GM Mosquito to wipe out own population

Based on the number of humans killed every year, mosquitoes are the world’s most dangerous creatures, chiefly because they’re the vectors for a whole raft of viral and parasitic infections that they spread when they bite. Indeed, some dub them “flying hypodermics”. Now a US company, called Intrexon, and their UK subsidiary Oxitec, have announced that they’ve come up with a possible solution: a genetically modified mosquito in which only the males survive. Pretty quickly, the targeted mosquito population - and its ability to spread deadly diseases - crashes. Chris Smith spoke with Chief Scientific Officer Tom Reed...

Tom - We have engineered mosquitoes that will pass a gene that will kill all female progeny. So what we've done is we've engineered male mosquitoes that when they mate they pass the gene to all of the male larvae and to all of the female larvae, and only the female larvae die.

Chris - And how are you making that sex distinction?

Tom - There are certain regulatory elements that differentiate between male and female expressed genes, and so we can control the expression so that it will only lead to the expression of the lethality product in the females and not in the males.

Chris - Essentially, a genetic switch, then, that turns on in the females but not in the males?

Tom - That is correct.

Chris - Why does it wipe them out?

Tom - There are certain biological functions that require a use of energy, and so what we've done is we've overexpressed a protein that leads to a great deal of energy use and you burn out the cell's ability to keep up.

Chris - It's a bit like leaving the lights on for too long. You waste loads of energy and they haven't got energy to put into useful things like growing and mating I suppose?

Tom - It's actually the larvae that cannot go to the next level of development because you burn them out before they even go through development.

Chris - Presumably though, you do need a founding population of males to get this process started in the first place?

Tom - Very good question. So our first-generation mosquito was not male selective. You would have to manufacture both males and females and then use size selection to sort the males away from the females. So our second-generation product is one that we are able to actually select only for the survival of the male mosquitoes, and then when we release the male mosquitoes in the population every male child that’s born will then breed and pass that gene until the population collapse occurs.

Chris - Because it's only going in one direction, I suppose, because any female that breeds with one of your genetically altered males, all of the male progeny will survive and will inherit it and they'll go and meet with more females, so it should grow exponentially to start with until you saturate and then the population is just going to be wiped out?

Tom - That is correct.

Chris -  Do you know if this is going to work in the wild?

Tom - We recently gave a press release that indicated the successful use of this in Brazil showing that our mosquitoes suppress mosquito populations in the field at 96%.

Chris - The population falls by 96%?

Tom - That is correct.

Chris - Is this safe in the environment though? Could that not have environmental consequences?

Tom - This is an invasive species. Aedes aegypti is from Egypt, and these day-biting mosquitoes came via shipping to Brazil and there were no natural enemies for these mosquitoes. So we’re not having any negative impact on the wild-type environment, we're actually removing a detrimental organism from that environment.

Chris - And there's no danger the gene could jump ship and end up in a native species, mosquito or otherwise?

Tom - No. Aedes aegypti will mate with Aedes aegypti. And actually for other mosquitoes that carry different diseases we have to create a version of that unique species in order for it to go after other diseases like malaria.

Chris - I'm glad you brought that up because that's what I wanted to ask you about next which is okay, you proved the point with Aedes aegypti which spread diseases like Zika, but they're not the most nasty, dangerous animals in the room because the Anopheles mosquito that spreads malaria probably are. There are hundreds of millions of cases of that around the world every year aren't there? So can this technology be used in them?

Tom - Absolutely. And I'm pleased to say that the Gates Foundation is working with us to develop this technology within the Anopheles species so that we can combat malaria.

Chris - Now the difference there is, though, that the Anopheles mosquitoes they are native to the geography in which they spread malaria, so rather than them being an invasive species  and you being able to say well, what we're doing is removing an invasive from the environment, you're actually going after something that should be there, so this is a slightly different situation?

Tom - Indeed it is. But there is possibility on how you control the releasing and where the releasing occurs that you can start to collapse the population within a defined area.