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[SAO PAULO] Brazilian authorities have decided that a genetically modified (GM) strain of mosquitoes whose offspring die before reaching adulthood do not pose a significant risk to humans or the environment. The decision will open up the possibility of the company that developed the insects selling them in Brazil as a control strategy for dengue fever.

The approval was made last month (10 April) by the National Technical Commission on Biosecurity, the organisation that regulates transgenic organisms in Brazil.

The GM strain, known as OX513A, has already been released in experiments across Brazil. And with their use now rubber-stamped, its developer, UK biotech firm Oxitec, plans to apply for a licence to sell it to local government bodies in Brazil.

“Once Oxitec has a commercial licence, the company intends deploying A. aegypti mosquito control programmes. The potential customers would be municipalities and other government and private entities,” Glen Slade, Oxitec’s head of business development, tells SciDev.Net.

He says the firm is preparing to request a licence from Brazil’s National Health Surveillance Agency.

The male GM mosquitoes have two additional genes: one makes a protein that causes a breakdown in the insect’s development and a second which acts as a marker, enabling researchers to monitor the mosquitoes in the field.

Wild female mosquitoes that mate with GM males transfer the genes to their offspring, which die before reaching adulthood.

Researchers from the University of Sao Paulo, along with Oxitec, have tested this approach in three field trials in Brazil’s Bahia state since 2011. In these, successive releases of the transgenic strain reduced the wild adult population of A. aegypti by between 79 and 93 per cent, according to Oxitec.

Yet GeneWatch UK, a not-for-profit organisation that monitors biotechnology, warned in a statement that the population of another dengue-transmitting mosquito, Aedes albopictus, could increase if Oxitec’s mosquitoes were released.

However, Slade tells SciDev.Net: “It is possible that the number of A. albopictus increases in areas where the infestation of A. aegypti is reduced, but it isn’t correlated, as each species prefers a specific habitat.” 

In any case, he adds, “A. albopictus has been shown to be a poor dengue vector”.

Jayme Souza-Neto, a genetics researcher at Sao Paulo State University, says the long-term impacts of releasing GM mosquitoes are uncertain.

He says: “Even though Oxitec claims that the first trials have been successful, causing significant suppressions in the mosquito population, the actual effect of this on reducing dengue transmission is still unclear.”

Brazilian biosafety agencies must closely monitor future releases, he says.

Souza-Neto adds that implementing Oxitec’s technique in a town of 50,000 people would cost two to five million reals (about US$890,000 to US$2.2 million) in its first year and around one million reals in following years.

“Although it is a promising method to control dengue mosquitoes, it is still imperative that the government continues to support education and warning programmes to keep the population watching out for breeding sites and other preventative actions against dengue,” he tells SciDev.Net.