From bruises to blood donation, menstruation to mozzies, the first season of It Can’t Hurt To Ask focuses on blood.
Are you the main mozzie attraction at a barbeque, coming home with dozens of bites? Or have you had the unfortunate experience of contracting a mosquito-borne virus?
Regardless of your history with mozzies, all Queenslanders need to know how to minimise their exposure to mosquito bites. In this episode, senior medical entomologist Scott Lyons, medical entomologist Brian Montgomery and Queensland’s Chief Health Officer, Dr John Gerrard, take us through why mozzies bite, why the bites can be so irritating, which viruses Queensland mosquitoes might carry and most importantly, how to avoid them.
There’s also a neat science experiment you might be able to get involved in, and a few mozzie myths to bust, like whether mosquitoes really do prefer some people over others, and how different mosquito repellents work.
Featured in this episode 
Scott Lyons
Scott Lyons is a senior medical entomologist at the Townsville Public Health Unit and he’s been working in the world of mozzies for 12 years. An entomologist works with and studies insects, and a medical entomologist works with insects that cause disease in humans. Scott’s role involves a lot of field work, travelling thousands of kilometres to trap, test and study mosquitoes right across the north of the state.
Brian Montgomery
Brian Montgomery is a medical entomologist at Metro South Hospital and Health Service. Like Scott, he worked for many years in northern Queensland, before coming to Brisbane. Compared to the north, he was surprised by how little mozzie monitoring was implemented in urban areas, and now leads the Zika Mozzie Seeker program, which coordinates members of the public trapping mosquitoes and their eggs for Brian’s team to analyse and predict the risk of Zika virus carrying mosquitoes in the local area.
Dr John Gerrard
Dr John Gerrard is Queensland’s Chief Health Officer. He’s dedicated his career to treating patients with infectious diseases, like the ones that can be transmitted through Queensland’s mozzies, figuring out how diseases spread, how to slow the spread and how to effectively treat patients.
Episode resources
Mosquito-borne viruses
In this episode, we discuss a number of mosquito-borne diseases, including Ross River fever, Dengue virus, Barmah Forest virus, Japanese encephalitis virus and Zika virus. You can find more information about all of these diseases from Queensland Government - Health and Wellbeing.
Zika Mozzie Seeker page
In this episode, Brian talks us through the Zika Mozzie Seeker program. If you’re interested in learning more, or live in the Metro South catchment and want to take part, visit the Metro South Zika Mozzie Seeker page.
How to protect yourself properly using mozzie spray
Did this episode make you question whether you’re protecting yourself from mosquitoes properly? Our blog, Are you using mosquito repellent incorrectly?, will take you through the steps you need to know for best protection.
Transcript
Vox pops: How do mosquitoes spread viruses?
Why am I always the one that gets bitten?
How long do mozzies live for?
What makes their bites so itchy?
Narrator: Welcome to It Can’t Hurt To Ask, the podcast from Queensland Health exploring all your health questions, concerns and curiosities.
This season, we’ve been looking at all things ‘In My Blood’. And today we’re buzzing around the state to learn more about mosquito-borne viruses.
Hi, I’m Lauren and this episode was recorded on the lands of the Jagera and Turrbal people. We acknowledge the Traditional Custodians and pay our respects to the Elders past, present and emerging.
Remember, whatever you hear in our episodes is general information. Always speak to your doctor about your individual circumstances.
Ready? Let’s get into it.
Narrator: Picture this – you’re sitting outside, enjoying dinner with some friends or family. The air is warm, even as the sun sets. And then you hear it. Or feel it. The faint buzz in your ear. That sudden itch on your arm, or leg, or ankle.
A mosquito bite.
A small flying insect that bites people and animals, Queensland is home to around 300 different types of mosquitoes. Or ‘mozzies’ as they’re affectionately known.
Most often, you might just get an annoying bite that’s red or itchy for a little while. But these flying blood suckers can carry diseases you can catch if you are bitten by an infected mosquito.
To learn more, let’s meet our first expert.
Scott Lyons: My name's Scott Lyons and I'm the senior medical entomologist here at the Townsville Public Health Unit. I've been here in this role about 12 years.
Narrator: An entomologist is someone that works or studies insects of all types. A medical entomologist works with any insects that can cause diseases in humans like mosquitos and biting midges.
From Brisbane to Cairns and now Townsville, Scott has studied mozzies for over 20 years.
Which means he’s a great person to explain why mosquitoes need us humans. And why do they bite?
Scott Lyons: Mosquito life cycle goes from an egg to a mosquito larvae so they have got to live in water and once they hatch out of the water, first thing they will need to do is find a mate so then they will mate, and then they will need food.
So, the male mosquitoes will feed on, females as well, on flowers and things like that, getting a bit of flower nectar and that for the sugars, and the females will need some sort of protein for their eggs. So that's either animal blood or human blood, depending on the species.
Narrator: In fact, it’s actually just the female mosquitoes that bite. That’s because female mosquitos need the ingredients found in blood to lay their eggs. So for a mosquito, the business of blood sucking is a life-or-death situation. Without a blood-rich diet, the circle of life for mozzies would cease entirely.
Scott Lyons: And so when they come to bite you they stick their proboscis into your skin and they'll use their saliva to make the blood flow a little bit better.
Narrator: Hold up... a proboscis? Yep, a proboscis is the proper name for the extended mouthpart that mosquitoes have and use to suck out blood.
Scott Lyons: So, they'll suck the blood out, digest that, protein will help the eggs and then they'll lay their eggs and then they'll probably survive about two weeks in good conditions, and then lay their eggs either in water or close to water.
Narrator: Then the cycle begins again.
The mosquito’s saliva is important. That’s what carries and transmits any virus the mosquito is carrying from mosquito to human. It’s also what makes you feel itchy. The saliva also anticoagulates your blood. If you listened to our episode about how blood works, you’ll remember coagulate means clotting, so anticoagulate means to stop clotting. So the saliva prevents the blood from clotting, meaning a more steady flow of protein for the hungry mosquito and their eggs.
All mozzies need water to complete their lifecycle, which means they can be found in a variety of environments.
Scott Lyons: Along the coastal areas when you've got a lot of wetlands and mango marsh areas you'll have sort of constant mosquito issues for most of the year.
Through the inland parts, the northwest parts it's more seasonal with the obviously you get a lot of rains and a lot of floods out there. The landscape's really flat so the water will sit for quite a long time, and so the mosquitoes have a lot of time to breed up, so you'll have these big outbursts of lots and lots of mosquitoes after the flood type activities.
Mostly if you're spending a lot of time outdoors, working outdoors, you'll be more at risk of getting bitten by mosquitoes. A lot of people go up that way fishing and hunting and camping and things like that and spending a lot of time outside.
Narrator: Someone else who knows a lot about the subject is Queensland’s Chief Health Officer.
Dr Gerrard: My name is Dr. John Gerrard I'm the Chief Health Officer of Queensland and I have a background in clinical infectious diseases. Most of my career has been, been spent treating patients with infectious diseases of various sorts.
I guess if a normal doctor is responsible for the health of the person that's in front of them making sure they are well, I'm ultimately responsible for the health of every Queenslander and any risk that might confront any Queenslander. So, my patients are the whole state of Queensland, which is a bit daunting.
Narrator: Ever stood in a group of people, and wondered why one person gets targeted by mosquitoes while others leave completely unscathed?
There are a few factors that make certain people more attractive to mozzies than others.
Dr Gerrard: The mosquitoes are attracted to us through a number of mechanisms. That's carbon dioxide that we emanate, but also smells from our body. Various chemicals in our skins, like lactic acid is one. But there are various chemicals that attract mosquitoes to bite us and to suck on our blood to help produce those eggs.
Narrator: Hard to take as a compliment, right?
However if you are, like me, the person that always seems to come away with the most bites, there is one potential bit of good news.
Dr Gerrard: There is actually some evidence that if you if you react strongly to mosquito bites, you're less likely to get mosquito-borne virus disease. That's probably because people who react strongly to mosquito bites avoid getting bitten by mosquitoes.
Narrator: This makes sense – if you’re familiar with the painful or uncomfortable sensation of frequent mosquito bites, there’s an extra incentive to be more proactive in protecting yourself. As a result, you reduce your risk of being exposed to a mozzie-related virus.
If you don’t react badly, then you might be more relaxed about using a repellent or wearing protective clothes – and be at greater risk.
As for treating those bites, Dr Gerrard says a simple cold compress or some calamine lotion is the best way to reduce the itch.
Narrator: For a mosquito to transmit an infection, it has to have bitten an animal or human that is infected with a disease. Let’s hear from Scott on this.
Scott Lyons: It can't get spread by coughing or things like that or touching people. It has to come from the blood. So the mosquito has to bite you, suck your blood out, and pick up a bit of that virus, and then it'll go, the virus will grow in the mosquito. It takes maybe between four and seven days in the mosquito and it goes up into their saliva glands and then when they bite the next person spit out the virus with the saliva into the other person's blood.
Narrator: Not all mosquitoes carry viruses, but there are a number of mosquito-borne viruses that we see in Australia.
These include Ross River and Barmah Forest Virus, which are very similar to each other.
Higher rates of disease are commonly seen when we experience lots of rain, which in Queensland is typically in the first few months of the year.
Dr Gerrard is back to tell us more.
Dr Gerrard: The commonest mosquito-borne virus we would see would be Ross River fever. Probably about a thousand people per year in Queensland are diagnosed with Ross River fever. In fact, it's probably many more that actually get it because it can be a very mild illness with very minimal symptoms is never recognised as Ross River fever and it varies in severity from mild to quite severe.
Narrator: Ross River is a native Australian virus that mainly lives within mosquitoes, possums and other marsupials. It doesn’t affect the animals and just circulates through them. But for humans, it can make us quite unwell.
Dr Gerrard: The symptoms typically include fever and joint pains, typically involving multiple joints, including the small joints and in your hands and elsewhere in your body. And that can last anywhere from a few days to a number of weeks. And some people get up post-viral fatigue syndrome lasting a few months afterwards. But for the most part, it's actually a quite mild illness and it's often unrecognised.
Narrator: When we say unrecognised, we mean that when people experience these symptoms they may assume they have something else, like the flu.
There is no specific treatment for Ross River Fever. The good news is that most people recover on their own, ranging from within a few days to a few weeks. In some cases, it may take a few months to recover completely.
The main way we can diagnose mosquito-borne viruses is through a blood test.
Japanese encephalitis virus, also known as JEV is another mosquito-borne virus that we’ve heard in the headlines more recently.
It was detected in 2022 in humans, mosquitoes and pigs across multiple states in Australia. That year, there were five locally acquired human cases reported in Queensland. Before this, the last locally acquired case reported was in 1998 in Far North Queensland.
Dr Gerrard: The Japanese encephalitis is of concern because it can cause a much more serious illness than Ross River virus. Including encephalitis, which causes severe headache, sometimes with seizures and sometimes leading to death. So, it can be a very serious illness.
Narrator: JEV is only spread through the bite of a mosquito. So, it can’t be spread person to person.
Dr Gerrard: We know the virus can amplify in both wild pigs and domestic pigs, but it seems, particularly in areas where there are domestic pigs, that where we have seen Japanese encephalitis virus. So that's particularly sort of just west of the divide in the Darling Downs area is the high, where the biggest number of piggeries are.
And it's not just people in immediate proximity to the piggeries, it's the whole region that can be affected. So, we've been recommending that people who spend a lot of time outdoors in in these areas receive a vaccine against Japanese encephalitis. And avoid getting bitten by mosquitoes, which is, you know, that's clearly the single most important thing we can do to prevent mosquito-borne virus disease.
Narrator: Given the risk of these viruses to our health, there are public health programs designed to monitor and test mosquito activity.
Let’s go back to Scott, the medical entomologist in Townsville we met earlier, who has played a key role in one of the programs monitoring JEV activity in north Queensland.
With a new virus, we need to learn how it reacts to our Australian mosquitoes and the population.
The team started monitoring for JEV in November 2022, finishing their last round of trapping in June 2023.
Scott Lyons: The idea is the Japanese Encephalitis virus probably migrated from north of us. So it would have passed through, usually through migratory birds following flood waters before they're further south. So whether it's moved or as it's gone through, it stays in other regions. It just stays in nature. It circles around wild birds, wild pigs and things like that. It doesn't need a human host.
Narrator: The team end up covering thousands of kilometres driving as they travel town to town setting up traps, making their way north towards the Northern Territory border.
Scott Lyons: We've got a team of four people here and so we work in pairs and we'll load the car with about 10 traps which are baited with carbon dioxide which the mosquito thinks it's somebody or animal breathing, with the carbon dioxide and that attracts them into the trap and it has a little fan inside it and it sucks them into the container. And so we set them overnight and come and collect them the next day and we'll do that for a couple of nights. And yeah stay a few nights in each town and drive on to the next one.
Narrator: When they arrive in Brisbane, the mozzies are crunched up and tested for viruses. This is done through a PCR test, or a Polymerase Chain React Test, which detects the presence of the genetic material of a particular virus.
Narrator: In the 2022-23 wet season, Scott and the team deployed 216 traps across North and North West Queensland. No Japanese Encephalitis Virus was detected.
While the work is ongoing, we don’t have to look far to see the impact these kinds of monitoring and programs have.
The rates of Dengue fever have been significantly reduced in North Queensland thanks to a similar program. It's considered one of thebiggest advancements in the prevention of mosquito-borne disease not just in Australia, but worldwide.
In fact, Scott was involved in this one too!
Scott Lyons: Another project or another thing that's happened over the last few years is the introduction of the Wolbachia bacteria, which we're working with the World Mosquito Program. They introduce the bacteria into the mosquito and that bacteria in the mosquito will stop dengue virus living in the mosquito so they can't transmit it.
So, we've been working with them to...I guess kind of just displace the wild type natural stray mosquitoes with this new strain that has the bacteria in them. So, the dengue mosquitoes in most of North Queensland now can't actually transmit dengue.
Narrator: Pretty impressive, right?
Not all mosquitoes can carry all diseases. So certain species are associated with certain viruses or illnesses.
Scott Lyons: So with dengue there's only in Australia two species of mosquito that can carry it; the Aedes aegypti and Aedes albopictus which is up in the Torres Strait area. It's not found on the mainland of Australia. So, they're the only two mosquitoes that can transmit dengue and that mosquito will only bite humans as well, so it won't bite any other animals.
Narrator: We’ve heard about how we monitor mozzies in some of the more rural and regional areas of Queensland. What about the urban areas in our major cities?
Brian Montgomery: My name is Brian Montgomery. I'm a medical entomologist from Metro South Health. I spent many years in north Queensland coordinating dengue response outbreak. And I moved to this role in 2010 and was quite surprised at the lack of urban mosquito monitoring for those sorts of mosquitoes which are capable of spreading exotic diseases.
Narrator: 70% of Queenslanders live in South East Queensland. So if there were mosquitos spreading diseases in these areas, that’s lot of people at risk.
It was this realisation following the emergence of Zika in 2016 that led to Brian establishing the Zika Mozzie Seeker program at Metro South.
When we say Zika mozzies we’re actually referring to two different types grouped together, The first is the Dengue mosquito, Aedes Aegypti who we met before. The second is the Asian tiger mosquito, Aedes Albopictus.
With both these mosquitoes present around the state outside of the South East Queensland area, a Zika outbreak would technically be possible.
With 220 suburbs to cover in the Metro South area alone, Brian quickly realised he was going to need some help.
Zika Mozzie Seeker calls on the community to get involved and help Brian and his team better understand which mozzies are buzzing round our gardens – and if they’re carrying diseases like Zika that pose a threat to our health.
Volunteers like you, if you live in the area, collect the mosquitoes and then the public health system counts, identifies and tests them.
And it’s simpler than you might expect. All you need is a bucket of water left outside and an egg collection kit that’s posted to you once you sign up. Leave it for a couple of weeks, and then post your results back to the team in a provided and pre-paid ziploc bag and envelope.
Brian Montgomery: So, you know, setting up a trap is very simple. We put all the components in there, and they're not complicated. A bit of blotting paper, paper tape for the mosquitoes to lay eggs on, a paper clip for you to put the tape on the side of your bucket and a little bit of lucerne pellet, which is basically rabbit food.
So, over the process of two or even three weeks, while your bucket is forgotten in the background, the mosquito is smelling that and going there and hopefully laying some eggs there so that after that two or three weeks you will send in the tape, which is in the egg collection kit.
Narrator: Like many insects, the success of mosquitoes breeding depends on the weather and other environmental factors. Take a warm climate and a rainy season, and you have, a perfect storm - and a much bigger mozzie population.
When it’s dry, mozzies are very sneaky, with their eggs able to survive 6 to 12 months totally dry.
Given there are mosquitoes in Australia, it’s highly likely you’ll get eggs in your trap. But what you or even Brian can’t tell until further testing is whether they’re the Zika mozzies.
Brian Montgomery: So, what I do with it is I open up your envelope and first thing I do is I look at it for eggs or not eggs. So, the no eggs go into one bundle and the strips with eggs go into another bundle.
I thought it'd be nice if we had a way to actually have a fairly good estimate of how many eggs are at your place. So what we have developed here is a web cam which gives a, you know, a pretty good guess or estimate about how many eggs are on your strip.
Brian Montgomery: And then we pair that with the batch. So, we put about 25 strips into one molecular screening test, so it's a very efficient way for us to look for the target species that that molecular test will see one egg in 5000 of the local species.
So far, the last five or six years we've screened getting close to half a million eggs and have yet to find the Zika mozzies.
Narrator: Brian says results like this that find no presence are important because they show “a refresh of absence”.
Especially when we’ve seen the impact of these invasive Zika mosquitos in other parts of the world like America and Europe.
Brian Montgomery: It's an extremely concerning virus because most people won't know they have Zika. So, what we say is it's asymptomatic. But what we saw in the Brazil context is that pregnant mothers that were infected with Zika run the risk of having either babies that die or have permanent brain damage by having these, you know, affected brains.
So, the motivation for me is to say, if we know it's invasive, we have to be looking more than once in a while. And the old style of looking for these mosquitoes would would be that we'd have to get a whole collection of mosquito inspectors coming to your yard.
Narrator: Like the JEV detection program, the Zika Mozzie Seeker Program can’t represent the whole area. But it’s hundreds more samples than we would normally have.
And while we haven’t had a broad scale invasion yet, it drives home the importance of detecting any presence or disease in the early stages to increase the chances of eradicating it.
And what would happen if you did test positive to a mosquito-borne virus through a blood test?
Brian Montgomery: So, we will be advised through our national system that you have arrived in Metro South and it will identify the virus that you have. And then that's the next part is to decide do we activate our response?
For things like Ross River and Barmah Forest, there is no response because it's in the background all the time. If we saw large numbers of people presenting with symptoms in the same season, you might see that story come on the in the public media where it might be, please cover up against mosquito bites.
But by the time you know you have Ross River or dengue, the mosquito that bit you is already dead. So it's always challenging. But the health system is designed that if you present and get a blood test, we will be notified that you have that disease.
Narrator: If it were an exotic disease that confirmed the presence of zika mosquitoes, a specialised public health programwould be triggered. This is based on previously successful programs, like the dengue-control methods in North Queensland we heard about earlier.
So how can you best protect yourself from mozzies when you’re out and about?
Check your backyard and make sure there’s nothing holding water.
If you’re outdoors, mosquitoes are most active at dusk and dawn, when it’s not too hot or cold for them.
They’re often attracted to dark clothing, so wearing loose-fitting, long-sleeved and light-coloured clothing can help. Close-toed shoes will also help protect your feet.
Repellents with appropriate Australian credentials are also your best line of defence. Ingredients to look for are either DEET, Picaridin, or eucalyptus extract – and it must be applied properly.
It’s a common myth that you can apply it once and you’re set for the rest of the day or night. You need to reapply every few hours as instructed.
Brian Montgomery:
If you're using a gel or a cream, that's going to last longer than if you use a spray. And applying, say, a repellent to your wrist won't stop the mosquitoes biting your elbow. So again, it's this concept you have to spray or distribute the repellent across all your exposed skin surfaces is the trick.
Narrator: As usual, let’s finish up by busting a few final mozzie myths. How long do you think mosquitoes live for? A few hours? A couple of days? Months or even years?
Brian Montgomery: A lot of people may have this idea that mosquitoes are long lived, but typically two weeks is an old mosquito. And you know, the reason they don't live very long is I guess it's a very dangerous environment. Maybe the Zika mozzies might be able to live a little bit longer when the climate is cooler.
Narrator: Thank you for listening to this episode of It Can’t Hurt To Ask.
We’ve learnt why mozzies bite, how they can spread diseases and how public health in Queensland monitors mosquito activity to prevent outbreaks.
Thank you to Dr Gerrard, Scott Lyons and Brian Montgomery for sharing their expertise with us. If you want to be part of the next round of the Zika Mozzie Seeker program, we’ve added the link in the description of this episode.
We’ve got loads more blood-related topics coming up this season, with new episodes dropping every Wednesday.
If you enjoyed this episode, please rate or review. Even better, tell or share with a friend, family member or colleague who you think would also enjoy this episode .
Until next time, goodbye. And remember, it can’t hurt to ask...