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Mosquito 'explosion' predicted after wet spring, experts warn to cover up

Sunday November 21, 2021 - 19:54 AEDT

It's been a wet spring, and November may turn out to be one of the wettest on record. 


The Bureau of Meteorology is predicting summer will also bring above-average rainfall for parts of the eastern states, and a 70 per cent chance of La Niña forming in the coming months.


With waterways swelling, David Bock from the Australia Museum told ABC Radio Hobart it would be perfect conditions for mosquitoes.


"When you get a lot of standing water and the warmer weather, you will get mosquito numbers exploding," Mr Bock said.


"Mosquitoes are a species that can breed up very quickly.


"But it can also lead to big numbers of species that eat mosquitoes."


Mr Bock said it wasn't just water that was needed for mosquitoes to thrive, but warm temperatures as well.


The cold snap Tasmania recently experienced with snow almost down to sea level would have killed off larvae, he said.


In other areas of Australia where it has been warm, he noted the situation is very different.


"It's a perfect opportunity for a population explosion," he said.


The mosquito life cycle


Mr Bock said mosquitoes lay eggs on stagnant water and the nymphs or "wrigglers" have an aquatic stage in their life cycle.


The larvae are up against predators like frogs, fish and other insects.


"When there's lots of food around, the predators do well as well," he said.


When there is lots of water on the ground and in gutters and backyard plant containers, mosquitoes have opportunities to avoid predators and quickly multiply.


"That's when you'll get the population booming when there's a lot of freestanding water," he said.


The wrigglers spend about a week in the water before being able to fly off.


If the water dries up, they die.


Only females bite


Mr Bock says only a small portion of mosquito species are out looking for blood.


"There are many species of mosquitoes, and many aren't pests at all," he said.


"Most drink nectar and sugar off flowers and plants."


Of the species that do want blood, it is only the females who bite.


"In a world without people, these mosquitoes would have fed off birds and mammals."


"But humans happen to be another source of nutrition for these females."


He says disease becomes a problem when mosquitoes feed on multiple sources of blood, and blood gets mixed between humans and animals.


Mosquito-borne diseases


Ross River virus is the most common mosquito-borne disease and can be found everywhere in Australia but is most prevalent in Queensland, the Northern Territory and the Kimberley region of Western Australia.


Public health physician Rod McClure told ABC Sunshine Coast symptoms develop about 10 days after a bite and can last for months.


"Some people don't develop symptoms at all, but quite a few have flu-like symptoms, fever, chills and headaches associated with rashes and aches and pains in joints," he said.


He said joint stiffness could become debilitating.


Dr McClure says there is no specific treatment for Ross River virus, but its symptoms can be managed.


The biggest risk of getting the virus is over summer.


"It's starting to increase now so we are just before the rise, and from January to March you see a dramatic escalation and then it returns to baseline," he said.


Protecting yourself


Dr McClure encouraged people to install and maintain fly screens, use insect repellent outside and be conscious of mosquitoes in the early morning and evenings.


"Protect your skin with clothes the mosquitoes are unable to bite through," he said.


He said loose and long light-coloured clothing was best.


"Barrier protection is a lot better than chemical protection."


The Barmah Forest virus is also found in most regions of Australia and has similar symptoms to Ross River virus.


Malaria and dengue fever are not transmitted in Australia, with all cases coming from overseas.







- ABC

© ABC 2021

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