CSIRO scientist and mosquito expert, Dr Brendan Trewin, explains the latest in mosquito research and offers advice on managing mosquitoes in and around the home.
Is Australia in for a “monster” mosquito season?
It is true that large mosquito numbers occur after significant rains. In Australia there are over 300 mosquito species and some of these species flourish in flood waters, so it’s quite possible we could see large mosquito numbers this season.
What’s causing this? Is La Niña to blame?
La Niña conditions in Australia increase the risk of mosquito bites and sometimes the spread of diseases like Ross River fever and Murray Valley encephalitis.
Are we seeing more mosquito-friendly habitats in Australia? Why is this?
Over the past 50 years we have seen a large increase in human populations and urban spread across the globe. This rapid expansion has resulted in large epidemics of diseases spready by invasive species like the dengue mosquito (which only live around humans) or the Asian tiger mosquito.
In Australia climate change is making areas like Sydney and Melbourne more receptive to invasive mosquito species and therefore the diseases they spread. Rainwater tanks have been installed throughout Australian cities in response to drought and water shortages, and these invasive mosquito species thrive in water tanks. If you have a water tank it’s important to make sure it doesn’t turn into an accidental breeding ground for mozzies.
How can we ensure water tanks do not become a mosquito breading ground?
CSIRO research found that 70 per cent of mosquito larvae survived to adulthood during winter in water tanks. Maintaining water tanks is important with these simple steps:
- Check there are sieves at the entrance and overflow and there are no gaps
- Clean entrance and overflow sieves regularly
- Look for cracks in plastic or holes rusted in metal tanks
- Make sure the sieves aren’t rusting and there are no holes
- Keep gutters clean as mosquitos feed on broken down leaves
- Check that first flush devices are draining fully.
What can we do to protect ourselves from mosquitoes this summer?
Peak mosquito biting hours are around dawn and dusk. During these times personal or topical repellents (like CSIRO-invented Aerogard), or those containing low concentrations of N,N-Diethyl-meta-toluamide or DEET, are the best applied to the skin to stop mosquito bites.
Mosquito coils are good for keeping mosquitos at bay in an outdoor setting but should not be used in unventilated areas.
Clothing such as long sleeves and long pants will minimise bites on arms and legs but any exposed areas of skin should still have topical repellents applied.
One of the most effective ways to prevent unwanted mosquito bites and annoying mosquitoes is to use fly screens on windows and doors.
Airconditioning has been shown to be effective in reducing the burden of dengue during disease outbreaks overseas by ensuring people are inside during daytime areas and not exposed to infected mosquitoes.
One of our favourites is the good old pedestal fan – using one of these at night ensures airflows that mosquitoes are unable to fly through!
Is it true some mosquitoes find some people’s blood “sweeter” than others?
There is mixed evidence to show the attractiveness of one blood type over another so at this stage it’s still inconclusive whether blood type influences attractiveness.
What we do know is that the smell of certain people’s skin is more attractive than others. This is likely to be a combination of blood, metabolic by-products, and bacteria on the surface of the skin. For instance, there are certain species of mosquitoes that love the smell of the bacteria in stinky socks! This includes the dengue fever mosquito which loves biting humans on their ankles.
Are all mosquitoes dangerous? Which ones should we be concerned about?
Apart from being annoying and causing itchy bites, most mosquitoes are harmless. However, the mosquitoes we should be most concerned about are those that spread disease. Invasive species such as the mosquitoes that carry dengue, Zika and chikungunya are increasingly problematic.
Out of the 3500 species of mosquito around the world, only a handful of those are deadly. It is these deadly mosquitoes that we are targeting with next generation mosquito control, to protect both Australian and vulnerable communities in other parts of the world.
In Australia, the deadly mosquitoes we should be most concerned about are the Asian tiger mosquito (Aedes albopictus) and the dengue fever mosquito (Aedes aegypti). Ross River fever carriers such as the Australian saltmarsh mosquito Aedes vigilax and the common banded mosquito (Culex annulirostris) are the next line of concern.
Which invasive/exotic mosquito species are already in Australia, or on our doorstep?
The Asian tiger mosquito is aptly known as the barbecue stopper in places like Italy and the United States where it has become a pest. With its habit of constant biting (unprotected, you could be bitten 20 to 100 times an hour) along with its ability to survive in cool climates, it is no wonder this mosquito has earned its name as the barbecue stopper.
There is growing concern that this mosquito will arrive and establish in Australia, it has been caught in mosquito traps at most Australian seaports and some airports. It’s also in the Torres Strait but so far our biosecurity and health systems have kept it out of mainland Australia.
What research projects is CSIRO involved in to help manage mosquitoes?
With our partners we have proven the effectiveness of Wolbachia, an environmentally friendly biological control, by eliminating a population of the dengue mosquito. Based on this success, dengue is no longer a problem in north Queensland.
CSIRO will trial the same technologies as a way to eliminate the Asian tiger mosquito in case it does establish in Australia. Working with Australian industry, universities and research institutes, CSIRO is developing innovative methods which don’t require insecticides and are highly targeted to the species.
Ross River fever, spread by the saltmarsh mosquito, is now the biggest mosquito-borne disease in Australia impacting the lives of over 4,000 people each year. CSIRO and our partners are looking at new technologies to suppress the saltmarsh mosquito and protect Australian communities who are vulnerable to large outbreaks of this disease.