Bumper mosquito season possible, according to researcher

Published:28 November 2017

CQUniversity Professor of Immunology & Haematology and Research Coordinator of Infectious Diseases, Andrew Taylor-Robinson, is predicting a worse-than-usual 2017/18 mosquito season.

Queenslanders could experience a bumper mosquito season this summer, thanks to an earlier and wetter-than-usual pre-season.

That’s according to CQUniversity Professor of Immunology & Haematology and Research Coordinator of Infectious Diseases, Andrew Taylor-Robinson.

“Mosquitoes require still, often stagnant water in which to breed, so mosquito numbers really take off after the seasonal rains,” Professor Taylor-Robinson explained.

“Typically in Australia the period when mosquitoes are most common coincides with the summer months. You may expect to see a mosquito any time between October and April. In 2017, however, Queensland has witnessed an unusually wet October with some regions registering the heaviest monthly rainfall on record. This means that now in late November, mosquitoes are starting to be seen in high numbers which is much earlier than in years that experienced a drier spring,” he said.

“If October was a prelude to a wet summer, then the prediction of it being ‘the worst mosquito season in history’ may come true.”

However, Professor Taylor-Robinson said more rain would be needed.

“For predictions of prolonged swarms to be validated, plenty more rain during and after the Christmas and New Year holiday period will be required,” he said.

Professor Taylor-Robinson said any region that had experienced significant rain could expect potential mosquito outbreaks.

“As a general rule, drier regions, where there is less rainfall over the summer, will experience fewer mosquitoes and therefore will have less pest problems as well as a reduced risk of the diseases that they may carry,” he said.

“So, what regions experience worse outbreaks will depend on the pattern, volume and duration of rainfall.

“Land that is in a river basin catchment area will see run-off water from areas further up-river, which may lead to an increased risk of flooding that is not related directly to the volume of rainfall that it has experienced. Flooding certainly leads to problems since the slow drainage affords an opportunity for mosquitoes to lay eggs in places they might not otherwise. Usually, eggs are deposited in clusters – called rafts – on the surface of stagnant water. Eggs can hatch in as little as a couple of centimetres of standing water.”

Professor Taylor-Robinson said while there were about 80 well-characterised species of mosquitoes that live in Australia and ‘probably a couple of hundred more that have not been identified in any great detail’, people could expect to see only a few varieties buzzing around this summer that cause real problems.

“Only a few, around a dozen, are known to carry pathogens, usually viruses such as Ross River and other so-called neglected arboviruses, that can cause infection when passed to humans,” Professor Taylor-Robinson explained.

“Of course, regardless of the species there is an irritant value to mosquitoes, since almost all species bite with the aim of taking a blood meal (if undisturbed, a mosquito can drink up to three times its weight in blood; it would take about 1.2 million bites to drain all the blood from your body!). In fact, in each case, it is only females that feed on blood, in search of protein which they need for egg production. They can lay up to 300 eggs at a time, while males are ‘tee-total’, usually drinking plant sap and nectar only.”

Which leaves the burning question for Professor Taylor-Robinson, who’s studied mosquitoes and their consequential diseases for over two decades - how can people best protect themselves from being bitten this season and contracting mosquito-borne diseases?

“Mosquitoes have caused more human deaths than any other animal, so don’t get bitten in the first place!

“There are several common-sense personal protection measures that can be taken to reduce the risk. First and foremost, wearing clothing to cover arms and legs. Of course, given the climate, this is often impractical, in which case correctly applying mosquito repellent to exposed areas of skin, and if possible avoiding going outside at dawn and dusk when some mosquito species like to bite,” Professor Taylor-Robinson explained.

“If you know you’re going to a mozzie-infested area, it is a good idea to take the added precaution of opting for light clothing since dark colours attract mosquitoes as they are drawn to heat and darker clothes retain more heat than does light-coloured clothing. Those staying closer to home may be reassured to hear that mosquitoes are disturbed by air conditioning and fans because they like to settle to feed in still air, not a breeze.”