Outcomes
Two different mosquito traps (the Banks trap and the Mosquito Magnet Pro) can be used to detect arboviruses such as Japanese Encephalitis virus (JEV) in remote areas.
Dead JEV can be detected on sucrose-soaked cotton pads fed upon by infected mosquitoes. The research team is developing this finding into a surveillance strategy that does not require processing of mosquitoes.
Mosquitoes are especially suited to urban gardens, and urbanised birds such as pigeons, songbirds and sparrows. Crows in particular, are excellent reservoirs for West Nile virus (WNV).
The most common Culex mosquitoes (Cx. annulirostris, Cx. gelidus, Cx. quinquefasciatus) are highly susceptible to WNV. Cx. annulirostris feeds on mammals and birds indistinctively, while Cx. quinquefasciatus feeds predominantly on birds in Cairns, and on birds and mammals in Brisbane and Sydney.
Aedes mosquitoes feed primarily on mammals, and two species, Ae. vigilax and Ae. notoscriptus, could potentially transmit WNV between birds and mammals, including humans.
Visionary Goal
This project will establish a mosquito-based surveillance system for Japanese encephalitis to study mosquito population dynamics at 2 foci of Japanese encephalitis virus (JEV) activity (Badu Island and St Pauls, on Moa Island) and better understand the ecology of this virus in the Torres Strait.
Background Statement
In a review of JEV conducted by the National Arbovirus and Malaria Advisory Committee, the replacement of the sentinel pig surveillance by a mosquito-based system was given a high priority. The current sentinel pig system relies upon amplifying the virus in the pigs to detect the presence of JEV. A mosquito surveillance system is thus much safer as it does not involve the testing in pigs.
While we have shown the mosquito-based surveillance system works in small-scale trials, a bonafide operational trial in the Torres Strait comparing sentinel pigs to remote mosquito traps has not been conducted. Furthermore, the risk of JEV transmission in the Torres Strait is increasing due to increased number of domestic pigs and decreasing uptake of JEV vaccination boosters.
WNV has lead to large epidemics in the USA, with 1000s of human cases and a significant impact on wildlife. The profound impact that WNV has had upon the USA suggests that Australia could be at risk of importation and establishment of this virus. Clearly, we need to be prepared. To do so we must assess the risk that WNV could become established and potentially cause epizootics in birds leading to human and animal cases. We will investigate the entomological aspects of risk. With the high level of WNV surveillance in the USA, this technology would be appealing to WNV programs.
Objectives & Aims of Project
1. Set single Banks updraft traps on Badu and Moa (St Pauls) Islands to collect mosquitoes and screen for JEV. Collect sera from sentinel pigs and screen for virus and anti-JEV IgM. The relative time when virus was detected in mosquitoes versus pig seroconvertion will be compared.
2. Determine if JEV activity occurs at low levels during the dry season (i.e. if the virus over winters locally).
3. Extend existing real-time (TaqMan®) PCR assays for the identification of common urban bird species (such as crows, pigeons, etc.) in mosquito blood meals.
4. Collect mosquitoes from the canopy of urban areas of eastern Queensland (Cairns, Brisbane, Sydney) to determine whether competent vectors for WNV (and/or other arboviruses) are present.
Deliverables
(a) Operational trial of the efficacy of a remote mosquito trap – real-time PCR system to detect JEV in mosquitoes from the Torres Strait (2005)
(b) From (a), an optimised mosquito-based system for the surveillance of JEV that could be extended to other arboviruses (2006)
(c) Longitudinal trap collections and JEV virus detection at Badu and Moa Islands over 3 years (2005-2007)
(d) Molecular tools for the identification of avian-derived mosquito bloodmeals collected from urban areas (2005)
(e) The relative abundance of Kunjin virus (KUNV) and its mosquito vectors in Cairns, Brisbane and Sydney, likely locations where WNV could be introduced into Australia (2006)
(f) A risk assessment of the likelihood that ornithophilic Culex mosquitoes could cause epizootics of KUNV and WNV in eastern urban areas of Australia (Cairns, Brisbane, Sydney) (2006)
(g) Determine the susceptibility of Australian mosquitoes to a North American strain of WNV (New York NY99-4132 strain, which was isolated from a dead crow in 1999)
(h) Determine if infected mosquito species can transmit the virus to a susceptible vertebrate host |