Genetically modified mosquitoes have made a significant impact in reducing wild populations of the disease-spreading insects in the West Bay release area.
Researchers documented a “62 percent suppression rate” in the release area, compared with a control area, also in West Bay, where only traditional methods of containing mosquitoes were used.
The results of this monitoring are revealed in the first report of the so-called “Friendly Aedes aegypti project,” a partnership between government’s Mosquito Research and Control Unit and British biotech firm Oxitec. It tracks the impact of the Oxitec mosquitoes from the first release in July 2016 through the end of June this year.
The approach involves the release of genetically modified male mosquitoes, which carry a “self-limiting gene,” preventing their offspring from surviving to adulthood. The genetically modified strain also carries a fluorescent marker, which is passed on to their offspring, enabling researchers to track the extent at which they are mating with wild females.
Monitoring of larvae found in traps shows that the genetically modified males are successfully mating with wild females and “competitively overwhelming the wild males in the release area,” according to the report.
“The impact on the wild population is already visible and we are now observing a 62 percent suppression of the Ae. aegypti population in the area after the start of the wet season,” the report states.
Renaud Lacroix, Oxitec project manager, told the Compass the results were in line with what was expected. He said the effect would increase over time with the continued release of genetically modified males.
The report notes that the Oxitec mosquitoes were initially slow to make an impact.
The number of insects released into the wild had to be increased from 300,000 per week to around 400,000 per week at the end of 2016.
At that stage, the level of mating between the genetically modified and wild mosquito populations was lower than expected, which project leaders attributed to a higher than anticipated wild population.
Increasing the number of genetically modified males released helped overwhelm and suppress the wild mosquitoes during that period, according to the report.
The report indicates that the tactic was effective. Between November 2016 and May 2017, monitoring of traps indicated that the target of 50 percent of larvae coming from Oxitec males had been reached and surpassed.
Despite seasonal variation in both the release area and the control area, the report indicates sustained impact of the genetically modified mosquitoes throughout this year: “The release area has shown consistent lower levels of infestation for the whole of 2017, confirming that the population has been suppressed.”