Scientists closing the zap on dengue fever

Jan 01, 2009

(PhysOrg.com) -- A mosquito-borne virus that each year harms up to 100 million people and kills more than 20,000 is a step closer to being controlled after a breakthrough by Queensland scientists.

In a paper published in the prestigious international journal Science on January 2, researchers from The University of Queensland have proved the effectiveness of a new way of limiting the lifespan of the type of mosquito that spreads dengue fever.

They have done it by infecting the dengue mosquito, Aedes aegypti, with a bacterium that is harmless to humans and other animals but halves Aedes' lifespan. This has the potential to greatly reduce dengue because only old mosquitoes are effective at transmitting the virus to humans.

The scientists' success is critical to the progress of a $10 million project funded by the Bill and Melinda Gates Foundation and may lead to a new, safe and cheap way of curtailing dengue fever.

Carried out in the laboratory of Professor Scott O'Neill, Head of UQ's School of Biological Sciences, the experiment's focus was painstaking work with the Aedes mosquito and Wolbachia, a bacterium that occurs naturally in fruit flies.

PhD student Conor McMeniman used super-fine needles to manually inject 10,000 mosquito embryos with Wolbachia, and encouraged the surviving mosquitoes to feed on his own blood.

“We ended up having to inject thousands of embryos to achieve success, but it was well and truly worth it in the end,” Mr McMeniman said.

The researchers have shown that Wolbachia halves mosquitoes' lifespan, which can be up to 30 days in the field. This dramatically curtailed their potential to spread dengue fever, without preventing the hereditary transmission of the bacterium.

Professor O'Neill said the project's next stage would be a contained field cage setting in northern Queensland.

“If that proves successful we hope to deploy this new dengue control measure in other parts of Australia, as well as Thailand and Vietnam,” Professor O'Neill said.

There is no vaccine or cure for dengue fever, which is a painful and debilitating disease also known as ‘breakbone fever'. Dengue haemorrhagic fever can be lethal.

The virus is of greatest concern in tropical parts of the developing world but - despite significant investments in insecticides and public awareness campaigns - outbreaks are not uncommon in northern Queensland. More than 50 cases have been confirmed in Cairns in northern Queensland since Nov 27, 2008.

Globally, outbreaks of dengue are becoming more common, and there are concerns that climate change will place more people at risk.

Web site: www.mosquitoage.org

Provided by University of Queensland

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User comments : 8

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tkjtkj
1 / 5 (3) Jan 01, 2009
So, what is that "evolutionary quirk that let's them gain a foothold...." ???????
Some big secret, perhaps???

and why is this FireFox refusing to let me copy/paste the actual sentence i manually quoted here, above??

Is it some consequence of this new 'blogging'-style ???

WolfAtTheDoor
2 / 5 (3) Jan 01, 2009
and why is this FireFox refusing to let me copy/paste the actual sentence i manually quoted here, above??

If you are open-minded try Google Chrome. It's wicked fast and doesn't have any of the hoopla.
Szkeptik
5 / 5 (2) Jan 02, 2009
Sounds great. At last a solution that's more elegant than the usual "spray 'em with toxic shit" approach. It's ways like this how an intelligent species should solve it's problems. Directed, timed, intricate, precise. I like it.
bmerc
5 / 5 (1) Jan 02, 2009
I think that it is great that research like this is being conducted but if mosquitoes tend to live 50 days in a lab but only 21 days if infected with this bacteria and this life span is longer than in the wild would this even have a big enough of an impact on the wild mosquito population? If it only shortens a wild mosquitoes life by a couple of days then I don't see how it could have much of an effect by itself. What is the average life span of malaria and dengue carrying mosquitoes in the wild?
smiffy
not rated yet Jan 02, 2009
I think that what the report was suggesting was that the 60% reduction in life span in the lab population would be translated pro rata in the wild (at least for the longer living mosquitos).

On a precautionary note I would say that they need to be careful with Wolbachia since it's very effective at horizontal gene transfer. They don't want to be breeding any supermosquitos.
ancible
not rated yet Jan 02, 2009
"...it takes roughly two weeks of incubation before the insect can spread that pathogen..."

This is why it is important. If the non-lab, parasite-infected lifespan is only 13 days or less, than no disease.
And even if it's only around 15-18 days, that's still only 1-3 disease spreading days vs. around 12-15 for uninfected mosquitoes.
pecachon
not rated yet Jan 02, 2009
I dont trust aussies to do anythi g with animals anymore. They are so dumb about their ecology. Look at their bird and rabbit problems. Australia needs to stop messing with animals!
smiffy
not rated yet Jan 03, 2009
pecachon, you forgot to mention Cane Toads!
http://en.wikiped..._History

Seriously though, a transference of any insecticide resistance belonging to the non-malaria kind of mosquitos to the malaria-bearing kind would be bad news. Not to mention the transference of the susceptibility of carrying malaria across the species in the other direction.

I've no idea how likely this would be. But I suspect that no one else does either.

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