If we alter the genetics of insect pests to reduce their populations, what are the benefits and risks?

There could be major benefits in public health (an end to malaria, perhaps), agriculture, native plant and wildlife conservation, and other areas. But to fully understand the risks, we need more research before we release gene-drive modified insects into the environment.

What do you mean by “gene-drive modified”?

A gene drive uses new gene-editing techniques to increase the likelihood that a given gene will be inherited by offspring. Over successive generations, that gene can become more and more common—and potentially universal—in a species.

Gene drives don’t work well in species that reproduce slowly, like humans, because they take too long to have effects. But in animals that reproduce quickly, like insects or small mammals, they could transform a population within a few years or even months.

The Aedes aegypti mosquito, which can spread dengue, Zika, and other diseases, takes a blood meal. Credit

Sounds unnatural.

Actually, a wide variety of gene drives occur in nature. Researchers studied these natural mechanisms throughout the 20th century but until the development of new gene-editing tools like CRISPR/Cas in the 21st century, researchers weren’t able to develop a gene drive.

And now they have?

Since early 2015, laboratory scientists have published studies showing that a CRISPR/Cas9-based gene drive (the “9” specifies a particular protein) could spread a targeted gene through the majority of a population of yeast, fruit flies, mosquitoes, and female mice. Now biologists are proposing using gene drives to address various public health, agricultural, conservation, and other problems where solutions are limited or entirely lacking.

And the benefits are…?

With insects that transmit diseases gene drives could supplement other control methods to reduce or even eliminate the disease. A gene drive could alter the genomes of mosquitoes, for instance, so that they no longer can transmit malaria, dengue, or Zika. A gene drive could even cause a given species of mosquito to go extinct.

In agriculture, a gene drive might be used to control or alter organisms that damage crops or carry crop diseases. That could mean fewer chemicals like pesticides need to be used.

The technology might also help control outbreaks of invasive pests like the woolly adelgid or the emerald ash borer, which are affecting many trees in North America. And it could help conserve threatened or endangered species.

"Fogging" mosquitoes with insecticide is one control method people currently use to reduce the spread of diseases like dengue and Zika. Credit

What are the risks?

Some gene-drive modified organisms might lead to unintended consequences. For instance, the decline—or extinction—of a population could have irreversible effects on other dependent species or ecosystems. It could lead to the establishment of a second, more resilient invasive species. It’s even conceivable that gene drives could be intentionally misused to cause harm, although the gene drive community is actively working to establish safe and secure research practices.

Not something to jump into right away then.

No. Deciding how to move forward with the technology will require careful assessment of both the risks and the benefits. Governments will need to clarify how they’ll regulate gene drives and how regulations will be coordinated within and among nations. The people and communities affected by gene drives will also need to be engaged in making decisions.

Where do things stand right now?

Gene drives are not yet ready to test in the environment, but a phased approach to testing—first in the laboratory, then in settings where organisms can be contained—can minimize risks and lead the way toward productive uses of gene drives.

How can scientists safely test gene drives in the environment?

To avoid unintended outcomes, the initial field tests will need to rely on both confinement and containment. For example, organisms could be tested where they can’t survive beyond a confined area. Or they could be contained within an enclosure like a pen or a greenhouse or be isolated on an island. A combination of measures will probably be needed to make sure that organisms can’t spread.

The World Health Organization outlined a phased testing pathway for genetically modified mosquitoes. Each step includes checkpoints to determine whether enough information is available to move to the next phase. Even when an organism is approved for wider release, continued surveillance will be necessary to track whether the gene drive has the desired effects.

What do we still need to learn about gene drives?

To make informed decisions about gene drives, we need many types of information. Biologists, for instance, need to:

  • learn more about how genes function and change over time in populations of reproducing organisms;
  • understand how species in ecosystems interact and the effects of changes in one species on others;
  • develop new ways of containing, monitoring, and altering gene drives.

Specialists in risk assessment, governance, public engagement, and other fields also need to contribute. Social scientists need to learn more about public perspectives and values and the best ways to involve the public in discussions and decisions about gene drives. It’s particularly important for people living in or near sites where gene-drive modified organisms might be released to participate in meaningful ways in making decisions. In all cases, decisions will involve engaging diverse populations, and this engagement will require effort, attention, resources, and planning.

Gene drives might help control outbreaks of invasive pests, like the woolly adelgids that are killing populations of hemlock trees in eastern North America. Credit

And then there’s the question of whether we should do this at all.

Yes, human values will play a big part in decisions about gene drives. Is our role to protect existing species or to actively manipulate the biological world? What is our relationship to nature? Widely shared commitments to protecting human welfare and the environment could require constraining research on gene drives or the release of modified organisms into the environment.

So to sum things up…

As humans gain increasing control over the genetics of living things, hard decisions will need to be made about how to exert that control. Gene drives are a great example. There isn’t enough evidence yet to support the release of gene-drive modified organisms into the environment. But the potential benefits of this technology for human health, agriculture, and conservation justify continuing to explore it.

Know it all? Prove it.