By Dr Eddy Bajrovic*
Last week, I stressed that travellers need to be wary if they develop a fever after visiting a tropical country.
It might be malaria, which can sometimes be rapidly fatal without urgent medical treatment. Each year, around 500 Australians return home with the mosquito-borne parasite multiplying in their blood.
However, the dengue virus has become a much more common cause of post-travel fever, with 1427 confirmed cases here to date this year – most of them imported from Asian countries. (Mind you, these are just a tiny fraction of the estimated 390 million annual cases of dengue that occur in 128 countries where 3900 million people are at risk of infection, according to World Health Organisation data.)
While dengue has conquered the world in the past half century, two other mozzie diseases are now hot on its trail. The chikungunya and Zika viruses are also entrenching themselves in tropical Africa, the Asia-Pacific, and the Caribbean-Americas regions.
Each of these three can be very painful, disrupting every aspect of life for weeks (even months), while one form of dengue can be deadly. So, it’s more important than ever that Aussies visiting a tropical country avoid mozzie bites.
Why we must protect our communities
But, there’s another reason to dodge dengue, chikungunya and Zika: To keep family, friends and your local wider community safe from infection.
The danger associated with travellers ‘importing’ these diseases is very real in Australia now. But, it will become even more critical in years to come as climate change takes effect and ever more people travel overseas for leisure or business each year.
Infected travellers already bring dengue into North Queensland each summer. The Aedes aegypti mozzies that spreads it are firmly established there and annual outbreaks see scores – sometimes hundreds – of people get sick. Fortunately, deaths have been rare.
But, Aedes aegypti has a cousin, Aedes albopictus, better known as the ‘Asian Tiger’ because of its striped body and legs. Without doubt, it’s now the world’s number one mozzie menace because it not only transmits dengue and yellow fever, but chikungunya and Zika too.
The Asian Tiger has been eyeing Australia for some time and authorities are monitoring intensively to detect incursions in an attempt to keep the species at bay.
Tenacious tiger will survive southern winters
Sydney-based entomologist Dr Cameron Webb believes it’s only a matter of time before it too becomes established here. The problem is that when it does, its geographic range won’t be limited to North Queensland: Even Tasmania won’t be safe from this climate-tolerant pest.
According to Dr Webb, Aedes albopictus is ‘perfectly adapted’ to summer life in Australia’s cooler southern cities, whose communities would otherwise be immune from local outbreaks of tropical diseases.
It’s able to breed in just a few drops of water and its eggs can endure lower winter temperatures to hatch in spring, while adults can survive and breed in micro habitats like greenhouses and indoor gardens during the cooler months.
In a recent paper, Dr Webb warned that while climate change will be a factor, the movement of people poses the biggest risk to Australia from an Asian Tiger invasion.
The Asian Tiger has already hitchhiked to Africa, the Caribbean, and North and South America. It’s even well established in parts of Europe and North America, its eggs carried with people and their belongings, as well as hidden among imported goods ferried by sea and air.
Not a matter of if, but when
Travellers can play a role in keeping these unwanted invaders out of Australia by protecting themselves against mozzie bites, so they don’t get infected and by ensuring they don’t inadvertently bring mosquitoes home in their luggage.
“If – or rather, when – the Asian Tiger reaches one of our major southern cities, there is little doubt that it could quickly become a persistent summer pest as well as a public health threat,” Dr Webb said.
“The way we respond to water shortages by installing tanks to store rainwater around our homes could set the scene for this mozzie to move into cities and towns. Once the species becomes established, all we need are travellers to bring in the viruses and they could then be spread by the Tiger.”
Last year Japan experienced its biggest outbreak of dengue in over 70 years when a traveller introduced the virus to an undetected cluster of Asian Tiger mosquitoes in a park in Tokyo.
Dr Webb said Tokyo’s outbreak has implications for local authorities in Australia. He advocates a multi-agency approach to mosquito surveillance here, along with strategies to eliminate these tiny invaders quickly and effectively whenever they’re discovered.
Change of mozzie mindset needed
Australian travellers continue to be blasé about potential travel-related health risks, the mosquito-borne diseases included.
Only vaguely aware that they have tongue-twisting names, we tend to dismiss the risk even when we holiday in places where dengue, chikungunya, Zika, and malaria are a significant problem.
Which is why these four diseases together infected more than 2000 Australian travellers last year and why we’re on track for a similar number this year.
As world travellers, we need to change our mindset and pay mosquitoes more respect. Not just to protect ourselves, but to safeguard our friends, family and neighbours too.
Make dodging bites routine during travel
When travelling overseas, it needs to become second nature to avoid insect bites by:
- Applying an insect repellent containing an effective ingredient such as DEET (30-50% formulations for adults, or 10-20% formulations for young children and infants as young as 2 months of age), Picaridin, IR3535, or preparations containing extract of lemon eucalyptus oil when mosquitoes are about outdoors – especially at dawn and dusk when they are most active.
- Wearing long, loose-fitting, light-coloured clothing at those peak feeding times.
- Sleeping under a treated bed net if you’re staying in a tent or in budget accommodation without screened doors and windows, or air-conditioning. You can buy a treated net or purchase a DIY kit to treat both your net and clothing with permethrin, a safe contact insecticide. Used in conjunction to your personal insect repellent, permethrin creates an additional barrier that repels and ultimately kills biting bugs that land on your bed net or clothes.
The fewer times you get bitten, the lower the risk of infection. Don’t get bitten and there’s absolutely no chance at all.
* Dr Bajrovic is the Medical Director of Travelvax Australia.
Did you know you can get no-obligation, country-specific advice on insect-borne diseases and other potential health risks of your next overseas destination by calling Travelvax Australia’s travel health advisory service on 1300 360 164 (toll-free to landlines)?