Being a Parasite Vector Isn't All Puppies and Unicorns

Maggie Koerth-Baker is a guest blogger on Boing Boing. A freelance science and health journalist, Maggie lives in Minneapolis, brain dumps on Twitter, and writes quite often for mental_floss magazine.

Short, but zippy, fact I found out this morning, while researching a piece on mosquitoes and malaria.

I've always sort of wondered what the interaction between mosquito and parasite is like. I've often seen the relationship described in a way that implies mosquitoes are ignorant of the larger human drama playing out in their digestive tract--as though they're basically just a parasite Fed-Ex. Sure, you're getting some bad news, but that's not really the mosquito's problem.

Turns out, though, there's some fairly decent evidence that, while not really being in the mortal danger we humans are, mosquitoes infected with malaria parasites aren't exactly the picture of insecty good health, either. I've spent most of the day talking to researchers at the Imperial College in London, the Johns Hopkins School of Public Health and the University of California Mosquito Research Program. They say that, while still controversial, there seem to be a least a couple of ways malaria bites the proboscis that feeds it.

First, infected female mosquitoes lay fewer eggs than their healthy sisters.

Second, it looks like infected mosquitoes might have trouble sucking blood. Gregory Lanzaro, Ph.D., director of the UC Mosquito Research Program, says there's been some research showing that malaria damages mosquito salivary glands, basically keeping the host from slurping down a full meal. Chronically un-satiated, the mosquito would end up having to bite more victims to get a proper dinner. That's good news for malaria, which needs a human habitat in order to grow up and reproduce. A mosquito that eats from more people is a mosquito that gives malaria a better chance of not ending up like a parasitic Peter Pan. Or, to look at it from our perspective, a mosquito that's carrying malaria is a mosquito that's more bitey and, thus, more likely to spread malaria to more people.

The mosquito POV? Probably a lot like being on a diet. Forever. Is it time to eat again yet?



  1. Your articles continue to be wonderful, Maggie. (Even when they’re full of parasites and hairless animals).

  2. As long as we’re hearing so much about parasites I’d love to read a bit about the fungi that inspired my moniker. Too similar to the entry on zombie crabs, perhaps?

  3. Tuckels,

    As I hit “Save” it occurred to me that maybe I’m making myself out to be a little creepy.

    Tomorrow: Fluffy kittens & feel-good facts.

  4. I hope now people will stop hating mosquitoes and focus on the disease. Our poor flying buddies are not evil, they’re just trying to deal with malaria the best way they can.

  5. I seem to recall that the parasite Toxoplasmosis causes a type of brain damage in its mouse host. The damage makes the mouse fatally attracted to cat urine. This has apparently come about because Toxoplasma only reproduces in the gut of cats.

    So again, for the poor mouse parasite vector, it isn’t all puppies and unicorns.

  6. Hi. I work at Imperial on Malaria you must have been talking to my colleagues. You’re right to say that malaria parasite infection puts the mosquito at a disadvantage. The flip-side of my colleagues’ research is that this shows that producing half-baked antimalarials (or not taking the correct dose), whilst reducing the infection in the mosquito actually makes it fitter, happier, live longer and so infect more people.

  7. @ Nyrath #5:

    I don’t know if there has been much legit study on the subject, but some have postulated that many of the so-called “cat ladies” (who compulsively collect as many of the animals as possible) are also victims of Toxoplasmosis. It would go a long way toward explaining how anyone could live among the stench created by hundreds of poorly-kept felines.

  8. This is why I’ve always felt that anti-malarial research should concentrate on curing the mosquitoes instead of the people. After all, if you cure one species you cure the other and you can try all sorts of radical procedures without having to muck about with informed consent forms for the test subjects. You get more generations in a shorter amount of time to see how things turn out in the long term too.

  9. So if we could make mosquitoes that were immune or strongly resistant to malaria shouldn’t they outcompete the malaria bearing mosquitoes?

  10. The flies which transmit sleeping sickness are similarly choked by the protozoan parasite that causes it. They have to eat more frequently and have longer meals, so they become better vectors.


    Keep an eye on National Geographic News, then. I’ve got an article that should be up there tomorrow (I believe) that will interest you.

  12. For those who haven’t, I recommend reading Zimmer’s “Parasite Rex”; google books or Amazon. I enjoyed it while hiking in Borneo, even if it did make me a bit paranoid/squeamish…

  13. @#10, my thoughts exactly. If carrying the parasite is a disadvantage, it’s possible that engineering mosquitoes (which are usually at a disadvantage to start with due to long-term lab breeding) could actually work.

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