CSIRO makes major breakthrough in fight against killer mosquito diseases

Science research agency CSIRO says it could soon drastically ­reduce the population of mosquitoes that cause dengue, zika, yellow fever and chikungunya.

Science research agency CSIRO says it could soon drastically ­reduce the population of mosquitoes that cause dengue, zika, yellow fever and chikungunya.

In a first for the southern hemisphere, researchers have shown a bacteria can successfully sterilise and eradicate the invasive, disease carrying Aedes aegypti mosquito which is responsible for spreading the diseases.

In a peer-reviewed paper published today in the National Academy of Sciences of the United States, CSIRO and its partners sterilised three million male mosquitoes with bacteria called Wolbachia and released them into three town regions in northern Queensland in the summer of 2018.

More than 80 per cent of the mosquito population was suppressed across the three trial sites over the 20 weeks of the project.

When scientists returned the following year, they found one of the treated trial sites, Mourilyan in Queensland, was almost devoid of mosquitoes.

CSIRO research scientist Brendan Trewin said mosquitoes remained substantially suppressed at the second site and while the population at the third site had recovered, this was due to mosquitoes from other areas migrating into the test area and eggs. “There were obviously eggs still in that environment,” he said.

The three sites were compared to three other sites where sterilised mosquitoes were not introduced.

He said if the program was conducted widely and repeatedly, entire populations of the common Aedes aegypti aka the yellow fever mosquito and dengue fever mosquito could be all but eradicated.

CSIRO partnered with University of Queensland, Verily Life Sciences, QIMR Berghofer Medical Research Institute and James Cook University on the project.

Mosquito varieties and the diseases they carry. Source: CSIRO

Dr Trewin said this technique of control was more effective and efficient than the current radiation method which reduced the “fitness” of mosquitoes placed back into communities to breed with “wild females”.

Instead of releasing 9000 males per hectare sterilised using radiation, you could release around 1500.

“It‘s highly targeted, we’re not using insecticides to do this so we’re not affecting all insects in those areas. We’re hoping this is more of a long-term solution for areas that do have isolated populations so that’s why the three towns were perfect,” Dr Trewin said.

He believed the technique involving bacteria could be researched and adapted to the other major sources of the same four diseases, Aedes albopictus, or the Asian Tiger mosquito which is threatening to enter Australia from the Torres Strait and from shipping.

Dr Trewin said the next step was to work out the optimal way of wiping out a whole mosquito population as you moved through a city.

He said one project partner Verity Life Sciences was already working with the Singapore government to implement it on a citywide basis.

Dr Trewin said the bacteria sterilisation technique could be adapted to the Asian tiger mosquito which was another major carrier of the same four diseases, exhibited the same reproductive behaviour and was on Australia’s doorstep.

“Once an incursion gets to a larger site, say, a suburb size in Brisbane, it‘s going to be pretty hard to get to keep it under control with insecticides, and that’s why we’re looking to develop these sort of more efficient tools.”

He said the Asian Tiger mosquito migrated at about 200 metres per generation (up to two weeks), had invaded Europe in the 1980s, was spreading across the US and nearing the English Channel, on the doorstep of the UK.

So eliminating these two mosquito species would have a major impact on the incidence of Dengue, Zika, yellow fever and chikungunya. He described the other sources of those diseases as only “secondary vectors”.

He believed the Wolbachia bacteria approach could also be used to reduce populations of other mosquito species responsible for Ross River fever, Barmah Forest, Murray Valley encephalitis and Kunjin.

CSIRO chief executive Larry Marshall said the organisation was proud to build on its 100-year legacy of protecting Australia and Australians while James Cook University Adjunct Professor Scott Ritchie said the Wolbachia trial had seen contemporary science working together with cutting-edge technology,

Verily product manager Nigel Snoad said community engagement was also essential to the project’s success.