Can Zika be controlled with GMO mosquitoes and Naled?

Zika

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We take an in-depth look at the Zika virus in Florida and beyond, including hearing from the director of USF Health and from a mosquito control expert on the pros and cons of genetically modified mosquitoes and the insecticide Naled.

Listen to the full show here:

On Monday Tampa Mayor Bob Buckhorn announced a program to try to dump standing water to reduce the number of Aedes aegypti mosquitoes that are the vector for the Zika virus.

On Friday U.S. health officials warned pregnant women to avoid Miami Beach, Florida. That’s the new area where Florida officials announced that mosquitoes have spread the Zika virus to five people. In a statement, the U.S. Centers for Disease Control and Prevention also says pregnant women should continue to avoid travel to Miami’s Wynwood arts district. That neighborhood was the first site on the U.S. mainland where health officials determined mosquitoes were transmitting Zika.

On Friday, the University of South Florida hosted a panel with medical specialists on Zika. It can cause microcephaly and other birth defects. Charles Lockwood, the senior vice president of USF Health, says, “I think [Zika] is the greatest threat to the well-being of American babies since polio.”

Another panelist at USF on Friday was Hillsborough County Health Department director Douglas Holt. He expects Florida to experience a series of smaller Zika outbreaks rather than a massive epidemic.

A pesticide being used in Miami-Dade County has drawn criticism from residents. So after the conference I wanted to find out more about naled, so I asked Robert Novak, a professor in the College of Public Health at USF. He has been working on mosquito control since 1969. He’s also past president of the American Mosquito Control Association.   

Here’s a link to the EPA’s frequently asked questions about naled.

Here’s a link to information about FIFRA.

Here’s a link to information from Beyond Pesticides on naled.

Here’s one option of how to make sure your bromeliads don’t become mosquito traps.

I also asked Novak about the company Oxytech that is meeting some resistance in its plan to release genetically modified mosquitoes in Key West.

We also heard listener comments about our last show — about phosphate mining in Florida. Last Thursday permission for a new mine took another step forward in Manatee County.

Information from the Associated Press was used in this report.

 

  • Elvia Melendez-Ackerman

    Was this program by the AgroChemical companies? What the Dr. Novak forgot to say about Naled was that even when it degrades quickly, it degrades into Dichlorvos, an EPA certified carcinogen that has a half life of five days. He also forgot to say that the EPA has been sued successfully for mistakes made in the past about chemicals deemed safe when they were not and yes Naled is a proven killer of pollinators (which currently give the US billions of dollas/yr). Yes, Puerto Ricans are concerned about Zika but getting our kids with cancer and other ‘fun’ diseases is not our cup of tea. If you don’t want mosquitoes the solution is a no-brainer, you get rid of breeding sites but then again the Pesticide Industry wont get their cut…

    • Michael McCarthy

      “If you don’t want mosquitoes the solution is a no-brainer, you get rid of breeding sites “
      Good luck removing every bromeliad growing in Florida or PR.

      • Elvia Melendez-Ackerman

        I would not even think about removing bromeliads in PR because they are also natural habitats of natural predators (amphibians) of mosquitoes. What we need to remove is the standing water at breeding sites that really matter in urban systems (stormwater drainages, potholes, abandoned properties with pools etc.). Its all about mosquito control (in sustainable ways), its not killing every single mosquito on earth.

        • Michael McCarthy

          This is what you said, “….you get rid of breeding sites”. A. aegypti love to breed in bromeliads. In FL, the mosquito control guys have had to go house to house and put in a Bt tablet in every one in and around the active Zika outbreak. Most of these “stormwater drainages, potholes, abandoned properties with pools etc.” are not ideal breeding sites for A. aegypti (which use small, stagnant bodies which most others can’t – as small as a plastic bottlecap!) but are for many other species of mosquito.
          The idea of the GM mosquito isn’t to get rid of every mosquito on earth, it is to get rid of A. aegypti, which are an invasive species anyway, and stop the spread of Zika (which at this point is a losing proposition).

          • Elvia Melendez-Ackerman

            Did you notice how you avoided addressing my concerns and suggestions? I will try once again to voice them and then I will address your points one by one with scientifically derived statements (not with passion). I can only hope that in return you will address mine supported with statements that are scientifically-based and not passion-driven. Everything I say here you can google it easily and relate to published work. All I ask is for you and your associates not to ignore it.

            My points first:
            You will be happy to know that as of two weeks ago, weekly data from the Puerto Rico’s Health Department shown that the number of new Zika cases has gone way down and that we seem to have past the peak of the epidemic. This has also been the case in Colombia.

            There is growing and solid scientific evidence indicating that exposing humans to pesticides (especially through aerial spraying of organophosphates for mosquito control or pest control in agriculture) is related to increased risk of developing severe neurological disorders and cancer. Pregnant women and children are particularly vulnerable.

            The overuse of pesticides for mosquito control invariably leads to the development of resistance. Mosquitos in Puerto Rico are resistant to 10 different pesticides commonly used for mosquito control as a ‘prevention’ measure there and in the rest of the US. Needless to say what the implications of that are for the control of the diseases that they carry.

            The World Health Organization as well as many published papers indicate that controlling vector borne diseases requires an integrated control plan that relies heavily in environmental management and where bio-control and chemical control are only support strategies not the first options. WHO says that in general we have failed mostly because of our lack of sound environmental management and public education.

            Funds for environmental management of mosquito control have been severely reduced and as a result states and territories rely more and more on the use of pesticides placing the general population more and more at risk from developing conditions related to pesticide exposure.

            The pesticide Naled is not a mosquito-specific pesticide and will kill bees, butterflies and is especially toxic to fish and aquatic life. That has important economic implications to agriculture and ecosystem function both terrestrial and aquatic.

            Biological control of mosquitoes also includes allowing natural predators to do their job at controlling mosquito populations. In Puerto Rico, our bromeliads are used by little amphibians (coquis) which eat mosquito larvae and adults among other things. Amphibians are also highly susceptible to pesticide exposure.

            Food for thought: Healthy urban ecosystems may allow for healthy mosquito control.

            Your points:
            You said
            “In FL, the mosquito control guys have had to go house to house and put in a Bt tablet in every one in and around the active Zika outbreak.”

            The use of Bt is not the same as removing breeding sites all together (which is what I suggested), it is just another form of mosquito control that while biological may also lead to resistance development (to Bti endotoxins) if used inappropriately. Mind you I am not opposed to using Bt if used appropriately. Getting rid of artificial mosquito habitats in homes does not require Bt, it just requires getting rid of them.

            You said:
            “Most of these “stormwater drainages, potholes, abandoned properties with pools etc.” are not ideal breeding sites for A. aegypti (which use small, stagnant bodies which most others can’t – as small as a plastic bottlecap!) but are for many other species of mosquito.”

            There is an incredible amount of published scientific work on mosquito breeding sites and yes they all agree in the tremendous diversity of habitats (natural and artificial). I have yet to read a paper that says that talks about the preference of this species for small bodies of water, but rather stagnant bodies of water in which ever form and size they come. There is an incredible body of literature addressing the A. aegyptis breeding sites in urban public areas which include: vacant lots, storm water drainages, sewer tanks, underground water storage tanks, gully traps, septic tanks (yes many cities around the world still have those) etc. There is no amount of aerial spraying in the world that will help reduced mosquitoes without addressing management of all breeding sites. These artificial mosquito habitats need to be dealt with and should not ignored.

            You said:
            “The idea of the GM mosquito isn’t to get rid of every mosquito on earth, it is to get rid of A. aegypti, which are an invasive species anyway, and stop the spread of Zika (which at this point is a losing proposition).”

            Yes, but let’s use this GM technology when we actually know the system (in the broad-sense) well enough to consider unwanted consequences. It would not be the first of the last time that we use biological introductions to control a problem while we create another. Did you know that the Zika epidemic hot spot in Brazil was a site where GM mosquitoes were released in 2015? Well it did not work. Using this technology without the right kind of information and out of desperation is a form of improvisation. I am always curious that in the middle of all the strategies used to attempt mosquito control we never get to see the mosquito data; we do not even know if the mosquito surveillance design is sound. We just trust that it is. Regardless of the strategy used (environmental, biological, chemical) our mosquito control responses should be driven by the mosquito data and not by the Zika epidemiological data because after all this Zika virus is also sexually transmitted…

          • Michael McCarthy

            “You will be happy to know that as of two weeks ago, weekly data from the Puerto Rico’s Health Department shown that the number of new Zika cases has gone way down and that we seem to have past the peak of the epidemic. This has also been the case in Colombia.”
            This is due to the number of people not having been exposed to Zika diminishing, that is to say immunity is developing within the populace.

            “There is growing and solid scientific evidence indicating that exposing humans to pesticides (especially through aerial spraying of organophosphates for mosquito control or pest control in agriculture) is related to increased risk of developing severe neurological disorders and cancer. Pregnant women and children are particularly vulnerable.”
            Please point to where I suggested spraying for mosquitoes was either good or bad.

            “The pesticide Naled is not a mosquito-specific pesticide and will kill bees, butterflies and is especially toxic to fish and aquatic life. That has important economic implications to agriculture and ecosystem function both terrestrial and aquatic.”
            Please point to where I supported spraying with Naled. Probably rather problematic since I never once mentioned it.

            “Biological control of mosquitoes also includes allowing natural predators to do their job at controlling mosquito populations.”
            Are you attempting to tell me something I don’t know?? Meanwhile, biological controls don’t sufficiently reduce mosquito populations to control an outbreak of mosquito borne illnesses.

            “The use of Bt is not the same as removing breeding sites all together (which is what I suggested)”
            Can you make up your mind?? I said good luck in removing all of the bromeliads, you said you don’t want to get rid of them, I said they are using a biologic in FL in bromeliads, you say that isn’t the same as removing all breeding sites as you suggested. So, do we get rid of the bromeliads or not???

            “I have yet to read a paper that says that talks about the preference of this species for small bodies of water, but rather stagnant bodies of water in which ever form and size they come. “
            There are plenty. Here is just one.
            “Aedes aegypti exhibits a great deal of specialization in breeding site selection and consequently the distribution of this species is limited by those sites”

            “Yes, but let’s use this GM technology when we actually know the system (in the broad-sense) well enough to consider unwanted consequences. “
            What unwanted consequences. You are releasing males of a specific species which is invasive. Therefore the control only affects this species and can’t have any effect on anything that eats them. Win, win. See: screw flies

            ” It would not be the first of the last time that we use biological introductions to control a problem while we create another.”
            In those instances, that was introducing another non-native to try to control an invasive, which is completely different.

            “Did you know that the Zika epidemic hot spot in Brazil was a site where GM mosquitoes were released in 2015? Well it did not work.”
            Not entirely true. They did achieve a 95% reduction in Aedes but the epidemic was already raging.

            ” Using this technology without the right kind of information and out of desperation is a form of improvisation”
            I will redirect you to screw flies.

            ” I am always curious that in the middle of all the strategies used to attempt mosquito control we never get to see the mosquito data; we do not even know if the mosquito surveillance design is sound.”
            Maybe that is true in PR. Here in FL, I can access this information. I can know what the primary type is in my county during the rainy season, what the density is, when and where they are most likely to bite.

            “Regardless of the strategy used (environmental, biological, chemical) our mosquito control responses should be driven by the mosquito data and not by the Zika epidemiological data because after all this Zika virus is also sexually transmitted…”
            So, you are saying that there was no need to up mosquito controls in FL because they could not find a mosquito infected with Zika? That the epidemiological data which ruled out other avenues of infection should be ignored? Yeah, but no.

          • Elvia Melendez-Ackerman

            I’m baffled at your responses but since you took the time to read what I wrote. I’ll answer. Please pay attention.

            You said:
            “This is due to the number of people not having been exposed to Zika diminishing, that is to say immunity is developing within the populace.”

            I totally agree, I never said that I did not know the mechanism by which Zika cases were diminishing only that you would be happy to know that the number of Zika cases are diminishing in PR and Colombia. You are happy to know…right?

            You said:
            “Please point to where I suggested spraying for mosquitoes was either good or bad”
            “Please point to where I supported spraying with Naled. Probably rather problematic since I never once mentioned it.”

            You have beautifully made my point. My original posting about the UF talk was about the ills of using chemical (Naled) mosquito control, but you and others keep ignoring it as if the problem will go away. Are you or not in favor of Naled aerial spraying in Florida and if you are, what is your take on the scientific evidence against the use of Naled? Don’t be afraid to make a statement but use strong scientific evidence to refute it. We are using a neurotoxin to control mosquitoes and there is science that says that it may not be safe. What is your scientific opinion on that?

            You said:
            “Are you attempting to tell me something I don’t know?? Meanwhile, biological controls don’t sufficiently reduce mosquito populations to control an outbreak of mosquito borne illnesses.

            I know that, I never said that biological control alone will lower mosquito populations. It is only one of a number a mechanism that can be used but WHO recommends that it needs to be part of a plan and first and foremost with the implementation of long-term environmental management (getting rid of breeding sites) and strong community-based education programs (mind you, not just internet postings). Current programs in the states (in their practice) emphasize the use of pesticides for prevention and control as opposed to the environmental management required.

            You said:
            “Can you make up your mind?? I said good luck in removing all of the bromeliads, you said you don’t want to get rid of them, I said they are using a biologic in FL in bromeliads, you say that isn’t the same as removing all breeding sites as you suggested. So, do we get rid of the bromeliads or not???”

            We get rid of containers by applying sanitation measures, we get rid of stagnant water from other sources (see my response below) and we monitor if this worked to control mosquitoes.

            In addressing my point about papers that deal with preferences of breeding sites by Aedes You said:

            There are plenty. Here is just one.
            “Aedes aegypti exhibits a great deal of specialization in breeding site selection and consequently the distribution of this species is limited by those sites”

            You are still ignoring my point. I will use the main conclusion of your paper to make it again. Your paper says ‘Aedes aegypti is breeding in a wide range of artificial containers’. Your paper only inspected containers and yes there are a dime a dozen of papers like this. What is important here (and the point that I am trying to make), is that this type of study does not consider other important mosquito habitats in cities which include stagnant water from storm water systems, abandoned properties, vacant lots, gullies, septic tanks. We need data that looks at the relative contribution of mosquito habitat from residential (dominated by containers) vs public areas (stromwater drains, sewer tanks etc.) and this needs to be placed-based. Most of the awareness/education work in the states focuses on breeding sites at residences and not necessarily in the public spaces of cities. You are focusing on bromeliads and containers but cities might be missing more important habitat that need to be controlled. Here are two papers for you. Read them please.
            http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4070300/
            http://www.bioone.org/doi/pdf/10.2987/5655.1

            On the use of GM mosquitoes, you said two things:
            “You are releasing males of a specific species which is invasive. Therefore, the control only affects this species and can’t have any effect on anything that eats them. Win, win. See: screw flies”

            “In those instances, that was introducing another non-native to try to control an invasive, which is completely different.”

            All I said is that you need to know your system well before releasing GMOs, when you simplify it like that it may seem harmless, but you leave out all of the information about your system and which frankly GMO companies need to explain not to me but to the general public. How exactly were the genetic modifications of mosquitoes done and is there any risk of further genetic modification of these mosquitoes while in the wild? Do they really all die? You need to recognize one thing: the companies that have traditionally backed GMO’s have gone to great lengths to prevent the GMO labeling of food products in the US, so there is a lot of mistrust out there when companies resist giving out information. When you simplify things like you just did, people are left wondering what information they are not getting…Its a matter of more transparency when it comes to the public dissemination of the science.

            Anyways, here is a 2010 report from a geneticist voicing her opinion on the subject and emphasizing that the context in which these GM mosquitoes are released may be important.
            http://www.econexus.info/publication/release-gm-mosquito-aedes-aegypti-ox513a

            I have yet to make up my mind on GMs but it would help if this issue were not overly simplified for the general public. People want full disclosure, they can handle complexity and even if they can’t they are owed this information specially when they get to foot the bill.

            You said on the release of GM mosquitoes in Brazil:

            “Not entirely true. They did achieve a 95% reduction in Aedes but the epidemic was already raging.”

            If developers knew that, then, why release GMs at all? Why waste the money? Did Brazil had to pay for that? As you pointed out, doing this kind of intervention once the epidemic is in full motion might be pointless. One interesting thing from the internet: The operation of the GM mosquito farm by Oxitec in Brazil was disclosed in 2012 and was originally developed to addressed Dengue feber. The question is why wait so long to release the mosquitoes for the Zika epidemic?

            By the way, there is a study showing 80% reduction of A aegypti using ovitraps in PR to control A. aegypti and Chickungunya. The funny thing is that if that worked why aren’t we using that in Puerto Rico and Florida? Why are we letting this epidemic spread through the states when there are other means of mosquito control readily available? Mosquito traps can still be used in places where the epidemic has not started but the focus is always on the pesticide use and waiting to use so it seems.

            You said about mosquito data:
            “Maybe that is true in PR. Here in FL, I can access this information. I can know what the primary type is in my county during the rainy season, what the density is, when and where they are most likely to bite.”

            It is true in PR. As for Florida, it is not about you being able to access the information but about the general public. Can we access the raw data or are we talking about accessing only maps and managed cumulative/pooled data? Mosquitoes within cities are not necessarily evenly distributed, so at what scale is this mosquito information being collected and reported? If data is being gathered at the county level only, without good spatial resolution, you are likely to be missing a lot of important information needed for management of breeding sites, for the control of adults and for the streamlining of resources. In any case if you can point out how I can easily get my hands on the raw mosquito data for Florida, I am all ears. I can think of a lot of great class exercises that could lead to discovery using that kind of data.

            You said:
            “So, you are saying that there was no need to up mosquito controls in FL because they could not find a mosquito infected with Zika? That the epidemiological data which ruled out other avenues of infection should be ignored? Yeah, but no.”

            No way! I am not saying that! All I am saying is that 1) if we are going to spray the heck out of a place, we should do it based on mosquito data specifically for that place (small scale); 2) there are likely density thresholds below which the spread of the disease via mosquitoes is likely to be negligible (so do we know this?), 3) Zika is also transmitted sexually and at some point sexual transmission of the virus might be more dominant than the mosquito transmission (do we have a handle on this? NO), 4) interventions like spraying pesticides should respond to specific mosquito density criteria as opposed to phone calls and just the # of say, Zika cases, 5) also once the epidemic is full blown these shut gun approaches to kill mosquitoes might be pointless. It has been shown over and over.

  • morphd

    Some follow-up on Dr. Novak’s comments regarding the genetically modified mosquito:

    The mosquito isn’t technically sterile. The artificial ‘self limiting’ gene, when it’s no longer held in check by the mosquito being fed a tetracycline-containing diet, keeps churning out a protein that over time kills the mosquito. The GM mosquitoes mate with wild females, offspring are produced but those offspring die.

    Dr. Novak: “once we start playing with that genome, who knows what could happen”. For perspective, the Aedes aegypti genome contains over 15,000 genes and half the genome consists of transposable elements – aka jumping genes that tend to hop around http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2868357/ . The genome is as much of a ‘contraption’ as it is a finely tuned machine. Oxitec scientists have added two genes, a fluorescent marker to track the mosquitoes and the self-limiting gene that weakens and eventually kills the mosquito, to that genome. Sure, “anything is possible”, but after more than two decades of making GMO crops the ‘worst’ that has happened is resistance build up to glyphosate and Bt – which are just examples of how evolution works when you put a population under selective pressure – and resistance happened with-non GMOs long before. No monsters have shown up under the bed. People need to think about GMOs rationally not emotionally.

    Lastly – Dr. Novak said there’s no silver bullet. So true. Oxitec has achieved over 90% suppression of Aedes aegyti in multiple locations but they’ve done that by multiple releases of GM males (mostly) each week starting early in the mosquito season and not letting up. As a recently retired plant molecular biologist who got interested in this topic several weeks ago (to the point I bought a little stock in Oxitec’s parent company Intrexon – which itself is a relatively small company compared to Monsanto etc.), I hope Oxitec isn’t pressured into releasing their GM mosquitoes mid season in some last ditch attempt to halt Zika because the risk of failure would be extremely high and their ‘all-GMOs-are-evil’ detractors would be jumping all over it.

    • grinninglibber

      This “spokesman” has stock in the company.
      200+ posts – all for Big-GMO

      • morphd

        GL – if you’d read my post you might have noticed that I mentioned owning a small amount of stock in the company that owns the GM mosquito technology. My (currently just over 230) Disqus posts are public, unlike your ~9000 posts which are private. Despite that I do often notice your “$hill” accusations directed at just about anyone who defends GMO technology from a cadre of anti-GMO ‘misinformation specialists’ like yourself (though I’ll add that your posts tend to be relatively brief and information-deficient).

        In case anyone is interested, here is a link to recent interaction with grinninglibber (who I imagine is scowling most of the time) http://www.motherjones.com/environment/2016/08/genetically-modified-mosquitos-zika-gmo (you’ll need to scroll down to “+ View Comments” to open the comments area).

  • Brian

    This genetic manipulation is a potential extinction level event. Not exaggerating in the slightest. IT CAN KILL US ALL. render us extinct. Read on. From MIT, the Massachusetts Institution of Technology, a world renowned science center. ”

    The Extinction Invention

    A genetic technology that can kill off mosquito species could eradicate malaria. But is it too risky to ever use?”

    https://www.technologyreview.c

    “This meant that with CRISPR, even a two-person team could, in theory, change an entire species. ” “change” including exterminate an entire species. ANY species. Really.

    Add natural gene hopping between species and we are really asking for it.

    This is new stuff, folks, super dangerous, no weapons have even threatened us like this.

    • grinninglibber

      Just wait for the North Korean “special” Anthrax,

      • Brian

        I hate to even contemplate it.

    • morphd

      Brian, this isn’t a gene drive application. It’s basically a ‘slow-acting suicide gene,’ not something designed to spread in wild Aedes aegypti. GM males have to be released multiple times a week throughout the mosquito season in order to suppress the wild population (by mating with normal females that then produce offspring that die). Oxitec has done this in Brazil, Cayman, Panama etc and typically achieves 90% or better suppression of the mosquito. The best traditional methods rarely achieve over 50% suppression.

      • Brian

        It has the gene drive in it. That’s how it accomplished 90% per generation instead of 50%.

        • morphd

          Right now they have to make frequent releases of massive numbers of GM mosquitoes for weeks or months during the season to get that 90%+ level of suppression. With a gene drive approach, they’d probably only have to release a small number of GM mosquitoes once, or at most a handful of times and the transgene would spread throughout the mosquito population through normal breeding.

          Since they want to make money, it’s harder to see how the gene drive could be more profitable than having to make large numbers of releases year after year. Also, I can’t imagine any government regulator would approve a gene drive release anytime soon, if ever. The real risk would be some ‘biohacker’ somewhere acting alone (or a terrorist group) IMO.

          • Brian

            Our FDA already approved the gene drive containing GMO mosquito.

          • morphd

            I think the root of our disagreement is the definition of “gene drive” and the definition of Oxitec’s self-limiting technology. The gene drive requires CRISPR Cas9 to copy itself within the mosquito genome so it’s inheritance doesn’t follow normal genetics.
            Oxitec’s gene does follow a normal pattern of inheritance.
            http://blogs.scientificamerican.com/guest-blog/files/2014/07/mosquito-diagram.jpg
            http://www.oxitec.com/our-solution/technology/the-science/

          • Brian

            Thanks. I’m very glad to hear that they have not approved the gene drive versions discussed in the MIT article. While I’m still wary of releasing any GMO into the wild, this one looks far safer in theory. It’s straight out of Jurassic park, they need lysine/tetracycline. I’ll have to research and think about some more. For instance, what method was used to create the GMO? how precise is it? What other changes were made? What happens if they develop the ability to live without tetracycline? What evolutionary pressures are they under?
            Still, a whole lot better than the Gene Drive versions.
            http://www.dna.com/userfiles/files/Oxitec's_Vector_Control_Solution—A_Paradigm_Shift_in_Mosquito_Control.pdf

          • morphd

            It’s a few years old but here’s a link to a New Yorker article that describes how the GM mosquitoes were originally made http://www.newyorker.com/magazine/2012/07/09/the-mosquito-solution Go about 1/3 of the way down to “It is not easy for an egg to become an OX513A.” to read a description of how the DNA was originally transferred into the mosquito.

            If you want lots of detail on the DNA that went in and how they analyzed the result you can find information in Oxitec’s 284 page submission to the FDA starting on page 18 (33 Mb file!) http://www.fda.gov/downloads/AnimalVeterinary/DevelopmentApprovalProcess/GeneticEngineering/GeneticallyEngineeredAnimals/UCM487377.pdf

            Basically they spliced their two genes (fluorescent identifier and ‘self-limiting’ gene) into a transposon so that the assembly would insert into the mosquito’s genome. They used a transposon from another species so that it wouldn’t move around the genome later – something transposons naturally do (around half the A aegypti genome consists of transposons).

            Based on my understanding of GM crops, I’ll speculate they generated more than one independent GM mosquito line then selected the best one of the bunch to take forward (‘best’ as in a single insertion of the transgenes and progeny that died before reaching adulthood).

            Here is a link to Oxitec’s description of the technology http://www.oxitec.com/our-solution/technology/the-science/

            I’ll speculate on some of your other questions…

            In order to be able to live without tetracycline I’d assume the self-limiting function would need to be disabled by a mutation. You’d have what amounts to a normal Aedes aegypti mosquito with a bit of non-functional transgenic ‘baggage’ along with its 15,000+ other genes. One problem I could foresee is the presence of a still-functioning fluorescent marker gene spreading into the wild population would confound monitoring of the working GM mosquito.

            As far as evolutionary pressure, remember that fresh batches of GM mosquitoes are always released from lab-reared lines which I assume can be monitored for changes over time. It could be that if there’s something about the GM mosquito (like fluorescence!) that allows wild females to differentiate them from normal males, perhaps there could be a selection for aversion to GM males that would make the technology ineffective. Since A aegypti don’t travel very far, it seems that would be a localized issue, at least initially.

            Coming up with with plausible unintended consequences that might be anywhere near as harmful as the diseases spread by Aedes aegypti is a stretch. Of course creative people can come up with all kinds of scenarios that people not familiar with the technology might think would be possible.

          • morphd

            Here’s a link to a blog on Scientific American that describes some possible applications of gene drives to potentially repair environmental damage caused by invasive species http://blogs.scientificamerican.com/guest-blog/gene-drives-and-crispr-could-revolutionize-ecosystem-management/

            Assuming good regulatory oversight, these applications could be beneficial – but I suspect to many without – and even some with – the scientific background to understand the details, this could look pretty scary.