Video lecture: Urban planning and mosquito-borne disease

Can urban planning influence mosquito-borne disease risk in Australia from Cam Webb on Vimeo.

The video above was originally broadcast to the The International Society for Neglected Tropical Diseases meeting at the Natural History Museum, London, 17 October 2012. You can read some background to the meeting here.

Abstract: Mosquito-borne disease management in coastal Australia faces many challenges. Increasing urbanisation is bringing the community closer to productive mosquito habitats but environmental management of coastal wetlands is often in conflict with effective mosquito control strategies. Broadscale mosquito control activities are restricted, resulting in annually abundant pest and vector mosquito populations, and large scale estuarine wetland rehabilitation projects are increasing the availability of productive mosquito habitat. Balancing the desire for environmental conservation with the need to protect the health of human communities requires integrated urban design strategies combined with targeted research. Local authorities are looking to use planning instruments to minimize the impacts of local mosquitoes, such as the incorporation of buffer zones between residential allotments and mosquito habitats as well as design, construction and maintenance requirements of constructed wetlands.

Mozzie bites and tweet tracking

One of my favourite artists, Nat Russell, painted a wonderful portrait of me a couple of years ago. Perhaps think of this as me wading out into the sea of social media?

Could social media help beat the bite of mosquito-borne disease?

Social media won’t do it alone but I think it is definitely something Australian authorities should embrace. The only problem is, how do you measure the success of social media activity? Taking my activity on Twitter as a case study, I monitored the changes in follower number, “tweet type” and estimated reach and exposure of tweets over a six month period. This was during a time when I would normally be active in the media responding to  mosquito-borne disease outbreaks or general interest questions about mosquito biology.

As broad scale mosquito control programs are generally limited, Australian health authorities typically rely on the communication of personal protection strategies to reduce mosquito-borne disease risks. These personal protection strategies may include avoiding known mosquito habitats, wearing long sleeved shirts and long pants to create physical barriers to biting mosquitoes and the use of insect repellents. Messages are usually relayed to the public via media releases or online fact sheets.

I started using Twitter in September 2010 with the expectation that I could use the service to distribute those public health messages as well as news on mosquito and mosquito-borne disease research. I generally tweet material that is related to my position with NSW Health/Westmead Hospital/University of Sydney but my account is not an official source of information from those organisations. I generally keep “personal” tweets to a minimum.

I’d already had some experience with public health communications working groups. I consider my activity on Twitter to be an extension of that work. In particular, my work with the “Living with Mosquitoes” group in the Hunter region investigated new ways to raise awareness of mosquito-borne disease risk and communicate more effectively the benefits of personal protection strategies. A couple of the options we tried were the incorporation of “mosquito risk periods” into free tide charts and stickers designed for primary school students. We even briefly (unsuccessfully) experimented with using myspace to host some information.

Using Twitter to spread the message

How did I go about using Twitter to help spread the word on mosquito-borne disease? At first I was expecting to build a following directly with the public by growing the number of followers. What I’ve found, however, is that the greatest benefit of Twitter has been when it is used in association with traditional media activities. Tweets can be exchanged between myself and the presenter/broadcaster/publisher, particularly links to online resources/fact sheets, and then subsequently retweeted to their followers.

You can read more background about my use of Twitter for spreading mosquito-borne disease awareness in this article, “Can the buzz of mosquitoes be replaced with a tweet?”, recently published in “Mosquito Bites” – the newsletter of the Mosquito Control Association of Australia.

While I initially thought a large number of followers was important, I now realise that engagement with the media (as well as other active users of Twitter) may be the best way to enhance the way health messages can be promoted. It is our local media that play the primary role in disseminating public health information to the local community, perhaps Twitter is best used to build communication lines between journalists, scientists and local authorities?

Assessing activity on Twitter

I started to think of ways I could better assess my use of Twitter to help answer some of these questions. I first starting thinking about this after reading a great paper by Thackery et al. in 2012 titled “”Adoption and use of social media among public health departments”. The paper describes the social media activity of health departments and highlights that very few use social media to engage the community. Their use of social media is, as is the case for traditional media, a one-way direction of information. There is very little active engagement. The authors argue that the departments need to develop a strategic communication plan to expand their reach while fostering interactivity and engagement.

This is very much the case in Australia too. If you have a quick look at state health department Twitter accounts (e.g. NSW Health, QLD Health), there is very little (if any) engagement with other Twitter accounts (i.e. very few RTs or Replies).

Before the start of the 2012-2013 “mosquito season”, I decided to try and document some of my activity on Twitter using some free online analytics services. I am the first to admit, this was a pretty rough and ready way to collect data. It was really just an experiment to see what kind of data could be collected to document how my activity on Twitter changed over the course of the season.

Most of the information was collected weekly from TweetReach. This website collects data on your account including estimated reach (total number of unique accounts that receive tweets) and exposure (total number of times tweets are received by any account) as well as a breakdown of “tweet type” (e.g. tweets, retweets and replies). It samples the last 50 of your tweets to collect this data. I logged in every Saturday morning and downloaded the data. I tweet more than 50 times a week (on average over this period I tweeted about 70 times per week) so the data represented what was going on towards the end of each week. I started in early November 2012 and stopped at the end of April 2013.

So, what did the analysis of my Twitter activity reveal?

Firstly, did my followers change over this time? There was a steady increase in the number of my followers as shown in the chart below. Followers increased from 916 to 1406 over the six month period. I’m not exactly sure what this reveals but since there were no notable falls in the number of followers, perhaps it suggests that most followers find the tweets of interest (or at least not annoying enough to “unfollow”).

A chart showing the weekly growth in the number of followers from November 2012 through April 2013

Secondly, what did analysis of my “tweet types” show? There is generally a three way split in my activity between tweets, RT and replies. The trend remained fairly consistent over the six month period as shown in the chart below. Many of the RTs were tweets from various health authorities providing information on mosquito-borne disease outbreaks or other health related matter (e.g. infectious disease outbreaks, vaccination information, general health advice). It was generally a quiet season for mosquito-borne disease activity. The start of the season was marked by local activity of dengue in FNQ and the end of the season by activity of Ross River virus and Barmah Forest virus in SE QLD as well as SW WA. As a result, there was substantially less coverage of “mozzie stories” in the traditional media this season compared to previous years.

A chart showing the mix of tweets, retweets and replies in 50 of my weekly sampled tweets

Many of the replies I tweeted were promoted by questions directed towards me following my tweets. Some were requests for more information or clarification on mosquito-borne disease activity or for my thoughts on recently published studies or news reports. I made an effort to respond to everyone who tweeted me. Interestingly, a recent paper by Neiger et al. (2013) titled “Evaluating social media’s capacity to develop engaged audiences in health promotion settings: Use of Twitter metrics as a case study” identified the number of questions and interaction between a user and their followers as a measure of “medium engagement”.

Finally, what was the reach and exposure of my tweets over this six month period? This was some of the most surprising information. Despite a relatively modest number of followers, my average weekly reach as approximately 19,000 and estimated exposure approximately 45,000. Much of the added reach and exposure came from multiple RT of my messages, not only accounts with large followers (e.g. media outlets) but from RTs by multiple users with similarly modest follower counts. I think this information shows the power of a small but engaged group of followers.

Chart showing the “reach” and “exposure” of the 50 tweets in my weekly sample

What influenced changes in reach and exposure?

Following the release of a health warning by NSW Health in mid-December 2012 (it is typical of health departments to release a warning about the start of the mosquito season every year) combined with a piece on mosquitoes on The Conversation, I was asked to do a series of radio interviews, mostly with stations in the ABC radio network. All had Twitter accounts that retweeted my link to repellent use guidelines following the interview. There would also often be some additional questions and comments tweeted about following the interview that I could respond to.

It is also easy to often forget who is following these accounts. In the case of 702 Sydney, whose account has over 20,000 followers, following an interview on why some people are bitten more by mosquitoes than others, I even received a tweet from the NSW Premier.

The peak in estimated exposure of my Twitter account came in early January. This was following an appearance on the Today show (a nationally broadcast tv breakfast show). Following an appearance to talk about mosquito repellents and their use, I had a tweet of mine retweeted by the producers and host of the program and this was subsequently retweeted by a number of their followers too. It provided exposure of a link to my guidelines for mosquito repellent use to almost 100,000 unique twitter accounts (with estimated exposure of approximately 188,000). As a result, I had over 200 visitors view the guidelines within a couple of days. That may be less than 1% of the people that saw the original link but still a substantial jump in the amount of people who would have otherwise visited the guidelines. I wonder how many people visit the “mosquito fact sheet” on the NSW Health website after a media release goes out?

So, what does all this mean for the potential benefits of Twitter?

In short, I think it Twitter provides a complementary route of community engagement to traditional methods. It certainly doesn’t replace any of the traditional methods of community or media engagement but I think it will become increasingly important in the future. From my experience, the ability to engage with local media outlets greatly increases the potential reach and exposure of information you can provide. This is particularly the case when links can be tweeted (and hopefully retweeted) that direct people to credible sources of public health information. The more people are aware of the risks associated with mosquito-borne disease, and the strategies available to reduce those risks, the better the public health outcomes.

The analysis of the reach and estimated exposure of my tweets demonstrates how, even from a Twitter account with a modest number of followers, messages can reach a much larger audience. That audience can be increased by being more engaged with followers. It isn’t just the Twitter accounts of media outlets and journalists. I’ve found that there are many active Twitter users who tweet and retweet material covering a wide range of topics. These users are actively engaged with a large cross section of other users and when they retweet material, messages are received by accounts that may not even think to seek out an account tweeting about mosquito-borne disease!

I am confident that the use of Twitter can assist in getting the community more engaged in public health issues, not only mosquito-borne diseases! Developing better strategies for the use of social media (by both health departments and individuals) as well as an assessment of whether those strategies are successful is required.

The buzz of bat conservation

Illustration by Golly Bard (Check out some of the other wonderful illustrations of plants and animals by Golly Bard at her Etsy site)

What is the ecological role of mosquitoes?

There is a huge gap in our knowledge of mosquitoes and their place in the world. There are very few studies that have investigated what environmental “good’ they may do. This would actually be a pretty handy thing to find out. A better understanding of their ecological role may assist balancing the objectives of mosquito control and wetland/wildlife conservation that all too often appears to be (or is perceived to be) in conflict. The results of our newly published study in PLoS ONE may help in understanding the ecological role of one mosquito species in coastal wetlands.

There have been plenty of studies that have documented mosquitoes in the diet of a range of animals such as predatory aquatic macroinvertebrates, fish, frogs, lizards, birds and bats. However, the importance of mosquitoes in the diet of these animals either hasn’t been quantified or can often be overstated. One example often cited is that tadpoles eat mosquito larvae. When we tested some common Australian tadpoles, results demonstrated that they rarely consume mosquito larvae. We need to build our understanding of how important mosquitoes are (or perhaps are not) to local ecosystems.

There are almost 80 species of bat in Australia. While fruit bats may be the most commonly encountered, insectivorous bats are a less well known but diverse group of bats. These often tiny bats (often weighing less than 10g) are usually found in small and far less conspicuous groups. Many of them are found in close proximity to humans and many even be present in in major cities like Sydney. Many are listed as threatened or endangered.

The management of these bat species faces many challenges. Notwithstanding the threat of urbanisation and direct impacts on roost and foraging habitats, indirect impacts may also be important. One potential prey in the diet of bats that may be regionally important is the mosquito. Could broadscale mosquito control programs impact local bat populations?

Saltmarshes have already been identified as important habitats for the saltmarsh mosquito, Aedes vigilax. The abundance of these mosquitoes can dramatically increase in response to tidal flooding of coastal wetlands and nuisance-biting impacts can be widespread in the local community as these species disperse widely from local wetlands. This mosquito is also the major vector of Ross River virus in coastal Australia. There are about 5,000 cases of human illness caused by Ross River virus each year across Australia.

An example of saltmarsh habitats in Empire Bay, Central Coast, NSW

Mosquito-borne disease is an ongoing concern in many parts of Australia, particularly coastal regions. There is a range of environmentally sensitive mosquito control strategies available that have been demonstrated to provide effective mosquito control without directly adversely impacting the local environment. However, studies have shown that it is preemptive, not reactive, mosquito control efforts that have a significant impact on reducing mosquito-borne disease risk. Some concerns have been expressed by local authorities regarding the potential indirect non-target impacts on insectivorous bats of reducing local mosquito abundance.

In 2007, a multidisciplinary research project, funded by a research grant from the NSW Environmental Trust, kicked off to investigate the importance of saltmarsh mosquitoes to local bat populations on the Central Coast of NSW. The 4 year project included researchers from the Australian Catholic University, University of Sydney and Forest Science Centre (NSW Department of Primary Industries). The hard work in this project was done by PhD candidate Leroy Gonsalves (Dr Gonsalves now!).

Leroy Gonsalves (Photo ACU Media)

The project was undertaken in a region where mosquitoes had been identified as both a nuisance-biting problem and potential public health risks but local authorities were reluctant to undertake broadscale mosquito control. For full details, see the Living with Mosquitoes document I produced for local councils in the region.

Our previously published studies analysing bat call recordings have shown that the activity of insectivorous bats can be influenced by the abundance of prey as well as the structure of local habitats. Bats use sound for the detection and capture of prey, as well as navigation, and, as calls are species-specific, an analysis of recordings can determine the bat species present in local habitats and what they’re doing there.

In this newly published paper, we radio-tracked Vespadelus vulturnus (little forest bat), a species known to be a predator of saltmarsh mosquitoes. The activity of these radiotracked bats could be monitored across a range of habitats (including saltmarsh and adjacent coastal swamp forest) when mosquito populations were at naturally relatively high and low abundances.

Bats were collected using harp nets set along flyways in the coastal swamp forest close to the estuarine wetlands. The collected bats were then fitted with small radio-transmitters and released. The activity of each bat was tracked over a period of up to 10 days whereby triangulating the signal direction could record where the bats were active, as well as allowing the identification of day roost sites. This data was then analysed together with prey (mosquito and moth) abundance data recorded using light and carbon dioxide baited traps.

An example of a harp net set to collect microbats (Photo Doug Beckers)

The results were interesting.

When mosquito abundance was high, the saltmarsh was selected preferentially for foraging instead of the coastal swamp forest. However, at times of low mosquito abundance, the bats spread their activity across a range of habitats. The results suggest that this species of bat may be moving into habitats of high mosquito abundance to feed.

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

This is the first radio-tracking study to demonstrate a shift in habitat use by an insectivorous bat species in association with fluctuations in the abundance and distribution of a particular prey population. The shift in habitat use by the little forest bat suggests that, for this species, the saltmarsh mosquito may be an important food item (at least at times when mozzies are abundant).

Does this mean that broadscale mosquito control activities should stop? There is no doubt that the results of our research indicates that the little forest bat moves into areas where the saltmarsh mosquito is abundant. However, whether reducing the abundance of mosquitoes will have ecological implications is yet to be shown. The bats in our study site certainly weren’t eating enough to reduce nuisance-biting impacts of the mozzies!

The Saltmarsh Mosquito (Aedes vigilax) (Photo: Stephen Doggett)

The implications for wetland management are likely to change from location to location. In areas where there is abundant alternative prey such as moths, or mosquitoes not targeted by control activity, are present, reducing populations of key pest species like the saltmarsh mosquito may be achieved without any significant ecological impact. It is important to note that there is no evidence from our studies that the little forest bat is targetting the saltmarsh mosquito specifically. That mosquito was most abundant in this local area but in some regions along the coast, there are equally abundant mosquitoes (e.g. mosquitoes associated with freshwater or brackish water environments), many of which are not the focus of control efforts.

Perhaps an adaptive management approach is required whereby careful monitoring of bat populations is recommended and that, in areas where local bat populations may be shown to be susceptible, avoid control activities during the lactation period of bats, a time when their energetic demands are greatest. As these periods generally fall in late spring and early summer, as opposed to peak periods of  mosquito-borne disease risk that generally fall in late summer and early autumn, an integrated approach to management of both public health and environmental health can be achieved.

One of the key findings, with implications for further research directions and mosquito management, is that species-specific studies are required to understand the ecological role of mosquitoes. This result indicates that the importance of local mosquitoes for insectivorous bats is likely to be specific species (perhaps both the bat species and mosquito species), as well as no doubt varying from region to region. Managing not just the habitats but the insects associated with them may be important. Maintaining suitable habitats for bats under the pressures of expanding urbanisation along much of coastal Australia is critical. It will take more than just retaining these remnant habitats, it will be the strategies used to manage these wetlands and surrounding habitats that will also be important.

You can read the media release regarding this project and publication at the University of Sydney news page.

The full citation for our new paper is: Gonsalves L, Law B, Webb C, Monamy V (2013) Foraging Ranges of Insectivorous Bats Shift Relative to Changes in Mosquito Abundance. PLoS ONE 8(5): e64081. doi:10.1371/journal.pone.0064081

Photos from the field (2012-2013)

I rarely head out into the wetlands without my camera. Having a stockpile of photos from my various study sites always comes in handy, not only for conference and workshop presentations or lectures but also to assist in interpreting some of my mosquito data. Shifts in the extent of tidal flooding of coastal saltmarsh or growth of invasive aquatic macrophytes across constructed wetlands can be captured pretty easily with a quick shot.

While I hope to upgrade my current camera (Canon PowerShot S5iS) to a digital SLR someday, having an iPhone (and being an avid user of Instagram) has opened up a whole new range of possibilities. The convenience of carrying around a reasonable quality camera has been great. Certainly much easier than carrying my other camera bag when I’ve got mosquito traps and other equipment to lug around.

I regularly post photos from the field to my “Wetland Field Guide” tumblr but I thought I’d put together a bunch of my favourite photos here from the recently completed “mosquito season”. This collection is from those posted to Instagram during the season. The vast majority of my field work is conducted between November and April each year. While it isn’t unusual to be out collecting data in early Spring, or even into May occasionally, it looks like I can pack away the gumboots for this season.

I hope you enjoy these shots.

Hexham Swamp (Newcastle)

Kooragang Island (Newcastle)

Newington Nature Reserve (Sydney Olympic Park)

Badu Mangroves (Sydney Olympic Park)

Narrawang Wetlands (Sydney Olympic Park)

Jerrabomberra Wetlands (ACT)

Gungahlin Wetlands (ACT)

Badu Saltmarsh (Sydney Olympic Park)

Kooragang Island (Newcastle)

Ironbark Creek, Hexham Swamp (Newcastle)

Ironbark Creek, Hexham Swamp (Newcastle)

Saltmarsh, Newington Nature Reserve (Sydney Olympic Park)

Saltmarsh, Newington Nature Reserve (Sydney Olympic Park)