Why do mosquitoes seem to bite some people more?

Back in 2015, I had an article published at The Conversation on why some people are more likely to be bitten by mosquitoes than others. It is one of the most commonly asked questions I get whenever I give public talks (or friends and family are quizzing me at summer BBQs).

This article was incredibly successful and has currently been read by approximately 1.4 million people. That is a lot of people. Hopefully the science of mosquito bites has got out there and actually helped a few people stop themselves or their family being bitten by mosquitoes!

The warm weather is starting to arrive here in Australia so I am sharing this once more for those wondering why they’re always the “mosquito magnet” among their friends…

Health Check: why mosquitoes seem to bite some people more

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There are up to 400 chemical compounds on human skin that could play a role in attracting mosquitoes.  sookie/Flickr, CC BY-SA

There’s always one in a crowd, a sort of harbinger of the oncoming mosquito onslaught: a person mosquitoes seem to target more than others. What is it about these unlucky chosen few that makes them mosquito magnets?

There are hundreds of mosquito species and they all have slightly different preferences when it comes to what or who they bite. But only females bite; they need a nutritional hit to develop eggs.

Finding someone to bite

Mosquitoes are stimulated by a number of factors when seeking out a blood meal. Initially, they’re attracted by the carbon dioxide we exhale. Body heat is probably important too, but once the mosquito gets closer, she will respond to the smell of a potential blood source’s skin.

Studies have suggested blood type (particularly type O), pregnancy and beer drinking all make you marginally more attractive to mosquitoes. But most of this research uses only one mosquito species. Switch to another species and the results are likely to be different.

There are up to 400 chemical compounds on human skin that could play a role in attracting (and perhaps repulsing) mosquitoes. This smelly mix, produced by bacteria living on our skin and exuded in sweat, varies from person to person and is likely to explain why there is substantial variation in how many mozzies we attract. Genetics probably plays the biggest role in this, but a little of it may be down to diet or physiology.

One of the best studied substances contained in sweat is lactic acid. Research shows it’s a key mosquito attractant, particularly for human-biting species such as Aedes aegypti. This should act as fair warning against exercising close to wetlands; a hot and sweaty body is probably the “pick of the bunch” for a hungry mosquito!

Probably the most famous study about their biting habits demonstrated that the mosquitoes that spread malaria (Anopheles gambiae) are attracted to Limburger cheese. The bacteria that gives this cheese its distinctive aroma is closely related to germs living between our toes. That explains why these mosquitoes are attracted to smelly feet.

But when another mosquito (such as Aedes aegypti) is exposed to the same cheese, the phenomenon is not repeated. This difference between mosquitoes highlights the difficulty of studying their biting behaviours. Even pathogens such as malaria may make us more attractive to mosquitoes once we’re infected.

Only females bite because they need a nutritional hit to develop eggs.
Sean McCann/Flickr, CC BY-NC-SA

Researchers are trying to unscramble the irresistible smelly cocktails on the skins of “mosquito magnets”. But the bad news is that if you’re one of these people, there isn’t much you can do about it other than wearing insect repellents.

The good news is that you may one day help isolate a substance, or mixes of substances, that will help them find the perfect lure to use in mosquito traps. We could all then possibly say goodbye to topical insect repellents altogether.

Attraction or reaction?

Sometimes, it’s not the bite as much as the reaction that raises concerns. Think of the last time the mosquito magnets in your circle of friends started complaining about being bitten after the event where the purported mosquito feast took place. At least, they appear to have attracted more than the “bite free” people who were also at the picnic, or concert or whatever.

But just because some people didn’t react to mosquito bites, doesn’t mean they weren’t bitten. Just as we do with a range of environmental, chemical or food allergens, we all differ in our reaction to the saliva mosquitoes spit while feeding.

People who don’t react badly to mosquito bites may think they haven’t been bitten when they’ve actually been bitten as much as their itchy friends. In fact, while some people attract more mosquito bites than others, there’s unlikely to be anyone who never, ever, gets bitten.

The problem is that people who don’t react to mosquito bites may all too easily become complacent. If you’re one of them, remember that it only takes one bite to contract a mosquito-borne disease.

Finally, there is no evidence from anywhere in the world that there is something you can eat or drink that will stop you being bitten by mosquitoes. No, not even eating garlic, or swallowing vitamin B supplements.

The ConversationPerhaps if we spent as much time thinking about how to choose and use mosquito repellents as we do about why mosquitoes bite our friends and family less than us, there’d be fewer bites all around.

Cameron Webb, Clinical Lecturer and Principal Hospital Scientist, University of Sydney

This article was originally published on The Conversation. Read the original article.

 

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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.

Summer summary of mosquito media madness

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Summer is always a busy time for me. As well as plenty of time sloshing about in the wetlands, there is often lots of interest from mosquito-curious media. There has been some intense bursts of activity in previous summers but the 2015-2016 was particularly interesting.

I certainly covered some new ground this summer. I responded to over 160 individual media requests in the past 6 months. From flies and food safety to the emergence of Zika virus. Here is a wrap from my media adventures and some valuable lessons learned for future science and public health communication.

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The good news of new virus discoveries

Usually, the discovery of a new mosquito-borne virus brings with it new concern for public health. This time though, there was some good news.

Towards the end of 2015, a paper reporting on a collaborative research project between University of Queensland, QLD Health and University of Sydney was published in Virology. This was the first publication detailing the discovery of Parramatta River virus, an insect specific virus that exclusively infects the mosquito Aedes vigilax. This virus does not infect people and poses no health risk.

A joint media release was issued by University of Queensland and University of Sydney and there was plenty of media attention. Not surprising given the usual negative associations with mosquito-borne pathogens!

There were dozens of articles, much of the attention focused on the team at University of QLD. Dr Jody Hobson-Peters was kept busy with local media including ABC and Brisbane Times. It was a great experience sharing the research with colleagues in Queensland, particularly great seeing so much exposure for PhD student Breeanna McLean and her newly published research.

I was surprised at how little attention there was in the news from Sydney media. The lesson here though was more about bad timing than uninteresting research. A couple of weeks after the initial media release, I forwarded around a few emails and sent out a couple of tweets and next thing you know, we made the front page of the local newspaper, the Parramatta Advertiser (see above). It was some great local coverage, not only about the virus discovery but it also provided an opportunity to raise awareness of mosquitoes and mosquito-borne disease on the eve of summer!

Lesson learned: A good reminder that if your research isn’t picked up immediately, give it another shot a few weeks later. Timing may make all the difference but perseverance does too!

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To stop sickness, swat or spray

Just in time for Christmas lunch and summer holiday picnics, I published an article on flies and food safety at The Conversation. I really expected this article to slip under the radar of most people. Coming out on Christmas eve doesn’t seem likely many would be clicking about on the internet but within a few days over 600,000 people had clicked on the piece!

Many of those clicks were thanks to the article being shared by IFLS but there was also plenty of interest from local media and I was busy with interview requests from ABC Local Radio across the country. Who doesn’t love hearing about how flies poop and vomit on your food? I was even interviewed by Grey Nomad Magazine!

Lesson learned: Applying a little science to seasonal urban myths and common uncertainties can prove popular and may be a good opportunity to promote a little science!

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Rain, rain everywhere with mozzies soon to come

With all the talk of El Nino and predictions of a hot and dry summer for the east coast of Australia, the summer was actually reasonably mild and extremely wet. Sydney was particularly battered by a series of storms and intense rainfall early in 2016.

More water generally means more mosquitoes. In response to the rain, many media outlets were interested in chatting about the prospects of a bumper mosquito problem. As well as talking about the prospects of an increase in mosquito-borne disease risk, it was a great opportunity to talk about personal protection measures.

There were some radio, print and tv spots that provided opportunities to talk about how to choose and use the right repellents.

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In 2015 I published a paper in the Medical Journal of Australia explaining that health authorities need to provide more guidance on how the community can get mosquito repellents working more effectively.

Typical health warnings and media release from health authorities (usually limited to grabs on news bulletins) but when there is an opportunity to do longer form radio interviews, there is a chance to put an emphasis on aspect of public health messages. The hook to get these longer spots is giving more than just warnings, by mixing up some interesting things about mosquitoes, you can catch a little extra attention and sneak in the public health messages between the fun and fascinating facts about mosquitoes!

One news outlet was really insistent in grabbing a hold of me for some comments ahead of the evening bulletin. They even sent a crew to meet me in the city while I was taking the kids along to the Sydney Festival!

Lesson learned: When doing tv for the evening news, it is ok to wear a t-shirt, shorts and runners just so long as you have a rain jacket handy to make you like like you could have just stepped straight out of the wetlands!

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From African forests to South American cities

While many of us were keeping our eyes on the developing outbreak of mosquito-borne Zika virus in South America towards the end of 2015, it wasn’t until February 2016 that the situation really grabbed the attention of the world’s media.

In late January, I published a piece at The Conversation titled “Does Zika virus pose a threat to Australia?” It prompted a little interest but it was the media conference coordinated by University of Sydney Media and Communications together with Australian Science Media Centre (AusSMC) that coincided with the announcement of the World Health Organization that the Zika virus outbreak was a Public Health Emergency of International Concern.

Together with colleagues from the University of Sydney’s Marie Bashir Institute of Infectious Disease and Biosecurity, I spoke at a media conference broadcast nationally on ABC News 24. There was a huge amount of media stories stemming from this media conference with over 500 individual articles identified across radio, tv, print and online. During the days and weeks following, I felt like I was spending more time at the ABC studios in Ultimo than I was in our lab! There were days when I spent hours on the phone doing radio interviews.

There were a couple of great longer form interviews that I really appreciated the opportunity to contribute to such as ABC Radio National’s Health Report and Rear Vision. There were also a couple of podcasts too, check out Science on Top and Flash Forward.

This flood of media requests also exposed me to a few more new experiences. There were live tv appearances on Sunrise, ABC News 24 and Sky News but probably one of the most interesting was my spot on Channel Ten’s The Project. It was interesting for a number of reasons.

Firstly, I was warned early on that one of the guests on the panel was comedian Jimmy Carr, a somewhat controversial figure notorious for jokes a little too close to bad taste. I’m not typically one to play the “wacky scientist” during interviews but what I was most cautious of was not being seen to be treating a very serious disease outbreak too lightly. I was determined to play the straight guy. In the end the interview turned ok but there were a couple of awkward moments that, luckily, ended up being edited out.

Secondly, simply doing the interview was unusual. It was a pre-recorded interview with me in a tiny room at the Channel Ten studio in Sydney and the panel in the Melbourne studio. I was sitting in front of a green-screen, staring down the camera with an earpiece blasting away in my ear. I have done live crosses before but they’re all been one-on-one interviews. This time it was with the panel and I found it incredibly difficult to get the feel for each of the panelists when they were asking questions. Missing that eye-to-eye contact was a disconcerting experience. Luckily, all turned out well in the end.

Lesson learned: Lots (I mean LOTS) learned while dealing with the interest in Zika virus! Probably another post in itself…but I would say that managing this volume of media wasn’t easy and it did eat up a lot of time (even though communicating public health messages is central to my “day job”) but this was important work.

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A morning with Dr Karl!

When it comes to science communicators in Australia, there are few with a higher profile than Dr Karl Kruszelnicki. We’d spoken on a number of occasions about mosquitoes but I’d never actually met him in person before. “Dr Karl” invited me to hang out for a morning recording interviews for ABC News 24, ABC Local Radio and also guest on his national “Science Talk” segment on Triple J’s Mornings Show with Zan Rowe.

The experience of a behind-the-scenes perspective on Karl’s hectic schedule and how he manages the frenetic pace of work at the ABC was an eye opener. Doing the hour long segment on Triple J was great, enlightening to get questions from a slice of the Australian community I don’t usually cross paths with when doing the usual community engagement. I good reminder of just how much anxiety there can be within the community when news of international disease outbreaks occur. Not surprising given the thousands of Australians travelling to South America each month….with more to come later this year when the Rio Olympic Games kick off!

You can listen to the segment here and you can also follow Dr Karl on Twitter.

Lesson learned: From a public health perspective, this is a great reminder that the concerns and anxieties around infectious disease can change depending on the sector of the community you’re dealing with. The core messages may remain the same but you’ll always need to consider your audience when fine tuning your public health messages.

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So, was all this worth it?

It was stressful. It was fun. It eroded much of my time that may have been spent in other ways but I see this as “doing my job” perhaps a little more than pure research scientists do. But how does all this convert into tangible metrics. How do you measure the reach and economics of all these media activities?

I’m fortunate to be supported by the University of Sydney media and communications team that helps out by providing some data on the metrics of my media activities each summer. What was all this time and effort worth?

Between November 2015 and Match 2016, I was quoted in over 160 media items. This adds up to a cumulative audience of around 8.9 million people, that is quite some reach! How much was it worth? Based on current advertising rates, about $1.6 million.

I’ve written before about how we can better value science and public health communication. Collecting these types of metrics can be useful for a range of purposes. Recently, I’ve been including media engagement as an “in kind” contribution to grant applications with valuation calculated on average media coverage that may be expected.

The lesson here is to take the time to record your media activities, not just so you have a list to demonstrate quantity but also so you can assess audience and value to your media activities. Work with your media and communications departments to see what extra information you can collect.

Got any other tips? Share them via Twitter!

 

 

 

 

 

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.

 

 

Does Zika virus pose a threat to Australia?

They’re small, spindly insects but their threat never dwindles – the bites of mosquitoes threaten death and disease in many parts of the world. The emergence of a little-known virus, Zika, from an African forest, is the latest to alarm the public, politicians and health authorities because of its potential link to birth defects.

What is Zika virus?

Zika virus is a mosquito-borne virus closely related to dengue and Yellow Fever viruses. Discovered almost 70 years ago in a Ugandan forest, the virus generally only causes a mild illness. Symptoms include rash, fever, joint pain and conjunctivitis.

Severe symptoms aren’t common and the illness was never thought to be fatal.

Despite detection throughout Africa and Asia, the virus rarely entered the spotlight of scientific research. It was overshadowed by the spread and impact of dengue and chikungunya viruses, which infect millions of people across the regions.

In the last decade, Zika virus outbreaks have occurred in the Pacific, with reports of severe illness. But again, Zika was considered a lesser threat than dengue and chikungunya viruses.

Everything changed in 2015 when Zika virus reached the Americas.

New outbreaks and severe symptoms

Since the first local Zika virus infection, cases have been reported from at least 19 countries or territories in the Americas, with more than one million suspected cases.

Rapid spread of an emerging mosquito-borne pathogen is news enough but people are also panicked by reports of more serious consequences of Zika virus infections, including post-viral Guillain-Barré Syndrome, an autoimmune condition where there person’s nerves are attacked by their own body.

Of most concern has been the rapid rise in rates of microcephaly, a birth defect which causes babies to be born with unusually small heads, in regions where Zika virus has been circulating.

While the role of Zika virus as the cause of microcephaly has not yet been confirmed, there is growing evidence of a connection between the two where pregnant women have been infected with the virus.

Babies born with microcephaly, and those who died shortly after birth, have tested positive for the virus, and there are close regional associations between clusters of birth defects and Zika virus.

There is enough concern for the Centres for Disease Control to issue health warnings to pregnant women planning to travel to these regions. [This also includes the Australian Government] Some health authorities are even advising people to postpone pregnancies.

There is no vaccine for Zika virus. Stopping mosquito bites is the only way to prevent infection.

Is Australia at risk of a Zika virus outbreak?

There is little doubt the virus can make it to Australia. There have already been a number of infections reported in travellers arriving in Australia from the Cook Islands and Indonesia.

Mosquito-borne viruses generally aren’t spread from person to person. Only through the bite of an infected mosquito can the virus be transmitted.

In the case of Zika, there have been some unusual cases of transmission, including through sex and the bite of an infected monkey. Despite these unusual circumstances, mosquitoes will still play the most important role in any local transmission.

While dozens of mosquitoes are capable of spreading local mosquito-borne pathogens, such as Ross River virus, only one of the 300 or so mosquitoes found in Australia can transmit Zika virus: Aedes aegypti, the Yellow Fever Mosquito, which is only found in north Queensland.

The Yellow Fever mosquito, Aedes aegypti, is critical to the spread of Zika virus in many regions of the world, including Australia.

For local Aedes aegypti to spread Zika virus, they must bite an infected traveller shortly after they return from a country where the virus is circulating.

While the chances of this happening are small, there is then a risk of a local outbreak occurring as the infected mosquito bites people who’ve never left the country.

This is the process that occurs in outbreaks of dengue in Far North Queensland. If we can get outbreaks of dengue, there is no reason we cannot, or won’t, get an outbreak of Zika in the future.

How to reduce the risk of transmission

Fortunately, authorities are well placed to contain an outbreak of Zika virus, as the required strategies are the same as management of dengue outbreaks.

Perhaps the real message here for Australian authorities is that they need to work diligently to keep exotic mosquitoes out of the country.

While Aedes aegypti may not become established in southern cities, even with a changing climate, there is great potential that Aedes albopictus, better known as the Asian Tiger Mosquito, could become established in southern cities. As well as a vector of Zika virus, it can spread dengue and chikungunya viruses and be a significant nuisance-biting pest. Keeping this mosquito out of our cities is critical.

Australians planning travel to South and Central America, including the Rio Olympics, should take precautions to avoid mosquito bites. Irrespective of Zika virus, mosquito-borne dengue and chikungunya viruses have infected millions of people, causing thousands of deaths, in the last few years and are reason alone to pack mosquito repellents. Be prepared to cover up with long sleeved shorts and long pants if in regions where risk is high.

The ConversationThis article was originally published on The Conversation. Read the original article.

Managing ‘Mozziegeddon’, Media and Public Health Messages

Sunrise_Mosquitoes

Beer, high tides, public holidays and blood thirsty mozzies. The perfect mix to set the media into a spin. How can you get the best public health messages out about mosquito bite protection?

It was almost as tricky managing the media this summer as it was the mozzies. Since late October, I’ve been interviewed on almost 50 occasions. A mix of pre-dawn calls from radio stations to live crossed to nationally broadcast breakfast televsion to taking talkback and dealing with mobile phone dropouts. It was a sweaty and stressful couple of months….and ‘mozzie season’ still isn’t over just yet.

The last few years have followed a pretty similar pattern. I get my first few calls around August/September. This is usually when we get our first blast of unseasonal heat and there are typically a few stories about people noticing bugs about their home and are worried about an early start to the mozzie season.

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Mozzie season kicked off early

This year we genuinely did have an early start to the mozzie season. The warmest spring on record kicked off the mozzie season early and one of the first big stories I did for Channel 9 News was almost derailed by swarms of mozzies! A few of the crew needed to retreat to the safety of their car. You can listen to me speaking with ABC New Radio here.

Following plenty of rain in early December, mosquito populations starting jumping up along the coast. Just in time for the Christmas holidays. During this period it is pretty common to respond to requests from media to talk about mozzies, particularly if there have been some public health alters from local health authorities.

Getting ready for a live cross to Weekend Today (Channel 9) but what you cannot see in this shot is the hundreds of mosquitoes that were swarming around me, standing in the middle of the mangroves for 20min getting ready for the segment attracted plenty of mozzie attention!

Getting ready for a live cross to Weekend Today (Channel 9) but what you cannot see in this shot is the hundreds of mosquitoes that were swarming around me, standing in the middle of the mangroves for 20min getting ready for the segment attracted plenty of mozzie attention!

A few things helped keep mozzies in the news. There were health warnings from local authorities after the detection of Ross River virus in southern Sydney. There were warnings about a new outbreak of dengue in Far North QLD. Flooding in central Australia also prompted warnings of outbreaks of mosquito-borne disease.

Then there was this piece I wrote on why mosquitoes bite some people more than others that attracted plenty of attention too….over 1.2 million readers in fact (thanks to republication by IFLS, SBS and Mamamia)!

Moztralia Day Mozziegeddon

As we headed towards our national holiday weekend and Australia Day celebrations, there were warnings that a big boost in mosquito populations were on their way. Yes, “mozziegeddon” was coming and the pesky little biters were set to turn our long weekend into a “moztralia day bloodbath“. Worse still, those taking part in the traditional Australia Day past time of beer drinking were being scared off the booze by fears of becoming “mozzie magnets“.

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“Mozzigeddon” turns Australia Day into Mozztralia Day! Great cartoon by Paul Zanetti accompanying a story at News.com

There is little surprise that stories about beer drinking and mozzies attract plenty of attention. It does almost every year. However, this year was a little different because health authorities were concerned about potential increases in mosquito populations and given recent detections of mosquito-borne pathogens such as Ross River virus, there was concern about public health risks. Those risks range from both the north coast of NSW to north-west of WA!

There was plenty of mosquito media coverage from SE QLD too. Local authorities were battling big mosquito populations and trying to control “3000 known mosquito breeding sites” the next generation of mosquitoes hatching following heavy rain and tidal flooding of local wetlands.

Local insect repellent manufacturers were also taking advantage of the boost in mosquito numbers. I’ve noticed an increase in tv and radio ads spruiking mosquito repellents and Aerogard also sent out “swat” teams to local parklands around Sydney on Australia Day promoting their “Mozzie Index“* website!

Aerogard "Bite Busters" hit the prime picnic spots around Sydney on Australia Day

Aerogard “Bite Busters” hit the prime picnic spots around Sydney on Australia Day

How could this media interest help spread the word on effectively stopping mosquito bites?

In the lead up to the long weekend I spoke with the breakfast show on 2UE (you can listen to the interview via link), Angela Catterns on 2UE, Chris Smith on 2GB as well as Robbie Buck and Linda Mottram on 702 Sydney. I provided a couple of brief grabs for news bulletins and even did my first live cross for the Sunrise breakfast program on Channel 7. You can also listen to interviews with 2SER, ABC Perth and ABC South East SA. [update 26 February 2015. There were a few more interviews, one fun one was with Richard Stubbs for 774 ABC Melbourne and you can listen in below, another was with Dom Knight on 702 ABC Sydney and you can read about that here. and I also chatted with Patricia Karvelas on Radio National Drive and you can listen here.]

It can be tricky getting good public health messages out during these very brief interviews, particularly for television. Radio can be pretty good as there is often plenty of time to get the message out (sometimes even time for talk back callers and questions) but for some of the commercial stations, time can be brief. Television is particularly challenging, I usually spend more time in the make up chair than being interviewed!

This summer I’ve been determined to ensure some key messages get out, particularly about choosing and using insect repellents most effectively. This is an issue I feel strongly about and I have an article coming out shortly in the Medical Journal of Australia on how local health authorities can do this a little better.

The two key messages were “if you’re using botanical based topical repellents, they need to be reapplied more frequently than the recommended DEET and picaridin based repellents” and “when using repellents, they must be applied as a thin coat over all exposed skin to get the best protection, not a dab here and there”.

Overall, I think I managed to get these two points into most radio and television interviews and I was happy to see that the general message got through in a lot of the print/online media too.

Below are some of my tips on getting a specific message out while dealing with the media.

1. Prepare. You would practice giving a conference presentation ahead of time so why not prepare for media? Think about the messages and how you can deliver them. What questions might you get asked? What will be the style of the presenter? Are there any questions you may be asked that you may want to avoid answering (e.g. questions of a political nature or something that could embarrass your employer)? How can you do that?

2. Learn from the professionals. If know you’re going to do some media in the coming weeks or months. Spend some time listening to talk back radio and reading newspapers. Take note of the number and length of quotes journalists use in articles. Make their job a little easier by providing concise quotes where possible. How do radio broadcasters conduct interviews? Listen to politicians and journalists being interviewed. How do they get their message across (or don’t in some circumstances). What makes you “switch off” from an interview – is it the topic or interviewee?

3. Create bridges between questions and your message. This is the thing I’ve found quick tricky but once you’ve got the hang of it, you can more effectively get the message out. There may not be a question asked that specifically relates to the message you need to get out. Learn how to transition from a brief response to the question asked onto the key messages you want to get out there. Don’t just launch off into your spiel at first chance, it is important to engage with presenter too, its a subtle art but like all things, it is only hard before it becomes easy.

4. Post-interview review. I’ll often take notes after an interview that help prepare for the next one. Things like the type of questions asked or how I answered questions, particularly if I feel my responses were clunky or I rambled a little! I’ve always found it interesting that slight differences in the way that questions are asked can often throw you off balance in an interview. If there are talkback callers, what questions were asked, especially if there was something out of left field! Making a note of these can help when preparing for the next batch of media.

5. Keep track of media activity. You never know when it may come in handy when applying for a promotion, grant or new job. I try to keep track of all media activities by recording the date, journalist, media outlet and brief description of topic. You can also speak to your local media and communications unit to see if they gather statistics on these things too. The team at the University of Sydney are great and it is fascinating to compare the analysis of different media activities, their reach and estimated value.

Perhaps the trickiest thing in all this is assessing whether this media activity actually helped the community prevent mosquito bites. It will be almost impossible to tell from human notification data on mosquito-borne disease given the numbers jump around so much from year to year anyway. What really need is some more attitudinal studies to see how people seek out and follow advice provided by local health authorities on mosquito-bone disease prevention strategies. Another thing for the “to do” list

Webb_NineNews_March2015[update 21 March 2015] Following the detection of Ross River virus amongst mosquitoes collected in NSW combined with a dramatic increase in human notifications of Ross River virus disease, there was another wave of interest by local media. You read a piece at the Sydney Morning Herald and watch a segment with me from Nine News.

Why not join the conversation on Twitter?

*A disclaimer: I provided some assistance to a local PR company back in 2012 that developed the “Mozzie Index” for Aerogard, particularly some info on the associations between mosquitoes and local environmental conditions.

Busting five myths of mosquito repellents

repellent_spraying_webbAfter a record year of West Nile virus activity in 2012, North American health authorities are on alert as the peak season of mosquitoes approaches. As of 16 July 2013, a total of 23 cases of human disease, including three deaths, had already been reported by CDC.

In many regions across the US, local mosquito control districts engage a range of strategies to reduce mosquito-borne disease risk. These may include broad scale insecticide use or the release of “mosquito fish” into derelict backyard pools. However, the first line of defense against biting mosquitoes remains the use of topical insect repellents.

In North America, the CDC provide detailed information on mosquito repellents but there still seems to be confusion amongst many in the community looking for alternatives to “chemical repellents”. These repellents are often perceived to be unsafe. For an Australian perspective, I’ve put together some guidelines on mosquito repellent use that provide a few more details than typically found on the websites of local health authorities.

In my experience of trying to promote the use of “known to be effective” repellents, I still find that there are many misconceptions and misunderstanding of how these products should be used. Below are the five myths I most commonly experience when it comes to the use of mosquito repellents.

Myth 1: Natural must be better

It isn’t surprising that most people associate “natural” products with better health. Many people perceive mosquito repellents derived from “natural” products, such as plant extracts, to be healthier choices. However, when it comes to mosquito repellents, there is clear evidence that these perceived “healthier” choices may not provide the best outcomes.

Studies have repeatedly shown that the most effective repellents are DEET and picaridin. DEET, in particular, has been shown to be very effective. Picaridin is pretty good too. Both products have shown to be effective in local field-based tests.

Unfortunately, many, many studies throughout the world have shown that botanical based repellents provide substantially less protection against biting mosquitoes than DEET or Picaridin. Products containing citronella, lavender, peppermint and Melaleuca oils are widespread and are often promoted as “DEET-Free” alternatives to the recommended repellents. There are many botanical-based insect repellents listed in the patent literature.

Essential oils of Australian native plants provide significantly less protection than DEET-based repellents. Expert review panels have suggested that products containing plant extracts should not be recommended in areas of endemic mosquito-borne disease or when biting mosquitoes are abundant.

It is important to remember that botanical-based repellents WILL provide some limited protection against biting mosquitoes. The biggest problem is that they will need to be reapplied 3-4 times as often as even a low dose DEET-based repellent to provide comparable protection. Botanical repellents may be fine for a quick trip to the backyard to hang the washing out but not for a long session of gardening or if you’re off for a hike.

It is also important to remember that using undiluted essential oils can also pose an important health risk, particularly in young children.

I often wonder if Koalas are bitten any less by mosquitoes than other Australian mammals given the amount of Eucalyptus leaves they consume! (Photo by DAVID ILIFF. License: CC-BY-SA 3.0)

What about “Oil of Lemon Eucalyptus”? That’s a botanical repellent and authorities recommend it against West Nile virus right? There is often some confusion regarding this product. It is not the essential oil, but rather a byproduct of the distillation process of the leaves of Corymbia citridora. Commonly known as PMD, it has been shown to be as effective as DEET (although generally requiring higher doses for comparable protection) and is recommended by the CDC in North America. The recommendations by CDC of this product should not be seen as an endorsement for other “botanical based” repellents.

Myth 2: Stronger repellent = fewer mosquitoes

This is probably the most common mistake made when choosing a repellent. The “strength” of a repellent (i.e. the concentration of active ingredients) doesn’t determine how many mosquitoes are kept at bay. It determines the duration of protection provided. It basically determines how long you are protected from biting mosquitoes.

The majority of published studies (the classic “arm in cage” style experiments) investigating the efficacy of repellents analyse the results in two ways, mean repellency rates (a comparison of how many mosquitoes land on a treated arm compared to an untreated arm) and mean protection time (for how long are all mosquito bites prevented). While the marketing companies may be interested in claims like “over 80% of mosquito bites prevented”, given that it only takes one mosquito bite for a pathogen to be transmitted, I’m hoping to prevent ALL bites! We should be far more interested in protection times than repellency.

Myth 3: Chemical repellents are dangerous

Both DEET and picaridin are considered safe. If used as directed, DEET-based repellents pose no substantial health risk. Despite being used by millions of people every year, there are few examples of reported serious adverse health impacts in the scientific literature.

There are many stories circulating about mosquito repellents having an unpleasant smell or creating an unpleasant feeling on the skin. There are also reports about damage to clothing and plastics in some instances. Some of these reports may be true but are most likely related to high concentration formulations. In the US, there are many brands available that contain over 95% DEET. In the vast majority of situations, however, most people would find that an approximate 10% DEET formulation would work perfectly well and not be associated with any of these unpleasant characteristics.

Myth 4: Apply repellent like perfume

A neighbor took great pleasure in telling me how ineffective mosquito repellents were. Repeatedly. One afternoon I saw him applying repellent to his children. The aerosol was sprayed around in the air above the kids as they jumped up and down. There was no way that the repellent was going to work.

While there is still some debate as to how DEET prevents mosquitoes bites, or how the response of mosquitoes to DEET is influenced by previous exposure or infection with a pathogen, we do know that to get the best results, the repellent should be applied as a thin covering on all exposed skin. It is for this reason I personally think creams and liquids are the best repellents to use.

Don’t apply repellent like a perfume. A spray “here and there” won’t work. Spraying it on your clothes won’t work either. Apply it in the same way as you would a sunscreen but keep in mind that you won’t need to apply it quite so often.

As summer approaches, the shelves of hardware stores and supermarkets are filled with various repellents, insecticides and traps. Some work better than others.

Myth 5: These gimmicks really work!

If it sounds too good to be true, it probably is! Gimmicks such as traps, ultrasonic devices and smartphone apps all sound very appealing if you find that putting on repellent is a bit of a hassle. Unfortunately, there is little scientific evidence that any of these will protect you from mosquito bites.

There is even a pill, recently approved by Canadian Health Authorities, that purports to only take 30 minutes to protect the swallower from mosquito bites. An excellent blog post, “Insect repellent you can eat – but does it work?”, refuting the claims of this product, is here. Also check this nice piece from 2012, “Homeopathic Insect Repellent: Is there anything the Natural Health Products Directorate won’t approve?

In short, there is nothing you can eat or drink that has been scientifically proven to prevent mosquito bites. That’s right, not even vitamin B.

In summary, the mosquito repellents widely available in North America, Australia and many other parts of the world are perfectly safe to use and can be effective in preventing mosquito bites. Many of these (and more) urban myths will persist for some time and perhaps it is time health authorities worked harder to communicate the benefits and effective use of the products available.

UPDATE: Thanks to BugGirl and Laurie Sullivan for the suggested tweaks!