosquitoes, transmission rates for lineage 2 WNV were significantly elevated in NWE mosquitoes due to better virus dissemination from the midgut and a shorter extrinsic incubation time.This emphasizes the need for intensified surveillance of virus activity in current WNV disease-free regions and warrants increased awareness in clinics throughout Europe.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Virology, Wageningen University, Wageningen, The Netherlands.

ABSTRACT

Background: West Nile virus (WNV) is a highly pathogenic flavivirus transmitted by Culex spp. mosquitoes. In North America (NA), lineage 1 WNV caused the largest outbreak of neuroinvasive disease to date, while a novel pathogenic lineage 2 strain circulates in southern Europe. To estimate WNV lineage 2 epidemic potential it is paramount to know if mosquitoes from currently WNV-free areas can support further spread of this epidemic.

Methodology/principal findings: We assessed WNV vector competence of Culex pipiens mosquitoes originating from north-western Europe (NWE) in direct comparison with those from NA. We exposed mosquitoes to infectious blood meals of lineage 1 or 2 WNV and determined the infection and transmission rates. We explored reasons for vector competence differences by comparing intrathoracic injection versus blood meal infection, and we investigated the influence of temperature. We found that NWE mosquitoes are highly competent for both WNV lineages, with transmission rates up to 25%. Compared to NA mosquitoes, transmission rates for lineage 2 WNV were significantly elevated in NWE mosquitoes due to better virus dissemination from the midgut and a shorter extrinsic incubation time. WNV infection rates further increased with temperature increase.

Conclusions/significance: Our study provides experimental evidence to indicate markedly different risk levels between both continents for lineage 2 WNV transmission and suggests a degree of genotype-genotype specificity in the interaction between virus and vector. Our experiments with varying temperatures explain the current localized WNV activity in southern Europe, yet imply further epidemic spread throughout NWE during periods with favourable climatic conditions. This emphasizes the need for intensified surveillance of virus activity in current WNV disease-free regions and warrants increased awareness in clinics throughout Europe.

No MeSH data available.


Related in: MedlinePlus