Why GM mosquitos might be our best bet to stop insect-borne disease.

By Peter Dearden 25/05/2015


Peter K. Dearden

There is a big feature in today’s Guardian newspaper on a company called Oxitec, a company spun out of Oxford University that uses GM mosquitos to battle insect pests, including those that carry human diseases. I have known about this company for a while because I used to regularly meet with its founder Dr Luke Alphey when I was a PhD student. Luke used to work on protein phosphatases, enzymes that regulate the way cells talk to each other, using the geneticist’s workhorse, the fruit-fly, to understand how they work. My PhD aimed to understand how fruit-flies make their nervous systems, and we used to meet at a fruit-fly meeting held every six months at Imperial College in London.

Soon after I moved on, Luke began to work on genetic systems for insect control, and developed a system called RIDL in fruit-flies that provided a potential way of controlling pests.

Insect control is a big problem. In agriculture, controlling pest insects is often difficult and expensive, and in some cases outbreaks of particular species can be devastating to a crop. Insecticides are one part of the solution. Treatment with insecticides provides significant crop protection, but many insecticides are broad range, hitting both beneficial as well pest insects. Agricultural systems desperately need better solutions than these.
In human health insects are also problem. Anopheles mosquitos carry malaria, which threatens 3.2 billion people; 198 million have malaria, and over 500,000 people, often infants and children, die of it each year. There are, in Africa, malaria-carrying mosquitos that are resistant to all currently used insecticides.

Aedes mosquitos carry Dengue fever, a virus that has increased in incidence to infect between 50,000 and 500,000 people, with 6,000 deaths annually.

While you are looking up those nasties, try African River blindness. This is caused by a nematode parasite, carried by black flies (similar to our sandflies), that infects 17-25 million people and causes blindness.

What if you could specifically target the insects that are pests, or disease carriers, and reduce their populations?

Well, in some cases, due to the work of Oxitec and others you can.

Oxitec provides GM insects that carry a poisonous gene. This gene kills cells, unless the insects are treated with an antidote. This antidote allows vast numbers of insects to be raised in the lab, and then released to mate with wild insects of the target species. Their offspring then carry the killer gene, but have no access to the antidote and thus die. Oxitech also dabbles in the sterile insect technique, which uses a similar genetic trick to produce sterile males. Release of vast numbers of these males then leads to them swamping a population and reducing its fecundity, a technique shown to be effective even without genetic modification.

Oxitec is currently being profiled as it is just about to release its GM insects in China to help control dengue fever. Oxitec’s mosquitos have achieved a 90% reduction in Dengue carrying mosquitos in Panama. Oxitec’s GM cotton boll worms have been found to be effective in cotton-boll worm control in the U.S. in small trials.  These technologies seem to be very effective in pest control, killing only the pest species, and not spreading the modified genes around. At least that is what the publications say. You do have to worry about the potential for the gene to be transmitted to related species, the impact on predators of the pest you are targeting and the fact that there is no mechanism to get the gene you have inserted back if it turns out some insects can cope with it. But the technology looks promising.

So could we use this technology here? We have lots of insect related problems (the Argentinian stem weevil and clover root weevil for example). The answer is almost certainly not. Our GM regulations would make this a hard road to take. Indeed, some of these technologies were invented first in New Zealand by the great Max Scott of Massey University. He, and his insect control techniques are now based in the U.S. as he couldn’t get funding to produce a solution to blowflies that might use GM.

We are reduced to spraying broad-range insecticides*, because our regulations mean that world class research on genetics solutions can’t get funding here. We damage beneficial insects, pollute groundwater and risk long-term environmental damage because of the potential risks of a technology. We can’t, in this country, even measure those risks because we are not allowed to.

We need to think carefully about genetic technologies because, while they carry risks, those risks may be much more palatable than the ones we are taking already.

 

*As another potential solution to this problem, my group is attempting to develop novel insecticides that are, at least, friendly to bees.