Mosquitoes, Gold Coast and the latest arbovirus research

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This week I’ve been on the Gold Coast for the 12th Mosquito Control Association of Australia and Arbovirus Research in Australia Symposium. The theme of the meeting was “Managing challenges and threats with new technology” and included presentations covering a range of topics, from remote piloted aircraft for mosquito control to the discovery of insect-specific viruses and their potential to stop outbreaks of mosquito-borne disease.

You can check out some of the tweets shared during the meeting here.

I found myself on ten papers presented at the meeting and I’ve provided the abstracts below!


Does surrounding land use influence the mosquito populations of urban mangroves?

Suzi B. Claflin1 and Cameron E. Webb2,3

1Department of Entomology, Cornell University, Ithaca, NY, USA; 2Marie Bashir Institute of Infectious Diseases and Biosecurity, University of Sydney, Sydney, NSW; 3Department of Medical Entomology, NSW Health Pathology, Westmead Hospital, NSW 2145, Australia

Mosquitoes associated with mangrove habitats pose a pest and public health risk. These habitats in urban environments are also threatened by urbanisation and climate change. As a consequence, urban mangrove management must strike a balance between environmental conservation and minimising public health risks. Land use may play a key role in shaping the mosquito community within urban mangroves through either species spillover or altering the abundance of mosquitoes associated with the mangrove. In this study, we explore the impact of land use within 500m of urban mangroves on the abundance and diversity of adult mosquito populations. Carbon dioxide baited traps were used to sample host-seeking female mosquitoes around nine mangrove forest sites along the Parramatta River, Sydney, Australia. Specimens were identified to species and for each site, mosquito species abundance, species richness and diversity were calculated and were analyzed in linear mixed effects models. We found that the percentage of residential land and bushland in the surrounding area had a negative effect on mosquito abundance and species richness. Conversely, the amount of mangrove had a significant positive effect on mosquito abundance, and the amount of industrial land had a significant positive effect on species richness. These results demonstrate the need for site-specific investigations of mosquito communities to assist local authorities develop policies for urban development and wetland rehabilitation.


Do urban wetlands increase mosquito-related public health risks?

Jayne K. Hanford1, Cameron E. Webb2,3, Dieter F. Hochuli1

1 School of Life and Environmental Sciences, The University of Sydney, Sydney; 2 Medical Entomology, NSW Health Pathology, Level 3 ICPMR, Westmead Hospital, Westmead; 3Marie Bashir Institute of Infectious Diseases and Biosecurity, The University of Sydney, Sydney

Wetlands in urban areas are frequently constructed or rehabilitated to improve stormwater quality and downstream aquatic health. In addition to improving water quality, these wetlands can provide aesthetic, recreational and biodiversity values to communities. However, urban wetlands are often perceived to proliferate nuisance-biting and pathogen-transmitting mosquitoes which can, in severe cases, erode goodwill in the community for protecting these valuable ecosystems.  We compared mosquito assemblages at 24 natural and constructed wetlands in the greater Sydney region, Australia. Our aims were to determine if wetlands with high aquatic biodiversity posed reduced mosquito-related public health risks, and if these links vary across the urban-rural gradient. At each wetland we sampled adult and larval mosquitoes, aquatic macroinvertebrates and physical habitat variables on two occasions through summer and autumn.  Although larval mosquito abundance was low across all sites, there was a high diversity of adult mosquito species, and assemblages varied greatly between sites and seasons. Species of wetland-inhabiting mosquitoes showed vastly different responses to aquatic biodiversity and physical habitat variables. There were strong relationships between the abundance of some mosquito species and aquatic macroinvertebrate richness, while others mosquito species showed strong relationships with the percentage of urbanisation surrounding the wetland.  Effectively integrating wetlands into cities requires balancing wetland design for water infrastructure purposes, biodiversity resources and public health and wellbeing requirements. Understanding relationships between biodiversity value and mosquito-related public health risks will enhance the value of constructed urban wetlands in cities while minimising risks posed by mosquitoes.


Aedes aegypti at Sydney Airport; the detections and response

Doggett, S.L. and Webb C.E

Department of Medical Entomology, CIDMLS, Pathology West, ICPMR,
Westmead Hospital, Westmead, NSW.

Despite a huge increase in the detections of exotic vectors at ports around Australia, up until 2016 there had been no detection of Aedes aegypti at the Sydney International Airport. However, this changed on 14/Jan/2016 when two larvae were observed in an ovitrap serviced by the Department of Agriculture and Water Resources (formerly AQIS), as part of their routine surveillance activities for the detection of exotic vectors. These larvae were confirmed as being Ae. aegypti. Thereafter, there were a further nine separate detections of Ae. aegypti up until 4/Mar/2016. Six were via BG traps, one in an ovitrap, and there were two separate instances of an adult mosquito being collected in open areas. The majority of detections occurred in areas of the airport known as the ‘basement areas’. This is where the bags are unloaded from the air cans onto convey belts for collection directly upstairs by the passengers. Response measures undertaken included: (1) enhanced surveillance; BG traps were increased in number from 2 to 12, and traps inspected at more frequent intervals; (2) insecticide treatments; thermal fogging and surface sprays were conducted of the relevant areas; (3) vector surveys; a comprehensive audit of the airport was undertaken to examine the potential for localized mosquito breeding. In the case of the vector surveys, some 107 potential sites were identified and grouped into risk categories. No Ae. aegypti were discovered breeding, although Cx. quinquefasciatus and Ae. notoscriptus were found, and recommendations to prevent future localized breeding were made.


Communicating the risks of local and exotic mosquito-borne disease threats to the community through social and traditional media

Cameron E Webb1,2

1Department of Medical Entomology, NSW Health Pathology, Level 3, ICPMR, Westmead Hospital, WESTMEAD NSW 2145 AUSTRALIA; 2Marie Bashir Institute of Infectious Diseases and Biosecurity, University of Sydney, NSW 2006, AUSTRALIA

Mosquito-borne disease management in Australia faces challenges on many fronts. Many gaps exist in our understanding of the drivers of exotic and endemic mosquito-borne disease risk but also the pathways to ensuring the community embrace personal protection measures to avoid mosquito bites. While traditional media has been the mainstay of public health communications by local authorities, social media provides a 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.

See the slides here.


So, you want to write a field guide?

Cameron E. Webb1,2, Stephen L. Doggett1 and Richard C. Russell2

1Department of Medical Entomology, NSW Health Pathology, Level 3, ICPMR, Westmead Hospital, WESTMEAD NSW 2145 AUSTRALIA; 2Marie Bashir Institute of Infectious Diseases and Biosecurity, University of Sydney, NSW 2006, AUSTRALIA

We know a lot about Australian mosquitoes. They’re one of the most studied insects in the country. Their pest and public health threats warrant a better understanding of their biology and ecology. There is still plenty we don’t know. We may not understand their ecological role in the local environment very well and there are many mosquitoes we know exist but have very little information about them. We still need to give many mosquitoes a formal scientific name. There is a reason why so many field guides are written by retired scientists. It’s not just about expertise, it’s about time too! In early 2016, “A Guide to Mosquitoes of Australia” to was published by CSIRO Publishing and marked the culmination of many years work. This work involved chasing mosquitoes from coastal rock pools to snow melt streams. We carried eskies of buzzing mosquitoes on airplanes from northern Australia to laboratories in Western Sydney and there were many late nights of wrangling those mosquitoes to get the perfect photo. Lots of mosquito bites too. Many, many mosquito bites. Putting together this field guide wasn’t an easy task and for all those involved it proved a challenge in many different ways. Digging out old papers to colour-correcting digital photographs proved time consuming but the biggest delays in finishing this project was a problem that plagues many field guide writer, “species creep”! Completing the guide was only possible with the kindness, generosity and co-operation of many mosquito researchers around the country.

See the slides here.


Arbovirus and vector surveillance in NSW, 2014/15-2015/16

 Doggett, S.L., Clancy, J., Haniotis, J., Webb C. and Toi, C.

Department of Medical Entomology, CIDMLS, Pathology West, ICPMR,
Westmead Hospital, Westmead, NSW.

The NSW Arbovirus Surveillance and Vector Monitoring Program acts as an early warning system for arbovirus activity. This is achieved through the monitoring of mosquito abundance, detection of arboviruses from mosquitoes, and the testing for seroconversions to MVEV and KUNV in sentinel chickens. A summary of the last two seasons will be presented. The 2014-2015 season started early with elevated temperatures through late 2014, however conditions were relative dry with neither Forbes’ nor the Nicholls’ hypothesis being suggestive of an MVEV epidemic. Despite this, for the inland region, human notifications were close to average, with 260RRV & 11BFV). There were 12 arboviral detections from the inland including 5BFV, 6RRV & 1STR, with no seroconversions. In contrast, the coastal strip experienced the largest epidemic of RRV in recorded history. The 1,225 cases were close to double the average, with much of the activity occurring in the far north coast. There were 41 isolates from the mosquitoes trapped along the coast and included 6BFV, 29RRV, 4EHV and 2STRV. An intense El Niño occurred during the 2015-2016 season and thus it was extremely dry across the state. Again the Forbes’ and the Nicholls’ hypothesis were not suggestive of an MVEV outbreak. For the inland, mosquito numbers were well below average and there were only two arboviral detections from the mosquitoes (1RRV & 1 BFV), with no seroconversions. Similarly, mosquito collections were below average and there were also two arboviral detections from the trapped mosquitoes (1BFV & 1EHV). Human cases were below average.


Are remote piloted aircraft the future of mosquito control in urban wetlands?

Cameron E Webb1,2 Stephen L. Doggett1 and Swapan Paul3

1Department of Medical Entomology, NSW Health Pathology, Level 3, ICPMR, Westmead Hospital, WESTMEAD NSW 2145 AUSTRALIA; 2Marie Bashir Institute of Infectious Diseases and Biosecurity, University of Sydney, NSW 2006, AUSTRALIA; 3Sydney Olympic Park Authority, 8 Australia Ave, Sydney Olympic Park NSW 2127, AUSTRALIA

Mosquito control in urban wetlands will become increasing important. The expansion of residential areas will continue to encroach on natural mosquito habitats, particularly coastal wetlands, and expose the community to the health risks associated with mosquitoes. In many existing areas, ever increasing density of human populations associated with high rise residential developments will further expose people to mosquitoes. The increasing urban development adjacent to wetlands can restrict the ability to use traditional larvicide and insect growth regulator application methods. In 2016 a trial of larvicide application via remote piloted aircraft was undertaken in an area of estuarine wetlands at Sydney Olympic Park. An existing mosquito control program involving helicopter application of larvicides has been in place for over a decade. Post-treatment mortality of Aedes vigilax and Culex sitiens larvae was compared between bioassay and long-term surveillance sites within the wetlands. While there was a substantial reduction in larval densities post-treatment, the treatments via remote piloted aircraft were less effective than those of traditional piloted aircraft. The results of this preliminary trial suggest that the use of remote piloted aircraft has potential but the operational aspects of this application method requires careful consideration if there are to be as effective as existing strategies.


Seasonal Activity, Vector Relationships and Genetic Analysis of Mosquito-Borne Stratford Virus

Cheryl S. Toi1, Cameron E. Webb1,2, John Haniotis1, John Clancy1 and Stephen Doggett1

1Department of Medical Entomology, Centre for Infectious Diseases and Microbiology Laboratory Services, Pathology West – Institute for Clinical Pathology and Medical Research, Westmead Hospital, NSW; 2Marie Bashir Institute for Infectious Diseases and Biosecurity, University of Sydney, Institute for Clinical Pathology and Medical Research, Westmead Hospital, NSW;

There are many gaps to be filled in our understanding of mosquito-borne viruses, their relationships with vectors and reservoir hosts, and the environmental drivers of seasonal activity. Stratford virus (STRV) belongs to the genus Flavivirus and has been isolated from mosquitoes and infected humans in Australia. However, little is known of its vector and reservoir host associations. A total of 43 isolates of STRV from field collected mosquitoes collected in NSW between 1995 and 2013 were examined to determine the genetic diversity between virus isolates and their relationship with mosquito species by year of collection. The virus was isolated from six mosquito species; Aedes aculeatus, Aedes alternans, Aedes notoscriptus, Aedes procax Aedes vigilax, and Anopheles annulipes. While there were distinct differences in temporal and spatial activity of STRV, with peaks of activity in 2006, 2008, 2010 and 2013, there was a high degree of sequence homology (89.1% – 97.7%) found between isolates with no evidence of mosquito species, geographic, or temporal divergence. The result suggests the virus is geographically widespread in NSW (albeit only from coastal regions) and increased local STRV activity is likely to be driven by reservoir host factors and local environmental conditions influencing vector abundance. While STRV may not currently be associated with major outbreaks of human disease, with the potential for urbanisation and climate change to increase mosquito-borne disease risks, and the potential for genomic changes which could produce pathogenic strains, understanding the drivers of STRV activity may assist the development of strategic response to public health risks posed by zoonotic flaviviruses in Australia.


Insect specific flaviviruses suppress West Nile virus replication and transmission

Sonja Hall-Mendelin1, Breeanna McLean2, Helle Bielefeldt-Ohmann3, Cameron E. Webb4 Jody Hobson-Peters2, Roy Hall2, Andrew van den Hurk1

1Public Health Virology, Forensic and Scientific Services, Department of Health, Queensland Government, PO Box 594, Archerfield 4108, Queensland, Australia; 2Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia 4072, Queensland, Australia; 3School of Veterinary Science, The University of Queensland, Gatton Campus, Gatton 4343, Queensland, Australia; 4Medical Entomology, Marie Bashir Institute of Infectious Diseases and Biosecurity, The University of Sydney, NSW, Australia

Diseases caused by mosquito-borne flaviviruses, including dengue (DENV), Zika and West Nile viruses (WNV), are a global problem. New molecular tools have led to recent discoveries of a plethora of insect-specific flaviviruses (ISF) that infect mosquitoes but not vertebrates. Preliminary reports have suggested that transmission of WNV can be suppressed by some ISFs in co-infected mosquitoes, thus the ecology of ISFs and their potential as natural regulators of flaviviral disease transmission is intriguing. In vitro studies with two ISFs discovered in Australia, Palm Creek virus (PCV) and Parramatta River virus (PaRV), demonstrated suppression of WNV, Murray Valley encephalitis virus (MVEV) and DENV replication in mosquito cells (C6/36) previously infected with either of these ISFs. Further in vivo experiments indicated that these ISFs were not transmitted horizontally in the saliva, and that PaRV relied on vertical transmission through the mosquito egg to the progeny. Additional studies revealed a significant reduction of infection and transmission rates of WNV when Culex annulirostris were previously infected with PCV, compared to control groups without PCV. Of particular interest was the specific localisation of ISFs to the midgut epithelium of mosquitoes infected via natural route (vertical transmission – PaRV) or by intrathoracic injection (PCV). Overall these results confirm a role for ISFs in regulating the transmission of pathogenic flaviviruses by mosquitoes and that this interference may occur in the midgut where initial infection occurs. Further research is needed to determine the precise mechanism of this phenomenon and its potential for mosquito-borne disease management.


Neges, Nidos and Nings – so that’s what’s killing my mossie cells!

Roy Hall1, Jody Hobson-Peters1, Helle Bielefeldt-Ohmann1, Caitlin O’Brien1, Breeanna McLean1, Agathe Colmant1, Jessica Harrison1, Thisun Piyasena1, Natalee Newton1, Waylon Wiseman1, Marcus Mah1,2, Natalie Prow2, Andreas Suhrbier2, David Warrilow3, Andrew van den Hurk3, Sonja Hall-Mendelin3, Cheryl Johansen4, Steven Davis5, Weng Chow6, Stephen Doggett7, John Haniotis7 and Cameron Webb7.

1Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Australia; 2QIMR Berghofer Medical Research Institute, Herston, Brisbane, Australia; 3Public Health Virology, Forensic and Scientific Services, Coopers Plains, Queensland, Australia; 4Arbovirus Surveillance and Research, Infectious Diseases Surveillance Unit, PathWest Laboratory Medicine WA, Western Australia; 5Berrimah Veterinary Laboratories, Department of Primary Industry and Fisheries, Darwin, Northern Territory, Australia; 6Vector Surveillance and Control, Australian Army Malaria Institute, Enoggera, Queensland, Australia; 7Department of Medical Entomology, West Westmead Hospital, Westmead, NSW, Australia.

Isolation of viruses from mosquitoes is an important component of arbovirus surveillance and virus discovery programs. In our lab, these viruses are detected in inoculated cultures by the appearance of cytopathic effects (CPE) in mosquito cell monolayers or by reactivity of monoclonal antibodies to viral antigens or dsRNA intermediates. Isolates are then identified by RT-PCR or deep sequencing.  We detected extensive CPE in many mosquito cell cultures inoculated with mosquito homogenates from several regions of Australia, however these isolates were not identified by specific mAbs or RT-PCRs designed to detect known arboviruses.  When we investigated their identity by deep sequencing, a new species (Castlerea virus – CsV) in the unclassified taxon Negevirus, was identified in several mosquito species from WA and Brisbane. Two viruses in the newly established Mesoniviridae family (order Nidovirales) were also identified; a novel species named Casuarina virus (CASV) from Coquillettidia xanthogaster in Darwin and from Culex annulirostris in Cairns, and the first Australian isolates of Nam Dinh virus from several mosquito species in Brisbane and Perth. Many isolates of a new genetic lineage of Liao Ning virus, a member of the Seadornavirus genus (family Reoviridae), were also obtained from several mosquito species from different regions of Australia.  These new viruses were isolated at very high frequency in some mosquito collections, and were often found to co-infect isolates of other mosquito-borne viruses making it difficult to obtain pure cultures. We have now developed neutralising antibodies to each virus to facilitate selective removal of these viruses from mixed cultures.

 

That was a busy meeting. I’m exhausted but cannot wait until the next meeting in 2018. Are you a member of the Mosquito Control Association of Australia?

 

 

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Does wetland rehabilitation need mosquito control?

Webb_estuarinewetlands_SydneyOlympicPark_2014Mosquitoes can be more than a nuisance. They pose health risks but could also erode the good will of the community for wetland rehabilitation projects. Wetland rehabilitation needs mosquito control.

It’s a warm February evening. A small and anxious group of residents have gathered in a local community hall to discuss the implications of a local wetland rehabilitation project. Some are angry. One of the first questions comes from an elderly gentleman. Close to tears, he explains how his grandchildren no longer visit due to the plagues of mosquitoes that engulf his property day and night. “What are you guys going to do about it?” he pleads.

I learnt a valuable lesson that night. Trying to explain the best mosquito repellent to use doesn’t go down too well when an audience is facing some significant nuisance-biting impacts around their homes. It doesn’t matter how much DEET is in the repellent, it may well work but is it something you need to wear all day just to get the day to day jobs done around the house? Something more substantial is required and, with hindsight, should have been in place before the first waves of mosquitoes left the local wetlands.

Coastal wetlands are under threat

Sea level rise and climate change  is putting pressure on saltmarshes and urbanisation is eating away land that would otherwise accommodate a landward shift in estuarine habitats. There is nowhere for saltmarshes to spread to so they’re destined to be swallowed up by mangroves. While the mangroves are valuable themselves, they don’t provide the same critical habitats required by many of the internationally protected migratory shorebirds that rely on saltmarshes. Saltmarsh habitats could well disappear from much of the east coast in coming decades if sea levels rise as expected and mangroves continue their march landward.

webb_landinglightswetlandsEstuarine wetlands and mosquitoes

Saltmarshes are home to one of our most important pest and vector mosquito species. While it is important to remember that Aedes vigilax is an Australian native animal and just as much a part of our wetland ecosystems as fish and birds, there is little doubt that it can have substantial impacts with regard to nuisance-biting and the transmission of Ross River virus.

Historically, many of the saltmarshes along the east coast were drained or filled to enable increased cattle grazing (although much of it was under the guise of protection from flooding). Tidal flows were cut off with the construction of levee banks and installation of flood gates. Notwithstanding the impacts of grazing, without tidal exchange, the habitats became brackish water to freshwater dominated systems with a dramatic change in vegetation. Saltmarsh and sedgeland vegetation was steadily replaced by reeds and rushes. Invasive plants such as Phragmites quickly took over many of these wetlands.

webb_floodgates_march2011Bringing back the tides

To combat the degradation of wetlands and impending loss due to climate change, there has been some ambitious wetland rehabilitation projects planned. One of the largest in the southern hemisphere is the Hexham Swamp Rehabilitation Project. Much can be learned from the experience in this wetland just west of Newcastle, NSW, and applied to rehabilitation projects, not only in Australia but overseas as well.

Rehabilitation of Hexham Swamp involved the staged opening of existing floodgates to reinstall tidal flows to an otherwise freshwater system. Many aspects of this project were considered and it is unsurprising that one major issue was the possible impact of mosquitoes. Mosquito populations were something of legend in this area, enough so that there is a “big mosquito” outside the local bowling club affectionately known as “Ossie the Mossie” (coincidently, “Ossie” celebrated her 20th birthday in March 2014).

One of the important considerations when assessing mosquito risk was that there had been a dramatic transformation of the areas surrounding the wetlands in the last 20 years. What was once agricultural land was now residential. This is the same situation right along the east coast of Australia, the rapid urbanisation and swelling residential populations along the coast have put people in the firing line of Aedes vigilax.

The prospect of mosquito control was raised in the early stages of the rehabilitation planning but there was great reluctance from the local authorities to head down that path. The problem is that broad scale mosquito control and ecological rehabilitation are often seen at opposite ends of the wetland management spectrum. I’ve experienced this many times first hand, from scepticism regarding the non-target impacts of biological larvicides to “Apocalypse Now” jokes as helicopters go about routine spraying of local wetlands.

Webb_MosquitoCollectionsIs there such a thing as “environmentally friendly” mosquito control?

The hangover from the actual and perceived impacts of pesticide use more than 50 years ago is still present in the minds of many responsible for managing local wetlands. I say perceived as the development of environmentally sustainable mosquito control programs over the past two decades may not be appreciated amongst those charged with managing wetlands and wildlife.

I feel we need to continue building the case for the range of mosquito control strategies available for our coastal wetlands. Not only do we need to convince local authorities that mosquito populations can be minimised without adversely impacting the local environment but that mosquito control should be a critical consideration in wetland rehabilitation projects. It also has the potential to reduce mosquito-borne disease.

We know that the direct non-target impacts of Bacillus thuringiensis israelensis and s-methoprene are minimal and there is growing evidence that the indirect impacts on local wildlife due to reduced mosquito populations isn’t a major concern. Well-designed projects can also minimise the frequency of treatments while reducing peaks in mosquito activity.

It seems our coastal bats populations are mostly eating moths, not mosquitoes so there is unlikely to be any significant impact on these bats resulting from reduced food. There is no reason why the judicious use of larvicides can’t knock the top off abundant mosquito populations, reduce the pest impacts on local community and not pose a risk to local wildlife. Perhaps it should be considered a critical component of wetland rehabilitation?

redkneeddoteral_kooragangisland_march2015Mosquito control and wetland rehabilitation

In speaking with wetland managers, I try to instil with them the importance of mosquito control. There is a risk that swarms of nuisance biting mosquitoes may erode the good will in the community for wetland rehabilitation. These systems, particularly in the early phases of rehabilitation don’t represent pristine environments and while there may not be a desire to establish ongoing mosquito control programs, some control may prove useful while the wetland comes back into balance with the changed environmental conditions.

Rehabilitation takes time and while there is substantial breakdown of freshwater vegetation it is not going to be ideal for fish and other mosquito predators. It is likely to provide ideal conditions for mosquitoes. Over time, however, fish are likely to increase in both their abundance and penetration into the wetlands and greater tidal flushing will make many of the wetland habitats generally unsuitable for mosquitoes.

Perhaps there is benefit in undertaking control as a show of good will to the local community? After all, engagement with the local community will be critical in the success of wetland rehabilitation projects.

The restoration of tidal flows to Hexham Swamp resulted in an initial increase in the abundance of Aedes vigilax. These increases resulted in substantial nuisance-biting impacts. However, in subsequent seasons, the populations of Aedes vigilax levelled out to comparable levels to those of the surrounding estuarine wetlands. The net result has generally been that the long-term moderate increases in Aedes vigilax populations have been balanced by reductions in Culex annulirostris and Coquilettidia linealis populations as the wetlands shifted from freshwater to saline. The health of the wetlands, as well as the local estuary, is improving.

Mosquito control is only a short-term fix and if the rehabilitation of estuarine wetlands is not carefully planned, there may well be ongoing mosquito impacts. However, reducing any initial impacts will go a long way to ensuring continued engagement of the community with the local wetlands. Cost and the operational considerations may be a barrier for organisations unfamiliar with broadscale mosquito control but these issues can be overcome with the expertise that exists in many parts of the country.

In summary, it is important that mosquito management be considered in the planning process of major wetland rehabilitation projects. There is little doubt that such projects will be required into the future as saltmarsh habitats and other estuarine wetlands are threatened but protection wetlands shouldn’t mean increasing mosquito populations. A balance is required between conservation of environmental health and protection of human health.

A longer version of this article originally appeared in “Mosquito Bites” (the Bulletin of the Mosquito Control Association of Australia).

Football, ticks, mozzie vaccinations and big budget repellents: The year ahead in medical entomology

IMG_6223The new year is off and running. What twists and turns will mosquitoes and other biting arthropods provide in the year ahead? Here are just a few of the things I’ll be keeping my eye on.

Ross River virus along the east coast of Australia

Ross River virus is the most commonly acquired mosquito-borne infection in Australia. It causes a potentially serious illness with flu-like symptoms and, although not fatal, can be seriously debilitating. There are around 5,000 cases of disease reported each year with cases reported from across the country. It is something of an urban myth to suggest that “Ross River virus is moving south from Queensland”. In fact, some of the largest outbreaks in recent years have been in southern states. South-west Western Australia has had considerable activity in recent years.

Along the east coast, activity has actually been reasonably low. Flooding of inland regions during 2010-2012 resulted in some substantial activity west of the Great Dividing Range but along the coast, not that much has been happening. One explanation is that the average to above average rainfall the east coast has experienced in recent times is not conducive for the major pest mosquitoes associated with coastal wetlands. With drier conditions forecast for this summer, conditions improve for these mosquitoes. The recent king tides that occurred in the first week of 2014 have provided an opportunity for a major emergence of mosquitoes. This may get the ball rolling for a big year of mosquito activity along the coast.

While we can forecast a rise in mosquito populations, predicting an outbreak of Ross River virus is much more difficult. The key reason for this is that mosquitoes don’t hatch out of the wetlands infected with the virus, they must bite an infective animal (most commonly kangaroos and wallabies) first. This means that complex interactions occur between mosquitoes, environmental conditions and wildlife ecology. We don’t quite understand how all these factors interact just yet. What we do know is that it is unusual to have more than a couple of years without at least a minor outbreak of Ross River virus and with a combination of suitable environmental conditions, could the Autumn of 2014 see a surge in cases of disease?

Tri Nguyen Island, Vietnam. The site of release of Wolbachia infected mosquitoes as part of the Eliminate Dengue project (Photo: Eliminate Dengue)

Will the Eliminate Dengue project eliminate dengue?

The Eureka Prize winning Eliminate Dengue project has many excited by the prospect that mosquitoes could be “vaccinated” against dengue infection. There have been some great results from Cairns, Australia, where field released Wolbachia-infected mosquitoes have natural spread through study sites and successfully replaced large percentages of “wild” mosquitoes. However, it is one thing to have a well resourced field study looking at the spread of Wolbachia infected mosquitoes alone, will they actually reduce rates of dengue? To test the effectiveness in a dengue-endemic region, the Eliminate Dengue project is currently undertaking field testing in Vietnam.

Unfortunately, 2014 hasn’t got off to a good start to the project. News of some small, but not insurmountable, hurdles has come through from Vietnam where populations of Wolbachia-infected mosquitoes on Tri Nguyen Island aren’t persisting at forecast levels. While the rate of Wolbachia-infected mosquitoes reached close to 80% in August 2013, the rate had fallen to below 65% by early December 2013. Whether the falling prevalence of infected mosquitoes is due to higher mortality rates of infected mosquitoes (or at least some degree of reduced competitive advantage) or other environmental factors is yet to be determined. Hopefully better news will come later in the year.

The tick responsible for most bites along the east coast of Australia, the paralysis tick, Ixodes holocyclus. (Photo: Virginia Bear/Sydney Morning Herald)

Pulling ticks and pushing Lyme in Australia

Ticks, and their health impacts, in Australia are gaining some increasing notoriety. We’ve always known that ticks can pose a potentially serious health impact due to bite reactions. There is also the fascinating “tick induced red meat allergy” that is being seen more commonly around Sydney. However, the controversy around the potential presence of a pathogen causing Lyme Disease, or a Lyme-like illness, spread by local ticks has focused the attention of local authorities and communities where ticks are abundant.

It will be interesting to see what comes out of the Tick-induced Allergies Research and Awareness (TIARA) group and the federal government’s Clinical Advisory Committee on Lyme Disease over the coming year. In addition, the largest study into tick-borne pathogens is currently underway at Monash University with specimens being processed from across the country in an effort to find, identify and (hopefully) culture any pathogens present so that we can better understand the complex issues surrounding tick-borne illness.

Even if new tick-borne pathogens are documented, the advice provided by local authorities on avoiding tick bites is unlikely to change significantly. However, what has been missing from the promotion of tick bite prevention methods is some good quantitative evidence on the best measures to prevent bites as well as how best to remove a tick once it has attached. Many of the products promoted for use haven’t been registered by the Australian Pesticides and Veterinary Medicines Authority (APVMA) for use against ticks; creating difficulties for health authorities to recommend their use. Also, despite some recent guidelines on tick removal from Europe, these guidelines may not be appropriate against local ticks that have the potential to cause anaphylaxis and paralysis. So, do you just pull off attached ticks or kill them first with an insecticide? We’re expecting some guidelines from the TIARA group this year (in the meantime, stay tuned for a blog post about this from me in coming weeks).

Dengue & FIFA World Cup in Brazil

There wouldn’t be a better place to be for a football loving entomologist than the FIFA World Cup in Brazil in June & July 2014. Enjoy some football; research some dengue!

Brazil has been a focus for dengue research for many years. With tens of thousands of travelers planning to visit Brazil for the world cup, concerns have been raised regarding the possible risk to travelers of dengue. Those risks are well founded as, not only is dengue endemic in the country, but many of the travelers to Brazil may not be fully aware of the risks and the appropriate personal protection measures they should take. We’ve seen this in recent years with a rise in the number of imported cases of dengue and Chikungunya virus with Australian travelers returning from SE Asian destinations. I’ve written about the need to educate travelers on avoiding mosquito bites in these dengue-endemic regions here.

While there is obviously a risk to travelers, a risk often overlooked is the possibility that travelers returning to their home countries may inadvertently introduce dengue viruses to local mosquito populations. As is the case in Australia, there are regions where suitable mosquitoes are present that can transmit dengue viruses but the disease is not endemic. Sporadic, and occasionally significant, outbreaks are triggered by infective travelers. Could we see locally acquired cases of post-World Cup dengue in North America, Europe or Australia? Conversely, could travelers import a new mosquito-borne virus into South America? (see below)

St Vincent: Holiday destination and location of first Chikungunya cases in the Americas (Telegraph)

Chikungunya in the Americas

2013 was the year that Chikungunya really made its presence felt in Australia. This was due to the Asian Tiger Mosquito knocking at the door of mainland Australia and raising the risk that a temperate climate tolerant mosquito may one day be widespread in Australia and, as a key vector of Chikungunya virus, could pose a serious health risk. Despite no known locally acquired cases of the infection in Australia, the numbers of infected travelers returning from Chikungunya endemic regions jumped dramatically in 2013 with over 100 cases reported compared to an average of about 25 cases for the previous two years.

It was at the end of 2013 that the virus was first detected in the Americas. By the first week of 2014 almost 100 cases now reported from Caribbean island of St Martin. Now with effective vectors of Chikungunya virus throughout much of South America and many parts of North America the question of whether more outbreaks are likely to occur should be asked. With increased travel to South America in conjunction with the FIFA World Cup (and additional tourism activity prompted by the tournament), perhaps the greatest risk is posed by travelers introducing the virus to other countries where suitable vectors are present. Perhaps Zika virus may pop up too in South America too…

Repel_illustration_DSMouthwatering mozzie repellents and a move away from topical formulations

The media love news of a new mosquito repellent. There is likely to be a steady stream of news stories this year about the discovery of new mosquito repellent chemicals. Considerable research is going into the discovery of chemicals, derived from a range of botanical and non-botanical sources, that may hold potential as mosquito repellents. Some neat computational analysis is being done that includes “molecular field topology analysis, scaffold hopping, and molecular docking” to uncover new repellent products. A recent study identified a few “nice” smelling chemicals that may be effective and more user friendly repellents. There also seems to be a focus on products derived from “food grade” substances, I assume as a way to avoid some of the registration obstacles and/or allow greater marketability for the “natural” repellent market. I expect to see many more announcements over the course of the year….but very few new products being made available that will make much of a differences “in the real world” (at least this year).

These “discoveries” are usually framed within the context that N,N-diethyl-3-methylbenzamide (DEET) based repellents are unsafe or unpleasant to use. This argument lacks substance when you considered that the safety of DEET is demonstrated time and time again. In addition, most circumstances call for the use of only a low or moderate concentration DEET-based repellent. A formulation that only contains about 10% DEET will still provide a few hours protection. Interestingly, a lot of the commercial “low dose” DEET-based repellents are being replaced by picaridin-based (a product considered more “user friendly”) repellents here in Australia.

Rather than new active ingredients, what we really need is better formulations. A move away from topical repellents would be a great move and overcome the difficulties in “user compliance” to get the most effective results. The most promising product in this regard is metofluthrin. This product has recently been registered for use by the APVMA in Australia so I’m looking forward to seeing it available in local stores. It has proven to be effective in preventing mosquito bites. What is most interesting is that the product is usually included with battery operated “clip on” devices that individuals wear. They may not prevent bites when mosquito populations are high (e.g. close to wetlands) but could be a useful alternative to topical repellents when mozzies are just causing a mild annoyance.

The half a million dollar mosquito repellent – Kite Patch

$600,000 would buy a lot of mosquito repellent!

One of the most amazing things to happen last year was the phenomenal support provided to a crowd-funded mosquito repellent patch that purported to make the wearer invisible to mosquitoes. The company raised almost US$600,000 for filed testing of their patches in endemic regions of Africa. Yep, over half a million dollars.

I’ve written about what is required to evaluate new mosquito repellents (it was easily the most read post on my blog last year). Field tests of the Kite Patch are scheduled to commence in Uganda in January 2014 so I will be keeping a keen eye out for any updates. Most importantly, I’m keen to see some published peer-reviewed papers reporting on field and laboratory testing of these new repellents. Hopefully we’ll know by the end of the year whether the “dream” of an effective non-topical repellent can become a reality. The next interesting development will be when the patches are sent out to supporters of the crowd funding campaign. This isn’t expected to be until late 2014 or early 2015 (after the completion of Uganda field tests and EPA approvals).

QLDControl1949Australian mosquito researchers head west

The 11th Mosquito Control Association of Australia conference will be held in Mandurah, Western Australia on 7-10 September 2014. The conference will be held at The Sebel Mandurah and is shaping up to be an exciting forum. Mandurah is located an hour south of Perth and plays an important role in mosquito ecology, being located on the Peel and Harvey estuaries with large areas of tidal saltmarsh habitat. Management of mosquitoes and mosquito-borne disease has been an important issue for local authorities.

The theme of the 2014 conference is “Bringing good science to strategic programs” will bring together research entomologists, field biologists, and vector control specialists in a unique networking environment designed to promote collaboration and partnerships to improve preparedness, prevention, and control of vector-borne diseases of medical importance. Keep an eye on the MCAA website for more details in the next month.

So, it looks like there will be plenty of medical entomology stuff to keep an eye on for 2014, I wonder what surprises will be tossed up….