Malaysia releases transgenic mosquitoes in controversial dengue study

Posted on February 17, 2011. Filed under: Bio-diversity |

A study involving the release of transgenic mosquitoes to combat dengue fever has taken place in Malaysia. This follows reports (see that the release had been postponed, in response to protests made by a number of environmental non-government organizations (NGOs).

The new approach to dengue control is a modification of the sterile insect technique (ST), in which insects that do not produce fertile offspring are released into the environment with the aim of displacing the natural population of insects of the same species, leading to a collapse in population numbers. First developed in the 1950s for the elimination of screwworm, ST has also been used successfully against a number of other agricultural pests. The insects released in ST programmes have been sterilized by radiation but, in the case of the Malaysian trial, sterile males of the mosquito Aedes aegypti (the main dengue vector) have been produced through genetic modification (GM) – a technology that has many opponents worldwide.

The transgenic strain codenamed OX513A was created in Oxford University and has been developed for field use by a spin-out company Oxitec (see article). Interviewed in the Independent (UK), Hayden Parry, chief executive of Oxitec, explained: “These mosquitoes are ‘sterile’. We only release the males and when they mate with females their offspring die. So there are only two options, either they mate and their offspring die, or the males don’t find a female and they die anyway”.

Releases so far

Cayman Islands (a British Overseas Territory in the Caribbean), Malaysia and Brazil have so far approved open releases. In 2009, Cayman Islands authorities imported Oxitec’s strain and have since released over 3.3 million sterile transgenic male Aedes aegypti mosquitoes in inhabited areas to achieve 80% suppression in the field population.

Malaysia has gone much slower: although it was the first endemic country to import the strain (in 2006), it has taken four years to conduct the limited release of 6000 sterile male mosquitoes in an uninhabited forest on 21st December 2010. Malaysia’s Institute for Medical Research (IMR) did not, however, issue a statement about the release until 26th January 2011. In the meantime, rumours that the release had been postponed were widespread.

IMR said the study – carried out in a remote area of Bentong, a district in the central state of Pahang – was designed to test transgenic males’ survival and mobility. The study ended 5th January, after which insecticides were sprayed to kill any remaining mosquitoes.


The study and plans for further Malaysian releases have been opposed by a coalition of 22 NGOs which claim that genetic engineering can have unintended effects, and that not enough is known about the OX513A mosquitoes and their interactions with other species in the environment. The NGOs have called on the country’s National Biosafety Board to revoke its approval for the releases.

The journal Nature in an editorial [1] has, however, dismissed the concerns of the NGOs, saying, “There is no suggestion that any of the releases was unsafe, or contravened any law. In line with Malaysia’s biosafety rules and the Cayman Islands’ draft rules, permits were issued after the relevant national authorities performed risk assessments”.

Nature says that media reports confused the December release with a second planned experiment, due to take place in a populated area of Malaysia in a few months time. The editorial goes on to call upon the media to report responsibly without mixing up facts, and that researchers, “…should do more to ensure that the relevant authorities make the relevant facts available, or do so themselves”.

According to a news report in Nature Biotechnology [2], “Although some concerns have been raised as to how information about the trial was disseminated, it seems that controversy over the environmental release of a GM organism has been overblown”. The article points out, however, that previous criticisms of the release of the mosquitoes have included the Ottawa-based ETC Group and EcoNexus of Oxford, which have expressed concerns about the risks of releasing an entirely new strain of organism into the environment. They fear the result might be the creation of an “empty niche”, which other potentially damaging insects might fill, and that there could be affects on organisms higher in the food chain that rely on mosquitoes as a dietary source.

Commentator Mark Benedict [3] has criticised the environmental NGOs, which also include Genewatch UK and the Consumers Association of Penang. He says their arguments are, “…specious, none are specific, others are muddy and a few are so far out there that they don’t deserve a response”. He calls for honest dialogues between scientists, the public and activists regarding GM mosquito risks and points out that “…the scientists who are developing this technology are not making tons of money, have no neo-colonial goals nor desire to introduce harmful technology. They are not dupes of a government conspiracy nor crazed monsters. They are just applying their knowledge and skill to looking for new solutions to difficult problems”.

In the journal Science, however, an article [4] reports that there are concerns amongst scientists who support the release of the insects that the apparent secrecy over the release date (and the confusion as to whether the trial had or had not been postponed ) “may erode public trust and provide anti-GM groups with ammunition”. contacted Dr Seshadri Vasan, Oxitec’s head of public health. He has previously stressed the importance of public engagement in avoiding such problems [5,6]. He told us: “Public engagement is very important not just because it is mandated by the law but because it is the right approach. In this context, Oxitec has always extended full cooperation to the government agencies in various countries responsible for regulating and evaluating our technology”.

Brazil is the planned site of the company’s next experiment.


1. Nature (2011). Letting the bugs out of the bag (Editorial). Nature; 470:139. Available from:

2. Subbaraman N (2011). Science snipes at Oxitec transgenic-mosquito trial. Nature Biotechnology; 29:9-11. Available from:

3. Benedict MQ (2011). Happy New Year! Getting serious about GMO risks in 2011. MalariaWorld; 1 January 2011. Available from:

4. Enserink M (2011). GM Mosquito Release in Malaysia Surprises Opponents and Scientists – Again. Science; ScienceInsider: 27th January. Available from:

5. Vasan SS (2009). Transgenic insects: From laboratory to field (Guest editorial). Asia Pacific Journal of Molecular Biology and Biotechnology; 17(3):53-54. Available from:

6. Vasan SS (2010). Modified insects: Risk analysis and public engagement (Guest editorial). Asia Pacific Journal of Molecular Biology and Biotechnology; 18(2):237-239. Available from:


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