Talking wetlands, wildlife and mosquitoes at the 2017 Australian Entomological Society Meeting


I’ll be in Terrigal, on the NSW Central Coast, for the 2017 Australian Entomological Society conference and taking the opportunity to present a summary of a number of collaborative projects undertaken in recent years, from working out how surrounding landuse influences the mosquito populations in urban mangroves to how important mosquitoes are to the diet of local bats.

Together with a range of colleagues, I’ve been undertaking research into the factors driving mosquito and mosquito-borne disease risk in urban wetlands. It is a complex puzzle to solve with more than just mosquitoes determining local pest and public health risks. However, with outbreaks of mosquito-borne Ross River virus on the rise in recent years, including urban areas of Australia, there is a need to better understand the factors at play.

There is a range of factors that may increase the risk of Ross River virus, they include suitable wetlands, wildlife reservoirs of the pathogen and mosquitoes. Understanding the mosquitoes associated with urban estuarine and freshwater wetlands is critical.

Investigating the role of surrounding landuse in determining the mosquito communities of urban mangroves, we found that industrial and residential areas tended to increase abundance of mosquitoes, perhaps due to direct or indirect impacts on the health of those mangroves. We’ve found previously that mosquitoes problems are often associated with estuarine wetlands suffering poor health, perhaps this is determining the increased mosquito risk we identified? You can read more in our publication here.

Expanding the investigation to look at urban freshwater wetlands, it was found that there was a high degree of variability in local mosquito populations and that each wetland needed to be assessed with consideration to be given to site-specific characteristics. You can read more about our work investigating mosquito assemblages associated with urban water bodies in our publication here.

More research is underway in this field and my PhD student, Jayne Hanford, has already started collecting some fascinating data on wetland biodiversity and local mosquito populations.

While the focus of our studies is often prompted by concern about Ross River virus, interestingly, in recent years we’ve found considerable activity of Stratford virus. This is not currently considered a major human health concern but given how widespread it is, it raises concerns about the suitability of local wildlife, even in Western Sydney, to represent important reservoirs of mosquito-borne pathogens. You can read more about Stratford virus in our publication here.

The final piece of the puzzle is to understand the ecological role of mosquitoes. Where their potential health threats are deemed significant, how could management of mosquito populations have unintended consequences for other wildlife. What about the animals that eat mosquitoes? A number of years ago we did some research to determine the importance of mosquitoes in the diet of coastal bats. While there was no indication that mosquitoes are a critical component of their diet, they are still being snacked on and mosquito control programs need to consider any local ecological impacts.

Now, how am I going to squeeze all this into 15 minutes….

The presentation abstract is below:

What drives mosquito-borne disease risk in urban wetlands?

Webb, C. (1, 2), J. Hanford (3), S. Claflin (4), W. Crocker (5), K. Maute (5), K. French (5), L. Gonsalves (6) & D. Hochuli (3)

(1) Department of Medical Entomology, NSW Health Pathology, Westmead Hospital, NSW 2145; (2) Marie Bashir Institute of Infectious Diseases and Biosecurity, University of Sydney, Camperdown, NSW 2006; (3) School of Life and Environmental Sciences, Faculty of Science, The University of Sydney, Camperdown, NSW, 2006; (4) Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, 7000; (5) Centre for Sustainable Ecosystem Solutions, Biological Sciences, Faculty of Science, Medicine & Health, University of Wollongong NSW, 2522; (6) School of Arts and Sciences, Australian Catholic University, North Sydney, NSW, 2060.

Managing pest and public health risks associated with constructed and rehabilitated urban wetlands is of increasing concern for local authorities. While strategic conservation of wetlands and wildlife is required to mitigate the impacts of urbanisation and climate change, concomitant increases in mosquitoes and mosquito-borne disease outbreak risk must be addressed. However, with gaps in our understanding of the ecological role of mosquitoes, could control strategies have unintended adverse impacts on vertebrate and invertebrate communities? A series of studies were undertaken in urban wetlands of greater Sydney to investigate the role of land use, wetland type and wetland aquatic biodiversity in driving the abundance and diversity of mosquito populations. A diverse range of mosquitoes, including key pest an vector species, were found in urban environments and mosquito-borne pathogens were detected in local populations, implicating local wildlife (e.g. water birds and macropods) as potential public health risk factors. Estuarine wetlands are locally important with the percentage of residential land and bushland surrounding wetlands having a negative effect on mosquito abundance and species richness while the amount of industrial land had a significant positive effect on species richness. Mosquito control in these habitats is required but insectivorous bats were identified as mosquito predators and the indirect implications of mosquito control should be considered. The aquatic biodiversity of urban freshwater wetlands influenced the species richness of local mosquito populations indicating vegetation plays an important role in determining local pest species. However, the matrix of wetland types also influences the abundance of mosquitoes in the local area. These results demonstrate the need for site-specific investigations of mosquito communities to assist local authorities develop policies for urban development and wetland rehabilitation that balance the need for conservation with reduced public health risks.

To keep up to date on what’s happening at the conference, check out the program online or follow the conversation on Twitter.


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

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

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

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

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

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

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

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

You can view my presentation slides and abstract below:

Developing a strategic response to exotic mosquito threats in NSW

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

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

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

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

Australian Entomological Society conference 2013


Common bed bug (Photo: Stephen Doggett, Medical Entomology, Pathology West – ICPMR Westmead)

The annual conference of the Australian Entomological Society is on next week. Although I’ll be missing the trip to Adelaide this year, our lab will be represented with some presentations on bed bugs and biting insects!

The 44st AGM and Scientific Conference of the Australian Entomological Society will be held from 29 September through until 2 October 2013 in Adelaide, South Australia. These meetings are great and I’m disappointed not to be attending this year. The meetings attract a wide range of researchers in the field of entomology, from those working on agricultural pests through to ecologists using arthropods to measure environmental change.

The theme of the conference is “Invertebrates in extreme environments”. I was originally planning on presenting some work on the saltmarsh mosquito, Aedes vigilax. This is an insect that thrives in the super saline conditions of tidally influenced saltmarsh habitats. It has adapted to these environments be developing dessication resistant eggs, the ability to lay its first batch of eggs without the need for a blood meal and can disperse many kilometers from the wetlands. It also happens to be a major nuisance-biting pest and vector of pathogens including Ross River virus. Time and budgets squished that plan unfortunately, perhaps next time.

I will be there in spirit though as co-author on a couple of presentations:

A New Resource on Medical Entomology

Webb, C.E., Doggett S.L. & Russell R.C.

The field of medical entomology covers much more than just mosquitoes! A new resource will soon be available to those government and non-government organisations that often need to provide advice on a range of arthropods of medical importance in Australia. The Environmental Health Committee (enHealth) of the Australian Government Department of Health and Ageing has commissioned the production of revised guides for the management of arthropod pests of public health importance in Australia. The original document, Guidelines for the Control of Public Health Pests: Lice, fleas, scabies, bird mites, bedbugs and ticks, was produced in 1999 and, while providing a useful resource for environmental health officers responding to enquiries from the general public, much of the information had become outdated. There was also a number important pests and/or pest groups left out of the original document. A new version of the document is expected to be made available for public comment in 2013 and this presentation will summarise some of the key features of, and additions to, the revised document.


Insecticide Resistance In Bed Bugs In Australia: Are They Getting A Little Too Cozy In Your Bed?

Lilly, D.G., M.P. Zalucki, S.L. Doggett, C.J. Orton, R.C. Russell & C.E. Webb

Insecticide resistance in bed bugs has been nominated as a major factor in the pest’s resurgence. Recent studies using field and laboratory strains of Cimex lectularius and C.hemipterus across Europe, Africa, Asia and North America have variously demonstrated resistance to the pyrethroids, carbamates and, to a lesser extent, the organophosphates. Resistance has been suspected in Australia, with anecdotal reports of treatment failures due to poor product performance. Early efficacy investigations on a range of formulated products found indications of resistance in an Australian derived strain of C. lectularius. To confirm if resistance was present, four compounds (permethrin, deltamethrin, bendiocarb and pirimiphos-methyl) encompassing the major groups of insecticides then registered for bed bug control in Australia were selected for bioassay along with one compound (imidacloprid) to which strains should not have received any exposure at that time. LD50 values (at 24 h) were determined via topical application of the technical grade compounds serially diluted in acetone against a suspected resistant strain (collected from and designated the ‘Sydney’ strain) and a susceptible laboratory strain imported from Bayer CropScience AG, Germany (the ‘Monheim’ strain). All tests were conducted using mixedsex adult bed bugs that had been offered a blood meal within the last 7 days. All compounds tested against the Monheim strain demonstrated high levels of insecticidal activity. However, for the Sydney strain only pirimiphos-methyl and imidacloprid showed high levels of efficacy. Bendiocarb, permethrin and deltamethrin all failed to return greater than 60% mortality at the maximum applied rate of 100μg/μL. The resistance factor (calculated as: Sydney LD50 / Monheim LD50) for each compound was:permethrin = 1.4 million, deltamethrin = 430,000, bendiocarb = 240, pirimiphos-methyl =2.8, imidacloprid = 2.7. Thus using this experimental protocol, resistance was detected with the pyrethroids and carbamates, but not the organophosphates or neonicotinoids (with thedifferences reflected against those compounds likely due instead to a minor resistance- related fitness cost or physiological difference between the strains). This research has significant implications for current and future insecticide management when attempting to control bed bugs. Further studies are ongoing to determine the mechanism(s) of resistance.

It looks like it will be a great meeting with lots of interesting presentations. The full program is available here and I hope there’ll be some tweeting using the hastag #AES2013