Ross River virus in Melbourne, how did that happen?

aedesnotoscriptus

Health authorities in Victoria have been warning of mosquito-borne Ross River virus for much of the summer. The state is experiencing one of its worst outbreaks of the disease but cases have mostly been across inland regions. Now it’s hit Melbourne. How has this happened?

Ross River virus is the most commonly reported mosquito-borne disease in Australia. There are usually about 5,000 cases across Australia. However, in 2015 there was a major spike in activity with around 9,000 cases reported. It is a common misconception that the disease is only found in northern regions of Australia. I’m often told “I heard the disease is moving south from QLD?” That’s not the case.

The virus is just as much a natural part of the Australian environment as the mosquitoes and the wildlife that maintain transmission cycles.

While there are generally more cases in northern Australia, nowhere is safe. Some of the largest outbreaks have occurred in southern regions of Western Australia, South Australia, Victoria and even Tasmania.

The virus is widespread but is generally associated with rural regions. A driving factor in determining the activity of Ross River virus is that more than just mosquitoes are involved in outbreaks. The virus is maintained in the environment in native wildlife, especially kangaroos and wallabies. Even when and where there are high numbers of mosquitoes, without wildlife, outbreak risk is low. This is the reason why any clusters of locally infected cases in metropolitan regions are typical in areas where there are wetlands, wildlife and mosquitoes occurring together. We’ve seen this on the urban fringe of Sydney and Perth in recent years.

The announcement of locally acquired cases in the suburbs of Frankston and Casey, in Melbourne’s south-east, has taken many by surprise. Should it have?

Victoria is no stranger to mosquitoes and outbreaks of mosquito-borne disease. There are mosquito surveillance and mosquito control programs in place in many regions and historically there have been major outbreaks of mosquito-borne disease. From freshwater flood plains of the inland to the tidally flooded estuarine wetlands of the coast, Victoria has diverse and often abundant mosquitoes. But cases in the metropolitan region are rare.

Victorian mosquitoes are not all bad but over a dozen different mosquito species can spread Ross River virus.

The region where these cases have been identified are in proximity to bushland and wetland areas. There is no doubt plenty of mosquitoes and suitable wildlife too. While this is the first time local transmission has been documented, that doesn’t mean the virus hasn’t circulated in the past, or even that cases may have occurred.

For individuals infected but only suffering mild symptoms, the illness can be easily discounted as nothing more than a mild case of the flu. Without appropriate blood tests, these cases never appear in official statistics. For this reason, many mosquito researchers believe that the number of notified cases across the country is just the tip of the iceberg with many milder infections going diagnosed.

But why in Melbourne now?

It is difficult to know for sure. The two most likely explanations are that either environmental conditions were ideal for mosquitoes and suitable populations of wildlife were present so that the virus was much more active in the local environment than previously. The second explanation is that the virus may have been introduced to the region by a traveller or movement of wildlife. In much the same way Zika virus made its way from SE Asia to South America in the last few years, mosquito-borne viruses move about in people and animals, much less so than mosquitoes themselves (but that isn’t impossible either).

Victoria (as well as inland NSW) is experiencing one of its largest outbreaks of Ross River virus on record following significant flooding of inland regions. With so much activity of the virus in the region, perhaps an infected bird or person travelling to the metropolitan region brought the virus with them. When bitten by local mosquitoes, the virus started circulated among local mosquitoes and wildlife.

Most people infected by Ross River virus are bitten by a mosquito that has previously fed on a kangaroo or wallaby.

Once it’s made its way to metropolitan regions, the virus can be spread from person to person by mosquitoes. Common backyard mosquitoes, especially Aedes notoscriptus, can transmit the virus but as these mosquitoes are not particularly abundant, don’t fly vary far and will just as likely bite animals as humans, they’re unlikely to drive major urban outbreaks of the disease. This mosquito doesn’t pack the same virus-spreading-punch as mosquitoes such as Aedes aegypti that spreads dengue, chikungunya and Zika viruses. Aedes aegypti isn’t in Victoria.

We’re unlikely to see significant spread of Ross River virus across Melbourne but that doesn’t mean Victorians should be complacent. As there is no cure for Ross River virus disease, the best approach is to avoid being infected in the first place. Preventing mosquito bites is the best approach. For my tips and tricks on avoiding mosquito bites see this recent paper in Public Health Research and Practice as well as my article for The Conversation.

Keep an eye on the website of Victoria Health for more information.

 

 

 

 

 

West Aussies versus the local mozzies

This is a special guest post from Dr Abbey Potter, Senior Scientific Officer, Environmental Health Hazards, WA Health. I’m currently mentoring Abbey as part of The Public Health Advocacy Institute of WA (PHAIWA) Mentoring Program. Its been a great experience as we navigate through some of the strategies to raise awareness of mosquito-borne disease and advocate for better approaches to addressing the public health risks associated with mosquitoes.

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Living in WA, we’re all too familiar with the pesky mosquito. We know they bite but what we often don’t consider is that they can transmit serious and sometimes deadly diseases. In fact, a recent survey of locals indicated that knowledge of mosquito-borne disease is pretty limited, particularly among younger adults aged 18-34 years and those living in the Perth Metro. It’s pretty important we’re aware of the risks posed by these pint-sized blood suckers and how you can avoid them… and here’s why!

The Facts

On average, more than 1,000 people will be infected with a mosquito-borne disease in WA every year. Our mossies can transmit Ross River virus, Barmah Forest virus, West Nile virus (Kunjin substrain) and Murray Valley encephalitis virus. All four cause diseases that are debilitating at best, causing weeks to months of symptoms. Murray Valley encephalitis is limited to the north of the State but is so serious it can result in seizures, coma, brain damage and even death.

Forget the bush, most people bitten in their own backyard. West Aussies are all very prone to getting eaten alive while socialising outdoors but if you’re up in the north of the State, you’ve also got a much higher likelihood of being bitten while boating, camping or fishing or working outside, compared to the rest of the state.

And don’t think you’re off the hook when you head off on holidays. A further 500 WA residents return from overseas travel with an exotic mosquito-borne disease every year. Heading to Bali? Beware of dengue, especially young adult males who return home with the illness more than others. There is limited mosquito management in many overseas countries where disease-transmitting mozzies can bite aggressively both indoors and throughout the day. This catches West Aussies off guard, as we are accustomed to mozzies biting outdoors, around dusk and dawn. When you’re in holiday mode it’s likely that you’ll be relaxing, having a couple of drinks and not thinking about applying repellent. Oddly enough, mosquitoes may actually be more attracted to people whose body temperature is higher. This happens naturally when you consume alcohol, so best pull out the repellent before you crack your first beer.

Despite our attractiveness to mosquitoes, we aren’t really aware of the most effective ways to avoid bites or how we can do our bit to reduce breeding in our own backyards. If you live by the mantra Cover Up. Repel. Clean Up you’ll have no problems!

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Western Australia has some amazingly beautiful wetlands but these saltmarshes around Mandurah can produce large populations of nuisance-biting mosquitoes!

Cover Up

If you know you are going to be outdoors when mosquitoes are active, wear loose, long-fitting clothing that is light in colour. Believe it or not, mosquitoes can bite through tight pants as tough as jeans – I’ve witnessed it!

If you’re staying in accommodation that isn’t mosquito-proof, consider bed netting.

Try to keep children indoors when mosquitoes are most active. If exposure can’t be avoided, dress them appropriately and cover their feet with socks and shoes. Pram netting can also be really useful.

Admittedly, it’s not always practical to wear long sleeves during our warm summer nights, so there are going to be times when you need to use repellent. Choose a product that actually works and apply it appropriately so it does the job. Despite our best intentions, this is where we often go wrong. There are a few basic things to cover here, so stick with it!

Ingredient: Science tells us that the best active ingredient for repelling mosquitoes is diethyltoluamide (DEET for short) or picaridin. You need to look for either one of these names on the repellent label under the ‘active constituents’ section.

Unfortunately, natural repellents and anything wearable (e.g. bands, bracelets or patches) have very limited efficacy. Experts don’t recommend you use them and I consider this very wise advice. It only takes a single mosquito bite to become infected and chances are you will receive at least one if you rely solely on a product of this nature. It just isn’t worth the risk.

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Percentage: The next thing to consider is the percentage of the active ingredient. This can range anywhere from 7% to 80% which can make choosing a repellent confusing. Just remember, the higher the percentage, the LONGER the product will remain active for. It doesn’t mean it will repel mosquitoes better.

A repellent containing 16-20% DEET will provide around 4-6 hours of protection, and is a good place to start. Repellents labelled ‘tropical strength’ usually contain greater than 20% DEET – they are useful when you spend longer periods exposed to mosquitoes or if you are heading to a region where dengue, malaria or Zika is problematic. Kids repellents usually contain picaridin or <10% DEET.

Sometimes it can be tricky to work out the percentage of the active ingredient. You can see the Bushmans example below states this clearly, but the other bottles list the ingredient in grams per litre (g/L). No need for complex maths – just divide by 10 and you have the magic number! For example, the RID label below reports the product contains 160g/L of DEET. This would convert to 16% DEET – easy!

You can see a few examples here of effective repellents:

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How to Apply: No doubt we would all prefer if repellents didn’t feel quite so gross on our skin or didn’t smell so bad. Even I have to admit that before I moved into this field, I was guilty of putting just a dab here and a dab there. Unfortunately, this is flawed logic that will only result in you being bitten!

Repellents must be applied correctly to be effective. That means reading the label and applying it evenly to all areas of exposed skin. Remember to reapply the product if you are exposed to mosquitoes for longer than the repellent protects you for. You’ll also have to reapply the repellent after sweaty activity or swimming.

For more information on repellent use in adults and children, click here.

Clean Up

Mosquitoes need water to breed, but only a very small amount. Water commonly collects in a range of things you may find in your backyard including pot plant drip trays, toys, old tyres, trailers and clogged up gutters. Mosquitoes also love breeding in pet water bowls, bird baths and pools if the water is not changed weekly or they are not well maintained. Rain water tanks can also be problematic so place some insect proof meshing over any outlets. When you’re holidaying, cover up or remove anything that may collect water.

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If you need more official info from WA Health about mosquito-borne disease or simple ways to prevent being bitten click here. And if you want to read more about how much West Aussies know (or don’t know) about mossies, check out Abbey’s excellent paper here! Joint the conversation too on Twitter by following Abbey and Cameron.

Do outbreaks of mosquito-borne disease always follow floods?

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Water, water everywhere…and mosquitoes soon to follow. It makes sense that with more water you’ll get more mosquitoes and with more mosquitoes you’ll get more mosquito-borne disease. Right? Well, not always.

With floods hitting parts of inland NSW, health authorities have issued warnings about mosquitoes and mosquito-borne disease.

Western NSW, has been substantially impacted by flooding this month and the region has been declared a natural disaster zone. The Lachlan River at Forbes has reached a level not seen for 25 years. There is a lot of water about. 35,000 mega litres of water has also been released from Wyangala dam resulting in further flooding. There could be more to come as “Superstorm 2016” continues to bring rain to south-east Australia. Evacuations continue.

The flooding has come at a time when the weather in warming up and there are already reports of mosquito numbers increasing. The biggest concern is that once the flood water recede, how long will pools of water remain, have mosquitoes got a “jump start”on the season?

On the other side of the world, Hurricane Matthew is threatening Florida. The Bahamas and Haiti have already been hit and more than 2 million people in the US have been told to evacuate their homes. Flooding is expected.

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Mosquitoes need water

There is no doubt that mosquito populations can increase rapidly following flood. There is even a group of mosquitoes commonly called “floodwater mosquitoes“. The desiccation resistant eggs of these mosquitoes are laying dormant in the cracks and crevices of flood plains, just waiting for the water to arrive. When it floods, the eggs hatch and in about a week or so, swarms of mosquitoes emerge.

For the most part, it isn’t immediately following the flooding, but in the weeks and even months following that can provide the most ideal conditions for mosquitoes. If temperatures aren’t high enough to drive rapid evaporation of ponding (or if additional rainfall keeps them topped up), mosquitoes can start building impressing population abundances. With more mosquitoes, the risk of mosquito-borne disease outbreak can increase.

bom_rainfalljulyseptember2016

Rainfall records provided by the Bureau of Meteorology indicate that over the three months to September 2016, some regions of NT, QLD, NSW and Victoria received some of their highest rainfall on record for the period. (Bureau of Meterology)

A look back to floods and mosquito surveillance

In 2011-2012, QLD, NSW and Victoria saw incredible flooding. For those of us working in the field of mosquito-borne disease, we’re well aware of what that flooding can cause. Our attention was sparked when stories starting coming out from locals about this being the biggest flooding since the 1970s. Why was this important? Following flooding in the 1970s, we saw one of the biggest outbreaks of the potentially fatal Murray Valley encephalitis virus Australia has seen. This outbreak, and the response to the actual and potential health impacts, was essentially the genesis of many mosquito-borne disease surveillance programs across the country.

One of those programs was the NSW Arbovirus Surveillance and Mosquito Monitoring Program. Following the flooding in early 2012, there was a huge jump in mosquito populations in western NSW and one of the largest collections of mosquitoes in the history of the program was recorded with over 18,000 mosquitoes collected! Fortunately, we didn’t see any substantial activity of Muray Valley encephalitis virus but elsewhere in Australia, cases were reported.

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Mosquito-borne disease outbreaks need more than just mosquitoes

There is little doubt you need mosquitoes about for pathogen transmission. However, for many mosquito-borne diseases, the pathogens that cause the illness in people are naturally found in wildlife. Person to person transmission may occur but for pathogens such as West Nile virus, Ross River virus or Murray Valley encephalitis virus, the mosquitoes that inject their virus-filled saliva into people have bitten birds or mammals previously.

The role of wildlife is important to consider as the flooding may influence mosquito populations but they can also influence wildlife. While kangaroos and wallabies may be adversely impacted by floods, flood waters can provide a major boost for waterbirds.

In some instances, as is the case for Murray Valley encephalitis virus, floods provide ideal conditions for both mosquitoes and birds!

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Do floods really cause outbreaks of mosquito-borne disease?

There are few studies that have demonstrated that outbreaks of mosquito-borne disease always occur following floods.

Studies in North America had previously concluded that there wasn’t a direct link between hurricanes and flooding and mosquito-borne disease. But, that doesn’t mean there won’t potentially be a boost in nuisance-biting mosquitoes following flooding.There is often widespread spraying to control these pest mosquito populations.

Interestingly, after Hurricane Katrina hit New Orleans in 2005, there was an increase in mosquito-borne disease with more than a 2-fold increase in West Nile neuroinvasive disease. However, other reports noted no significant increase in cases of either West Nile or St. Louis encephalitis viruses. Surveillance for 6 weeks following the hurricane, authorities found no arboviruses circulating in local mosquito populations. These results highlight that much more than water and mosquitoes are required for outbreaks of disease.

In Australia, a recent review looked at the influence of flooding on cases of Ross River virus disease. They found that the evidence to support a positive association between flooding and RRV outbreaks is largely circumstantial. The trouble in predicting outbreaks of Ross River virus disease is that there can be complex biological, environmental and climatic drivers at work and, irrespective of local flooding, there may be other region-specific issues that either increase or decrease the potential for an outbreak.

What should we expect in Australia as summer approaches?

There is no doubt mosquito repellent will come in handy over the coming months. There are already reports of increased mosquito populations in some parts of the country. While nuisance-biting impacts will be a worry, if mosquito populations further increase following flooding, authorities need to remain mindful of a range of other health risks too.

The good news is that unless higher than normal mosquito populations persist into the warmer months, we may not see major outbreaks of disease. It typically isn’t until November-December that we start to see pathogens circulate more widely among wildlife and mosquitoes. Hopefully, if some hot weather arrives, the flood waters will quickly evaporate and abundant mosquitoes populations won’t continue.

Current outlooks suggest that between now and December 2016, south-eastern regions of Australia are likely to receive above average rainfall. Temperatures, though, are likely to be a little cooler than normal. We’re probably lucky that this cooler weather will keep the really big mosquito population increases that we saw a few years ago at bay.

On balance, we’re expecting plenty of mosquitoes to be about as summer starts, hopefully not “mozziegeddon” but enough to ensure the community should stay aware of the health risks associated with mosquito bites and how best to avoid their bites.

Have you seen mosquitoes about already this season? Join the conversation and tweet some shots of local mosquitoes!

Around the world in a thousand fleas

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The International Congress for Tropical Medicine and Malaria (ICTMM) kicks off in Brisbane, QLD, Australia this week running from 18 through 22 September. This is a big conference and wonderful for local researchers to be showcased to an audience of international scientists from our own backyard in QLD.

I couldn’t make this meeting unfortunately but luckily my wonderful PhD student Andrea Lawrence will be presenting some of our flea research as part of the Australian Society of Parasitology conference that is incorporated into ICTMM this time around.

Andrea has been doing some excellent research during her candidature and you can read some of it here [Evaluation of the bacterial microbiome of two flea species using different DNA isolation techniques provides insights into flea host ecology] and here [Integrated morphological and molecular identification of cat fleas (Ctenocephalides felis) and dog fleas (Ctenocephalides canis) vectoring Rickettsia felis in central Europe].

This week she will be sharing her research into the genetics of global cat flea populations. You can catch Andrea on Tuesday 20 September in the Zoonoses session in M4, 13:00-15:00.

Our abstract is below:

One thousand fleas from fifty countries: global genetic structure and morphometrics of the common cat flea (genus Ctenocephalides) reveals phylogeographic patterns and resolves the generic complex.

Andrea Lawrence, Cameron E. Webb and Jan Šlapeta

School of Life and Environmental Sciences (SoLES), Faculty of Veterinary Science, The University of Sydney, Australia and Department of Medical Entomology, The University of Sydney and Pathology West, ICPMR, Westmead, Australia

The common cat flea and its relatives (genus Ctenocephalides) are considered the most successful ectoparasites on earth. The widespread parasitisation of these insects on mammals closely associated with humans (e.g. dogs and cats) represents significant potential for vector borne disease transmission. Fleas of the genus Ctenocephalides represent a unique model to study the effects of modern human migration and geographic and climatic barriers on parasite diversity and diversification. We have amassed a world-wide collection of Ctenocephalides over a period of 7 years, and analysed over 1000 flea samples from ca. 50 countries representing all continents bar Antarctica. Novel integration of morphology, morphometrics and molecular identification and phylogenetics using a combination of four mitochondrial and nuclear DNA markers, reveals phylogeographic patterns and evolutionary relationships of global cat flea populations. These techniques provide resolution of the long disputed Ctenocephalides generic complex, which has not yet been definitively resolved despite its significance in veterinary and public health. Understanding of contemporary population structure inferred from global phylogeographic analysis has implications for parasite and flea-borne disease management. It is hoped that this work will form the authoritative estimation of the origin of the genus Ctenocephalides and the subsequent species evolution and migratory radiation.

Keep an eye on the official conference hashtag [#ICTMM2016] and why not follow Andrea on Twitter for more!

The lead image on this article is modified from Andrea’s paper, “High phylogenetic diversity of the cat flea (Ctenocephalides felis) at two mitochondrial DNA markers

 

 

 

 

 

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?

 

 

Beware the thick skinned bed bugs (they’re beating our bug sprays)

Bed_bug_Leg_Lilly

Think you’re got thick skin? You may be able to brush off the odd insult but for bed bugs, their thick skin can ward off fatal doses of insecticides! This is just one way they’re beating our commonly used bug sprays.

The resurgence of bed bugs over the past couple of decades has been great fuel for media and pest control companies alike. From Paris to London and New York to Sydney, infestations in all forms of accommodation has made headlines.

Eradicating an infestation of bed bugs can be tricky, tricky and expensive. While control within the hospitality industry is improving, the impacts of bed bugs are now being felt in lower socioeconomic groups in the community. There are often financial barriers to effectively controlling infestations and controlling infestations is not getting any easier.

Working out why bed bugs are hard to kill

David Lilly is currently a postgraduate student in our lab undertaking his PhD with the University of Sydney. He has been doing some great work and its wonderful as a supervisor to see him starting to publish some of his research as he approaches the end of his candidature.

We’ve already published some research on bed bugs and insecticide resistance and the role of metabolic detoxification in driving this resistance (you can read about that work via at Entomology Today). However, some of the most exciting research has just been published and indicates that “thicker skinned” bed bugs are more resistant to pyrethroid insecticides.

It is one thing to demonstrate insecticide resistance in a pest but understanding why that resistance occurs is critical if we’re to develop more effective strategies to control bed bugs.

This project was inspired by a study that demonstrated that mosquitoes resistant to insecticides had thicker cuticle. Could the same phenomenon occur in bed bugs?

Working with the Australian Centre for Microscopy & Microanalysis at The University of Sydney, we were able to capture images of cross-sections of legs from resistant and susceptible strains of bed bugs. Measuring the cuticle thickness at various points and comparing those between the two strains of bed bugs allowed an assessment of changes in cuticle.

Those bed bugs resistant to insecticides had thicker cuticle. In fact, the cuticle of the resistant bed bugs was around 15% thicker. Thicker the cuticle, the tougher it is for insecticides to penetrate.

Given human’s propensity to use insecticides, it is little wonder our most loathsome pests, such as mosquitoes and bed bugs, are developing resistance. While there really aren’t many other options available to control bed bugs, insecticides will remain part of our pest control tool kit. Alternative strategies are always being considered but while insecticides remain, we need to be mindful of the development of resistance and ways we can slow (or overcome) that process.

Bed bug’s thick skins grab the media’s attention

ABC24_BedbUgs_Lilly_17April2016

The research has already received international media coverage thanks to the fantastic team at University of Sydney Media and Communications team. A quick “google news” search turns up over 70 news items reporting on the paper! You can catch up with coverage at Popular Science (Australia), Wired, USA Today, Daily Mail, Sydney Morning Herald, BBC, Newsweek, Gizmodo and Mirror.

The abstract for our paper is below:

Thickening of the integument as a mechanism of resistance to insecticides is a well recognised phenomenon in the insect world and, in recent times, has been found in insects exhibiting pyrethroid-resistance. Resistance to pyrethroid insecticides in the common bed bug, Cimex lectularius L., is widespread and has been frequently inferred as a reason for the pest’s resurgence. Overexpression of cuticle depositing proteins has been demonstrated in pyrethroid-resistant bed bugs although, to date, no morphological analysis of the cuticle has been undertaken in order to confirm a phenotypic link. This paper describes examination of the cuticle thickness of a highly pyrethroid-resistant field strain collected in Sydney, Australia, in response to time-to-knockdown upon forced exposure to a pyrethroid insecticide. Mean cuticle thickness was positively correlated to time-to-knockdown, with significant differences observed between bugs knocked-down at 2 hours, 4 hours, and those still unaffected at 24 hours. Further analysis also demonstrated that the 24 hours survivors possessed a statistically significantly thicker cuticle when compared to a pyrethroid-susceptible strain of C. lectularius. This study demonstrates that cuticle thickening is present within a pyrethroid-resistant strain of C. lectularius and that, even within a stable resistant strain, cuticle thickness will vary according to time-to-knockdown upon exposure to an insecticide. This response should thus be considered in future studies on the cuticle of insecticide-resistant bed bugs and, potentially, other insects.

The full citation is: Lilly DG, Latham SL, Webb CE, Doggett SL (2016) Cuticle Thickening in a Pyrethroid-Resistant Strain of the Common Bed Bug, Cimex lectularius L. (Hemiptera: Cimicidae). PLoS ONE 11(4): e0153302. doi:10.1371/journal.pone.0153302

Download the paper for free directly from PLoS ONE!

Oh, and if you’re worried about picking up bed bugs on your next holiday, here are some tips!

 

Lessons from the dengue outbreak in Hawaii

Hawaii_1There are millions of cases of mosquito-borne disease world wide every year so why should we care about a few dozen dengue cases in Hawaii?

Hawaii is no stranger to dengue. There have been outbreaks first dating back to the 1840s. Travellers, including returning residents, are diagnosed with dengue routinely. However, this is the first outbreak of locally-acquired infection since 2011.

As of 17 November 2015, Hawaii Department of Health reports there have been approximately 65 locally acquired cases on Hawaii Island (aka Big Island) including both residents and visitors. Why has this happened and what lessons can be learned from the outbreak?

[update: As of 29 January 2016, there have been 242 confirmed cases of locally acquired dengue.]

Hawaii provides a fascinating example of the implications (as well as study of spread) of exotic mosquito invasions. With no endemic mosquito species, the pest species found in the Hawaiian islands have all been introduced from elsewhere.

The first mosquito to make it to Hawaii was Culex quinquefasciatus. It is thought to have arrived on a boat from Mexico in the mid 1820s. Interestingly, with no native mosquitoes in Hawaii, there was no word to describe them so they were initially referred to as “singing flies”.

In recent years, it has been the role of Culex quinquefasciatus in the spread of avian malaria that’s been grabbing the headlines. However, in the last few weeks, it has been Aedes aegypti and Aedes albopictus playing a role in the local spread of dengue virus in the spotlight. These two container-inhabiting mosquitoes are the key vectors of dengue viruses (as well as chikungunya, yellow fever and zika viruses) internationally. They’re driving the outbreak now as they have in the past.

There was an outbreak of dengue in 2001 with a total of 122 locally acquired cases. Cases were reported from Maui, Oahu and Kauai with the outbreak thought to have been triggered by travellers from French Polynesia where there was a major outbreak underway at the time. Between 1944 and 2001, the only cases of dengue reported in Hawaii were imported with travelers. Firstly, this highlights how important it is to understand the pathways of infected people, this can help guide assessments of risk.

This was also done from the potential introduction of West Nile virus into Hawaii. Analysing the movement of travelers from regions of endemic mosquito-borne disease has also been used to assess the risk of chikungunya virus introduction to North America.

It was believed that Aedes albopictus played an important role in this 2001 outbreak. This mosquito was not a significant presence in Hawaii until the 1940s. More importantly, Aedes albopictus is not exclusively found in water-holding containers in urban area. Unlike the other vector of dengue viruses, Aedes aegypti, Aedes albopictus is also found in bushland habitats. This makes mosquito control just a little more difficult when authorities need to look beyond the backyard.

Previous dengue outbreaks in Hawaii were thought to have been driven by Aedes aegypti. These outbreaks were significant with an estimated 30,000 cases in the early 1900s followed by approximately 1,500 cases around Honolulu in the period 1943-1944. While not necessarily easy to manage, outbreaks of dengue driven primarily by Aedes aegypti can be strategically targeted by residual insecticide treatments and community education. That education focuses on raising awareness of the public health risks associated with mosquitoes and the need to remove opportunities for mosquitoes to be breeding around dwellings. This model is essentially what is in place to address occasional outbreaks of dengue in Far North Queensland, Australia.

The current outbreak has raised concern in the community. Shelves of stores have been emptied of insecticides and repellents. Community meetings have been held by local authorities to provide information on dengue and address concerns on the Big Island. You can watch some of the meetings here. You can see some of the health promotion (aka “Fight the Bite”) flyers here.

Community engagement is important. An indirect impact of this engagement though is that the total number of confirmed cases of dengue on the Big Island is likely to rise over coming weeks. Not necessarily due to new cases but a greater likelihood that older cases will now be diagnosed through blood tests. Even those who may be suffering a mild illness are likely to be tested for infection and may end up in official statistics.

This dengue outbreak is a reminder to authorities across the world that where suitable mosquitoes are present, a risk of mosquito-borne disease outbreak is possible. The mosquitoes provide the tinder and it only takes the spark of an infected traveler to ignite an outbreak. We saw this in 2014 with the first outbreak of dengue in Japan for 70 years. We’ve seen it this year with local transmission of chikungunya virus in Spain and other outbreaks across Europe.

For Australian authorities, ensuring there are strategic responses in place to address the risk of exotic mosquito introduction, as well as outbreaks of disease, is critical. What this outbreak in Hawaii reminds us is that if Aedes albopictus becomes established in our major cities, it is only a matter of time before we see local outbreaks of dengue, chikungunya or Zika viruses.

What is it like if a loved one comes down with dengue? Check out the channel of YouTube stars Charles Trippy and Allie Wesenberg as they document their brush with mosquito-borne disease during this outbreak.

[Update: Implications for potential Zika virus spread] The recent spread of Zika virus in the Americas has raise concerns by health authorities. In particular, the spread of the virus to North America. What about Hawaii? There has already been one case of microcephaly in Hawaii with a baby born on Oahu to a mother who had been residing in Brazil. The pregnant women was infected in South America, not Hawaii. However, authorities should be on alert as travellers from the Americas, or the Pacific, have the potential to introduce the virus and the mosquitoes currently present in Hawaii spreading dengue viruses are the same that spread Zika virus.