The purpose of undertaking mosquito management is to provide a level of control over nuisance species and vectors of medical importance, sufficient to reduce vector borne disease in the Townsville region.
Proactive Urban Mosquito Response Program
Public Notice - Mosquito Inspection Program
A Proactive Urban Mosquito Response Program will take place from the 4th October to the 23rd December 2011.
Dengue Fever outbreaks in Townsville have become more frequent over the last few years with most outbreaks typically lasting several months. One of the largest Dengue outbreaks in 50 years occurred back in early 2009 with more than 70 cases reported and having both type 1 and type 3 strains. Several suburbs were affected during this outbreak and well over 2000 properties were inspected. There have been four other separate outbreaks since then in November 2009 to April 2011.
Dengue Fever is a communicable disease with debilitating and potentially life threatening consequences to those affected within our community. Dengue Fever is endemic as it is not normally present in Australia. Cases of dengue fever are imported by people who become infected overseas, and then return to or visit Australia.
Dengue Fever transmission only occurs via the Aedes aegypti mosquito. This mosquito is one that breeds primarily in artificial containers around the home or business, and has a limited flight range of approximately 200m. This means that the disease spreads via mosquitoes around infected persons properties and also their neighbours’ properties.
Reactive control measures are currently conducted by Queensland Health and Environmental Health Services during an outbreak and are aimed at reducing Aedes aegypti adult populations by the elimination of breeding sites in properties within a 200m radius of known dengue case. An ‘Authorised Prevention and Control Program’ is generally issued for a period (usually 3- 6 months) once a dengue outbreak has been confirmed by Qld Health. Reactive responses have proven to be extremely labour intensive with the outbreak in early July 2009 consuming almost 200 council officer days in total.
However, to reduce the likelihood or severity of an outbreak from occurring, an ‘Approved Inspection Program’ is an ideal way for Vector Control staff to check for and eliminate any mosquito breeding, particularly the dengue mosquito Aedes aegypti, prior to cases of Dengue Fever being imported to Townsville. This would reduce the likelihood that any imported cases of Dengue Fever being transmitted due to reduced dengue mosquito populations, reducing overburden on resources during a reactive disease outbreak response.
Householders will be given the opportunity to be ‘good community citizens’ and comply with any directions given from council officers with regard to legislative requirements. In situations where the householder does not comply with a direction from Vector Control staff, then any enforcement action will be generated through the existing Customer Service Request System for investigation by Environmental Health Officers.
Council's role
Council acknowledges its role in providing mosquito control activities for the benefit of the wider community. Council conducts mosquito control on unallocated State lands and council lands through both ground and aerial treatments. The community is encourage to participate in mosquito control on their lands through the removal of breeding sites (eg artificial water-filled containers). Community awareness information is available through print media advertisements, scheduled radio campaigns, fact sheets and pamphlets.
Saltwater areas are treated when required depending on rain and tidal activity. Freshwater areas are inspected routinely and larvae are treated if found in areas.
Triggers for Treatment
Triggers for treatment will largely depend upon the target environment (fresh or salt water) and certain preconditions within that unique environment.
Freshwater Considerations
- Rain events and duration
- Excessive landscape watering
- Amount of flooded areas
- Abundance of mosquito larvae
Saltwater Considerations
- Tides > 3.48m
- Rainfall events
- Amount of breeding site inundation
- Abundance of mosquito larvae
It is difficult to predict a definitive level of rainfall or tidal event level that will necessitate a treatment. Many conditions can combine such as period from last rainfall event, level of natural aquifers in treatment areas, wind direction and wind velocity. The variability of such elements precludes the ability to place a definitive measurement on such elements.
This variability requires flexibility in the methods of assessing treatments and highlights the absolute importance of pre-treatment inspections.
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Pre-Inspection Activities
Prior to any decision to treat, pre-inspections must be carried out in all proposed treatment areas . Such inspections are in addition to routine general surveillance work conducted by ground crews. During times of emergency response activities (such as post flooding/cyclone activity), inspections of key indicator areas is essential (as a minimum), to ensure treatment areas are effectively prioritised within available resources and maximum kill rates are achieved in sites that impact residents the most.
It should be noted that due to the massive inundation that may be associated with these events and potential for prolonged adverse weather conditions, treatments are often hindered and it may be impossible to treat within the first few days post event. This shows the importance of pre-treatment inspections and the requirement for prioritisation.
Application Methods
Consideration is given to three potential treatment methods based on the following hierarchy. The rationale of this hierarchy is based upon environmental considerations (i.e. minimal impact on the environment), efficiency, effectiveness and total cost.
It should be noted that ground applications run concurrently with all aerial applications, in areas inaccessible to aircraft due to flight restriction zones (usually within 150m of residential properties).
Once the need for treatment has been determined by a pre-treatment inspection, consideration is given to the most effective and desirable application method. Generally the following considerations provide a guide to preferred treatment option.
Aerial Treatment
- Tide level ≥ 3.48m
- Extended rain event
- Abundance of mosquito larvae
- Amount of breeding site inundated
- Post disaster response
The advantage of aerial applications is the efficiency and effectiveness of applications through the ability to cover large land areas in reasonably quick time.
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Aerial treatment - helicopter
preparing for take off |
Aerial treatment of saltmarsh
mosquito breeding site |
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Ground Treatments
- Tide level ≥ 3.48m
- Minor rain events
- Concurrent with aerial treatments
- Routine treatment of minor permanent water holding bodies
Although providing an effective treatment method, ground treatments are labour intensive and are limited in the amount of areas that can be treated in the required time. Ground treatments also have the disadvantage that vehicles/4WD bikes have to physically enter treatment sites, hence the need to ensure activities are environmentally compatible. Further disadvantages are experienced as some areas permanently exclude the use of vehicle access (such as conservation areas like Town Common), requiring the need for aerial treatments to be undertaken.
Adulticiding (Fogging)
- Adverse wind conditions preventing larviciding to be effectively conducted
- Adverse rain conditions preventing larviciding to be effectively conducted
- Post disaster activity (and or outbreak) in conjunction with larviciding activities
Adulticiding activities are only undertaken as a last resort when hatching occurs after adverse tidal and climatic conditions. Treatments occur as soon as possible following a hatch preferably in mosquito habitat resting areas, prior to the mosquitoes dispersing and seeking blood meals.
Adulticiding is not conducted as part of council's normal mosquito control operation and each situation will be assessed to determine if this operation is justified.
For more information, please phone 1300 878 001 or contact Environmental Health Services.
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