mosquito on human skin at sunset

With the outbreak of Japanese encephalitis and increasing numbers of Ross River Virus, authorities, designers and communities have started to turn their minds to how to mitigate the risk of mosquito-borne diseases. Considering mosquito habitat is an important aspect of urban design that should come hand-in-hand with climate adaptation. 

In an increasingly hot and humid climate, citizens and urban design professionals are looking for greening solutions such as vertical garden walls, tree coverage and parklands. City greening makes for healthier populations, cooler temperatures, happiness and liveability.

But plants and the water that feeds them can invite unwelcome guests into homes and workplaces. Mosquitos thrive around water for reproduction. Urban greening is inadvertently creating a pest and disease problem for city-dwellers. 

“Mosquitos are the most deadly animal on the planet… About half a million people die every year because of mosquito bites.”

– Dr Cameron Webb

How can we create green cities for the future without creating a major mosquito problem and the ensuing mosquito borne disease outbreaks?

There are hundreds of different mosquitos across Australia, and a dozen or so that live in bodies of water in our cities including rainwater tanks, wetlands, green walls on buildings and water infrastructure. 

“Unfortunately the way we conserve water and expand our local water sensitive environment is great for people, but can create habitat for mosquitos,” Dr Cameron Webb, mosquito expert and clinical associate professor of medical entomology at NSW Health Pathology and the University of Sydney, told The Fifth Estate.

“Mosquitos are the most deadly animal on the planet,” Dr Webb said in a Ted 2019 Ted Talk at Ted X Parramatta. “About half a million people die every year because of mosquito bites. Diseases such as malaria and dengue infect hundreds of millions of people every year across the planet. That burden of disease weighs quite heavily on both communities and local authorities as they struggle to try and deal with those impacts.” 

How climate change is increasing mosquito-borne disease risk in Australia’s cities

Australia has been lucky to avoid the most damaging diseases including malaria, dengue fever, and zika virus. But we do have cases of Ross River Virus (RRV), which in some cases can be debilitating. 

“Mosquitos aren’t like a dirty syringe transferring diseases from person to person,” Dr Webb explained to The Fifth Estate. “Different species spread different diseases.” 

But a recent outbreak of Japanese encephalitis (JEV), which in less than 1 per cent of cases can cause a life-threatening brain infection, has now struck down a Griffith man in his 70s and a Goulburn man in his 60s.

Australia has now had 18 confirmed cases of JEV in humans: six in NSW, seven in Victoria, four in SA and one in Queensland.

On Tuesday Agriculture Victoria confirmed the mosquito-borne virus had been detected in the regional local government areas of Campaspe, Loddon, Gannawarra and the Northern Grampians.

Climate change may “increase our chances of getting dengue fever and zika virus here”.

– Dr Cameron Webb

NSW Health said investigations are underway to locate the source of his infections, and they have urged the community to ”stay vigilant”.

Piggery workers are undergoing vaccinations and abattoirs are “fogging” (spraying areas with insecticides such as pyrethrins) mosquitos to prevent the spread.

Dr Webb said that in Australia there has been an increase in mosquito borne diseases arising from changing climates, particularly an uptick in cases of RRV caused by increased and more extreme weather events such as storms and flooding. An average of 4653 cases have been recorded in Australia annually since 1993, with a rise in cases around the eastern seaboard and major east coast metropolitan areas, which has been a “rising concern for health authorities”. 

“But it’s not a simple scenario.” 

The other side of the coin is that with travel restrictions lifting and tourism returning in the near future, we might see new types of mosquitos accidentally making the trip across the seas into Australia (such as via larvae caught in shoe soles, which authorities urge should be washed on re-entry).

And with a changing climate these species may be able to adapt and thrive in the environment here, including more those bringing more dangerous diseases with them.

“That may increase our chances of getting dengue fever and zika virus here. If these diseases can get to Australia, that’s a game-changer. Japanese encephalitis is mostly a rural risk, but dengue and zika can live in our cities, and that’s dangerous.” 

This is Part 1 of a two-part article series.

Read Part 2 here: How to prevent and mitigate the threat of mosquito-borne diseases in our cities

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