A Guam visit to battle Zika virus and discover new mosquitoes

Guam2017_Beach

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.

Guam2017_StormClouds

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.

Guam2017_Canoe

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!

Guam2017_EntomologyandEnvironmentalHealth

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“.

Guam2017_SpeciesList

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)

 

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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!

Around the world in a thousand fleas

fleas

The International Congress for Tropical Medicine and Malaria (ICTMM) kicks off in Brisbane, QLD, Australia this week running from 18 through 22 September. This is a big conference and wonderful for local researchers to be showcased to an audience of international scientists from our own backyard in QLD.

I couldn’t make this meeting unfortunately but luckily my wonderful PhD student Andrea Lawrence will be presenting some of our flea research as part of the Australian Society of Parasitology conference that is incorporated into ICTMM this time around.

Andrea has been doing some excellent research during her candidature and you can read some of it here [Evaluation of the bacterial microbiome of two flea species using different DNA isolation techniques provides insights into flea host ecology] and here [Integrated morphological and molecular identification of cat fleas (Ctenocephalides felis) and dog fleas (Ctenocephalides canis) vectoring Rickettsia felis in central Europe].

This week she will be sharing her research into the genetics of global cat flea populations. You can catch Andrea on Tuesday 20 September in the Zoonoses session in M4, 13:00-15:00.

Our abstract is below:

One thousand fleas from fifty countries: global genetic structure and morphometrics of the common cat flea (genus Ctenocephalides) reveals phylogeographic patterns and resolves the generic complex.

Andrea Lawrence, Cameron E. Webb and Jan Šlapeta

School of Life and Environmental Sciences (SoLES), Faculty of Veterinary Science, The University of Sydney, Australia and Department of Medical Entomology, The University of Sydney and Pathology West, ICPMR, Westmead, Australia

The common cat flea and its relatives (genus Ctenocephalides) are considered the most successful ectoparasites on earth. The widespread parasitisation of these insects on mammals closely associated with humans (e.g. dogs and cats) represents significant potential for vector borne disease transmission. Fleas of the genus Ctenocephalides represent a unique model to study the effects of modern human migration and geographic and climatic barriers on parasite diversity and diversification. We have amassed a world-wide collection of Ctenocephalides over a period of 7 years, and analysed over 1000 flea samples from ca. 50 countries representing all continents bar Antarctica. Novel integration of morphology, morphometrics and molecular identification and phylogenetics using a combination of four mitochondrial and nuclear DNA markers, reveals phylogeographic patterns and evolutionary relationships of global cat flea populations. These techniques provide resolution of the long disputed Ctenocephalides generic complex, which has not yet been definitively resolved despite its significance in veterinary and public health. Understanding of contemporary population structure inferred from global phylogeographic analysis has implications for parasite and flea-borne disease management. It is hoped that this work will form the authoritative estimation of the origin of the genus Ctenocephalides and the subsequent species evolution and migratory radiation.

Keep an eye on the official conference hashtag [#ICTMM2016] and why not follow Andrea on Twitter for more!

The lead image on this article is modified from Andrea’s paper, “High phylogenetic diversity of the cat flea (Ctenocephalides felis) at two mitochondrial DNA markers

 

 

 

 

 

Can social media help translate research to practice and promote informed public health messages?

I’m a Senior Investigator with the Centre for Infectious Diseases and Microbiology – Public Health. One of our primary focuses is translating research into improved public health outcomes. With NSW Population Health and Health Services Research Support Program assisting our work, we’re exploring new ways to achieve this objective. My experience of using social media was selected to be showcased among other case studies in 2015. 


Nuisance-biting mosquitoes and mosquito-borne disease are concerns for local authorities in Australia. 2015 saw the largest outbreak of mosquito-borne Ross River virus disease for more than 20 years with over 9,500 cases nationwide. In NSW, there were 1,633 cases compared to the annual average since 1993 of 742 cases per year. Notwithstanding the current outbreak, other endemic, as well as exotic, mosquito-borne pathogens represent future threats to public health.

As there is no large-scale mosquito control program in NSW, reducing the contact between mosquitoes and people is primarily achieved through the promotion of personal protection measures. NSW Health promotes the use of topical insect repellents in combination with behavioural change to avoid natural mosquito habitats and the creation of mosquito habitats around the home. This information is typically provided in the form of posters, brochures, online factsheets, and seasonal or outbreak-triggered public health messages issued by Local Health Districts or the NSW Ministry of Health.

With the emergence of new communications technologies, particularly the rise in popularity of social media, there are new opportunities for public health communications.

The aim of the current research was to determine the reach of public health messages through social media by tracking engagement, audience and relative value as assessed by media monitoring organisations and metrics provided by hosting services of social media platforms.

Assessing activities and processes

Dr Cameron Webb (CIDM-PH) has focused much attention on filling the gaps between current public health messages and findings from recent research into topical mosquito repellents.[1] For example, while public health messages provide accurate information on the insect repellents that provide the best protection, there is a paucity of information provided on how best these products should be used by individuals and those they care for.

Dr Webb’s engagement with mass media, online media (e.g. The Conversation), a personal blog (e.g. Mosquito Research and Management) and social media (e.g. Twitter) has resulted in substantial exposure of focused and informed public health messages. From mid-2014 through to the end of 2015, Dr Webb participated in over 80 mass media articles and interviews in print, online, radio and television media with public health information reaching an estimated audience of over 10 million people.[2] The focus of his messaging around mosquito-borne disease was to highlight the best way for the community to choose and use mosquito repellents; stressing the importance of active ingredients and application methods. This fills a gap in the current provision of public health information while also augmenting public health alerts and messages associated with the 2015 outbreak of Ross River virus disease.

Social media has become a “go to” source of information for much of the community. Information shared on Facebook, Twitter, Instagram, and YouTube has the potential to shape the habitats and behaviour of the community. Dr Webb is active on Twitter (currently followed by over 4,500 people); he uses the platform to engage with the social media accounts of journalists and broadcasters to establish a voice of authority in the field of mosquito-borne disease prevention and extend the reach and exposure of public health messages broadcast through mass media. Using Twitter to share links to informed articles following interviews reached hundreds of thousands of people by being shared by the social media accounts of journalists, media outlets, government organisations and community groups. During the 2014-2015 summer, tweets by Dr Webb reached an estimate 1.28 million people.[3]

Dr Webb regularly writes open access articles on his website, attracting around 250 daily visitors with over 117,000 article views.[4] In addition to his personal website, Dr Webb regularly contributes articles to The Conversation (a website for academics to share expert opinion and write about their latest research). His articles have attracted over 120,000 readers. However, one article “why mosquitoes seem to bite some people more” (published 26 January 2015) has alone been read by over 1.3 million people.[5] This “non-scholarly” writing not only establishes CIDM-PH scientists as authorities in public health matters but can also assist in directing the public to official health guidance provided on official websites and other sources.

Dr Webb’s activities provide a framework for how health authorities may engage with social media to extend public health messages. Organisations or individuals can connect health authority information with the community through media outlets. He has been invited to share his experiences in this field at local and international conferences and workshops including those coordinated by the Public Health Association of Australia, Australian Entomological Society and Entomological Society of America. In addition, Dr Webb has been invited to provide lectures on the benefits of social media for public health advocacy to undergraduate and post-graduate students at the University of Sydney.

While traditional messaging provided by health authorities will remain a staple in public health campaigns, social media provides a connection between traditional and emerging media and communication organisations. This increased connectivity between public health advocates, the media and community has the potential to greatly improve the awareness of mosquito-borne disease and increase the rate of uptake and application of strategic personal protection measures.

References

  1. Webb C.E. (2015). Are we doing enough to promote the effective use of mosquito repellents? Medical Journal of Australia, 202(3): 128-129.
  2. Estimated audience reported by Kobi Print, Media and Public Relations, University of Sydney, 23 April 2015, based on data provided by media monitoring organisation isentia.
  3. Estimated from total “tweet impressions” for the period October 2014 through April 2015 provided by Twitter Analytics (https://analytics.twitter.com/user/Mozziebites/home accessed 30 April 2015)
  4. Data provided by WordPress statistics (accessed 18 December 2015)
  5. Data provided by The Conversation metrics (accessed 18 December 2015)

This article was originally published by NSW Health showcasing some of the work within the NSW Population Health and Health Services Research Support Program. You can see the original article here.

Beware the thick skinned bed bugs (they’re beating our bug sprays)

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Think you’re got thick skin? You may be able to brush off the odd insult but for bed bugs, their thick skin can ward off fatal doses of insecticides! This is just one way they’re beating our commonly used bug sprays.

The resurgence of bed bugs over the past couple of decades has been great fuel for media and pest control companies alike. From Paris to London and New York to Sydney, infestations in all forms of accommodation has made headlines.

Eradicating an infestation of bed bugs can be tricky, tricky and expensive. While control within the hospitality industry is improving, the impacts of bed bugs are now being felt in lower socioeconomic groups in the community. There are often financial barriers to effectively controlling infestations and controlling infestations is not getting any easier.

Working out why bed bugs are hard to kill

David Lilly is currently a postgraduate student in our lab undertaking his PhD with the University of Sydney. He has been doing some great work and its wonderful as a supervisor to see him starting to publish some of his research as he approaches the end of his candidature.

We’ve already published some research on bed bugs and insecticide resistance and the role of metabolic detoxification in driving this resistance (you can read about that work via at Entomology Today). However, some of the most exciting research has just been published and indicates that “thicker skinned” bed bugs are more resistant to pyrethroid insecticides.

It is one thing to demonstrate insecticide resistance in a pest but understanding why that resistance occurs is critical if we’re to develop more effective strategies to control bed bugs.

This project was inspired by a study that demonstrated that mosquitoes resistant to insecticides had thicker cuticle. Could the same phenomenon occur in bed bugs?

Working with the Australian Centre for Microscopy & Microanalysis at The University of Sydney, we were able to capture images of cross-sections of legs from resistant and susceptible strains of bed bugs. Measuring the cuticle thickness at various points and comparing those between the two strains of bed bugs allowed an assessment of changes in cuticle.

Those bed bugs resistant to insecticides had thicker cuticle. In fact, the cuticle of the resistant bed bugs was around 15% thicker. Thicker the cuticle, the tougher it is for insecticides to penetrate.

Given human’s propensity to use insecticides, it is little wonder our most loathsome pests, such as mosquitoes and bed bugs, are developing resistance. While there really aren’t many other options available to control bed bugs, insecticides will remain part of our pest control tool kit. Alternative strategies are always being considered but while insecticides remain, we need to be mindful of the development of resistance and ways we can slow (or overcome) that process.

Bed bug’s thick skins grab the media’s attention

ABC24_BedbUgs_Lilly_17April2016

The research has already received international media coverage thanks to the fantastic team at University of Sydney Media and Communications team. A quick “google news” search turns up over 70 news items reporting on the paper! You can catch up with coverage at Popular Science (Australia), Wired, USA Today, Daily Mail, Sydney Morning Herald, BBC, Newsweek, Gizmodo and Mirror.

The abstract for our paper is below:

Thickening of the integument as a mechanism of resistance to insecticides is a well recognised phenomenon in the insect world and, in recent times, has been found in insects exhibiting pyrethroid-resistance. Resistance to pyrethroid insecticides in the common bed bug, Cimex lectularius L., is widespread and has been frequently inferred as a reason for the pest’s resurgence. Overexpression of cuticle depositing proteins has been demonstrated in pyrethroid-resistant bed bugs although, to date, no morphological analysis of the cuticle has been undertaken in order to confirm a phenotypic link. This paper describes examination of the cuticle thickness of a highly pyrethroid-resistant field strain collected in Sydney, Australia, in response to time-to-knockdown upon forced exposure to a pyrethroid insecticide. Mean cuticle thickness was positively correlated to time-to-knockdown, with significant differences observed between bugs knocked-down at 2 hours, 4 hours, and those still unaffected at 24 hours. Further analysis also demonstrated that the 24 hours survivors possessed a statistically significantly thicker cuticle when compared to a pyrethroid-susceptible strain of C. lectularius. This study demonstrates that cuticle thickening is present within a pyrethroid-resistant strain of C. lectularius and that, even within a stable resistant strain, cuticle thickness will vary according to time-to-knockdown upon exposure to an insecticide. This response should thus be considered in future studies on the cuticle of insecticide-resistant bed bugs and, potentially, other insects.

The full citation is: Lilly DG, Latham SL, Webb CE, Doggett SL (2016) Cuticle Thickening in a Pyrethroid-Resistant Strain of the Common Bed Bug, Cimex lectularius L. (Hemiptera: Cimicidae). PLoS ONE 11(4): e0153302. doi:10.1371/journal.pone.0153302

Download the paper for free directly from PLoS ONE!

Oh, and if you’re worried about picking up bed bugs on your next holiday, here are some tips!

 

Asian tigers and shifting mosquito control from the swamps to the suburbs

aedes_albopictus_SteveDoggettOne of the world’s most troublesome nuisance-biting mosquitoes is perfectly adapted to summer life in southern cities in Australia. This is bad news for communities in temperate climate regions in Australia that would otherwise be immune from the threats of exotic mosquito vectors of dengue and chikungunya virus otherwise limited to tropical regions of the world.

I’ve been invited to speak in the “Managing Current & Future Exotic Mosquito Threats” symposium at the Australian Entomological Society conference to share some of the experiences in temperate Australia regarding exotic and endemic mosquito threats and how the threat of the Asian Tiger Mosquito is being addressed.

Australia has annual activity of mosquito-borne disease. Around 5,000 people a year fall ill following a mosquito bite each year in Australia, most commonly due to Ross River virus. These pathogens are generally spread by native “wetland” mosquitoes such as Aedes vigilax or Culex annulirositrs). Australia has also had major outbreaks of dengue in the past but the only mosquito in Australia able to spread the viruses, Aedes aegypti, is restricted to far north QLD. It is unlikely to spread to southern cities beyond Brisbane based on temperature change alone but there is another mosquito that may pose a threat of dengue or chikungunya virus transmission in southern regions.

The Asian Tiger Mosquito (Aedes albopictus), poses a significant threat to Australia. It was discovered in the Torres Strait in 2005, having thought to have hitchhiked on fishing boats from Indonesia. Although the mosquito hasn’t yet managed to set up home on mainland Australia, its a more likely a question of when, not if, this mosquito will make its way here.

The container-inhabiting (not wetland living) mosquito has already hitchhiked to Europe and North America with eggs carried with people and their belongings. Movement of people, not shifts in climate is the biggest risk. Should it reach one of our major southern cities, there is little doubt that mosquito could become a persistent summer pest and possible public health threat. The way we respond to water shortages in our cities, by increasing water storage around our homes, may set the scene for this mozzie to move in.

Once the mosquito is established in our cities, all we need are travellers to bring in the viruses. Travellers introduce dengue virus into Far North QLD every year. Last year Japan experienced its biggest outbreak of dengue in over 70 years thanks to a traveller introducing the virus to local mosquitoes in downtown Tokyo. This Tokyo outbreak of dengue has implications for local authorities in Australia.

In my presentation at the Australian Entomological Society conference, I’ll highlight some of the issues to consider when assessing the risks posed by exotic mosquitoes in New South Wales as well as outline some of the problems local authorities may have to face when dealing with these mosquitoes that differ from the current focus of mosquito and mosquito-borne disease surveillance and control strategies.

You can view my presentation slides and abstract below:

Developing a strategic response to exotic mosquito threats in NSW

Cameron E Webb (1,2), Jay Nicolson (3), Andrew van den Hurk (4) & Stephen L Doggett (1)

(1)Department of Medical Entomology, Pathology West – ICPMR Westmead, Level 3, ICPMR, Westmead Hospital, Westmead NSW 2145 Australia; (2) Marie Bashir Institute of Infectious Disease and Biosecurity, University of Sydney, NSW 2006, Australia; (3) School of Pathology and Laboratory Medicine, The University of Western Australia, Nedlands, WA 6009, Australia; (4) Virology, Public and Environmental Health, Forensic and Scientific Services, Department of Health, Queensland Government, Brisbane, QLD 4108, Australia.

Mosquito-borne disease management in Australia faces challenges on many fronts. Home growth threats posed by endemic mosquito-borne pathogens (e.g. Ross River virus (RRV)) may increase with a changing climate but exotic mosquitoes and pathogens are an emerging threat. In the absence of a national strategy to address these exotic threats, local authorities must develop regionally specific surveillance and response programs to identify and respond to exotic mosquito incursion. The Asian tiger mosquito, Aedes albopictus, poses the greatest risk to temperate regions of Australia due to their close ecological associations with urban habitats and ability to transmit exotic pathogens (e.g. dengue viruses (DENV) and chikungunya virus (CHIKV)). The mosquito is widespread in local regions, has been detected at international ports and, given the increasing frequency of local travellers to regions where this mosquito is abundant, it raises the potential that an incursion into metropolitan Sydney in the coming years is probable. When this happens, what is the likelihood that this mosquito becomes established? Laboratory studies have confirmed Ae. albopictus could survive in the egg stage under climatic conditions typical of a Sydney winter. Despite the endemic mosquito, Aedes notoscriptus, sharing the same ecological niche to Ae. albopictus, cohabitation studies demonstrated that no interspecies competition would act to limit the local spread of Ae. albopictus and the mosquito could proliferating in the summer. Critically, vector competence experiments have demonstrated the ability of Ae. albopictus to transmit endemic pathogens and, given their propensity to bite humans, could contribute to human-mosquito-human outbreaks of RRV in urban areas of NSW, complementing the enzootic vectors that currently limit transmission to the metropolitan fringe. Local authorities need to develop a multiagency strategic approach to surveillance concomitant with strategic response to reduce the pest and public health threats associated with exotic mosquitoes.

Make sure you check out the tweets from the Australian Entomological Society Annual Conference in Cairns, QLD, 27 September through 1 October 2015, by clicking on #AusEntoSoc15

Should we mix mosquito repellents and sunscreens?

MosquitoRepellents_childarm_webbCombining mosquito repellents with sunscreens, as well as other cosmetics, sounds like a great idea but perhaps it isn’t to best way to protect ourselves from exposure to both the sun and mosquitoes.

There are formulations that combine mosquito repellents with various skin moisturizers but the most common combination formulations contain sunscreen and repellents. A combined formulation make sense given that Australia has one of the highest rates of skin cancer anywhere in the world. Even the Cancer Council have their own “Repel Sunscreen” formulations.

Combined formulations but conflicting risks

As well as questions regarding the efficacy of these formulations, there have also been some questions regarding their safety. Do they lessen the protection against the sun? Do they lessen the protection against mosquitoes? Do they increase the potential risk of toxic reactions to mosquito repellents?

One study found that the inclusion of mosquito repellent in sunscreen actually reduced the sun protection factor of the sunscreen. In 2009, I published a paper in Australian and New Zealand Journal of Public Health that investigated the efficacy of combined sunscreen and insect repellent formulations. The key finding was that no loss of protection from mosquito bites was provided by these combined formulations when compared to low and high dose “mosquito repellent only” formulations. The finding supported previous studies that indicated sunscreen does not reduce the efficacy of insect repellent. However, where we went further was to try and provide some guidelines for use of these products to maximise mosquito bite protection but also to minimise any potential adverse reactions to repellents.

I've provided plenty of deail of how to choose and use mosquito repellents in the "beating the bite" guidelines freely available for download

I’ve provided plenty of detail of how to choose and use mosquito repellents in the “Beating the Bite” guidelines freely available for download

This issue of conflicted use was highlighted in a review of sunscreen labelling recommendations and combination sunscreen/insect repellent products that outlined concerns that “the application of a combination product too frequently poses the risk of insect repellent toxicity, whereas application too infrequently invites photodamage”.

Could combined formulations raise potential over exposure to mosquito repellents?

It is important to note that many published studies and reviews have shown that DEET does not pose a significant health concern (see here too). A recent review of safety surveillance from extensive humans use reveals no association with severe adverse events. In short, if a DEET-based mosquito repellent is used as recommended, there are no major concerns for health risk.

What if the use of a combined repellent and sunscreen formulations results in the application rate of repellent above and beyond recommended rates?

How much repellent are you using with sunscreen?

The recommended use of sunscreens and repellents are quite different. As well as the frequency of reapplications (sunscreen every two hours; repellent reapplication is determined by the “strength” but may be up to four hours for mid-range formulations), the quantity used will vary. Mosquito repellents require a thin application over all exposed skin to provide effectiveness. When the applications rates providing effective protection in mosquito repellent studies are compared to those for sunscreen use (i.e. approximately 30ml applied across the forearms, legs, torso and back 20 minutes before going outside and reapplied every two hours), application rates for sunscreens are approximately 3-5 times greater.

Are you using repellent when you don’t need to?

It is interesting to note the differences in the use pattern of sunscreen and mosquito repellent use. In many instances, nuisance-biting mosquitoes will generally be more active during periods when sun exposure risk is low (e.g. late afternoon, evening and early morning). However, as I pointed out in this paper on mosquito repellent use to reduce the risk of dengue, protection against these day-biting mosquitoes could call for the use of both products simultaneously. There is also no doubt that under some circumstances in coastal regions of Australia, mosquitoes can be out and about biting in shaded environments (places like mangrove forests and coastal swamp forests) during the day.

The Yellow Fever Mosquito, Aedes aegypti (Photo: Stephen Doggett)

The Yellow Fever Mosquito, Aedes aegypti (Photo: Stephen Doggett)

What should you do?

I’m not aware of any review in Australia to reconsider the registration or recommendations surrounding the use of combined mosquito repellent and sunscreen formulations. In most instances, the advice provided by local authorities is simply to “follow label instructions”.

Combined mosquito repellent and sunscreen formulations are not recommended by the CDC. It is worth noting that also in Canada, combined sunscreen and insect repellents are not recommended. It is suggested to apply the sunscreen first, then the insect repellent over the top. The only problem is that as repellent will generally last longer than sunscreen, you end up alternating application of the two products.

We tested the idea that repellents should be applied first and then sunscreen over the top. While testing the efficacy of sunscreen wasn’t in the scope fo our study, we found that the efficacy of repellent (as measured by the duration of protection) was actually reduced. The reduction, we concluded, was probably due to physical disruption of the original mosquito repellent application during subsequent sunscreen application.

It should be noted once again that repeated reviews have concluded that DEET-based repellents pose a very low risk of adverse health impacts. However, if you were to take a cautious approach, if there is a risk of possible adverse reaction to repellents, this may be more likely to happen when using high dose DEET-based repellents (e.g. “tropical strength” repellents that may contain over 80% DEET) in combination with sunscreen. If you want to lower the risks as much as possible, using a low-dose DEET-based (e.g. containing less than 10% DEET), or picaridin-based, repellent will more closely align the recommended reapplication times of the two products.

If you’re looking for sunscreen advice, visit the Cancer Council website here.

The full reference for our 2009 paper is below:

Webb, C. E. and Russell, R. C. (2009) Insect repellents and sunscreen: implications for personal protection strategies against mosquito-borne disease. Australian and New Zealand Journal of Public Health, 33: 485–490.