A program to eliminate the exotic mosquito capable of transmitting the dengue virus, Aedes aegypti, has been under way in Tennant Creek since 22 February 2004. This followed the finding of this mosquito via routine adult mosquito trapping on 17 February 2004. Further surveys by the Medical Entomology Branch (MEB) of the Centre for Disease Control (CDC) of the Northern Territory Department of Health and Community Services (DHCS) have indicated to date that the dengue mosquito is firmly established in Tennant Creek. Elimination of this mosquito will take a major effort by health and local authorities as well as by the general public in Tennant Creek.

In Alice Springs, the Ilparpa Swamp is the most productive mosquito breeding site for the common banded mosquito, Culex annulirostris. The swamp is of major public health concern due to potential outbreaks of Murray Valley encephalitis (MVE), with the virus transmitted by this mosquito. In 2001, extensive flooding and two MVEV disease cases led to the first aerial control of Ilparpa Swamp, with aerial control also carried out in 2010. In January 2015, Alice Springs again received heavy rainfall associated with monsoonal activity in the north-east, indicating a possible MVEV disease risk. DoH responded by carrying out another aerial control operation in Ilparpa Swamp, with the successful operation jointly funded by the Power and Water Corporation and the Department of Lands & Planning.

The introduction of target-specific adult mosquito traps (Biogents® (BG) sentinel mosquito traps) in 2009/10 to detect exotic dengue vectors at Darwin port facilities has apparently increased the ability and frequency of their detection. The latest detection of Aedes aegypti at Frances Bay in Darwin in January 2011 was followed by subsequent successful elimination measures and heightened surveillance responses, which indicated no further presence of adults or larvae of this species.

Darwin, in the tropical north of Australia, is subject to high numbers of mosquitoes and several mosquito-borne diseases. Many of Darwin’s residential areas were built in close proximity to tidally influenced swamps, where long-term storm-water run-off from nearby residences into these swamps has led to anthropogenic induced ecological change. When natural wet-dry cycles were disrupted, bare mud-flats and mangroves were transformed into perennial fresh to brackish-water reed swamps. Reed swamps provided year-round breeding habitat for many mosquito species, such that mosquito abundance was less predictable and seasonally dependent, but constant and often occurring in plague proportions. Drainage channels were constructed throughout the wetlands to reduce pooled water during dry-season months. This study assesses the impact of drainage interventions on vegetation and mosquito ecology in three salt-marshes in the Darwin area. Findings revealed a universal decline in dry-season mosquito abundance in each wetland system. However, some mosquito species increased in abundance during wet-season months. Due to the high expense and potentially detrimental environmental impacts of ecosystem and non-target species disturbance, large-scale modifications such as these, are sparingly undertaken. However, our results indicate that some large scale environmental modification can assist the process of wetland restoration, as appears to be the case for these salt marsh systems. Drainage in all three systems has been restored to closer to their original salt-marsh ecosystems, while reducing mosquito abundances, thereby potentially lowering the risk of vector-borne disease transmission and mosquito pest biting problems.

Ross River virus (RRV) causes the most common human arbovirus disease in Australia. Although the disease is nonfatal, the associated arthritis and postinfection fatigue can be debilitating for many months, impacting on workforce participation. We sought to create an early-warning system to notify of approaching RRV disease outbreak conditions for major townships in the Northern Territory. By applying a logistic regression model to meteorologic factors, including rainfall, a post-estimation analysis of sensitivity and specificity can create rainfall cut-points. These rainfall cut-points indicate the rainfall level above which previous epidemic conditions have occurred. Furthermore, rainfall cut-points indirectly adjust for vertebrate host data from the agile wallaby (Macropus agilis) as the life cycle of the agile wallaby is intricately meshed with the wet season. Once generated, cut-points can thus be used prospectively to allow timely implementation of larval survey and control measures and public health warnings to preemptively reduce RRV disease incidence. Cut-points are location specific and have the capacity to replace previously used models, which require data management and input, and rarely provide timely notification for vector control requirements and public health warnings. These methods can be adapted for use elsewhere.

A biting insect assessment was conducted at the Andranangoo Creek West and Lethbridge Bay West mining prospects from the 29th September to the 1st of October 2005. This included detailed ground surveys for actual and potential mosquito breeding sites, assessment of aerial photography for potential mosquito and biting midge breeding sites, and initial adult biting insect trapping at both mining prospects. The early report production meant that information from subsequent peak season adult biting insect trapping in November 2005, and January and May 2006 had to be produced in a separate supplementary report. Therefore some conclusions in the first report were drawn based on field inspections and desktop observations, and not on trap data. The following report highlights the findings of the supplementary trapping, with new conclusions in regards to mosquitoes and biting midges. Trapping conducted for the Andranangoo Creek West and Lethbridge Bay West Biting Insect Assessment Report (Warchot & Whelan 2005) is referred to as ‘initial trapping’ in this supplementary report.

Burnside Operations Pty Ltd plan to commence mining at the North Point and Princess Louise mine sites, located in the East Burnside Project Area approximately 130km south-east of Darwin. The mining method will be open cut, with ore to be transported to Union Reefs Gold Mine for processing. Workers are to be housed at the mine camp at Cosmo Village. Mine sites have the potential to create or exacerbate mosquito breeding, potentially from the creation of water dams, wetland filters, borrow pits, sediment traps, dry season water discharge, waste water disposal, as well as the construction of roads and mine waste dumps. Mine sites also have the potential to introduce new mosquito species into the Northern Territory, such as the dengue mosquito Aedes aegypti from North Queensland, if equipment was to be sourced from this area. As part of the environmental process, all major development in the NT is required to consider mosquitoes during the preparation of Environmental Impact Statements or Public Environmental reports, to ensure new development does not create new mosquito breeding sites, and also to protect the health of workers.

Matilda Minerals Limited (Matilda) proposes to develop sand mining operations at Andranangoo Creek West (Andranangoo) and Lethbridge Bay West (Lethbridge), Melville Island, Tiwi Islands, Northern Territory. The proposed operation will extract high grade heavy minerals (HM), specifically zircon and rutile, for export to China. It is estimated that a total of 99,000 t of zircon and rutile will be exported during the anticipated sand mining operation over three and half years. A proposal to mine both sites was submitted to the NT Government in the form of a Notive of Intent Document (URS, 2005). The NT Government determined the project is to undergo formal environmental assessment in the form of an Environmental Impact Assessment (EIS). Part of the EIS process is to conduct a biting insect assessment of the general project areas to determine any public health risks to workers and the potential for mining activities to alter the natural environment and create further biting insect breeding sites. The Medical Entomology Branch was commissioned by URS Australia on behalf of Matilda Minerals to undertake a biting insect assessment at both proposed sandmining sites.

A Hazchem Storage Facility is proposed at Section 4239, Hundred of Bagot. Section 4239, Hundred of Bagot is located at Hidden Valley adjacent to extensive mangrove areas of Bleesers Creek and Reichardt Creek in Frances Bay, Darwin Harbour. Section 4239 is proposed to be subdivided in future, with the proposed Hazchem Storage Facility to be built within a 4ha site in Section 4239. The areas adjacent to the proposed development area were also identified as being subject to seasonal pest problems from the salt marsh mosquito Ochlerotatus vigilax (Whelan et al 1994). Other mosquito species of potential significance in the proposed development area include Culex annulirostris and Coquillettidia xanthogaster (Whelan et al 1994). Ochlerotatus vigilax is a vector of Ross River virus (RRV) disease and Barmah Forest virus (BFV) disease, while Culex annulirostris is a vector of RRV, BFV, Murray Valley encephalitis virus (MVEV) disease and Kunjin virus (KUNV) disease. The numbers of these species of mosquitoes in this area indicated there are seasonal risks for mosquito borne disease transmission in the development area. The Medical Entomology Branch (MEB) has been asked to identify any biting insect pest or potential human health problems in the development area, and provide advice on the magnitude of the problem. To do this MEB has referred to past biting insect investigations in the development area (Whelan et al 194), as well as examined the proposed plans for the potential of the development to create or exacerbate existing biting insect problems.

It is assumed that mosquito breeding areas within proposed residential development will be rectified as a matter of course, as the suburbs are developed. However, there are a number of mosquito breeding sites that are outside the suburban area that will require rectification as soon as possible, before considerable numbers of residents move into the area.

The objectives of the biting insect assessment of the proposed Darwin City Waterfront Redevelopment area is to outline actual and potential biting insect problems within the redevelopment area, and to provide mitigation strategies to prevent or minimise biting insect problems. As with most coastal areas in the NT, the proposed development area is potentially subject to mosquito and biting midge pest problems, and potential mosquito borne disease problems.

The Blacktip Project consists of both offshore and onshore components. The onshore components include the construction and operation of an onshore processing plant, construction and operation of 3km of buried onshore pipeline, and the construction of access roads and construction camp. There were potential biting insect concerns associated with these onshore components of the Blacktip Project. EcOZ Environmental Services was commissioned by Woodside Energy Limited (Woodside) to assist in the preparation of a Draft Environmental Impact Statement (EIS) for the Blacktip Project. EcOZ Environmental Services then commissioned the Medical Entomology Branch of the Department of Health and Community Services to provide information on biting insects likely to affect the Blacktip Project.

Milingimbi is an Aboriginal community in Arnhem Land, 206 km West from Nhulunbuy. The population is 920 (NT government intranet, 30/6/2003). The community is located on Milingimbi Island. Near the end of February 2003 the Milingimbi community council expressed concerns over increased mosquito numbers to Environmental Health, who requested the Medical Entomology Branch to visit the community, assess the situation and advise on strategies to reduce mosquito problems. Two MEB officers visited Milingimbi on 7-9 April 2003 and carried out a comprehensive biting insect survey, including biting insect trapping, larval mosquito surveillance and a receptacle survey. The results of this survey and the assessment are presented in this report. A mosquito survey had previously been carried out in Milingimbi in 1983, and was documented in a MEB branch report.

There are many examples of development in the Darwin region that have led to enormous populations of a range of mosquito species, severely effecting residents in nearby areas and requiring costly rectification. To aid planners in their design of the proposed Newton development, the Medical Entomology section of the department of Health and Families has made collections of biting midges and mosquitoes form march 1984 to April 1985 in and around the proposed development area between the Elizabeth and Blackmore Rivers, south-west of Palmerston. Additional surveys of biting midge breeding areas were made in late 1987. This report analyses the result and suggest methods of minimising the adverse effects of the biting insect present in the proposed development area, and outlines some construction guidelines to avoid exacerbating the problem.

Compass Resources NL is proposing the development of the Browns Oxide mine, located in the Northern Territory approximately 65km south of Darwin and 7km north-west of Batchelor (Figure 1).The project is currently under construction. Compass Resources NL proposes to utilise open cut mining methods and a conventional hydrometallurgical process to extract approximately 3.9 million tonnes of oxide ore and produce copper, cobalt and nickel over a four year period (Public Environmental Report (PER) - Enesar Consulting Pty Ltd 2005). Mine sites have the potential to create or exacerbate mosquito breeding, from the creation of water dams, wetland filters, borrow pits, sediment traps, pit water discharge, waste water disposal, as well as the construction of roads and mine waste dumps. Mine sites also have the potential to introduce new mosquito species into the Northern Territory, such as the dengue mosquito Aedes aegypti from North Queensland, if equipment is sourced from this area. Therefore, all major development in the NT is required to consider mosquito breeding during the Environmental Assessment process, to ensure development does not create new mosquito breeding sites.

In early April 1998 the Centre for Disease Control (CDC) in Darwin was notified of a case with positive dengue serology. The illness appeared to have been acquired in the Northern Territory (NT). Because dengue is not endemic to the NT locally acquired infection has significant public health implicationst particularly for vector identification and control to limit the spread of infection. Dengue IgM serology was positive on two occasions but the illness was eventually presumptively identified as Kokobera infection. This case illustrates some important points about serology. The interpretation of flavivirus serology is complex and can be· misleadingt despite recent improvements. The best method of determining the cause of infection is still attempting to reconcile clinical illness details with incubation times and vector presence, as well as laboratory results. This approach ultimately justified the initial period of waiting for confirmatory results in this case, before the institution of public health measures necessary for a true case of dengue.

Cockroaches can be significant pest and potential public health problems in the tropics. The guide and recommendations below have been produced with public buildings in mind but can equally apply to private premises. They have been aimed at the German cockroach as they are more common in institutions and residential premises in the Northern Territory but the principles apply equally to the larger American cockroach. They are aimed at the owner or occupier conducting the control, rather than engaging a licensed pest control operator.

Originally published as a media release, this article was re-published in the Northern Territory Disease Control Bulletin Vol. 18, no. 4, Dec. 2011 on pages 23-24. It encourages the Tennant Creek community to help control an infestation of Aedes aegypti mosquitoes by eliminating their breeding sites.

Mosquitoes are problematic as vectors and pests in many tropical cities, including Darwin, the principal city in the Northern Territory of Australia. To monitor peaks in mosquito populations, the Medical Entomology unit of the Health Department sets overnight CO2-baited traps weekly. Trap setting and retrieving, followed by mosquito counting and identification, are labor intensive. Aiming to reduce this workload, we tested the hypothesis that fortnightly trapping is as effective as weekly trapping across seasons and ecologically distinct systems in Darwin. We applied cross-sectional negative binomial mixed effects models, which adjusted for rain and calendar month, to existing historical data. Culex annulirostris peaks were effectively identified using fortnightly trapping across all three ecological systems, during wet/dry and build-up seasonal patterns. For Aedes vigilax, fortnightly trapping was adequate in identifying peaks during wet and dry season months,but inadequate during build-up months across all three ecological systems. Therefore, weekly trapping should continue during build-up months, but trapping could be reduced to fortnightly for wet and dry season months for all ecological systems. Trapping for Cx. annulirostris monitoring could be reduced to fortnightly in all areas and seasons. Evaluation of programs can maximize staff efficiency and improve service delivery by reducing the need for unnecessary tasks.

In April 1992 the Darwin City Council approached the Medical Entomology Branch, Department of Health & Community Services to conduct a trial to determine the efficacy of Enviroblox insecticidal blocks against blowflies and their larvae in wheelie bins. These blocks consisted largely of napthalene with 2% permethrin. Initial trials indicated that the insecticidal activity of the blocks was not adequate for effective control (especially of larvae). A second batch of Enviroblox insecticidal blocks containing 10% dichlorvos with napthalene were tested against blowflies and their larvae. Under the trial conditions these blocks killed blowflies within half an hour and larvae within six hours. Shelltox Ministrips which contain 18.6% dichlorvos were found to kill blowflies and larvae as effectively as the insecticidal blocks. Larvae feeding on organic matter within plastic bags may be protected from the insecticide vapour in the bin air space. However once larvae escape from the bags to search for pupation sites or more food they are likely to come into contact with a lethal dose of insecticide. The report concludes that a trial of the blocks in household wheelie bins in part of Darwin should be undertaken to confirm the trial results reported here.