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)

 

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

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

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

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

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

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

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

See the abstract below…

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

Cameron E Webb

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

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

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

David Lilly, Cameron E Webb and Stephen Doggett

Introduction: Research on field strains of Cimex lectularius from Australia has identified widespread resistance to pyrethroid insecticides, but variability in the magnitude expressed. To determine if differences in resistance mechanisms exist, collected strains were examined for the presence of metabolic detoxification and/or cuticle thickening. Methods: The presence and relative contribution of detoxifying esterases or cytochrome P450 monooxygenases were assessed. Bed bugs collected from Parramatta (NSW), Melbourne (VIC) – 2 strains, ‘N^o.2’ and ‘N^o.4’, and Alice Springs (NT) were exposed in topical bioassays employing deltamethrin and two pyrethroid synergists: piperonyl butoxide (PBO) and EN16/5-1. PBO inhibits both monooxygenases and esterases, whereas EN16/5-1 will inhibit esterases only. Thus in a comparative bioassay, the results can infer the dominant enzyme system. The Parramatta strain was then selected to study the potential presence of cuticle thickening. Nine-day-old male bed bugs were exposed to filter papers treated with the highest label rate of Demand Insecticide^®(200mL/10L of 25g/L lambda-cyhalothrin) and were grouped according to time-to-knockdown (< 2 hours, ≥ 4 hours, and survivors at 24 hours). Measurements of mean cuticle thickness at the transverse midpoint of the second leg tarsus were taken under electron microscope. Results/Conclusion: All strains possessed resistance that was inhibited by the synergists, with the Parramatta and Melbourne N^o.2 indicating esterase-dominance, and Alice Springs and Melbourne N^o.4 indicating cytochrome P450 monooxygenase-dominance. Cuticular measurements demonstrated that bed bugs surviving deltamethrin exposure had significantly thicker cuticles, denoting a novel form of resistance in these insects. doi: 10.1603/ICE.2016.92553

 

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

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

 

Taking Australian wetland research to China

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

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

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

Our abstract for the conference is below:

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

Jayne Hanford¹, Cameron Webb², Dieter Hochuli¹

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

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

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

You can keep an eye on whats happening in China by following Jayne on Twitter and checking the hashtag #IWC10

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

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

 

 

 

From publication to the public: Can blogging scientific papers stop people getting sick?

Why should academics blog? Answers to this question vary. On one hand it provides an opportunity to “spread to word” on newly published research. However, I’d argue that, more importantly, it is about getting the message out beyond the scientific community.

Do your research findings have something to offer the community?

I occupy a space somewhere between research and policy. While I undertake research, I’m also involved in disease surveillance, policy development and public health education. A critical component of my work (particularly in my role as a senior investigator with the Centre for Infectious Disease and Microbiology Public Health) is translating research for improved public health outcomes. Blogging helps me do this. Studies have suggested that this is why many other academic blog too. This also one reason why the use of social media by academics is encouraged.

I wanted the share an example of how blogging can increase the impact of your published research.

Much of the research I’ve done on mosquito repellents is prompted by questions I’m asked at public events and presentations. It is also informed by regular visits to the “insect repellent” shelves of the local supermarket. I believe public health messages need to keep place with the changing face of commercial formulations. This has led to work on botanical mosquito repellents (here and here and here), combined formulations of mosquito repellents and sunscreen and advice on using repellents in tropical areas where dengue is a risk. I’m also often pulling all this information together in one place.

One of the most common questions I’m asked is if mosquito repellent wrist bands/bracelets protect against mosquito bites. These products seem like a great idea and an alternative to topical repellents would be welcome by many.

Clearly there is demand for information as Google searches for “mosquito repellent wrist bands” are far and away the most common way new readers visit my blog. Of the top 20 search terms used to find my blog, 15 of the phrases contain “bands” or “bracelets”.

In 2009 I published a paper titled “Do wrist bands impregnated with botanical extracts assist in repelling mosquitoes?” in General and Applied Entomology. This is a very small journal published once per year by the NSW Entomological Society. The journal doesn’t have an impact factor and I suspect that many of the papers are only read by members of the society who receive a hard copy in the post. Once papers are 12 months old, they are made available on the website to download as PDF but I have no idea how frequently they’re accessed, particularly not by the general public.

Why did I published that work in General and Applied Entomology? Good question. At the time I probably didn’t appreciate how much interest would be in the work. The other issue is that I’d had some trouble getting “negative” results of mosquito repellent testing published. Also, as a member of the local society, I was keen to contribute and this was a relatively straight forward paper to write. Hindsight is wonderful though and clearly this could have gone elsewhere.

The results of this research could easily have been locked away in scientific literature obscurity forever. Fortunately, I started blogging.

I recently wrote about the publication in the post “Do mosquito repellent wrist bands work?“. This is now one of the most read posts on my blog with over 22,000 views of the article since late November 2013. Would I be excited if that many people read a paper of mine online at a Journal’s website? Of course. I get excited when over a 1,000 people read or download a paper!

Perhaps most importantly, the key message from that paper is freely available and easily accessed by those in search of information. There is also the backing of a peer-reviewed publication if people want to dig back a little deeper to find more information about the science behind the testing of these products. This isn’t the kind of information usually provided in fact sheets and websites of local health authorities.

The other benefit of have a blog is that it provides an easily accessible place to redirect people to who are asking questions via Twitter. I could always direct people to journal articles but often all they can access is the abstract. I’d prefer to send them to my blog.

Does this change people’s opinions? That is a more difficult question to answer but I would hope that with that many people accessing my article, the message is getting out there. I hope it is also spreading as much by word of mouth as well as via the world wide web. I’ve been contacted and quoted in a number of online and print publications so the post has also provided a stepping stone for contact with other media outlets.

This is just one example of how maintaining a blog and writing about published research can help improve public health awareness. Hopefully that blog post will stop a few people getting sick from mosquito bites in the coming years.

Why not join the conversation on Twitter and help share other examples of where blogging about scientific research has helped the community access public health information.

Should we mix mosquito repellents and sunscreens?

Combining 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 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)

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.

Want to learn more about the amazing world of Australian mosquitoes? Check out “A Field Guide to Mosquitoes of Australia” out now through CSIRO Publishing. Over 200 pages containing a pictorial guide to almost 100 different mosquitoes along with tips on beating their bite and protecting your family from the health risks of mosquitoes. You can order online or through your favourite local bookstore or online retailer.

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Read more at The Conversation: Are mosquito coils good or bad for our health?

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Read more at The Conversation: What can I eat to stop mosquitoes biting me?

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Read more at The Conversation: The best (and worst) ways to beat mosquito bites

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Can we genetically modify malaria mosquitoes to extinction?

Malaria no more? A new study has provided a pathway to possibly driving one of the most important malaria transmitting mosquitoes to extinction by using genetically modified mosquitoes that produce almost entirely male offspring. Without many females, the mosquito population will crash. A decline in the number of malaria cases should similarly follow.

There has been much research, as well as community discussion, regarding the use of genetically modified mosquitoes (and sometimes the pathogens themselves) to reduce the impacts of mosquito-borne disease. The recent proposals around the use of genetically modified mosquitoes to assist in the control of dengue outbreaks have been attracting many headlines, including both excitement and concern.

The new study, “A synthetic sex ratio distortion system for the control of the human malaria mosquito” (published in Nature Communications), reports on the genetic modification of mosquitoes that only produce sperm that result in (mostly) only male offspring. The researchers used a modified enzyme that attacks a specific region of the X-chromosome, preventing it being passed onto the next generation. Mating between GM mosquitoes and “wild type” mosquitoes produced up to 97.4% male mosquitoes.

In addition, the researchers demonstrated that once the wheels are set in motion, there is the potential that the spread of these  mosquitoes carrying “male only sperm” pass on the trait to their offspring and then their offspring. It is hoped that as these mosquitoes spread throughout the environment, eventually, the population of mosquitoes will crash as female mosquitoes are removed. The theory was tested in the laboratories and the researchers found that it took about 6 generations for the populations to crash (but they did need to start off with three times as many genetically modified mosquitoes to “wild type” mosquitoes).

While the technology is new, the idea was first proposed in the 1950s. The idea that you can distort the sex ratio of insect populations to control pest impacts had been proposed with various approaches to achieve it. The latest approach provides a novel way to apply the strategy to mosquitoes.

An illustration taken from “This is Ann, she’s dying to meet you” produced by US War Department, 1943

Doesn’t this latest research mean, in theory, you could make mosquitoes extinct?

The results from the current study are fascinating but it is still very early days before it is known if this approach works under field conditions and can actually reduce malaria, let alone drive mosquitoes to extinction. Keep in mind that this study focuses on just one of the thousands of mosquito species found throughout the world.

The mosquito the researchers from the Imperial College of London used was one of the key vectors of malaria parasites, Anopheles gambiae. This species belongs to a group of mosquitoes that contain up to 40 different species that may play a role in the transmission of malaria parasites. The fact that there are so many mosquito species capable of transmitting malaria parasites makes developing a “silver bullet” approach to control difficult.

Global distribution of potentially important malaria vectors (Taken from: Kiszewksi et al., 2004. American Journal of Tropical Medicine and Hygiene 70(5):486-498 via CDC)

There are many ecological and operational issues surrounding the release of genetically modified mosquitoes. Notwithstanding any fitness cost (e.g. less effective mating with “wild type” mosquitoes, lower fecundity, lower survival of immature stages, smaller dispersal ranges) that may put the genetically modified mosquitoes at a competitive disadvantage in the field, there are the issues of determining when, how many, and how frequently, genetically modified mosquitoes must be released into the environment. Some of these issues are discussed in this discussion paper and I’ve written about regulation here.

Even if the laboratory technique is translated to the field, and it worked, what would happen if you drove local populations of Anopheles gambiae to extinction?

I’m not sure that there is any research that identifies the ecological role of these mosquitoes. There certainly hasn’t been any work, to my knowledge, that addresses the issue in the same way we studied the ecological role of the Australian mosquitoes that spread Ross River virus. However, the potential ecological impacts of genetically modified mosquitoes have been identified.

Putting aside the issues of ecological impact (perhaps there wouldn’t be any significant ecological impact?), what would be the impact on human health? This is the critical issue. We know that by reducing the contact between mosquitoes and humans through the use of bed nets and insecticides can reduce the incidents of malaria, what if populations of Anopheles gambiae were significantly reduced or eradicated?

Malaria eradication campaigns have been with us for decades but are they now transitioning from spraying insecticides to releases genetically modified mosquitoes? (Source: National Library of Medicine)

One of the problems may be that the ecological niche exploited by Anopheles gambiae is simply taken up by another of the mosquitoes able to transmit malaria. Anopheles gambiae is a pretty good competitor and if you take it out of the environment, another Anopheles species may move in. There is no doubt that Anopheles gambiae is one of the most important vectors of malaria parasites but even if a “replacement” species moves in, outbreaks of disease may still be less than before. However, health authorities will still need to call on traditional mosquito control and malaria prevention strategies. A balance is required when assessing the cost effectiveness of the new and old strategies.

Amongst the wave of new technologies purported to aid in the battle against malaria, it is worth noting that current methods of prevention (e.g. bed nets) and control (e.g. insecticides), in combination with better diagnosis and treatment, have contributed to a reduction in world wide malaria mortality rates by 42% since 2000. Combining different mixes of approaches (e.g. bed nets and residual insecticide treatments) has been shown to be potentially significant. In the future, perhaps genetically modified mosquitoes should be added to this mix too.

You can listen (stream or download) to me chat with James Carleton about the implications of the research on Radio National’s Breakfast. There has also been plenty of news coverage following the publication of the research, a good overview is here.

Why not join the conversation by following me on Twitter?

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The photo of the malaria vector, Anopheles gambiae, at the top of this post is taken from here (CDC/James Gathany)

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What do you need to know about West Nile virus?

With the arrival of mosquito season in North America, health authorities have started issuing warnings about prevention of potentially fatal West Nile virus. My latest coauthored publication reviews the epidemiological and clinical aspects of this mosquito-borne pathogen.

West Nile virus is a pathogen generally spread by mosquitoes from birds to humans. While only about one in five people infected develop symptoms (inc fever, headache, body aches, nausea, vomiting, swollen lymph glands or a skin rash.), for those over 50, there can be more serious implications and the illness may be fatal. There is currently no vaccine, avoiding mosquito bites is the only way to prevent disease.

The virus was first detected in North America in 1999 and has since spread from coast to coast, having a significant impact on the health of both people (resulting in an economic burden of around $56 million per year) and wildlife (particularly birds). Interestingly, from 2007 there was a steady decline in the activity of the virus and many thought that major outbreaks would be a thing of the past but 2012 saw a one of the largest outbreaks in almost a decade. During this time, Texas was particularly hard hit with 1,868 cases and estimated costs of around US$47.6 million.

The activity of the virus in 2013 wasn’t insignificant either.

Annual total numbers of West Nile virus disease cases and deaths reported by CDC 1999-2013.

It hasn’t only been North America that has been impacted by West Nile virus. Outbreaks of human and animal illness have also been reported in Europe. In fact, cases of West Nile virus were reported from France in the 1960s. However, there wasn’t a major outbreak until 1996-1997; prompting warnings from health authorities about the future risks associated with this pathogen in Europe. The activity of the virus in North American, Europe and Africa provides interesting opportunities to research the genetic differences between regions and potential implications for surveillance and disease control. Europe has developed an extensive surveillance program to assess activity of endemic and exotic mosquitoes and activity of the virus.

Human illness in Europe resulting from West Nile virus infection during 2012 (European Centre for Disease Prevention and Control)

It is interesting to note that one of the key factors linking outbreaks of West Nile virus in both North America and Europe is the presence of closely related mosquitoes. Unlike dengue, chikungunya or yellow fever viruses that are spread by Aedes mosquitoes, and malaria parasites by Anopheles mosquitoes, West Nile virus is primarily spread by Culex mosquitoes. In particular, the bird-feeding mosquitoes within the Culex pipiens group.

The Culex pipiens group, particularly Culex pipiens, Culex quinquefasciatus and Culex molestus, are closely associated with urban environments. With mosquitoes found in close contact with humans, there is greater risk associated with potential outbreaks.

Our recent review article in the International Journal of General Medicine provides an overview of the clinical and epidemiological aspects of West Nile virus and is a good starting point for anyone interested in this pathogen and the factors that drive outbreaks in North America and Europe.

The abstract of our paper is here:

The reurgence of West Nile virus (WNV) in North America and Europe in recent years has raised the concerns of local authorities and highlighted that mosquito-borne disease is not restricted to tropical regions of the world. WNV is maintained in enzootic cycles involving, primarily, Culex spp. mosquitoes and avian hosts, with epizootic spread to mammals, including horses and humans. Human infection results in symptomatic illness in approximately one-fifth of cases and neuroinvasive disease in less than 1% of infected persons. The most consistently recognized risk factor for neuroinvasive disease is older age, although diabetes mellitus, alcohol excess, and a history of cancer may also increase risk. Despite the increasing public health concern, the current WNV treatments are inadequate. Current evidence supporting the use of ribavirin, interferon α, and WNV-specific immunoglobulin are reviewed. Nucleic acid detection has been an important diagnostic development, which is particularly important for the protection of the donated blood supply. While effective WNV vaccines are widely available for horses, no human vaccine has been registered. Uncertainty surrounds the magnitude of future risk posed by WNV, and predictive models are limited by the heterogeneity of environmental, vector, and host factors, even in neighboring regions. However, recent history has demonstrated that for regions where suitable mosquito vectors and reservoir hosts are present, there will be a risk of major epidemics. Given the potential for these outbreaks to include severe neuroinvasive disease, strategies should be implemented to monitor for, and respond to, outbreak risk. While broadscale mosquito control programs will assist in reducing the abundance of mosquito populations and subsequently reduce the risks of disease, for many individuals, the use of topical insect repellents and other personal protective strategies will remain the first line of defense against infection.

The full paper can be downloaded for free here.

You can also read more background to West Nile virus and the 2012 outbreak in my piece for The Conversation. For a comprehensive look at how the pathogen is managed in North America, download the CDC publication “West Nile Virus in the United States: Guidelines for Surveillance, Prevention, and Control“.

Why not join the conversation on Twitter by following me at @mozziebites?

The image at the top of this piece is taken from Mother Jones.

A manual for managing urban wetlands

The protection and rehabilitation of urban wetlands is critical. They are under threat from urbanisation and a changing climate climate but perhaps the greatest risk is disengagement from the community with many not really know the true value of our wetlands.

I have had a long and productive working relationship with the Sydney Olympic Park Authority (SOPA). One of the most enjoyable activities has been serving as a member of the Wetlands Education and Training (WET) Program Advisory Panel. A small group of wetland scientists assist SOPA develop and coordinate workshops for scientists, managers, policy makers and teachers. The program has been in place since 2002 and over 30 workshops have been held since then. There have two very successful “managing mosquitoes” workshops in recent years with the next scheduled for 2015 (keep your eyes out for that one)

After ten years of working with a diverse range of professionals, it was decided that the collected wisdom of those groups and individuals should be brought together in the form of a resource for those managing urban wetlands. In particular, it would draw on many of the experiences within the wetland of Sydney Olympic Park.

The “WET eBook: Workbook for Managing Urban Wetlands in Australia” was launched on Thursday 28 November 2013 in conjunction with a two-day workshop on constructed wetlands management. The eBook was officially launched by Michael Knight, Chair of the Sydney Olympic Park Authority. Michael is well connected to the Sydney Olympics, serving as Minister for the Olympics between 1995 and 2001 in NSW, and it could be argued that, without the hosting of the 200 Olympics, many of the current wetlands around the area may not exist today.

I’ve contributed three chapters to the eBook. They can be downloaded individually but don’t just stick to the mozzies, there is lots more valuable information contained within the 400 or so pages. A wide range of topics, across broad topic areas of estuarine wetlands, freshwater wetlands, monitoring, developing a plan of management, are covered and a concluding section brings everything together. In fact, I was given the opportunity to be lead author on the final chapter, identifying and bringing together many of the challenges faced by urban wetlands and mapping out a way forward for wetland conservation.

My chapters and direct links to the individual PDFs are below.

Webb C.E. (2013) Managing mosquitoes in constructed freshwater wetlands. ‘Workbook for managing urban wetlands in Australia’ (Ed. S. Paul) 1st edn. (Sydney Olympic Park Authority) ISBN 978-0-9874020-0-4

Webb C.E. (2013) Managing mosquitoes in coastal wetlands. ‘Workbook for managing urban wetlands in Australia’ (Ed. S. Paul) 1st edn. (Sydney Olympic Park Authority) ISBN 978-0-9874020-0-4

Webb C.E. et al. (2013) Facing the challenges of managing urban wetlands in Australia: the way forward. ‘Workbook for managing urban wetlands in Australia’ (Ed. S. Paul) 1st edn. (Sydney Olympic Park Authority) ISBN 978-0-9874020-0-4

Do mosquito repellent wrist bands work?

If you don’t know if commercial mosquito repellents work, how can authorities provide useful advice to the community? What about non-topical mosquito repellents? How do you help the community make informed decisions on how to choose and use mosquito repellents effectively?

I’ve written about mosquito repellents on a number of occasions. The most popular post on my blog has been one describing how we test new repellents. That post was promoted by the enormous support received by a crowdfunding campaign by the developers of the Kite “mosquito repellent” patch that raised over $550,000 back in August 2013. There is a steady stream of new repellents in the news, either newly published research on active ingredients or new approaches to formulations and delivery systems. What was most appealing with the Kite patch was that is wasn’t a topical formulation but a “spatial repellent”. All you needed to do was put a sticker on your shirt you’d be protected from biting mosquitoes. An effective non-topical mosquito repellent would be a great asset in our battle against mosquito-borne disease.

Much of the research I do with mosquito repellents is directed towards better informing local health authorities on what works and how it should be used. My development of guidelines on mosquito repellent use came from the paucity of information provided by local health authorities. Health authorities generally provide the right advice, just not with enough detail that allows the public to make informed choices on mosquito repellents and how they should be used.

Topical mosquito repellents are the most commonly used and widely distributed in Australia. These products, particularly those containing DEET or picaridin are most commonly recommended by health authorities

One of the most common questions I’m asked at public events is “do those mosquito repellent wrist bands and patches work?”

In 2010, I tested a product currently registered for use in Australia by the APVMA for use against mosquitoes. This was a plastic wrist band impregnated with peppermint oil. The results of the study were published in the 2011 volume of General and Applied Entomology. All papers in that volume are now freely available for download.

We tested the bands in laboratory conditions against the mosquito Aedes aegypti. This mosquito is one of the major vectors of dengue and yellow fever viruses internationally. It is also the most common species used in laboratory assessments of mosquito repellents due to its persistent biting behaviour and preference for humans.

The bands were tested to determine if any protection or repellency was provided against the mosquitoes compared to a DEET-based topical repellent. Although fewer mosquitoes landed on arms with the wrist bands compared to arms without wrist bands, there was no complete protection provided (as observed with DEET-based topical repellents). In fact, even on arms with wrist bands, beyond a small area around the band, the reduction in landing mosquitoes further up the arm was only marginally better than on arms without the wrist bands.

In short, while there was a reduction in total bites in close proximity to the bands, the bands we tested won’t prevent all bites. They won’t completely prevent bites on the arms wearing the bands and there is certainly no evidence that other parts of the body will be protected. They won’t create a “halo” of protection against mosquito bites around you.

There aren’t a lot of published studies investigating these “non-topical” repellents. There are a few “wrist band” and “patch” type devices available but all generally contain a botanical based active ingredient. In Australia, there are no DEET-based spatial repellents registered (to my knowledge). Studies from overseas have yielded mixed results. The level of protection (if any) provided is generally dose-related. For the most part, these devices have been demonstrated to assist in reducing the number of bites but not protecting you from all bites. Similarly, studies investigating the effectiveness of burning “mosquito sticks” demonstrate that while fewer bites are received, there is no complete protection provided.

A summer approaches, the local hardware stores boost their stocks of Christmas lights and mosquito repellents

The results prompt an interesting question for health authorities (as well as regulators of mosquito repellents). Is it good enough to simply reduce the number bites, do you really need to prevent all bites?

My personal feeling is that you need to prevent as many as possible. Transmission of mosquito-borne pathogens such as Ross River virus, dengue virus or West Nile virus isn’t dependent on the number of bites. A single mosquito bite is all it takes. It may be true that the more bites you receive, the more likely it is that one of those mozzies will be infected but what if it is the first bite of the day that infects you?

So, do these devices have any use? My advice is to go with a DEET-based topical repellent. However, in some cases there may be some benefit in using a repellent wrist band to protect the hands if you’re undertaking an activity where the topical application of repellent may be considered inappropriate (perhaps fishing?). You could even wear these devices around your ankles to prevent bites but if you’re in a region where dengue or Chikungunya viruses are active (see here and here), I’d always recommend a topical product.

So, in answer to that commonly asked question, “Do mosquito repellent wrist bands work?”, I’d say they may offer some very limited protection but they are an ineffective way to prevent mosquito bites compared to a DEET or picaridin based topical repellent.

Here is the abstract of our paper:

A wide range of insect repellent formulations, as well as active ingredients, are currently registered for use in Australia. While topical repellents are most common, there are also commercial products in the form of wristbands impregnated with botanical extracts that purport to repel mosquitoes. In laboratory tests, wristbands impregnated with peppermint oil were tested against the mosquito Aedes aegypti to determine their efficacy in repelling mosquitoes from the forearms of human volunteers compared with a commercial DEET-based topical repellent. The wristbands failed to stop landing by the mosquitoes, although the mean landing rate of mosquitoes was significantly lower on forearms in the presence of the wristband compared with untreated controls. The mean landing rate of mosquitoes on forearms treated with DEET was significantly lower than those of forearms in the presences of the wristband. The results indicated that while wristbands impregnated with botanical products may assist in repelling mosquitoes, their inability to completely protect individuals from mosquito bites suggests that they should not be recommended for use in areas of endemic or epidemic mosquito-borne disease.

The full paper [PDF] can be downloaded for free here:

Webb CE and Russell RC. (2011) Do wrist bands impregnated with botanical extracts assist in repelling mosquitoes? General and Applied Entomology 40:1-5. PDF

[UPDATE 25 February 2015] It is interesting to note that in the U.S., the Federal Trade Commission has charged a manufacturer of mosquito repellent wrist bands with “making deceptive, unsubstantiated claims” regarding the effectiveness of their product. It will be interesting to see how this decision impacts the availability of these products in North America.

Want to learn more about the amazing world of Australian mosquitoes? Check out “A Field Guide to Mosquitoes of Australia” out now through CSIRO Publishing. Over 200 pages containing a pictorial guide to almost 100 different mosquitoes along with tips on beating their bite and protecting your family from the health risks of mosquitoes. You can order online or through your favourite local bookstore or online retailer.

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Read more at The Conversation: Are mosquito coils good or bad for our health?

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Read more at The Conversation: What can I eat to stop mosquitoes biting me?

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Read more at The Conversation: The best (and worst) ways to beat mosquito bites

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What do bats eat more often, mosquitoes or moths?

Have you ever thought about how hard it is to find pieces of munched mosquito in a pellet of bat poo?

Perhaps not but for many years I have. Luckily, I have been part of a wonderful research project that has overcome the difficulties of studying the diet of insectivorous vertebrates.

I’ve already written about the multidisciplinary research project, funded by a research grant from the NSW Environmental Trust, designed to determine the importance of saltmarsh mosquitoes (Aedes vigilax) to local bat populations on the Central Coast of NSW.  The hard work in this project was done by Dr Leroy Gonsalves but the 4 year project also included researchers from the Australian Catholic University, University of Sydney and Forest Science Centre (NSW Department of Primary Industries).

Our most recent publication, titled “Mosquito Consumption by Insectivorous Bats: Does Size Matter?“, is the fourth paper to be produced from this study. We’ve probably left the best until last as this research has really opened some doors to our understanding of mosquitoes and their importance in the diet of Australian bats in coastal environments.

There had already been some qualitative studies that hinted at the possibility that saltmarsh mosquitoes were an important prey source for insectivorous bats. Studies have shown that the “feeding buzzes” (the sounds bats make when they’re hunting food) had been recorded over saltmarsh habitats. The conclusion was made that these bats were most likely feeding on mosquitoes. Some of our studies have indicated that the abundance of mosquitoes can influence the use of foraging habitats of bats. As with previous studies, this conclusion was made by recording the “feeding buzzes” of bats or radio-tracking bats while also sampling the abundance of mosquito and moth populations.

What was missing was a quantitative assessment of mosquito consumption by bats. How many mosquitoes are eaten by bats? How many bats species were eating mosquitoes? How important are mosquitoes, compared to other insects, such as moths, to the diet of bats?

This was the critical question. It was also a little tricky trying to work out how to get an answer. While the circumstantial evidence appeared to be strong, we needed actual evidence that bats were eating mosquitoes.

What did we do?

There are a few different ways you can determine what bats are eating. The classic approach is through visual examination of fecal material. That basically means searching through bat shit under the microscope looking for bits of insect and then identifying it. This technique has been used successfully. However, it only took us 15 minutes of looking through bat shit to realise this wasn’t going to cut it. We could clearly identify pieces of insect but what were they? We never found a piece of “entomological material” in the samples that was definitively from a mosquito. We needed another approach.

Since we know there was insect material in the feces, perhaps we could use molecular methods to identify them? Instead of looking for bits and pieces of chewed up mosquito, why not look for mosquito DNA?

Fecal samples were taken from five eastern Australian bat species; Vespadelus vulturnus (little forest bat), Vespadelus pumilus (eastern forest bat), Miniopterus australis (little bent-wing bat), Nyctophilus gouldi (Gould’s long-eared bat) and Chalinolobus gouldii (Gould’s wattled bat). These bats are relatively common in coastal regions of NSW and range in size from 4-14 g. Yes, these bats are small!

How did we collect the bat feces? Bats were collected using harp traps set in forest habitats adjacent to the estuarine wetlands. Bats that were trapped were then transferred to small bags. Bats were kept in the bag for at least 1 hour and then released. Fecal pellets were then collected from the bottom of the bag and returned to the laboratory for testing.

Five sub-samples from each individual bat were tested for the presence of mosquito and moth DNA using molecular techniques. We even conducted some quality control experiments and found that our molecular techniques could identify mosquitoes, even if they comprised around 5% of the total contents of the fecal pellet. We were confident that if a sample was negative, it was highly unlikely that moth or mosquito material was contained within the fecal pellet.

Leroy Gonsalves removing a little forest bat from the harp trap. All set to collect some bat poo! (Photo by Doug Beckers)

What did we find?

Across the five bat species collected, fecal samples were collected from 52 individual bats. From the samples, a total of 40 prey taxa was identified from the bat feces. Moths were the most frequently detected prey, present in the feces of 49 of the 52 (approx 94%) bats tested individuals. We were expecting this, moths are probably a pretty tasty treat for a bat.

Interestingly, mosquitoes were only detected in the feces of two bat species (Vespadelus pumilus and Vespadelus vulturnus). Of those bats, mosquitoes were collected from 2 of 10 Vespadelus pumilus individuals and 11 of 20 Vespadelus vulturnus individuals. All the individuals had eaten moths.

With regard to mosquitoes, only 2 of the 5 bat species tested had been eating mosquitoes and of those two species 20-55% had recently consumed mosquitoes. By comparison, all individuals of these two species tested had been eating moths.

Little Forest Bat (Vespadelus vulturnus) (Photo: Museum Victoria)

What does this mean?

Most importantly, it highlights the dangers of generalisation when it comes to bat biology. We’ve clearly demonstrated in this study that there will be species-specific relationship between bats and preference for foraging on mosquitoes. This relationship is most likely driven by the size of the bat. Based on our work, the small bat species are more likely to feed on mosquitoes.

This makes sense as other studies have shown that when it comes to insectivorous vertebrates, larger predators tend to eat larger prey, rather then greater numbers of smaller prey.

With regard to bat conservation, the results of our study haven’t identified a bat species that relies heavily on mosquitoes. However, in regions where smaller bat species are threatened or endangered, consideration should be given to the possibility that if mosquitoes are locally abundant, they may provide a relatively more important food source for these species. Local authorities should be mindful of this potential when designing broad-scale mosquito control programs. Perhaps they should be doing more to encourage moth populations?

If they’re good enough for bats, perhaps moths are good enough for us? Canberra’s Ironbark Cafe cooks up “Brandy Flamed Bogong Moth Frittata”. (News Limited)

It has been exciting working on this aspect of the project. It has been great to see Leroy develop this innovative use of molecular techniques to investigate bat diet (as well as helping understand the ecological role of mosquitoes). Many ecologists are heading in this direction and it will be interesting to see how new technologies open up new opportunities. When we started this project, this approach hadn’t been used extensively, and certainly not to determine weather bats were eating mosquitoes.  This technique has now been used widely, including to determine if bats are eating agricultural insect pests and can be used to track bats and their response to seasonal fluctuations of these pest insects. It has also been used to investigate the diet of snakes.

The full citation our the paper is:

Gonsalves L, Bicknell B, Law B, Webb C, Monamy V (2013) Mosquito Consumption by Insectivorous Bats: Does Size Matter? PLoS ONE 8(10): e77183. doi:10.1371/journal.pone.0077183

The abstract is below:

Insectivorous bats have often been touted as biological control for mosquito populations. However, mosquitoes generally represent only a small proportion of bat diet. Given the small size of mosquitoes, restrictions imposed on prey detectability by low frequency echolocation, and variable field metabolic rates (FMR), mosquitoes may not be available to or profitable for all bats. This study investigated whether consumption of mosquitoes was influenced by bat size, which is negatively correlated with echolocation frequency but positively correlated with bat FMR. To assess this, we investigated diets of five eastern Australian bat species (Vespadelus vulturnus Thomas, V. pumilus Gray, Miniopterus australis Tomes, Nyctophilus gouldi Tomes and Chalinolobus gouldii Gray) ranging in size from 4-14 g in coastal forest, using molecular analysis of fecal DNA. Abundances of potential mosquito and non-mosquito prey were concurrently measured to provide data on relative prey abundance. Aedes vigilax was locally the most abundant mosquito species, while Lepidoptera the most abundant insect order. A diverse range of prey was detected in bat feces, although members of Lepidoptera dominated, reflecting relative abundance at trap sites. Consumption of mosquitoes was restricted to V. vulturnus and V. pumilus, two smaller sized bats (4 and 4.5 g). Although mosquitoes were not commonly detected in feces of V. pumilus, they were present in feces of 55 % of V. vulturnus individuals. To meet nightly FMR requirements, Vespadelus spp. would need to consume ~600-660 mosquitoes on a mosquito-only diet, or ~160-180 similar sized moths on a moth-only diet. Lower relative profitability of mosquitoes may provide an explanation for the low level of mosquito consumption among these bats and the absence of mosquitoes in feces of larger bats. Smaller sized bats, especially V. vulturnus, are likely to be those most sensitive to reductions in mosquito abundance and should be monitored during mosquito control activities