Culex quinquefasciatus mosquitoes do not support replication of Zika virus

Abstract

The rapid spread of Zika virus (ZIKV) in the Americas raised many questions about the role of Culex quinquefasciatus mosquitoes in transmission, in addition to the key role played by the vector Aedes aegypti. Here we analysed the competence of Cx. quinquefasciatus (with or without Wolbachia endosymbionts) for a ZIKV isolate. We also examined the induction of RNA interference pathways after viral challenge and the production of small virus-derived RNAs. We did not observe any infection nor such small virus-derived RNAs, regardless of the presence or absence of Wolbachia. Thus, Cx. quinquefasciatus does not support ZIKV replication and Wolbachia is not involved in producing this phenotype. In short, these mosquitoes are very unlikely to play a role in transmission of ZIKV. Micronesia and then in French Polynesia in 2013-2014, and after affecting most of the South Pacific islands, the virus was eventually detected in the Americas in 2015 [1][2][3][4]. The increased number of infections in humans included cases with unusually severe symptoms such as Guillain-Barr e syndrome and developmental abnormalities in newborns that are now described as congenital Zika syndrome [5][6][7][8]. As there are currently no licensed vaccines or specific therapies, the only way to interrupt ZIKV transmission is by controlling mosquito populations [9]. An enzootic cycle limited to Africa and Asia with occasional spillover events has been described [10,11]. In the current outbreak in the Americas, ZIKV is believed to be mainly transmitted by the human-biting mosquito Aedes aegypti [12,13]. Whether a similar enzootic cycle in the Americas can be established is not known and it has been suggested that such a process would make eradication efforts 'practically impossible' [14]. Experimental infections with the epidemic ZIKV genotypes demonstrated that populations of Ae. aegypti and Ae. albopictus mosquitoes, which are associated with a risk of local transmission [15] as well other aedine species were heterogeneously and weakly competent for transmission [16][17][18][19][20][21][22][23][24][25]. Therefore, the potential role of other anthropophilic mosquitoes in the ZIKV outbreak raised a question which took time to be addressed [26]. Culex quinquefasciatus Say is an opportunistic blood feeder predominant in urban settings throughout the tropics where it is frequently the most annoying biting pest to humans [27]. This night-active mosquito is also the vector of many pathogens including arboviruses such as West Nile and St. Louis encephalitis viruses [28], which belong to the genus Flavivirus of the family Flaviviridae and are related to ZIKV. Both Cx. quinquefasciatus and Culex pipiens (from temperate regions) mosquitoes of the Cx. pipiens complex were not able to experimentally transmit ZIKV and no viral particles were detected in mosquito saliva up to 21 days after exposure to an infectious blood meal [17-20, 25, 29-36], though different results were recorded with other Cx. quinquefasciatus strains [37,38]. Even after injection o...

Endogenous Viral Elements Are Widespread in Arthropod Genomes and Commonly Give Rise to PIWI-Interacting RNAs

“…These viruses are transmitted by their respective insect vectors in a noncirculative manner (3). In agreement with these findings, we also identified a number of EVEs corresponding to viruses of the Closteroviridae and Bromoviridae families, as well as several other families comprised of viruses not known to replicate outside their plant hosts, including Geminiviridae, quefasciatus (13,14,20). However, it is unclear whether piRNAs are produced from EVEs in nonmosquito arthropod species.…”

Zika and dengue viruses infecting wild-caught mosquitoes in an environmental protection area in Brazil

“…They demonstrated that Cx. quinquefasciatus is a competent vector for ZIKV, disagreeing with the findings of Lourenço-de-Oliveira et al [47], who showed that these mosquitoes neither support replication of ZIKV nor play a role in transmission of this virus. Moreover, our study has demonstrated that other species of the Culex genus have vector competence for DENV-2.…”

Endogenous viral elements are widespread in arthropod genomes and commonly give rise to piRNAs

“…Previous studies have revealed that EVEs serve as a templates for piRNA production in A. aegypti, A. albopictus , and Culex quinquefasciatus [14, 15, 26], however, it is unclear whether piRNAs are produced from EVEs in non-mosquito arthropod species. We examined the sRNAs mapping to each EVE for the characteristics of primary piRNAs (i.e.…”