A female resident of Townsville, Queensland, Australia has been diagnosed with Zika virus infection following a recent trip to the Cook Islands. An initial serum sample collected in March, 2014 was positive by two separate Zika virus TaqMan real-time RT-PCRs and a pan-Flavivirus RT-PCR. Nucleotide sequencing and phylogenetics of the complete Cook Islands Zika virus envelope gene revealed 99.1% homology with a previous Cambodia 2010 sequence within the Asian lineage. In addition, IgG and IgM antibody seroconversions were detected between paired acute and convalescent phase sera using recombinant Zika virus serology assays. This is the first known imported case of Zika virus infection into northern Queensland where the potential mosquito vector Aedes aegypti is present and only the second such reported case diagnosed within Australia.

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Dengue viruses (DENVs) are the leading cause of mosquito-borne viral disease of humans. They exist in both endemic and sylvatic ecotypes. In 2014, a viremic patient who had recently visited the rainforests of Brunei returned to Australia displaying symptoms consistent with DENV infection. A unique DENV strain was subsequently isolated from the patient, which we propose belongs to a new genotype within DENV serotype 1 (DENV-1). Bayesian evolutionary phylogenetic analysis suggests that the putative sylvatic DENV-1 Brunei 2014 (Brun2014) is the most divergent DENV-1 yet recorded and increases the time to the most recent common ancestor (MRCA) for DENV-1 from ≈120 years to ≈315 years. DENV-1 classification of the Brun2014 strain was further supported by monoclonal antibody serotyping data. Phenotypic characterization demonstrated that Brun2014 replication rates in mosquito cells and infection rates in Aedes aegypti mosquitoes were not significantly different from an epidemic DENV-1 strain. Given its ability to cause human illness and infect Ae. aegypti, potential urban spillover and clinical disease from further Brun2014 transmission cannot be discounted.

BackgroundEmerging and re-emerging arthropod-borne viruses (arboviruses) cause human and animal disease globally. Field and laboratory investigation of mosquito-borne arboviruses requires analysis of mosquito samples, either individually, in pools, or a body component, or secretion such as saliva. We assessed the applicability of mosquito excreta as a sample type that could be utilized during studies of Ross River and West Nile viruses, which could be applied to the study of other arboviruses.Methodology/Principal findingsMosquitoes were fed separate blood meals spiked with Ross River virus and West Nile virus. Excreta was collected daily by swabbing the bottom of containers containing batches and individual mosquitoes at different time points. The samples were analyzed by real-time RT-PCR or cell culture enzyme immunoassay. Viral RNA in excreta from batches of mosquitoes was detected continuously from day 2 to day 15 post feeding. Viral RNA was detected in excreta from at least one individual mosquito at all timepoints, with 64% and 27% of samples positive for RRV and WNV, respectively. Excretion of viral RNA was correlated with viral dissemination in the mosquito. The proportion of positive excreta samples was higher than the proportion of positive saliva samples, suggesting that excreta offers an attractive sample for analysis and could be used as an indicator of potential transmission. Importantly, only low levels of infectious virus were detected by cell culture, suggesting a relatively low risk to personnel handling mosquito excreta.Conclusions/SignificanceMosquito excreta is easily collected and provides a simple and efficient method for assessing viral dissemination, with applications ranging from vector competence experiments to complementing sugar-based arbovirus surveillance in the field, or potentially as a sample system for virus discovery.