Modifying Genes in Mosquitoes Could Save Millions From Malaria and Dengue

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MosquitoesGenetically modified organisms (GMOs) are controversial, particularly when it comes to food products. While the results tamper with nature, the effects can be positive. In fact, some attempts at modifying genes could save millions of lives, particularly the recent attempts to modify mosquitoes to be resistant to malaria and dengue fever.

Scientists have created a genetically modified mosquito that is resistant to malaria and dengue fever. The malaria-thwarting mosquitoes are still only in the lab, but real-world tests in the Cayman Islands using the mosquitoes that were modified to fight dengue reduced instances of the fever by 80 percent.

With an innocent sounding name (“Little fly” in Spanish), mosquitoes are the most dangerous species on earth. Unlike other mammals or reptiles that kill, the insects do not do so directly. Their bites are not lethal. It is the infections and/or parasites that they spread from biting an infected person then biting non-infected ones that put them at the top of the dangerous animal list.

The diseases mosquitoes spread are often treatable today, but medicines are largely unavailable in the most affected regions, which are among the poorest in the world. Malaria is the deadliest disease they carry. That disease will strike more than 200 million people this year, according to the World Health Organization (WHO), and will kill about 500,000. Dengue fever affects between 50 to 100 million people each year and approximately 40,000 people die annually of severe dengue symptoms. Mosquitoes also spread encephalitis, yellow fever, West Nile virus and other diseases.

While visions of Frankenstein, mutating bacteria, Dr. Josef Mengele, and questionable foods have people concerned about the concept of genetic modifications, modifying mosquitoes to stop spreading the illnesses would be a significant achievement, which is why several labs have been working on different approaches.

The malaria-resistant mosquitoes being developed had parasite-resistance genes introduced using a gene-editing technique called CRISPR (or Clustered Regularly Interspaced Short Palindromic Repeats) to insert two genes into the insect’s genetic structure to that make them malarial resistant. Those insects then pass on the genetic change to offspring.

Most genetic changes like this only are transmitted to a fraction of the offspring. But the CRISPR approach promotes a higher rate of inheritability, which scientists are the University of California, Irvine, report have created a mosquito that passes on the anti-malarial trait to 99.5 percent of its offspring. That would allow the change to spread quickly through the mosquito population once it is introduced.

The UC Irvine team conducted its tests on the type of mosquitoes that typically spread malaria in India, where more than 1 million are infected annually. They believe that their findings, published in the Nov. 23 edition of journal Proceedings of the National Academy of Sciences. However, there is no reason to believe the approach would not work on other types of mosquitoes too.

Malaria and dengue fever are found in approximately 100 countries, largely in Sub-Saharan Africa and Southern Asia. About 3.2 billion people (about half of the world’s population) are at risk for infection. (A dengue outbreak started in Egypt this past October.) If efforts to modify genes in mosquitoes prove successful, it could save millions from falling ill to or succumbing from malaria and dengue fever.

Written and edited by Dyanne Weiss

Proceedings of the National Academy of Sciences: Highly efficient Cas9-mediated gene drive for population modification of the malaria vector mosquito Anopheles stephensi
Newsweek: Researchers Genetically Modify Mosquitoes to Be Malaria-Resistant
USA Today: 5 most incredible discoveries of the week
World Health Organization: Malaria
World Health Organization: Dengue

Photo by Jim Gathany, courtesy of the U.S. Centers for Disease Control and Prevention