Scientest warns genetically modified mosquitoes could have 'unintended consequences'

Genetically modified mosquitoes could help wipe out some diseases but create new health threats. Photo / James Gathany

Malaria and many other mosquito-borne diseases could be wiped out within a few years thanks to a new way of creating genetically modified insects - but it could also unleash potentially devastating unintended consequences, scientists have warned.

Researchers have devised a method of bypassing a barrier to the rapid spread of genes within a population. They believe that it could be used to spread malaria-resistant genes in mosquitoes to prevent transmission of the disease to people.

However, it could also be used to spread harmful genes rapidly in the wild, which has led other researchers to call for the imposition of strict safety controls over such research in case of an accidental escape from a laboratory.

The scientists have already demonstrated that it works in fruit flies reared in a high-security laboratory. When a genetically modified fly was mated with a normal fly, the mutated gene was passed on to about 97 per cent of the offspring, instead of the usual one-in-three proportion.

The technique works because the genetically modified DNA includes a "cassette" of other genetic elements that make sure the mutation is passed from one chromosome to another within the same organism, in what the scientists have called a "mutagenic chain reaction" (MCR).

This ensures that almost all offspring born as a result of the genetically modified mosquito mating with wild mosquitoes are born with the ability to pass on the mutated gene. This would enable malaria resistance to spread completely within a single breeding season, said Dr Ethan Bier of the University of California, San Diego.

"In the case of malaria, several groups have created genetic cassettes that when introduced into mosquitoes prevent the malarial parasite from propagating," Bier said.

"A major challenge in the field, however, has been devising a way to disseminate these gene cassettes throughout the mosquito populations. MCR offers an obvious solution to this problem since the incorporation of an anti-malaria gene cassette into an MCR element should result in the rapid spread of the gene cassette through the target population," he added.

"For example, if one in 100 individuals initially carried the cassette, the cassette should spread to virtually all individuals in as few as 10 generations, which is less than one season for mosquitoes," he added.

The chain reaction, described in a study published in Science, uses a new method for precision editing of genes, called Crispr. This has an enzyme that cuts and splices chromosomes, enabling a modified gene to be passed between one chromosome and another in the same organism.

However, other scientists have warned about carrying out experimental work without taking adequate precautions against the possibility of escape from laboratories carrying out so-called "gene drive" research.

- Independent