Vector competence of Australian Aedes aegypti and Aedes albopictus for an epidemic strain of Zika virus.

Leon E Hugo,Helen M Faddy,Liesel Stassen,O’Mezie Ekwudu,Francesca D Frentiu,Jessica La,Elvina Viennet,Clay Winterford,Edward Gosden,Gregor J Devine,Lyric C Bartholomay

doi:10.1371/journal.pntd.0007281

Abstract

BackgroundRecent epidemics of Zika virus (ZIKV) in the Pacific and the Americas have highlighted its potential as an emerging pathogen of global importance. Both Aedes (Ae.) aegypti and Ae. albopictus are known to transmit ZIKV but variable vector competence has been observed between mosquito populations from different geographical regions and different virus strains. Since Australia remains at risk of ZIKV introduction, we evaluated the vector competence of local Ae. aegypti and Ae. albopictus for a Brazilian epidemic ZIKV strain. In addition, we evaluated the impact of daily temperature fluctuations around a mean of 28°C on ZIKV transmission and extrinsic incubation period.Methodology/Principal findingsMosquitoes were orally challenged with a Brazilian ZIKV strain (8.8 log CCID50/ml) and maintained at either 28°C constant or fluctuating temperature conditions. At 3, 7 and 14 days post-infection (dpi), ZIKV RNA copies were quantified in mosquito bodies, as well as wings and legs, using qRT-PCR, while virus antigen in saliva (a proxy for transmission) was detected using a cell culture ELISA. Despite high body and disseminated infection rates in both vectors, the transmission rates of ZIKV in saliva of Ae. aegypti (50–60%) were significantly higher than in Ae. albopictus (10%) at 14 dpi. Both species supported a high viral load in bodies, with no significant differences between constant and fluctuating temperature conditions. However, a significant difference in viral load in wings and legs between species was observed, with higher titres in Ae. aegypti maintained at constant temperature conditions. For ZIKV transmission to occur in Ae. aegypti, a disseminated virus load threshold of 7.59 log10 copies had to be reached.Conclusions/SignificanceAustralian Ae. aegypti are better able to transmit a Brazilian ZIKV strain than Ae. albopictus. The results are in agreement with the global consensus that Ae. aegypti is the major vector of ZIKV.

Highlights

Over the past decade, Zika virus (ZIKV) has caused unprecedented epidemics in the Western Pacific and the Americas
The recent ZIKV epidemic in the Americas has been linked to the urban vector Aedes aegypti
We determine the vector competence of Australian Ae. aegypti and Ae. albopictus mosquitoes for a ZIKV epidemic strain, originating from the epicentre of the Brazilian outbreak, under constant and fluctuating temperatures that simulate field environments in Australia. Both species were susceptible to ZIKV infection, Ae. aegypti is more likely to transmit virus

Summary

Introduction

Zika virus (ZIKV) has caused unprecedented epidemics in the Western Pacific and the Americas. The transmission efficiency of ZIKV is governed by interactions between mosquito strain [25, 53] and virus genotype/strain [45, 53, 55,56,57] This variability underscores the importance of evaluating the vector competence of local mosquito populations for ZIKV. Recent epidemics of Zika virus (ZIKV) in the Pacific and the Americas have highlighted its potential as an emerging pathogen of global importance. Both Aedes (Ae.) aegypti and Ae. albopictus are known to transmit ZIKV but variable vector competence has been observed between mosquito populations from different geographical regions and different virus strains. We evaluated the impact of daily temperature fluctuations around a mean of 28 ̊C on ZIKV transmission and extrinsic incubation period

Methods

Results

Discussion

Conclusion