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

Abstract

Background 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. 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 findings Mosquitoes were orally challenged with a Brazilian ZIKV strain (8.8 log CCID 50 /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 log 10 copies had to be reached. Conclusions/Significance Australian 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.

One-step RT-qPCR assay for ZIKV RNA detection in Aedes aegypti samples: A protocol to study infection & gene expression during ZIKV infection

“…In recent studies that used qRT-PCR analysis to detect ZIKV RNA in mosquitoes, most used hydrolysis probes as fluorescent labels. More than half of the studies that used fluorescent probes to detect ZIKV RNA also used viral extraction kits and four did not describe how RNA extraction was performed [9,14,16,18,22,23,31,32,33,34,35,36,37,38,39,40,41,42,44,45,46,48,49].…”

“…In recent studies utilizing RT-qPCR to detect ZIKV RNA in mosquitoes, which mostly analyzed vector competence, it is possible to observe a methodological trend favoring the utilization of hydrolysis probes as a fluorescent label (83% of the papers in literature) and the use of viral RNA extraction kits to obtain the RNA templates (56% of the studies). However the number of studies could actually be higher since some of them do not specify the extraction RNA method used for the experiments [9,14,16,18,19,21,22,23,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51]. Although this approach has demonstrated to be relatively effective in detecting ZIKV RNA, since the isolation of viral RNA is prioritized, it does not permit the study of the gene expression in mosquito genes during viral infection using the same samples.…”

The impact of biological invasion and genomic local adaptation on the geographical distribution of Aedes aegypti in Panama

“…Thus, the emerging data are demonstrating that even well-connected populations can adapt to environmental differences and habitat heterogeneity across narrow spatial scales. In our case, differentially adapted populations can be considered as population variants which could have potentially different abilities to vector arboviral disease (48)(49)(50)(51)(52)(53). Since environmental adaptation is an important driving factor promoting genomic differentiation within mosquito disease vectors, this should be considered in spatially predictive models.…”

A micro-PRNT for the detection of Ross River virus antibodies in mosquito blood meals: a useful tool for inferring transmission pathways

“…Female Ae. aegypti mosquitoes (aged 3-5 days) were starved of sugar solution for 5 hrs to increase their avidity and then offered seropositive or seronegative blood for 30-45 min via a membrane feeding apparatus [23]. Fully engorged and unfed mosquitoes from these treatments were maintained separately at 27±1°C and 80% RH humidity and provided with 10% sucrose solution ad libitum .…”