Key points
- There are more than 3000 species of mosquitoes around the world and Australia has many unique species.
- Some have adapted to urbanisation and are evolving to better target humans. Climate change will also likely impact mosquito populations.
- We're researching new strategies to block the disease transmission by these mosquitoes.
Summer is here and the mosquitoes are ready!
We swat up on mosquitoes with our vector biologist Dr Prasad Paradkar. Prasad tells you how to protect yourself and shares findings from our latest research.
The path to ‘enbitenment’
Prasad is a medical doctor turned mosquito vector researcher at our Australian Centre for Disease Preparedness. Formerly, a medical doctor in India, he saw several cases of dengue and malaria.
“I’ve always been interested in the transmission and epidemiology of those diseases, so I made the decision to work in this field."
Prasad and his team look at the ability of local mosquitoes to be a host for and to transmit diseases such as viruses.
“We study how to target mosquitoes with different interventions to prevent disease transmission, rather than just looking at vaccines or therapeutics to treat the disease in humans.”
When a female mosquito feeds on an infected host, they pick up their virus. In their next feed they transmit the virus to the next person or animal. Only female mosquitoes bite because they require blood to make their eggs mature. When they bite, they inject saliva, which sometimes contains viruses.
Whenever an exotic virus like Japanese encephalitis poses a new threat to Australia, Prasad and his team promptly assess the risk of transmission by local mosquitoes.
It comes down to the genetics of the local mosquitoes that determines whether they will be good transmitters since not all viruses are transmitted by all mosquitoes. For example, dengue is transmitted by Aedes species of mosquito but not by Culex species. Conversely, Japanese encephalitis is transmitted by Culex species but not by Aedes mosquitoes.
Mosquito management around your home
Prasad has a few great tips for reducing mosquitoes around your home. These include removing any stagnant water sources. These can become breeding sites for mosquitoes.
“The mosquitoes that transmit viruses, such as Japanese encephalitis and Murray Valley encephalitis, don't travel very far,” Prasad said.
“It's really the local areas around your house that are the key source of mosquitoes.”
Prasad also recommends you check your rainwater tanks to make sure they have a good mesh cover on top.
“Mosquitoes don’t need much water to breed, so make sure there are no other breeding sites for mosquitoes such as water bowls of pets, bird baths or pot plant saucers,” Prasad said.
When outdoors, cover up with long sleeves and long pants wherever possible. Use repellents containing DEET, such as Aeroguard, when you go outside. Remember, mosquitoes are the most active and looking for blood around dawn and dusk.
An itchy situationship
There are more than 3000 species of mosquitoes around the world. Australia has many unique species, with the common species in Australia being Aedes notoscriptus, Culex quinquefasciatus and Culex annulirostris.
A lot is still unknown about their roles in disease transmission and the ecosystem. We do know mosquitoes are a good food source for certain birds and bats, and some mosquitoes are pollinators. The Culex species are mainly bird biters while the Aedes are mammalian or marsupial biters, but both can bite humans as well.
“Culex is an important one as it transmits Japanese encephalitis virus,” Prasad said.
“It mainly bites water birds, but it can also bite humans and horses, and that's when they can cause disease."
Adaptation in action
Mosquitoes are early adopters and rapidly evolving.
“I find them fascinating,” Prasad said. “They adapt really quickly to urban environments and human behaviour.”
For example, in Africa people started using insecticide-treated sleeping nets at night to protect themselves from mosquitoes. The mosquitoes have now adapted to that by changing their biting behaviour.
“The Anopheles mosquito, which transmits malaria, used to bite only at night, but that's when the bed nets are used,” Prasad said.
“So now they have changed their behaviour to more evening biting when there are no nets being used.”
Global warming, global buzzing?
Climate change may lead to more mosquitoes globally, as a warming climate and heavy rainfall can increase the mosquito population.
“Some extreme climatic events can also transport mosquitoes directly to new areas. Meanwhile, increased temperature shortens the mosquito developmental time and incubation period of virus in mosquitoes. So, they become infective more quickly,” Prasad said.
As average global temperature increases, mosquito populations will spread to newer areas. In Australia they will move southwards. In the Northern Hemisphere they will move north.
“The vectors for dengue will move southwards too, and it’s likely dengue will move with them,” Prasad said adding that only time would tell.
Parts of Europe have now seen Aedes albopictus mosquito become established. With this species being a transmitter of various viruses, this has raised health concerns.
“There have been locally transmitted cases of dengue in Europe recently. It’s unclear whether this will also happen in Australia,” Prasad said.
How mosquitoes adapt to increasing global temperature, and what temperatures are optimal for the transmission of viruses and mosquito lifespan, remains to be seen.
“If the change is just a couple of degrees warmer, mosquitoes will be able to adapt really well,” Prasad said.
“But if you go above that to really extreme high temperatures like 35 or 40 degrees Celsius, then it's too hot for mosquitoes as they will dry out.”
A bite future
Prasad’s team is looking at new technologies to prevent transmission, such as using a naturally occurring bacteria called Wolbachia.
This involves releasing millions of male mosquitoes infected with Wolbachia. They then mate with wild female mosquitoes to produce sterile eggs, which causes mosquito populations to decrease.
“The next stage is genome engineered mosquitoes to prevent virus transmission or reduce population,” Prasad said.
“We know we can do that in the lab but taking it into the field is going to be a whole new area, including discussion and education with the community.”
“The mosquito genome is complex but a lot of people are working on it. It’s a case of ‘watch this space’ for some exciting times ahead.”
TL;DR? Remember these tips
- Remove any breeding sites for mosquitoes. They don’t need much water to breed and can quickly proliferate in water bowls of pets, bird baths, pot plant saucers and backyard buckets.
- Cover up when outdoors, with long sleeves and long pants.
- Use repellents containing DEET, such as Aeroguard, when you go outside – especially at peak mosquito times of dawn and dusk.
- Check your rainwater tanks to make sure they have a good mesh cover on top, their sieves are clean and are sealed to prevent mosquito entry.