Abstract
BackgroundJapanese encephalitis virus (JEV) is the causative agent of Japanese encephalitis, the leading cause of viral encephalitis in Asia. JEV transmission cycle involves mosquitoes and vertebrate hosts. The detection of JEV RNA in a pool of Culex pipiens caught in 2010 in Italy raised the concern of a putative emergence of the virus in Europe. We aimed to study the vector competence of European mosquito populations, such as Cx. pipiens and Aedes albopictus for JEV genotypes 3 and 5.FindingsAfter oral feeding on an infectious blood meal, mosquitoes were dissected at various times post-virus exposure. We found that the peak for JEV infection and transmission was between 11 and 13 days post-virus exposure. We observed a faster dissemination of both JEV genotypes in Ae. albopictus mosquitoes, when compared with Cx. pipiens mosquitoes. We also dissected salivary glands and collected saliva from infected mosquitoes and showed that Ae. albopictus mosquitoes transmitted JEV earlier than Cx. pipiens. The virus collected from Ae. albopictus and Cx. pipiens saliva was competent at causing pathogenesis in a mouse model for JEV infection. Using this model, we found that mosquito saliva or salivary glands did not enhance the severity of the disease.ConclusionsIn this study, we demonstrated that European populations of Ae. albopictus and Cx. pipiens were efficient vectors for JEV transmission. Susceptible vertebrate species that develop high viremia are an obligatory part of the JEV transmission cycle. This study highlights the need to investigate the susceptibility of potential JEV reservoir hosts in Europe, notably amongst swine populations and local water birds.
Highlights
Japanese encephalitis is one of the major viral encephalitides in Asia, with an estimated 68,000 human cases per year [1]
We found that mosquito saliva or salivary glands did not enhance the severity of the disease
We demonstrated that European populations of Ae. albopictus and Cx. pipiens were efficient vectors for Japanese encephalitis virus (JEV) transmission
Summary
Japanese encephalitis is one of the major viral encephalitides in Asia, with an estimated 68,000 human cases per year [1]. JEV strains can be differentiated into five genotypes (1 to 5) based on phylogenetic studies of the viral envelope protein sequences. Most of the strains of JEV at the origin of major epidemics in the South, East and Southeast Asia regions belonged to genotype 3 [3, 4]. No other JEV genotype 5 strain had been identified until its recent isolation from Culex spp. mosquito pools in China in 2009 [11] and in South Korea in 2010 and 2012 [12, 13]. Japanese encephalitis virus (JEV) is the causative agent of Japanese encephalitis, the leading cause of viral encephalitis in Asia. The detection of JEV RNA in a pool of Culex pipiens caught in 2010 in Italy raised the concern of a putative emergence of the virus in Europe. We aimed to study the vector competence of European mosquito populations, such as Cx. pipiens and Aedes albopictus for JEV genotypes 3 and 5
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