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Transgenic mosquitos to combat dengue
A program to use genetically modified (GM) mosquitos to combat or even eradicate dengue fever in Brazil is having pretty spectacular results. Male mosquitos were genetically engineered to carry a "poison pill" in their genes: a gene that provokes the death of the progeny before reaching adulthood. Lowering the population of mosquitos will lower the transmission rate of this serious viral disease, since mosquitoes are the insect vector. Over 10 million GM male mosquitoes were released over a 300,000-people Brazilian city, Juazeiro, in Eastern Brazil in the state of Bahia, in a period of one year, and currently, >80% of eggs collected around the area carry the lethal transgene. The GM mosquitos are being tested in the Cayman Islands and in Malaysia too. So, if the gene is lethal, how can you raise large numbers of males carrying the lethal gene? A repressible system has been used to express the lethal gene, and repression can be maintained in the lab by feeding tetracycline (a cheap antibiotic) to the mosquitoes. Once released in the wild, there is no tetracycline around so the lethal gene, a transcriptional activator, is highly expressed, and kills the carriers. The experiments are being closely monitored for unexpected problems with the GM mosquitoes. Males were chosen to carry the lethal gene because they do not bite humans, only females do.
Brazil tests GM mosquitoes to fight Dengue
Males with offspring-killing genes are replacing wild insects, say researchers.
11 April 2012
Engineered males might mean fewer female Aedes aegypti mosquitoes to spread Dengue fever.
JAMES GATHANY/CDC
Scientists in Brazil say an experiment to reduce populations of the dengue-carrying Aedes aegypti mosquito, by releasing millions of genetically modified (GM) insects into the wild, is working.
More than ten million modified male mosquitoes were released in the city of Juazeiro, a city of 288,000 people, over a period of time starting a year ago.
The results were released at a workshop in Rio last week (28–29 March), where the project's co-ordinator, Aldo Malavasi, said they were "very positive".
"From samples collected in the field, 85 per cent of the eggs were transgenic, which means that the males released are overriding the wild population. This [should result] in the decrease of Aedes mosquitoes, and in the decrease of dengue transmission," he told SciDev.Net.
Malavasi is also the president of Moscamed — the Brazilian firm that produced the mosquitoes. The mosquitoes, which carry a gene which causes their offspring to die before reaching adulthood, were originally developed by the British firm Oxitec.
They have already been tested in Malaysia and the Cayman Islands, but this is believed to be the largest experiment in the wild to date.
"We developed technology to efficiently create the transgenic insects here [in Brazil], so we won't need to buy them from England in the future, reducing costs," Malavasi said.
The method has been approved by the Brazilian National Biosafety Technical Committee, and will be used in other Brazilian cities. Ultimately, it is hoped the GM mosquitoes will lead to the eradication of dengue in areas where insect translocation is low, and substantially reduced elsewhere.
Before releasing the mosquitoes, Malavasi said his team visited homes, schools and churches in Juazeiro to seek the permission of residents, and said nearly 90 per cent were in favour.
Read the rest here.
Tags: Dengue, genetic engineering, mosquito, transgene, transgenic
Replies to This Discussion
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Permalink Reply by Michel on -
I wonder what kind of political crap a similar project would raise in the US.
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Permalink Reply by Adriana on -
It wouldn't raise much of an eyebrow, the regulations of GM organisms in the US are basically null. Corporations rule.
Though in this case I think it would not be a bad idea. Dengue is a serious, serious disease.
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Permalink Reply by Chris on -
An Indian reservation I used to live near refused to let mosquito abatement on the reservation when the abatement program was expanded because of West Nile virus. The rational for refusing the spraying for mosquitoes was the larva feed the fish and other aquatic life. Diminishing the mosquito population in Brazil will reduce that food source for other species.
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Permalink Reply by Adriana on
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An ecological assessment is needed, no doubt. But they were already reducing the mosquito population by spraying chemical insecticides, which are toxic. A worse solution than this one, in principle. Dengue is not a nice disease.
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Permalink Reply by Adriana on
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GeneWatch, a UK organization that opposes (or at least keeps an eye on) transgenics and GM animals and crops, has this article:
Researchers have been experimenting with genetically modifying a variety of insects, including mosquitoes, fruit flies, moths and bollworms.
The Oxfordshire-based company Oxitec plans to release genetically modified (GM) diamond back moths (which eat cabbages) in experimental trials in Britain in 2012. The company is seeking to bypass regulations by arguing that its insects are "biologically contained" because they are programmed to die and that therefore the requirements for open releases of genetically modified organisms do not apply.
Controversial experimental releases of 3 million GM mosquitoes produced by Oxitec took place in the Cayman Islands (a British Overseas Territory which has no biosafety law) in 2009 and 2010. A smaller number of Oxitec's GM mosquitoes were released in December 2010 in Malaysia and in 2011 in Brazil. According to Oxitec, future experimental releases are planned in other countries, including Panama, India, Singapore, Thailand, Vietnam and the United States (Florida Keys), and are also being discussed in the Philippines, Costa Rica and Trinidad & Tobago. However, Vietnam has stated that it does not intend to release GM mosquitoes and plans in the US have been delayed pending a regulatory assessment by the Food and Drug Administration (FDA).
There is a fundamental flaw in Oxitec's technology, which uses the common antibiotic tetracycline as a chemical switch to allow it to breed GM insects in the lab. The insects are supposed to breed with wild insects on release but their offspring should die before adulthood, reducing the wild population. But a confidential company document shows that 15 percent of the GM insects survive to adulthood in the presence of very low levels of tetracycline contamination, which is widespread in the environment. Third World Network has published a briefing on this issue.
The Public Library of Science has published a collection of articles about the regulation of genetically modified insects, including an article by scientists at the Max Planck Institute that criticises the risk assessments for Oxitec's GM insect trials.
A GM pink bollworm moth (a cotton pest) also produced by Oxitec and containing a fluorescent marker gene was released in 2006 to 2008 in the US as part of a plant pest control programme. GM bollworms are being developed in response to the development of resistance to the Bt toxin which is engineered into pest-resistant GM crops (Bt crops) such as maize and cotton.
Other insects might be genetically modified in future.
The honey bee genome was completed in 2006 and in May 2011 Nature News reported that this might allow geneticists to "build a better bee". Plans to sequence thousands of insect and other arthropod genomes were announced in June 2011.
In November 2011, scientists reporting the completion of the spider mite genome argued that it could be used to reduce the mite's ability to reproduce. Completion of the Monarch butterfly genome was also announced.
What they cite as a fatal flaw, that there are some escapees from the trtracycline system, is not a bad thing in my opinion, this way you do not exterminate the mosquitoes, just reduce the population.
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