It is intuitive that vector-borne disease exposure risk is related to proximity to sources of vector breeding, but this aspect rarely receives empirical testing. The population of Western Australia (WA) is increasing rapidly, with many new residential developments proposed in close proximity to mosquito breeding habitat. However, potential mosquito-borne disease risks for future residents are given little consideration by planning authorities. The Peel region is one of the fastest growing regions in WA and regularly experiences a large number of cases of the mosquito-borne Ross River virus (RRV) disease with epidemics occuring in the region every few years. A spatial analysis of RRV disease data in the Peel region was undertaken to determine the risk associated with proximity to a mosquito breeding habitat. Geographic Information Systems (GIS) software was used to create buffers between 1 and 6 km from the breeding habitat. The number of cases per 1000 dwellings in each buffer was calculated between 2002/03 to 2011/12 for years with >100 cases across all buffers ( n =5) in addition to the cumulative rate over the entire period in each buffer. Residents living within 1 km of a mosquito breeding habitat had a significantly higher rate of RRV disease compared to the background rate across the Peel region in all individual years investigated. The cumulative data over the 10-year study period showed that residents in the 1- and 2-km buffers had a significantly higher rate, whereas those living between 3 and 6 km away did not. This study demonstrates an increased mosquito-borne disease risk associated with living in close proximity to a mosquito breeding habitat in a rapidly expanding region of WA and highlights the importance of considering mosquito-borne disease risks when planning authorities assess new residential development applications. Known mosquito breeding wetlands should be incorporated into land use planning scheme maps to ensure that they are accurately delineated and the implications are considered when planning decisions are made.

Barmah Forest virus (BFV) is a medically important mosquito-borne alphavirus endemic to Australia. Symptomatic disease can be a major cause of morbidity, associated with fever, rash, and debilitating arthralgia. BFV disease is similar to that caused by Ross River virus (RRV), the other major Australian alphavirus. Currently, just four BFV whole-genome sequences are available with no genome-scale phylogeny in existence to robustly characterise genetic diversity. Thirty novel genome sequences were derived for this study, for a final 34-taxon dataset sampled over a 44 year period. Three distinct BFV genotypes were characterised (G1–3) that have circulated in Australia and Papua New Guinea (PNG). Evidence of spatio-temporal co-circulation of G2 and G3 within regions of Australia was noted, including in the South West region of Western Australia (WA) during the first reported disease outbreaks in the state’s history. Compared with RRV, the BFV population appeared more stable with less frequent emergence of novel lineages. Preliminary in vitro assessment of RRV and BFV replication kinetics found that RRV replicates at a significantly faster rate and to a higher, more persistent titre compared with BFV, perhaps indicating mosquitoes may be infectious with RRV for longer than with BFV. This investigation resolved a greater diversity of BFV, and a greater understanding of the evolutionary dynamics and history was attained.

Rapid population growth in Western Australia has resulted in increased development of land for residential housing, and new developments are often proposed close to water because of intrinsic aesthetic values. However, this placement may place future residents at risk of mosquito-borne disease, of which Ross River virus (RRV) disease is the most common in Australia. Mosquito dispersal data were combined with a spatial analysis of human RRV cases to show that mosquitoes dispersed readily from larval habitat into surrounding low- and high-density residential areas and that residents living within 2 km of mosquito breeding habitat had a significantly higher rate of RRV disease. This finding highlights the importance of planning authorities in state and local governments to consider the implications of mosquito-borne disease risks when assessing residential development applications.

In October 2013, a locally-acquired case of dengue virus (DENV) infection was reported in Western Australia (WA) where local dengue transmission has not occurred for over 70 years. Laboratory testing confirmed recent DENV infection and the case demonstrated a clinically compatible illness. The infection was most likely acquired in the Pilbara region in the northwest of WA. Follow up investigations did not detect any other locally-acquired dengue cases or any known dengue vector species in the local region, despite intensive adult and larval mosquito surveillance, both immediately after the case was notified in October 2013 and after the start of the wet season in January 2014. The mechanism of infection with DENV in this case cannot be confirmed. However, it most likely followed a bite from a single infected mosquito vector that was transiently introduced into the Pilbara region but failed to establish a local breeding population. This case highlights the public health importance of maintaining surveillance efforts to ensure that any incursions of dengue vectors into WA are promptly identified and do not become established, particularly given the large numbers of viraemic dengue fever cases imported into WA by travellers returning from dengue-endemic regions. Dengue fever transmission in Western Australia ceased in the 1940s and there are currently no known dengue vector species present. Despite this, a locally acquired of dengue fever was reported in 2013 with the most likely location of exposure the township of Point Samson in Pilbara region in the north-west of the State. A comprehensive follow-up investigation was undertaken and while the dengue case was confirmed, no other cases were identified and not exotic dengue vector mosquitoes were detected around the location of exposure. The exact mechanism for the locally acquired infection could not be determined but the most likely explanation is that a dengue infected mosquito was transported into the region, fed on the patient, but did not survive to lay eggs and establish a local breeding population. This case highlights the potential risk of the re-emergence of dengue fever in regions of Australia outside where ongoing transmission is currently limited to in northern Queensland, particularly given the large number of imported dengue cases that occur among travellers returning from dengue endemic regions.

Japanese encephalitis virus (JEV) emerged across mainland Australia in 2022, causing substantial impacts on public health and the pig industry. Its emergence raised concerns regarding potential spread into Western Australia (WA). This study aimed to determine JEV activity in WA with a focus on the Kimberley region between 2022 and 2024. It also examined potential pathways of JEV introduction into the state and the challenges associated with flavivirus serology. An integrated surveillance program comprising targeted feral pig surveillance and sentinel chicken monitoring was implemented across northern WA. Sera were screened using flavivirus ELISAs and confirmatory plaque reduction neutralisation tests (PRNT), while feral pig tonsils were tested by RT-qPCR. Evidence of JEV activity was detected in WA between 2022 and 2024. Serological findings from two feral pigs sampled in October 2022 provided the earliest indication of JEV transmission in the Kimberley region. Sentinel chicken surveillance subsequently identified JEV activity in Kununurra, Wyndham, Halls Creek and Newman during 2023 and Derby in 2024. These results provide the first published evidence of JEV activity in WA and highlight the importance of ongoing surveillance, vaccination, mosquito control and preparedness activities in northern Australia.