GM mosquito trial: A dangerous precedent

Dr Rosli Omar

Modified 13 Sep 2010, 9:09 am

The National Biosafety Board of Malaysia through the Institute of Medical Research (IMR) is planning to release genetically modified (GM) male Aedes aegypti mosquitoes into the environment for a trial to combat dengue. This release of GM mosquitoes has never been attempted before in the world even though the concept has been around for quite some time.

And as far as is known only one other release into the environment of a GM insect has been attempted before – all others are within controlled environments. This says something about safety concerns on such a release. SOS-Selangor (Save our Rivers) is worried about this release and here we discuss our reasons.

Problems with invasive species - once an organism is released into a new environment, it acts as an invasive or exotic species which at times is detrimental to that environment. And it is recognized that invasive species form the third most important factor for environmental destruction the world over after habitat destruction and overkill of species. Twenty-four rabbits initially introduced to Australia have reproduced so successfully that they are seriously eating and destroying an already fragile ecosystem.

Asian carps introduced to the United States are destroying its freshwater ecosystem and the fear is they are now on the verge of entering the Great Lakes. The US initiated a large scale, including poisoning, campaign against the establishment of the snakehead (of the haruan family) in their ecosystem because they can eat their way to the destruction of that ecosystem (even though they seem to co-exist well in their original habitat).

The cane toad introduced into Australia to solve a certain problem and now eating its way across the land is regarded as a major disaster. In Malaysia, the house crow was introduced to solve some pest problem but they were so successful in adapting to the local ecosystem that they are now in turn regarded as a pest. The Nile perch introduced into Lake Victoria by the Brits as a sporting fish has decimated the lake’s ecosystem and again is regarded as a major environmental mistake. Many more examples abound but those are enough to indicate the folly of introducing a new species into an environment.

And these GM mosquitoes are an invasive/exotic species because they have new traits not available in other mosquito species. Additionally, Aedes aegypti is an introduced species to Malaysia, and is already considered an invasive species. And how the genetic modification would affect these characteristics are currently unknown.

Problems with pleiotropy - one term that we hear often in the discussion of GM organisms (GMOs) is pleiotropy, or unintended consequences. We may think we have planned for every eventuality to safeguard against the negative effects of, for example, release of a GMO but there could possibly be unintended effects, i.e., those that we did not think of.

This is likely especially so of a release of a new GMO into a new environment since we still have a rudimentary understanding of the web of interactions, causes and consequences, in nature. Some of the planned releases of the invasive species mentioned above (and others) have been thought out before hand as to their likely impacts yet disasters still occur. This could happen in the case of the GM mosquitoes. If the unintended occurs, once they are out in the wild, there is no recall.

Another form of unintended consequences could come from the genetic engineering process itself. When a new gene construct from one species is engineered to a target species, in this case the aedes mosquito, the introduction can cause new behaviours apart from the intended ones, for example more aggressive mating or feeding behaviours.. And given that the gene introduction is a random process, each mosquito could potentially have different unintended behaviors from the next.

Problems with the safety precautions - IMR says that the larvae of the mosquitoes will die if there is no tetracycline, an antibiotic, in the water. But this antibiotic, which has been around since the 1950s, is widely used, for example in the treatment of acne, and is also used as a biomarker in wildlife to detect consumption of medicine-or vaccine-containing baits. In genetic engineering, tetracycline is used in transcriptional activation.

Tetracycline is also one of the antibiotics used to treat ulcers caused by bacterial infections. Thus, because of its wide use, it could be present in the water where these mosquitoes are to be released. Have the IMR determined whether the water there has tetracycline in it or not? And have the IMR determined how low the concentration of tetracycline that is enough to keep the larvae alive?

If the larvae are able to survive they could become an invasive species. Once they are out there in the wild it is near to impossible to recall. Because of the above concerns this is why this release, if it gets the nod, will be the first release into the wild of a GM mosquito. Most ecologists would regard the idea of releasing a GM animal/insect into the environment as a serious mistake.

If the larvae survive some of them will develop into female mosquitoes which will then bite humans, a situation that does not arise with the original all male GM mosquito release.

Then there is also a possibility of horizontal gene transfer of the gene construct from the mosquitoes to other species, possibly through the intermediary of bacteria, which could render problems for their procreation, given that the gene in question is sterility inducing.

Problems with the capture plans - to capture or destroy the mosquitoes after the experiment, the IMR plans to capture or fumigate around an area of 200m radius. This is too optimistic. What if storms or strong winds were to occur that would spread the mosquitoes to a much wider area? And their other strategy does not sound any better: ‘These include placing traps to recapture the mosquitoes and continuous daily monitoring of the traps until no marked mosquitoes are recaptured for three successive days. If marked mosquitoes are still being caught after one month, further trapping can be put in place’.

If trappings had been effective surely we would have used them and got rid of our aedes problem long ago. And pleiotropy may rear its ugly head. The expression levels of the fluorescence marker to identify the GM mosquitoes may vary and there could be some GM mosquitoes that may not be identifiable by fluorescence and hence escape detection.

For all the issues discussed, the GM mosquitoes must not be released.

An AFP wire report quotes a Malaysian ministry official as saying that anti-dengue GM mosquitoes had previously been released in a trial in Cayman Islands in the Caribbean. I don’t think this is true. I have done an Internet search using three search engines (Google, Yahoo and Ixquick) using keywords ‘genetically modified mosquitoes Cayman’ as well as ‘genetically engineered mosquitoes Cayman’ but found no such trial whereas the Malaysian proposal generates many hits.

A report on Aug 5 this year only says that ‘the Cayman Islands, Malaysia and Mexico are interested in using GM sterile mosquitoes to tackle dengue’.

The Cayman Islands’ Malaria Control Unit website does not mention any such trial either.

Thus I believe this Malaysian trial, if approved, would be the first in the world. The fact that GM mosquitoes have been around for more than 10 years and the idea to use them to combat mosquito-bearing diseases has been around for much longer but yet no country has ever tried it indicates the extent of the fear that it may have unintended consequences. Don’t let Malaysia be the world’s guinea pig for a British firm – which provides the GM mosquitoes - hoping for a commercial success.

The writer teaches at Universiti Malaya.

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