Tag Archives: malaria

Engineering Mosquitos to Fight Malaria

Mosquitos are the deadliest animal on Earth. They spread diseases like yellow fever, chikungunya, West Nile virus and malaria. Malaria alone killed 435,000 people and infected another 219 million in 2017 according to the World Health Organization. There are widespread efforts to combat mosquito-borne illnesses, including revolutionary new gene editing techniques.

Ethan Bier and Valentino Gantz, biologists at UC San Diego, have been researching gene drives – systems that allow scientists to quickly push genes through entire populations. Typically, genetic information from each parent is combined and passed down to their children. Think back to Punnett squares from high school biology. If one parent has blonde hair and the other has brown hair, the brunette would have to carry a recessive blonde gene for any of their children to be blonde. But, gene drives change that. Gantz and Bier came up with a way to use the CRISPR gene-editing technique to insert self-editing genes into mosquitos, so preferred traits are always passed down. Their research shows these traits can take over entire populations within 10 generations, one to two years for mosquitos.

In a recent talk at UC San Diego Extension’s Osher Lifelong Learning Institute, Bier dove into the details of exactly how gene drives work, and their many potential applications.

Watch — Engineering Mosquitos to Fight Malaria with Ethan Bier — Osher UC San Diego

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Combatting the Scourge

Malaria has been described as “the perennial scourge of mankind,” with over 200 million cases reported annually resulting in up to 750,000 deaths and incalculable misery. The disease is most common in the tropical and subtropical regions that surround the equator, including Sub-Saharan Africa, Latin America, and Asia, but it may be found in any region where climatic conditions favor the growth and spread of the mosquito-borne parasite.

On-going global eradication efforts employing pesticides have been successful in southern Europe and the southern United States, but less so elsewhere. In recent years genomics has taken center stage in malaria research with the sequencing of both the malarial parasite and the human genome. One experimental application of this research is the production of genetically-modified mosquitoes that do not transmit malaria. Another new and promising technique is the gene drive, which combats malaria by introducing disruptive genes into wild populations of mosquitoes that interfere with the development of females.

The use of such radical measures unavoidably prompts serious bioethical concerns, including the possibilities of unforeseen mutations and broader ecological impacts. Ethicists also question whether we have the right to potentially eliminate a species. In her self-described role as a “moral philosopher” Laurie Zoloth (University of Chicago) has written and lectured extensively about these issues, arguing that:

In the 1960s, the world agreed that smallpox was a species worth eliminating. We should feel the same way about A. gambiae. And isn’t deploying a gene drive that specifically targets the mosquito species that carries malaria far better than using chemical sprays, such as pyrethroids, organochlorines and DDT (still used in some countries) that indiscriminately target any insect?

Though malaria and other insect-borne diseases have historically been associated with Third World poverty, Zoloth notes these maladies are no longer the exclusive province of underdeveloped tropical countries. As climate change results in greater and more widespread extremes of temperature, rainfall, and humidity, the range of mosquitoes is likely to increase, and with them the diseases they transmit including malaria, dengue, yellow fever, and Zika. While acknowledging the dangers of meddling with the genetic status quo, Zoloth maintains that preoccupation with those risks is a luxury afforded only to those who are not at risk of losing a loved one to wrenching fevers and severe dehydration.

Zoloth concludes that in that light, gene drives and other genomic-based eradication methods represent the most moral and ethical choice available to scientists.

Watch May We Make the World?: Religious and Ethical Questions with Dr. Laurie Zoloth – Burke Lectureship

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