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Anti-GM groups attempt to sully transgenic control of dengue fever

Genetically engineered mosquitoes developed by British biotech firm Oxitec as an approach to controlling dengue fever have been caught up in controversy since 6,000 of them were deliberately released to an uninhabited forest in Malaysia in a trial in December 2010.

The move took many local people and international observers by surprise. For the most part, the problem was not that the mosquitoes were GM or ineffective – previous trials in the Cayman Islands were very successful. Rather the locals took aim at the lacklustre efforts made by Oxitec and the Malayan government to consult and notify the public about the trials (see  GM mosquitoes wipe out dengue fever in trial and Letting the bugs out of the bag).

Unsurprisingly anti-GM campaigners went for the company’s jugular over the incident, and have been trying to bring them down since. In the latest thrashing, green groups including GeneWatch and Friends of the Earth say Oxitec tried to hide results showing the GM mosquitoes could survive in the wild (Daily Mail).

The Aedes aegypti spreads dengue fever.

Oxitec engineered the males so that they will die unless they are given the antibiotic tetracycline which is not generally available once they are released into the wild. The green groups obtained a study showing that 15% of the offspring of lab-bred GM mosquitoes survived when fed on cat food which contains low levels of tetracycline. Tetracycline can sometimes be found at low levels in the environment. This represents a “failure of the technology”, they say.

The green groups have made “inaccurate public assertions” with the purpose of causing “anxiety” about GM technology and its the regulatory process, counters Oxitec. Given how the Daily Mail covered the story,  Oxitec has a point.

The green groups’ claims have “no substance as they could have known had they asked us about any part of it,” Luke Alphey co-founder and chief scientist of Oxitec told Nature.

In further studies Oxitec investigated whether the tetracycline levels that can be found in the environment are likely to lead to survival of the mosquitoes.

“While tetracycline can be found in the environment in isolated areas it is not present in sufficient quantity to ensure survival of the mosquitoes,” the company says.

About two-fifths of the world’s population are at risk of contracting dengue fever. The green groups “risk undermining the chance of a real solution coming to cultures who have a real problem,” the company says.

The fight continues.

Picture source: Wikipedia. Published under terms of the GNU Free Documentation License. Author  Muhammad Mahdi Karim.


  1. Report this comment

    Helen Wallace said:

    A couple of comments:
    1. You link to an article that claims the trials in Cayman “wiped out” dengue. This is incorrect because dengue is not endemic in the Cayman Islands and there were no reported cases at the time of the trial.
    2. The company has reported at meetings that it achieved suppression of the mosquito population in Cayman, but these results have not yet been published. Only the smaller, earlier part of the trial, which studied mating effectiveness has been published.
    3. The Cayman trials (where 3 million mosquitoes were released before the smaller trial in Malaysia) were controversial because there is no biosafety law covering the regulation of GMO releases in Cayman and because local people were told the mosquitoes were “sterile” and not that they were GM.
    4. Oxitec has repeatedly referred to its GM mosquitoes as “sterile” but they are not. They mate and produce progeny which are supposed to die before adulthood. The company has reported a 3% survival rate of progeny in the lab. The new document revealed today shows a 15% survival rate when the mosquitoes were fed on cat food containing low levels of tetracycline contamination.
    This information has major implications for the risk assessment for open releases of these insects. Documents released to the UK parliament and following Freedom of Information requests blacked out the 15% survival rate, hiding important information from public view.

    1. Report this comment

      Hadyn Parry said:

      I would like to draw your attention to a statement released today by the director of the Cayman’s Mosquito Research & Control Unit, Bill Petrie, in which he states that Oxitec mosquitoes did not persist in the environment link following our successful trial.

      The article also notes ‘Petrie said that some of the claims by Genewatch and Friends of the Earth were inaccurate, in particular regarding the lack of regulations for bio-study in Cayman’

      It is also wholly inaccurate to suggest that Oxitec has avoided regulation or deliberately tried to mislead people by blocking information from public view. The institutions who determine the acceptability of any new public health technology are that nation’s regulators, and Oxitec is resolute in its commitment to working within a transparent regulatory environment. This means sharing all research with these experts.

      For further information please see our full statement link

      The Cayman trial has been submitted for publication and we would be delighted to supply you a copy once published.

    2. Report this comment

      Carlos Figueroa-Aranda said:

      The best that can be said of the Genewatch attack on Oxitec is that they have not done their homework; the probability that transgenic Aedes aegypti will encounter tetracycline in their larval diet is close to zero. Elementary knowledge of the biology, ecology and environment of the target insect will make this clear.

      In its original habitat in the African forest, Ae. aegypti breeds in water in tree-holes, rock-holes, plant axils, fruit husks and other small natural containers. It mainly bites rodents but a “domestic” form has adapted to the urban environment where an abundance of hosts (people) and of artificial containers—particularly in “throw-away” societies—provides prolific breeding sites. This is a crucial point: the standard description of the species begins: “Aedes aegypti is a container breeding species”.

      The great majority of infested containers are less than 50cm in diameter and a large proportion of these are less than 20cm in diameter. Among the most favored are old used tires, discarded buckets, watering cans, flower-pot saucers and any other small water holding containers. Natural containers in the same environment include coconut husks, cut bamboo stalks and the axils of ornamental plants. Water barrels and other water storage vessels can also be infested but their productivity in terms of emerging adults is often very low.

      The domestic form of Ae. aegypti is exclusively a creature of the urban ecosystem.
      It is rarely found more than 100m from human habitations and is NEVER present in ditches, ponds or other “ground water”. There is a single publication that reports the presence of larvae in the second-stage compartments of domestic septic tanks that contain fairly clear water (i.e. after the sedimentation compartments). The article is recent and was accepted for publication precisely because it was so surprising. Apart from any other consideration, the larvae of the species are unable to cope with sewage-polluted water because their access to air is blocked by the presence of organic surfactants. Indeed, the standard description of the ecology of the species states: “Aedes aegypti only breeds in clean water”. In any case these are septic tanks for human waste, not battery farms. I doubt many people live within 100m of battery farms or sewage treatment ponds.

      It is true that sewage-polluted water can breed colossal numbers of mosquitoes but these are foul-water breeders, principally Culex quinquefasciatus, the Common House Mosquito. The larvae of this species are equipped with well-developed valves that can cope with organic pollutants and surface-active material. The pupae have a fascinating response: they blow a bubble through their breathing “trumpets”. This puches molecules of surface-contaminating compounds apart until the bubble bursts through into the air!

      The biology and ecology of mosquitoes is fascinating but those who attack Oxitec— however innocent they may be in their motives—ignore a much more important issue: mosquitoes and mosquito-borne diseases are on a global rampage. New species are appearing in the most unexpected places and exotic diseases are “emerging” where they were hitherto unknown.

      Aedes aegypti is of particular concern because it thrives in the rapidly expanding cities of the tropics. Dengue and chikungunya are a serious public health problem, with tens of thousands of deaths, mainly in children, each year. In my country (Colombia) epidemics are so severe that hospital corridors are filled, schools are closed and tourism on the coast is a disaster. Global air travel ensures the worldwide dispersal of the viruses in infected passengers and rate of increase of global incidence has brought it second only to malaria as a mosquito-borne disease. Another real and present danger is Yellow Fever, also transmitted by Ae. aegypti. At present, human cases—estimated as tens of thousands of cases per year—are in people who live in close proximity to the “sylvatic cycle” in forests where monkeys are present. An accidental introduction to any of the teeming megacities of the tropics could precipitate disaster at a level we normally associate with influenza epidemics.

      What the public needs to know is that, at present, we have absolutely no success in controlling the species. Even in countries that spend tens of millions of dollars on pre-emptive control, dengue and chikungunya are rife. In my country, when outbreaks happen, our government resorts to “fogging” with poisonous insecticides such as malathion, sprayed from trucks and even aircraft. It’s the same in all of Latin America. The strategy is highly visible to the public (loud noise, nasty smell, flashing light) but has very little impact on the target insect, mainly because it rests indoors. It is also worth noting that these are products in a group that were developed as poison gases during World War I.

      There is therefore an urgent need for new approaches and new tools to protect urban populations. I believe that the development of transgenics such as RIDL is an exciting approach in an otherwise dismal picture. It may not solve the world’s problems but it would be shameful if it were to be torpedoed by GeneWatch or any other organization with a knee-jerk reaction to innovation and a disregard for the ecology of this threat to human health.

      Carlos Figueroa-Aranda
      Cartagena, Colombia

  2. Report this comment

    Michael Chisnall said:

    Why would green groups ask about it? They have a long history of basing their campaign against genetic modification on nonsense that they could easily double-check but won’t. The Dunning-Kruger effect strikes again.

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    Alan Dewar said:

    It would seem that Genewatch and Friends of the Earth have become the alternative self appointed regulators of novel control technologies in crop protection. As I understand it, the use of GM mosquitoes has not yet been approved in any country, but is still undergoing assessment in a number of countries where this disease is endemic. Why can’t Genewatch and FOE let the regulators assess the viability and safety of Oxitec’s novel solution to the Dengue fever problem? I think I would trust their balanced judgement over the biased views of anti-GM crusaders who have their own agenda.

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    John Sime said:

    I worry when obvious scaremongering is used to try to scupper work that has significant beneficial potential for people in the third world. The motives of those concerned must be questionable.

  5. Report this comment

    H T said:

    Really, anti-GM groups opposing anti-dengue GM research using evidence from a study that fed GM mosquitoes cat food. Apparently, they have no qualms about the real-life applicability of a study that fed mosquitoes, GM or not, cat food.

    Is it their strategy to gather support from people with no common sense and incapable of simple judgements? They could have scored a point on the 3% survival in lab conditions with implications of further selection leading to eventual resistance. Just mentioning DDT would be enough to put the Oxitec people in their place. But no, they have to focus on cat food, which I’m sure would be the target of the next anti-dengue or malaria campaign, or sewage, which might have been an effective weapon in suffocating these Ae. aegypti larvae.

    @Helen: the trial did not wipe out dengue, it wiped out the mosquitoes, which would be sufficient to have wiped out dengue anywhere and would be better than just wiping out dengue, unless you are a mosquito bite advocate

    I’m no fan of GM mosquitoes or Oxitec, especially with alternative options (Wolbachia?) on the horizon. However, these anti-GM groups managed to discredit themselves beyond my belief. If I had been a conspiracy theorist, I would think that Oxitec paid them to make such claims.

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