How does a mosquito researcher mark the passing of seasons?

Winter has come and gone for another year. For many people it means packing away the footy boots and starting to shop for swimwear. What about mosquito researchers? How does the passing of seasons change their work?

One of the things I love about my job (and occasionally loathe) is that it is primarily driven by the weather. On a weekly basis, i have to keep an eye on local rainfall, temperature fluctuations, and tidal cycles. All these things have a strong influence on local mosquito abundance and diversity. Add extreme weather events into the mix and things can become quite unpredictable! I can’t ignore the wind either, ever tried catching a mosquito in a howling gale?

Mosquitoes can be found right through the year in Sydney. Generally though, the year for me is divided into a series of milestones.

Goodbye winter, hello spring (plus migratory birds, daylight saving and end to rugby league)

There is a sound I’ve come to dread in recent years. The “awk-awk-awk…” of the channel-billed cuckoo. This migratory bird moves into Sydney from New Guinea and Indonesia around August and it’s call is a kind of siren that warns of the upcoming mosquito season. Once I start hearing those calls, I better start planning the field work season ahead.

The long weekend in October, that coincides with an end to the rugby league season, means field work planning should really be in full swing.

If these birds and farewell to footy season aren’t strong enough reminders, once daylight savings kicks in from early October, I know I’ve got to start moving!

In Sydney, “mosquito season” has historically run from the start of November through to the end of April. Field work is well underway by the time the Melbourne Cup is run and won.

One of the interesting trends in recent years has been are ever increasing early start to mosquito season. While the start of spring if often punctuated by occasional hot conditions, mosquitoes have usually be slow to kick into gear. It isn’t until late spring that serious pest problems are reported. However, in recent years, the start of the season has got earlier and earlier.

It is becoming so common to see boosts in mosquito numbers in late September and early October that start dates of mosquito control and surveillance programs are moving forward.

Say goodbye to summer holidays

My summers are dictated by tides and rainfall. These are the events that bring water into local wetlands and trigger hatches of mosquitoes. My schedule will shift from year with differences in the timing of king tides and the pattern of rainfall.

What these shifts in environmental conditions mean is that I can be in the wetlands on Christmas Day or New Years Eve. Sometimes mosquito season sucks.

The Australia Day holiday is often an important date, especially if it occurs just as mosquito populations are on the rise or there is increased activity of mosquito-borne pathogens. I’m often dealing with plenty of media enquiries at this time.

The kids are back in school by February and Sydney is well and truly out of holiday mode. For me, this means much earlier and later working times as I try to dodge peak-hour traffic getting from field site to field site. There is nothing more likely to take the gloss off some early morning time in the wetlands than spending twice as long as usually in crawling traffic as I try to get mosquitoes back to the laboratories.

Easter bunnies, chocolate eggs, and outbreaks of mosquito-borne disease

While it may be tempting to think the Easter Long-weekend may mark the end of the mosquito season and chocolate egg fueled celebrations can commence, it is important to keep in mind that Easter moves about from year to year. This can have important implications for mosquito monitoring and public health interventions.

When the Easter falls at the end of March or early April, there can be greater mosquito-borne disease risks. In many areas of Australia, mosquito-borne disease caused by Ross River virus is more commonly reported in autumn than summer or spring. Depending on the temperatures, tides, and rainfall, there can be very abundant populations of mosquitoes and elevated mosquito-borne disease risk just as everyone is taking off on long-weekend camping trips or school holidays. In 2020, with Easter falling in the middle or April, the risks shouldn’t be too high (but lets just wait to see what the weather and mosquito populations are like).

An end to daylight savings is usually a pretty good marker. I’m often caught out the first week after our clocks go back and need a head lamp or torch to finish setting mosquito traps! However, the real end point to mosquito season is typically ANZAC Day. While there may be some mosquitoes about through to the early stages of May, it is usually only under exceptional circumstances (at least around Sydney).

Bring on the cold (and report writing)

Between May and September, temperatures get too cold for mosquitoes to be a problem. It is the cold overnight temperatures (as opposed to the occasional warm daily temperatures) that influence mosquito populations. As soon as we start getting overnight minimums consistently dropping below 10oC, mosquito activity generally starts to decline.

Winter is spent writing, teaching, sleeping, conferences, planning, and trying to sneak in some kind of holiday….

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If you’re a scientist, how do the seasons shift your schedule throughout the year? Join the conversation on Twitter!

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The long hot summer of mosquito and media wrangling

“Webb’s a mosquito researcher with NSW Health Pathology, and while it may sound like potentially the worst job in the world to the rest of us, it’s important work.” – Ten Daily, 14 Jan 2019.

Every summer I’m required to juggle those pesky mosquitoes and help out with requests from media. Over the past 6 months or so I’ve responded to about 70 media requests and here is a round up of some fun highlights and other bits and pieces.

There was a wide range of media requests this summer, from morning TV through to talkback radio, podcasts and live interviews via Skype. There was once a time when the only acceptable way to do a radio interview was via landline connected phone. This summer I did interviews via mobile, Skype, and various  smartphone apps! Times are a changing.

A fun segment on Channel 7’s ‘Sunrise’ breakfast show on why mosquitoes bite some people more than others; always a challenge taking in a cage a live mosquitoes to the studio, especially travelling in via public transport!

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A hot and dry summer must mean less mosquitoes, right?

The outlook for the 2018-2019 “mosquito season” was for it to be fairly routine. The Bureau of Meteorology was predicting a hot and dry summer under the influence of El Nino. At the time I wrote a piece for The Conversation highlighting that just because it was dry, that didn’t mean we wouldn’t see plenty of mosquitoes.

In coastal regions of Australia, tidal flooding of local wetlands often offsets any impact due to lack of rainfall. Mosquitoes such as Aedes vigilax certainly respond well and there were some very high mosquito numbers recorded in early spring. Usually, the media interest in mosquitoes starts increasing once the politicians break for the summer, this year there was plenty of interest early on!

NSW Health also issued a media release to get the community thinking about the potential mosquito impacts ahead of the summer holiday period and asked me to be the spokesperson. These warnings often prompt a different range of media interest, usually news bulletins for radio. Unlike the traditional radio interviews in which you’re responding to the host’s questions, only “grabs” (short statements regarding the topic) are required. I’ve learned there is a fine art to being concise in these statements and it pays to give some thought to what you’ll say ahead of calling up the news desk!

Some of the media coverage in early summer was less about bites and more about why mosquitoes disturb your sleep! I spoke with Channel Ten about how you can beat these bedroom buzzers! Here are some tips on beating the buzz of mosquitoes in the bedroom.

These concerns about mosquitoes in the bedroom prompted questions about the suitability of mosquito coils as a person protection measures. I’d written about this issue before but there was also some media coverage at the Daily Telegraph and Sydney Morning Herald.

There was also a funny segment on The Project:

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Warm weather, warm blood, and hungry mosquitoes

As summer kicked in, I did a bunch of “pre-season” interviews about the outlook for the mosquito activity ahead. One of them was with the Sydney Morning Herald. There was also a piece in Illawarra Murcury on the mosquitoes around Newcastle. I even chatted with ABC Illawarra about the mosquitoes bringing in the new year along the NSW coast. I also chatted with the team at the Daily Mail. Also the Daily Telegraph.

Once summer really hit (and the mosquitoes really started biting following heavy rains), everyone’s mind turned to one of the most commonly asked questions….why do mosquitoes bite me more than my friends? You can check out my contribution to a story by ABC Science below:

The usual coverage of mosquito impacts during the Australia Day holiday also popped up. Will my diet influence the likelihood of being bitten? I spoke with Channel Ten. The University of Sydney media team also put out a piece on why what you eat or drink makes not difference when it comes to stopping mosquito bites. A story picked up and republished by ABC News.

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Combining fieldwork and media requests

“Ballina council is calling in an expert to hunt for some ladies – Medical Entomologist Dr Cameron Webb will visit the area next week in search of blood sucking girls.” – EchoNet Daily, Ballina

While undertaking some work for Ballina Shire Council on the NSW far north coast, I helped out managing a few media requests associated with local mosquito problems and the work of council. It was fun squeezing in some print, TV, radio, and social media activities between the work in the wetlands.

I also participated in a “Q and A” on the Ballina Shire Council Facebook page where residents could ask questions about how best to protect themselves from mosquitoes. See here.

Mosquito-borne disease in the city

The detection of Ross River virus in mosquitoes around Sydney sparked some additional interest from media (and anxiety from local community). Coverage in Sydney Morning Herald here.  It prompted me to write an article about what the actual health implications were of finding the pathogen in a heavily urbanised areas such as the Parramatta River compared to the more bushland dominated Georges River.

The issue of wildlife and their role in urban transmission cycles of Ross River virus is always a tricky one. How do you balance wildlife conservation and mitigation of health risks? Together will colleagues I wrote about this at The Conversation.

The media coverage of the Ross River virus detection provided an opportunity for NSW Health Pathology to share some insights into how we research local mosquitoes and the pathogens they’re carrying. See below for a short video from the mangroves along the Parramatta River.

Did you know we monitor mosquitoes around the state to provide public health advice to @NSWHealth? Here’s our mozzie guru @Mozziebites (Dr Cameron Webb) explaining how we do this important work! pic.twitter.com/zpCTs7p3DL

— NSW Health Pathology (@NSWHPathology) January 10, 2019

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Declining insects, increasing mosquitoes, and the need to spray our backyards

One of the other stories bubbling along during the last year or so were the reports of declining global insect populations. I first spoke to the media about this issue back in early 2018. I was quoted in a couple of other stories too, clearly there was a lot of interest in this issue. This story gained plenty of attention and I spoke with various radio and print media about this challenge were facing with potential insect declines and how we can measure them. I even wrote an article about whether mosquitoes may be in decline too!

I spoke about this issue, and more generally about mosquitoes on an episode of the Science on Top podcast too.

There has been suggestions that insecticides may be contributing to declining insect populations. Earlier in the year, I was one of the coauthors of a paper that called for the need to better understand integrated pest control in our cities and become less reliant on insecticides. There was also an associated article at The Conversation. This was also republished at Domain.

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Floods in the north, floods in the south

The incredible flooding around Townsville in far north QLD created some major concern. Despite some initial concerns about increased mosquito risk, there weren’t any substantial increases in mosquito-borne disease reported. I spoke to ABC News about the potential risks.

The flooding that did trigger a big boost in mosquito numbers occurred in SE QLD and northern NSW. Local wetlands were inundated by tides and rain, resulting in some phenomenal numbers of mosquitoes in early autumn. I spoke to ABC and Great Lakes Advocate about the climatic factors that triggered this unusual mosquito activity.

Everyone was on weather watch late in the season too. A few extra downpours prompted concerns about more increases in autumn mosquito populations. I spoke with Sydney Morning Herald after a particularly wet weekend in March.

Finally, I helped the Australian Academy of Science make a video exploring why mosquitoes bite and how to stop them!

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Join the conversation on Twitter, did you catch me talking mosquitoes this summer? Did it help you protect your family from mosquito bites?

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Could a boombox (playing Skrillex) save you from mosquito bites?

There has been quite a buzz about some new research that suggests the music playing at your next backyard party may keep the mosquitoes at bay. Could it actually be true?

“As music is loved by many people, the development of music-based anti-mosquito control measures may represent an appealing alternative to strategies involving the use of harmful chemical insecticides.” – Dieng et al. 2019

Are mosquitoes monsters or sprites?

The study was recently published in the peer-reviewed journal Acta Tropica. The researchers (including one of my previous PhD students) exposed mosquitoes to the song “Scary Monsters And Nice Sprites” by U.S. electronic dub-step artist Skrillex while recording how long it took Aedes aegypti (these are the mosquitoes that transmit dengue viruses) to find a blood meal, how long they spent feeding, as well as tracking how much time was spent mating. The “blood meal” was provided by a restrained hamster and all experiments were conducted in the laboratory.

“Adults entertained with music copulated far less than their counterparts kept in the environment where there was no music entertainment.” – Dieng et al. 2019

Unfortunately, the researchers didn’t explain why they decided to use this particular song, only describing it as “…characterized as noisy based on the resulting vibragram and strong sound pressure/vibration with constantly rising pitches”. It would have been interesting to include a couple of other songs in the testing too. Perhaps something a little more downbeat?

Once they had the song playing (ensuring the speakers weren’t located close enough to cause vibration to the cage containing mosquitoes), mosquitoes were released into the cage and behaviour was recorded for 10 minutes. Researchers recorded the time to first blood feeding attempt, number of blood feeding events, and number of mating events.

The results were interesting. Mosquitoes took longer to find a host, spent less time blood feeding and mated less often when exposed to the music. These differences in each measurement were statistically different too.

What does this mean for prevention of mosquito-borne disease?

This study has received plenty of media attention. See here and here and here. I spoke to ABC Sydney about it too (tune in from the 1:07).

While the results demonstrated some reduced likelihood of biting, it shouldn’t be interpreted that playing Skrillex’s music will protect yourself from mosquito bites. The reduced likelihood was pretty short lived, you’re pretty much guaranteed to get bitten despite the dub step blasting from the boombox.

There has always been an interest in understanding how sound impacts the behaviour of mosquitoes. Ultrasonic insect repellents have been sold in one way or another for a couple of decades. Now you can download apps to your smartphone that purport to use sound to repel mosquitoes. There really is no evidence that sound can provide protection from mosquito bites.

Digging deeper into the “Skrillex study”, the results indicate that even though there may be less chance you’ll be bitten while listening to this music, you’ll still be bitten. Even over the relatively short exposure periods in the laboratory study, the mosquitoes were still biting. Notwithstanding your tolerance of Skrillex’s brand of electronic music, who knows how loud you need to be playing it or how shifts in songs (and their associated pitches, frequencies, buzzes, and beats) may change the activity of local mosquitoes.

To prevent mosquito-borne disease, you need to stop all bites, not just some of them. Topical insect repellents will still provide better protection. Keep in mind that even a low dose DEET-based insect repellent will prevent all bites from Aedes aegypti for a few hours in laboratory testing.

See the full paper here:

Dieng, H., Chuin, T.C., Satho, T., Miake, F., Wydiamala, E., Kassim, N.F.A., Hashim, N.A., Vargas, R.E.M. and Morales, N.P., 2019. The electronic song “Scary Monsters and Nice Sprites” reduces host attack and mating success in the dengue vector Aedes aegypti. Acta Tropica. [online]

 

Join the conversation on Twitter, if music could keep mosquitoes away, what music would you want that to be?

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Photo at the top of this article by Eric Nopanen on Unsplash

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Mosquitoes feed on frogs, very small frogs…

I was excited to be asked back on the Science on Top podcast recently to record an episode about mosquitoes, currently declines in insect populations (are mosquitoes on the way out too?), and whether recent flooding in north QLD would result in increased mosquito populations and risk of mosquito-borne disease outbreak.

Please subscribe to the podcast, its a really fun and relaxed look at whats making headlines in the science world. The crew themselves describe the podcast as:

The Australian podcast about science, health and technology news. Join Ed Brown and his panel of co-hosts each week as we talk about the latest and coolest research and discoveries in the world of science. We’re joined by special guests from all over the science field: doctors, professors, nurses, teachers and more.

If you’re interested, you can chase up my previous guest spot with them talking “Everything Zika” back in 2016.

I still hold some aspirations of starting my own podcast. Problem is finding the time (there isn’t even enough time to catch up on my podcast “to do” list). Perhaps this is a project for the coming summer.

Would you listen to a podcast about mosquitoes and the people who study them?

You can catch up on a couple of other podcasts I’ve guested on over the past few years. Check out Flash Forward (The Ultimate Swatting) and Arthropod (Getting to Know Mosquitoes).

Oh, and mosquitoes do feed on frogs. Frog blood, not the whole thing. It would have to be a very small frog…

 

 

 

Can citizen science help stop mosquito-borne disease outbreaks?

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 #CitSciOz18

A Guam visit to battle Zika virus and discover new mosquitoes

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.

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.

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!

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“.

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)

 

Preserve and protect? Exploring mosquito communities in urban mangroves

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?

 

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!

Lessons from the dengue outbreak in Hawaii

There are millions of cases of mosquito-borne disease world wide every year so why should we care about a few dozen dengue cases in Hawaii?

Hawaii is no stranger to dengue. There have been outbreaks first dating back to the 1840s. Travellers, including returning residents, are diagnosed with dengue routinely. However, this is the first outbreak of locally-acquired infection since 2011.

As of 17 November 2015, Hawaii Department of Health reports there have been approximately 65 locally acquired cases on Hawaii Island (aka Big Island) including both residents and visitors. Why has this happened and what lessons can be learned from the outbreak?

[update: As of 29 January 2016, there have been 242 confirmed cases of locally acquired dengue.]

Hawaii provides a fascinating example of the implications (as well as study of spread) of exotic mosquito invasions. With no endemic mosquito species, the pest species found in the Hawaiian islands have all been introduced from elsewhere.

The first mosquito to make it to Hawaii was Culex quinquefasciatus. It is thought to have arrived on a boat from Mexico in the mid 1820s. Interestingly, with no native mosquitoes in Hawaii, there was no word to describe them so they were initially referred to as “singing flies”.

In recent years, it has been the role of Culex quinquefasciatus in the spread of avian malaria that’s been grabbing the headlines. However, in the last few weeks, it has been Aedes aegypti and Aedes albopictus playing a role in the local spread of dengue virus in the spotlight. These two container-inhabiting mosquitoes are the key vectors of dengue viruses (as well as chikungunya, yellow fever and zika viruses) internationally. They’re driving the outbreak now as they have in the past.

There was an outbreak of dengue in 2001 with a total of 122 locally acquired cases. Cases were reported from Maui, Oahu and Kauai with the outbreak thought to have been triggered by travellers from French Polynesia where there was a major outbreak underway at the time. Between 1944 and 2001, the only cases of dengue reported in Hawaii were imported with travelers. Firstly, this highlights how important it is to understand the pathways of infected people, this can help guide assessments of risk.

This was also done from the potential introduction of West Nile virus into Hawaii. Analysing the movement of travelers from regions of endemic mosquito-borne disease has also been used to assess the risk of chikungunya virus introduction to North America.

It was believed that Aedes albopictus played an important role in this 2001 outbreak. This mosquito was not a significant presence in Hawaii until the 1940s. More importantly, Aedes albopictus is not exclusively found in water-holding containers in urban area. Unlike the other vector of dengue viruses, Aedes aegypti, Aedes albopictus is also found in bushland habitats. This makes mosquito control just a little more difficult when authorities need to look beyond the backyard.

Previous dengue outbreaks in Hawaii were thought to have been driven by Aedes aegypti. These outbreaks were significant with an estimated 30,000 cases in the early 1900s followed by approximately 1,500 cases around Honolulu in the period 1943-1944. While not necessarily easy to manage, outbreaks of dengue driven primarily by Aedes aegypti can be strategically targeted by residual insecticide treatments and community education. That education focuses on raising awareness of the public health risks associated with mosquitoes and the need to remove opportunities for mosquitoes to be breeding around dwellings. This model is essentially what is in place to address occasional outbreaks of dengue in Far North Queensland, Australia.

The current outbreak has raised concern in the community. Shelves of stores have been emptied of insecticides and repellents. Community meetings have been held by local authorities to provide information on dengue and address concerns on the Big Island. You can watch some of the meetings here. You can see some of the health promotion (aka “Fight the Bite”) flyers here.

Community engagement is important. An indirect impact of this engagement though is that the total number of confirmed cases of dengue on the Big Island is likely to rise over coming weeks. Not necessarily due to new cases but a greater likelihood that older cases will now be diagnosed through blood tests. Even those who may be suffering a mild illness are likely to be tested for infection and may end up in official statistics.

This dengue outbreak is a reminder to authorities across the world that where suitable mosquitoes are present, a risk of mosquito-borne disease outbreak is possible. The mosquitoes provide the tinder and it only takes the spark of an infected traveler to ignite an outbreak. We saw this in 2014 with the first outbreak of dengue in Japan for 70 years. We’ve seen it this year with local transmission of chikungunya virus in Spain and other outbreaks across Europe.

For Australian authorities, ensuring there are strategic responses in place to address the risk of exotic mosquito introduction, as well as outbreaks of disease, is critical. What this outbreak in Hawaii reminds us is that if Aedes albopictus becomes established in our major cities, it is only a matter of time before we see local outbreaks of dengue, chikungunya or Zika viruses.

What is it like if a loved one comes down with dengue? Check out the channel of YouTube stars Charles Trippy and Allie Wesenberg as they document their brush with mosquito-borne disease during this outbreak.

[Update: Implications for potential Zika virus spread] The recent spread of Zika virus in the Americas has raise concerns by health authorities. In particular, the spread of the virus to North America. What about Hawaii? There has already been one case of microcephaly in Hawaii with a baby born on Oahu to a mother who had been residing in Brazil. The pregnant women was infected in South America, not Hawaii. However, authorities should be on alert as travellers from the Americas, or the Pacific, have the potential to introduce the virus and the mosquitoes currently present in Hawaii spreading dengue viruses are the same that spread Zika virus.

 

 

 

 

 

 

 

Why would a Californian drought trigger an outbreak of mosquito-borne disease?

Mosquitoes need water almost as much as they need blood so why is it a drought could cause an outbreak of mosquito-borne disease? Why does the drought in California mean less water but more mosquito-borne disease?

More than just water

All mosquitoes need water. It could be a teaspoon of water in a pot plant base or an expanse of wetlands inundated by tides. Following flooding, health authorities are typically quick to issue public health warnings about increased risk of mosquito-borne disease. However, more mosquitoes doesn’t always mean more mosquito-borne disease.

Mosquitoes need blood. As well as biting people, they also bite animals. Outbreaks of mosquito-borne disease typically requires the presence of wildlife, animals that act as reservoirs for the disease-causing viruses.

Drought is hitting California hard (Source EPA via Huffington Post)

Mosquitoes, drought and West Nile virus

West Nile virus is a mosquito-borne pathogen generally spread between birds and people by mosquitoes. Culex mosquitoes they appear to play the most important role in West Nile virus transmission in urban environments, particularly Culex pipiens.

These mosquitoes are generally not breeding in wetlands. They’re found in artificial structures ranging from backyard containers and neglected swimming pools to stormwater pipes and drains. These mosquitoes have moved out of the swamps and into the suburbs! They’ve also moved into the constructed wetlands popping up throughout the suburbs too.

Rather than water birds associated with wetland environments, the birds playing a key role in West Nile virus transmission are small songbirds common in urban areas. These birds roost in large numbers and are the target the the Culex mosquitoes that preferentially feed on birds. It is important to keep in mind that there is still a lot of learn about how the roosting behaviour of birds influences their exposure to West Nile virus.

During “dry” conditions, bird populations are concentrated in urban areas (where humans provide water and food) and mosquito populations associated with urban water-holding structures increase. During “wet” summers, bird populations may be more widely dispersed through the environment with many birds roosting and foraging well away from residential areas and reducing the contact between birds, mosquitoes and people. When the “dry” summers arrive, birds move back close to the people. People who provide water.

The Culex pipiens group of mosquitoes play an important role in the transmission of West Nile virus and are closely associated with urban environments. They like biting birds. (Photo: Stephen Doggett, NSW Health Pathology)

In the absence of rain, water stagnates in stormwater pipes and drains providing favourable conditions for mosquitoes. During “wet” summers, the mosquitoes are flushed out by increased water flows and, even if they don’t, permanent habitats are more likely to support populations of mosquito predators such as fish.

During “dry” summers, people also start storing water around the home. Once water restrictions kick in, the desire to keep the garden looking healthy can potentially pose an indirect health risk to the homeowner as they hoard water around the home that provides habitat for mosquitoes.

In short, dry conditions help concentrate mosquitoes and birds in close proximity to people and increase the risk of mosquito-borne disease outbreaks.

Mosquito control in Texas in response to an outbreak of West Nile virus raised much concern within the community. It can sometimes be difficult to balance the need for mosquito control with community engagement to allay fears of insecticide -based human health risks (Source: CDC)

An outbreak in Texas in 2012

West Nile virus was first introduced into North America in 1999. Despite rapidly spreading across the continent in the subsequent years, the numbers of outbreaks steadily declined and, to some extent, it fell of the radar as a serious public health concern. There was a resurgence of the disease in 2012 with an outbreak primarily focused in Texas.

There was a substantial increase in the number of cases compared to previous years with an unusually warm spring thought to have played an important role in driving the outbreak. Health authorities were warned that outbreaks of this nature may continue.

West Nile virus and the Californian drought

For the past couple of years, California has been hit with one of its worst droughts in decades. It is having widespread impacts and may also be increasing mosquito-borne disease. Californian authorities have been battling potential public health risks associated with mosquitoes on many fronts. There were record numbers of deaths due to West Nile virus disease in 2014 and exotic mosquitoes were detected. This included an Australian mosquito that was found in Los Angeles.

It is relatively early in California’s mosquito season but West Nile virus has already been detected. Health authorities are warning that another bad year for West Nile virus activity could be ahead despite the ongoing drought. There is already a suggestion that the severity of the current drought may be exacerbated by climate change and that climate change may be playing a role in future West Nile virus risk internationally.

There is little doubt that prolonged drought will impact Californian residents in many ways and an increased risk of mosquito-borne disease is just one of them. Fortunately, mosquito and vector control agencies in California work closely with local health authorities to monitoring mosquito and pathogen activity to provide warnings of increased risk. However, there is responsibility for everyone to ensure that the ways in which water is conserved around the home doesn’t increase the risks associated with mosquitoes.

If you’re worried about keeping your pot plants well watered but don’t want to provide a home for mosquitoes, fill the saucer with sand. It will keep the moisture in place but there is no “free water” for mozzies to use!

If you’re not able to “dump and drain” water holding containers, make sure that they’re covered to stop mosquitoes getting in or out. If you’ve got a swimming pool that’s neglected, start chlorinating it or release fish to eat through any mosquitoes. There are also a few mosquito control products that could be used, the most appropriate would probably be the insect growth regulator methoprene, it will stop mosquitoes emerging from the water holding container.

Why not share your tips on saving water around the home while not increasing opportunities for mosquitoes on Twitter?

The photo at the top of this post is taken by Dawn Ellner (see original photo here)