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Current Affairs

Transgenic mosquitoes

Date: 18 September 2019 Tags: Biotechnology

Issue

Genes from genetically-modified Aedes aegypti mosquito were found to have been transferred to naturally-occurring A. aegypti mosquito population in three areas in Brazil where transgenic mosquitoes were released as part of a pilot program to reduce population of disease causing mosquitoes.

 

Background

About 4,50,000 transgenic male mosquitoes were released each week for 27 months (June 2013 to September 2015) in three areas in Brazil.

 Genetic analysis of naturally occurring mosquitoes were done prior to the release and at six, 12, and 27-30 months after the releases to ascertain the effects of the move.

 

Details

  • The transgenic strains can be distinguished from naturally-occurring mosquitoes by using fluroscent lights and filters. It was found that some transgenic genes were found in 10-60% of naturally-occurring mosquitoes.

  • Tthe naturally occurring A. aegypti mosquitoes carrying some genes of the transgenic mosquitoes were able to reproduce in nature and spread to neighbouring areas 4 km away.

  • The genetic strategy employed to control A. aegypti population known as RIDL (the Release of Insects carrying Dominant Lethal genes) was supposed to only reduce the population of the naturally occurring A. aegypti mosquitoes and not affect or alter their genetics.

  • The offspring of the mosquitos are not supposed to grow to adult mosquitoes and reproduce as per claims made by the British company Oxitec Ltd, which had developed the technology and field-tested it in several countries.

 

How Transgenic mosquitoes help in reducing disease burden?

  • The transgenic male mosquitoes released frequently in large numbers would compete with the naturally occurring male mosquitoes to mate with the females.

  • Offspring from the mating of transgenic male mosquito and naturally occurring female mosquito do not survive to the adult stage.

  • This is because tetracycline drug, which prevents the dominant lethal gene from producing the lethal protein during rearing in labs, is not present in sufficient quantity in nature. In the absence of tetracycline, there is overproduction of the lethal protein causing the larvae to die.

 

Implications of the research

The presence of transgenic mosquito genes in the natural population will affect the disease transmission capacity or can make mosquito control efforts more difficult.