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.

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Moving pictures and managing mosquitoes

Mangroves_Video_June2016

For a few months now I’ve been thinking through some future options for the blog and my science communications activities. I’ve been toying around with starting a podcast or video blog about my work in local wetlands.

#MosquitoWeek has just happened in the U.S. and as it coincided with the close of entries with the Entomological Society of America YouTube competition, I thought what better time to play around with putting together a video.

A year or so ago I had the chance to see Karen McKee (aka The Scientist Videographer) talk about social media and the ways she uses video as a critical component of her community engagement and communications. Since I’m already using Instagram to connect followers with my various wetland sites and mosquito studies (as well as other things), I’ve thought video could be a way to go.

Interesting too since images and video are (or are soon to be) increasingly dominant in social media.

I’m an advocate for mosquito control to be part of overall wetland management. I think I’m sometimes seen as the enemy of wetland and wildlife conservation, not surprising given the perception of mosquito control still influenced by the DDT debate. As we push for the construction and rehabilitation of urban wetlands, the pest and public health risks associated with mosquito populations do need to be considered by local authorities.

I’m often arguing that ecologically sustainable mosquito management is actually critical to wetland conservation. If you’re encouraging the community to visit your wetlands, what happens when they’re chased away by mosquitoes? What about the community living around the wetland? Will nuisance-biting erode the good will of the community for wetland conservation?

You can watch my video, “Why is mosquito management important in our local wetlands?”, at YouTube or below:

You can check out some of my other posts of wetlands, mosquitoes and social media below:

Should we start pulling out mangroves to save our wetlands?

Does wetland rehabilitation need mosquito control?

Can social media help track environmental change?

Mosquitoes, constructed wetlands, urban design and climate change: Some workshop resources

Let me know if you’d be interested in seeing more videos! Send me a tweet.

Safely avoiding mosquito bites when pregnant

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Hundreds of millions of people fall ill due to mosquito-borne pathogens every year but the recent rise in birth defects associated with Zika virus emerging in the Americas has health authorities on alert.

Zika virus is transmitted by mosquitoes, primarily by the Yellow Fever mosquito, Aedes aegypti. Since its discovery in Africa around 70 years ago it has avoided the public health spotlight due to the relatively mild illness it causes. Throughout Africa and Asia it is overshadowed in importance by the diseases caused by malaria parasites as well as dengue and chikungunya viruses.

For background on the rise of Zika virus, see my article for The Conversation.

Zika and the health risks to those pregnant and their unborn children

While Zika virus has yet to be fully confirmed as the causative agent in birth defects (such as microcephaly), there is clearly enough concern among health authorities in many parts of the world to issue warnings to those pregnant to avoid travel to countries experiencing an outbreak of Zika virus.

Authorities in Columbia and El Salvador have even gone so far as to advise residents to avoid falling pregnant for up to two years.

The Australian Government issued the following advice via their SmartTraveller website:

“Until more is known about Zika virus, and taking a very cautious approach, we advise women who are pregnant (in any trimester) or who plan to become pregnant to consider postponing travel to any area where Zika virus transmission is ongoing. If you do decide to travel, talk to your doctor first and strictly follow steps to prevent mosquito bites during your trip.”

For many, the option of not travelling will be easy. But what if you still want to travel? What if you’re doing business in some of these countries? What if you need to travel to visit family? Cancelling a trip isn’t always the easiest options.

Reducing risk of mosquito-borne disease while travelling

Irrespective of the current Zika outbreak, travelling while pregnant brings various health and safety risks.  Other mosquito-borne diseases, such as malaria and dengue, also pose a risk to pregnant women and their unborn children. These serious risks existed long before Zika virus grabbed the public health spotlight.

Unfortunately, there is no vaccine currently available for Zika virus. Vaccines are in development for dengue viruses and anti-malaria drugs are available so consult your local travel health clinic.

While travelling, staying indoors as much as possible, particularly air-conditioned accommodation, will greatly reduce exposure to mosquitoes. This may not be how you expected to spend your time during a South American holiday!

Many people associate mosquito-borne disease with wetland or jungle environments but as Zika virus is spread by mosquitoes found in urban habitats (e.g. water-filled containers), travellers should not be complacent if only visiting cities. Some of the biggest recent outbreaks of mosquito-borne disease have been in major metropolitan regions in the Americas and Asia.

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Mosquito control in Brazil, a striking image of the battle against container-inhabting mosquitoes (Image: Ernesto Benavides via International Business Times)

If you’re staying at a high end resort, chances are there will be a well established insect control program. This typically includes widespread spraying for insecticides to knock down any mosquito populations. This may not completely remove risk but it will substantially lower potential exposure to mosquitoes. Again, don’t be complacent and take special care to avoid mosquitoes if taking a day trip to local villages or other tourist attractions.

Sleeping under a bed net is usually recommended in regions where malaria is an annual problem but this may not offer that much protection against Zika virus as the mosquitoes that spread the virus primarily bite during the day. If you’re planning on taking some afternoon naps, make sure it is under a bed net. A range of insecticide treated bed nets are available from your local camping store.

There is also an ever increasing range of “pre-treated” insect repellent clothing but evidence is scarce on just how effective these are at preventing bites. Treating clothing with insecticide (e.g permethrin) yourself would be a better option but don’t expect that wearing treated clothing means you don’t have to put insect repellents on exposed skin.

Safe and effective use of mosquito repellents

There will be anxiety among many about using insect repellents while pregnant. Are they safe? Will they impact the baby?

Without doubt, the most commonly used, safe and effective mosquito repellents is DEET (I’ve written about these repellents extensively, see here and here but I’ll summarize below). This is found in lots of major commercial brands and is a mainstay in the recommendations issued by health authorities the world over. Problem is, it can be hard to find information on how to choose and use the repellent that’s right for you and your situation.

The first point to remember is that the the strength of the formulation determines how long you’re protected against mosquito bite, not how many mosquitoes are kept away. For example, a 10% DEET based repellent may provide 2h protection, a 20% formulation may provide 4h protection. When choosing a repellent, think about how long you need protection for and how frequently you’re happy to reapply.

Secondly, the repellent must be applied as an even coverage on all exposed skin. If there are “gaps” in the application, mosquitoes are sneaky enough to pick a spot to bite. In the case of the mosquitoes that spread Zika, dengue and chikungunya viruses, pay special attention to application around the lower legs and feet, that’s where they like to bite.

Be sure to reapply repellent after swimming or sweaty exercise too.

There is no need to apply mosquito repellents to skin under clothing.

Are repellents safe to use when pregnant?

Health authorities and regulatory agencies rarely provide specific warnings on the use of insect repellents by those pregnant. While there haven’t been many clinical trials, these papers (here and here) demonstrate a lack of documented significant health risk associated with the used of DEET-based repellents. Most notably, a study of almost 900 women using mosquito repellent in the second or third trimester and no adverse neurologic, gastrointestinal, or dermatologic effects were observed in women or their infants for a year after birth.

It is important to balance the distinct lack of evidence of major health risks associated with repellents to the rapid rise in microcephaly in Brazil. Repellents can stop mosquitoes bites, stop mosquito bites and remove the risk of infection. If you use registered mosquito repellents as directed on the label, they are effective and safe.

Common sense must prevail. Even if you’re concerned about the use of repellents, make some compromises while still protecting yourself for infection. Choose a lower dose DEET-based repellent and reply more often. This is a better approach than trying a repellent that hasn’t been proven effective.

I’m often asked what formulation works best. There are aerosol sprays, roll-ons, pump-pack sprays, creams, gels, lotions and even towelettes. There really haven’t been many scientific studies looking at which if these formulations work best, and for good reason. As the active ingredients in these formulations are the same, it doesn’t really matter. The critical issue is to choose a formulation that you’re most comfortable using to ensure you get a good coverage over exposed skin. I like creams and pump-pack sprays but I generally apply the product to my hands first and them spread across skin.

Always ensure you avoid getting repellent in your eyes or any cuts or abrasions.

I don’t like the smell or feel of mosquito repellents!

There is often a temptation for those who dislike DEET to use a “natural“, plant-based repellents. Notwithstanding that these products provide shorter periods of protection, tea-tree oil (particularly when used in home-made concoctions) also has the potential to cause skin irritation. While plant-based mosquito repellents may offer some protection against nuisance-biting mosquitoes, they shouldn’t be relied on to prevent mosquito bites in regions of mosquito-bore disease outbreaks.

Many health authorities recommend para-Menthane-3,8-diol (PMD), a product commonly known as “oil of lemon eucalyptus”. This is not an essential oil but rather the by product of the distillation process of Corymbia citriodora. The product does repel a range of biting insects and there is no evidence suggesting it should not be used in pregnancy. However, in Australia, this product is generally more difficult to find in grocery stores and pharmacies than DEET- or picaridin-based repellent formulations.

It would be brilliant if there was a non-topical options for stopping mosquito bites. Unfortunately, there is nothing that has been proven effective. Do not rely on mosquito repellent wrist bands as they do not provide adequate protection against mosquitoes. Also, remember that there is nothing you can eat or drink that will stop you being bitten by mosquitoes.

Rounding out the advice on mosquito repellents, make sure you pack some before you leave. You can never be sure of what products will be available at your destination or whether it has gone through the process of registration (e.g. APVMA in Australia or EPA-registered in the U.S.). It is not unheard of for mosquito repellent stock to sell out during outbreaks of disease.

Lastly, if you’re travelling to regions experiencing dengue, chikungunya and Zika virus outbreaks, don’t necessarily expect to be swarmed by mosquitoes in the same way you will around many of Australia’s coastal wetlands. Don’t be complacent if there are only a few about, remember, it only take one bite to transmit a pathogen. Don’t wait until you notice mosquitoes biting, wake up and put on that repellent.

There is a great set of questions with answers provided by the CDC for pregnant travellers on Zika risk and prevention and here is another reminder of the travel advice provided by the CDC and Australian Government for pregnant women.

If planning to travel while pregnant, consult your local doctor or travel health clinic for advice.

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.

 

 

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.

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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.

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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.

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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.

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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.

 

 

 

 

Could a mosquito bite make you a Jedi?

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On the eve of the release of Star Wars The Force Awakens, I’ve been revisiting bits and pieces of the previous six Star Wars movies. You know what stands out? I’ve been thinking about the possibility that wielding “The Force” may just be a symptom of parasitic infection!

Growing up with the original trilogy of Star Wars films, my perspective on “The Force” was entirely defined by Obi-Wan Kenobi’s explanation to Luke in A New Hope, “The Force is what gives a Jedi his power. It’s an energy field created by all living things. It surrounds us and penetrates us. It binds the galaxy together.”

I always thought of it as more a spiritual, rather than a scientific, thing. If I thought about it really hard, I could snatch that tv remote into my hand from across the room. Apparently it doesn’t quite work that way. I’d need to be infected with a parasitic pathogen. Midi-chlorians.

Midi-chlorians were explained to a young Anakin Skywalker by Jedi Master Qui-Gon Jinn in The Phantom Menace as “Midi-chlorians are a microcopic lifeform that reside within all living cells and communicates with the Force. We are symbionts with the midi-chlorians. Life forms living together for mutual advantage. Without the midi-chlorians, life could not exist, and we would have no knowledge of the Force. They continually speak to you, telling you the will of the Force.”

So, these intracellular microbes speak to us? Do they control the host? Are Jedi just doing the dirty work of midi-chlorians? I know midi-chlorians have sparked a sea of frustration among some Star Wars fans but lets just assume for a moment that the only reason Force users can do what they do is because they’re infected with special strains of these parasites.

Luke_lightsaber_wampacave

How many times have you imagined you could snatch the remote from coffee table through nothing more than concentrated thought alone?

Can pathogens and parasites control their hosts?

We know that in a galaxy not so far away and not so long ago, parasites have been described that alter the behaviour of their hosts. See here  and here and here. From mind-controlling fungi to parasites that break down your fear of predators there are plenty of examples of how parasites change the behaviour of hosts to their own benefits.

There are insect symbiotes and mostly they’re beneficial. But when it comes to mosquitoes, microbes including viruses, bacteria, fungi and protozoa can influence their role in disease outbreaks.

Viruses, such as dengue, may even influence the behaviour of mosquitoes to increase the chances of their transmission to new hosts. Infection with a virus may also change the way mosquitoes respond to insect repellents. But when some mosquitoes are infected with an intracellular bacteria, a bacteria that’s not naturally found in this mosquito, their ability to transmit dengue viruses is blocked. It can also disrupt their blood feeding and reduce their lifespan.

Now, if mosquitoes are capable of transmitting blood-borne pathogens, could they also transmit midi-chlorians? If a mosquito bites you after its taken a blood meal from Yoda, Obi-Wan Kenobi or Luke Skywalker, could you start using the force? Is the ability to use the force a symptom of vector-borne disease?

Aedes aegypti

Itchy yet? Dozens of mosquitoes drinking in a mosquito researcher’s blood! (Image: Alex Wild)

Are there Medical Entomologists in the Star Wars universe?

I don’t know how many medical entomologists will be featured in The Force Awakens. According to Wookiepedia there are mosquitoes (or at least mosquito-like insects called Msqitoes) in the Star Wars universe but how would you go about working out if theses or any other blood feeding arthropods could transmit midi-chlorians between Jedi and us normal non-Jedi folk?

When investigating outbreaks of suspected mosquito-borne disease, there is a number of things to consider. Are there clusters of cases that may suggest localised exposure to mosquitoes? If there is widespread disease with little or no link to environments associated with mosquitoes, it is usually enough to suggest the pathway of pathogen transmission doesn’t include mosquitoes. But where there is evidence to suggest mosquitoes are playing a role, where to next?

Collecting and testing field collected specimens can provide some evidence. There are mosquito-borne pathogen surveillance programs in many parts of the world. They rely on collecting and testing adult mosquitoes but can also involve taking blood from wild or domestic birds to determine the circulation of mosquito-borne pathogens in the environment. However, just because a mosquito tests positive to a pathogen, it doesn’t mean it is spreading it to people.

There are thousands of mosquito species worldwide but relatively few effectively transmit mosquito-borne pathogens. For example, in Australia around 40 mosquitoes have been implicated in the transmission of Ross River virus but only one mosquito can transmit dengue viruses. Unless there is a specific relationship between the pathogen and the mosquito, the pathogen wont be transmitted.

Complex path of pathogens from host blood to mozzie spit

Mosquitoes aren’t like dirty syringes. They don’t transfer infected droplets of blood between people. Mosquitoes must become infected with the pathogen before it can then pass it on. Taking a virus as an example, the virus must be ingested by the mosquito together with a blood meal from an animal and then the virus must pass into and out of the cells lining the insect’s gut before spreading throughout the body of the mosquito. Once the salivary glands are infected (a process that takes about a week), the virus is passed on through the spit of the mosquito when it next bites (when feeding on an animal, a mosquito will inject some saliva to get the blood flowing).

Not all mosquitoes can transmit all mosquito-borne pathogens. Mosquitoes cannot transmit non-mosquito-borne pathogens. That’s why mosquitoes don’t spread Ebola virus.

Dagobah_Wookipedia

For a mosquito researcher, surely Dagobah is top of the list of fantasy field trip destinations! There has to be plenty of mozzies on this swamp covered planet! (Image: Star Wars)

How would you test the ability of mosquitoes to transmit midi-chlorians?

Firstly you need some blood feeding mosquitoes. If there was anywhere in the Star Wars universe where mosquitoes could be found, surely it is Dagobah. The whole planet is essentially covered in wetlands. Once you’ve got the mosquitoes, now all you need is some midi-chlorian-filled blood.

Expose caged mosquitoes to a mix of blood and midi-chlorians (or ask a Jedi to kindly volunteer their arm). For those mosquitoes that feed, they can be put aside and kept alive for as long as possible. Every few days, mosquitoes are removed and tested for infection. Legs and wings can be removed from the mosquito and tested separately from the body. If they’re positive, it indicates the virus has spread through the body of the mosquito.

Next, the proboscis of the mosquito can be inserted into a micro-capillary tube filled with growth media. Once inserted into the liquid, the mosquito will instinctively feed and expectorate saliva. The saliva and growth media mix can then be tested for the presence of virus. If this mix is positive, it indicates the mosquito is transmitting the pathogen.

vcexperiments

Known as “vector competence” experiments, studies investigating the ability of different mosquito species to transmit different pathogens help build up a profile of each mosquito and its potential role in the spread of local and exotic mosquito-borne pathogens.

Studies of this nature have been conducted for many, many mosquito species worldwide and many, many different pathogens. Here is a recent example of a study conducted to determine how the transmission of a strain of West Nile virus by mosquitoes influenced an outbreak of mosquito-borne disease in horses.

Things can start to get a little more complicated when you take into account the interaction between the host (e.g. an animal) and the pathogen, the level of viremia that may develop and the propensity of the mosquito to bite people. For example, some mosquito species may be very susceptible to infection and effective at transmitting a pathogen but if those mosquitoes prefer to only feed on birds, the risk to people are generally much lower.

The take home message from all these studies is that the interactions between pathogens, mosquitoes and the animals and people carrying the pathogens are complex. When assessing the risk of mosquito-borne disease outbreak, designing more effective mosquito-borne pathogen surveillance programs or developing strategic public health responses, it is critical to understand the ability of local mosquitoes to transmit pathogens.

In theory, a mosquito taking a blood meal from a Jedi whose blood contains a high concentration of midi-chlorians could potentially pass on some Force-inducing infections to other people. Makes you wonder why Yoda was hanging out in a swamp planet?

Disclaimer: There is little doubt the issue of midi-chlorians has been discussed, dissected and the implications for the ability to wield the force determined within Star Wars Expanded Universe/Legends literature. I know I’ve taken a little artistic license here but if you’re a Star Wars aficionado, please take this article for what it is, a fun way to communicate the science behind mosquito and mosquito-borne disease research.

Why not join the conversation on Twitter?

I’ll leave you with this great CDC video on immunization.

UPDATE! [9 January 2016] So, it seems that not only do mosquitoes potentially help make Jedi in the Star Wars universe but, as the The Force Awakens demonstrates, mosquito-inspired aliens are out and about in the bars and cantinas of the galaxy! Just in the remote chance you haven’t seen the movie, I won’t describe when and where these creatures pop up but they’re known as the “Dengue Sisters” and represent a sentient species of small insectoids known as Culisetto. They look pretty awesome (see photo below from “Star Wars: The Force Awakens Visual Dictionary” by Pablo Hidalgo)

denguesisters

Dengue Sisters from Star Wars: The Force Awakens Visual Dictionary (Thanks Cybergosh for the tip off)!

Perhaps I need to petition Hasbro to create a “Dengue Sister” action figure!

 

 

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.

Why would a Californian drought trigger an outbreak of mosquito-borne disease?

CalifornianBushfireSunset_DawnEllnerMosquitoes need water almost as much as they need blood so why is it a drought could cause an outbreak of mosquito-borne disease? Why does the drought in California mean less water but more mosquito-borne disease?

More than just water

All mosquitoes need water. It could be a teaspoon of water in a pot plant base or an expanse of wetlands inundated by tides. Following flooding, health authorities are typically quick to issue public health warnings about increased risk of mosquito-borne disease. However, more mosquitoes doesn’t always mean more mosquito-borne disease.

Mosquitoes need blood. As well as biting people, they also bite animals. Outbreaks of mosquito-borne disease typically requires the presence of wildlife, animals that act as reservoirs for the disease-causing viruses.

CaliforniaDrought_EPA

Drought is hitting California hard (Source EPA via Huffington Post)

Mosquitoes, drought and West Nile virus

West Nile virus is a mosquito-borne pathogen generally spread between birds and people by mosquitoes. Culex mosquitoes they appear to play the most important role in West Nile virus transmission in urban environments, particularly Culex pipiens.

These mosquitoes are generally not breeding in wetlands. They’re found in artificial structures ranging from backyard containers and neglected swimming pools to stormwater pipes and drains. These mosquitoes have moved out of the swamps and into the suburbs! They’ve also moved into the constructed wetlands popping up throughout the suburbs too.

Rather than water birds associated with wetland environments, the birds playing a key role in West Nile virus transmission are small songbirds common in urban areas. These birds roost in large numbers and are the target the the Culex mosquitoes that preferentially feed on birds. It is important to keep in mind that there is still a lot of learn about how the roosting behaviour of birds influences their exposure to West Nile virus.

During “dry” conditions, bird populations are concentrated in urban areas (where humans provide water and food) and mosquito populations associated with urban water-holding structures increase. During “wet” summers, bird populations may be more widely dispersed through the environment with many birds roosting and foraging well away from residential areas and reducing the contact between birds, mosquitoes and people. When the “dry” summers arrive, birds move back close to the people. People who provide water.

Culex_molestus_Photo_StephenDoggett

The Culex pipiens group of mosquitoes play an important role in the transmission of West Nile virus and are closely associated with urban environments. They like biting birds. (Photo: Stephen Doggett, NSW Health Pathology)

In the absence of rain, water stagnates in stormwater pipes and drains providing favourable conditions for mosquitoes. During “wet” summers, the mosquitoes are flushed out by increased water flows and, even if they don’t, permanent habitats are more likely to support populations of mosquito predators such as fish.

During “dry” summers, people also start storing water around the home. Once water restrictions kick in, the desire to keep the garden looking healthy can potentially pose an indirect health risk to the homeowner as they hoard water around the home that provides habitat for mosquitoes.

In short, dry conditions help concentrate mosquitoes and birds in close proximity to people and increase the risk of mosquito-borne disease outbreaks.

WestNileSign

Mosquito control in Texas in response to an outbreak of West Nile virus raised much concern within the community. It can sometimes be difficult to balance the need for mosquito control with community engagement to allay fears of insecticide -based human health risks (Source: CDC)

An outbreak in Texas in 2012

West Nile virus was first introduced into North America in 1999. Despite rapidly spreading across the continent in the subsequent years, the numbers of outbreaks steadily declined and, to some extent, it fell of the radar as a serious public health concern. There was a resurgence of the disease in 2012 with an outbreak primarily focused in Texas.

There was a substantial increase in the number of cases compared to previous years with an unusually warm spring thought to have played an important role in driving the outbreak. Health authorities were warned that outbreaks of this nature may continue.

USDroughtMonitors_7April2015West Nile virus and the Californian drought

For the past couple of years, California has been hit with one of its worst droughts in decades. It is having widespread impacts and may also be increasing mosquito-borne disease. Californian authorities have been battling potential public health risks associated with mosquitoes on many fronts. There were record numbers of deaths due to West Nile virus disease in 2014 and exotic mosquitoes were detected. This included an Australian mosquito that was found in Los Angeles.

It is relatively early in California’s mosquito season but West Nile virus has already been detected. Health authorities are warning that another bad year for West Nile virus activity could be ahead despite the ongoing drought. There is already a suggestion that the severity of the current drought may be exacerbated by climate change and that climate change may be playing a role in future West Nile virus risk internationally.

There is little doubt that prolonged drought will impact Californian residents in many ways and an increased risk of mosquito-borne disease is just one of them. Fortunately, mosquito and vector control agencies in California work closely with local health authorities to monitoring mosquito and pathogen activity to provide warnings of increased risk. However, there is responsibility for everyone to ensure that the ways in which water is conserved around the home doesn’t increase the risks associated with mosquitoes.

potplantsaucer

If you’re worried about keeping your pot plants well watered but don’t want to provide a home for mosquitoes, fill the saucer with sand. It will keep the moisture in place but there is no “free water” for mozzies to use!

If you’re not able to “dump and drain” water holding containers, make sure that they’re covered to stop mosquitoes getting in or out. If you’ve got a swimming pool that’s neglected, start chlorinating it or release fish to eat through any mosquitoes. There are also a few mosquito control products that could be used, the most appropriate would probably be the insect growth regulator methoprene, it will stop mosquitoes emerging from the water holding container.

Why not share your tips on saving water around the home while not increasing opportunities for mosquitoes on Twitter?

The photo at the top of this post is taken by Dawn Ellner (see original photo here)