Except, it could only increase virulence at the vector stage, and in order to get transmitted, a disease needs to not kill off its vector. I would actually predict there wouldn't be an increase in virulence then, because it would only serve to kill off it's own vector.
Virulence does not mean lethality. Malaria could increase its virulence by infecting more mosquitoes, becoming more likely to infect through an infected mosquito, or even by completing its incubation faster. I don't recall anything about malaria being detrimental to the life cycle of mosquitoes so any of those would have no particular impact on the vector.
Um, reducing vectors is a good thing. Vector-transmitted diseases tend to be more virulent than non-vector-transmitted ones. Eradication of the disease is pretty much not going to happen, so let's focus on decreasing virulence and transmission.
Sure, reducing vectors is wonderful. If we could kill all infected mosquitoes within 10 days of their infection then malaria would be dead right there. I don't agree that the eradication of the disease isn't going to happen, at least within human hosts. We have eradicated diseases before so there is no reason to think it cannot happen again. I am certainly not arguing against the attack of vectors, I am arguing against the attack of vectors *instead* of direct attacks on the organism. I disagree with your statement that those attacks are not helpful, in the sense of evolutionary theory, at reducing their impact on humans.
By saying "destroying every human malaria case" do you mean killing people with malaria? ... If that's not what you mean, then what exactly are you getting at?
I mean by developing medicines and treatments that can finish off a malaria case within a human before it has a chance to spread. Human infection is a stage in the life of human strains, and if they don't survive it the cycle of life does not go on. If we can consistently cure a large majority of human cases before they manage to reproduce and spread then that is strong evolutionary pressure for being unfit for the environment.
I don't recall anything about malaria being detrimental to the life cycle of mosquitoes so any of those would have no particular impact on the vector.
quote:This study makes it clear that genetics play a part, too, and that mosquitoes are not just passive squirt guns for malaria parasites.
Plasmodium parasites do hurt mosquitoes, Dr. Vernick and Dr. Wirth said. They damage salivary tissue, make the mosquitoes fly less vigorously and lay fewer eggs and, to gain a toehold in the insect, may depress its immune system.
"The mosquito doesn't want to be infected, so it has responded with this very powerful mechanism," Dr. Vernick said, referring to what he called the "resistance island" on the mosquito genome.
Anyway, I'm not interested in picking apart this example; I was using it as just that: an example of the direction I'd like to see more research go in. I'm not saying this specific approach is perfect.
We have eradicated diseases before so there is no reason to think it cannot happen again.
True, but the there are very very few diseases we have eradicated, and they are definitely not the norm. There is no reason to think we'll be able to eradicate all diseases.
quote:The vaccine success stories involve acute childhood infections. A striking feature of the natural history of these diseases is that first infections invoke immunity that is sterilizing, strain-transcending, and usually lifelong. Such acute infections either kill their host or are rapidly cleared. The pathogens persist by exploiting susceptible individuals, typically non-immune children. Why natural selection failed to find these organisms a way to penetrate previously exposed hosts is unclear, but it is evident that it did not. There must have been intense selection on all of them to break though natural immunity in the pre-vaccine era. An evolutionary solution would have been no easier in the vaccine era. Acute childhood diseases were easy targets for vaccination: natural immunity was already evolution-proof; all that was needed was for vaccines to induce something similar.
The diseases that are the focus of much of today’s vaccine development differ notably from acute childhood infections. The populations of pathogens causing diseases like flu, malaria, and pneumococcal disease frequently consist of a rich diversity of strains able to successfully infect previously infected individuals.
If we can consistently cure a large majority of human cases before they manage to reproduce and spread then that is strong evolutionary pressure for being unfit for the environment.
Or, instead of host switching, they could just evolve more resistance. There are more ways to neutralize a threat than just destroying your enemy. (BTW this is not me advocating disease rights or something, I just think it's too much effort, when there are probably easier ways)
We have many intuitions in our life and the point is that many of these intuitions are wrong. The question is, are we going to test those intuitions? -Dan Ariely