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Genocide and Malaria Mosquitoes

  1. May 22, 2003 #1

    LURCH

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    I read an article in this month's Pop Sci detailing a research program aimed at eradicating the mosquito that carries malaria. At first blush, this sounds like a terrific idea. After all, malaria is a horrible disease, killing one million people a year, 5,000 children a day (four every minute), and draining billions of dollars from Third World countries to really cannot afford it.

    However, we are talking about a deliberate campaign to bring about the extinction of an entire species. Also, the program is dependent upon homing endonuclease genes (HEG's), which are said to be of no benefit to the organism which carries them. Apparently, HEG's beat the usual 50/50 odds of being passed to the Next Generation by copying themselves from one chromosome to another. Once all the chromosomes possess the HEG, it is assured of being carried on. This reproductive strategy is quoted as having in 95% success rate, "even though the genes confer no survival benefit".

    All of the experts seem to agree that:

    A) the extinction of the mosquito species Anapheles Gambiae will have little or no environmental impact, and

    B) HEG's are highly successful at reproducing themselves from one generation to the next, without conferring any survival benefit.

    How much confidence do you have in these two conclusions? (I must confess, I harbor some reservations as to whether we, as a species, possess enough knowledge to make such statements with any great certainty)
     
  2. jcsd
  3. May 22, 2003 #2
    Hindsight will be 20/20.
    I don’t know what impact it might have but I’m probably nearsighted enough to say “go ahead”. If serious investigation is put into this beforehand in order to assess, as much as possible, the long term ramifications then maybe that’s all you can ask for. I suppose they could keep some of those mosquitoes alive, under lock and key, rather than completely wipe a species off the earth forever…

    I recall the screw worm eradication program that happened in a Central American country I was living in. I mention this only because I found the technique itself interesting; The female flies would only breed once, so by irradiating box-loads to make the males sterile, the males would be released from planes, satisfy the females, which would then in turn lay unfertilized eggs. Sheep would be put into cages in strategic areas, have a small wound inflicted on them, then team members would collect egg samples around the wound every couple of days. The samples were incubated and as fewer and fewer of them hatched they were able to judge the effectiveness of the campaign. I was glad to see those pests eradicated, actually.
     
  4. May 22, 2003 #3

    iansmith

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    From what I read, knowledge on the Anapheles gambiae is quite good but I don't think elimating the species will eliminate malaria. there is other vector for the parasite. The extinction migth have an impact on the enviroment because you remove a prey for predator suc as bird and fish. It is hard to determine how many eggs are eaten before it hatches and how many mosquito larvae reach sexual maturity in the wild.

    What does HEG does exacly, your explanation was not to clear.


    I also hear that they trying to create a genetically modified anapheles. the modified mosquito would have a less hostipal "enviroment" for the malaria protozoan.

    Control will defenitely be effecient, Florida and lousiana does not have malaria problem anymore.
     
  5. May 27, 2003 #4

    LURCH

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    Re: Re: Genocide and Malaria Mosquitoes

    Yes, that's one aspect of the program I find interesting. The project is not aimed at rendering the malaria parasite extinct, but only at eliminating the vector that delivers it to humans. On the one hand, this should have the minimum possible impact on the environment (malaria may serve a useful purpose in the biosphere that we don't know about). On the other hand, it leaves the virus in existence and creates the risk that it will find another way into the human body.
     
  6. May 27, 2003 #5

    iansmith

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    Re: Re: Re: Genocide and Malaria Mosquitoes

    Lurch, Plasmodium (the scientific name for malaria parasite) is not a virus. Its a unicellular protzoan and it is sometimes refer as a parasite.

    There a lot of ongoing research in labs and they sequence the whole genome of some Plasmodium species causing human disease and some of the animal model too (http://www.ncbi.nlm.nih.gov/PMGifs/Genomes/EG_T.html). The whole genome sequence for Anapheles gambia (http://www.ncbi.nlm.nih.gov/mapview/map_search.cgi?taxid=7165) is also done. Therefore it open new way for new vaccine, medication and control.

    In our department at university, there is an entomologist that did research in South Asia (Vietman but I am not sure) about malaria. They find that distrubiton of some of the malaria parasite species are different according to the species of mosquito but it migth not be the case in Africa or other part of the world. If it is the case it migth complicate things.

    There a lot of question to ask such as
    if the parasite is pressure will if adapt to new Anapheles vector?
    Is there a animal reservoir of the parasite?
     
  7. May 28, 2003 #6

    LURCH

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    Yes, I should have said "protozoan". I'm afraid I have developed the linguistic habit of referring to all in infectious diseases as viruses; quite sloppy, actually.

    BTW, the question has been asked as to exactly what HEG's do. It is my (somewhat limited) understanding that an HEG is simply a gene which carries on from one generation to the next not because they increase the organisms chances of survival, but rather because the gene itself has developed a successful survival technique. In this respect (to my way of thinking) the HEG almost resembles a separate organism, successfully surviving and reproducing not because it improves the survivability of its host, but regardless of, and sometimes even in spite of its effect on the organism. While they convey no survival benefit to the host, most HEG's also appeared to do no harm. According to the article I read, these genes are normally found in sea anemones, algae, and moss.

    However, the survival technique that HEG's have developed depends upon their ability to duplicate themselves from one chromosome to another. A geneticist named Austin Burt of Imperial College London has shown that these genes can be engineered to displace other genes in the DNA strand. If the gene being displaced were something essential to survival, the result would be a lethal genetic defect.

    The strategy is to implant a gene in a large number of males and release them into the wild population. These males would mate with females, who would give birth to healthy young that carried the HEG as a recessive gene. When two individuals carrying the recessive gene mate, the resulting offspring will be fatally flawed. The gene could express itself as the absence of a heart, a nervous system, etc.

    So, as long as there is a healthy population with which the infected individuals can mate, the HEG population increases and spreads. When the recessive trait has spread to all individuals within the population, the next generation will be stillborn.
     
    Last edited: May 28, 2003
  8. May 28, 2003 #7

    iansmith

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    Ok I get what the HEG does. It act as a selfish DNA such as small plasmid and transposon. The problems is how successfull will this technique be. Will this select for non carrier of HEG or will HEG stay in but mosquito without any harmfull "side effect" survive and propagate? The theory seems already the aplication seems weeks.
     
  9. Jun 8, 2003 #8

    LURCH

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    Testing has begun on a lab-bound population of fruitflies. Testing on actual A. Gambiea should begin next year.
     
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