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How Scientists Cracked the Zika-Mosquito Genome

The Zika virus was discovered in 1947, but most people hadn’t heard of this mosquito-borne illness until an outbreak in 2015 entered into the world’s collective view.  (Image:  pixabay  /  CC0 1.0)
The Zika virus was discovered in 1947, but most people hadn’t heard of this mosquito-borne illness until an outbreak in 2015 entered into the world’s collective view. (Image: pixabay / CC0 1.0)

The Zika virus was discovered in 1947, but most people hadn’t heard of this mosquito-borne illness until an outbreak in 2015 entered into the world’s collective view. This virus usually only causes mild symptoms in healthy adults, if there are any symptoms at all, but researchers found that an infection during pregnancy can lead to birth defects in the fetus. While the virus itself does not have a vaccine yet, researchers at MIT may have discovered a way to stop the spread of the virus — by eliminating the Aedes aegypti mosquitoes that carry it.

Gene drives

The idea behind the elimination of these disease-carrying mosquitoes is known as a “gene drive” — utilizing specific genetic elements to spread a target gene throughout a wild population. This spread takes place over multiple generations, making it fairly ineffective on creatures that breed slowly or have long life spans, but for small mammals and insects that breed and die off quickly, it can be an efficient way to alter the genetic code of the entire species.

Gene drives rely on the specific genetic code of the organism being modified. (Image: pixabay / CC0 1.0)

Gene drives rely on the specific genetic code of the organism being modified. (Image: pixabay / CC0 1.0)

Cracking the code

Gene drives rely on the specific genetic code of the organism being modified. A gene drive will be unsuccessful unless the entire genome is mapped. MIT researchers may have finally cracked the code for Aedes aegypti, the specific invasive species of mosquito that is carrying the Zika virus throughout North and South America.

While this technique has been used on other creatures, like fruit flies and the species of mosquito that transmits malaria, the gene sequencing for the Zika mosquito was much more difficult — the genome itself contained nearly five times the amount of base pairs as the previously sequenced insects.

These gene drives can be used to alter the mosquitoes in one of two ways. Option one is to change the mosquitoes so they can no longer carry the Zika virus. Option two is to alter the mosquitoes so that only male mosquitoes are born, effectively driving the Aedes aegypti to extinction within a few generations.

The problem researchers are facing is that these creatures naturally adapt to changes in their genetic structure in the wild, so it’s entirely possible that the mosquitoes will adapt to the gene drives. (Image: pixabay / CC0 1.0)

The problem researchers are facing is that these creatures naturally adapt to changes in their genetic structure in the wild, so it’s entirely possible that the mosquitoes will adapt to the gene drives. (Image: pixabay / CC0 1.0)

Wild resistance

These gene drives have yet to be tested in the wild, so even if they are successful under laboratory conditions, it may not be possible to replicate that same success out in the world. The problem researchers are facing is that these creatures naturally adapt to changes in their genetic structure in the wild, so it’s entirely possible that the mosquitoes will adapt to the gene drives. Wild populations will likely develop a resistance to the changes being implemented, and until this can be overcome, gene drives will be unsuccessful.

An ethical dilemma

Altering the genetic structure of wild animal or insect populations is akin to playing God, at least according to some activists who oppose the use of these gene drives. Right now, it is impossible to tell what kind of impact these modifications could have on both the target population and the ecosystem in which they live.

Further-reaching implications might take years or decades to discover. Once the human genome is fully mapped, there is also the fear that this kind of genetic manipulation could be used on human beings to eliminate unwanted traits.

It may take a couple more years before an effective vaccine can be released to the public, and the research may stall depending on funding availability. (Image: pixabay / CC0 1.0)

It may take a couple more years before an effective vaccine can be released to the public, and the research may stall depending on funding availability. (Image: pixabay / CC0 1.0)

Ray of hope

Right now, gene drives are a ray of hope for countries that have been dealing with Zika outbreaks without any hope of a vaccine or a solution. Researchers are currently developing a vaccine for the Zika virus that is in the first stage of its clinical trials. It may take a couple more years before an effective vaccine can be released to the public, and the research may stall depending on funding availability — it is fully funded through the second phase of the clinical trial, but budget cuts by the current administration might remove funding necessary for the trial to continue.

By pairing an effective vaccine with the gene drive that could modify or eliminate the mosquitoes that are carrying the virus, researchers could effectively end the spread of Zika once and for all. By cracking the genetic code of the Aedes aegypti mosquito, researchers have taken the first step to stopping the spread of the Zika virus.

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This article was written by Megan Ray Nichols. If you enjoyed this article, please visit her page Schooled by Science.

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