Dinosaurs, DNA, Mosquitoes and Movies

I thought I’d celebrate the 20th anniversary of one of my favourite movies, Jurassic Park, by posting on, what is arguably, the most famous mosquito in cinematic history.

As most people probably already know, the “science” of the story revolves around the cloning of dinosaurs from DNA samples obtained from prehistoric mosquitoes. The DNA was purportedly extracted from blood meals contained within these mosquitoes that had been trapped and preserved in amber. Even though studies have suggested that DNA wouldn’t survive long enough to assist in making “Jurassic Park” styled dinosaurs a reality, modern molecular techniques are quickly improving and may make the impossible a little more possible in the future.

If we can improve the technology enough to make this happen, could the research team who receives the multimillion dollar grant please go to the trouble of hiring an entomologist? You don’t want to make the same mistake as the team led by entrepreneur John Hammond.

I’m not just referring to the creation of nasty people eating dinosaurs. If you’re hunting around for mosquitoes in amber, you’d better pick the specimens that may actually contain blood!

The screen shot above is taken from a scene in the movie (see YouTube clip below). The scene provides some background to the process behind dinosaur DNA capture. It has already been pointed out elsewhere that the mosquito specimen depicted in the video is a male mosquito. Male mosquitoes don’t feed on blood.

Only female mosquitoes feed on blood, they need the nutritional hit to develop their eggs. Mosquitoes take blood from a range of vertebrates. Birds, mammals, frogs and reptiles. In theory, there is no reason why a mosquito wouldn’t bite a dinosaur. Blood meal analysis of mosquito populations in Florida during an outbreak of West Nile virus revealed that a number of mosquitoes were feeding on alligators (Alligator mississippiensis).

The problem isn’t just that the mosquito depicted in the video is male, the type of mosquito shown doesn’t feed on blood at all!

Not all mosquitoes need a blood meal. There is a group of mosquito species that belong to the genus Toxorhynchites. These are large, very beautiful mosquitoes that often have a metallic appearance. They are really the “good guys” of the mosquito world. Their immature stages are predatory. They are typically found in natural or artificial water holding containers such as buckets, bird baths, tree holes or discarded tyres. They tend to move in and eat through some of the other pest mosquitoes found in these types of habitats such as Aedes aegypti and Aedes albopictus. These mosquitoes spread pathogens such as the dengue and chikungunya viruses.

Notwithstanding their size, a Toxorhynchites is most easily identifiable by their long bent proboscis. Compare the photo below to the screen shot from the Jurassic Park video. See that bent proboscis? The bent proboscis assists in nectar feeding by this mosquito. (as an aside, if you look at the shot of the “Jurassic Park” mosquito, you can see that the wings of the mosquito are actually squished down along the side of the abdomen. The “wings” shown in the mosquito are fake. There are no wing veins)

Taken from the archives of the Walter Reed Biosystematics Unit

Lets give credit to John Hammond and the team at International Genetic Technologies, perhaps it is samples from these mosquitoes that they were able to use to clone the prehistoric plants that were growing throughout Jurassic Park?

If you’ve decided to go out and hunt down some dinosaur DNA, best look out for mosquitoes that actually feed on blood!

Do we know that mosquitoes were even buzzing about with the dinosaurs?

There is strong evidence, both preserved specimens in amber as well as fossils, that mozzies have been about since at least the Cretaceous Period. A paper by Poinar et al. (2000), in their description of a small mosquito named Paleoculicis minututs from a sample of Canadian Cretaceous amber, provides references to almost 40 references to mosquitoes in the fossil record. Paleoculicis minututs was thought to have dated back to 66-100 million years ago but the oldest known record of a mosquito is Burmaculex antiqus described from Cretaceous Burmese amber (89.3-99.6 million years ago).

Recently, two new mosquito species, Culiseta kishenehn and Culiseta lemniscata, were described from compression fossils in shale deposits dating from 46 million years ago. These fossils are pretty amazing as many of the morphological features we use to identify mosquitoes, such as scales and wing veins, have been preserved.

Mosquito fossil of Culiseta lemniscata  Smithsonian’s National Museum of Natural History

There are mosquitoes related to these two species flying about today. There are thought to be almost 40 species belonging to the genus Culiseta. They’re generally considered to be associated to cooler-temperature climates. We have a few species in Australia such as Culiseta frenchii, Culiseta hilli, Culiseta inconspicua and Culiseta litteri. They tend to be associated with ground pools in forested areas. Although they will bite humans, they are rarely considered pests and have not been associated with the transmission of pathogens locally. However, related species are thought to transmit both Eastern and Western equine encephalitis virus in North America. Mosquitoes belonging to Culiseta, although they will bite mammals, are generally thought to prefer blood meals from birds.

Culiseta morsitans taken from Walter Reed Biosystematics Unit

While it may be fun (and nerdy) to spot mistakes like this in movies, it is nice to be given an opportunity to dig back through the literature and have a closer look at some of the more unusual mosquito species and their place in the fossil record. Perhaps we’ll find some mosquitoes in Australian fossils someday too. I’m not aware of any mosquitoes identified from fossils found in Australia but there are research projects investigating insect specimens in amber. Fingers crossed.

UPDATE. Wouldn’t you know it! Just as I hit “publish”, I notice that a similar story is doing the rounds today, something must be in the water!!! Joe Conlon has been reported in a few places reporting the same issue. Some more coverage here.

UPDATE [15 October 2013]. Some more “mozzie fossil” news is making headlines today with the fossil of a blood-engorged mosquito in oil shale from northwestern Montana, USA, has been described in a recently published paper!

Newly described blood-filled mosquito fossil (The National Museum of Natural History, Washington via Nature)

The discovery of a mosquito (Culiseta sp. Culicidae) fossil clearly displaying an engorged abdomen from a recent blood meal has provided more evidence that mosquitoes were feeding on vertebrates as far back as 46 million years ago. Not only does the specimen look engorged, mass-spectrometry analysis of the specimen identified heme, the oxygen-carrying group of hemoglobin in the host’s blood. The study, publish in Nature, describes the discovery but also details the “extremely improbable event” that this fossil was created, let alone discovered tens of millions of years later!  While discoveries like this still aren’t going to bring back the dinosaurs, they do confirm hematophagy in the fossil record. I wonder what other specimens are out there?

Update [1 December 2014] Jurassic World repeats the mistakes of the past…

A screen shot from the Jurassic World trailer…is this supposed to be a mosquito?

November saw the release of a trailer for the new movie in the “Jurassic” franchise, Jurassic World. As well as attracting plenty of attention from fans and media about the movie, it also attracted plenty of interest from dinosaur lovers and entomologists. There was a great post by Dr. David Steen on some of the errors spotted by wildlife biologists and paleontologists and Morgan Jackson put together a nice piece on the entomological inaccuracies of the trailer (it is a crane fly, not a mosquito, locked up in that amber). Despite all of this, perhaps the biggest issue to have arisen is the purported unauthorized  use of illustrations in accompanying promotional material.

“Shut up, Scientists! Always have to ruin everything with facts and accuracy.”

It would be silly to get REALLY upset about the mosquito/crane fly mix up but there was no shortage of people pointing out the mistake, you’d think they’d fix it this time around (unless there is a gag we’ll get in the movie about crane flies and non-biting mosquitoes). However, any opportunity to point out some scientific inaccuracies provides an opportunity to raise awareness of genuine scientific knowledge. I’m regularly called up to investigate “giant mosquito” problems….that almost always turn out to the crane flies (they don’t bite BTW).

I’ll be heading along to see the Jurassic World monsters in 2015 but perhaps I’ll take the kids back to the museum to learn about dinosaurs and some of the other extinct Australian mega fauna for a hit of real science.

Now, about that light saber in the trailer for “The Force Awakens”….

Testing the claims of new mosquito repellents

Having worked in the field of “mosquito research” for over 10 years, I’m no stranger to new mosquito repellent formulations or mosquito traps that purport to provide a breakthrough in the prevention of mosquito-borne disease. I’ve tested dozens of these products, both in a research capacity and as part of the registration process of new products here and overseas.

Since DEET first become widely available in the 1950s, there really hasn’t been many new topical mosquito repellents reaching the market AND accepted by health authorities. Picaridin and PMD are probably the two exceptions. For the most part, the vast majority of mosquito repellents currently available contain one of these three active ingredients. Most of the recent developments have been in the formulations, making them “nicer” to use. I’ve written about these various repellents elsewhere (try here, here or here) so won’t repeat it here. I must say though that although these products are often claimed to contain “toxic chemicals”, reviews of the literature repeatedly find that these products are safe to use, even on young children.

The patch that makes you invisible to mosquitoes!

This week, a new mosquito repellent formulation/device was grabbing headlines. The  Kite™ Mosquito Patch repellent is currently a runaway success on crowd funding website Indiegogo. Their website is here. At the time of writing, they’d already raised close to US$190,000. That is a lot of money. If nothing else, it demonstrates the willingness of the community to support the development of new approaches to reducing the burden of mosquito-borne disease.

The promotional video for Kite™ Mosquito Patch campaign can be seen here.

The developers claim:

Kite™ Mosquito Patch is a small, powerful patch that allows humans to go virtually undetected by mosquitoes for up to 48 hours. Kite’s compounds act as a non-topical, spatial repellent, blocking mosquitoes’ ability to detect carbon dioxide – their primary method of tracking human blood meals. Indiegogo

Firstly, it would be fantastic if this worked. One of the biggest obstacles to the effective use of repellents is the need to apply a topical formulation correctly, as well as overcoming any actual or perceived unpleasantness of using any of the currently available formulations. If there was a “stick on” device that protected an individual or household from mosquito bites, it would go a long way in our battle to reduce the burden of mosquito-borne disease.

It is important to note that the developers state on their website that Kite™ Mosquito Patch is not a substitute for bed nets, rather it is an alternative product to topical repellents.

With regard to the Kite™ Mosquito Patch, I’m a little skeptical as to how effective it will be outside of the laboratory. I hate to sound negative about this but from personal experience, I have not tested a “spatial” repellent that worked effectively in a field-based situation. Even in a laboratory setting, a small device worn on one part of the body won’t provide “whole body” protection against bites. A number of reputable organisations have provided funding to the various stages of this product’s development so it isn’t fair to dismiss their claims too quickly. However, in the absence of published laboratory trials, it is difficult to make an assessment of just how effective this “spatial repellent” product will be.

Products claiming to be “spatial repellents” such as mosquito coils and sticks offer some protection if they contain insecticides (and therefore “knock down” of near by mosquitoes) but there is growing opinion amongst experts that these provide only limited protection against nuisance-biting and/or mosquito-borne disease risk. Australian studies have shown that burning devices like this that contain botanical products provide a reduction in landing mosquitoes of approximately 70%. The same study found that a topical application of DEET stopped 100% of landings.

Probably the most exciting development in “spatial repellents” is metofluthrin. This is often called the “smokeless mosquito coil”. Studies have suggested this is a potentially effective tool in controlling dengue outbreaks.

The team behind Kite™ Mosquito Patch claim that the product makes the person wearing the patch “practically invisible” to mosquitoes by blocking the detection of carbon dioxide. It is true that mosquitoes use carbon dioxide, as well as the smell of the chemical cocktail of microbes on our skin, to determine who and where to bite. I’ve written about this here.  This is essentially the same process in play with DEET. It blocks the blood feeding urges of mosquitoes. It essentially makes the person wearing the repellent “invisible” to mosquitoes for various periods of time depending on the concentration of DEET in the specific formulation.

Will this new repellent device work? The team behind Kite™ Mosquito Patch haven’t really provided enough detail in their promotional material to make a good assessment of the effectiveness of this product. I don’t want to tear apart their claims but it is worth taking a look at the processes behind assessing new mosquito repellents.

Taking Australia as an example, any product claiming to repel mosquitoes must be registered with the Australian Pesticides and Veterinary Medicines Authority (APVMA). The APVMA assesses new products for both safety and effectiveness.

Do you just stick your arm in a cage of mozzies?

There are a few different ways to test repellents but one of the most common methods remains the “arm in cage” test. This seems to be one of the methods used by the developers of the Kite™ Mosquito Patch. As this repellent isn’t a topical formulation, they need some alternative strategies to test the methodology.

The shot below is taken from their promotional material. It is a neat idea to test the effectiveness of a repellent without directly exposing researchers to mosquito bites. Similar techniques are used to test the effectiveness of insecticide and/or repellent treated clothing. The team at USDA are undertaking some great work in this area as part of the Deployed War-Fighter Protection (DWFP) Program.

An example of the testing methodology of the Kite repellent as depicted in promotional material. Taken from The Australian.

As I mentioned earlier, without more detail on the laboratory methods, it is difficult to assess the links between the work with Kite™ Mosquito Patch in the laboratory and its application in the field. I appreciate that the promotional video isn’t claiming to be a factual presentation of their laboratory procedures. While the presence of a patch (or the candidate repellent substances), may reduce the number of mosquito bites in the nearby area, what about elsewhere?

In 2011, I published a paper on the testing of mosquito repellent “wrist bands”. These were bands that contained botanical products. The laboratory test results showed that there was a significant difference in the landing rates of mosquitoes (Aedes aegypti) adjacent to the band, compared to “untreated” arms. However, landing rates 10cm away from the band were no different to “untreated” arms. This supports previous studies that have reported similar results with wrist bands containing botanical extracts. We tested a wide range of essential oils from Australian native plants as topical repellents also and found only very limited protection.

When I’ve tested similar products (i.e. devices containing botanical ingredients) in the field, I get the same result. A product that provides some limited spatial protection in the lab, does not provide “whole body” protection under field conditions. I’ve never found them to provide the same level of protection as a DEET-based topical repellent. However, some researchers have found that DEET-impregnated anklets, wristbands, shoulder, and pocket strips do offer some protection against biting mosquitoes in the field (up to 5h).

What mosquito was the repellent tested against?

This may seem a strange question to ask. However, it is critically important. There are thousands of mosquito species worldwide. Some are far more important as nuisance-biting pests than others. Many don’t even bite humans. The vast majority of mosquito repellent tests published in the scientific literature use Aedes aegypti (the dengue/yellow fever mosquito). This is pretty much the lab rat of the mosquito world. It is a great species to work with as it is a day-biting species and has a relatively consistent biting rate. Testing a repellent against Aedes aegypti is pretty much the way to go. In malaria prone regions, testing against the malaria-vector and avid nuisance-biting species Anopheles gambiae is useful too.

If, however, a repellent is tested against a species such Culex quinquefasciatus, a species generally associated with bird-feeding, it is difficult to be confident with the results. We have this species is colony and whenever it is used for repellent tests, we get greatly different results. For example, in our testing of a botanical-based topical repellent, over 200min of protection against Culex quinquefasciatus was achieved but no protection against Aedes aegypti was recorded.

I couldn’t find any reference to the mosquito species used for the lab testing of the Kite™ Mosquito Patch but I’d suspect that they probably used Aedes aegypti.

Does the product repel or protect?

This is a tricky one. What is an effective repellent? One that stops some mosquitoes biting or one that stops ALL mosquitoes biting? Given that it only takes one mosquito bite for the transmission of a pathogen, I believe that a repellent should provide protection from all bites. This is why most published reports contain information on “complete protection time” of candidate repellents. This represents the duration of protection provided by a repellent. It is interesting to note that once a candidate repellent has failed this test (i.e. mosquitoes are actively biting) there may be still be over 80% reduction in the number of mosquitoes landing on treated forearms compared to untreated controls.

A repellent that only reduces the number of bites won’t necessarily prevent disease.

When will we know if the Kite™ Mosquito Patch works?

As the developers state on their fundraising page, field work is to be conducted in Uganda. It will be interesting to see the results. They will certainly have a great funding base to work from. In their promotional video they state they’re testing in the “toughest proving ground there is”. It is true that Uganda has a high rate of malaria. It will be great to see a well designed project that investigates the role of the new repellent device in reducing disease risks. I hope they include other strategies as well including bed nets and insecticides as well to determine what works best.

If they really want to test the Kite™ Mosquito Patch with regard to protecting against mosquito bites, they are welcome to get in touch with me. Some of my study sites have huge populations of the saltmarsh mosquito Aedes vigilax. If the repellent patch works in those situations, it really will be a game changer!

In summary, I would like to remain optimistic about the Kite™ Mosquito Patch. Despite all the technology at our finger tips, the burden of mosquito-borne disease internationally remains a significant health problem. Along with a range of strategies, new mosquito repellents will definitely play an important role in reducing public health risks internationally.

I’ll look forward to reading about the results of the Uganda field tests in the months ahead!

Busting five myths of mosquito repellents

After 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!

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.

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Read more at The Conversation: Are mosquito coils good or bad for our health?

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Read more at The Conversation: What can I eat to stop mosquitoes biting me?

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Read more at The Conversation: The best (and worst) ways to beat mosquito bites

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Taking the taste test with MyScience

How can coloured plates and sour lollies teach primary school students about science?

For the second year in a row I volunteered in the MyScience program. The program began  in 2006 as “a collaboration between the University of Sydney, the Australian Catholic University, IBM and the NSW Department of Education and Training (Western Sydney Region) to fulfill their common goals of improving primary science education and encouraging students to take an interest in science and technology”.

The program encourages professionals with a science and/or technology background to volunteer in a local school to help teach primary school students about the process of scientific experimentation. It is designed to help the students turn their minds to the process of developing testable questions about how the world works and to try and design experiments to investigate these questions. As does the CSIRO Scientists in Schools and Australian Academy of Science’s Science by Doing programs, MyScience aims to introduce the world of science and technology to school students and encourage them to become the next generation of researchers and innovators. If the calls for scientific research to become a national priority are answered, we’re going to need to ensure that there is a steady flow of “bright young minds” forming the next generation of scientists.

The theme for MyScience this year was food. Unsurprisingly, most the experiments revolved around lollies/candy/sweets. In particular, skittles and warheads. Don’t ask me why but the kids love warheads. If you’re not familiar with them, they’re a hard sweet ball covered in the most sour tasting substance imaginable.

I supervised four pairs of Year 4 students (aged 9-10), each had to come up with a question about food and work out an experiment to test that question.

There were two particular projects that worked out really well.

The first was looking at how plate colour influenced volunteer’s choice of food. There are specific fields of science dedicated to this kind of research. Researchers have looked at how food colour, as well as plate colour and shape, influences the perception of taste. Even the type of cutlery can make a difference! Is colour-related food choice inherited or developed through empirical learning? An experiment like this, as well as providing an opportunity to do some neat experiments, may provide an opportunity to discuss the issue of food packaging and marketing.

The students laid out three colour plates, each with a group of lollies. While I tried to encourage the students to use sliced apple as the “food”, I quickly realised it was a battle I wouldn’t win. The students then recruited their class mates to line up and take turns selecting the plate from which they would like a lolly. The number of times each coloured plate was selected was then recorded.

It probably comes as no surprise that most volunteers chose lollies from the red plate. This is actually in line with some published studies. Studies have suggested that foods with green labels are perceived to be healthier but I’m not sure if that means that “unhealthy food” is more likely to be associated with red! It does seem that colour pays an important role in food choice by children.

The best thing about the experiment was that the students really were excited to see that there was a difference in the selection trends of their volunteers. As the sample size grew and the trend become more pronounced, they got even more excited. In the end, it was a nice clear cut experiment that allowed them to make a nice simple chart of results to present to their class.

The second experiment was more of a demonstration that a true experiment. The real focus of these students’ question was to determine if sour lollies were more sour than sour fruit. They asked volunteers to taste one of the sour lollies, and then a piece of lemon, and pick the most sour. The students didn’t place too much emphasis on gathering a decent sample size. They stopped at three volunteers. While they may not have been quite as enthusiastic about the first part of the experiment, I took the chance to work up a demonstration to teach them about food acid and how it relates to taste.

Warheads are dusted in malic acid (dicarboxylic acid). When you suck them, there is an intense sour taste that lasts about 30sec. How could you demonstrate that it is the acid that causes the sour taste and why does it stop?

I made up two solutions of sodium bicarbonate (roughly 1 teaspoon of bicarb mixed into 50ml of lukewarm water). If you drop a freshly opened warhead into the solution, it fizzes up and looks reasonably dramatic. Next, one of the students takes another freshly opened warhead and sucks it until the sour taste is gone. Now drop that “sucked” warhead into the second solution. No bubbles. No fizz.

While this may seem like a fairly basic demonstration, the students were generally excited and during their science fair, it was one of the most popular demonstrations of the morning. This was probably due in part to the joy of watching teachers and parents enduring the sourness of the warheads in front of the students!

Overall, the My Science program has benefits both for the students but also the volunteers. I’ve found that breaking down the process of experimentation and thinking about how to explain concepts to primary school students greatly improves the way I approach communication of “medical entomology” issues to the general public and media. If an eight year old can understand my explainations, I’m hoping everyone else can too.

Australian Mammal Society Conference

On Tuesday 9 July I’m presenting some work at the Australian Mammal Society conference at the University of NSW. The title of my presentation is “The role of macropods in mosquito-borne disease: Implications for urban development and wetland rehabilitation” (my coauthors are Stephen Doggett (Medical Entomology, Westmead Hospital) and Mark Ferson (University of NSW/NSW Health).

Ross River virus causes around 5,000 cases of reported human disease every year but, as the symptoms can sometime be mild, the official data is probably an underestimate. The role of Australian wildlife in mosquito-borne transmission cycles is often overlooked. The emphasis is generally placed on mosquito populations and their relationship to environmental drivers of population abundance. We have some very good data on the types of mosquitoes responsible for transmitting RRV thanks to detection of the virus in wild caught mosquito populations and “vector competence” experiments in the laboratory.

There have only been a few studies looking at the role of wildlife. These studies have included serological surveys, isolation of pathogens from wildlife and laboratory studies investigating the titre and duration of viremia in infected animals. These studies have helped identify macropods as some of the key reservoir hosts of RRV in coastal Australia. However, we still don’t know much about how the local wildlife, mosquitoes and pathogens interact under the influence of local environmental and climatic conditions. In particular, how does the ecology of local macropods influence local mosquito-borne disease risk? To be even more specific, how may the conservation strategies of local wildlife at the urban fringe influence public health risks?

If you’d like to read more about RRV, there are two very good review papers here and here. For more on mosquito risk associated with urban development, see my piece here.

My presentation will concentrate on mosquito abundance and diversity, as well as the activity of mosquito-borne pathogens, from two estuarine river systems in Sydney. The Parramatta River and Georges River systems contain comparable mosquito habitat dominated by estuarine wetlands (i.e. saltmarsh and mangroves) but support very different populations of macropods. There aren’t any macropods along the Parramatta River. What we’ve found by studying these two systems can be used to assist in urban development plans where wildlife conservation may require increased awareness of mosquito population management.

Of course, I’m not suggesting that the conservation of macropods isn’t important. The point here is that local authorities must be aware that in regions where there are opportunities for interactions between mosquitoes and wildlife (particularly kangaroos and wallabies), public health risks will be higher. Increased mosquito populations in association with newly constructed or rehabilitated wetlands, particularly in urban areas, may risk only increase nuisance-biting impacts. However, at the fringes of our cities, the risks of disease caused by pathogens such as RRV must be considered. In these circumstances, mosquito management strategies should be more carefully considered.

The full abstract of my presentation is below:

Mosquito-borne disease risk in coastal regions of Australia is a concern for local authorities. Many gaps exist in our understanding of the drivers of mosquito-borne disease risk, particularly with regard to the role of interactions between mosquitoes and wildlife. Macropods have been identified as important reservoir hosts of mosquito-borne pathogens and the presence of kangaroos and/or wallabies is a critical factor in driving outbreaks of disease. What are the implications for urban development and wetland rehabilitation projects? To investigate the role of macropods in urban mosquito-borne disease outbreaks, mosquitoes and activity of Ross River virus (RRV) was investigated in two estuarine wetland systems in Sydney. The abundance and diversity of mosquitoes produced by the estuarine wetlands along the Parramatta River and Georges River are similar with the dominant mosquito Aedes vigilax. There are no macropods are present along the Parramatta River. Few isolations of RRV have been detected along the Parramatta River but significantly higher rates of RRV (as well as other mosquito-borne pathogens) have been detected from mosquitoes collected along the Georges River. In addition, public health investigation confirmed local acquisition of RRV disease in residents living along the Georges River. No locally acquired RRV disease has been confirmed from the Parramatta River region. The use of natural bushland wildlife corridors along the George’s River by macropods is increasing local disease risk in that region. The results have implications for urban planning where wetland creation and rehabilitation, as well as wildlife corridors, may increase local public health risks.

The full program for the Australian Mammal Society conference is available here.

UPDATE: There was a nice article by Nicky Phillips in the Sydney Morning Herald on 13 July covering this story too “Urban kangaroos, wallabies harbour Ross River virus“