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07 February 2019

Collecting mosquito poo may not be everyone’s idea of a dream job, but for AITHM research fellow and biologist Dr Dagmar Meyer Steiger it is a key ingredient in a new project which aims to significantly enhance surveillance of mosquito-borne diseases in northern Australia.

A member of AITHM's Health Entomology research group, she is developing and field trialling traps designed to catch female mosquitoes and harvest their excreta, which can then be analysed to detect a range of pathogens, including dengue, Ross River fever, Murray Valley encephalitis, West Nile virus and Malaria.

“You can capture and transport live mosquitos – which have to be kept cool at all times – to laboratories for analysis, or take regular blood samples from sentinel animals, usually chickens, placed in areas where a disease is thought to be circulating. But these methods are both expensive and time consuming,” observed Dr Meyer Steiger, whose current research is funded by a Hot North Early Career Research grant, from the Menzies Institute for Medical Research.

“It was found that viruses could be detected in mosquito saliva, but they only expel very small amounts, which makes detection difficult. So what other mosquito product could we collect that is provided in bigger quantities? The answer was excreta.”

Dr Meyer Steiger currently uses CO2, derived from dry ice or from gas bottles, to lure female mosquitoes into her traps, where honey-soaked cards provide a feast to encourage poo production. She also humidifies the traps with water-soaked sponges to keep the insects alive and comfortable.

Traps contain special filter cards or polycarbonate sheets to collect the excreta and preserve the viral RNA it contains for later laboratory analysis. The chemically-treated cards also de-activate viruses, to ensure safety in handling.

Despite Dr Meyer Steiger’s success in generating mosquito poo, the tiny excreta remained difficult to detect – until she came up with an eye-catching solution.

“We put blue food dye in the honey, so the excreta turned blue. If you look at mosquitoes that have consumed the honey, their bellies are actually blue, as well,” she said.

Dr Meyer Steiger has deployed her modified traps in both Cairns and Darwin. The collected excreta samples are then mailed to a Brisbane laboratory to verify the excreta can yield specific information on viruses carried by the mosquitoes. To date, analyses have detected Ross River fever, West Nile (Kunjin strain) and Murray Valley encephalitis viral RNA.

Her next goal is to simplify the traps, so they no longer require CO2 gas or a power source to operate, thus enabling the devices be cheaply produced and deployed on a large scale in even the remotest of locations in Australia.

“This research will significantly increase the surveillance capabilities of local governments for control of mosquito-borne diseases,” she observed.


Dr Dagmar Meyer Steiger

E. dagmar.meyersteiger1@jcu.edu.au

 

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