.

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

We’re often warned to avoid mosquito bites after major flooding events. With more water around, there are likely to be more mosquitoes.

As flood waters recede around Townsville and clean-up efforts continue, the local population will be faced with this prospect over the coming weeks.

But whether a greater number of mosquitoes is likely to lead to an outbreak of mosquito-borne disease is tricky to predict. It depends on a number of factors, including the fate of other wildlife following a disaster of this kind.

Mozzies need water

Mosquitoes lay their eggs in and around water bodies. In the initial stages, baby mosquitoes (or “wrigglers”) need the water to complete their development. During the warmer months, it doesn’t take much longer than a week before they are grown and fly off looking for blood.

So the more water, the more mosquito eggs are laid, and the more mosquitoes end up buzzing about.

But outbreaks of disease carried by mosquitoes are dependent on more than just their presence. Mosquitoes rarely emerge from wetlands infected with pathogens. They typically need to pick them up from biting local wildlife, such as birds or mammals, before they can spread disease to people.


Read more: The worst year for mosquitoes ever? Here's how we find out


Mosquitoes and extreme weather events

Historically, major inland flooding events have triggered significant outbreaks of mosquito-borne disease in Australia. These outbreaks have included epidemics of the potentially fatal Murray Valley encephalitis virus. In recent decades, Ross River virus has more commonly been the culprit.

A focal point of the current floods is the Ross River, which runs through Townsville. The Ross River virus was first identified from mosquitoes collected along this waterway. The disease it causes, known as Ross River fever, is diagnosed in around 5,000 Australians every year. The disease isn’t fatal but it can be seriously debilitating.

Following substantial rainfall, mosquito populations can dramatically increase. Carbon dioxide baited light traps are used by local authorities to monitor changes in mosquito populations. Cameron Webb (NSW Health Pathology)

In recent years, major outbreaks of Ross River virus have occurred throughout the country. Above average rainfall is likely a driving factor as it boosts both the abundance and diversity of local mosquitoes.

Flooding across Victoria over the 2016-2017 summer produced exceptional increases in mosquitoes and resulted in the state’s largest outbreak of Ross River virus. There were almost 1,700 cases of Ross River virus disease reported there in 2017 compared to an average of around 300 cases annually over the previous 20 years.


Read more: Explainer: what is Ross River virus?


Despite plagues of mosquitoes taking advantage of flood waters, outbreaks of disease don’t always follow.

Flooding resulting from hurricanes in North America has been associated with increased mosquito populations. After Hurricane Katrina hit Louisiana and Mississippi in 2005, there was no evidence of increased mosquito-borne disease. The impact of wind and rain is likely to have adversely impacted local mosquitoes and wildlife, subsequently reducing disease outbreak risk.

Applying insect repellent is worthwhile even if the risk of mosquito-borne disease isn’t known. From shutterstock.com

Australian studies suggest there’s not always an association between flooding and Ross River virus outbreaks. Outbreaks can be triggered by flooding, but this is not always the case. Where and when the flooding occurs probably plays a major role in determining the likelihood of an outbreak.

The difficulty in predicting outbreaks of Ross River virus disease is that there can be complex biological, environmental and climatic drivers at work. Conditions may be conducive for large mosquito populations, but if the extreme weather events have displaced (or decimated) local wildlife populations, there may be a decreased chance of outbreak.

This may be why historically significant outbreaks of mosquito-borne disease have occurred in inland regions. Water can persist in these regions for longer than coastal areas. This provides opportunities not only for multiple mosquito generations, but also for increasing populations of water birds. These birds can be important carriers of pathogens such as the Murray Valley encephalitis virus.


Read more: Giant mosquitoes flourish in floodwaters that hurricanes leave behind


In coastal regions like Townsville, where the main concern would be Ross River virus, flood waters may displace the wildlife that carry the virus, such as kangaroos and wallabies. For that reason, the flood waters may actually reduce the initial risk of outbreak.

Protect yourself

There is still much to learn about the ecology of wildlife and their role in driving outbreaks of disease. And with a fear of more frequent and severe extreme weather events in the future, it’s an important area of research.

Although it remains difficult to predict the likelihood of a disease outbreak, there are steps that can be taken to avoid mosquito bites. This will be useful even if just to reduce the nuisance of sustaining bites.

Cover up with long-sleeved shirts and long pants for a physical barrier against mosquito bites and use topical insect repellents containing DEET, picaridin, or oil of lemon eucalyptus. Be sure to apply an even coat on all exposed areas of skin for the longest lasting protection.

Cameron Webb and the Department of Medical Entomology, NSW Health Pathology and University of Sydney, have been engaged by a wide range of insect repellent and insecticide manufacturers to provide testing of products and provide expert advice on the biology of medically important insects. Cameron has also received funding from local, state and federal agencies to undertake research into mosquito-borne disease surveillance and management.

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

Read more http://theconversation.com/after-the-floods-come-the-mosquitoes-but-the-disease-risk-is-more-difficult-to-predict-111173

Become Independent and Install a Solar Power System in your Property

We are certainly living in a very exciting time, and when you consider the technological advances we have witnessed in the last 50 years, it really is amazing. In the 1960s, the Internet emerged and...

News Company - avatar News Company

The Amazon is on fire – here are 5 things you need to know

Huge fires are raging across multiple regions of the Amazon Basin. Guaira Maia/ISARecord fires are raging in Brazil’s Amazon rainforest, with more than 2,500 fires currently burning. They are ...

Danilo Ignacio de Urzedo, PhD candidate, University of Sydney - avatar Danilo Ignacio de Urzedo, PhD candidate, University of Sydney

It's not just athletes who get Achilles tendon pain, but exercising is the answer

Basketball fans around the world were recently sickened by the footage of NBA star Kevin Durant’s Achilles tendon rupturing during a game. But while many think it’s only elite athletes...

Sean Docking, Post-doctoral researcher, La Trobe University - avatar Sean Docking, Post-doctoral researcher, La Trobe University

Australia's energy woes will not be solved by reinforcing a monopoly

Australia's energy market has a logjam, Sean Davis/Flickr, CC BY-NC-SAThe possibility of blackouts affecting half of Victoria has attracted plenty of attention to a document once read only by industry...

Bruce Mountain, Director, Victoria Energy Policy Centre, Victoria University - avatar Bruce Mountain, Director, Victoria Energy Policy Centre, Victoria University

Tim Fischer had his blind spots, but he was an unsung champion of an Asian-facing Australia

Amid the tributes to former deputy prime minister Tim Fischer and the stories of his authenticity, courage and quirky interests – like trains and military history – what has struck me most...

Tim Harcourt, J.W. Nevile Fellow in Economics and host of The Airport Economist, UNSW - avatar Tim Harcourt, J.W. Nevile Fellow in Economics and host of The Airport Economist, UNSW

VIDEO: Michelle Grattan on Tim Fischer's legacy - and Scott Morrison's first year

Michelle Grattan talks about the sad news of the passing of former Deputy Prime Minister Tim Fischer with University of Canberra Vice-Chancellor Professor Deep Saini. They also discuss Scott Morrison&...

Michelle Grattan, Professorial Fellow, University of Canberra - avatar Michelle Grattan, Professorial Fellow, University of Canberra

Catastrophic Queensland floods killed 600,000 cattle and devastated native species

In February, about 600,000 cattle were killed by catastrophic flooding across north Queensland’s Carpentaria Gulf plains. The flood waters rose suddenly, forming a wall of water up to 70km wi...

Gabriel Crowley, Adjunct Principal Research Fellow, James Cook University - avatar Gabriel Crowley, Adjunct Principal Research Fellow, James Cook University

Four home traps that contribute to the gender pay gap

KPMG says Australia's gender pay gap declined from $3.05 an hour in 2014 to $2.43 in 2017. www.shutterstock.comAustralia’s gender pay gap is diminishing, says a new report, but some contributors...

Emma Willamson, Adjunct Senior Research Fellow, Monash University - avatar Emma Willamson, Adjunct Senior Research Fellow, Monash University

Australia wants to install military technology in Antarctica – here's why that's allowed

Technology, such as satellite systems, can be used for both military and scientific purposes. ShutterstockThis week, the ABC revealed that the Australian Defence Force wants to roll out military tech...

Tony Press, Adjunct Professor, Institute for Marine and Antarctic Studies, University of Tasmania - avatar Tony Press, Adjunct Professor, Institute for Marine and Antarctic Studies, University of Tasmania

Why some feminists oppose allowing people to choose their sex on birth certificates

Legislation in Victoria would allow people to change the sex on their birth certificates with just a declaration, not sex reassignment surgery. ShutterstockA bill currently before the Victorian parlia...

Holly Lawford-Smith, Senior Lecturer in Political Philosophy, University of Melbourne - avatar Holly Lawford-Smith, Senior Lecturer in Political Philosophy, University of Melbourne

Plants are going extinct up to 350 times faster than the historical norm

Plant extinctions have skyrocketed, driven in large part by land clearing and climate change. Graphic Node/Unsplash, CC BY-SAEarth is seeing an unprecedented loss of species, which some ecologists are...

Jaco Le Roux, Associate Professor, Macquarie University - avatar Jaco Le Roux, Associate Professor, Macquarie University

Vital Signs: economically, Australia is at risk of becoming Germany, and not in a good way

Once, emulating Germany would be something to be proud of. Not at the moment. ShutterstockIt’s four years since then Prime Minister Tony Abbott warned Australia had been heading to “a Gree...

Richard Holden, Professor of Economics, UNSW - avatar Richard Holden, Professor of Economics, UNSW

'What is wrong with me? I'm never happy and I hate school'

Remember, there is always someone to talk to about these things. Wes Mountain Hi, I was just wondering if something’s wrong with me because I’m never happy and never want to do anything a...

Louise Remond, Clinical Psychologist, University of Technology Sydney - avatar Louise Remond, Clinical Psychologist, University of Technology Sydney

Friday essay: how a Bengali book in Broken Hill sheds new light on Australian history

The large book bearing a handwritten English label, 'The Holy Koran', was not a Quran, but a 500-page volume of Bengali Sufi poetry. Samia KhatunSome 1,000 kilometres inland from Sydney, over the Blu...

Samia Khatun, Senior Lecturer, SOAS, University of London - avatar Samia Khatun, Senior Lecturer, SOAS, University of London

Unlawful strip searches are on the rise in NSW and police aren’t being held accountable

Being strip searched by the police can be intrusive, humiliating and harmful. Typically, strip searches involve being required to strip naked in front of police officers, who often give the direction ...

Vicki Sentas, Senior Lecturer, UNSW Law, UNSW - avatar Vicki Sentas, Senior Lecturer, UNSW Law, UNSW

How to make good arguments at school (and everywhere else)

There are more important things than winning an argument – like making everyone feel valued. www.shutterstock.comFrom as early as Grade 3 teachers start teaching children how to put across thei...

Luke Zaphir, Researcher for the University of Queensland Critical Thinking Project; and Online Teacher at Education Queensland's IMPACT Centre, The University of Queensland - avatar Luke Zaphir, Researcher for the University of Queensland Critical Thinking Project; and Online Teacher at Education Queensland's IMPACT Centre, The University of Queensland

GM crops: to ban or not to ban? That's not the question

The South Australian government recently announced its intention to lift the long-standing statewide moratorium on genetically modified (GM) crops, following a statutory six-week consultation period. ...

Rachel A. Ankeny, Professor of History and Philosophy, and Deputy Dean Research (Faculty of Arts), University of Adelaide - avatar Rachel A. Ankeny, Professor of History and Philosophy, and Deputy Dean Research (Faculty of Arts), University of Adelaide

Grattan on Friday: Courting 'quiet Australians' from 'bubble central', it's been a remarkable first year for Scott Morrison

Can Scott Morrison maintain the image of separation from the Canberra elite, given he's its most powerful member? AAP/The ConversationEven Scott Morrison, with his abundant self-belief, couldn’t...

Michelle Grattan, Professorial Fellow, University of Canberra - avatar Michelle Grattan, Professorial Fellow, University of Canberra

Trust Me, I’m An Expert: Why the Hong Kong protesters feel they have nothing to lose

Last weekend, hundreds of thousands of people again took to the streets in Hong Kong to protest against the government – the 11th straight weekend of demonstrations that began in June over a pro...

Sunanda Creagh, Head of Digital Storytelling - avatar Sunanda Creagh, Head of Digital Storytelling

Sick and Tired of Your Dead End Job? Try Teaching!

Tired of the same old grind at the office? Want an opportunity to impact lives both in your community and around the world? Do you love to travel and have new experiences? Teaching English is the perfect job for you! All you need is a willingness to ...

News Company - avatar News Company

The Impact of an Aging Population in Australia

There’s an issue on the horizon that Australia needs to prepare for. The portion of elderly citizens that make up the country’s overall population is increasing, and we might not have the infrastructure in place to support this. Australians h...

News Company - avatar News Company

LifeStyle

A Guide for Tenants

The cost of purchasing a home has been increasing, and the size of deposits needed, make buying pr...

Top ways for men to look after their skin

According to Jack Simmons, from Aboutmen, more and more men are taking pride in their appearance a...

Top 10 Caravan Storage Tips & Tricks

Taking caravan trips is a popular Aussie pastime, but if you have spent more than a few days in ...

5 Meaningful Gifts Your Mother Would Simply Love

Wouldn’t it be wonderful to amaze the person who loves you the most with a thoughtful gift? Why ...