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.

fightthebite_wahealth_flyer

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!

mandurah_sep2014

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.

mosquito_repellent_wristband_october2015

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:

repellents_potterpaper

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.

**

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.

Could a podcast stop mosquito bites?

podcasting_mozziebites

This week I’m attending OzPod 2016: the Australian Podcast Conference, a workshop at the ABC, Ultimo. Celebrating International Podcast Day, the workshop brings together podcasters for “an event for the expanding podcast industry to escape the studio or office and meet with peers to share experiences, information, insights and ideas around audience acquisition and retention, new technologies, the rise of the podcast in traditional media, monetizing and of course the fine art of storytelling.”

 So, why am I going? I don’t even have a podcast!

I may not have a podcast now but I hope to start playing around with the platform soon as a complement to my other efforts to spread the word on science communication and public health awareness.

I’ve been thinking about kicking off a podcast for a while but have been a little reluctant due to time commitments. More importantly, I’ve also wanted to have a clear idea of what exactly I want to do.

In a previous life, I co-hosted a radio show on FBI Radio (during their test broadcast days) with my wife called “Good Morning Gidget”. It was a Saturday morning show of surf music and interviews with professionals involved in a wide range of coastal-based activities, from marine biologists to surf shop owners. Despite the early start on a Saturday morning, it was a load of fun. I’d also worked behind the scenes producing a couple of music shows. If I had more time, I really would have liked to pursue more work with community radio.

Perhaps podcasting will be the backup plan.

flashforward_swatting

It’s great to listen back to packaged interviews with radio, like the Health Report (I’m talking zika virus) but I was also lucky enough to have a chance to contribute to a few podcasts this year. I spoke with Science On Top about the outbreak of Zika virus and the implications it has for Australia, Flash Forward on what will happen if we eradicate mosquitoes from the planet and ArthroPod on what its like to study mosquitoes for a living!

All these were a lot of fun and were really motivating for me to want to get started with podcasting myself.

I feel like my experience with sound recording and ongoing engagement with media provides a solid background in most of the technical skills I need to get started. I’m hoping I’ll leave the OzPod 2016 conference with a few more tips on story telling and structuring a podcast too.

What I’ve been struggling with is format. I like the conversational nature of most podcasts but as I’ll probably be doing everything myself, perhaps a more structured and edited podcast is the go?

There are very few podcasts I listen to that are built around a one-person show. I’m not sure I could pull it off. Does anyone really want to listen to me ramble on for 20 mins about mosquitoes? 40minutes?

Sometime over the coming summer I hope to launch a short series of podcasts covering some of the basics of mosquito biology and how that relates to the ways we protect ourselves and our families from mosquito bites and mosquito-borne disease. I want to share my fascination with mosquitoes and explore some of the gaps in our understanding of mosquitoes, particularly their role in our local environment. 

Hopefully I can recruit some of my colleagues from around Australia for a chat too so we can share a little about the science behind our public health messages and what life is like to be chasing mosquitoes around swamps all summer

Sound like a good idea? Join the conversation on Twitter and let me know what you think, would you listen to a podcast about Australian mosquitoes?

 

 

 

 

 

 

Social media and blood suckers showcased at the International Congress of Entomology

instagram_wetlands_webb

Digital technology is changing a lot about how we undertake entomological research and communicate the results of that research to the community and policy makers.

This week in Orlando, Florida, is the International Congress of Entomology (ICE). A huge gathering of entomologists from around the world. While it was a great pleasure to be invited to participate, I couldn’t get over there this time.

I will, however, have a chance to present my work in the Symposium “Entomology in the Digital Age”  Friday, September 30, 2016 (01:30 PM – 04:45 PM), Convention Centre Room W222 A.

In the presentation I’ll share some of the reasoning behind my use of social media to engage the community with both entomological research and public health communication. Most importantly, it will focus on some of the metrics I’ve recorded alongside my use of social media, maintaining a blog of research and writing for outlets such as The Conversation.

I’ve written about my use of social media and how it can help extend the reach of public health messages and presented on the topic alongside a range of great speakers at the 2014 Entomological Society of America meeting in Portland.

This time around, technology is playing an even more direct role in my presentation! I’ve pre-recorded my presentation and it will be shown to the audience on the day among other presentations. I’ll also be checking into the session to answer questions. Despite the fact I’ll need to be up around 1:30am due to time differences, it should be fun.

See the abstract below…

Taking entomological research from the swamps to the suburbs with social media

Cameron E Webb

Connecting scientists and the community is critical. This is particularly the case for medical entomologists working in the field of mosquito-borne disease where the translation of entomological research into improved public health outcomes is a priority. While traditional media has been the mainstay of public health communications by local authorities, social media provides 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. doi: 10.1603/ICE.2016.94611


If you’re at ICE, you can also catch up with my PhD student David Lilly who’ll be presenting our research into the development of insecticide resistance in bed bugs as part of the symposium “New Insights into Biology, Resistance Mechanisms, and the Management of the Modern Bed Bug” Friday, September 30, 2016, 01:30 PM – 04:45 PM, Convention Center, West Hall F4 (WF4).

Novel insecticide resistant mechanisms in the common bed bug, Cimex lectularius

David Lilly, Cameron E Webb and Stephen Doggett

Introduction: Research on field strains of Cimex lectularius from Australia has identified widespread resistance to pyrethroid insecticides, but variability in the magnitude expressed. To determine if differences in resistance mechanisms exist, collected strains were examined for the presence of metabolic detoxification and/or cuticle thickening. Methods: The presence and relative contribution of detoxifying esterases or cytochrome P450 monooxygenases were assessed. Bed bugs collected from Parramatta (NSW), Melbourne (VIC) – 2 strains, ‘No.2’ and ‘No.4’, and Alice Springs (NT) were exposed in topical bioassays employing deltamethrin and two pyrethroid synergists: piperonyl butoxide (PBO) and EN16/5-1. PBO inhibits both monooxygenases and esterases, whereas EN16/5-1 will inhibit esterases only. Thus in a comparative bioassay, the results can infer the dominant enzyme system. The Parramatta strain was then selected to study the potential presence of cuticle thickening. Nine-day-old male bed bugs were exposed to filter papers treated with the highest label rate of Demand Insecticide®(200mL/10L of 25g/L lambda-cyhalothrin) and were grouped according to time-to-knockdown (< 2 hours, ≥ 4 hours, and survivors at 24 hours). Measurements of mean cuticle thickness at the transverse midpoint of the second leg tarsus were taken under electron microscope. Results/Conclusion: All strains possessed resistance that was inhibited by the synergists, with the Parramatta and Melbourne No.2 indicating esterase-dominance, and Alice Springs and Melbourne No.4 indicating cytochrome P450 monooxygenase-dominance. Cuticular measurements demonstrated that bed bugs surviving deltamethrin exposure had significantly thicker cuticles, denoting a novel form of resistance in these insects. doi: 10.1603/ICE.2016.92553

 

You can also see Stephen Doggett (co-author and photographer of A Guide to Mosquitoes of Australia) speaking on photographing mosquitoes to in the symposium “Insect Photography Symposium: Bringing the Small to the World.


You can join the conversation on Twitter and keep an eye on all the fun in Orlando by keeping an eye on the tweet stream!

 

How to beat the bite of backyard mosquitoes

dude_sandpit_30032014Summer is here and you’ll want to know how to spend time in the backyard without a barrage of bites from pesky mosquitoes!

There is little doubt mosquitoes are a nuisance but in some parts of Australia but they can also pose a health risk. Around 5,000 people a year are infected with Ross River virus. In fact, 2015 saw the biggest outbreak of mosquito-borne Ross River virus disease ever recorded in Australia.

I recently shared ten tips on keeping free of mosquito bites with the University of Sydney that proved popular so now here are five top tips (with a bit more detail) to help reduce the risk of mosquito bites and get the most out of your backyard this summer!

Water water everywhere, just what mozzies love

Don’t let mosquitoes find a home around your home.

The immature stages of mosquitoes (commonly known as wrigglers) are found in free-standing water so drain, tip out or cover any water holding containers. These can range from buckets and discarded tyres to children’s toys and slumped tarpaulins covering boats or trailers.

Flush out your bird baths with a hose once a week (you can also scrub it with wire brush to dislodge any mosquito eggs). Mosquitoes can even find a home in your pet’s water bowl so empty before refilling at least once a week.

Can you see a puddle or pool of water? There are probably mosquitoes in there, or dozens of eggs waiting to hatch.

Pot plant saucers (particularly “self watering” pots) are great places for mosquitoes. If you fill saucers with sand, the moisture will be trapped but there won’t be any “free standing” water for mosquitoes to use. Good for the plants, bad for mosquitoes.

Sometimes the problem comes from above. Check your roof gutters, when they get blocked with leaves and water is trapped it provides habitat for mosquitoes. Same goes for courtyard drains, make sure you clean out soil, sand and other debris that might trap pools of water.

Make sure you keep your swimming pool chlorinated. Neglected swimming pools can harbour mosquitoes, especially mostly empty in-ground pools that partially fill following rainfall.

Webb_bucketsofrainwater

It may seem like a good idea to store water around the home to help keep plants going during a long hot summer but any water, from a full rainwater tank to a few drops in the base of a pot plant saucer, can make a great home for mosquitoes!

Spray with care (if you really need to)

A range of products is available that will help control mosquitoes. It is important to ensure that any product used is registered with the Australian Pesticides and Veterinary Medicines Authority (APVMA). The APVMA test products for their effectiveness and safety and it is critical that the instructions on the insecticide label are followed.

The insect growth regulator methoprene (NoMoz) and the monomolecular film (Aquatain) can both be used to stop mosquitoes emerging from backyard habitats. A few pellets of methoprene or a few drops of monomolecular film into water can be enough to provide a month or so of mosquito control. It was once common practice to put a teaspoon of kerosene into rainwater tanks (the kerosene floats on the surface of the water, drowning mosquito wrigglers), now monomolecular films can be used. Keep in mind though, if your rainwater tank is properly screened, you don’t need to worry about putting anything inside.

For mosquitoes flying in from beyond the backyard, sometimes you need to use insecticides. Insecticide sprays generally fall into one of two categories. “Knockdown” sprays are designed to kill flying insects while they’re buzzing about. While they’ll certainly kill mosquitoes, mosquitoes are far less likely to be randomly flying about in the backyard. They’re usually a little more sneaky than that. A better option will be “surface sprays” that provide some residual control and kill the mozzies where they hide out.

Residual insecticides (typically containing synthetic pyrethroids and often marketed as “surface sprays”) can be applied to cool and shaded areas. The most effective places will be under outdoor furniture, the shaded sides of buildings, verandas or within vegetation. While these products are safe for people and pets, they are likely to impact non-target insects too (e.g. bees, butterflies, beetles) so should be employed judiciously, especially if spraying on plants. Never spray them into or around ponds as these insecticides can be toxic to fish. Always check the label of the insecticide for directions.

I once asked a local resident if this type of spraying worked in reducing mosquito numbers around the home. “Yeah, it killed everything” they replied. We really don’t want to be killing everything so please be careful when using these products.

vintage_bugspray_

Vintage insecticide advertising (Source: Envisioning the American Dream)

Topical mosquito repellents will remain the first line of defence for many when mosquitoes are out in force. Products that contain DEET (diethyltoluamide) or picaridin will provide the longest lasting protection but make sure they’re applied correctly. You’ll need a thin coverage of all exposed skin. A dab “here and there” won’t be enough. Plant-based products (e.g. tee tree oil) will provide some protection but will generally need to be applied more frequently than the other repellents to ensure long lasting mosquito bite protection.

Burning coils and switching on zappers

The smell of mosquito coils is up there with the smell of sunscreen and BBQs as a reminder of summer. Mosquito coils and sticks are good at reducing the number of mosquito bites but they’re unlikely to stop them all. A recent study found little evidence that burning mosquito coils prevents malaria so don’t expect all biting mosquitoes to stop once you light up a coil. Make sure you use coils or sticks that contain insecticide (e.g. pyrethroid) and not just botanical extracts (e.g. citronella) as the insecticides will actually kill some mosquitoes.

Never sleep in an enclosed room with a mosquito coil burning. Seriously, don’t keep a mosquito coil burning overnight in your bedroom.

There is a range of “smokeless” ways to beat mosquitoes too. These are either plug-in or butane powered units that heat insecticide impregnated pads, or reservoirs of liquid. Most of these types of units are designed for indoor use but they’ll work just as well in sheltered balconies or courtyards too. Like the insecticide impregnated coils and sticks, these products provide the best bite protection but without the smoke.

You can also forget about the various types of mosquito traps on the market. Some may catch mosquitoes but never enough to stop bites in the backyard. Electrocuting traps and those with UV lights are generally ineffective at catching mosquitoes, you’ll catch many more non-biting flies, moths and beetle than mosquitoes.

birdhouse

Encourage the creatures that will eat mosquitoes

Mosquitoes are food for fish, frogs, birds and bats. Can they help keep mosquito numbers down?

Fish eat mosquito wrigglers so release some (native fish preferably) into your ornamental ponds. Best not release “mosquitofish” (aka the plague minnow, Gambusia holbrooki) as these will chomp through more than just mozzies (say good bye to native fish and tadpoles!). Contact your local council who can provide some advice on what fish may be best suited to your local area. If you’ve got frogs about, tadpoles won’t munch through many wrigglers, but having frogs about is reward enough anyway!

Many claim that encouraging birds or bats to move in around the house will help reduce mosquitoes. A garden of native shrubs and ground covers will provide a home for small insect-eating birds so at least some local animals will be snacking on mozzies. But don’t buy bird houses and bat boxes expecting all the bites to disappear. Although birds and bats do eat mosquitoes, they don’t eat anywhere near enough to reduce nuisance biting. Encourage these creatures because they’re nice to have around, not because they’ll provide pest control.

There are some mosquitoes whose wrigglers will actually eat the wrigglers of other mosquitoes. The news gets even better because these mosquitoes (Toxorhynchites speciosus) don’t even bite (they’re also film stars)! Unfortunately, there will never be enough of them to eat enough mosquitoes to make a difference having them around (as well as other mosquito eating arthropods such as dragonflies, spiders, beetles and damselflies) can only help, even if it is just a little bit.

mosquitorepellentplants

Mosquito repellent plants aren’t repellent

Sounds like a dream that you could plant something in the garden that would “naturally” keep mosquitoes away. Problem is, none of the plants promoted as “mosquito repelling” provide any substantial protection.

Experiments in Africa found that some potted plants repelled around 30-40% of the mosquitoes. I’m somewhat sceptical of that success. Whenever I’ve tested spatial repellents, especially those containing plant extracts that are actively released in one way or another, I rarely get that success. Whole plants? I’m not so sure.

If you check out your local nursery, you may find a plant called “Mozzie Blocker” for sale. This plant is the Lemon Scented Gum (Leptospermum liversidgei). While the extracts from these types of trees (Leptospermum and Melaleuca species) have been shown to repel some mosquitoes, there is no evidence that the whole plant will reduce mosquito bites. It is worth remembering that these plants populate coastal swamp forests and I know from experience that these are some of the most intense places for biting mosquitoes you can find!

In summary, the nuisance caused by local mosquitoes will often be determined by the environment around your home as much as those in it but there are still things you can do to reduce their bites. Most important of all is ensuring you’re not creating opportunities for mosquitoes to breed and hang out in your backyard!

What’s your favourite way to beat the bite of backyard mosquitoes? Join the conversation in Twitter!

Want to learn more about the amazing world of Australian mosquitoes? Check out “A Field Guide to Mosquitoes of Australia” out now through CSIRO Publishing. Over 200 pages containing a pictorial guide to almost 100 different mosquitoes along with tips on beating their bite and protecting your family from the health risks of mosquitoes. You can order online or through your favourite local bookstore or online retailer.

 

 

 

 

Perfume won’t protect you from mosquito bites

VictorissecretThe headlines have been awash with claims that a popular perfume may repel as many mosquitoes as those regularly recommended by health authorities. Could it be true?

In short, no. There is little surprise that the results of this recently published study in the Journal of Insect Science has attracted so much attention. Everyone loves the idea that some unexpected substance could be used as a mosquito repellent. Even better if it performs as well, or even better, than those such as DEET or picaridin that are widely recommended by health authorities.

The scientists tested a range of commercial insect repellents. Three formulations of DEET based repellent, an oil of lemon eucalyptus (aka PMD) based repellent, three botanical-based repellents, a mosquito repellent patch (Vitamin B), a product not specifically designed as a repellent but often quoted as being effective (Avon skin so soft) and the perfume. Why include the perfume at all?

The logic behind including the perfume was a good one. It is often said that floral perfumes and other cosmetics attract mosquitoes. I’ve never thought this is actually the case. I mean, there is stronger evidence that mosquitoes re attracted to smelly foot bacteria than pleasant smelling cosmetics! I always suspected that the idea comes from the fact the mosquitoes (mostly the non-biting males) will feed on plant sugars. However, it was worth including in this study. Always good to gather some quantitative evidence on the response of blood-seeking mosquitoes. It could be a good opportunity to bust (or perhaps confirm) some urban myths.

I’ve written before about how you can test mosquito repellents. While the “arm-in-cage” methodology typically provides the best indication of how a mosquito repellent will perform, there are other methods commonly employed. In this case, the researchers used a “Y-tube” setup. This system basically allows mosquitoes to make a choice as to whether they preferentially fly towards one or the other ends of the tube. If you insert a hand treated with a substance into one end and another untreated hand as a control into the other, it is possible to measure the overall repellent effect by tracking the movement of mosquitoes.

Firstly, it is interested to note that the researchers found that some mosquitoes were attracted to the hand treated with DEET. If I was conducting an “arm in cage” test. I would be very surprised if I had any mosquitoes biting a DEET-treated arm within 2h of application. In one study, I found an approximately 7% DEET-based repellent stopped bites for a little under 2h. It makes me wonder how many mosquitoes may fly up to tube towards the treated hand but, given the chance, would actually bite the hand?

Fewer mosquitoes were attracted to hands treated with oil of lemon eucalyptus, not surprising either given this product is regularly recommended as an effective repellent by health authorities.

The testing of the perfume provided the headline grabbing results! For the first couple of hours, there wasn’t much difference in the proportion of mosquitoes repelled by the perfume compared to the other repellents. Why? It may be related to the strength of the odour overpowering the sensory organs of the mosquito. I think this is how some strongly smelling essential oils can provide some protection. It masks the normal chemical cocktails of smells on our skin that attracts mosquitoes.

We all know how overpowering the smell of some cosmetics can be. In this case of this experiment, a relatively high dose of the products as used. The authors make note of this too when they state “It must be noted that the concentration of perfume we used in this test was rather high and that lower concentrations of the same fragrance might have different effects.”

Could this perfume be used as a repellent?

Studies like this provide some fun headlines but they can be misleading to the public. What “works” for a relatively short period in a small laboratory based study does not necessarily stand up the practicalities of real life.

Notwithstanding the expense (the perfume is about AUS$80 for 100ml compared to less than AUS$10 for about the same amount of DEET-based repellent) I must admit that for some of these products, the smell can be so overpowering that applying them to large areas of skin would probably be more unpleasant than the bites of mosquitoes!

When trying to help the public choose and use mosquito repellents more effectively, it is critical that health authorities stick to products that are currently registered for use as a mosquito repellent and that have been demonstrated to provide suitable protection from biting mosquitoes over extended periods of time.

Perhaps the most important finding of the paper is not that the perfume repelled some mosquitoes but that patches infused with Vitamin B provide absolutely no protection from mosquitoes. This is one urban myth that never really seems to go away!

We also know that Victoria’s Secret perfume doesn’t stop bed bugs invading lingerie stores!

[The image used at the top of this piece is taken from here.]

Are mosquito coils making us sick?

coilWe burn them to beat the bite of mosquitoes but could they actually be making us sick? Is breathing the smoke from a smouldering mosquito coil really the same as smoking a pack of cigarettes?

In summary, should I use mosquito coils to protect my family from mosquito bites?

  • Only use commercial products that have been registered by local authorities
  • Products that contain pyrethroids will provide better protection from mosquitoes than those that contain only botanical extracts
  • The byproducts of combustion, not insecticides, associated with mosquito coils may pose a health risk in some circumstances
  • Best to limit use of coils to outdoor or well ventilated indoor areas
  • Don’t sleep next to a smouldering mosquito coil
  • Consider plug-in “smokeless” mosquito repellent devices
  • Sleeping under a mosquito net is the best non-chemical approach to overnight mosquito bite prevention
The Saltmarsh Mosquito (Aedes vigilax) (Photo: Stephen Doggett)

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

Here is the background…

For centuries we’ve burnt substances, particularly aromatic plants, to keep mosquitoes away. The clouds of smelly smoke can often ward off the swarms of blood sucking mosquitoes.

The use of pyrethrum in incense gained popularity and became common practice in Asia but it wasn’t until the early 1900s that the mosquito coil was born thanks to Japanese entrepreneurs Eiichiro and Yuki Ueyama and their katori senkō (mosquito-killing incense).

Modern mosquito coils, mostly containing the pyrethroid insecticides, are an almost permanent fixture at camp sites and backyard during summer. Millions of families across the tropics use them as their primary source of mosquito-borne disease prevention. They’re cheap and generally effective. We burn them to reduce the risks of mosquito-borne disease but could they actually be making us sick?

Health concerns of mosquito coils

There is growing concern about the adverse health impacts associated with the burning of mosquito coils and sticks indoors. A recently presentation to the 48th National Conference of Indian College of Allergy, Asthma and Applied Immunology has again raised the issue of potential health impacts associated with mosquito coils with media coverage given to Dr Sundeep Salvi in the lead up to the conference. He is quoted as saying “Burning one mosquito coil in a closed room amounts to smoking roughly 100 cigarettes”. The key point in Dr Salvi’s comment is “closed room”.

When assessing the real risks posed by mosquito coils, it is important to consider not just what is released by these smouldering products but actual likelihood it poses a serious health risk. How do you balance these potential health risks of burning coils with those posed by the bite of infected mosquitoes?

Total daily rainfall recorded at Sydney Olympic Park (Data source Bureau of Meteorology)

Do you really need to weigh up the risks of breathing in smoke from a mosquito coil with the risks of mosquito bites? (Image: Joel Sartore, National Geographic)

Who checks the safety of mosquito coils?

In Australia, all substances that purport to kill or repel mosquitoes must be registered by the Australian Pesticides and Veterinary Medicines Authority (APVMA). Similar regulatory authorities exist in other jurisdictions.

Mosquito repellents, whether they’re topical or spatial or whether they contain “chemical” or “natural” substances will need to be tested for efficacy and safety. Check the packaging for a registration number. There are dozens of different variations on “mosquito coils” including sticks, coils, candles and a variety of “plug in” devices. You’ll find the shelves of the local supermarket, camping and hardware store fully stocked almost all year round!

Despite the wide range of products available, the active ingredients (that is the mosquito repelling or killing products) don’t vary too much. There are either synthetic pyrethroids or botanical extracts (e.g. citronella oil, eucalytpus oil). You may be surprised to know that some contain a combination of the two. Just because “citronella” is written in bold on the packaging, it may still contain one of the synthetic pyrethroids. Check the label.

repellentrackDoes burning mosquito coils really make us sick?

A study of mosquito coils sold in the U.S. and found that some mosquito coils contain octachlorodipropyl ether (s-2) that, during the smouldering of the coils, produces an extremely potent lung carcinogen as a byproduct called (bis(chloromethyl)ether (BCME)). Fortunately, s-2 is banned in many countries. It is no longer used commercially in the U.S. and prompted by reports of the risks associated with mosquito coils, Hong Kong authorities released a statement in 2005 regarding the recall of mosquito coils containing s-2.

It is not listed as an active ingredient in mosquito coils registered for use in Australia. Given that in most circumstances, particularly in Australia, mosquito coils don’t contain s-2, it is the particulate matter that is of greatest concern.

An often quoted study published in 2003 titled “Mosquito coil emissions and health implications” analysed the components of commercially available mosquito coils from China and Malaysia and found that burning mosquito coils in an enclosed room may pose “significant acute and chronic health risks” with the fine and ultra fine particulate matter released from a single mosquito coil equaling that of up to 137 cigarettes!

In addition, they found that emission of formaldehyde (a by product of the combustion process) from burning one coil can be as high as that released from burning 51 cigarettes.

Doesn’t sound too good does it? The combustion of the coil itself is the main concern, not the insecticides used.

More recent studies have indicated that changing the base materials used in mosquito coils (i.e. switching to charcoal from other organic material) can reduce the volume of particulate matter substantially. Would these “smokeless” mosquitoes be more “healthy”? Probably.

Does what happens in the lab stays in the lab?

Billions of mosquito coils are sold across Asia every year. Millions of families use them as their primary mosquito bite prevention strategy. Why aren’t we seeing more substantial health impacts in local communities?

It is worth noting that two papers published in 2006 investigated the different methods used to assess the health risks associated with burning mosquito coils. The researchers tested different methods to expose laboratory rats to particulate matter from mosquito coils. They firstly reported that “protocols devised evaluate and assess the acute inhalation toxicity of mosquito coil smoke demonstrating that the nose-only mode of exposure of rats to the smoke of mosquito coils is suitable to assess the toxic potency of different coils.

The nose-only mode has clear advantages over the whole-body exposure mode.” Then, using the “nose-only” exposure method that they proposed, the researchers concluded that “overnight exposure to the smoke from burning mosquito coils (manufactured in Indonesia) is unlikely to be associated with any unreasonable health risk.” This is a noteworthy conclusion given that the level of exposure to those rats (6 h a day, 5 days a week for 13 weeks) was substantial.

What about “smokeless” mosquito coils?

There is a paucity of studies investigating the potential human health impacts of “smokeless” mosquito repellents. The few studies that do exist are inconclusive or use animals to test health impacts under conditions unlikely to occur in most circumstances.

A 2005 review of pyrethroid poisoning reported “Despite their extensive world-wide use, there are relatively few reports of human pyrethroid poisoning. Less than ten deaths have been reported from ingestion or following occupational exposure. Occupationally, the main route of pyrethroid absorption is through the skin. Inhalation is much less important but increases when pyrethroids are used in confined spaces.” Again, this highlights the critical issue here, exposure to insecticides in confined and/or enclosed situations.

It is worth remembering that pyrethroids are over 2000 times more toxic to insects than mammals. That means that the concentrations used to kill insects are unlikely to have adverse health impacts on humans, particularly if commercial formulations are used as recommended. Given the billions of people who use mosquito coils to prevent mosquito bites, perhaps the more important question to ask is, does burning mosquito coils actually prevent mosquito-borne disease? Perhaps that is a discussion for another time….

sp-breweries-mozzie-boxPerhaps one of the most interesting ideas this year was the “mosquito repellent beer carton”. More marketing than public health initiative but I like the idea. The carton is infused with citronella so that when you’re sitting about the campfire enjoying a few beers, you can toss bits of the carton into the fire and keep mosquitoes away. It is unlikely many mosquitoes will be actively repelled. However, I do like the idea of using the beer carton as an opportunity to raise awareness of mosquito-borne disease.

Perhaps it is this little bit of public health communication that will actually stop a few people becoming infected.

Do you use mosquito coils and sticks to prevent mosquito bites? Join the conversation on Twitter and let me know what you think.

Want to learn more about the amazing world of Australian mosquitoes? Check out “A Field Guide to Mosquitoes of Australia” out now through CSIRO Publishing. Over 200 pages containing a pictorial guide to almost 100 different mosquitoes along with tips on beating their bite and protecting your family from the health risks of mosquitoes. You can order online or through your favourite local bookstore or online retailer.