Life, could you stop finding a way already?


It was a cunning plan. All these mosquitos are carrying terrible diseases like dengue fever and Zika, so what if we fired back and gave the mosquitos terrible genetic diseases that decimated their populations? That would serve them right and also reduce their affliction of human populations.

Scientists made it so. They genetically modified swarms of mosquitos to carry a lethal gene, called the OX513A strain, and released them into the Brazilian wilderness to breed with, and taint the precious germ plasm of the native mosquitos.

In an attempt to control the mosquito-borne diseases yellow fever, dengue, chikungunya, and Zika fevers, a strain of transgenically modified Aedes aegypti mosquitoes containing a dominant lethal gene has been developed by a commercial company, Oxitec Ltd. If lethality is complete, releasing this strain should only reduce population size and not affect the genetics of the target populations. Approximately 450 thousand males of this strain were released each week for 27 months in Jacobina, Bahia, Brazil.

Wow. That’s almost 50 million genetically diseased male mosquitos. I hope the scientists said, “Fly, my pretties!” when they dispatched them on their devious mission.

It worked for a while. Mosquito numbers dropped. But then…

Genetic sampling from the target population six, 12, and 27–30 months after releases commenced provides clear evidence that portions of the transgenic strain genome have been incorporated into the target population. Evidently, rare viable hybrid offspring between the release strain and the Jacobina population are sufficiently robust to be able to reproduce in nature.

Uh-oh. Is anyone surprised?

Our data clearly show that release of the OX513A has led to significant transfer of its genome (introgression) into the natural Jacobina population of Ae. aegypti. The degree of introgression is not trivial. Depending on sample and criterion used to define unambiguous introgression, from about 10% to 60% of all individuals have some OX513A genome

They don’t know what effects these other genes will have on the mosquitos.

It is not known what impacts introgression from a transgenic strain of Ae. aegypti has on traits of importance to disease control and transmission. We tested OX513A and Jacobina before releases for infection rates by one strain each of the dengue and Zika viruses and found no significant differences. However, this is for just one strain of each virus under laboratory conditions; under field conditions for other viruses the effects may be different. Also, introgression may introduce other relevant genes such as for insecticide resistance. The release strain, OX513A, was derived from a laboratory strain originally from Cuba, then outcrossed to a Mexican population. The three populations forming the tri-hybrid population now in Jacobina (Cuba/Mexico/Brazil) are genetically quite distinct, very likely resulting in a more robust population than the pre-release population due to hybrid vigor.

Before their experiment, there was one known population of Ae. aegypti around Jacobina, and they understood the genetic properties of those animals and could predict the salutary effect of introducing their lethal gene there. Unfortunately for their clever plan, the mosquito vector used to introduce that gene also had all those other mosquito genes, which have also been introduced into the region, and now they have become three genetically distinct mosquito populations, and their response to the ‘lethal’ gene has become complex and unpredictable. Yikes. Unintended consequences are entirely predictable, not in detail, of course, but the general chaos is.

You know what else is predictable? This.

Oxitec, the company responsible for developing the GM mosquito strain discussed in this article, has contacted New Atlas claiming that the report cited in this article contains “false, speculative and unsubstantiated claims and statements about Oxitec’s mosquito technology.” Oxitec says it is currently working with the journal publishers, Nature Research, to remove or update the article, which now carries a disclaimer.

Clearly, it is the scientists who exposed this problem, not the corporation that released transgenic mosquitos, that have Meddled with the Primal Forces of Nature.

You have meddled with the primal forces of nature, Mr. Beale, and I won’t have it, is that clear?! You think you have merely stopped a business deal — that is not the case! The Arabs have taken billions of dollars out of this country, and now they must put it back. It is ebb and flow, tidal gravity, it is ecological balance! You are an old man who thinks in terms of nations and peoples. There are no nations! There are no peoples! There are no Russians. There are no Arabs! There are no third worlds! There is no West! There is only one holistic system of systems, one vast and immune, interwoven, interacting, multi-variate, multi-national dominion of dollars! petro-dollars, electro-dollars, multi-dollars!, Reichmarks, rubles, rin, pounds and shekels! It is the international system of currency that determines the totality of life on this planet! That is the natural order of things today! That is the atomic, subatomic and galactic structure of things today! And you have meddled with the primal forces of nature, and you will atone!

Let’s be clear here. The scientists behind OX513A haven’t created a monster, the humans of Jacobina don’t have to flee for their lives, they haven’t done something that creates immediate medical issues. No, what they’ve done is increased the genetic diversity of the mosquito population and made the problem of controlling them more complex for future management.


Benjamin R. Evans, Panayiota Kotsakiozi, Andre Luis Costa-da-Silva, Rafaella Sayuri Ioshino, Luiza Garziera, Michele C. Pedrosa, Aldo Malavasi, Jair F. Virginio, Margareth L. Capurro & Jeffrey R. Powell (2019) Scientific Reportsvolume 9, Article number: 13047.

Comments

  1. raven says

    I’m having a little trouble understanding this situation.
    From the OP, “… containing a dominant lethal gene…”
    Well, if it is a dominant lethal, how is it being carried by the laboratory reared mosquitos???
    Presumably, they must have some other genetic mechanism to counteract it.

    “… but its expression is artificially repressed to allow the insects to be reared.”
    From a quick Google search that explains this.

    More interesting is that AFAICT, we are watching evolution in action again.
    Introduce a dominant lethal into a population of mosquitos and you introduce a strong selection agent.
    You are selecting for mosquitos resistant to…the dominant lethal gene.
    And that is what you end up with.

  2. says

    It’s a conditional dominant lethal. Think of phenylketonuria, a genetic disease that is a death sentence…except that if you have a diet free of phenylalanine, you’re fine.

  3. komarov says

    Okay, so any detrimental genes are happily assimilated. Perhaps a more effective strategy could be to breed more successful mosquitoes instead, that happen to resist the various diseases we don’t want them to carry. Of course I have no idea if it’s even remotely feasible to aim for some sort of mosquito disease resistance, much less one that won’t be overcome by the diseases at some point. At the very least it I’d expect it to be a lot more complicated than what was tried here.

  4. Dunc says

    Perhaps a more effective strategy could be to breed more successful mosquitoes instead, that happen to resist the various diseases we don’t want them to carry.

    And then the diseases adapt, and you just end up with more successful disease-carrying mosquitoes.

  5. chris61 says

    and now they have become three genetically distinct mosquito populations,

    You might want to correct that PZ. They aren’t three genetically distinct populations.

  6. PaulBC says

    🎶I don’t know why she swallowed a fly.🎶

    Sorry, I held back, but didn’t we all learn about this as kids? Aside from the old lady who swallowed a fly, one of my favorite “What could possibly go wrong?” ideas is the introduction of cane toads for pest control (which I also remember reading about as a kid in the 70s, actually I think on some kind of laminated supplemental reading card in grade school).

    Maybe cane toads have a bad reputation. i have often wondered in places where cane toads have become a pest if there is some other larger and more dangerous, preferably venomous animal that could be introduced to eat the cane toads. Worth a try, right?

  7. says

    The paper explicitly says, “The three populations forming the tri-hybrid population now in Jacobina (Cuba/Mexico/Brazil) are genetically quite distinct”. It’s in the quote from the discussion that I included.

  8. davidc1 says

    Didn’t America get rid of the Screw worm fly by using the sterile insect technique ,although according to Wikipedia it is making a come back in Florida ,why didn’t they try that in this case .

  9. chris61 says

    Not to be pedantic but … current day Homo sapiens consists of a population of individuals containing variable amounts of Neanderthal and Denisovan DNA. Does that make three distinct populations of Homo sapiens?

  10. Ridana says

    The paper explicitly says, “The three populations forming the tri-hybrid population now in Jacobina (Cuba/Mexico/Brazil) are genetically quite distinct”.

    Yes, but that’s not saying there are now three distinct populations in Brazil. It’s saying that there is hybrid vigor in the resulting tri-hybrid population in Brazil because the 2 that were crossed for the introduced mosquitoes and the native Jacobina population were all originally genetically distinct from each other.

  11. Ridana says

    So to finish my thought… (oy)

    now they have become three genetically distinct mosquito populations

    They have not “become,” they already were three genetically distinct mosquito populations to begin with, and now they are one tri-hybrid population (plus of course the non-hybrid population still extant).

  12. Ridana says

    Oh, how I long for editing capability after posting! ::sigh:: (close italics failure strikes again. my kingdom for a / )

  13. says

    (Cuba/Mexico/Brazil)

    And let me guess, countries like Cuba were not asked for their consent to participate in a large field experiment with genetically engineered mosquitoes?

  14. nomdeplume says

    This is an example of the kind of unintended and unpredicted outcomes of GM organisms that is the reason for my opposition to them. I don’t think eating foods derived from GM crops etc is the problem, as critics of opposition suggest, it is the escape of genes into wild populations with potential for ecological disaster.

  15. methuseus says

    As nomdeplume says, this is the kind of thing that supposedly isn’t supposed to happen with GMO’s. PZ has stated in the past that the “killer” gene for, say, wheat can’t get out into wild populations. Well there’s rye growing along the side of the road in a lot of the country, why can’t those wild grasses get contaminated? Would it make them hardier or less hardy? Would it spread to other farms that are not growing the GMO seed?

    I’m not against GMO just because they’re GM. I’m against the way they’re currently used, and I try to be vocal in that. Something like adding nutrients or making them resistant to disease is worthwhile. Making them resistant to a pesticide that doesn’t end up reducing total amounts sprayed doesn’t seem worthwhile. Terminator genes in plants you grow for food seem to be the same in my opinion. I’m open to my mind being changed, however, if it can be shown that those modifications are for more than just pure profit from the companies.

  16. methuseus says

    Oh, and I forgot to mention, but my first thought on hearing the scheme of releasing genetically modified, sterile mosquitoes, was “How will their biology get around it?”

  17. komarov says

    And then the diseases adapt, and you just end up with more successful disease-carrying mosquitoes.

    Well, yes. I chose “succesful” as a descriptor since – as far as my lay knowledge goes – it doesn’t imply anything beyond certain genes proliferating through a population, which is pretty much what happened in the experiment anyway. I.e. you don’t necessarily end up with larger populations, which would be a step backwards. Realistically speaking, any resistance will be overcome by the diseases at some point. The odds of actually wiping a disease out in this matter are probably low at best. But you might be able to buy time and push diseases back, and the effects might last longer than in this experiment, since there is no disadvantage and no pressure to overcome it.

    So the question then is about efficiency: Are you better off with deterimental genes to reduce population sizes, at the risk of ending up with more and more hybrids that may cause more difficulties?? Or might it be more effective to run the usual arms race of resistances, except you do it with the disease vector (mosquitoes) rather than humans.
    Depending on how you did it you might be able to avoid creating a bunch of complicated hybrid mosquitoes, and when the diseases adapt they’d have overcome something that works for mosquitoes, not humans. So you could also avoid selecting for resistances that will cause problems when trying to inoculate or treat humans.

    But if anyone is up for some mad science that shouldn’t be done and technology that should never be built, how about a swarm of super-efficient robot mosquitoes that suck everything and everyone dry, leaving their biological counter-parts to starve? A pyrrhic victory is still a victory!

    Oh, I forgot: I have a cunning plan…

  18. chris61 says

    @Ridana

    It’s saying that there is hybrid vigor in the resulting tri-hybrid population in Brazil because the 2 that were crossed for the introduced mosquitoes and the native Jacobina population were all originally genetically distinct from each other.

    It’s not even really saying that. It’s saying that there might be hybrid vigor. But in fact that is pure speculation. It’s too early to tell, since there was only one sample collected post-release and in that sample there is, if anything, a slight decrease in the frequency of hybrid mosquitoes relative to what they observed while the releases were still on-going. Presumably if someone does a follow-up in a year or so they’d have a better idea.

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