New mosquito type seen making malaria fight harder

LONDON Thu Feb 3, 2011 3:21pm EST

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LONDON (Reuters) - Scientists have discovered a new type of mosquito in Africa unlike any documented before and say it could further complicate the fight to control malaria.

Scientists from France who collected mosquitoes from ponds near villages in Burkina Faso say they identified a subtype of the Anopheles gambiae mosquito that is highly susceptible to infection with the malaria parasite, likes to rest outside, not indoors, and can therefore evade most current control measures.

"They are very susceptible to the human malaria parasite, we know they belong to a species that has an exquisite preference for human blood, and we know they are abundant in the population," said Ken Vernick, who discovered the mosquito with colleagues at the Unit of Hosts, Vectors and Pathogens at the French National Center for Scientific Research in Paris.

Vernick said the researchers were not yet able to quantify how much malaria transmission this new mosquito subtype is responsible for, but they feared it might be a major factor.

"What we can say is that it's unlikely they're harmless," he said in a telephone interview.

Malaria is an infectious disease spread by mosquitoes that threatens up to half the world's population. Most of its victims are children under five in poor countries in sub-Saharan Africa.

The World Health Organization's (WHO) latest malaria report found that some progress against the disease has been made over the past decade, with deaths estimated to have dropped to 781,000 in 2009 from nearly a million in 2000.

"NEVER-ENDING BATTLE"

In a study in the journal Science, the French team said the newly-identified mosquito, nicknamed Goundry after one of the villages near where it was discovered, was unlike any that has turned up in collections before.

This is probably because nearly all mosquitoes collected for research in the past have been taken from inside human dwellings, they said, where the insects are easier to catch.

"A few scattered studies over the years have suggested that the vector population was not just indoors, but that there was more to the story," Vernick said, which was why his team decided to collect mosquitoes from outside and study them more closely.

Having found the new subtype, the team grew new generations of it in the laboratory and found that it was significantly more susceptible to the malaria parasite than recorded indoor types.

This suggests the Goundry may be quite young in evolutionary terms, Vernick said, and may even have evolved as an outdoor subtype as a way of resisting indoor control measures such as spraying insecticides or encouraging people to sleep under insecticide-treated mosquito nets.

The WHO, which has called for faster research and development of new anti-malarial drugs, said late last year that the international community could stop malaria deaths by 2015 if it put in massive levels of investment.

But Vernick said discoveries such as this one added to what he called the "never-ending battle" against the disease.

"The parasite is smarter than all the immunologists that study it... and the mosquito is smarter than all the vector biologists that study it," he said. "It's not a fair fight."

( For a Reuters SPECIAL REPORT on the fight against malaria, click on link.reuters.com/cep99q )

(Editing by Ralph Boulton)

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