How far do mosquitoes fly?

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There is no single answer to one of the most commonly asked questions I’m asked. “How far does a mosquito fly?” Notwithstanding those blown long distances by cyclonic winds or transported in vehicles, the distances travelled by mosquitoes varies greatly from mosquito to mosquito. But how do scientists work it out?

My latest published research demonstrates that Australia’s saltmarsh mosquito (Aedes vigilax) flies many kilometres from urban estuarine wetlands. This has great implications for improving our understanding of their role in outbreaks of mosquito-borne disease as well as designing mosquito control programs.

There are a few different ways you can work out how far mosquitoes fly.

Firstly, given we know that mosquitoes are closely associated with certain habitats, it is sometimes possible to track back collections of mosquitoes to their preferred habitats. For example, knowing a coastal wetlands mosquito is found many kilometres away from the nearest estuarine wetland may indicate it disperses widely.

Secondly, scientists can conducted mark-release-recapture experiments. In these studies, mosquitoes are marked with some kind of substance, released, and then specimens collected in traps operated in a surrounding network can be checked to see how many of those marked mosquitoes have been recaptured and how far they’ve travelled.

In this recently published study, I marked over 200,000 Aedes vigilax with a fluorescent powder (usually used to create paint) and released them close to their larval habitats in estuarine wetlands along the Parramatta River. For the next week, I set dozens of traps around the local area hoping to recollect some of those marked mosquitoes. By scanning the mosquitoes under a UV light, the marked mosquitoes were (relatively) easily identified.

Recapture rates for these types of experiments are notoriously low. While I was only able to recapture less than 1% of those marked mosquitoes released, marked mosquitoes were recaptured many kilometres from their release point. The results demonstrated that these mosquitoes of pest and public health concern disperse so widely from saltmarsh and mangrove habitats that their impacts can be felt quite widely, highlighting the need for targeted mosquito control to minimise potentially widespread pest and public health impacts.

There is an important implication here for current “mosquito aware” urban planning strategies. The incorporation of “buffer zones” between residential developments and mosquito habitats is often proposed but this research clearly demonstrated that this strategy just isn’t practical when it comes to saltmarsh mosquitoes. They just fly too far!

While this study demonstrated marked mosquitoes were travelling up to 3km, other work I’ve done has highlighted how differently the dispersal ranges of mosquitoes can be.  In a study of yellow fever mosquitoes (Aedes aegypti) in far north QLD, we found marked mosquitoes were only traveling between 100-200m. Similarly, other work with Australian backyard mosquitoes (e.g. Aedes notoscriptus) has shown they don’t fly more than 200m. That’s still enough to fly over from your neighbour’s backyard full of mosquito breeding opportunities.

There is a practical application to this work for the management of dengue in far north QLD. Knowing that the mosquitoes involved in transmission are flying less than 200m, mosquito surveillance and control can be concentrated around the homes of those infected individuals. A great example of how understanding mosquito biology can better inform cost-effective response strategies.

There is still plenty to learn about the dispersal of mosquitoes in Australia. I’ve got some ideas so if you’re looking for a research projects, get in touch!

Check out the Journal of Medical Entomology for the full paper titled “Dispersal of the Mosquito Aedes vigilax (Diptera: Culicidae) From Urban Estuarine Wetlands in Sydney, Australia“.

The abstract is below:

Aedes vigilax (Skuse) is a pest and vector species associated with coastal wetlands and the abundance of this mosquito has been identified as contributing to increased risk of mosquito-borne disease outbreaks. As urban development continues to encroach on these coastal wetlands, pest and public health impacts are becoming of increasing concern and in the absence of broadscale mosquito control. Urban planners are looking to buffer zones and other land use planning options to minimize contact between mosquitoes and humans but gaps in the understanding of dispersal ranges of mosquitoes hamper the adoption of these strategies. A mark-release-recapture experiment was conducted to measure the dispersal of this mosquito from an urban estuarine wetland in Sydney, Australia. An estimated total of over 150,000 wild caught female mosquitoes were marked with fluorescent dust and then released. A network of 38 traps was then operated for 5 d within an area of 28 km2. A total of 280 marked mosquitoes was recaptured, representing less than 1% of the estimate 250,000 marked mosquitoes released. Marked mosquitoes were recaptured up to 3 km from the release point, providing an insight into the dispersal range of these mosquitoes. The mean distance traveled by marked mosquitoes was 0.83 km, a result reflecting the greater proportion of marked mosquitoes recaptured near release point. The findings of this study indicate that effective buffer zones between estuarine wetlands and high-density urban developments would be an impractical approach to minimizing pest and public health impacts associated with this mosquito.

Join the conversation on Twitter or check out some of the other articles I’ve written on mosquitoes and other biting insects at The Conversation. You can also learn more about Australia’s wonderful mosquitoes in the award winning field guide available from CSIRO Publishing.

 

 

 

Ross River virus in Sydney, should we be worried?

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Health authorities in NSW recently released warnings to avoid mosquito bites following the detection of Ross River virus in wetlands along two major river systems in metropolitan Sydney. Whats going on and should these findings be something to be worried about?

What is Ross River virus?

Ross River virus is the most commonly reported mosquito-borne disease in Australia. The virus is spread by the bite of a mosquito and about 40 different mosquito species have been implicated in its transmission.

The disease caused by Ross River virus is not fatal but it can be severely debilitating.

Thousands of Australian’s are infected each year. We have some idea of the quantity of infections as Ross River virus disease is classified as a notifiable disease. While the official statistics indicate there are around 5,000 cases of illness across the country (there are between 500 and 1,500 cases per year in NSW), there are likely to be many more people that experience a much milder illness and so never get blood tests to confirm infection. These people won’t appear in official statistics.

What makes Ross River virus a fascinating pathogen to study is also what makes it extremely difficult to predict outbreaks. Transmission cycles require more than just mosquitoes. Mosquitoes don’t emerge from local wetlands infected with the virus, they need to bite an animal first and become infected themselves before then being able to pass on the pathogen to people.

It is generally thought that kangaroos and wallabies are the most important animals driving outbreak risk. However, we’re starting to better understand how the diversity of local wildlife may enhance, or reduce, likely transmission risk.

How was the virus found in Sydney?

The recent warnings have been triggered by the results of mosquito trapping and testing around Sydney. NSW Health coordinates an arbovirus and mosquito monitoring program across the state and this includes surveillance locations within metropolitan Sydney.

Mosquitoes are collected using traps baited with carbon dioxide. They trick the mosquitoes into thinking the trap is an animal. By catching mosquitoes, we can better understand how the pest and public health risks vary across the city and the conditions that make mosquitoes increase (or decrease) in numbers.

It mostly occurs around the metropolitan region’s northern and southern river systems and generally associated with estuarine or brackish-water wetlands. In these areas, there are often abundant mosquitoes and wildlife. Along the Parramatta River, there are often abundant mosquito populations but given the heavily urbanised landscape, there aren’t many kangaroos and wallabies.

The nuisance impacts of mosquitoes, such as Aedes vigilax, dispersing from the estuarine wetlands of the Parramatta River can create challenges for local authorities. These challenges include targeted wetland conservation and rehabilitation strategies along with ecologically sustainable mosquito control programs.

Is the detection of the virus in Sydney unusual?

The detection of Ross River virus is not that unusual. Detection of Ross River virus (as well as other mosquito-borne viruses such as Stratford virus) along the Georges River in southern Sydney is an almost annual occurrence. The local health authorities routinely issue warnings and in recent years have successfully used social media to spread their messages.

Ross River virus has also previously been detected along the Parramatta River.

While there have been confirmed local clusters of locally acquired Ross River virus in the suburbs along the Georges River, there have been no confirmed cases of Ross River virus disease in the suburbs along the Parramatta River.

There are a few reasons why more disease isn’t reported. Health authorities are active in promoting personal protection measures, sharing recommendations on insect repellent use and providing regular reminders of the health risks associated with local mosquitoes. It isn’t unreasonable to think these actions raise awareness and encourage behaviour change that reduces mosquito bites and subsequent disease.

Along the Georges River, there is clearly a higher risk of infection given the more significant wildlife populations, especially the wallabies common throughout Georges River National Park. By comparison, along the Parramatta River there are fewer bushland areas and virtually no wallabies (except for the occasional one hopping across the Sydney Harbour Bridge). Even in the wetland areas around Sydney Olympic Park, there is abundant bird life, meaning mosquitoes are probably more likely to be biting the animals than people. A study looking at the blood feeding preferences of mosquitoes in the local area found that animals were more likely to be bitten, mosquitoes actually only fed on humans about 10% of the time.

It is important that if you’re spending a lot of time outdoors in these areas, especially close to wetlands and bush land areas at dawn and dusk when mosquitoes are most active, take measure to reduce the risk of being bitten. Cover up with long sleeved shirts and long pants and apply an insect repellent. Choose a repellent that contains either DEET (diethlytoluamide), picaridin, or oil of lemon eucalyptus. Apply it to all exposed skin to ensure there is a thin even coat – a dab “here and there” doesn’t provide adequate protection. More tips here.

Also, keep in mind that just because cooler weather has arrived, the health risks associated with mosquitoes remain. That means keeping in mind that mosquitoes will be out and about just as football and netball seasons start so take along some mosquito repellent to training nights.

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Join the conversation on Twitter!

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Giant mosquitoes are invading my backyard!

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“I’ve never seen anything like it. I actually heard it before I saw it!”

I get more than a dozen emails, tweets, or phone calls every summer like this. Excited (terrified?) correspondence asking about the “giant” mosquito captured in the backyard or buzzing about windows.

Toxorhynchites speciosus is as “good” a mosquito as there can be. First, it is a gorgeous creature. Almost four times the size of a typical mosquito, it is a large dark and shiny mosquito with bright metallic patterns.

There are around 70 species of Toxorhynchites mosquitoes around the world but only a few species found in Australia. The mosquito is reasonably common, but rarely very abundant. It is found along the eastern and north coast of Australia, stretching from Sydney through to Darwin.

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The larvae of Toxorhynchites speciosus are large and easily spotted in water-holding containers around the backyard

This is one of the few mosquitoes that don’t need blood. Unlike almost all other mosquitoes, the females of which need blood to develop their eggs, Toxorhynchites speciosus doesn’t bite. It gets its energy from plant juices and nectar.

Even though it doesn’t bite, the sheer size of this mosquito makes it an imposing sight.

They most commonly lay eggs in water holding containers around the home. Pot plant saucers, bird baths, watering cans, buckets, bins and even tree holes and water-filled bromeliads. These are the same types of water-filled containers where you’ll find wrigglers of the pest mosquitoes Aedes notoscriptus and Culex quinquefasciatus.

They have a fascinating way of laying eggs. Unlike many other mosquitoes that elegantly stand on the water surface and lay up to 300 eggs in a neatly packed floating raft, Toxorhynchites lays single eggs. It  doesn’t even land on the water to lay eggs, it fires them into water while in mid flight!

Once an appropriate place to deposit an egg has been identified, the mosquito flies in a vertical loop, the loops getting ever smaller until the egg is ejected and into nearby habitats. A neat trick and avoids the risk of being eaten by a hungry spider or other predator waiting by to grab a mosquito coming in to lay eggs.

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A specimen of Toxorhynchites speciosus collected by Helen Mamas from the inner west suburb of Sydney, Newtown

Not only do these mosquitoes not bite, they even help out with a little pest mosquito control around the home.

While the mosquito wrigglers of mosquito mosquitoes feed on organic debris floating about in water bodies, the larvae of Toxorhynchites speciosus are predatory and feed on the wrigglers of other mosquitoes. Laboratory studies have shown that a closely related Toxorhnychites consumed over 300 Aedes aegypti  (aka the dengue mosquito) larvae during its development. In some parts of the world, a closely related mosquito is used as a biological control agent of the pests that spread dengue, chikungunya and Zika viruses.

While Toxorhynchites speciosus will chomp through plenty of wrigglers of Aedes notoscriptus each summer in Australian backyards, it is unlikely to make a huge difference in bites.

My experience in backyards across Sydney has shown that there is something of a tug-o-war between Toxorhynchites speciosus and other mosquitoes. While undertaking a project with Ku-ring-gai Council looking at backyard mosquitoes and their possible impact on backyard wildlife conservation efforts, I’d often find a fluctuating dynamic between the mosquito predators and their prey. Populations of Aedes notoscriptus or Culex quinquefasciatus would build up in bird baths and buckets, then Toxorhynchites speciosus would move in. They’re eat through all the other larvae, then once emerged and flown off, the other mosquitoes would move back in. And the cycle continued.

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Image of Toxorhynchites speciosus sent to be by David Lawson from the inner west suburbs of Marrickville, Sydney.

Next time you see a “giant mozzie” buzz by, think twice before you squish it. Oh, and keep in mind that this mosquito is also a movie star! Do you recognise it from Jurassic Park?

If you want to keep the pest mosquitoes out of your backyard, make sure you get rid of any water-holding containers. If you can’t throw them out, keep them covered.

Check to make sure your roof gutters and drains are clear of leaves and other debris so they flow freely. Check your rainwater tank is screened to stop the mozzies entering. And try not to kill the good guys who help keep the other mozzies at bay!

For more on how to better control insect pests in and around the home, read one of our latest publications on engaging urban stakeholders in the sustainable management of arthropod pests.

Find out more about Australia’s fascinating mosquitoes by checking out our “A Guide to Mosquitoes of Australia” via CSIRO Publishing!

 

Preserve and protect? Exploring mosquito communities in urban mangroves

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This is a special guest post from Dr Suzi Claflin. Suzi found herself in Sydney, Australia, (via Cornell University, USA) in 2015 to undertake a research project investigating the role of urban landscapes in determining mosquito communities associated with urban mangroves. She was kind enough to put this post together to celebrate the publication of our research in Wetlands Ecology and Management!

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Sometimes you’ve got to make hard choices for the greater good. These situations can arise anywhere, but here – as usual – we are concerned with mosquitoes. There’s a balancing act carried out by public health officials and wetland managers trying to both preserve endangered habitat and protect human health. In this guest post, I’ll explain the science behind research I recently published in collaboration with Dr Cameron Webb, and suggest one way forward for addressing human and environmental health concerns in urban wetlands.

During my PhD, I studied how the landscape surrounding small-scale farms affects the spread of a crop virus and the community of insect pests that carry it. When I came to Australia to work with Cameron, I was surprised to find myself applying the same type of landscape ecology to mosquitoes and mangroves in urban Sydney.

The misfortune of mangroves

Mangroves are real team players. They provide a range of services to the surrounding ecosystem and to the humans lucky enough to live near them. Mangroves are extremely effective at protecting the shoreline (but this can sometimes be a problem). They prevent erosion by gripping the soil in their complex root systems and buffer the beach by serving as a wave break. By filtering sediment out of the water that flows over them, mangroves also prevent their neighbouring ecosystems, such as coral reefs and seagrass forests, from being smothered.

Despite all their good work, mangroves have an almost fatal flaw; they prefer waterfront property. Unfortunately for them, so do humans. Urban and agricultural development has eaten away at mangroves, leaving them highly endangered.

The mosquito menace

Mozzies are a public health menace, because they spread human diseases like Ross River virus (RRV). Because of this, public health officials rightly spend time considering how to supress mosquito populations in order to reduce the risk of disease transmission.

Here’s where things get tricky: mangroves are great for mosquitoes.

That leaves public health officials and wetland managers in a difficult position. On the one hand, mangroves are delicate, at-risk ecosystems that need to be preserved. On the other, mangroves and surrounding habitats potentially harbor both the animal carriers of the RRV (e.g. wallabies) and a load of mosquitoes, which means that people nearby may need to be protected.

How can we do both?

 

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Dr Suzi Claflin trapping mosquitoes in the mangroves along the Parramatta River, Sydney, Australia.

 

The potential power of prediction

This is a hard question to answer. One approach is prediction: using measurements of the environment, like rainfall and tide level, to estimate what the mosquito community will look like in a given region. The mosquito community determines what management actions, like spraying an insecticide, need to be taken, based on the threat it poses to public health.

We set out to explore how the way we use land (e.g. for residential areas or industrial areas) near urban mangroves affects the mosquito communities that live in those mangroves. The project involved dropping over retaining walls, slipping down banks, and tromping through muddy mangroves along the Parramatta River in Sydney. We set mosquito traps (billy cans of dry ice with a container on the bottom) and left them overnight to capture the mozzies when they are most active. We did this at two points in the summer, to see if there was any change over time.

We found that yes, the way we use land around a mangrove makes a difference. Mangroves with greater amounts of bushland and residential land in the surrounding area had fewer mosquitos, and fewer species of mosquitos. On the other hand, mangroves with greater amounts of industrial land surrounding them had a greater number of mosquito species, and those surrounded by greater amounts of mangrove had more mosquitos.

And, just to muddy the waters a bit more (pun intended), several of these relationships changed over time. These results show that although prediction based on the surrounding environment is a powerful technique for mangrove management, it is more complicated than we thought.

Another way forward: site-specific assessments

Our work suggests another way forward: site-specific assessments, measuring the mosquito community at a particular site in order to determine what management approaches need to be used. This is a daunting task; it requires a fair number of man-hours, and mangroves are not exactly an easy place to work. But it would be time well spent.

By assessing a site individually, managers can be confident that they are taking the best possible action for both the mangroves and the people nearby. It turns out that the best tool we have for striking a balance between environmental and public health concerns, the best tool we have for preserving and protecting, is information. In mangrove management—as in everything—knowledge is power.

Check out the abstract for our paper, Surrounding land use significantly influences adult mosquito abundance and species richness in urban mangroves, and follow the link to download from the journal, Wetlands Ecology and Management:

Mangroves harbor mosquitoes capable of transmitting human pathogens; consequently, urban mangrove management must strike a balance between conservation and minimizing public health risks. Land use may play a key role in shaping the mosquito community within urban mangroves through either species spillover or altering the abundance of mosquitoes associated with the mangrove. In this study, we explore the impact of land use within 500 m of urban mangroves on the abundance and diversity of adult mosquito populations. Carbon dioxide baited traps were used to sample host-seeking female mosquitoes around nine mangrove forest sites along the Parramatta River, Sydney, Australia. Specimens were identified to species and for each site, mosquito species abundance, species richness and diversity were calculated and were analyzed in linear mixed effects models. We found that the percentage of residential land and bushland in the surrounding area had a negative effect on mosquito abundance and species richness. Conversely, the amount of mangrove had a significant positive effect on mosquito abundance, and the amount of industrial land had a significant positive effect on species richness. These results demonstrate the need for site-specific investigations of mosquito communities associated with specific habitat types and the importance of considering surrounding land use in moderating local mosquito communities. A greater understanding of local land use and its influence on mosquito habitats could add substantially to the predictive power of disease risk models and assist local authorities develop policies for urban development and wetland rehabilitation.

Dr Suzi Claflin completed her PhD at Cornell University exploring environmental factors driving the spread of an aphid-borne potato virus on small-scale farms. She is now a postdoctoral research fellow at the Menzies Institute for Medical Research in Hobart, TAS. In her spare time she runs her own blog, Direct Transmission, focusing on disease and other public health issues (check it out here). To learn more about her doctoral research, follow this link!

Could a podcast stop mosquito bites?

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This week I’m attending OzPod 2016: the Australian Podcast Conference, a workshop at the ABC, Ultimo. Celebrating International Podcast Day, the workshop brings together podcasters for “an event for the expanding podcast industry to escape the studio or office and meet with peers to share experiences, information, insights and ideas around audience acquisition and retention, new technologies, the rise of the podcast in traditional media, monetizing and of course the fine art of storytelling.”

 So, why am I going? I don’t even have a podcast!

I may not have a podcast now but I hope to start playing around with the platform soon as a complement to my other efforts to spread the word on science communication and public health awareness.

I’ve been thinking about kicking off a podcast for a while but have been a little reluctant due to time commitments. More importantly, I’ve also wanted to have a clear idea of what exactly I want to do.

In a previous life, I co-hosted a radio show on FBI Radio (during their test broadcast days) with my wife called “Good Morning Gidget”. It was a Saturday morning show of surf music and interviews with professionals involved in a wide range of coastal-based activities, from marine biologists to surf shop owners. Despite the early start on a Saturday morning, it was a load of fun. I’d also worked behind the scenes producing a couple of music shows. If I had more time, I really would have liked to pursue more work with community radio.

Perhaps podcasting will be the backup plan.

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It’s great to listen back to packaged interviews with radio, like the Health Report (I’m talking zika virus) but I was also lucky enough to have a chance to contribute to a few podcasts this year. I spoke with Science On Top about the outbreak of Zika virus and the implications it has for Australia, Flash Forward on what will happen if we eradicate mosquitoes from the planet and ArthroPod on what its like to study mosquitoes for a living!

All these were a lot of fun and were really motivating for me to want to get started with podcasting myself.

I feel like my experience with sound recording and ongoing engagement with media provides a solid background in most of the technical skills I need to get started. I’m hoping I’ll leave the OzPod 2016 conference with a few more tips on story telling and structuring a podcast too.

What I’ve been struggling with is format. I like the conversational nature of most podcasts but as I’ll probably be doing everything myself, perhaps a more structured and edited podcast is the go?

There are very few podcasts I listen to that are built around a one-person show. I’m not sure I could pull it off. Does anyone really want to listen to me ramble on for 20 mins about mosquitoes? 40minutes?

Sometime over the coming summer I hope to launch a short series of podcasts covering some of the basics of mosquito biology and how that relates to the ways we protect ourselves and our families from mosquito bites and mosquito-borne disease. I want to share my fascination with mosquitoes and explore some of the gaps in our understanding of mosquitoes, particularly their role in our local environment. 

Hopefully I can recruit some of my colleagues from around Australia for a chat too so we can share a little about the science behind our public health messages and what life is like to be chasing mosquitoes around swamps all summer

Sound like a good idea? Join the conversation on Twitter and let me know what you think, would you listen to a podcast about Australian mosquitoes?

 

 

 

 

 

 

Social media and blood suckers showcased at the International Congress of Entomology

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Digital technology is changing a lot about how we undertake entomological research and communicate the results of that research to the community and policy makers.

This week in Orlando, Florida, is the International Congress of Entomology (ICE). A huge gathering of entomologists from around the world. While it was a great pleasure to be invited to participate, I couldn’t get over there this time.

I will, however, have a chance to present my work in the Symposium “Entomology in the Digital Age”  Friday, September 30, 2016 (01:30 PM – 04:45 PM), Convention Centre Room W222 A.

In the presentation I’ll share some of the reasoning behind my use of social media to engage the community with both entomological research and public health communication. Most importantly, it will focus on some of the metrics I’ve recorded alongside my use of social media, maintaining a blog of research and writing for outlets such as The Conversation.

I’ve written about my use of social media and how it can help extend the reach of public health messages and presented on the topic alongside a range of great speakers at the 2014 Entomological Society of America meeting in Portland.

This time around, technology is playing an even more direct role in my presentation! I’ve pre-recorded my presentation and it will be shown to the audience on the day among other presentations. I’ll also be checking into the session to answer questions. Despite the fact I’ll need to be up around 1:30am due to time differences, it should be fun.

See the abstract below…

Taking entomological research from the swamps to the suburbs with social media

Cameron E Webb

Connecting scientists and the community is critical. This is particularly the case for medical entomologists working in the field of mosquito-borne disease where the translation of entomological research into improved public health outcomes is a priority. While traditional media has been the mainstay of public health communications by local authorities, social media provides new avenues for disseminating information and engaging with the wider community. This presentation will share some insights into how the use of social media has connected new and old communications strategies to not only extend the reach of public health messages but also provide an opportunity to promote entomological research and wetland conservation. A range of social media platforms, including Twitter, Instagram, and WordPress, were employed to disseminate public health messages and engage the community and traditional media outlets. Engagement with the accounts of traditional media (e.g. radio, print, television, online) was found to be the main route to increased exposure and, subsequently, to increased access of public health information online. With the increasing accessibility of the community to online resources via smartphones, researchers and public health advocates must develop strategies to effectively use social media. Many people now turn to social media as a source of news and information and those in the field of public health, as well as entomological research more generally, must take advantage of these new opportunities. doi: 10.1603/ICE.2016.94611


If you’re at ICE, you can also catch up with my PhD student David Lilly who’ll be presenting our research into the development of insecticide resistance in bed bugs as part of the symposium “New Insights into Biology, Resistance Mechanisms, and the Management of the Modern Bed Bug” Friday, September 30, 2016, 01:30 PM – 04:45 PM, Convention Center, West Hall F4 (WF4).

Novel insecticide resistant mechanisms in the common bed bug, Cimex lectularius

David Lilly, Cameron E Webb and Stephen Doggett

Introduction: Research on field strains of Cimex lectularius from Australia has identified widespread resistance to pyrethroid insecticides, but variability in the magnitude expressed. To determine if differences in resistance mechanisms exist, collected strains were examined for the presence of metabolic detoxification and/or cuticle thickening. Methods: The presence and relative contribution of detoxifying esterases or cytochrome P450 monooxygenases were assessed. Bed bugs collected from Parramatta (NSW), Melbourne (VIC) – 2 strains, ‘No.2’ and ‘No.4’, and Alice Springs (NT) were exposed in topical bioassays employing deltamethrin and two pyrethroid synergists: piperonyl butoxide (PBO) and EN16/5-1. PBO inhibits both monooxygenases and esterases, whereas EN16/5-1 will inhibit esterases only. Thus in a comparative bioassay, the results can infer the dominant enzyme system. The Parramatta strain was then selected to study the potential presence of cuticle thickening. Nine-day-old male bed bugs were exposed to filter papers treated with the highest label rate of Demand Insecticide®(200mL/10L of 25g/L lambda-cyhalothrin) and were grouped according to time-to-knockdown (< 2 hours, ≥ 4 hours, and survivors at 24 hours). Measurements of mean cuticle thickness at the transverse midpoint of the second leg tarsus were taken under electron microscope. Results/Conclusion: All strains possessed resistance that was inhibited by the synergists, with the Parramatta and Melbourne No.2 indicating esterase-dominance, and Alice Springs and Melbourne No.4 indicating cytochrome P450 monooxygenase-dominance. Cuticular measurements demonstrated that bed bugs surviving deltamethrin exposure had significantly thicker cuticles, denoting a novel form of resistance in these insects. doi: 10.1603/ICE.2016.92553

 

You can also see Stephen Doggett (co-author and photographer of A Guide to Mosquitoes of Australia) speaking on photographing mosquitoes to in the symposium “Insect Photography Symposium: Bringing the Small to the World.


You can join the conversation on Twitter and keep an eye on all the fun in Orlando by keeping an eye on the tweet stream!

 

Taking Australian wetland research to China

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My PhD student Jayne Hanford has been super busy this year. Not much more than a year into her candidature and she has already locked away a summer of research and has been presenting her findings at conferences here in Australia as well as overseas.

After recently sharing our research at the Society for Wetland Scientists Annual Conference held in Corpus Christi, Texas, USA and the Mosquito Control Association of Australia conference on the Gold Coast, Jayne is off to China for the 10th INTECOL International Wetlands Conference.

Her research is focused on understanding the links between wetland vegetation, aquatic biodiversity and mosquito populations. Better understanding of these links will assist management strategies that minimise actual and potential pest and public health risks associated with mosquitoes and urban wetlands.

Our abstract for the conference is below:

Is the Biodiversity Value of Constructed Wetlands Linked to their Potential Mosquito-Related Public Health Risks?

Jayne Hanford1, Cameron Webb2, Dieter Hochuli1

1School of Life and Environmental Sciences, The University of Sydney, Australia; 2Department of Medical Entomology, Westmead Hospital and The University of Sydney, Westmead, Australia

 Stormwater treatment wetlands constructed in cities can enhance the sustainability of urban biodiversity by providing wildlife refuge areas and habitat connectivity. However, the creation of wetlands for stormwater infrastructure can increase risks to public health and wellbeing by proliferating nuisance-biting and pathogen-transmitting mosquitoes. In severe cases, this proliferation can erode goodwill in the community for creating and protecting valuable wetland systems.  We compared mosquito assemblages at 24 natural and constructed urban wetlands in the greater Sydney region, Australia. Our aim was to determine if stormwater wetlands constructed with the goal to support high biodiversity value also had reduced associated mosquito risks. Wetlands were located across a gradient of urbanisation determined by surrounding human population density, and included sites with different aquatic and riparian habitat complexity and availability. Adult and larval mosquitoes and aquatic macroinvertebrates were sampled on two occasions through summer and autumn. Aquatic macroinvertebrates were used to derive health indices, as well as being a relative measure of aquatic diversity.  Diversity of adult mosquito species was high, and abundance varied greatly between wetlands. Macroinvertebrate assemblages were also highly variable between sites. Wetlands with greater habitat complexity had lower adult mosquito abundance and greater mosquito species diversity, compared to stormwater-specific wetlands with minimal available habitat. As expected, mosquito assemblages did not respond to urbanisation and aquatic macroinvertebrate assemblages per se, but appeared to respond to a complex suite of coarse and fine-scale features that may affect a wetland’s biodiversity value.  Effectively integrating wetlands into cities requires balancing their design for water infrastructure purposes, biodiversity resources and public health and wellbeing requirements. Understanding the risks as well as the benefits will enhance the value of constructed urban wetlands in sustainable cities while minimising public health risks posed by mosquitoes.

Jayne will be speaking in the “The next generation of wetland science: ecosystems, applications, and engineering” session in the Nanhu Room 1520-1530 on Wednesday 21 September.

You can keep an eye on whats happening in China by following Jayne on Twitter and checking the hashtag

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The Society for Wetland Scientists Annual Conference held in Corpus Christi, Texas, USA back in May included a paper by Jayne titled “Risky Wetlands? Conflicts between biodiversity value and public health” and prompted some great feedback and discussion among wetland scientists at the meeting. It was a successful trip and a timely reminder that I must get to one of the SWS meetings sometime soon, perhaps Puerto Rico?

Keep an eye out for Jayne’s research publications soon!