How far do mosquitoes fly?

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

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

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

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

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

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

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

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

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

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

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

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

The abstract is below:

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

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

 

 

 

Entomology 2014: Portland, Oregon

Portland isn’t going to get any less “weird” when 3000 entomologists hit town! I’m going to be one of them there talking tweets and tweaking public health messages.

This month I’m heading along to the Entomology 2014: The Annual Meeting of the Entomological Society of America, 16-19 November in Portland, Oregon.

This will be the first time I’ve attended an ESA meeting and I’m really looking forward to it. These are large meetings with thousands of delegates, a big change from our recent Mosquito Control Association of Australia conference that attracted about 150 attendees! There is little doubt that I’ll be kept busy getting along to just a fraction of presentations I’m interested in. You can check the program yourself here.

A couple of interesting things I’m looking forward to (notwithstanding the coffee, record shopping and doughnuts) is the workshop on scientific writing, How not to write like a scientist, and a session on the role (or perhaps lack of a role) arthropods play in Ebola virus transmission. I’ve written about why mosquitoes don’t spread Ebola here.

I’ll be giving a couple of presentations, one on the role of mosquito repellents in managing mosquito-borne disease risk and another on the use of social media to promote public health messages. Both of these invited presentations are sure to be fun. It will be nice to catch up with some old friends during the repellent symposium. I recently contributed a book chapter to the new handbook on insect repellents edited by the session organizer/moderator Mustapha Debboun (alongside Dan Strickman and Steve Francis).  the symposium.The social media session will be fun too and, apart from sharing my experiences in using social media to promote public health messages, it will be great to catch up with many wonderful people who’ve made my experience on Twitter in recent years so rewarding.

My PhD student, David Lilly, will also be speaking on his work studying insecticide resistance in bed bugs. The abstracts for all these presentations are below but please note that due to the nature of some symposium, not abstracts are included on the Entomology 2014 online program.

A researcher at Rockefeller University feeds her stock of yellow fever mosquitoes (Aedes aegypti). This approach remains one of the most effective ways to test new mosquito repellents. (Photo: Alex Wild)

1. Finding a place for mosquito repellents in mosquito-borne disease management: An Australian perspective

Webb CE

Mosquito-borne disease is a growing concern for local authorities in Australia. While broad scale mosquito control programs reduce nuisance-biting impacts in some instances, in most regions where mosquito-borne pathogens, particularly Ross River virus, pose a public health risk, local authorities rely on the promotion of personal protection measures. A key component of such strategies is the use of topical insect repellents. There is little evidence that confirms their effectiveness in preventing disease. However, many studies have indicated that the correct use of topical repellents can protect against biting mosquitoes. As a result, it is likely that the promotion of topical insect repellents will remain a critical component of personal protection measures. If they’re here to stay, health authorities must ensure the public is aware of how to effectively choose and use repellents. Currently, there is a disjointed approach to repellent advice provided by state and local authorities. What is needed is a national approach that sets the framework for

The Challenges and Significant Contributions of Insect Repellents to Vector Control

Sunday, November 16, 2014: 8:00 AM-12:00 PM
B115-116 (Oregon Convention Center)

---

 

The global resurgence in bed bugs has been attributed to increased international travel and a shift in household insecticide use but perhaps it is resistance that is driving the increasing pest impacts? (Photo: Steve Doggett)

2. The importance of methodology and strain selection when determining efficacy of insecticides against bed bugs

Lilly D, Webb CE and Doggett SL

Selection of an appropriate bioassay technique and insect strain(s) are known to be important factors when attempting to accurately detect and monitor for insecticide resistance or define the efficacy of an insecticide. Recent studies with both susceptible and resistant strains of the common bed bug, Cimex lectularius, have indicated these principles similarly apply to bed bugs and must be considered prior to undertaking diagnostic bioassays. Age, access to a blood meal, and the period since repletion may all influence the outcomes of bioassays with bed bugs. Dry residual deposits of insecticides, in particular those of neonicotinoids, also have the potential to overestimate resistance ratios or provide a false negative indication of efficacy when viewed in comparison to more applicable topical or wet residual exposure methods. Resistance monitoring of Australian field strains has also revealed that a wide spectrum in the magnitude of resistance can exist between strains that express identical resistance mechanisms, and that laboratory strains held in culture for long periods of time may lose resistance or change resistant genotypic frequencies. When factored in to the proliferation of field strains with various combinations of multiple and/or cross resistance mechanisms, this clearly presents a challenge to product manufacturers, registration bodies, and pest managers as to how they can ensure the experimental methodology and strain selected is most appropriate for the desired purpose or outcome. The results of laboratory investigations to provide informed guidance on recommended ‘best practise’ bioassays with bed bugs will be presented.

Graduate Student Ten-Minute Paper Competition: MUVE

Monday, November 17, 2014: 9:48 AM
B117-119 (Oregon Convention Center)

---

 

Engaging with the community is an important part of public health and beyond public meetings and workshops, social media may provided an effective way to get the messages out to increase awareness of mosquito-borne disease (Photo: Steve Doggett)

3. Can social media extend the reach of public health messages?

Webb CE

Increasing the exposure of public health messages is critical. This is particularly the case for mosquito-borne disease where advice on personal protection measures often informs the first line of defense against biting mosquitoes. Traditional media has been the mainstay of communication efforts by local authorities but could the use of social media provide a new vehicle for disseminating information and engaging with the wider community? The aims of this study were to determine if promotion and engagement via social media influenced how online information is accessed. A range of social media platforms, particularly Twitter, were employed to disseminate public health messages and engage the community and traditional media outlets. The total weekly exposure of “tweets” was measured for six months with approximately 40,000 people per week received tweets with maximum exposure of almost 190,000 people in a single week. 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.

Reaching Beyond Our Horizon: Social Media & Connecting with the World

Wednesday, November 19, 2014: 8:00 AM-12:00 PM

Portland Ballroom 252 (Oregon Convention Center)

---

If you’re attending the meeting, please say hi if you’re passing by and feel free to introduce yourself using your twitter handle! If you’re not at the meeting, you can keep track by following the hashtag #EntSoc14. I’ll be trying to tweet about bits and pieces during the conference so please join the conversation!

The image at the top of this post taken from “Top ten things you didn’t know about Portland”