GM mosquitoes to fight dengue fever during the world cup

To say that getting dengue fever - aka breakbone fever - isn’t fun is an understatement. Around the world, there are between 50 and 100 million cases a year, mostly in tropical countries, according to the World Health Organization. Of these cases, 22,000 result in deaths. Though the disease lasts no more than 10 days, its effects on the immune system can be felt for up to a year after infection. Contracting it often means hospitalization and a drip stuck into your hand. TreeHugger founder Graham Hill caught dengue in Rio and said it made him feel “deathly sick.”

That’s why Brazil, the country with the highest incidence of dengue in the world, has been using genetically modified mosquitoes to reduce mosquito populations during the World Cup. But like anything GM, this has caused controversy and many are questioning the safety and ecological impact of this method.

Genetic modification of mosquitoes is a technology has been around for several years. Basically, scientists are able to insert genes that make male mosquitoes sterile or prevent larvae from reaching maturity. This guarantees that the population declines and has been so successful that trials in Jacobina, Brazil have reduced mosquito populations by 90 percent.

Such a drastic change in population has been a major source of concern in the online community. Many are concerned that this will throw the Brazilian ecosystem out of balance. But scientists like Dr. Dina Fonseca, associate professor in the ecology and evolution of mosquitoes at Rutgers, say fear not! Aedes aegypti, the mosquito responsible for dengue transmission, is not native to Brazil. In fact, it’s not native to most parts of the world where it’s found, spreading terror in its wake.

Plus, the Aedes aegypti spread is largely an urban phenomenon. “The mosquitoes are exploiting a very artificial environment,” said Fonseca. “It’s kind of an ecosystem of just humans and mosquitoes. Aedes aegypti is not found in ponds, it’s not found in lakes, it’s not being fed on by any sort of invertebrate predators, and it’s not an important source of food for any other member of the ecosystem.”

Photo by: A. Tigre Small puddles like this are the perfect breeding ground for Aedes aegypti/CC BY 2.0

And the Aedes aegypti has masterfully adapted to our city living. Its larvae can survive in extreme conditions with little water and limited amounts of bacteria to feed on. They take advantage of water gathered in small puddles and containers in people’s yards or roofs. With no predators in these places, like fish, to eat the larvae, the Aedes aegypti population grows rapidly.

Fonseca added that compared to pesticides and insecticides, genetic modification was a much safer approach to combating dengue. Unlike pesticides, which kill a wide range of insects and to which many mosquitoes are resistant, genetic modification will only affect the Aedes aegypti species.

“We react horribly to the idea of releasing these males that are being modified so that they’re sterile but we have no problem applying some horrible insecticides to our lawns and our back yards and all these things, to which we know the secondary effects,” she said. “Applying organo-phosphates kills the fish, kills all the bees, but we apply them anyway.”

Photo by: Sanofi Pasteru/Marizilda Cruppe Pesticides are used to fight dengue, but many mosquitoes have built a resistance to them/CC BY 2.0

These reassurances haven’t satisfied all critics. Though Aedes aegypti is the main transmitter of dengue, other species like the Asian Tiger mosquito can spread it too. These critics say there is a chance that the Asian Tiger mosquito will take over the role of Aedes aegypti.

Helen Wallace, director of environmental group Gene Watch, recently said she was worried that these mosquitoes would mutate once released. Since the sterilizing gene is blocked by an antibiotic called tetracycline, she added that mosquitoes might survive by being exposed to tetracycline outside of lab conditions and pass on their mutated genes to future generations. She stressed that they could not be recaptured if anything went wrong.

Tim Harvey-Samuel, a Ph.D. student studying genetic pest management at Oxford University in the UK, said that this technology is extremely species specific and self-contained, so we won’t be seeing giant mosquitoes flying around.

For people who are concerned about being bitten by the GM mosquitoes, he added that only males are genetically modified, and male mosquitoes do not bite humans.

“Where incidence of dengue is very high, people have been much more receptive to the technology in general,” said Harvey-Samuel. “These mosquitoes are not meant to be there.”

Tags: Antibiotics | Asia | Brazil | Diseases | Ecology | Genetic Engineering | GMO | Health | Insects | Pesticides

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