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| Malaria parasite in mosquito midgut |
We often think of mosquitoes as willing co-conspirators in spreading human1 pathogens. But of course, in most cases the mosquito would be just as happy to get rid of the pathogen themselves; even if it doesn’t cause as severe as disease in the mosquito as in humans, it’s not doing them any good.2
So why don’t the mosquitos get rid of these pathogens, rather than carrying them around to infect yet more vertebrates? We know that insects have a fairly elaborate immune system, albeit one that’s quite different from ours.
The answer seems to be (at least partially) that — just as with pathogens of vertebrates — the mosquito pathogens have evolved ways of evading the immune response, so that the mosquitos can’t eliminate them.
Our findings provide support for the hypothesis that mosquito-borne pathogens have evolved to evade innate immune responses in three vector mosquito species of major medical importance.
—Bartholomay, L., Waterhouse, R., Mayhew, G., Campbell, C., Michel, K., Zou, Z., Ramirez, J., Das, S., Alvarez, K., Arensburger, P., Bryant, B., Chapman, S., Dong, Y., Erickson, S., Karunaratne, S., Kokoza, V., Kodira, C., Pignatelli, P., Shin, S., Vanlandingham, D., Atkinson, P., Birren, B., Christophides, G., Clem, R., Hemingway, J., Higgs, S., Megy, K., Ranson, H., Zdobnov, E., Raikhel, A., Christensen, B., Dimopoulos, G., & Muskavitch, M. (2010). Pathogenomics of Culex quinquefasciatus and Meta-Analysis of Infection Responses to Diverse Pathogens Science, 330 (6000), 88-90 DOI: 10.1126/science.1193162
- And other animal[↩]
- Are there any agents that are pathogenic to vertebrates, and mutualistic in their arthropod host? Not that I know of – there are lots of amazing mutualistic agents of arthropods [example here in spiders: “More Symbionts and Flight“], but as far as I know they tend to be highly specialized to one host.[↩]
[…] often think of mosquitoes as willing co-conspirators in spreading human1 pathogens. But of course, in most cases the mosquito would be just as happy to get rid of the […]
The attack on the pathogen in the nonhuman hosts as a preventive measure was explored to much lesser extent than the attack on nonhuman host itself, I suppose – tt’s so much easier to kill than to heal. But that may be interesting approach. Vaccinating all the mosquito larvae against dengue might be tough, but at least the mosquitoes don’t have Jenny McCarthy to warn them against the imagined evils of vaccination.
I’m only half joking here.
There was a discussion that touched on this in Dr Kiki’s Science Hour awhile back:
http://twit.tv/kiki36
Among other things, her guest discussed a strategy for slowing or stopping the spread of malaria by killing the mosquitoes fairly late in their lives. This has a big impact on the spread of malaria, because they have to feed on an infected person to pick up the parasite, and then feed on someone else to spread it. (I gather they feed only when it’s time to lay eggs, so it’s not every day or anything close.) But killing them relatively late in their life cycle doesn’t have much of a fitness cost to them, since most mosquitoes don’t live long enough to be affected. The idea is that this lets you control the spread of malaria, without causing the mosquitoes to evolve resistance.
The mosquito is designed to host, retain and spread. They have the ability to adapt quickly to most non-chemical threats.
I guess when you think about it, mosquitoes are forced to eat contaminated food all the time. You would think with their short life span they would just want a decent meal before they die lol
If mosquito vectors evolve resistance to insecticides to me this makes sense that the pathogens are evolving too. I do appreciate the question posed in the title of this post, as it’s easy to forget that the carriers of human pathogens are trying to fight them off as well.
So is the lifespan of an mosquito infected with a pathogens shortend? Or does its immune system keep it at bay?
I like science and believe it is good to study to learn what actually is going on. But isn’t this fairly obvious? Doesn’t pretty much everything that invades other lifeforms develop ways to resist that lifeforms systems to attack invaders?
“We often think of mosquitoes as willing co-conspirators”
That is a really great point!! Most people figure because they need blood to survive and thrive they themselves are a parasite. They like all living creatures are just trying to live.
Hi iayork, thanks for the post we know mosquitoes are forced to eat contaminated food and we know that they spread malaria just have to protect ourselves as best we can.