Outdoor caged trials to demonstrate the efficiency of genetically modified mosquitoes to suppress wild female Aedes aegypti mosquito populations that transmit dengue, chikungunya and Zika were launched in Maharashtra.
Based on the results of the trials which use the Release of Insects carrying Dominant Lethal genes (RIDL) technology, open field trials were conducted.
Logic behind Modified males
Technology uses genetically modified male Aedes aegypti mosquitoes that carry a dominant lethal gene. When male GM mosquitoes mate with wild female mosquitoes the lethal gene is passed on to offspring. The lethal gene in the offspring kills the larvae before they reach adulthood.
Since male mosquitoes do not bite humans, the release of GM males will not increase the risk of dengue, chikungunya and Zika. The open field studies will be conducted for about a year in two villages in Jalna (Maharashtra).
Problems with the plan
1. There are practical problems of raising a large number of mosquitoes needed for vector control – 100-150 [GM] mosquitoes are needed per person for months together.
2. Large numbers of GM male mosquitoes have to be released at regular intervals to compete with wild normal males for mating. Since the larvae die before reaching adulthood, the technology is a “self-limiting approach”.
Alternate means to control mosquito population
Vector control using A. aegypti infected with the bacterium Wolbachia is achieved by using the life-shortening bacteria strain in both male and female mosquitoes. Uninfected wild female mosquito embryos fertilised by Wolbachia-infected males fail to develop, while embryos from infected females fertilised by infected or uninfected wild males survive.
As Wolbachia is maternally inherited, the bacteria are anyway passed on to offspring. Dengue, Zika or chikunguya viruses cannot replicate when mosquitoes have Wolbachia. Unlike the genetically modified males technology, a feature of Wolbachia is that it is self-sustaining, making it a low-cost intervention.