Materia Medica Malaysiana

April 27, 2008

‘Warrior’ mosquitoes to fight dengue scourge

Filed under: Uncategorized — malaysianmedicine @ 9:12 am

NST: The days of the Aedes mosquitoes appear to be numbered, thanks to the efforts of a British bio-tech company and Malaysia’s Institute of Medical Research, writes P. SELVARANI.
MILLIONS of genetically modified (GM) “warrior” Aedes mosquitoes will soon be released into the fishing village of Pulau Ketam off Selangor as part of international field trials to fight the dengue scourge.
The GM male Aedes aegypti mosquitoes, which carry killer genes, will be released into the wild to eliminate the Aedes mosquito population which spreads dengue fever.
The field trials will be undertaken by the Health Ministry’s Institute of Medical Research (IMR) in collaboration with British-based Oxitec Ltd, an insect bio-tech company part-owned by the University of Oxford.
This follows the success of confined lab trials which were conducted under the supervision of the IMR over the past year.
The field testing is expected to be conducted on a wider scale on Pulau Ketam at the end of the year or early next year.
The team is undertaking a baseline survey of the island, which is reported to have a high number of the Aedes aegypti mosquitoes.
Oxitec has advertised on its website vacancies for the Pulau Ketam field-testing job, which includes a position for a senior entomologist.
The field trials on the island, which is a 30-minute boat ride from Port Klang, are expected to be carried out over a year.
Health Ministry and IMR officials did not want to comment on the tests.
In February, Oxitec had announced that it planned to release the GM mosquitoes in Malaysia on a large scale in three years, following its successful trials.
Calcutta’s The Telegraph newspaper had quoted Oxitec’s head of public health, Seshadri S. Vasan, as saying that the first confined field study under the supervision of the IMR “yielded encouraging results”.
Sources said the controlled lab tests done here were the first in the world and was a breakthrough in the fight against dengue, which has grown to alarming proportions across the globe in recent years.
The technique involves releasing GM male Aedes mosquitoes to mate with the female Aedes mosquito. The lethal genes cause the larvae to die.
(Only a female mosquito can transmit the disease-causing germ because it, and not the male mosquito, has a proboscis that is capable of piercing the human skin.)
The Aedes mosquito is the main vector for dengue and chikungunya fever and conventional methods such as fogging have been ineffective in controlling the spread of these diseases.
However, environmental non-governmental organisations fear that releasing these GM mosquitoes in the wild may affect the ecosystem and cause further damage.
Gurmit Singh, the chairman of the Centre for Environment, Technology and Development, said: “Like all GM organisms, once they have been released in the wild, how do you prevent them from interacting with other insects and producing mutants which may be worse than the Aedes mos-quito?”
It is learnt that if the Pulau Ketam field trials prove successful, the next step would be to introduce the killer mosquitoes in bigger towns which have a high incidence of dengue.
The Telegraph had also reported that the sterile insect technique (SIT), which involves releasing millions of sterile male insects over a wide area to mate with the native female ones, had been around for decades.
It said the conventional sterilisation programmes using radiation or chemical treatment to foster sterility, which were tried on mosquitoes as well, did not work.
Irradiation rendered these mosquitoes so sickly and unattractive that their female counterparts shunned them for the wild ones.
On the other hand, mosquitoes subjected to Oxitec’s proprietary technique, called RIDL-SIT, remained healthy and attractive enough to woo the native female insects.
This was proved in independent case studies in Oxford and France and in contained semi-field trials in Malaysia.
Vasan was quoted as saying that the latest study in Malaysia showed that “up to 50 per cent of the wild type female mosquitoes chose to mate with Oxitec’s RIDL male mosquitoes”.
The paper added that Oxitec had received regulatory and import permits for confined evaluation in the US, France and Malaysia.

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