The Best Australian Science Writing 2012 (29 page)

The life-shortening effect was irrelevant;
Wolbachia
effectively immunised the mosquitoes.

And there was more: ‘When you look at all the different mosquitoes, it's only the ones that don't have very strong
Wolbachia
infections that transmit disease,' says O'Neill. ‘The nuisance mosquitoes that just bite you, many of them have
Wolbachia
. Perhaps
Wolbachia
had been determining which mosquitoes were vectors and which weren't. Perhaps putting
Wolbachia
into a mosquito that is a vector was quite a natural thing, and we were just helping it along.'

Fortuitously, there was indeed a type of
Wolbachia
that blocked dengue without shortening the mosquitoes' lives and affecting their ability to breed through the dry. The strain, called wMel, had been discovered by Hoffmann in 1988, when he tried crossing
fruit flies from Townsville with fruit flies from Melbourne. ‘It's an Aussie,' Hoffmann laughs, ‘and it came out of your fruit bowl. That's where we sourced the flies.' Thomas Walker, a postdoctoral researcher in Scott O'Neill's lab, established it in
Aedes aegypti
mosquitoes ‘in about a month', he reckons, ‘from four or five days' injections'.

And so McMeniman's thousands of injections weren't ultimately part of the solution. He's pragmatic, albeit slightly wistful: ‘It's bitter-sweet, I guess. I spent four or five years of my life working towards the project's aim: these experiments are fairly labour-intensive, they're very technically demanding, and they're not very good for your social life. But we're a team in the end – and what both Tom and I did was really, really cool.'

Driving out from the Eliminate Dengue shopfront in central Cairns towards his office at James Cook University, Professor Scott Ritchie is talking about those two huge field cages, 20m long, purpose-built for the
Wolbachia
project. ‘If our old cages were three-star accommodation for mozzies,' he says, ‘then these are the Taj Mahal.'

An ebullient American and a self-described ‘quarterback' against mosquito-borne disease in this part of the world, Ritchie arrived in Australia in 1994 and took ‘a dengue-related job' in Cairns with Queensland Health. ‘It's real
aegypti
country,' he says. Far North Queensland was fast becoming Australia's dengue hot spot, and by 1998, the region had a Dengue Action Response Team (DART) mandated to enter properties and treat
Aedes
breeding sites (anywhere that holds water, such as a potplant holder or the cupping leaves of a bromeliad; anywhere that's dark, such as under a bed) with insecticide.

While this approach has successfully stemmed more than 30 dengue outbreaks, ‘We're ticking the milestones to dengue becoming endemic in North Queensland unless an alternative strategy comes on board,' says Brian Montgomery, Eliminate
Dengue's field trial manager. It's just one reason, says Ritchie, why governments would find a control strategy like the
Wolbachia
project ‘very sexy'.

It's quiet inside the cages, quiet and surprisingly still. Petrina Johnson, who oversees the mass production of the mosquitoes, shows me the cage where they fly free, feeding on volunteers to lay eggs for the releases.

‘
Aegypti
have a really close association with humans,' Johnson explains, ‘so for some earlier experiments, rather than sit here all the time, we made it smell human – we collected used gym towels and left them here. It smelt awesome, all dank and stinky …' In the second cage, mosquitoes are prepared for release, and every week Johnson delivers 12,000 mosquitoes, each four to six days old, to Brian Montgomery's release team (6000 for the northern Cairns suburb of Yorkeys Knob, 6000 for Gordonvale, south of Cairns). ‘We make another 6000 or so as a back-up. We're just a mosquito factory,' she says, laughing.

For most people in Australia, dengue is an exotic disease with no bearing on day-to-day life. But for the residents of Far North Queensland, it's an immediate, alarming threat. ‘Many have had dengue before and are very fearful of having it again,' says O'Neill. ‘Whatever they think of DART forcibly entering houses to spray insecticides under beds, in closets, major dengue outbreaks are still occurring. So people are very keen for something new to be done.' More than half the residents in the two trial sites are happy for the team to release mosquitoes on their properties.

At a community engagement breakfast, representatives from those suburbs, and from Cairns's tourism industry – always heavily affected by reports of dengue – hear the latest about the trial.

‘The story is simple,' says the tourism industry rep. ‘Eliminate dengue and there's an economic benefit – that's what you're doing; that's it.'

Along the table, Scott O'Neill demurs, ‘I'm looking for wood
to touch. I don't want to over-promise and under-deliver. We're still a long way upstream.'

Out in the field, the team distributes small black buckets lined with red felt in which they hope mosquitoes will lay eggs that show that the
Wolbachia
infection is beginning to spread. At the house of the project's first release, they weigh up locations for these traps – under a table, next to a door – while the owner jokes about it being
Wolbachia
's ground zero. ‘There'll be a plaque on the fence,' someone suggests. ‘There'll be tours.'

‘If it works,' laughs the homeowner. ‘If it works.'

Four weeks later, the eggs collected from those traps are analysed. There's
Wolbachia
in 20 per cent of them. ‘That's what our models had predicted it would be,' says O'Neill, ‘so it's on the money.' It's also the point from which the models – designed by Ary Hoffmann and Michael Turelli, working together again more than 20 years after they watched
Wolbachia
spread across California – suggest the bacteria will drive itself through the population.

‘If it continues that way, we think the release should be successful,' says O'Neill. ‘We're getting quietly confident.' In March, the time of the last releases, the level had reached about 70 per cent.

And now, what next? The trial in Cairns is funded for two years; a successful release this year may see another rolled out in less isolated areas in 2012. Regulatory approval is being sought for field releases in Thailand and Vietnam. And Scott O'Neill has just moved to Victoria's Monash University to become their dean of science, taking his lab, and this project, with him.

Plus there's the small matter of malaria. ‘The Gates people are really interested in malaria, more than they are in dengue,' O'Neill confesses. ‘So they're saying, “Fantastic, Scott, but can you do it for malaria?”' It's the million-dollar question – and the problem, again, is getting the infection into the mosquito. ‘
Aedes
mosquitoes have lots of close relatives with naturally occurring
Wolbachia
. But with
Anopheles
mosquitoes, which transmit malaria, no matter where you look in that genus,
Wolbachia
isn't there.'

At UQ, Thomas Walker estimated he'd injected 20,000
Anopheles
embryos ‘without success. It will require something novel, a novel technique or a breakthrough,' he says. ‘It's gone past the point of hard work and perseverance.' Around the world, several rival teams are on that hunt.

And up in Cairns, those dengue mosquitoes keep up their hard work of feeding and breeding in their comfortable cages, collaborating with the development of this subtle weapon to be used against their own kind.

Lateral thinking

Things that bite

Life in Lake Vostok? The link between Antarctica and extra-terrestrials

Helen Maynard-Casely

In early 2012, the Russian Arctic and Antarctic Research Institute (AARI) announced that they had successfully drilled into the elusive sub-glacial Lake Vostok, a body of water lying under nearly 4km of Antarctic ice. The breakthrough is the result of 20 years of drilling at one of the most inhospitable places on Earth.

Much of the interest in the 15,000 square-kilometre Lake Vostok revolves around the fact that any micro-organisms within it have been isolated for anywhere up to 30 million years, trapped in an environment similar to that of the moons of Jupiter.

So what does a sub-glacial lake in Antarctica have in common with the alien moons of Jupiter? And what's the significance of the Lake Vostok exploration when we consider the search for extra-terrestrial life?

Every time astronomers look at Jupiter with a different instrument they seem to discover a couple more moons. When I was a child I learned there were 16 moons – now there are 66, and I'm only 28. But it's the four largest of these moons that have attracted the most scientific attention.

They are now known as the Galilean moons, as they were discovered
by Galileo Galilei when he pointed his telescope towards Jupiter in 1610. The moons are named, poetically enough, after the lovers of Zeus (the Greek equivalent to Jupiter): Io, Europa, Callisto and Ganymede.

Most of what we know about the Galilean moons comes from an extremely successful NASA spacecraft. The unmanned Galileo spacecraft was launched in October 1989 and completed an eight year tour of Jupiter and its moons. That mission yielded images of the surfaces of the Galilean moons and spectral data showing the chemistry of their surfaces.

Among the many discoveries made by Galileo were the sulphur volcanoes of Io and a greater knowledge of Jupiter's massive magnetic field. Though Io is a sulphurous, inhospitable environment, the other three Galilean moons were found to have surfaces of water ice, with a number of other salty deposits.

Perhaps the most intriguing discovery was that under the icy crust of Europa lies what is thought to be a planet-wide ocean. This was detected because the salts in this ocean caused a change in the magnetic field of Jupiter as the icy moon moved through the field. Discovery of this ocean under 6–100km of ice highlighted the potential of a warm and mineral-rich playground – a viable place for life to flourish.

This was deemed so important that, at the end of its scientific life, the Galileo spacecraft was plunged into the clouds of Jupiter, to avoid the possibility of the craft hitting and contaminating the pristine environment of Europa.

The issue of contamination is chief on the minds of many scientists as drilling equipment plunges into Lake Vostok.

In the lead-up to the breakthrough, some scientists were concerned that liquid being used to stop the borehole from freezing over – a mixture of kerosene and other hydrocarbons – would leak into and contaminate the lake. The Russian scientists have refuted such claims, and the Antarctic Treaty Secretariat has
since ratified the drilling methods as well.

Discovering life in Lake Vostok would be a major scientific discovery. For a start, any organisms that live in the lake would have been trapped under the ice for millions of years. Such a discovery would also have significant ramifications for our understanding of the sub-surface ocean of Europa.

Any micro-organisms surviving in Lake Vostok could be an unknown form of life, and excellent candidates for what life on Europa might be like. The technology developed for the Antarctica project could be used to build a follow-up to the Galileo spacecraft – a craft that could land on Europa and burrow into the ocean.

Sure, a mission of this sort might still be many years away, but we are definitely heading in the right direction.

In the meantime, we'll await the results of the Russian drilling expedition and look forward to December, when a UK-led team starts to drill towards Lake Ellsworth – a similarly buried Antarctic lake. The UK team will be using a newly developed method of ‘hot-water' drilling, avoiding the use of kerosene completely and allowing for clean samples to be plucked throughout the drilling.

Stay tuned.

Expeditions

Moons

The doctor is in