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Eurosurveillance, Volume 21, Issue 39, 29 September 2016
Rapid communication
We assessed the ability of a French population of Aedes albopictus to transmit yellow fever virus (YFV). Batches of 30 to 40 female mosquitoes were analysed at 7, 14 and 21 days post-exposure (dpe). Bodies, heads and saliva were screened for YFV. Infectious viral particles were detected in bodies and heads at 7, 14 and 21 dpe whereas the virus was found in saliva only from 14 dpe. Our results showed that Ae. albopictus can potentially transmit YFV.
The establishment of a local YF transmission cycle outside endemic areas is related to competent Aedes mosquitoes, active all year long in tropical regions and during the warm period in temperate areas. The mosquito species Ae. albopictus is present in 20 European countries [18], and a strain of this species (Houston) in the United States has been previously reported to be a competent vector for YFV [19]. Hence travellers returning to Europe from countries where a YF outbreak is occurring could be a source of infection for local strains of Ae. albopictus. We therefore assessed the competence of Ae. albopictus mosquitoes from the south of France for a West African strain of YFV.
The virus was detected at 14 dpe in saliva of the French Ae. albopictus mosquitoes at a rate of two mosquitoes in 40, a relatively low TE. While this is reassuring, a low vector competence can on the other hand contribute to select for virulent virus strains capable of eliciting high viraemia in humans [20] and causing more severe clinical symptoms [21]. Moreover although our results point to a low TR (2/9) for YFV, the anthropophilic nature of Ae. albopictus mosquitoes and their high densities in urban areas may allow them to be a vector of YFV.
Concerning the virus strain assessed in this study, the West African YFV strain should not be very genetically distant from the other six genotypes with ca 9% amino-acid divergence between strains, indicating genetic stability of YFV genotypes [7]. However, small genetic changes in the viral genome may change the vector competence.
As Europe has faced YF outbreaks in the past [22], the last being recorded in Gibraltar in 1905, a risk of importation of YF into Europe is to be considered. Although so far there have been hardly any reports from Europe of imported YF cases, many imported cases of chikungunya and dengue, two other arboviral diseases, have been documented [23].
If YF follows the same path as dengue and chikungunya, which have a greater number of imported cases, a local transmission of YF in temperate regions where Ae. albopictus is established becomes a plausible scenario, underlining the need for continued vigilance for YF.
LINK TO FULL ARTICLE
Rapid communication
We assessed the ability of a French population of Aedes albopictus to transmit yellow fever virus (YFV). Batches of 30 to 40 female mosquitoes were analysed at 7, 14 and 21 days post-exposure (dpe). Bodies, heads and saliva were screened for YFV. Infectious viral particles were detected in bodies and heads at 7, 14 and 21 dpe whereas the virus was found in saliva only from 14 dpe. Our results showed that Ae. albopictus can potentially transmit YFV.
The establishment of a local YF transmission cycle outside endemic areas is related to competent Aedes mosquitoes, active all year long in tropical regions and during the warm period in temperate areas. The mosquito species Ae. albopictus is present in 20 European countries [18], and a strain of this species (Houston) in the United States has been previously reported to be a competent vector for YFV [19]. Hence travellers returning to Europe from countries where a YF outbreak is occurring could be a source of infection for local strains of Ae. albopictus. We therefore assessed the competence of Ae. albopictus mosquitoes from the south of France for a West African strain of YFV.
The virus was detected at 14 dpe in saliva of the French Ae. albopictus mosquitoes at a rate of two mosquitoes in 40, a relatively low TE. While this is reassuring, a low vector competence can on the other hand contribute to select for virulent virus strains capable of eliciting high viraemia in humans [20] and causing more severe clinical symptoms [21]. Moreover although our results point to a low TR (2/9) for YFV, the anthropophilic nature of Ae. albopictus mosquitoes and their high densities in urban areas may allow them to be a vector of YFV.
Concerning the virus strain assessed in this study, the West African YFV strain should not be very genetically distant from the other six genotypes with ca 9% amino-acid divergence between strains, indicating genetic stability of YFV genotypes [7]. However, small genetic changes in the viral genome may change the vector competence.
As Europe has faced YF outbreaks in the past [22], the last being recorded in Gibraltar in 1905, a risk of importation of YF into Europe is to be considered. Although so far there have been hardly any reports from Europe of imported YF cases, many imported cases of chikungunya and dengue, two other arboviral diseases, have been documented [23].
If YF follows the same path as dengue and chikungunya, which have a greater number of imported cases, a local transmission of YF in temperate regions where Ae. albopictus is established becomes a plausible scenario, underlining the need for continued vigilance for YF.
LINK TO FULL ARTICLE