How to know if we’re winning the war on Australia’s fire ant invasion, and what to do if we aren’t


Fire ants like these can give a nasty bite.
Shutterstock/SweetCrisis

Daniel Spring, University of Melbourne and Jonathan Keith, Monash University

More than A$400 million of government funding is being invested in the latest round of the fire ant program in the hope of eradicating the invasive pests by 2027.

But recent reports on the ABC suggest the invasion is spreading beyond containment lines in south-east Queensland, and there are delays in responding to public reports of new ant infestations.

The claims are denied by Graeme Dudgeon, the new general manager of Queensland Government’s National Red Imported Fire Ant Eradication Program.




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Fire ants are native to South America but nests were first discovered in Brisbane in 2001. It’s thought they arrived via shipping at the Port of Brisbane.

They’re regarded as one of the world’s worst invasive species and have a painful bite which is why the Queensland Government has been trying to wipe them out here.

Is eradication possible?

An independent review in 2016 found the fire ants were confined to a region of south east Queensland and said there was an opportunity to eradicate the pests.

But the latest debate raises the question of whether eradication is the best plan, or would further containing the spread of the fire ants be a more practicable solution?

To achieve its aim of eradicating the fire ant problem, the program needs to progressively shrink the invasion.

If the invasion is shrinking too slowly (or is expanding), eradication won’t be achieved by 2027. Without ongoing monitoring of the invasion’s size, the program might be failing without the general public knowing.

But knowing the fire ant invasion’s size isn’t easy because there isn’t enough funding to survey all locations that might have them.

Estimates of the invasion

Using records of past fire ant detections, we have demonstrated how to estimate the invasion’s size when only part of the managed area is surveyed.

Our inference of the boundary of the fire ant invasion in April 2015. The different coloured polygons correspond to different levels of credibility that the boundary contains the invasion, with the outermost boundary corresponding to the highest credibility. Small crosses represent sites where nests have been detected, with the most recent detections in red and the oldest in brown.
Nature/Authors provided, CC BY

If this approach to estimating the invasion boundary is applied each year during the current program, we could estimate whether the invasion is shrinking fast enough to be gone by 2027.

The importance of this issue demands a rigorous scientific analysis using transparent data and methods. Without this, anecdotal evidence that the current invasion is spreading is all we have to indicate whether eradication efforts are failing.

The size of the fire ant invasion should not only be measured in terms of the total area within its estimated boundary but also the density of nests within this area.

Eradication won’t be achieved if both the invasion boundary and the density within it are increasing. This straightforward test to determine whether the program is failing has not yet been applied.

But such a test could be done if updated records of the fire ant invasion are regularly made available to allow for periodic estimation of updated maps of the invasion.

Never give up

Even if eradication by 2027 is unlikely, this does not mean we should give up, provided future control efforts can contain the invasion at an affordable cost.

If the current program fails to eradicate the fire ants, it may still set the stage for effective long-term containment of the invasion.

A poor outcome will result if current management efforts are spread thinly over the infested area, reducing the density of nests but not eradicating them from any suburbs.

A better outcome would involve shrinking the infested area, that is, eradicating the ants from many or most suburbs, so that subsequent containment efforts can focus resources on a smaller area.

Is it still early enough in Australia to shrink the fire ant invasion to a manageably small area and thereby protect most homes and most of the environment for a long time? The required information to answer this question is not yet available.




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But if Queensland’s eradication program has substantially slowed the spread so far, this provides confidence that continuing the program could effectively suppress the invasion. If so, we need to estimate what it will cost to keep out fire ants from most homes and most of the environment for a long time.

It’s often claimed that removing the last 1% of invaders costs as much as removing the previous 99%. If the current program removes all ants from most areas by 2027, this may provide large benefits without the extra cost of finding the last few ants in all infested areas.

Even if we do eradicate fire ants this time, it’s almost certain they will be back because they can readily hitchhike rides on ships.

So if governments can keep fire ant numbers down through ongoing containment, a lot of people and a lot of native species will benefit.The Conversation

Daniel Spring, Research Fellow, School of Biosciences, University of Melbourne and Jonathan Keith, Associate Professor, School of Mathematical Sciences, Monash University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Adani beware: coal is on the road to becoming completely uninsurable



Insurers have to protect themselves against foreseeable risks. For insurers of fossil fuel projects, those risks are growing.
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John Quiggin, The University of Queensland

The announcement by Suncorp that it will no longer insure new thermal coal projects, along with a similar announcement by QBE Insurance a few months earlier, brings Australia into line with Europe where most major insurers have broken with coal.

US firms have been a little slower to move, but Chubb announced a divestment policy in July, and Liberty has confirmed it will not insure Australia’s Adani project.

Other big firms such as America’s AIG are coming under increasing pressure.

Even more than divestment of coal shares by banks and managed funds, the withdrawal of insurance has the potential to make coal mining and coal-fired power generation businesses unsustainable.

As the chairman and founder of Adani Group, Gautam Adani, has shown in Queensland’s Galilee Basin, a sufficiently rich developer can use its own resources to finance a coal mine that banks won’t touch.




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But without insurance, mines can’t operate.

(Adani claims to have insurers for the Carmichael project, but has declined to reveal their names.)

Why are insurers abandoning coal?

By the nature of their business, insurers cannot afford to indulge the denialist fantasies still popular in some sectors of industry. Damage caused by climate disasters is one of their biggest expenses, and insurers are fully aware that that damage is set to rise over time.

Even so, a sufficiently hard-headed company might choose to work both sides of the street – continuing to do business with fossil fuel companies, while also writing more expensive insurance against climate damage.

The bigger problem insurers face is the risk of litigation holding fossil fuel companies responsible for climate-related damage. For the moment, this is a potential rather than an immediate risk.

As US insurer AIG, yet to announce a divestment policy, has observed:

Based on our monitoring, while the overall volume of litigation activity has increased, past litigation seems to have largely been unsuccessful on numerous grounds including difficulties in determining and attributing fault and liability to a particular company, and the judiciary’s deference to the political branches of government on questions relating to climate change.

Recent development suggest these difficulties will be overcome.

It’s becoming easier to finger climate culprits…

Until recently, the most immediate problem facing potential litigants has been demonstrating that an event was the result of climate change as opposed to something else, such as random fluctuations in climatic conditions.

Scientific progress on this “extreme event attribution problem” has been rapid.

It is now possible to say with confidence that climate change is causing an increase in both the frequency and intensity of extreme weather and weather-related events such as extreme heatwaves, drought, heavy rains, tropical storms and bushfires.

The Bulletin of the American Meteorological Society has highlighted three extremes in 2016 that would not have occurred if not for the added influence of climate change:

  • a persistent area of unusually warm water that lingered off the Alaskan coast, causing reduced marine productivity and other ecological disruptions

  • the extreme heatwave that happened in Asia, killing hundreds and destroying crops

  • the overall global atmospheric heat record set that year.

…and to allocate liability

The second line of defence against climate litigation that has held so far is the difficulty of imputing damage to the companies that burn fossil fuels.

While it is true that all weather events have multiple causes, in many circumstances climate change caused by the burning of fossil fuels has been a necessary condition for those events to take place.

Courts routinely use arguments about necessary conditions to determine liability.

For example, a spark from a power line might cause a bushfire on a hot, dry, windy day, but would be harmless on a wet cold day. That can be enough to establish liability on the part of the company that operates the power line.

These issues are playing out in California, where devastating fires in 2017 caused damage estimated at US$30 billion and drove the biggest of the power companies, PG&E, into bankruptcy.

As a result there has been pressure to loosen liability laws, leaving the cost of future disasters to be borne by Californians in general, and their insurers.

Lawyers will be looking for someone to sue.

Adani is a convenient target

The question facing potential litigants is whether any single company contributes enough to climate change to make it meaningfully liable for particular disaster.

Adani’s Carmichael mine provides a convenient example.

Adani says the 10 million tonnes of coal it plans to mine will produce only 240,000 tonnes of carbon dioxide, but this is semantic trickery. The firm is referring only to so-called “scope 2” emissions associated with the mining process itself.

When the coal is burned it might produce an extra 30 million tonnes of carbon dioxide, amounting to about 0.05% of global emissions.

A 0.1% share of the damage associated with the California fires is US$15 million, enough to be worth suing for. Other similarly sized mines will face similar potential liabilities.

Once a precedent is established, any company in the business of producing or burning fossil fuels on a large scale can expect to be named in a regular stream of suits seeking substantial damages.

When governments are successfully sued…

The remaining line of defence for companies responsible for emissions is the history of courts in attributing climate change to decisions by governments rather than corporations.

In the Netherlands, a citizen action group called Urgenda has won a case against the Dutch government arguing it has breached its legal duty of care by not taking appropriate steps to significantly restrain greenhouse gas emissions and prevent damage from climate change.

The government is appealing, but it has lost every legal round so far. Sooner or later, this kind of litigation will be successful. Then, governments will look for another party that can be sued instead of them.

…they’ll look for someone else to blame

Insurance companies are an easy target with deep pockets. Despite its hopeful talk quoted above, AIG would find it very difficult to avoid paying up if Californian courts found the firms it insured liable for their contributions to a climate-related wildfires or floods.

This is not a message coal-friendly governments in the US or Australia want to hear.

But the decision of Suncorp to dump coal, just a couple of months after the re-election of the Morrison government, makes it clear that businesses with a time horizon measured in decades cannot afford wishful thinking. They need to protect themselves against what they can see coming.




Read more:
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The Conversation


John Quiggin, Professor, School of Economics, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Adani has set a dangerous precedent in requesting scientists’ names



The Galilee waterhole is part of the area potentially affected by Adani’s Carmichael mine.
Stop Adani, CC BY-SA

Samantha Hepburn, Deakin University

A freedom of information request has revealed Adani sought the names of CSIRO and Geoscience Australia scientists involved in reviewing groundwater management plans related to its proposed Carmichael mine.

Adani argued it required a list of people involved in the review so as to have “peace of mind” that it was being treated fairly and impartially on a scientific rather than a political basis.

Ten days before Adani’s request, Geoscience Australia’s acting director of groundwater advice and data reportedly raised concerns that Adani had “actively searched/viewed” his LinkedIn profile and that of a colleague.




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Significantly, Adani’s request to the government was made before CSIRO and Geoscience Australia had reported their review findings back to the Queensland government.

While the federal Department of the Environment and Energy reportedly declined to hand over the names, the fact the letter was sent in the first place is concerning. It fundamentally interferes with the capacity of individual scientists to provide clear and informed evaluation.

The letter obtained under freedom of information by environmental group Lock The Gate. Click to enlarge.
Lock the Gate

Was Adani denied procedural fairness?

In the absence of clear legislation to the contrary, government decision-makers have a general duty to accord “procedural fairness” to those affected by their decisions. While procedural fairness is protected by common law, Commonwealth legislation also provides some protection, and a breach of procedural fairness is a ground for judicial review.

What exactly constitutes procedural fairness varies from case to case. Fundamentally, the principles of procedural fairness acknowledge the power imbalance that can arise between an administrative decision-maker and an individual citizen. Traditionally, procedural fairness has two elements: the fair hearing rule and the rule against bias.

The fair hearing rule requires a person – or company, in this case – to have an opportunity to be heard before a decision is made affecting their interest.

The rule against bias ensures the decision-maker can be objectively considered to be impartial and not to have prejudged a decision. This rule is flexible, and must be determined by reference to a hypothetical observer who is fair minded and informed of the circumstances.

There is no indication of any breach of procedural fairness in the environmental assessment process. The review of the groundwater management plan was conducted rigorously, according to the public interest.

The letter sent by Adani requesting the names of scientists was allegedly grounded in concerns about the possibility of anti-Adani activism by expert reviewers. Despite this, Adani made it clear that it was not explicitly alleging bias. Its objective, the letter said, was a desire to be “treated fairly and in a manner consistent with other industry participants”.

The real purpose of the letter

If Adani was seriously concerned about a breach of procedural fairness in the review of their groundwater management plan, it would have sought a judicial review. It did not – because there was no breach.

The scientists working at CSIRO and Geoscience Australia are all experts in their disciplines. They were engaged in the important process of determining whether Adani’s plan for managing groundwater around their mine would meet the environmental conditions of their mining licence. In other words, the scientists were doing their job.

Deputy Prime Minister Michael McCormack has said he “understands” Adani’s actions because of the delays associated with the review, but this is not how the system works.
The delays occurred because the original plan submitted by Adani had to be revised following expert review, and the updated plan required detailed evaluation. The mine could potentially have a serious impact on groundwater, the communities and ecosystems dependent on the water, and the nationally significant Doongmabulla Springs; this deserves careful scrutiny.




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As Adani has not brought an action for judicial review, the substantive purpose of the letter appears to be, as suggested by CSIRO representatives, to pressure scientists and potentially seek to discredit their work. The potentially chilling effect is clear.

Concern about climate change is not bias

The profound concerns raised by climate change and fossil fuel emissions are shared by many scientists around the world. The reports prepared for the International Panel on Climate Change make it clear that coal fired electricity must drop to nearly zero by 2050 to keep warming within 1.5℃.

This shared concern does not make scientists political activists. Nor does it prevent scientists from acting fairly and impartially when reviewing a groundwater management plan.




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An acceptance of climate science and even a belief that coal-fired energy should be decommissioned does not constitute bias. A reasonable bystander would expect most environmental scientists to be concerned about climate change.

It is crucial the environmental assessment process for large coal mines remains rigorously independent and absolutely free from any direct or indirect pressure from the coal industry. This is even more important when dealing with groundwater assessments, given their economic, social and ecological significance.

The letter, sent before the review was handed down, sets a dangerous precedent. Not because it suggests the scientists were impartial or there was any procedural unfairness involved in the process. But rather, because it jeopardises the independence of our scientists who, in seeking to ensure the longevity of our water, food and energy resources, carry a heavy responsibility to the public interest.The Conversation

Samantha Hepburn, Director of the Centre for Energy and Natural Resources Law, Deakin Law School, Deakin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

‘Sadness, disgust, anger’: fear for the Great Barrier Reef made climate change feel urgent



Tourists are experiencing ‘Reef grief’.
Matt Curnock, Author provided

Matt Curnock, CSIRO and Scott Heron, James Cook University

Media coverage of mass coral bleaching on the Great Barrier Reef may have been a major tipping point for public concerns around climate change, according to research published today.

Severe and extensive bleaching during the summers of 2016 and 2017 has been directly attributed to human-caused climate change. Much of the ensuing media coverage used emotional language, with many reports of the Reef dying.




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While the physical effects of the bleaching have been well documented, we wanted to understand the social and cultural impact.

Our research, including a study published today in Nature Climate Change, has compared survey responses from thousands of Australians and international visitors, before and after the bleaching event.

Reef grief

Our research team conducted face-to-face interviews with 4,681 visitors to the Great Barrier Reef region, in 14 coastal towns from Cooktown to Bundaberg, over June to August in both 2013 and 2017. We asked more than 50 questions about their perceptions and values of the Reef, as well as their attitudes towards climate change.

We found a large proportion of respondents, including Australians and overseas visitors, expressed forms of grief in response to loss and damage to the iconic ecosystem. Negative emotions associated with words given in short statements about “what the Great Barrier Reef means to you”, included sadness, disgust, anger and fear.




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Emotional appeals are widely used in media stories and in social media campaigns, and appealing to fear in particular can heighten a story’s impact and spread online.

However, a side-effect of this approach is the erosion of people’s perceived ability to take effective action. This is called a person’s “self-efficacy”.
This effect is now well documented in reactions to representations of climate change, and is actually a barrier to positive community engagement and action on the issue.

In short, the more afraid someone is for the Great Barrier Reef, the less they may feel their individual efforts will help to protect it.

While our results show a decline in respondents’ self-efficacy, there was a corresponding increase in how highly they valued the Reef’s biodiversity, its scientific heritage and its status as an international icon. They were also more willing to support action to protect the Reef. This shows widespread empathy for the imperilled icon, and suggests greater support for collective actions to mitigate threats to the Reef.

Researchers surveyed thousands of visitors to the Great Barrier Reef in 2013 and 2017.
Matt Curnock, Author provided

Changing attitudes

We observed a significant increase in the proportion of people who believe that climate change is “an immediate threat requiring action”. In 2013 some 50% of Australian visitors to the Great Barrier Reef region agreed climate change is an immediate threat; in 2017 that rose to 67%. Among international visitors, this proportion was even higher (64% in 2013, rising to 78% in 2017).

This represents a remarkable change in public attitudes towards climate change over a relatively short period. Previous surveys of Australian climate change attitudes over 2010 to 2014 showed that aggregate levels of opinion remained stable over that time.

Comparing our findings with other recent research describing the extent of coverage and style of reporting associated with the 2016-2017 mass coral bleaching event, we infer that this event, and the associated media representations, contributed significantly to the shift in public attitudes towards climate change.

Moving beyond fear

As a source of national pride and with World Heritage status, the Great Barrier Reef will continue to be a high profile icon representing the broader climate change threat.

Media reports and advocacy campaigns that emphasise fear, loss and destruction can get attention from large audiences who may take the message of climate change on board.

But this does not necessarily translate into positive action. A more purposeful approach to public communication and engagement is needed to encourage collective activity that will help to mitigate climate change and reduce other serious threats facing the Reef.

Examples of efforts that are underway to reduce pressures on the Reef include improvements to water quality, control of crown-of-thorns starfish outbreaks, and reducing poaching in protected zones. Tourism operators on the Reef are also playing an important role in restoring affected areas, and are educating visitors about threats, to improve Reef stewardship.

Clearly there remains an immediate need to reduce greenhouse gas emissions to ensure the Reef’s World Heritage qualities are maintained for future generations.

However, maintaining hope, and offering accessible actions towards attainable goals is critical to engaging people in collective efforts, to help build a more sustainable future in which coral reefs can survive.


The authors would like to acknowledge Nadine Marshall, who co-wrote this article while employed by CSIRO. We thank our other co-authors of the Nature Climate Change paper, including Lauric Thiault (National Center for Scientific Research, PSL Université Paris), Jessica Hoey and Genevieve Williams (Great Barrier Reef Marine Park Authority), Bruce Taylor and Petina Pert (CSIRO Land and Water) and Jeremy Goldberg (CSIRO & James Cook University). The scientific results and conclusions, as well as any views or opinions expressed herein, are those of the authors and do not necessarily reflect those of the Australian Government or the Minister for the Environment, or the Queensland Government, or indicate commitment to any particular course of action.The Conversation

Matt Curnock, Social Scientist, CSIRO and Scott Heron, Senior Lecturer, James Cook University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Adani’s finch plan is approved, just weeks after being sent back to the drawing board


Stephen Garnett, Charles Darwin University; Brendan Wintle, University of Melbourne; David Lindenmayer, Australian National University; Don Franklin, Charles Darwin University, and John Woinarski, Charles Darwin University

The Queensland government has ticked off a crucial environmental approval for Adani’s Carmichael coalmine, bringing the contentious project a step closer to becoming reality.

It has approved Adani’s proposed management plan for the endangered black-throated finch, less than a month after the state’s environment department announced a delay in approval because the plan was judged to be inadequate.




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Four days after the May 18 federal election, in which the mine’s future was a prominent issue, Queensland Premier Annastacia Palaszczuk called for an end to the delays and uncertainty.

In a statement issued today, the government said it has now approved a “strengthened” version of the plan, submitted by Adani earlier this week.

Under the revised plan, Adani has now committed to:

  • “establish enhanced understanding” of the finch, with the help of “appropriate population studies”

  • implement “appropriate monitoring protocols” to track the finch’s population over time

  • restrict grazing in nearby areas.

The only remaining state environmental approval for the project now is Adani’s groundwater management plan, on which a decision is due by June 13.

Bad plan caused the delays

As members of the scientific panel that reviewed the finch management plan, we can understand the Premier’s frustration. There is no excuse for such a poor plan to have been put forward for approval when the company has been aware for almost a decade that the land it wants to mine is home to the largest known remaining population of the black-throated finch.

There has already been ample time to undertake the studies Adani has pledged to carry out in the future. Had it done so before now, it could have put its claims to be able to manage the finch’s extinction risk on a much more solid footing.

As it is, the plan we reviewed made biologically improbable assumptions about the finch, while ignoring what is known about the finch’s precipitous decline so far. Under the plan, people with the curious title of “fauna spotter-catchers” were to find finches and move them “to suitable habitat adjacent to the disturbance, if practical” before the habitat is destroyed.

It sounds impractical, and will in all likelihood prove to be so. If the adjacent habitat already has finches, it is likely to be “full” and so won’t be able to support mining refugees. If it lacks finches, there is probably a very good reason.

The finch has been observed only a handful of times in just a tiny proportion of the area purchased for conservation purposes near the mine site. The finch has had more than 10,000 years to occupy and breed in the proposed conservation area that is supposed to offset the impact of the mine. It hasn’t, and it probably won’t.

As far as can be determined by overlaying the available maps, the proposed conservation area has a different geology and soil type. Adani has categorically failed to provide robust scientific evidence to demonstrate that the conservation reserve will adequately offset the loss of the finches and the habitat in the mined area. It has had more than 10 years to conduct the science to provide the evidence.



Meanwhile, before the existing habitat is mined, the plan had talked about grazing being used to control bushfire fuel loads and reduce the abundance of a weed called buffel grass. Yet grazing is thought to be the main reason the finches have disappeared from most of their once vast range – they once occurred from the Atherton tablelands to northern New South Wales.

The new plan is said to “restrict grazing” but no details are yet available. Under the original plan, the cattle would have got fat on the buffel grass pastures just as they did in all the places where the finch once lived.

Rigorous research

What must really frustrate the Queensland Premier is the contrast between Adani’s efforts with the black-throated finch and the much more rigorous work done by mining companies who find themselves in similar situations. Rio Tinto, for example, is currently funding high-quality research on two other birds, the palm cockatoo and red goshawk, ahead of its planned expansion of bauxite operations on Cape York Peninsula.

Vista Gold, meanwhile, funded research on stress levels in Gouldian finches long before mining was planned to begin at its Mt Todd goldmine in the Northern Territory.

In criticising Adani’s plan, we are not criticising mining. Like all Australians, we use the products of mining every day. We enjoy a high standard of living that is delivered partly by royalties from mining. We also understand that miners (and politicians) in Queensland want to see jobs created.

Most mining companies, however, provide jobs while willingly abiding by national and state legislation. They compromise where necessary to minimise environmental harm. And crucially, they commission research to demonstrate how they can mitigate damage well before that damage occurs, rather than when their operations are already underway.




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In contrast, the so-called research and monitoring that went into Adani’s finch plan seems only to conclude that more research is needed. After nine years, Adani did not even know the population size of the finch, how it moves around the landscape, or even what it eats.

Given the time available, this bird could (and should) have been among the best-studied in Australia. The management plan could then have been based on robust evidence that would show how best to safeguard the finch population.

Now the research and monitoring is a hurried add-on with no proof that the threat posed to the finch can actually be solved and an extinction averted. Given the high stakes involved, Australians might reasonably have expected something altogether more rigorous.The Conversation

Stephen Garnett, Professor of Conservation and Sustainable Livelihoods, Charles Darwin University; Brendan Wintle, Professor Conservation Ecology, University of Melbourne; David Lindenmayer, Professor, The Fenner School of Environment and Society, Australian National University; Don Franklin, Adjunct Research Fellow, Research Institute for Environment and Livelihoods, Charles Darwin University, and John Woinarski, Professor (conservation biology), Charles Darwin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

After decades away, dengue returns to central Queensland



Australia’s dengue cases are usually limited to far north Queensland.
Shutterstock

Cameron Webb, University of Sydney

The Queensland city of Rockhampton was free of dengue for decades. Now, a case of one of the most serious mosquito-borne diseases has authorities scratching their heads.

Over the past decade, dengue infections have tended to be isolated events in which international travellers have returned home with the disease. But the recent case seems to have been locally acquired, raising concerns that there could be more infected mosquitoes in the central Queensland town, or that other people may have been exposed to the bites of an infected mosquito.

What is dengue fever?

The illness known as dengue fever typically includes symptoms such as rash, fever, headache, joint pain, vomiting, diarrhoea, and abdominal pain. Symptoms can last for around a week or so. Four types of dengue virus cause the illness and they are spread by mosquito bites.

Once infected, people become immune to that specific dengue virus. However, they can still get sick from the other dengue viruses. Being infected by multiple dengue viruses can increase the risk of more severe symptoms, and even death.

Hundreds of millions of people are infected each year. It is estimated that 40% of the world’s population is at risk given the regions where the virus, and the mosquitoes that spread it, are active. This includes parts of Australia.




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The last significant outbreak in Australia occurred in far north Queensland in 2009, when more than 900 people were infected by local mosquitoes.

Only a handful of locally acquired cases have been reported around Cairns and Townsville in the past decade. All these cases have two things in common: the arrival of infected travellers and the presence of the “right” mosquitoes.

The dengue virus isn’t spread from person to person. A mosquito needs to bite an infected person, become infected, and then it may transmit the virus to a second person as they bite. If more people are infected, more mosquitoes can pick up the virus as they bite and, subsequently, the outbreak can spread further.

Why are mosquitoes important?

Australia has hundreds of different types of mosquitoes. Dozens can spread local pathogens, such as Ross River virus, but just one is capable of spreading exotic viruses such as dengue and Zika: Aedes aegypti.

Aedes aegypti breeds in water-holding containers around the home. It is one of the most invasive mosquitoes globally and is easily moved about by people through international travel. While these days the mosquito stows away in planes, historically it was just as readily moved about in water-filled barrels on sailing ships.

Aedes aegypti is the mosquito primarily responsible for the spread of dengue viruses.
By James Gathany – PHIL, CDC, Public Domain

The spread of Aedes aegypti through Australia is the driving force in determining the nation’s future outbreak risk.

The mosquito was once widespread in coastal Australia but since the 1950s, it become limited to central and far north Queensland. We don’t really know why – there are many possible reasons for the retreat, but the important thing now is they don’t return to temperate regions of the country.

Authorities must be vigilant to monitor their spread and, where they’re currently found, building capacity to respond should cases of dengue be identified.




Read more:
Is climate change to blame for outbreaks of mosquito-borne disease?


What happened in Rockhampton?

Last week, for the first time in decades, a locally acquired case of dengue was detected in Rockhampton, in central Queensland. The disease was found in someone who hasn’t travelled outside the region, which suggests they’ve been bitten locally by an infected mosquito.

This has prompted a full outbreak response to protect the community from any additional infected mosquitoes.

While the risk of dengue around central Queensland is considered lower than around Cairns or Townsville, authorities are well prepared to respond, with a variety of techniques including house-to-house mosquito surveillance and mosquito control to minimise the spread.

These approaches have been successful around Cairns and Townsville for many years and have helped avoid substantial outbreaks.

The coordinated response of local authorities, combined with the onset of cooler weather that will slow down mosquitoes, greatly reduces any risk of more cases occurring.

What can we do about dengue in the future?

Outbreaks of dengue remain a risk in areas with Aedes aegypti mosquitoes. There are also other mosquitoes, such as Aedes albopictus (the Asian tiger mosquito), that aren’t currently found on mainland Australia but may further increase risks should they arrive. Authorities need to be prepared to respond to the introductions of these mosquitoes.




Read more:
How we kept disease-spreading Asian Tiger mozzies away from the Australian mainland


While a changing climate may play a role in increasing the risk, increasing international travel, which represents pathways of introduction of “dengue mosquitoes” into new regions of Australia, may be of greater concern.

There is more that can be done, both locally and internationally. Researchers are working to develop a vaccine that protects against all four strains of dengue virus.

Others are tackling the mosquitoes themselves. Australian scientists have played a crucial role in using the Wolbachia bacteria, which spreads among Aedes aegypti and blocks transmission of dengue, to control the disease.

The objective is to raise the prevalence of the Wolbachia infections among local mosquitoes to a level that greatly reduces the likelihood of local dengue transmission.

Field studies have been successful in far north Queensland and may explain why so few local cases of dengue have been reported in recent years.

While future strategies may rely on emerging technologies and vaccines, simple measures such as minimising water-filled containers around our homes will reduce the number of mosquitoes and their potential to transmit disease.The Conversation

Cameron Webb, Clinical Lecturer and Principal Hospital Scientist, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.