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Dengue mosquito eradication project, Tennant Creek, end of January 2005 progress report
... It is thought that Ae. aegypti disappeared due to a reduction of artificial breeding receptacles following the movement to reticulated water and diesel trains [2,8]. However, in the past 13 years, Ae. aegypti incursions occurred in Tennant Creek on two separate occasions in 2004 and 2011, and once on Groote Eylandt during 2006, with all three incursions eliminated via intensive 2-3 year programs [9][10][11]. Imported Aedes aegypti and the Asian tiger mosquito Aedes albopictus are also frequently found in Department of Agriculture and Water Resources surveillance traps at Darwin international air and seaports [12]. ...
The Northern Territory Top End Health Service, Medical Entomology Section and the City of Darwin council carry out a joint Mosquito Engineering Program targeting the rectification of mosquito breeding sites in the City of Darwin, Northern Territory, Australia. In 2005, an investigation into potential subterranean stormwater breeding sites in the City of Darwin commenced, specifically targeting roadside stormwater side entry pits. There were 79 side entry pits randomly investigated for mosquito breeding in the Darwin suburbs of Nightcliff and Rapid Creek, with 69.6% of the pits containing water holding sumps, and 45.6% of those water holding sumps breeding endemic mosquitoes. Culex quinquefasciatus was the most common mosquito collected, accounting for 73% of all mosquito identifications, with the potential vector mosquito Aedes notoscriptus also recovered from a small number of sumps. The sumps were also considered potential dry season maintenance breeding sites for important exotic Aedes mosquitoes such as Aedes aegypti and Aedes albopictus, which are potential vectors of dengue, chickungunya and Zika virus. Overall, 1229 side entry pits were inspected in ten Darwin suburbs from 2005 to 2008, with 180 water holding sumps identified and rectified by concrete filling.
... Transmission of DENV in Australia is currently restricted to urban areas of north Queensland and the Torres Strait where Ae. aegypti remains well established and outbreaks regularly occur following importations of dengue viruses by returning travellers infected overseas567. Recent incursions of Ae. aegypti into towns in the Northern Territory have occurred, but the vectors were eliminated without any dengue activity being detected8910. In WA, outbreaks of dengue were reported in northern parts of the state up until the mid-1940s [6] and Ae. ...
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 den-gue 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.
... It has not been subsequently detected anywhere on Groote Eylandt or elsewhere in the NT. This is the second successful attempt to eradicate an established mosquito species in Australia (Whelan et al. 2005), and the first in the higher rainfall tropical region of Australia. The Ae. aegypti elimination on Groote Eyland has been largely a top down approach. ...
... annulirostris (Russell and Whelan 1986; Van Essen et al. 1994; Miller et al. 2005; Williams et al. 2006). Indeed, CO 2 -baited mosquito traps are effective for registering relative adult abundance and population rates of change (Whelan et al. 2005). For this particular study, we only used the data on female population density due to their blood-feeding behaviour and their importance for disease transmission. ...
Cited By (since 1996):14, Export Date: 26 November 2013, Source: Scopus
... CO 2 -baited traps also tend to target nulliparous females more effectively than other methods, but may not always be as efficient as backpack aspirators or BG- Sentinels (Williams et al. 2006). Regardless, they are effective at registering relative adult abundance and can be used to estimate population rates of change (Whelan et al. 2005). The distance between each pair of traps varied from 1 to 3 km, with the traps covering a total area of 63.2 km 2 . ...
Cited By (since 1996):16, Export Date: 26 November 2013, Source: Scopus
The Northern Territory (NT) of Australia is currently free of the dengue mosquito Aedes (Stegomyia) aegypti (L). However, on 17 February 2004, two Ae. aegypti adults were captured in two routine CO2‐baited encephalitis virus surveillance traps in Tennant Creek, located 990 km south of Darwin in the NT. The detection triggered an immediate survey and control response undertaken by the NT Department of Health and Community Services, followed by a Commonwealth of Australia‐funded Ae. aegypti elimination program. This report details the methods and results of the detection and subsequent elimination activities that were carried out between 2004 and 2006, returning the NT to its dengue vector‐free status. There have been very few successful Ae. aegypti elimination programs in the world. This purposeful mosquito elimination for Australia was officially declared on 5 April 2006.
In Australia, the re-introduction of large, permanent water storage containers (known as rainwater tanks) as a response to climate instability has increased the risk of establishment of mosquito invasions and therefore the transmission of disease. An estimated 300,000 rainwater tanks have been installed into south east Queensland since 2006. This project aimed to identify the risk they pose.
To understand the role that rainwater tanks played in past epidemics of vector-borne disease, such as dengue, this thesis reviewed the history and potential mechanisms for the disappearance of Aedes aegypti (L.) from its historical, southern range in Australia. Government surveillance records from Brisbane (the capital of Queensland, Australia) were collated from the period when Ae. aegypti was extant until its last detection in 1957. Several factors were likely responsible for the disappearance of the species including the introduction of reticulated water and the removal of rainwater tanks, and increased mosquito surveillance backed up by regulatory enforcement. This thesis demonstrates the value of historical data to help identify potential invasion risks and indicates the dramatic impact that mosquito surveillance, supported by government regulations, can have on Ae. aegypti persistence at the margins of its distribution.
Field observations and laboratory trials were conducted to measure the temperature buffered environment of rainwater tanks and determine growth and survival of Ae. aegypti in these containers during winter in Brisbane. Abiotic conditions in rainwater tanks were measured and data loggers were placed outdoors in buckets and rainwater tanks during winter and summer. For laboratory experiments daily temperature fluctuations were selected based on the coldest week of the year. Tropical and sub-tropical colonies of Ae. aegypti were established from material collected from different location in Queensland to test for their capacity to survive Brisbane winter temperatures. Greater than 48% survival (egg to adult) was observed in all treatments and mean adult development times (egg to adult) took 32 days. As such, a population of Ae. aegypti could survive in both buckets and rainwater tanks exposed to the coldest water temperatures in Brisbane.
To test the hypothesis that climate played a role in the disappearance of Ae. aegypti in south eastern Australia, I exploited an existing bio-climatic model (using CLIMEX). Survey records from the past 100 years were collated for the species and combined with a number of biological parameters to predict: a) the historical distribution based on the presence of permanent water storage (rainwater tanks), and b) a natural distribution based on the absence of artificial and permanent water sources. Predictions for Australia were validated against a) international distribution records, and b) the annual population phenology of Ae. aegypti from Cairns, Botucatu and Sao Paulo state. If suitable water storage was present, such as rainwater tanks, climate was unlikely to have played a major role in the disappearance of Ae. aegypti in eastern Australia. However, when permanent water storage was absent, the majority of locations tested from the historical distribution were unfavourable for the persistence of the species.
To examine the role that rainwater tanks play in the presence and movement of Aedes species in urban environments, a mark, release and recapture experiment was designed and undertaken. Results suggested that roads act as barriers to male Ae. aegypti but not to female Ae. notoscriptus (Skuse), another disease vector that inhabits rainwater tanks. Female Ae. aegypti were four times more likely to be captured in traps placed proximal to rainwater tanks than in locations where rainwater tank were absent. Finally, an ‘isotropic Gaussian dispersal kernel’ was used to describe mosquito dispersal as a diffusion process of movement over time. This provides compelling evidence that permanent domestic water storage facilitated the historical persistence of Ae. aegypti across much of eastern Australia.
This thesis examined the role that a network of unsealed rainwater tanks may play in the spread of Ae. aegypti in Brisbane. Using a spatially explicit network model in Repast Simphony I simulated the movement of mosquito populations through known locations of rainwater tanks across 140 Brisbane suburbs. Movement was parameterized using an isotropic Gaussian dispersal kernel, a maximum distance of movement, average life expectancy and the probability of Ae. aegypti crossing a road over a two week period that was empirically derived. The model was run against a number of scenarios that examined population spread through rainwater tanks based on compliance rates (unsealed or not) and real road grids. Finally, this thesis described key network properties and produced risk maps to inform areas for future mosquito and rainwater tank surveillance.
The outcomes of this thesis demonstrate that large, permanent water storage containers present ideal larval habitat for the re-establishment and persistence of Ae. aegypti in areas south of its current distribution in Queensland, Australia. Large numbers of rainwater tanks have been present in south east Queensland for over a decade with little monitoring of their structural integrity or vector presence. Ongoing management of rainwater tanks in south east Queensland will be essential to prevent the establishment of disease vectors and the consequent risk of seasonal transmission of disease.
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.
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