By Calvin J.
Mosquitos have become more than just a nuisance, particularly for the residents of Florida Keys. With the mosquito-borne Zika virus spreading out of South America and a number of travel-associated cases already popping up in Florida, pressure is rising as the state prepares for a possible outbreak. However, it isn’t all bad news, particularly for the British biotech company, Oxitec. If the name sounds familiar to you, its likely because Oxitec has recently received a publicity boost as the FKMCD (Florida Keys Mosquito Control District) announced a potential trial release of their genetically modified (GM) mosquitos to combat mosquito-borne viruses.
Genetically Modified WHAT?
While Zika seems to be dominating the news outlets, Florida Keys has long been dealing with a number of other mosquito-borne viruses, including Dengue as well as Chikungunya. So how are GM mosquitos going to help against the spread against these diseases? Oxitec has introduced into their mosquitos a so-called “dominant lethal genetic system”, meaning that they contain a lethal gene that when inherited will result in death. Oxitec’s self-limiting tTAV (tetracycline repressible Trans-Activating factor Variant) gene when expressed encodes the tTAV protein. tTAV is designed to bind mosquito cell’s DNA transcriptional machinery, trapping it and preventing it from producing actual mosquito proteins needed for survival. tTAV also recognizes tTAV regulatory DNA sequences and drives production of even more tTAV. Eventually, the amount of the tTAV protein being produced overwhelms the cell’s protein production ability. All the cell’s machinery which would normally be producing actual mosquito proteins needed for survival is now bound by tTAV. Without the capacity to synthesize essential proteins, the organism eventually dies. So now you might be wondering, how is releasing a bunch of dead mosquitos going to help us? Well, Oxitec was clever enough to design a system such that the tTAV protein can be inactivated using a drug that’s easily supplemented in the lab, but one that isn’t available in nature. The drug, tetracycline, inactivates or turns off the lethality of tTAV to allow scientists to maintain mosquito lines in the lab. (Read more about it here: http://www.oxitec.com/ridl-science/understanding-ridl-science/molecular-biology/)
What Oxitec aims to do, is release modified male mosquitos (male mosquitos are not only promiscuous and should pass the lethal tTAV gene to a large number of offsprings, but males also don’t bite) into Florida Keys. The males should mate with existing females leading to the production of a lot of dead larvae. Without new mosquitos born, the viruses can’t spread.
But Is This Safe?
Traditional methods of mosquito management can be quite expensive, in fact, the FKMCD claim that they spend ~1.1 million a year in efforts to reduce mosquito populations by ~50%. So far, Oxitec has carried out a number of successful trail runs in Brazil as part of a fight against Dengue and demonstrated a ~90% reduction in local mosquito populations. They have also had a number of other smaller successful runs in Panama as well as the Cayman Islands. And with Oxitec themselves covering the majority of the experimental costs, if successful, the FKMCD may be saving money in the long run (depending on administrative, monitoring, and outreach costs of course).
On the other hand, major concerns have been raised surrounding human and environmental safety, including tTAV toxicity and the possibility of the lethal gene transferring to other organisms or into the viruses themselves. First off, the tTAV proteins is non-toxic and poses no threat to birds or pets that might accidentally (or purposefully) ingest a GM mosquito. The protein will essentially be digested just like any other protein. In terms of potential spread, the lethal gene was introduced via a non-autonomous transposable element and has been demonstrated by Oxitec to be be genetically stable (meaning that it is unable to move around the genome or migrate on its own). Researchers has been able to track inheritance of the lethal gene over 100 generations and has observed no abnormalities. Because the gene is dominant lethal, mosquitos carrying tTAV would never make it through 100 generation out of the lab anyways. (Rest of the safety assessment can be found here: http://keysmosquito.org/question-answers-on-gm-mosquitoes/)
Could there be any effects on the environment? What about the organisms that depend on mosquitos for food? Well, mosquitos are unable to mate outside their species and the species in question, Aedes aegypti, (carries Dengue, Chikungunya and Zika) do not have predators in the Florida region that dependent on them as the sole food source. And because the GM mosquitos are essentially born to die, they will not remain in the ecosystem once we stop releasing the GM mosquitos.
At this point investigations suggests Oxitec’s GM mosquitos do not pose any long term dangers to either humans or the environment. And in truth, while Oxitec is a private business with strong interests in turning a profit, they probably wouldn’t be advertising their product if they had reasons to suspect anything might go wrong. Oxitec ultimately remains financially and legally responsible for any potential damage caused by their GM mosquitos. Currently, the FDA is still reviewing information regarding the safety and efficacy of the Oxitec product and are accepting public comments on the draft environmental assessment and preliminary findings so far. (Learn about that here: http://www.fda.gov/AnimalVeterinary/DevelopmentApprovalProcess/GeneticEngineering/GeneticallyEngineeredAnimals/ucm446529.htm).
What Do You Think?
From my research so far, I have to say that I’m completely on board with the use of Oxitec’s GM mosquitos! I think this is one of our most powerful tools against the spread of mosquito-borne illnesses. They are responsible for over a million deaths per year, and while the Aedes aegypti isn’t the only species responsible, it is the one of most concern.
For or against GM mosquitos? Fears and or objections? How would you feel if you were living in Florida Keys? Let us know, down below!
http: //www.fda.gov/AnimalVeterinary/DevelopmentApprovalProcess/GeneticEngineering /GeneticallyEngineeredAnimals/ucm446529.htm