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Viruses That Show Resistance To Drugs?  
User currently offlinefca767 From United Kingdom, joined Nov 2006, 1751 posts, RR: 1
Posted (4 years 1 month 3 weeks 2 days 16 hours ago) and read 1499 times:

I was just wandering about Malaria, How can they overcome a drug.

If a Mosquito dies, then 1st from the new drug, how does it eventually become resistant if it is already dead.

If it's like 1 out of 100 mosquito's has always been resistant then it's not becoming resistant but always been resistant.

Edit: Found it http://www.aegis.com/factshts/network/simple/resistance.html

[Edited 2010-07-06 05:53:42]

8 replies: All unread, jump to last
 
User currently offlineariis From Poland, joined Sep 2004, 421 posts, RR: 1
Reply 1, posted (4 years 1 month 3 weeks 2 days 14 hours ago) and read 1462 times:

I am no expert in immunity but I would guess that when exposed to new threat, any living population (mosquitoes too) would first decrease rapidly leaving only those that were strong enough to resist which will then eventually introduce a new generation born from those naturally selected to "fight back".

So in a way I think I agree with you - if a large-scale population as a whole becomes resistant I would guess it means that there were individuals in that population that were luckily resistant from the very beginning which eventually spread its features among children after weaker ones went extinct. The only thing which is critical and very delicate here is whether there will be enough strong individuals left to rebuild the population.

As for the viruses which are not strictly following the definition of a life form it may be difficult to judge when they are dead as they are not fully alive anyway. And this fact only adds some spice to the discussion I guess.  



FAO - Flight Activities Officer
User currently offlineeinsteinboricua From Puerto Rico, joined Apr 2010, 3057 posts, RR: 8
Reply 2, posted (4 years 1 month 3 weeks 2 days 14 hours ago) and read 1458 times:

I don't understand your question. A mosquito is just a carrier of the virus. The mosquito itself does not suffer the disease. Resistance, in this case, is caused inside humans and the fact that viruses evolve and combine with other strains to become even more deadly. That was why the bird flu pandemic was very worrisome. Had it combined with regular human flu, it would have been even more deadly than the swine flu pandemic was, making it easier to infect a human host. Since there was no vaccine ready for a human case of bird flu, death tolls could have been higher.


"You haven't seen a tree until you've seen its shadow from the sky."
User currently offlineAesma From France, joined Nov 2009, 6601 posts, RR: 9
Reply 3, posted (4 years 1 month 3 weeks 2 days 14 hours ago) and read 1435 times:

That's not how evolution works anyway, according to Darwin. No "new feature" appears for a reason, it's all random but can come handy, when of course it doesn't kill you.

You are thinking about Lamarckism, a nice but defunct theory.



New Technology is the name we give to stuff that doesn't work yet. Douglas Adams
User currently offlineus330 From United States of America, joined Aug 2000, 3871 posts, RR: 14
Reply 4, posted (4 years 1 month 3 weeks 2 days 13 hours ago) and read 1425 times:

Quoting Aesma (Reply 3):
You are thinking about Lamarckism, a nice but defunct theory

Perhaps I am mistaken, but I remember reading an article in National Geographic not too long ago (within the past three years--sorry for being vague) talking about how some scientists are beginning to reevaluate Lamarckism--that, apparently, in certain cases, Lamarckism offers a better and more plausible explanation than Darwinism. From what I can recall (again, sorry for being vague), the gist of the article was that Darwinism and Lamarckism are neither entirely correct, and that the gaps in one are filled by the other.


User currently offlinefca767 From United Kingdom, joined Nov 2006, 1751 posts, RR: 1
Reply 5, posted (4 years 1 month 3 weeks 2 days 12 hours ago) and read 1399 times:

Quoting ariis (Reply 1):
As for the viruses which are not strictly following the definition of a life form it may be difficult to judge when they are dead as they are not fully alive anyway. And this fact only adds some spice to the discussion I guess

That's true   I found something that explains it in my first post now  


User currently offlineDocLightning From United States of America, joined Nov 2005, 19552 posts, RR: 58
Reply 6, posted (4 years 1 month 3 weeks 2 days 9 hours ago) and read 1369 times:

First of all, the Plasmodium falciparum parasite that causes malaria is neither a virus nor a bacterium. It is a protozoan, which means that it has membranous organelles inside, such as a nucleus and mitochondria.

For this sort of evolution, it is important to remember that P. falciparum only spends a small portion of its life cycle in the human body. It spends a good portion of it in a mosquito's gut.

During the reproduction of the parasite, mutations occur randomly. Most (>99.9%) of these will cause no effect or will be harmful to the parasite. A small number of these mutations may, however, confer some resistance to the anti-malarial drugs. If a patient with malaria does not take a complete course of the drugs, then the parasites that survive will be those who were more resistant to the drugs. Those will survive to be transmitted by another mosquito. It's important to understand that the drugs don't make the bugs evolve resistance, per se. But that without the drugs, there is no selective advantage to the bugs that are resistant (and resistance usually has some disadvantages associated with it, too). Since the drugs offer a selective advantage to mutants that have full or partial resistance, the population of parasites will become enriched in those resistant mutants and the susceptible mutants will be killed.

Let's take an example of someone with a bacterial infection, since it's easier to describe:

They start with an infection caused by ten trillion bacteria, all of the same type and reproducing. With each round of bacterial reproduction (about 20 minutes) mutations occur. Some of these mutants will be slightly resistant to the antibiotic that we prescribed, just by sheer chance. Remember, it only has to happen once in 10 trillion. That resistant mutant will survive longer while the patient is taking the medication than its susceptible brethren.

If the patient finishes the entire course of antibiotics, the partially resistant mutant will still be killed, but if the patient stops early, the partially resistant mutant is more likely than the susceptible bugs to be alive. And now that partially resistant mutant can be spread on to another patient who will also not finish their antibiotics. After a few rounds of non-compliant patients, that partially resistant mutant will have mutated into a fully resistant mutant, or MRSA, which is exactly how MRSA appeared in the first place.

It's a lot easier to describe with pictures.


User currently offlineus330 From United States of America, joined Aug 2000, 3871 posts, RR: 14
Reply 7, posted (4 years 1 month 3 weeks 2 days 8 hours ago) and read 1347 times:

Quoting DocLightning (Reply 6):
After a few rounds of non-compliant patients, that partially resistant mutant will have mutated into a fully resistant mutant

Isn't that why drug resistant TB is on the rise? People (mainly homeless people who are afflicted with it) aren't taking their full course of prescribed medication?


User currently offlineDocLightning From United States of America, joined Nov 2005, 19552 posts, RR: 58
Reply 8, posted (4 years 1 month 3 weeks 2 days 6 hours ago) and read 1327 times:

Quoting us330 (Reply 7):

Isn't that why drug resistant TB is on the rise? People (mainly homeless people who are afflicted with it) aren't taking their full course of prescribed medication?

Yes. Unfortunately, because of the very slow growth and life cycle of dormant TB, it takes a 6-12 mo course of antibiotics to fully treat it. Since there are a high number of people who don't complete their course of medication, MDR (multi-drug resistant) TB is on the rise.

For those who do not believe in evolution, this is it. Either God is interfering in the development of these microbes, which is a seriously messed-up theology, or there be some evolution happening. The thing about bacteria is that they are far more "Evolved" than we humans are. They divide every 20 minutes. They can have 72 generations in 24 hours! That's a lot of mutation that can happen and in very large population numbers.

It's for this reason that I believe that antibiotics should be classified as controlled substances, like morphine.


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