Genetic engineering – a double-edged sword?

I was intrigued – but also worried – to read about the growing use of mutated insects and fish to control pests. New Scientist reports:

In the so-called “sterile male technique”, large numbers of the target pest are bred, sterilised and the males let loose. When they mate with wild females, the resulting eggs are not viable, so releasing enough sterile males can eventually exterminate wild populations.

. . .

The sterile male technique has the huge benefit of being incredibly focused, homing in only on the species you want to control. Pesticides, by contrast, harm a wide range of other species, including us.

So why isn’t the method more widely used? The main problem is that it is very difficult to sterilise animals without harming them in other ways. The usual way of sterilising insects is to zap them with radiation, for instance, which leaves the males weakened. Establishing the optimal dose of radiation for a species is thus crucial – too little and fertile insects will be released, too much and the males will be too feeble to compete for females. Working out the optimal dose is best done in the field, but the task is laborious without an easy way to distinguish sterilised insects from wild ones.

Enter Oxitec, a biotechnology company based just outside Oxford in the UK.

. . .

When the founder of Oxitec, Luke Alphey, first learned about the sterile insect technique from a colleague in the 1990s, he realised that the molecular tools he was using in his everyday research might provide a better alternative. Within a matter of years, he had created fruit flies with genes that kill their offspring.

In theory, unlike zapping animals with radiation or chemosterilisation, the genetic approach should work well with just about any species. … Oxitec is targeting the mosquito Aedes aegypti, the single most important carrier of dengue, a viral disease that affects 50 to 100 million people in tropical regions every year, including a few in Florida and Queensland, Australia. Usually the symptoms are mild, but around 1 in 20 people become seriously ill. There is no vaccine and no treatment, so the only way to combat the disease is to kill the mosquitoes that carry it – and they are becoming resistant to pesticides.

Alphey and his colleagues have created a strain of A. aegypti with two copies of a gene that disrupts the development of offspring. The gene is switched off in the presence of the antibiotic tetracycline, allowing large numbers of perfectly fit mosquitoes to be bred for release. “With our system, the mosquitoes are fundamentally sterile and we’re keeping them alive by giving them an artificial antidote,” says Alphey. The insects also have the DsRed marker gene, to enable them to be easily monitored.

When these mosquitoes mate with wild females, the eggs hatch and the larvae develop normally until they reach the pupae stage, when the killer genes kick in. Delaying death like this is actually a cunning trick: the doomed larvae compete with wild larvae for resources, further reducing their numbers.

. . .

While Oxitec is leading the way, many other groups around the world are working on similar approaches – and not just for killing insects. “On technical grounds, there’s no reason why the logic of sterile insects could not be transferred to vertebrates,” says Ronald Thresher, an ecologist working for Australia’s national scientific agency, CSIRO.

He thinks the autocidal approach could not only be used to control invasive species such as cane toads, but that it is the only method that could work in many cases. “It’s the only hope we have for the long-term control and eradication of these pests,” he says. “Other efforts help, but in the end they are Band-Aids in the absence of a real solution.”

Thresher has come up with a way to create fish that produce only male offspring. Releasing enough of these “daughterless” fish into the wild, with each passing on the daughterless habit, would turn a thriving invasive population into a bunch of reluctant bachelors destined for extinction.

There’s much more at the link. I urge you to read the full report. It’s very interesting . . . but it also disturbs me. What if some unfriendly or rogue state – for example, Iran, North Korea, or the like – were to get hold of this technology and modify it for nefarious purposes? For example, what if a mutated strain of honey bees could be released, that would kill off the ‘regular’ honey bee population in Europe or the USA over the course of a year or two? We rely on honey bees to pollinate many of our food crops. If they die, the crops can’t reproduce. We’d starve. That’s why so much attention has been paid to colony collapse disorder, because it threatens our food production.

This new technology appears to be very much a two-edged sword. Let’s hope we don’t get cut by it in the wrong hands . . .

Peter