No abstract

Chikungunya virus (CHIKV) is a mosquito-borne pathogen that causes an acute febrile syndrome and severe, debilitating rheumatic disorders in humans that may persist for months. CHIKV’s presence in Asia dates from at least 1954, but its epidemiological profile in the region remains poorly understood. We systematically reviewed CHIKV emergence, epidemiology, clinical features, atypical manifestations and distribution of virus genotypes, in 47 countries from South East Asia (SEA) and the Western Pacific Region (WPR) during the period 1954–2017. Following the Cochrane Collaboration guidelines, Pubmed and Scopus databases, surveillance reports available in the World Health Organisation (WHO) and government websites were systematically reviewed. Of the 3504 records identified, 461 were retained for data extraction. Although CHIKV has been circulating in Asia almost continuously since the 1950s, it has significantly expanded its geographic reach in the region from 2005 onwards. Most reports identified in the review originated from India. Although all ages and both sexes can be affected, younger children and the elderly are more prone to severe and occasionally fatal forms of the disease, with child fatalities recorded since 1963 from India. The most frequent clinical features identified were arthralgia, rash, fever and headache. Both the Asian and East-Central-South African (ECSA) genotypes circulate in SEA and WPR, with ECSA genotype now predominant. Our findings indicate a substantial but poorly documented burden of CHIKV infection in the Asia-Pacific region. An evidence-based consensus on typical clinical features of chikungunya could aid in enhanced diagnosis and improved surveillance of the disease.

To date, insect-specific flaviviruses (ISFs) have only been isolated from mosquitoes and increasing evidence suggests that ISFs may affect the transmission of pathogenic flaviviruses. To investigate the diversity and prevalence of ISFs in Australian mosquitoes, samples from various regions were screened for flaviviruses by ELISA and RT-PCR. Thirty-eight pools of Aedes vigilax from Sydney in 2007 yielded isolates of a novel flavivirus, named Parramatta River virus (PaRV). Sequencing of the viral RNA genome revealed it was closely related to Hanko virus with 62.3% nucleotide identity over the open reading frame. PaRV failed to grow in vertebrate cells, with only Aedes-derived mosquito cell lines permissive to replication, suggesting a narrow host range. 2014 collections revealed that PaRV had persisted in A. vigilax populations in Sydney, with 88% of pools positive. Further investigations into its mode of transmission and potential to influence vector competence of A. vigilax for pathogenic viruses are warranted.

Understanding the non-human reservoirs of zoonotic pathogens is critical for effective disease control, but identifying the relative contributions of the various reservoirs of multi-host pathogens is challenging. For Ross River virus (RRV), knowledge of the transmission dynamics, in particular the role of non-human species, is important. In Australia, RRV accounts for the highest number of human mosquito-borne virus infections. The long held dogma that marsupials are better reservoirs than placental mammals, which are better reservoirs than birds, deserves critical review. We present a review of 50 years of evidence on non-human reservoirs of RRV, which includes experimental infection studies, virus isolation studies and serosurveys. We find that whilst marsupials are competent reservoirs of RRV, there is potential for placental mammals and birds to contribute to transmission dynamics. However, the role of these animals as reservoirs of RRV remains unclear due to fragmented evidence and sampling bias. Future investigations of RRV reservoirs should focus on quantifying complex transmission dynamics across environments.Electronic supplementary materialThe online version of this article (10.1186/s13071-018-2733-8) contains supplementary material, which is available to authorized users.

No abstract

Urban landscape features play an important role in the distribution and population spread of mosquito vectors. Furthermore, current insecticide and novel rear-and-release strategies for urban mosquito management rarely consider the spatial structure of the landscape when applying control practices. Here, we undertake a mark-recapture experiment to examine how urban features influence the movement and distribution of Australian container-inhabiting Aedes vectors. We pay attention to the role of semipermanent water storage containers, called rainwater tanks, and the influence of movement barriers, such as roads, on the spread and distribution of vector populations. Results suggest that Aedes aegypti (Linnaeus) (Diptera: Culicidae) were more likely to be captured around rainwater tanks, and that released males travel throughout residential blocks but do not cross roads. Conversely, female Aedes notoscriptus (Skuse) (Diptera: Culicidae) movement was uninhibited by roads and rainwater tanks did not influence female distribution or oviposition behavior. Using an isotropic Gaussian kernel framework, we show that vector movement is likely to be greater when applying a temporal effect, than when estimated by traditional methods. We conclude that a greater understanding on the role of urban features on vector movement will be important in the new age of rear-and-release mosquito control strategies, particularly those where estimations of movement are important for ensuring efficacy of application.

Since the establishment of West Nile virus (WNV) into the United States, concern has arisen that this virus may also pose a serious threat to Australian biosecurity. The vector competence of 19 Australian mosquito species for a North American strain of WNV was evaluated. Mosquitoes collected from Cairns, Brisbane, and Sydney were exposed to blood containing 10(4.0+/-0.3) cell culture infectious dose(50)/mosquito WNV that was isolated from a crow during the 1999 New York outbreak. Mosquitoes were tested 12-15 days later to determine their infection, dissemination, and transmission rates. A number of Culex spp. demonstrated a high vector competence for this virus, with some populations of Culex annulirostris, the primary Australian Kunjin virus vector, displaying transmission rates up to 84%. Similarly, Cx. quinquefasciatus and Cx. gelidus were highly competent, with infection and transmission rates of >80% and >50%, respectively. Common Aedes spp., including Aedes notoscriptus, Ae. vigilax, and Ae. procax, were moderately susceptible, and some Verrallina spp. and Coquillettidia spp. were relatively refractory to infection. Thus, Australia possesses a number of competent mosquito species that could facilitate local transmission of WNV, should it be introduced.

Aedes aegypti (L.) (Diptera: Culicidae) is a highly invasive mosquito whose global distribution has fluctuated dramatically over the last 100 years. In Australia the distribution of Ae. aegypti once spanned the eastern seaboard, for 3,000 km north to south. However, during the 1900s this distribution markedly reduced and the mosquito disappeared from its southern range. Numerous hypotheses have been proffered for this retraction, however quantitative evidence of the mechanisms driving the disappearance are lacking. We examine historical records during the period when Ae. aegypti disappeared from Brisbane, the largest population centre in Queensland, Australia. In particular, we focus on the targeted management of Ae. aegypti by government authorities, that led to local elimination, something rarely observed in large cities. Numerous factors are likely to be responsible including the removal of larval habitat, especially domestic rainwater tanks, in combination with increased mosquito surveillance and regulatory enforcement. This account of historical events as they pertain to the elimination of Ae. aegypti from Brisbane, will inform assessments of the risks posed by recent human responses to climate change and the reintroduction of 300,000 rainwater tanks into the State over the past decade.