By Dr Eddy Bajrovic*
Dr Cameron Webb is the man the Travelvax Report turns to for his expert knowledge of insects – especially the ones that bite.
There’s not much the Sydney-based entomologist doesn’t know about mozzies, including the two disease-carrying Aedes species that are spreading to every corner of the world’s tropical regions.
After reading last week’s article advising Year 12 students about to head overseas for schoolies or a gap year, Dr Webb had some keen observations to share.
Indeed, they’re relevant for travellers of all ages.
Besides the vaccinations we recommended for travel to developing countries, he says there are a couple of other major differences between overseas schoolies (and holiday) destinations like Bali or Fiji and local ones like Queensland’s Gold Coast that Australians often don’t appreciate.
Among them, the consistent risk of the mosquito-borne viruses, dengue and chikungunya and the very ‘un-Australian’ biting patterns of the aggressive mozzies that spread them - Aedes aegypti (also known as the ‘Yellow Fever mosquito’) and Aedes albopictus (the ‘Asian Tiger’).
Two very un-Aussie mozzies
“Aussie travellers are used to Aussie mozzies,” Dr Webb said.
“Here they mainly bite in the late afternoon and evening.
“So, when Australians travel to the tropics they often don’t realise that the distinctively banded Aedes mosquitoes bite from first light and right through the day.
“These mosquitoes aren’t found in wetlands. They emerge from water-holding containers and are as close as the balcony or gardens of your resort or hotel.
“All travellers need to remember to apply an effective insect repellent to all exposed skin before they head outside their hotel room each morning and to carry it with them so it can be re-applied during the day – especially after a swim or sweating a lot.
“And, if you’re still outside at sunset, it’s smart to refresh the repellent and cover up with long pants and shirt, and shoes and socks.”
We’re the ‘specials’ on mozzie menu
Dr Webb believes so many Australians are returning infected with dengue (almost 1500 cases so far this year) and chikungunya (almost 100 cases) because the life cycle of the Aedes mosquitoes that spread them are perfectly in ‘sync’ with humans. We are their favourite source of the blood meal the females need to lay eggs.
“These mosquitoes prefer us to animals,” he said.
“When an infected female takes a blood meal, she transfers the virus in the process.
“She will later breed close to that source of food in any container that holds even a small amount of water – a pot plant saucer, an old car tyre, a rainwater tank, or an uncovered water drum.
“Ironically, our discarded takeaway food containers, and bottles and cans, are probably the most likely mosquito breeding sites.”
Local incursions are increasing
When you compare the number of local cases of the two diseases, chikungunya may not seem that high.
That is, until you realise that until 2013, the highest number of cases previously was only 62 in 2010.
The majority of dengue infections reported in Australia occurred in Indonesia and each summer imported cases trigger local outbreaks in Far North Queensland (FNQ).
Local mosquitoes typically pick up the virus by biting an infected traveller and then pass it on to locals. There have been about 30 cases of locally acquired dengue in FNQ this year.
Infected mosquitoes have even hitched a ride on aircraft, resulting in suspected cases of ‘airport dengue’ in the Northern Territory and ‘baggage dengue’ in Western Australia.
Dodging bites takes a little effort
A holiday totally free of insect bites is difficult to achieve – especially in tropical or sub-tropical destinations, where breeding conditions are ideal for much of the year.
But, it’s important to reduce your risk by reducing the number of bites.
So…
Pack a repellent that works: To be effective, your repellent needs an active ingredient that really works, such as DEET, Picaridin, or oil of eucalyptus (also known as PMD). DEET formulations containing 40% active ingredient will protect for 6 hours, sufficient protection for most holidaymakers. (Products containing around 20%-30% DEET protect for over 4 hours, while 10% formulations provide at least 2 hours of protection.) Picaridin and oil of eucalyptus are equally effective and safe: A 20% Picaridin formulation will protect for around 4 hours, while oil of eucalyptus will last for up to 6 hours. For children… lower-dose repellents are suitable for littlies as young as 3 months of age. ‘Low-dose’ DEET-based repellents have been supplemented by Picaridin-based ones. Applying repellent should be done by an adult and if your child has a skin condition, check with your doctor on which product is the most suitable. Wash repellent off kids when it’s no longer needed each day.
Use repellent with care: Apply a thin coating of repellent to exposed skin only, avoiding the eyes, mouth, wounds, or rashes. For children… Peak-time protection is particularly important for kids – they’re less aware of the dangers mozzies can present and generally make an easy target for all biting insects. And, don’t forget to pack a light gauze netting to protect babies in strollers.
Seek and destroy: Mozzies can breed in very small quantities of water and they generally don’t travel far from where they hatch: less than 200m. When you arrive, turn over or remove anything that can hold water on balconies and in gardens – a job kids can help with!
Some things just don’t work
When it comes to avoiding mozzies and other biting insects, we know some things simply are not effective, including:
- Wristbands.
- Mozzie-repelling phone apps.
- ‘Natural’ alternatives to DEET, Picaridin, or oil of eucalyptus-based formulations. (These are unproven and are far less likely to be effective for even a short time. In addition, some plant-based repellents need to be reapplied much more frequently than products made with the three proven active ingredients.)
- Taking vitamin B. (It doesn’t prevent bites. In fact, there is no evidence that anything you can eat, drink or swallow will shield you from being bitten.)
- Burning mosquito coils and sticks. (At best, these may reduce the number of bites, not completely prevent them. Never burn these indoors overnight in an enclosed room.)
While there are products that combine sunscreen and insect repellent, it’s best to keep them separate. Apply sunscreen at least 20 minutes before going outdoors, then apply repellent over the top just before you go out. Reapply each as required.
Before you fly…
Forewarned is forearmed.
Find out if there are likely to be mozzie diseases or other risks at your destination by calling Travelvax Australia’s travel health advisory service on 1300 360 164 (toll-free from landlines).
You’ll not only get no-obligation advice over the phone, but you can also make an appointment for a one-stop pre-travel medical consultation and any vaccinations needed for the trip from medical professionals experienced in travel medicine at a Travelvax Australia clinic near you.
* Dr Bajrovic is Medical Director of Travelvax Australia.