Vector competence of Australian Culex gelidus Theobald (Diptera: Culicidae) for endemic and exotic arboviruses

Abstract

The recent recognition of established populations of the mosquito, Culex gelidus Theobald, in Australia has raised concerns about local transmission of arboviruses. The vector competence of a mainland population of Cx. gelidus was investigated for two local alphaviruses, Ross River (RRV) and Barmah Forest (BFV) viruses, and three flaviviruses, Japanese encephalitis (JEV), Kunjin (KUNV) and Murray Valley encephalitis (MVEV) viruses. Colonised mosquitoes were exposed to virus via blood-soaked pledgets and transmission was tested using a capillary-tube method. The important Australian vectors, Aedes vigilax (Skuse) and Culex annulirostris Skuse, were used as internal controls for the alphaviruses and flaviviruses, respectively. Overall, Cx. gelidus was a more efficient vector of flaviviruses than alphaviruses. Culex gelidus was refractory to infection with BFV, and nearly 25% transmitted RRV, which was comparable to Ae. vigilax. Culex gelidus was susceptible to all three flaviviruses, with transmission rates of 96%, 95% and 41% for JEV, KUNV and MVEV, respectively. JEV transmission rates in Cx. annulirostris were unexpectedly low and this was possibly due to differences in susceptibility to JEV genotypes I and II. Considering the high susceptibility to the flaviviruses demonstrated here, and the natural infections with RRV and JEV that have been detected from northern Australian populations, the establishment of the exotic mosquito, Cx. gelidus, in Australia is potentially a significant public health concern.

Aedes albopictus(Diptera: Culicidae) as a Potential Vector of Endemic and Exotic Arboviruses in Australia

“…Although caution must be exercised when comparing different vector competence experiments, previ- ous work by Johnson et al (2009) conducted in our laboratories using similar methods, feeding titers, and the same virus strains as the current study, allowed us to place the current work into context. This earlier work has provided suitable data on known vectors of the major Australian endemic arboviruses and JEV, from which the data on Ae.…”

“…Two species implicated as JEV vectors in Australia are Cx. annulirostris and Culex gelidus (Theobald) (Ritchie et al 1997;van den Hurk et al 2001van den Hurk et al , 2003Johnson et al 2009). Dengue outbreaks occur regularly in northern Queensland where the primary vector Aedes aegypti (L.) occurs (Hanna and Ritchie 2009).…”

Development of multiplex suspension microarrays for the detection of alphaviruses and flaviviruses of public health significance

“…These samples included Aedes vigilax mosquitoes infected with BFV strain BH2193 and RRV strain 389A, and Aedes aegypti mosquitoes infected with a strain of CHIKV isolated from the Reunion Island outbreak in 2006. The methods used to infect these mosquitoes with virus have been previously described (Johnson, 2009.…”

“…Virus positive mosquitoes from published vector-competence studies were used to validate the suspension microarray and the methods used to infect the viruses have been previously described (Johnson, 2009, Jansen et al, 2008. All experiments were conducted in a physical containment level 3 (PC3) insectary located at QHFSS.…”

“…Molecular tests have also been developed for the detection of RRV (Sellner et al, 1994, Hall, 2009, SINV (Sane et al, 2011) and BFV (A Pyke, unpublished data).…”