96 per cent success in wiping out dengue mosquitos in research trial
From Radio Australia
A British research company has reported remarkable results in controlling the mosquito that causes dengue fever.
At a trial in Brazil the company released sterile Aedes aegypti mosquitos resulting in a 96 per cent reduction of the wild mosquito population in the target area after only six months.
This could be very good news for the 50 million cases of dengue fever around the world reported by the World Health Organisation each year.
Presenter: Geraldine Coutts
Speaker: Dr Andrew McKemey, field trial manager, Oxitec, British-based research company
MCKEMEY: It’s fantastic news actually, I mean we’ve been working on this technique for a number of years and we demonstrated in previous studies in the Cayman Islands and again in Brazil that we’ve been able to reduce populations by over 80 per cent. So this new study where we’ve achieved 96 per cent is a great step forward.
COUTTS: And what are you doing to get these results?
MCKEMEY: So we’re a bio-tech company based in the UK and we’ve developed a system whereby we’ve genetically modified Aedes aegypti mosquitos, now these are mosquitos which transmit dengue. We’ve genetically modified them so that we can rear basically sterile male Aedes aegypti, and by releasing these males, now we release males only because males don’t bite, it’s only the female mosquitos that bite. And by releasing these males in sufficient numbers they will go out and mate with wild females in the environment and the genetic modification means that the offspring of these released males which mate with the wild females fail to develop to adults. So by sustained release of these males we’re able to decimate the wild population as we’ve been able to demonstrate in this village.
COUTTS: So you’re actually sterilising when you say genetically modifying?
MCKEMEY: Well no, we’ve actually genetically modified and the clever sort of part of the system is we’ve introduced basically a defect in the genetic component of the mosquito which we rear in the lab, and that requires an antidote to counteract the defect. So in a laboratory or in our mass rearing facility we have an antidote to basically the water they’re reared in. And that allows them to grow up to adult, so you can get adult male mosquitos, and those are what you release into the environment. However in the environment you don’t have any of this antidote so when these genetically modified males mate with the wild females they’re able to pass on the gene which means the offspring have this defect and then aren’t able to develop. So it’s a way of producing what is effectively a sterile male using a genetic system.
COUTTS: Now how confident are you of the success in Brazil and I think the Caribbean did you say, that you could now introduce it in the Pacific where dengue is still a huge problem?
MCKEMEY: Well the Aedes aegypti actually originates from northern Africa and it’s only in the last 200 years or so that it’s spread globally. So it’s essentially the same species which transmits dengue all over the world. So our success with this species in Brazil and the Caribbean we believe would translate to anywhere that this species exists in the world. And we have also done tests from this species collected from different parts of the world to show that it will sort of breed and mate with the same species from other parts of the world. So we’re very confident that what we’ve demonstrated in the Cayman Islands and Brazil can be translated to anywhere in the world which is suffering from dengue basically.
COUTTS: Is there a potential downside that would give rise to an air of caution before other scientists rush out and actually do similar studies and introduce this genetically modified mossie in the Pacific? Is there a cautionary word before that happens?
MCKEMEY: It’s hard to conceive of one. This work is the end of ten years’ worth of careful study where we’ve looked into all the sort of safety aspects, and that’s not just ourselves but regulators in all the countries we’re working with. So independent regulators and ourselves. And it’s hard to conceive of any sort of danger or downside of the technology. In fact where regulators have looked at it, for example in the US, their conclusion is that it’s one of the most environmentally benign pest control systems that’s ever been invented. It’s certainly a lot more sort of environmentally benign than the use of insecticides which we rely on at the moment. So I think it has a real potential to tackle a problem that we’re struggling to tackle at the moment with conventional control methods, such as insecticides. And it is able to do it in a way which I believe is a lot more environmentally friendly.
COUTTS: Is it a downside for the Pacific the fact that this technique might be costly to introduce?
MCKEMEY: It’s difficult to give an exact cost at the moment, but we believe in the long run with the scales of economy it would be equivalent if not cheaper than current pesticide methods that are being used.
COUTTS: Well if Pacific governments in particular are interested in this study and research and the technique, how do they go about getting hold of someone who could introduce it in their part of the world?
MCKEMEY: We’re a company based in Oxford and we’re working in several countries are the moment, but if they’re interested certainly get in touch with us and we’d be happy to talk about how we could work with the government or public health authority in that region to try and introduce this technology.
COUTTS: So what would be the process to do that, I don’t mean politically or bureaucratically, but what would be the process in getting it introduced say in Solomon Islands?
MCKEMEY: You said not politically but just practically?
COUTTS: Yes.
MCKEMEY: Ok so the first aspect would be to link up with a local research group to help out, use local knowledge because our experience is always to work with the local teams on the ground because they know the situation there better than we do. And then with them transfer the technology, and that would essentially be to build a facility which can mass rear these sterile mosquitos, and then introduce a program of sustained release. And the approach would be to start maybe in one island or one portion of a larger island and with sustained release you can achieve control, bring down the wild population. Once you’ve done that you need far less mosquitos to maintain that low level, and then you can move onto another island or another part of a bigger island. And using that sort of roll-out approach you could achieve control of a large scale.
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