The Asian tiger mosquito is on our doorstep

IT'S aggressive, its bite causes fever and excruciating pain and it's on our doorstep. Can the Asian tiger mosquito be stopped?

IN 2005 Peter Moore, a young honours student at the University of Queensland, was dispatched to the Torres Strait with a team to trap mosquitoes.

The islands are home to a number of species and researchers wanted to find out if they were capable of transmitting the debilitating dengue fever. Moore and his team diligently set up their traps in dark, moist places and found a bunch of mosquito species, including one they couldn't identify, and so they took it back to scientists in Cairns. To their horror they identified it as Aedes albopictus, the Asian tiger mosquito, No.4 on the Global Invasive Species Database's list of the World's 100 Worst Invasive Alien Species.

Since it began its relentless expansion out of Asia to North and South America, Africa, Europe and the Middle East a few decades ago, spread mainly in the warm, moist environment of second-hand tyres that are shipped around the globe, Aedes albopictus has been responsible for immense misery. It is a vector for a number of tropical diseases such as dengue fever and chikungunya, which causes excruciating joint pain and fevers for weeks, months, sometimes years. Just when the mosquito was discovered in the Torres Strait, Reunion - a French island in the Indian Ocean, east of Madagascar - was in the midst of a chikungunya epidemic spread by albopictus. More than 250,000 people, almost a third of the population, were infected. It devastated the island's economy and tourism industry and completely swamped its medical system. The French Government sent emergency aid worth $60 million and 500 soldiers to battle the mosquitos.

So when albopictus was discovered in the Torres Strait, Queensland Health immediately sent troops armed with insecticide and clipboards to spray and to see how widely the mosquito had spread. They found 10 islands had been infested. Initially it was thought albopictus had found its way to the islands through Papua New Guinea; however, Nigel Beebe, a mosquito biologist with the University of Queensland and the CSIRO, says that when they "drilled down into the DNA" they found the Torres albopictus had come from Indonesia. "We learnt that during the early 2000s there was a lot of illegal shark-fin fishing in the area. Indonesian poachers would come over in high-powered speed boats and park up on the islands to store their nets, water and their catch." Inadvertently, they were probably seeding the islands with the Asian tiger mosquito.

Since then, Queensland Health has been conducting an aggressive spraying and inspection program on the islands. But, as Beebe points out, history suggests it's only a matter of time until the mosquitos develop a resistance to the insecticides. Then what? So far, this program has cost about $5 million; if the mosquito reaches the mainland, the cost of containment will rise to many tens of millions of dollars.

It is not just from the north that the invasion could occur. In the past 10 years the Asian tiger mosquito, or its eggs or larvae, has been discovered in Melbourne, in shipments of lucky bamboo from China; in Brisbane, in the anchor well of a boat imported from the US; in Townsville, lurking in tyres imported from PNG; in Darwin, among steel cables from Timor Leste; in Cairns, on a boat shipped from PNG ... on at least 35 occasions it has made its way to the mainland to be intercepted and destroyed by Department of Agriculture inspectors.

Unlike other mosquitos that spread tropical diseases, such as Aedes aegypti - responsible for regular dengue fever outbreaks in northern Queensland - the Asian tiger mosquito does not need tropical conditions to survive. It's an all-rounder and thrives in urban environments. A recent study, published in Austral Ecology, found the mosquito could spread right down the east coast to Tasmania.

As its name suggests, it is a mean and aggressive feaster that bites its victim many times. Its bite is particularly painful and while other mosquitos bite at dawn and dusk, albopictus bites from dawn until dusk - they call it the Barbecue Stopper. "In places where this mosquito has spread it has really affected their alfresco lifestyle," Beebe says. "I have a colleague who lives in Atlanta [in the US], which has been invaded by albopictus, and he says that on a summer day you can get 50 mosquito bites in 15 or 20 minutes. It is so aggressive that it just forces people to stay inside."

There have been studies conducted overseas which have linked the invasion of albopictus to an increase in childhood obesity as children stay indoors to avoid the vicious little bloodsuckers. You don't make the list of World's 100 Worst Invasive Alien Species being a pussy (unless, of course, you are Felis catus, which comes in at number 38).

In April last year Juliet Corley, a marine biologist and illustrator from Cairns, flew to West New Britain, an island in Papua New Guinea, where she was working on a project preserving local reefs. She'd lived and worked in the tropics and was conscious of covering up and applying mosquito repellent. However, one afternoon she was bitten on the elbow by a mosquito - almost certainly an albopictus. She remembers it clearly because it was so painful and then, soon after, spots and a rash started to appear. Two days later she felt dreadfully ill, with a raging temperature and aching joints. Fearing she may have meningitis, she saw a local doctor who diagnosed two forms of malaria (contracted by an earlier mosquito bite in PNG) and said she probably also had chikungunya, which is closely related to Ross River virus. He wrote a referral letter and Corley flew back to Cairns. She was tested for malaria and urged doctors to test her for chikungunya, but none of them had heard of it. Eventually a test was done and three weeks later Queensland Health workers phoned; they wanted to spray her house for mosquitos. "They said, 'We've been told you have chikungunya'. I said, 'That's nice because nobody has told me yet'."

Corley has kept a diary since her illness - she calls it her diary of misery. For about two months the pain in her ankles was so severe it felt as though she'd sprained them; at other times that pain would move to her wrist or shoulder or neck. She got terrible headaches and pins and needles in her arms. At times she got depressed and lethargic and could only walk a few hundred metres. In supermarkets she'd have to use the trolley as a Zimmer frame to get around. Things have now improved, somewhat, but she still has her bad days. "It's been months of utter hell."

Corley is one of 126 Australians - a record number, up from just 19 the previous year - who returned from overseas in 2013 with chikungunya from places such as Indonesia, India, Malaysia and PNG, where there is now a serious epidemic. All that is required for an outbreak of chikungunya here is for one of these people to be bitten by the tropical mosquito Aedes aegypti; the mosquito would then be able to pass it on to other humans. Aedes aegypti exists in the north of Australia, down to just 250km north of Brisbane, restricting the diseases it transmits to the tropics. However, if albopictus invades, there's a potential for an outbreak of chikungunya, or dengue, in Brisbane, Sydney, Melbourne or Perth. The costs to the public purse of such an outbreak could be astronomical. But imagine, too, the costs to the Queensland economy if an outbreak occurs in one of its tourist towns.

While this is not an issue that has sparked great public or political interest, scientists in Queensland have been digging away in the trenches for a number of years, attempting to fortify our defences. A CSIRO project team is using complex algorithms to predict where the mosquito may invade and how our resources may best be deployed to combat it. "I think that it is inevitable that albopictus will turn up," says Dr Paul De Barro, an expert on biosecurity at the CSIRO. "It's already been knocking on the door, we've had a number of interceptions, we are a trading nation and so we are going to have to deal with it." A team from the CSIRO, in conjunction with economists from the Australian National University, is working on a "contingent valuation analysis" to inform the public, and the politicians, of the costs of a full-blown Asian tiger mosquito invasion: how it would affect our economy, our tourism industry, our house prices and our alfresco way of life. "We have never seen a mosquito as aggressive as the Asian tiger that occurs in such large numbers and likes humans - it could severely affect the way we live," says De Barro. "We want to mount an economic case so that if there is an incursion we have the capacity to respond effectively and early." So far, he says, no politician has come on board to champion the cause.

At the same time, researchers are working on a number of biological controls to try to combat the spread of albopictus, but these are some years away. There is a technology available now that could possibly wipe out albopictus in the Torres Strait; it just happens to be controversial - genetically modified mosquitos, specifically engineered to kill off the species. It's in the armoury now, awaiting mobilisation.

Professor Luke Alphey is a visiting fellow in zoology at Oxford University and the founder of Oxitec, a company at the forefront of developing genetically modified insects. Oxitec has engineered a male mosquito which, when it mates with a "wild" female, causes a defect in the flight muscles of her female offspring - they can't fly and either drown, get eaten by ants or starve. Only male mosquitoes are released (the males don't bite) and are easy to breed, which means they can be released in large numbers, overwhelming their wild competitors. Essentially, it is using mosquitos to destroy themselves.

Successful trials have been conducted in the Cayman Islands, Brazil and Malaysia, with suppression rates above 96 per cent and higher in "closed environments" such as those that exist on islands in the Torres Strait. It is a technology that has broad support among scientists working in the field. "It's another tool to help us fight this mosquito," Beebe says. "They've been bombarding the malaria mosquito in Africa for years with insecticides and now their main malaria mosquito is very insecticide-resistant. We don't want to be in that position." He describes the Oxitec mosquito as an "elegant" control method.

Scientists in Queensland are considering the option to combat albopictus, but they have yet to submit an application to the Office of the Gene Technology Regulator for approval. And they would need to conduct extensive community consultation, too. In Florida, when there was a major outbreak of dengue fever in 2009, the Florida Keys Mosquito Control District looked at introducing GM Oxitec mosquitoes to combat Aedes aegypti but the proposal was scuppered by staunch resistance, including claims that the scientists were "playing God" with their "Robo-Frankenstein mosquitoes".

"It is always a tradeoff," Beebe says. "The risks need to be evaluated, but that also needs to be weighed against what would happen if albopictus made it to the mainland and what that would mean."

Bob Phelps, who heads the campaign group Gene Ethics, says it is "inevitable" that, once released, genetically modified insects would go beyond recall and have an adverse effect. "Deficiencies in ecological and evolutionary knowledge make it essential that GM mosquito research not proceed," he insists.

The scientists know there is a significant lobby opposed to GM, no matter how rigorous the scientific testing. Several I spoke to said they felt they may also have problems releasing genetically modified mosquitos in the Torres Strait as the locals may see it as "experimenting on the indigenous".

However, the Mayor of Torres Strait Island Regional Council, Fred Gela, says he thinks islanders would welcome anything that could reduce disease. Gela says he is acutely aware of the dangers of chikungunya and the devastating effect it is having in PNG, just to the north. "We live with tropical diseases, we know how terrible they can be," he says. "We are the guys on the front line."