Taking the sting out of dengue

Taking the sting out of dengue

In 2008, it was reported that the Health Ministry would undertake an experiment to release genetically-modified mosquitoes to fight Aedes aegypti mosquitoes, the main carriers of the dengue virus. Was it a success? How effective have we been in efforts to control dengue fever? Deputy director-general of Health (public health) Datuk Dr Lokman Hakim talks to Chandra Devi Renganayar and Suzanna Pillay to get an insight into efforts to combat the scourge.

Question: Where were the genetically-modified (GM) mosquitoes first released?

Answer: Our original proposed trial site was in Pulau Ketam, but our preliminary surveys indicated that the site was unsuitable for the trial. Instead, a trial site in Pahang was found to be ideal and the release was conducted in this site.

The trial, the first open release of male transgenic mosquitoes in Asia, was conducted on Dec 21, 2010, in an uninhabited forest (non-reserve forest land owned by the government off Jalan Tentera/Lebuhraya Bentong-Raub) in Bentong, Pahang.

Question: What was the outcome of the trial? Were the GM mosquitoes able to eliminate the Aedes aegypti mosquitoes as intended?

Answer: The goal of the trial was to understand the dispersal (that is, how far they fly) and longevity of the male OX513A strain dispersal, compared with the unmodified wild type strain under open field conditions. This was not a suppression trial and it was not done to determine the impact of the transgenic males on the Aedes population.

The Institute of Medical Research (IMR) released 6,045 transgenic male Aedes aegypti mosquitoes from the OX513A strain, along with 5,372 unmodified male mosquitoes from its laboratory strain. These two strains were marked with different-coloured fluorescent powder. Using stringent quality control, IMR ensured that the released mosquitoes were all male and cannot bite or spread diseases. The mosquitoes were recaptured using a network of adult traps.

The experiment was successfully concluded on Jan 5, 2011, in accordance with trial protocol. It was carried out in compliance with the National Biosafety Board's terms and conditions.

The dispersal and longevity of the GM Aedes aegypti and lab unmodified Aedes aegypti were similar, indicating that genetic modification (introduction of a single transgene) did not affect the biology of the mosquitoes. The longevity of the GM Aedes aegypti male was two days and the lab unmodified Aedes aegypti, 2.2 days.

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