June 10, 2014

expert reaction to new study on GM mosquitoes which produce male-only offspring

Nature Communications published a study showing that genetically modifying mosquitos to distort the sex ratio of their offspring suppressed their breeding capabilities as a population.

Dr Michael Bonsall, Reader in Zoology at the University of Oxford, said:

“This is super cool work.  Reducing mating potential of mosquitoes by modifying sperm is a population suppression technology – the work demonstrates just how important these sorts of GM technologies are at reducing insect vector population sizes.

“This has important implications for limiting the spread of malaria. It will be very exciting to see how this specific technology is now taken forward.

“It’s important to note this piece of work is at a very early stage, and is a long way from being deployed.  Before a modified mosquito could be released into the environment, it would have to pass through a very rigorous regulatory framework.  That framework is firmly in place in the UK.”

“In an intervention like this we have to weigh up the environmental effects against the human health effects.  On the one hand, this species of mosquito is a stagnant water breeder, eaten by fish but not relied on as a food source – fish have a very varied diet.  Similarly it doesn’t eat anything that has to be kept in check.  On the other hand, a million children die every year from malaria.  We can’t afford not to take this approach seriously.”

Dr Luke Alphey, Group Leader in the Vector-Borne Viral Diseases Programme at The Pirbright Institute, said:

“The authors have successfully engineered a genetic system into mosquitoes that leads to almost all offspring being male, rather than the normal situation where about half are female.  This would reduce the number of females and, since males don’t lay eggs, over time reduce or even eliminate a target mosquito population, as the authors show in the laboratory.

“After further testing these engineered mosquitoes might well be useful in the field, so this is a big step forwards.  However the overall goal of this research programme is even more ambitious – to develop a version of this genetic system that will spread itself through the target species, removing females and causing population crash or extinction as it goes.

“If this species were to suffer a population crash, it’s hard to see how significant negative side-effects might arise.  The mosquitoes are not keystone species in their ecosystems.  No other animal is dependent on them for food, and we don’t rely on mosquitoes to eat anything.  They don’t seem to keep out anything more dangerous, not least because they are the most dangerous thing around.  And this technique only affects one species, Anopheles gambiae, among over three thousand known species of mosquitoes.

“If we rely instead on pesticide control we would likely kill non-malarial mosquitoes and many other insects besides.  The genetic approach is much more precise.

“As well as considering potential dangers of controlling this species of mosquito, I would equally consider the dangers of not intervening.  Malaria is a major killer and if we’re serious about saving lives it’s going to take scientific innovation like this.”

‘A synthetic sex ratio distortion system for the control of the human malaria mosquito’ by Roberto Galizi et al published in Nature Communications on Tuesday 10 June 2014.

Declared interests

Dr Bonsall is a member of the Advisory Committee on Releases to the Environment (ACRE), a member of an European Food Safety Authority Working Group on Protection Goals (& previously was on GM animals working group), has worked with the WHO/FNIH on Biosafety of GM mosquitoes has past and current funding from BBSRC and collaborations with Oxitec, but has no direct financial links with Oxitec (although Oxford University does).

Dr Alphey is a non-executive director and shareholder at Oxitec Ltd.  Oxitec is developing genetic control methods for pest insects, though not currently Anopheles gambiae, the subject of this study. He is also non-exec director (chairman) and shareholder at Genefirst Ltd, a molecular diagnostics SME.