Detection of mosquito-only flaviviruses in Europe

Abstract

The genus Flavivirus, family Flaviviridae, includes a number of important arthropod-transmitted human pathogens such as dengue viruses, West Nile virus, Japanese encephalitis virus and yellow fever virus. In addition, the genus includes flaviviruses without a known vertebrate reservoir, which have been detected only in insects, particularly in mosquitoes, such as cell fusing agent virus, Kamiti River virus, Culex flavivirus, Aedes flavivirus, Quang Binh virus, Nakiwogo virus and Calbertado virus. Reports of the detection of these viruses with no recognized pathogenic role in humans are increasing in mosquitoes collected around the world, particularly in those sampled in entomological surveys targeting pathogenic flaviviruses. The presence of six potential flaviviruses, detected from independent European arbovirus surveys undertaken in the Czech Republic, Italy,

Wide detection of Aedes flavivirus in north-eastern Italy – a European hotspot of emerging mosquito-borne diseases

“…Moreover, the prevalence of AeFV in Aedes albopictus in Trentino was higher than in Veneto and this result is supported by previous research carried out in 2008(Roiz et al, 2009, and it was also higher compared with the prevalence of ISFs detected in other northern Italian regions (e.g. Lombardia, Emilia-Romagna and Piemonte) (Roiz et al, 2009(Roiz et al, , 2012Calzolari et al, 2010a Calzolari et al, , b, 2012aCalzolari et al, , 2013aCerutti et al, 2012;Ravanini et al, 2012;Pautasso et al, 2013).These results support the hypothesis that the local ecological and climatic conditions may shape not only the abundance and distribution of mosquito populations (Roiz et al, 2010(Roiz et al, , 2011Trawinski & Mackay, 2010), but also their viral infection pattern (Newman et al, 2011;Calzolari et al, 2012b;Obara-Nagoya et al, 2013). The ecological and climatic conditions of the two study areas differ not only in climate, but also in the degree of anthropization, biodiveristy and land use.…”

“…Veneto is a region characterized by a continental climate, high anthropization, and intense agricultural and industrial activities, whilst Trentino is mostly a mountainous and forested area with a temperate climate, and a lower degree of anthropization and agricultural land. More research is now needed, however, to better understand the effect of environmental variables on AeFV ecology.In Trentino, infection prevalence with AeFV was higher in female mosquitoes than in males in which no flaviviruses were detected, but these findings may be related to the small number of male pools analysed and to the low infection levels (Cook et al, 2006;Farfan-Ale et al, 2009;Roiz et al, 2009Roiz et al, , 2012Bolling et al, 2011;Saiyasombat et al, 2011;Haddow et al, 2013).Regarding ISF transmission routes, there is evidence that both vertical and horizontal transmission are possible, as trans-ovarial transmission, horizontal transmission between larvae sharing the same aquatic habitat, transmission via shared microparasites and infection via shared sugar-rich food sources have been reported .The phylogenetic analysis showed that the AeFV sequences detected in Veneto were very similar to those detected in Trentino, and to those previously detected in these two regions and also further afield in Italy (Roiz et al, 2009(Roiz et al, , 2012Calzolari et al, 2012b). The high sequence identity of the virus that was detected in Aedes albopictus mosquitoes to those isolated in Japan would corroborate the hypothesis that these two viruses are the same or closely related (Roiz et al, 2012), but the analysis of the complete genome of these strains would be necessary to confirm this.…”

Japanese encephalitis virus RNA detected in Culex pipiens mosquitoes in Italy

“…The sequences (Box) were identified as (i) ISF from A. albopictus, 2011 (two sequences; lengths 133 and 87 bp; identical in the overlapping region), (ii) USUV from C. pipiens, 2010 and 2011 (two sequences; lengths 133 and 167 bp; identical in the overlapping region) and (iii) JEV (one sequence; 167 bp) from one pool of C. pipiens, 2010 (Figure 2). The ISF (collected in Sasso Marconi) and USUV (collected in Pontecchio Marconi and Pianoro) sequences were identical to other sequences previously reported from Italy [1,7]. The JEV sequence (genomic position: 9,109-9,275) was obtained from mosquitoes collected in Sasso Marconi.…”

“…While ISF and USUV have been documented previously in Italy and several other European countries [1,2], JEV has, to our knowledge, not been detected in mosquitoes in Europe so far. JEV is a mosquito-borne flavivirus known to be endemic in Asia, extending to India and Pakistan in the west, where it is a leading cause of encephalitis.…”

“…Following the active circulation of WNV and USUV, the recent detection of novel ISFs in Italy and elsewhere in Europe, and the detection of dengue virus in southern France and Croatia [1,7,10,11], the aim of this study was to screen mosquitoes for flavivirus RNA using a system allowing the detection of all flaviviruses. Female mosquitoes were collected in late summer of 2010 and 2011 in rural areas near Modena and Bologna in EmiliaRomagna region (Figure 1), using CO 2 -baited traps.…”