快猫短视频

Pest control can sometimes get out of hand. In 1995, Australia was testing the deadly calicivirus for controlling rabbits on an island. Somehow the virus escaped and spread across the entire country.

New Zealand, which also has a serious rabbit problem, decided not to introduce the virus. But a group of farmers took it upon themselves to smuggle the virus into the country in 1997, where it still circulates today.

Now New Zealand is considering using genetic 鈥渆xtinction鈥� drives to tackle invaders such as rats, possums and stoats. These gene drives are essentially genetic parasites that can spread and wipe out populations.

But leading gene drive researchers are calling for caution, lest history repeats itself. In a paper published in PLOS Biology, they argue that no country should use gene drives to tackle invasive species unless they can be certain they won鈥檛 spread beyond that country鈥檚 borders.

Protected species

Possums, for instance, are protected species in Australia, so it would be a disaster if a possum-killing gene drive was deliberately or accidentally introduced there. Instead, conservationists should release only smart gene drives that cannot spread in other countries.

Natural gene drives have been around nearly as long as life itself. There is normally a 1 in 2 chance that a specific piece of DNA inherited from one of our parents is passed on to any one of our children. But gene drives cheat. They copy and paste themselves from one chromosome to the other, matching chromosome, meaning that all offspring inherit them. In theory, they can spread to every single member of a population.

In 2014, Kevin Esvelt, now at MIT, and colleagues . Such drives, they said, could reverse pesticide and herbicide resistance in insects and weeds, and control damaging invasive species, as well as preventing diseases spreading.

Several CRISPR-based gene drives have now been created. A team at Imperial College London is carrying out lab tests of gene drives designed to combat malaria. Other teams are testing . This approach could be used to wipe out invasive species like rats.

False hope

But it was a mistake to talk about what was technically possible without discussing the social and diplomatic barriers, Esvelt now says. 鈥淭his misled many conservationists, who are desperately in need of hope, to falsely believe that gene drives might be used to humanely remove invasive species without much risk of international spread.鈥� He now thinks that gene drives without some inbuilt safety system should only be used with international agreement.

And we need to be extremely careful just testing gene drives. Some studies have suggested organisms can quickly evolve resistance to gene drives, suggesting that they will not spread very far in the wild unless designed to overcome resistance. But that assumption may be wrong.

CRISPR-based gene drives can be highly invasive despite resistance, by a team including Esvelt suggests. The evolution of resistance would stop gene drives affecting every single organism in a population, he says, but they could still spread very widely.

Because worldwide spread could result from the release of just a few individuals, the team say, gene drives should not be developed nor field-tested in areas where the host organism is found 鈥� contrary to the recommendations of .

But there are potential solutions. Last year, Esvelt鈥檚 team outlined a design for a self-limiting gene drive that vanishes after a few generations. Such a drive could be safely tested and used without risking uncontrolled spread.

Another approach would be look for gene variants specific to invasive populations in particular regions or countries, and design gene drives that only target these variants.

Conservationists should not rush to release gene drives until we can be sure they are safe, Esvelt says. Gene drives have enormous potential for tackling diseases and pests, so it would be a profound tragedy, he says, if an incident with a hastily introduced gene drive led to the entire technology being shelved.