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What do malaria, sleeping sickness, yellow fever, and dengue virus have in common? Sure, they’re all tropical diseases, but there’s something else.

All of these diseases have some kind of insect vector.


image from the Public Health Library

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At one time, I thought it was merely a matter of an insect biting one organism and then transmitting the parasite to another organism because the parasite was stuck on the insect proboscis, or something like that, kind of like the way cold viruses might get transmitted by someone borrowing a used handkerchief, or perhaps getting Salmonella because you ate the wrong crop of organic spinach.

And then, I spent a couple of years as a post-doc studying trypanosomes and trying to grow them in the laboratory. And I found that keeping tryps alive in culture, outside of a living body, is really not that easy. And the insect plays a much bigger role than I used to think.

I also used to think that we could attack the mosquitoes and flies that carry disease in a different way. I thought, that if we could use BT toxin (which is not toxic to humans, but is toxic to insects) and somehow, get the toxic crystals into a place where the mosquito and fly larvae would consume it, that this could help solve the problem.

Now, I know that for anything like BT toxin or any other kind of insecticide or drug, evolution is powerful enough that some kind of drug resistance is likely to emerge, at least eventually. It’s only a matter of time.

So, what do we do? How do we protect people from tropical disease?

Sure, we’ve got mosquito netting. Sure, we’ve got fly traps.

But the evidence is pretty clear that those really aren’t quite enough. And sure, we have children dying from malaria and other forms of insect-carried disease.

So what do we do?

In some of the next posts, I will write about methods for confronting those pesky pests and possible options for turning the tables on insect-borne disease.


  1. #1 llewelly
    August 3, 2007

    Given how effective DDT was before resistance evolved, if the agricultural community had not spewed millions of tons of DDT on fields, with poor or no targeting of specific insect species, it is possible that DDT could have been used to exterminate some of the carriers – particularly for malaria, and particularly if pyrethoids had become available before widespread DDT resistance became normal. Unfortunately it’s too late for that now.

  2. #2 Tom @Thoughtsic.com
    August 3, 2007

    Any comment on the efficacy of the introduction of extremely large amounts of dragonflies?

  3. #3 Sandra Porter
    August 3, 2007

    I think that might be harder than it seems, plus I suppose there’s a risk of introducing a new invasive species.

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