Mosquitoes have long been known to infest the coastal area of southern Redlands.
At present this area is not heavily populated so the risk of people contracting mosquito borne diseases is relatively low. This could change if plans for a major residential development are approved.
Public health implications of locating people close to mosquito breeding areas should be carefully assessed together with likely community costs.
Are mosquitoes a health risk?
Residents of the proposed Shoreline development at Redland Bay would be living close to major mosquito breeding habitats and so will be at greater risk of being bitten by mosquitoes than people living further away.
Medical entomologist Darryl McGinn prepared a Biting Insect Management Strategy report for the Shoreline proponents. This report advises that specific information about the distribution and abundance of biting mosquitoes during periods of peak seasonal activity is needed to enable development of a detailed management plan to minimise the risks to residents and visitors.
In its conclusion the McGinn report states:
The Shoreline Redlands development presents some challenges as it is exposed to mosquitoes and biting midges associated with salt-marsh and intertidal habitats of Redland Bay. Because of its current low residential population, the development site and adjoining area are not currently subject to high resolution adult biting insect surveillance by Council. There is currently a lack of good quality entomological data upon which to fully characterise the public health and nuisance biting risks or to objectively inform an appropriate management response. Notwithstanding that more scientific detail is required; there is ample anecdotal evidence of the biting insect problem in the southern Redland Bay.
Where are the mosquitoes found?
The McGinn report notes that the salt-marsh mosquito Aedes vigilax is known to breed in a number of areas on the Shoreline development site as well as nearby Pannikan, Long and Lagoon islands. The Report states that “This species has a known pest range of several kilometres from major breeding sites.”
The report also notes that the proposed development site currently contains suitable habitat for at least five mosquito species that breed in freshwater.
The distribution and abundance of mosquitoes during periods of peak seasonal activity is not well known because that information has not been collected. The McGinn Strategy report notes that among other things, Shoreline would be responsible for: “An entomological field survey to characterise the diversity and seasonal abundance of biting insects”.
Mosquitoe borne diseases in south east Queensland
Brisbane City Council advises that Ross River Virus and Barmah Forest Virus are the two most common diseases transmitted by mosquitoes to humans in south east Queensland. Dogs can also be at risk of contracting heartworm via mosquitoes. Ross River Virus causes skin rashes, joint pain, fatigue and fever. It can persist for an extended period of time and is a wholly unpleasant experience. These diseases are carried by both salt-marsh and freshwater breeding mosquitoes.
The frequency of mosquito borne diseases has increased over the past year in South East Queensland. For example, the number of Ross River Virus infections has increased from 120 in 2014 to over 380 in 2015. There is a strong trend for the increasing frequency of infection by Ross River Virus in South East Queensland.
In the past year most of these incidents occurred in Brisbane metropolitan area (150 cases) and Gold Coast (77 cases). As more people move closer to mosquito breeding areas, it can be expected that the infection rates will increase unless effective steps are taken to reduce human exposure to biting mosquitoes.
Is DEET mosquito repellent safe for humans?
Generally, people need to modify their behaviour and clothing to reduce their exposure to biting insects. In addition the Queensland Department of Health recommends that the use of mosquito repellent containing DEET (chemical name, N,N-diethyl-meta-toluamide).
There are some concerns about the adverse effects of DEET on humans and people have been advised to minimise exposure to DEET.
It has been reported in the United States that DEET may cause severe skin irritation and in rare cases it has caused seizures in people, resulting in the death of a few. In another study, it was reported that National Park workers exposed to DEET were more likely to suffer from mood swings, insomnia and impaired cognitive function than co-workers not exposed to DEET. However, the American Environmental Protection Agency considers that the risk of using DEET 10-30% active ingredient is small compared the harm due to the diseases DEET is preventing.
Cost implications for the community
Development of a major residential development next to a mosquito breeding ground would increase the amount of spraying work that Redland City Council would have to undertake. This is acknowledged in the McGinn report which states: “The future residents and visitors of Shoreline Redlands will be dependent on Council’s management of mosquitoes in areas it controls.”
Who would be responsible for the other potential costs that might result if people residing or visiting this area were to contract any of the diseases transmitted by mosquitoes?
Any community costs resulting from location of a major residential development next to a major mosquito breeding ground should be fully considered by the Council as part of a comprehensive assessment process.
There has to be a better way!
The Redlands City mosquito fact sheet admits that Council’s control program will not kill all adult mosquitoes. Even with a control program, there is still a risk of people contracting mosquito borne diseases. As development encroaches on mosquito breeding areas, exposure of people to mosquito borne diseases will increase.
Council’s land supply study report found that Redland City has enough land already approved for residential development to meet likely needs for the next 25 years.
So why would Council seriously consider approving a major new residential development next to a major mosquito breeding area?
The Council is supposed to make decisions in the public interest. Increasing the risk of people contracting diseases from mosquitoes does not seem to be in the public interest.