Are mosquitoes disappearing?

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There’s been a swarm of headlines recently about the global decline of insects. Could mosquitoes be disappearing too? Probably not but how would we know?

Recent research suggests that over 40% of insects worldwide are in decline. Some of the most vulnerable insects are those that occupy specific ecological niches. When scientists reviewed over 70 historical reports of insect declines, environmental degradation, the spread of agriculture, and widespread insecticide use were suspected for causing the decline.

What about mosquitoes? Sadly, they’re not a group of insects many people would care too much about if they were threatened with extinction.

Some of the most important mosquitoes, those that transmit dengue viruses or malaria parasites, are evading our efforts to eradicate them. For these insects, the insects authorities the world over actively are trying to kill, they’re surviving quite well. They’re becoming resistant to commonly used insecticides and they’re thriving living in habitats in and around our cities.

The reality is that some mosquitoes are probably doing very well , while those potentially under threat are probably those we know least about.

Tracking change in mosquito populations

There are over 300 mosquitoes in Australia. The mosquitoes that bring with them the greatest pest and public health risks are well studied. Mosquitoes such as Aedes camptorhynchus, Aedes vigilax, and Culex annulirostris are nuisance-biting pests and have been associated with outbreaks of Ross River virus disease. Their populations are monitored as part of mosquito control and surveillance programs around the country. But these programs probably won’t reliably pick up declines in lesser known mosquitoes.

There are mosquito surveillance programs around the country that provide information on local mosquito populations to health authorities. That’s how scientists know if this really is the “worst year for mosquitoes ever”! There is little evidence that the major pest mosquitoes are in decline. But these programs probably won’t reliably pick up declines in lesser known mosquitoes.

Mosquitoes under threat?

It is entirely possible that there are mosquitoes under threat.

What about the mosquitoes that specifically feed on frogs, how will they be impacted by declining frog populations?

Mosquitoes that are highly specialised to certain environments or ecological niches or close interactions with wildlife may struggle if their ecosystems are disrupted. Habitat degradation may hit some mosquitoes in much the same way it’ll hit other insects. It won’t end well.

What about mosquitoes associated with snow-melt pools in the Australian alps? Could climate change see their habitats destroyed?

Mosquitoes can adapt

Mosquitoes can be some of the most adaptable animals on the plant. That’s probably why they’ve been such persistent pests. In fact many insects are quite adaptable to change and that’s why we may not be facing an “insect apocalypse” as many headlines suggest.

We’ve found that mosquitoes are more abundant in mangrove forests that are degraded or surrounded by industry. Some mosquitoes are even becoming resistant to commonly used insecticides. Those same issues threatening many thousands of insects are no problem for some mosquitoes.

The reality is, mosquitoes have already been around for millions of years, they’ll probably be around long after. Its just that we could take a few species with us…

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The image at the top of this article is of a carbon-dioxide baited mosquito trap, there were thousands of mosquitoes inside; collected late in 2018 along the Georges River in southern Sydney.

Join the conversation on Twitter, are there any mosquitoes you think are under threat?

 

Wetlands, climate change, and managing mosquitoes

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I’ve spent over twenty years sloshing about in wetlands around Sydney and surrounds. They’re changing. They’re changing due to shifts in climate, sea level rise, and urbanisation. The 2019 World Wetlands Day is a time to stop and reflect on the state of wetlands around the world and how we can keep them health under the threat of climate change.

World Wetlands Day is held every year on 2 February,  this day marking the adoption of the Convention on Wetlands on 2 February 1971 in Ramsar, Iran. The theme of the 2019 World Wetlands Day is “Wetlands and Climate Change” and we shouldn’t just think about the impact of climate change on wetlands but also how wetlands can help us as we face the challenges of a changing climate.

Coastal wetlands around Sydney are impacted in many ways. Mangrove forests and saltmarshes are degraded through direct and indirect human activity. There is recent research indicating that sea level rise is impacting mangroves along the Parramatta River in Sydney. This requires active management to ensure substantial degradation and die back occurs, as has been seen elsewhere in Australia.

Some of our research even suggests that degraded mangroves are more productive when it comes to mosquitoes. Effective rehabilitation of these habitats may actually reduce the mosquitoes flying out of these environments and impacting the community nearby. Similarly, urban planning should consider the risk posed by mosquitoes in wetlands adjacent to new and expanding residential developments. This includes major wetland rehabilitation projects.

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The challenges facing wetlands isn’t unique to Australia. Released in conjunction with World Wetlands Day preparations was The Global Wetland Outlook. A document that provides “a current overview of global wetlands: their extent, trends, drivers of change and the responses needed to reverse the historical decline in wetland area and quality”.

While we think of rainforests and coral reefs under greatest threat, it is a sobering thought to think that up to 87% of the global wetland resource has been lost since 1700. These are environments that were, until relatively recently, considered wastelands. With this lack of perceived value came greater susceptibility to abuse and degradation.

Along with the unsurprising loss of wetland area and decline in biodiversity associated with these environments come some interesting findings. The most interesting from a mosquito management point of view is that artificial wetlands are actually increasing in some areas. Notwithstanding an assessment of the ecosystem services they provide, they’re more likely to be closer to human habitation, so any mosquitoes associated with them may have relatively greater impact.

In recent years, the value of wetlands has increased. There is an understanding now that these environments provide critical ecosystem services. There is also a growing understanding of the wetland’s roles in mitigating the impacts of climate change. Coastal wetlands in particularly provide protection from increasingly severe storm events and trap valuable carbon stores that assist in mitigating the impacts of climate change.

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This then raises the issues of mosquitoes. Mosquitoes are a natural part of wetland ecosystems. While often their pest impacts may indicate the poor health of the wetlands, at other time, abundant mosquito populations are a natural occurrence that fluctuate in their intensity from year to year. How do best manage mosquitoes associated with these wetlands?

I’ve written about how I think mosquito control should actually be considered an important component of coastal wetland rehabilitation. How climate change may be impacting mosquito threats and that even hot and dry summers under the influence of El Nino may not necessarily mean that mosquitoes are less problematic.

Based on the experience during the 2018-2019 summer, mosquitoes seem to persist in plague proportions despite the extreme temperatures being experienced in NSW.

It is important to remember that there are many mosquito species associated with wetlands, especially freshwater habitats, that pose no substantial threat to humans. There are hundreds of mosquitoes in Australia, less than a dozen really pose a substantial pest or public health threat. Many mosquitoes may play an important ecological role in wetland ecosystems. This may include representing a locally important food source for insectivorous wildlife or possibly pollinating plants.

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A balance is required. If we’re going to continue squeezing an increasing human population into a narrow stretch of land up against the coast, there are many issues to consider here and they’re not just about how human activity is impacting those coastal wetlands. Pollution is a problem, our physical damage is another. Worst still, we’re taking away the opportunity of these normally resilient habitats to adapt to a rising sea levels and increasingly frequent storm events. Our cities and their infrastructure provide a hard and unforgiving edge against the wetlands.

Our wetlands even battle against themselves sometime. The threat of mangrove incursion into saltmarsh habitats is of increasing concern. Its counter-intuitive but perhaps we need to be pulling out mangroves to save some coastal wetlands.

Expanding, modifying, and creating new coastal wetlands will require local authorities to turn their mind to the issue of mosquitoes. Firstly, consideration needs to be given to what may constitute a tolerable level of mosquito exposure. How many mosquito bites are too many? How many cases of mosquito-borne disease are considered “normal” each year. Once these thresholds are drawn and exceeded, who is responsible for the decisions on active mosquito control? Who pays?

Another ecosystem disservice to consider is how the nuisance-biting of mosquitoes may discourage engagement with local wetlands. less engagement may mean less support for conservation and rehabilitation efforts. Less community interest, support, and activism may then result is less political drive to protect local wetlands by local authorities.

Importantly, decisions regarding the management of coastal wetlands, as well as those peppered throughout the city, need to be made with some consideration of mosquitoes and their potential impact. How do you convince the local community about the overall benefits of carbon sequestration, wildlife conservation, and protection of infrastructure is worthwhile if their quality of life is degraded through summer swarms and nuisance-biting mosquitoes?

More details on managing the risks associated with estuarine mosquitoes is provided in this book chapter included in the free Sydney Olympic Park Authority’s guide to managing urban wetlands.

For more about World Wetlands Day activities in Australia see here.

To stay up to date with my adventures in local wetlands, you can follow me on Instagram here.

 

 

 

Preparing for the exotic mosquito invasion of Australian backyards

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While Australia has hundreds of “home-grown” mosquitoes, it is just a few from overseas that have authorities on alert. Preparing for these new risks is critical if the future pest and public health risks associated with mosquitoes are to be effectively managed. Citizen scientists may hold the key to success!

A project underway in the Northern Rivers region of NSW is set to build a framework for responding to the threats of exotic mosquitoes. This is in association with the Building Resilience to Climate Change program, a partnership program between Local Government NSW (LGNSW) and the NSW Office of Environment and Heritage (OEH) to address identified climate change risks and vulnerabilities facing NSW councils.

Lead by Tweed Shire Council, the program “Developing and trialing a Northern Rivers Emerging Vector Response Plan” is designed to build capacity among local stakeholders in the region to better respond to possible introductions of exotic mosquitoes from overseas (or perhaps travelling south from Queensland).

The mosquitoes that pose the greatest risk are Aedes aegypti and Aedes albopictus. As well as being severe nuisance-biting pests, these mosquitoes can transmit pathogens of serious public health concern such as Zika, dengue and chikungunya viruses. The mosquitoes aren’t found in local wetlands, they prefer backyard water-holding containers. This means that should these mosquitoes make their way to NSW, local authorities must shift their focus from the swamps to the suburbs.

There is already a program in place monitoring mosquitoes and the pathogens they carry in NSW. This program is primarily focused on Ross River virus and the mosquitoes that transmit this pathogen. As a consequence, mosquito collections are typically in bushland or wetland areas adjacent to urban areas and may not readily pick up exotic mosquitoes that have moved into local backyards.

Authorities must expand their approach and develop strategic responses to these exotic threats.

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Representatives of local stakeholders help survey 300 backyards in Tweed Heads!

This work is already underway. A workshop for local stakeholders was held in December 2017 in Tweed Heads along with a two day field exercise in which around 300 residential backyards were surveyed for potential mosquito habitats. A wide range of potential sources of mosquitoes was identified, the most common were water-filled plants (particularly bromeliads), pot-plant saucers, buckets, wheel burrows, garden ornaments, and rainwater tanks.

The survey highlighted how important community involvement in the program is and “citizen science” is currently being employed to assess some mosquito surveillance technologies in backyards across the Tweed Heads region.

Supported by a grant from the Human Health and Social Impacts Node, a partnership between the Office of Environment and Heritage, NSW Health and The University of Sydney, over 150 mosquito traps were deployed and it is hoped that the mosquitoes they collect will help inform the development of strategic mosquito surveillance in the future.

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An example of the mosquito traps deployed across two suburbs in Tweed Heads to collect eggs from mosquitoes buzzing about backyards

Whats needed now is a better understanding of how the community thinks about mosquitoes and how they’re trying to make their backyard less favourable for these pests.

Residents in the Local Government Areas of Tweed, Byron, Ballina, Richmond Valley, Clarence Valley, Lismore and Kyogle are invited to participate in a short survey. It is a great way to learn how to reduce the risks of mosquito bites in your backyard (there is also an iPad that can be won!).

If you live in the areas mentioned, or know friends or family who do, please complete and/or share the details of the survey.

You can start the survey now!

There are many factors contributing to the future threat of  mosquitoes and mosquito-borne disease in Australia. Climate change or exotic mosquito introductions may be game changes but one of the most important considerations is the importance of community awareness and willingness to assist local health authorities.

Perhaps the new mosquito emoji will help too?

 

 

 

 

 

Can citizen science help stop mosquito-borne disease outbreaks?

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Mosquito surveillance has been a critical component of how health authorities manage the risk of mosquito-borne disease. Data on the abundance and diversity of mosquitoes, together with activity of mosquito-borne pathogens, can guide decisions on when and how to apply mosquito control agents or issue public health warnings.

Almost every state and territory in Australia conducts seasonal mosquito surveillance. The exceptions are Tasmania and ACT, although both have had some limited investigations over the years. Even among those doing routine surveillance, the program structure varies but most include the collection of mosquitoes. This is how we can determine if it really is “the worst mosquito season ever”!

The programs are currently are working well in providing early warnings of outbreaks of mosquito-borne disease. These programs often include mosquito trapping undertaken by local governments and, occasionally, members of the public. For may years there has been a strong interest in citizen scientists undertaking mosquito sampling, particularly by some schools. The projects that I’ve been involved with have rarely got off the ground for various reasons. School holidays at the peak of mosquito season doesn’t help. Beyond that, the consumable costs of the traps we use, especially the dry-ice (carbon dioxide) used to bait the traps, can be a barrier to involvement. Dry-ice use in schools, and the associated health and safety issues, has been a cause for concern too. Finally, the fact that mosquitoes may be attracted to traps operated in school or community grounds and that these mosquitoes may be carrying disease-causing pathogens can often raise concerns.

As a result, there really haven’t been any major citizen science based mosquito surveillance programs until recently. Things are changing.

One reason local authorities are starting to turn their minds to a citizen science based approach is that the threat of exotic mosquitoes will require a shift in focus from the swamps to the suburbs. The mosquitoes that drive outbreaks of dengue, particularly Aedes aegypti and Aedes albopictus live in water-holding containers in backyards and populations are not as easily measured by traditional surveillance approaches. This is why there has been a much stronger engagement with the public in Far North QLD (a region where Aedes aegypti is present and causes occasional outbreaks of dengue) where health authorities are regularly visiting backyards looking for and controlling backyard mosquitoes

There are many reasons why citizen science is starting to come into play when it comes to mosquito surveillance more broadly. Technology is getting better (as highlighted by many smartphone apps) but also, some of the laboratory techniques are getting cheaper. This is a really critical issue.

A breakthrough in rapid testing of mosquitoes led to the development of an award winning initiative in Brisbane by Metro South Health and Queensland Health Forensic & Scientific Services. The Zika Mozzie Seeker project combines this new laboratory technique with DIY mosquito traps by the general public to help track exotic mosquitoes. In short, residents create their own mosquito trap out of a bucket or recycled plastic container, it is filled with water and placed in a yard with a small piece of paper hung inside. Mosquitoes then drop by to lay eggs on the paper. After a couple of weeks, the traps are collected and egg filled paper strips sent to the lab and tested to track the DNA of local and exotic mosquitoes. The project has been an amazing success with around 2,000 participants being involved in recent years (that adds up to about 150,000 mosquito eggs collected and tested). Luckily, no exotic mosquitoes have been detected.

But when it comes to citizen science based projects, perhaps it isn’t the mosquitoes collected (the backyard mosquito battles are fun to track though) but the awareness raised that is important. Awareness not only of the risks posed by mosquitoes, but what you can do about them through the safe and effective use of mosquito repellents and other personal protection measures. Engaging the public through citizen science may be the way to go. It doesn’t always work in reaching new audiences, as was discovered in a mosquito surveillance project in South Australia, but that doesn’t mean it won’t!

Perhaps the rise in new smartphone apps will help. There are a few out there, like the Globe Observer and Mosquito Alert. These, and other smartphone apps, deserve their own post (stay tuned). However, the significant initiative of recent years has been the Global Mosquito Alert project. Launched in May 2017, here is an extract from their media release:

The new initiative, launched under the name ‘Global Mosquito Alert’, brings together thousands of scientists and volunteers from around the world to track and control mosquito borne viruses, including Zika, yellow fever, chikungunya, dengue, malaria and the West Nile virus. It is the first global platform dedicated to citizen science techniques to tackle the monitoring of mosquito populations. The programme is expected to move forward as a collaboration involving the European, Australian and American Citizen Science Associations as well as the developing citizen science community in Southeast Asia.

With such momentum, it is an exciting time to consider the potential of citizen science in Australian mosquito surveillance programs. This is what i will be exploring in my presentation at the Australian Citizen Science Conference in Adelaide this week.

I’ll be presenting the paper on Wednesday 7 February 2018 in the “Empower with Data” session. The full abstract of our presentation is below:

The public as a partner in enhancing mosquito surveillance networks to protect public health

Craig Williams (1), Brian L. Montgomery (2), Phil Rocha (2), and Cameron Webb (3)

(1) University of South Australia, School of Pharmacy and Medical Sciences; (2) Metro South Public Health Unit, Queensland Health; (3) Medical Entomology, Marie Bashir Institute of Infectious Diseases and Biosecurity, University of Sydney

Mosquito-borne diseases are pervasive public health concerns on a global scale. Strategic management of risk requires well-designed surveillance programs, typically coordinated by local health authorities, for both endemic and exotic mosquitoes as well as the pathogens that they may transmit. There is great potential to utilise citizen science to expand the reach of current surveillance programs, particularly those centred on urban areas. There is increasing focus internationally on the role of citizen science in mosquito surveillance as evidenced by the establishment of the ‘Global Mosquito Alert’ project driven by multiple international stakeholders and citizen science associations. In Australia, new initiatives to engage the public in mosquito surveillance are emerging in multiple centres; utilizing a range of emerging field and laboratory technologies that remove previously existing barriers to community involvement. In South Australia, citizen science entomology programs have been trialed, and mosquito trapping and identification technology to expand existing trapping networks has been assessed. In suburban South-East Queensland, Zika Mozzie Seeker is linking citizen scientists into a network by using new laboratory techniques to rapidly screen for Ae. aegypti DNA in large numbers of eggs collected from DIY ovitraps,. In NSW, citizen science is being used to promote biodiversity and delineate pest and non-pest activity of mosquitoes associated with urban wetlands and surrounding suburbs. Citizen science holds great potential for public engagement activities as well as serving to enhance existing surveillance operations.

 

Join the conversation on Twitter by following Dr Cameron Webb, A/Prof Craig Williams and keep an eye on the meeting via the hashtag

A flood of festive season media coverage

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Spring is gone and with the arrival of summer comes the mosquitoes. Calls from the media inevitably follow shortly after. I have no doubt many journalists, broadcasters and producers have my name in their diaries, circled brightly in red, on the first day of summer!

It is a fun part of my job to deal with the media. Its more than just getting a chance to talk about mosquitoes and their role in the local environment, it also provides an opportunity to do some important public health communications around the issues of mosquito bite prevention and management of mosquito-borne disease.

Scorchers, sun protection, and buzzing bloodsuckers

What got the ball rolling this year was a joint media briefing arranged by ausSMC. Alongside colleagues talking about heat waves, summer storms, sun protection and bushfire, I shared some tips on protecting yourself from mosquito bites and mosquito-borne disease this summer. It was interesting speaking alongside Professor Sanchia Aranda, CEO of Cancer Council Australia, and comparing the ways we promote safe and effective use of sunscreens and mosquito repellents. This was picked up on in additional media coverage. Overall, there was over 300 local and international articles following this media briefing!

The briefing provided an opportunity to fill a gap in public health communication I’ve identified (and tried to fill) in recent years. Health authorities are pretty good at providing advice on choosing mosquito repellents but less so on using them effectively. Ensuring repellents are actually used effectively is the best way to increase the protection of the community against mosquito-borne disease.

In early December we held our “Sydney Ideas: Mosquitoes in the City” event at Westmead. This was a great opportunity to speak to the community and the well attended event prompted some broader interest in the work of presenters.

It was a pleasure being able to visit the studios of ABC Radio National with Prof Tony Capon, Professor of Planetary Health at the University of Sydney, to discuss with Philip Adams how urbanisation and a changing climate may influence local mosquito populations and mosquito-borne disease risk. I’m working more and more with Tony so nice to share the opportunity to talk about this initiative with him on national radio. You can listen back here. This work is strongly linked to the theme of the “Mosquitoes in the City” event and there is clearly much to learn regarding the place of mosquitoes, wetlands, wildlife and mosquito-borne disease at the fringes of our metropolitan regions under the influence of a changing climate and the ways urban design responds to the threat.

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Why me? I wish mozzies would bite my friends instead!

There was another boost in interest resulting from a spot on ABC News 24 Weekend Breakfast. The accompanying online article explaining why mosquitoes are more likely to bite some people more than others then sparked considerable interest! What followed was a bunch of radio and television interviews.

There was also a follow up article at News.com.au and this was also picked up on “Kids News” who republished a modified version of the story together with some suggestions for classroom learning exercises. Nice.

There were two different experiences with ABC News. The appearance on Weekend Breakfast was great. I’ve done segments with Andrew Geoghegan and Miriam Corowa before, have always been impressed with their knowledge and interest. I really enjoy the relaxed feel on the show. Was also a pleasure working with Dale Drinkwater, the producer, who put together the segment and accompanying article.

A couple of days later I appeared on News Breakfast with Virginia Trioli. As the program is produced out of Melbourne, I had to do a live cross from the Sydney studios. I always find these interviews a little uncomfortable as I’m tucked away in a small, dark recording booth staring down a camera and hoping my ear piece doesn’t fall out! I’m sure there is an art to these but I’m not sure I’ve mastered that just yet.

 

Once the mozzies start biting…

With the warm weather arriving and everyone’s minds turning to summer, there is always a flood of festive season-related media stories. Once the mozzie stories started popping up, many more media outlets starting running segments.

There were also warnings about the health threats of mosquitoes over the festive season from local health authorities.

I had the chance to visit many radio and television studios to conduct interviews, this time it was the first opportunity to visit the Macquarie Radio (home to 2UE and 2GB) for what turned out to be a relatively long (by commercial radio standards) interview with Tim Webster on Talking Lifestyle/2UE including a few callers asking about mosquito repellents, disease risk and what the “purpose” of mosquitoes actually is! Listen back via the Holiday and Home podcast.

Taking talkback can be tricky. I’m fortunate enough to have had an opportunity to do this reasonably routinely. I appreciate the opportunity to get a feel for what the community wants to know about mosquitoes, we should be taking these things into account when designing fact sheets and other communication material. There is no point in simply systematically repeating what has come before.

Live TV can also be tricky. I also had the chance to do segments on Channel Nine’s Today and Today Extra programs. These are always fun and I do find it fascinating to see how the behind-the-scenes production of these shows get put together.

Even the local newspaper, the Parramatta Sun, ran a nice story with great shot of me among the mangroves of the Parramatta River. It is also fun dragging photographers out into the wetlands. This time a fun shot of me from a different perspective other than simply standing beside a mosquito trap!

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There was certainly plenty of “buzz” (or should that be “hum”) about mosquitoes over recent weeks. Great to see other articles pop up by fellow science communicators as well as the occasionally celebrity. There can never be too many ways to get the message out!

The mosquito coil conversation

At the point where I thought everyone was getting sick of mosquitoes, my latest article on the safe and effective use of mosquito coils was published at The Conversation (as well as being republished by ABC News). To date there have been about 90,000 clicks on the article, highlighting just how interested people are in the topic.

There were a bunch of other interview requests on the back of this including ABC Sydney, ABC Brisbane and ABC Adelaide. You can listen back to my chat with James Valentine on ABC Nationwide Afternoons here.

It isn’t always easy managing media requests

To finish up, I think it is important to share some of the reality of wrangling all these media requests. Most importantly, it takes time. It takes time to prepare and it takes much more time to actually do these activities.

For live television appearances, that often only last a few moments, you’re typically asked to arrive at the studios 30-40min prior to scheduled interview. Notwithstanding the travel time back and forth from studios (often very early in the morning), this means the interruption to the day isn’t insignificant. There was one day that I participated in two different teleconferences while in transit to and between interviews at ABC in Ultimo and Channel Nine in Willoughby!

The other thing is that sometimes you’ll get bumped. I was scheduled to chat on a live television program that requested I bring along a cage of live mosquitoes. This is generally not a problem but it does take time, especially when I have to actually collect field caught mosquitoes especially for this purpose. Unfortunately, the segment got bumped on one day, rescheduled for the next and then bumped again for a second time.

It would be easy to get really upset in these circumstances but it is a reality of dealing with the media. Don’t take it personally as these things are mostly out of your control. If you’re keen to engage with the media, this is just one of the many challenges you’ll need to learn to manage.

Spot any other cool mozzie media things? Join the conversation on Twitter or Facebook!

 

A Guam visit to battle Zika virus and discover new mosquitoes

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There are few places on earth where you can search in water-filled canoes for one of the most dangerous mosquitoes on the planet less than a stone’s throw from tourists posing for selfies alongside their inflatable novelty swans in the nearby lagoon.

Guam is the place to go if you need to tick that off your “to do” list!

I was fortunate to be invited to speak at the Pacific Island Health Officers Association (PIHOA) Regional Zika Summit and Vector Control Workshop in Guam 25-29 June 2017. The theme of the summit was “Break Down the Silos for Preparedness and Management of Emergencies and Disasters in United States Affiliated Islands” and had objectives to critical analyze the regional responses to recent mosquito-borne disease outbreaks while developing policies to strengthening public health emergency response and preparedness systems and capabilities within the region.

The tranquil lagoons of the Pacific Islands may seem a very long way from the hustle and bustle of the busy South American cities that held the 2016 Olympics but just as Zika virus was grabbing the attention of sports reporters everywhere, health authorities active in the Pacific were growing concerned too.

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The Pacific has been far from free of mosquito-borne disease outbreaks. Previous outbreaks of dengue, chikungunya and even Ross River virus had struck numerous times. While sometimes widespread, at other times outbreaks were more sporadic or isolated. As is the case for many non-endemic countries, outbreaks are prompted by movement of infected travelers and the prevalence of local mosquitoes.

Across the region there are four mosquitoes of primary concern, Aedes aegypti, Aedes albopictus, Aedes polynesiensis and Aedes hensilli. The greatest concerns are associated with Aedes aegypti and in those countries where the mosquito is present, the risks of mosquito-borne disease outbreak are greatest. For this reason alone, it is imperative that good entomological surveillance data is collected to confirm the distribution of these mosquitoes but also to develop strategies to eradicate, where possible, Aedes aegypti should it be introduced to new jurisdictions.

With a growing interest in developing mosquito surveillance and control programs for exotic mosquitoes here in Australia, it was a perfect opportunity for me to get a closer look at how the threats of these mosquitoes and associated outbreaks of disease are managed.

On the third day of the meeting, vector control took centre stage. A brilliant day of talks from each of the jurisdictions on the disease outbreaks they’ve faced and how they’re preparing for future threats. There were presentations from the United States Affiliated Pacific Islands (USAPI) including Guam, the Federated States of Micronesia (Yap, Kosrea, Chuuk, Pohnpei), the Commonwealth of the Northern Marianas (CNMI), the Republic of Palau, the Republic of Marshall Islands (RMI), and American Samoa.

Hearing from these teams doing their best to protect their local communities from the threat of mosquito-borne disease, with only limited resources, was quite eye opening. There was passion and dedication but each territory faced unique challenges to ensure the burden of disease is minimised.

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Just outside the workshop venue were a series of water-filled canoes. Most contained larvae!

There is little doubt that climate variability will have a strong role to play in the impacts of mosquito-borne disease across the region in the future but there are so many other issues that could be contributing to increased risk too. One of the biggest problems is rubbish.

Time and time again, the issue of accumulated waste, especially car bodies and discarded tyres, was raised as a major problem. As many of the key pest mosquitoes love these objects that trap water, treatment of these increasing stockpiles becomes more of a concern. Community wide cleanups can help reduce the sources of many mosquitoes but the rubbish more often than not remains on the island and requires continued management to ensure is not becoming a home to millions of mosquitoes.

It is a reminder that successful mosquito control relies on much more than just insecticides. An integrated approach is critical.

There was a “hands on” session of surveillance and control. Coordinated by PIHOA’s Eileen Jefferies and Elodie Vajda, the workshop was a great success. It provided an opportunity for many to see how to prepare ovitraps and BGS traps (one of the most widely used mosquito traps) and discuss the various considerations for choosing and using the right insecticides to reduce mosquito-borne disease risk. Workshop attendees were also the luck recipients of a selection of cleaver public awareness material produced in Guam, from personal fans and anatomically incorrect plush mosquitoes to Frisbees and mosquito-themes Pokemon cards!

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Guam “mozzie” team: Elodie Vajda, Claire Baradi, Michelle Lastimoza, Eileen Jefferies and me

Following the summit, there was a chance to visit the new Guam “Mosquito Laboratory”, newly established as part of the Guam Environmental Public Health Laboratory (GEPHL). I’ll go out of my way to visit any mosquito laboratory but I was particularly keen to see this one as one of my previous students was playing a key role in establishing the mosquito rearing and identification laboratories. Elodie has been doing an amazing job and it was brilliant to geek out with her over some hard core mosquito taxomony as we tried to ID a couple of tricky specimens. [Make sure you check out our recent paper on the potential impact of climate change on malaria outbreaks in Ethiopia]

It actually turned out that one of their “tricky specimens” was a new species record for Guam – an exotic mosquito Wyeomyia mitchellii! The paper reporting this finding has just been published “New Record of Wyeomyia mitchellii (Diptera: Culicidae) on Guam, United States“.

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Mosquito-borne disease in the Pacific isn’t going anywhere and it’s important that once the focus fades from Zika virus, dengue and chikungunya viruses will again take centre stage and their potential impacts are significant. With the added risks that come with gaps in the understanding of local pest and vector species, the prevalence of insecticide resistance among local mosquitoes, climate variability and a struggle to secure adequate funding, challenges lay ahead in ensuring the burden of mosquito-borne disease doesn’t increase.

A modified version of this article appears in the latest issue (Winter 2017; 12(1)) of Mosquito Bites Magazine, (a publication of the Mosquito Control Association of Australia)

 

Why do mosquitoes seem to bite some people more?

Back in 2015, I had an article published at The Conversation on why some people are more likely to be bitten by mosquitoes than others. It is one of the most commonly asked questions I get whenever I give public talks (or friends and family are quizzing me at summer BBQs).

This article was incredibly successful and has currently been read by approximately 1.4 million people. That is a lot of people. Hopefully the science of mosquito bites has got out there and actually helped a few people stop themselves or their family being bitten by mosquitoes!

The warm weather is starting to arrive here in Australia so I am sharing this once more for those wondering why they’re always the “mosquito magnet” among their friends…

Health Check: why mosquitoes seem to bite some people more

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There are up to 400 chemical compounds on human skin that could play a role in attracting mosquitoes.  sookie/Flickr, CC BY-SA

There’s always one in a crowd, a sort of harbinger of the oncoming mosquito onslaught: a person mosquitoes seem to target more than others. What is it about these unlucky chosen few that makes them mosquito magnets?

There are hundreds of mosquito species and they all have slightly different preferences when it comes to what or who they bite. But only females bite; they need a nutritional hit to develop eggs.

Finding someone to bite

Mosquitoes are stimulated by a number of factors when seeking out a blood meal. Initially, they’re attracted by the carbon dioxide we exhale. Body heat is probably important too, but once the mosquito gets closer, she will respond to the smell of a potential blood source’s skin.

Studies have suggested blood type (particularly type O), pregnancy and beer drinking all make you marginally more attractive to mosquitoes. But most of this research uses only one mosquito species. Switch to another species and the results are likely to be different.

There are up to 400 chemical compounds on human skin that could play a role in attracting (and perhaps repulsing) mosquitoes. This smelly mix, produced by bacteria living on our skin and exuded in sweat, varies from person to person and is likely to explain why there is substantial variation in how many mozzies we attract. Genetics probably plays the biggest role in this, but a little of it may be down to diet or physiology.

One of the best studied substances contained in sweat is lactic acid. Research shows it’s a key mosquito attractant, particularly for human-biting species such as Aedes aegypti. This should act as fair warning against exercising close to wetlands; a hot and sweaty body is probably the “pick of the bunch” for a hungry mosquito!

Probably the most famous study about their biting habits demonstrated that the mosquitoes that spread malaria (Anopheles gambiae) are attracted to Limburger cheese. The bacteria that gives this cheese its distinctive aroma is closely related to germs living between our toes. That explains why these mosquitoes are attracted to smelly feet.

But when another mosquito (such as Aedes aegypti) is exposed to the same cheese, the phenomenon is not repeated. This difference between mosquitoes highlights the difficulty of studying their biting behaviours. Even pathogens such as malaria may make us more attractive to mosquitoes once we’re infected.

Only females bite because they need a nutritional hit to develop eggs.
Sean McCann/Flickr, CC BY-NC-SA

Researchers are trying to unscramble the irresistible smelly cocktails on the skins of “mosquito magnets”. But the bad news is that if you’re one of these people, there isn’t much you can do about it other than wearing insect repellents.

The good news is that you may one day help isolate a substance, or mixes of substances, that will help them find the perfect lure to use in mosquito traps. We could all then possibly say goodbye to topical insect repellents altogether.

Attraction or reaction?

Sometimes, it’s not the bite as much as the reaction that raises concerns. Think of the last time the mosquito magnets in your circle of friends started complaining about being bitten after the event where the purported mosquito feast took place. At least, they appear to have attracted more than the “bite free” people who were also at the picnic, or concert or whatever.

But just because some people didn’t react to mosquito bites, doesn’t mean they weren’t bitten. Just as we do with a range of environmental, chemical or food allergens, we all differ in our reaction to the saliva mosquitoes spit while feeding.

People who don’t react badly to mosquito bites may think they haven’t been bitten when they’ve actually been bitten as much as their itchy friends. In fact, while some people attract more mosquito bites than others, there’s unlikely to be anyone who never, ever, gets bitten.

The problem is that people who don’t react to mosquito bites may all too easily become complacent. If you’re one of them, remember that it only takes one bite to contract a mosquito-borne disease.

Finally, there is no evidence from anywhere in the world that there is something you can eat or drink that will stop you being bitten by mosquitoes. No, not even eating garlic, or swallowing vitamin B supplements.

The ConversationPerhaps if we spent as much time thinking about how to choose and use mosquito repellents as we do about why mosquitoes bite our friends and family less than us, there’d be fewer bites all around.

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

This article was originally published on The Conversation. Read the original article.

 

Talking wetlands, wildlife and mosquitoes at the 2017 Australian Entomological Society Meeting

homebushbay_mangroves_jan2016

I’ll be in Terrigal, on the NSW Central Coast, for the 2017 Australian Entomological Society conference and taking the opportunity to present a summary of a number of collaborative projects undertaken in recent years, from working out how surrounding landuse influences the mosquito populations in urban mangroves to how important mosquitoes are to the diet of local bats.

Together with a range of colleagues, I’ve been undertaking research into the factors driving mosquito and mosquito-borne disease risk in urban wetlands. It is a complex puzzle to solve with more than just mosquitoes determining local pest and public health risks. However, with outbreaks of mosquito-borne Ross River virus on the rise in recent years, including urban areas of Australia, there is a need to better understand the factors at play.

There is a range of factors that may increase the risk of Ross River virus, they include suitable wetlands, wildlife reservoirs of the pathogen and mosquitoes. Understanding the mosquitoes associated with urban estuarine and freshwater wetlands is critical.

Investigating the role of surrounding landuse in determining the mosquito communities of urban mangroves, we found that industrial and residential areas tended to increase abundance of mosquitoes, perhaps due to direct or indirect impacts on the health of those mangroves. We’ve found previously that mosquitoes problems are often associated with estuarine wetlands suffering poor health, perhaps this is determining the increased mosquito risk we identified? You can read more in our publication here.

Expanding the investigation to look at urban freshwater wetlands, it was found that there was a high degree of variability in local mosquito populations and that each wetland needed to be assessed with consideration to be given to site-specific characteristics. You can read more about our work investigating mosquito assemblages associated with urban water bodies in our publication here.

More research is underway in this field and my PhD student, Jayne Hanford, has already started collecting some fascinating data on wetland biodiversity and local mosquito populations.

While the focus of our studies is often prompted by concern about Ross River virus, interestingly, in recent years we’ve found considerable activity of Stratford virus. This is not currently considered a major human health concern but given how widespread it is, it raises concerns about the suitability of local wildlife, even in Western Sydney, to represent important reservoirs of mosquito-borne pathogens. You can read more about Stratford virus in our publication here.

The final piece of the puzzle is to understand the ecological role of mosquitoes. Where their potential health threats are deemed significant, how could management of mosquito populations have unintended consequences for other wildlife. What about the animals that eat mosquitoes? A number of years ago we did some research to determine the importance of mosquitoes in the diet of coastal bats. While there was no indication that mosquitoes are a critical component of their diet, they are still being snacked on and mosquito control programs need to consider any local ecological impacts.

Now, how am I going to squeeze all this into 15 minutes….

The presentation abstract is below:

What drives mosquito-borne disease risk in urban wetlands?

Webb, C. (1, 2), J. Hanford (3), S. Claflin (4), W. Crocker (5), K. Maute (5), K. French (5), L. Gonsalves (6) & D. Hochuli (3)

(1) Department of Medical Entomology, NSW Health Pathology, Westmead Hospital, NSW 2145; (2) Marie Bashir Institute of Infectious Diseases and Biosecurity, University of Sydney, Camperdown, NSW 2006; (3) School of Life and Environmental Sciences, Faculty of Science, The University of Sydney, Camperdown, NSW, 2006; (4) Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, 7000; (5) Centre for Sustainable Ecosystem Solutions, Biological Sciences, Faculty of Science, Medicine & Health, University of Wollongong NSW, 2522; (6) School of Arts and Sciences, Australian Catholic University, North Sydney, NSW, 2060.

Managing pest and public health risks associated with constructed and rehabilitated urban wetlands is of increasing concern for local authorities. While strategic conservation of wetlands and wildlife is required to mitigate the impacts of urbanisation and climate change, concomitant increases in mosquitoes and mosquito-borne disease outbreak risk must be addressed. However, with gaps in our understanding of the ecological role of mosquitoes, could control strategies have unintended adverse impacts on vertebrate and invertebrate communities? A series of studies were undertaken in urban wetlands of greater Sydney to investigate the role of land use, wetland type and wetland aquatic biodiversity in driving the abundance and diversity of mosquito populations. A diverse range of mosquitoes, including key pest an vector species, were found in urban environments and mosquito-borne pathogens were detected in local populations, implicating local wildlife (e.g. water birds and macropods) as potential public health risk factors. Estuarine wetlands are locally important with the percentage of residential land and bushland surrounding wetlands having a negative effect on mosquito abundance and species richness while the amount of industrial land had a significant positive effect on species richness. Mosquito control in these habitats is required but insectivorous bats were identified as mosquito predators and the indirect implications of mosquito control should be considered. The aquatic biodiversity of urban freshwater wetlands influenced the species richness of local mosquito populations indicating vegetation plays an important role in determining local pest species. However, the matrix of wetland types also influences the abundance of mosquitoes in the local area. These results demonstrate the need for site-specific investigations of mosquito communities to assist local authorities develop policies for urban development and wetland rehabilitation that balance the need for conservation with reduced public health risks.

To keep up to date on what’s happening at the conference, check out the program online or follow the conversation on Twitter.

 

Ross River virus in Melbourne, how did that happen?

aedesnotoscriptus

Health authorities in Victoria have been warning of mosquito-borne Ross River virus for much of the summer. The state is experiencing one of its worst outbreaks of the disease but cases have mostly been across inland regions. Now it’s hit Melbourne. How has this happened?

Ross River virus is the most commonly reported mosquito-borne disease in Australia. There are usually about 5,000 cases across Australia. However, in 2015 there was a major spike in activity with around 9,000 cases reported. It is a common misconception that the disease is only found in northern regions of Australia. I’m often told “I heard the disease is moving south from QLD?” That’s not the case.

The virus is just as much a natural part of the Australian environment as the mosquitoes and the wildlife that maintain transmission cycles.

While there are generally more cases in northern Australia, nowhere is safe. Some of the largest outbreaks have occurred in southern regions of Western Australia, South Australia, Victoria and even Tasmania.

The virus is widespread but is generally associated with rural regions. A driving factor in determining the activity of Ross River virus is that more than just mosquitoes are involved in outbreaks. The virus is maintained in the environment in native wildlife, especially kangaroos and wallabies. Even when and where there are high numbers of mosquitoes, without wildlife, outbreak risk is low. This is the reason why any clusters of locally infected cases in metropolitan regions are typical in areas where there are wetlands, wildlife and mosquitoes occurring together. We’ve seen this on the urban fringe of Sydney and Perth in recent years.

The announcement of locally acquired cases in the suburbs of Frankston and Casey, in Melbourne’s south-east, has taken many by surprise. Should it have?

Victoria is no stranger to mosquitoes and outbreaks of mosquito-borne disease. There are mosquito surveillance and mosquito control programs in place in many regions and historically there have been major outbreaks of mosquito-borne disease. From freshwater flood plains of the inland to the tidally flooded estuarine wetlands of the coast, Victoria has diverse and often abundant mosquitoes. But cases in the metropolitan region are rare.

Victorian mosquitoes are not all bad but over a dozen different mosquito species can spread Ross River virus.

The region where these cases have been identified are in proximity to bushland and wetland areas. There is no doubt plenty of mosquitoes and suitable wildlife too. While this is the first time local transmission has been documented, that doesn’t mean the virus hasn’t circulated in the past, or even that cases may have occurred.

For individuals infected but only suffering mild symptoms, the illness can be easily discounted as nothing more than a mild case of the flu. Without appropriate blood tests, these cases never appear in official statistics. For this reason, many mosquito researchers believe that the number of notified cases across the country is just the tip of the iceberg with many milder infections going diagnosed.

But why in Melbourne now?

It is difficult to know for sure. The two most likely explanations are that either environmental conditions were ideal for mosquitoes and suitable populations of wildlife were present so that the virus was much more active in the local environment than previously. The second explanation is that the virus may have been introduced to the region by a traveller or movement of wildlife. In much the same way Zika virus made its way from SE Asia to South America in the last few years, mosquito-borne viruses move about in people and animals, much less so than mosquitoes themselves (but that isn’t impossible either).

Victoria (as well as inland NSW) is experiencing one of its largest outbreaks of Ross River virus on record following significant flooding of inland regions. With so much activity of the virus in the region, perhaps an infected bird or person travelling to the metropolitan region brought the virus with them. When bitten by local mosquitoes, the virus started circulated among local mosquitoes and wildlife.

Most people infected by Ross River virus are bitten by a mosquito that has previously fed on a kangaroo or wallaby.

Once it’s made its way to metropolitan regions, the virus can be spread from person to person by mosquitoes. Common backyard mosquitoes, especially Aedes notoscriptus, can transmit the virus but as these mosquitoes are not particularly abundant, don’t fly vary far and will just as likely bite animals as humans, they’re unlikely to drive major urban outbreaks of the disease. This mosquito doesn’t pack the same virus-spreading-punch as mosquitoes such as Aedes aegypti that spreads dengue, chikungunya and Zika viruses. Aedes aegypti isn’t in Victoria.

We’re unlikely to see significant spread of Ross River virus across Melbourne but that doesn’t mean Victorians should be complacent. As there is no cure for Ross River virus disease, the best approach is to avoid being infected in the first place. Preventing mosquito bites is the best approach. For my tips and tricks on avoiding mosquito bites see this recent paper in Public Health Research and Practice as well as my article for The Conversation.

Keep an eye on the website of Victoria Health for more information.

 

 

 

 

 

West Aussies versus the local mozzies

This is a special guest post from Dr Abbey Potter, Senior Scientific Officer, Environmental Health Hazards, WA Health. I’m currently mentoring Abbey as part of The Public Health Advocacy Institute of WA (PHAIWA) Mentoring Program. Its been a great experience as we navigate through some of the strategies to raise awareness of mosquito-borne disease and advocate for better approaches to addressing the public health risks associated with mosquitoes.

fightthebite_wahealth_flyer

Living in WA, we’re all too familiar with the pesky mosquito. We know they bite but what we often don’t consider is that they can transmit serious and sometimes deadly diseases. In fact, a recent survey of locals indicated that knowledge of mosquito-borne disease is pretty limited, particularly among younger adults aged 18-34 years and those living in the Perth Metro. It’s pretty important we’re aware of the risks posed by these pint-sized blood suckers and how you can avoid them… and here’s why!

The Facts

On average, more than 1,000 people will be infected with a mosquito-borne disease in WA every year. Our mossies can transmit Ross River virus, Barmah Forest virus, West Nile virus (Kunjin substrain) and Murray Valley encephalitis virus. All four cause diseases that are debilitating at best, causing weeks to months of symptoms. Murray Valley encephalitis is limited to the north of the State but is so serious it can result in seizures, coma, brain damage and even death.

Forget the bush, most people bitten in their own backyard. West Aussies are all very prone to getting eaten alive while socialising outdoors but if you’re up in the north of the State, you’ve also got a much higher likelihood of being bitten while boating, camping or fishing or working outside, compared to the rest of the state.

And don’t think you’re off the hook when you head off on holidays. A further 500 WA residents return from overseas travel with an exotic mosquito-borne disease every year. Heading to Bali? Beware of dengue, especially young adult males who return home with the illness more than others. There is limited mosquito management in many overseas countries where disease-transmitting mozzies can bite aggressively both indoors and throughout the day. This catches West Aussies off guard, as we are accustomed to mozzies biting outdoors, around dusk and dawn. When you’re in holiday mode it’s likely that you’ll be relaxing, having a couple of drinks and not thinking about applying repellent. Oddly enough, mosquitoes may actually be more attracted to people whose body temperature is higher. This happens naturally when you consume alcohol, so best pull out the repellent before you crack your first beer.

Despite our attractiveness to mosquitoes, we aren’t really aware of the most effective ways to avoid bites or how we can do our bit to reduce breeding in our own backyards. If you live by the mantra Cover Up. Repel. Clean Up you’ll have no problems!

mandurah_sep2014

Western Australia has some amazingly beautiful wetlands but these saltmarshes around Mandurah can produce large populations of nuisance-biting mosquitoes!

Cover Up

If you know you are going to be outdoors when mosquitoes are active, wear loose, long-fitting clothing that is light in colour. Believe it or not, mosquitoes can bite through tight pants as tough as jeans – I’ve witnessed it!

If you’re staying in accommodation that isn’t mosquito-proof, consider bed netting.

Try to keep children indoors when mosquitoes are most active. If exposure can’t be avoided, dress them appropriately and cover their feet with socks and shoes. Pram netting can also be really useful.

Admittedly, it’s not always practical to wear long sleeves during our warm summer nights, so there are going to be times when you need to use repellent. Choose a product that actually works and apply it appropriately so it does the job. Despite our best intentions, this is where we often go wrong. There are a few basic things to cover here, so stick with it!

Ingredient: Science tells us that the best active ingredient for repelling mosquitoes is diethyltoluamide (DEET for short) or picaridin. You need to look for either one of these names on the repellent label under the ‘active constituents’ section.

Unfortunately, natural repellents and anything wearable (e.g. bands, bracelets or patches) have very limited efficacy. Experts don’t recommend you use them and I consider this very wise advice. It only takes a single mosquito bite to become infected and chances are you will receive at least one if you rely solely on a product of this nature. It just isn’t worth the risk.

mosquito_repellent_wristband_october2015

Percentage: The next thing to consider is the percentage of the active ingredient. This can range anywhere from 7% to 80% which can make choosing a repellent confusing. Just remember, the higher the percentage, the LONGER the product will remain active for. It doesn’t mean it will repel mosquitoes better.

A repellent containing 16-20% DEET will provide around 4-6 hours of protection, and is a good place to start. Repellents labelled ‘tropical strength’ usually contain greater than 20% DEET – they are useful when you spend longer periods exposed to mosquitoes or if you are heading to a region where dengue, malaria or Zika is problematic. Kids repellents usually contain picaridin or <10% DEET.

Sometimes it can be tricky to work out the percentage of the active ingredient. You can see the Bushmans example below states this clearly, but the other bottles list the ingredient in grams per litre (g/L). No need for complex maths – just divide by 10 and you have the magic number! For example, the RID label below reports the product contains 160g/L of DEET. This would convert to 16% DEET – easy!

You can see a few examples here of effective repellents:

repellents_potterpaper

How to Apply: No doubt we would all prefer if repellents didn’t feel quite so gross on our skin or didn’t smell so bad. Even I have to admit that before I moved into this field, I was guilty of putting just a dab here and a dab there. Unfortunately, this is flawed logic that will only result in you being bitten!

Repellents must be applied correctly to be effective. That means reading the label and applying it evenly to all areas of exposed skin. Remember to reapply the product if you are exposed to mosquitoes for longer than the repellent protects you for. You’ll also have to reapply the repellent after sweaty activity or swimming.

For more information on repellent use in adults and children, click here.

Clean Up

Mosquitoes need water to breed, but only a very small amount. Water commonly collects in a range of things you may find in your backyard including pot plant drip trays, toys, old tyres, trailers and clogged up gutters. Mosquitoes also love breeding in pet water bowls, bird baths and pools if the water is not changed weekly or they are not well maintained. Rain water tanks can also be problematic so place some insect proof meshing over any outlets. When you’re holidaying, cover up or remove anything that may collect water.

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If you need more official info from WA Health about mosquito-borne disease or simple ways to prevent being bitten click here. And if you want to read more about how much West Aussies know (or don’t know) about mossies, check out Abbey’s excellent paper here! Joint the conversation too on Twitter by following Abbey and Cameron.