Published On: July 15, 2015

Technology Fights Dengue Fever

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Millions of modified mosquitoes have been intentionally released in the city of Piracicaba in São Paulo state in the battle against dengue fever. The genetically modified mosquitoes are all male, and when they mate with females, they pass on a gene to the offspring that causes the larvae to die before they mature. Hence the modified male mosquitoes are designed to eliminate their own species.

However, for those who enjoy the presence of mosquitoes, there is nothing to fear. The mosquito population is not being eliminated in Brazil or even in São Paulo. Only the mosquitoes that carry dengue are being targeted, the species known as Aedes aegypti.

The new mosquitoes were designed by Oxitec of Abingdon, UK, and are bred “en masse” in a factory in Campinas. Oxitec has a permit to commercialize and release the mosquitoes anywhere in Brazil. Oxitec is also waiting for permission from the US Food and Drug Administration (FDA) to test the mosquitoes in the Florida Keys in the US.

The test began in April, and since then 6 million of the modified mosquitoes have been released in Piracicaba. “The government has asked us to attack the neighborhood that has the highest number of dengue mosquitoes to prove our system works,” said Hadyn Parry, chief executive of Oxitec. “We hope that if it does, we can expand to a larger number of areas.” The plan is to flood the area with the modified mosquitoes to outnumber the male mosquitoes there, and thus gradually reduce the numbers of dengue-transmitting mosquitoes.


Modified male mosquitoes are released in Brazil (Credit: Oxitec)

Modified male mosquitoes are released in Brazil (Credit: Oxitec)


Another amazing accomplishment in this mosquito modification is the modified mosquitoes also carry a gene that makes the larvae they breed glow red under ultraviolet light, which allows scientists to see how well the strategy is working. By leaving pots of water in which female mosquitoes lay eggs at strategically important sites in the city, researchers can tell by counting the proportion of red larvae how well the test is working.

“The ultraviolet light gives an instant readout of how successfully we’re driving down the dengue mosquito population,” says Parry. So far, the survey has revealed that half of the larvae in the area have been sired by the modified mosquitoes.

In another recent trial in the city of Juazeiro, tests showed that within six months the special mosquitoes had reduced the dengue mosquito population by 95 percent. “This showed that our method is more effective than any other at eradicating the mosquitoes that transmit this disease,” says Parry. “With insecticides, nothing clears more than 50 per cent of the mosquitoes.”


Dengue fever outbreak in Mexico

Dengue fever outbreak in Mexico



Whether the reduction of dengue-transmitting mosquitoes will actually lead to a drop in the number of humans infected by the disease is still to be seen. “In theory, if you have fewer mosquitoes, you will have less likelihood of transmission of the disease from mosquito to human. However, in reality, this is something we still need to investigate,” says Margareth Capurro of the University of São Paulo, head of the Brazilian team that conducted the Brazilian-funded test on behalf of Oxitec in Juazeiro.

Laith Yakob of the London School of Hygiene and Tropical Medicine says the results are impressive but the effect may be temporary, just as it is with chemical spraying, because mosquitoes can move in from elsewhere and those remaining will multiply. So further testing is needed to optimize the timing and location of releases to reduce and manage the human infections of dengue.

“Thus far the test results are impressive. The level of control is phenomenal and although some wild mosquitoes remained, these were of such low numbers as to suggest an eliminated threat of disease,” Laith said. Oxitec is now hoping to win FDA approval for trials in Florida, as a preventative measure. Unlike in Brazil, where polls show high levels of public support for the technique, there has been opposition in Florida. This is not surprising, says Parry, because Brazil can have more than a million new cases of dengue fever a year, whereas Florida has almost none.



[This article comes from research provided by Reed Business Information.]




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