A Blog by Ed Yong

Here’s What Happens Inside You When a Mosquito Bites

The video above shows a brown needle that looks like it’s trying to bury itself among some ice-cubes. It is, in fact, the snout of a mosquito, searching for blood vessels in the flesh of a mouse.

This footage was captured by Valerie Choumet and colleagues from the Pasteur Institute in Paris, who watched through a microscope as malarial mosquitoes bit a flap of skin on an anaesthetised mouse. The resulting videos provide an unprecedented look at exactly what happens when a mosquito bites a host and drinks its blood.

For a start, look how flexible the mouthparts are! The tip can almost bend at right angles, and probes between the mouse’s cells in a truly sinister way. This allows the mosquito to search a large area without having to withdraw its mouthparts and start over.

“I was genuinely amazed to see the footage,” says James Logan from the London School of Hygiene and Tropical Medicine, who studies mosquitoes. “I had read that the mouthparts were mobile within the skin, but actually seeing it in real time was superb. What you assume to be a rigid structure, because it has to get into the skin like a needle, is actually flexible and fully controllable. The wonders of the insect body never cease to amaze me!”

From afar, a mosquito’s snout might look like a single tube, but it’s actually a complicated set of tools, encased in a sheath called the labium. You can’t see the labrum at all in the videos; it buckles when the insect bites, allowing the six mouthparts within to slide into the mouse’s skin.

Four of these—a pair of mandibles and a pair of maxillae—are thin filaments that help to pierce the skin. You can see them flaring out to the side in the video. The maxillae end in toothed blades, which grip flesh as they plunge into the host. The mosquito can then push against these to drive the other mouthparts deeper.

The large central needle in the video is actually two parallel tubes—the hypopharynx, which sends saliva down, and the labrum, which pumps blood back up. When a mosquito finds a host, these mouthparts probe around for a blood vessel. They often take several attempts, and a couple of minutes, to find one. And unexpectedly, around half of the ones that Choumet tested failed to do so. While they could all bite, it seemed that many suck at sucking.

The video below shows what happens when a mosquito finally finds and pierces a blood vessel. On average, they drink for around 4 minutes and at higher magnifications, Choumet could actually see red blood cells rushing up their mouthparts. They suck so hard that the blood vessels start to collapse. Some of them rupture, spilling blood into the surrounding spaces. When that happens, the mosquito sometimes goes in for seconds, drinking directly from the blood pool that it had created.

When the mosquitoes were infected with the Plasmodium parasites that cause malaria, they spent more time probing around for blood vessels. It’s not clear why—the parasites could be controlling the insect’s nervous system or changing the activity of genes in its mouthparts. Either way, the infected mosquitoes give up much less readily in their search for blood, which presumably increases the odds that the parasites will enter a new host.

Many hours after a bite, Choumet’s team found Plasmodium in the rodents’ skin, huddled in areas that were also rife with the mosquito’s saliva. The mosquito starts salivating as soon as it probes the mouse’s skin, releasing substances that prevent blood vessels from constricting, stop blood from clotting, and prevent inflammation. Sometimes, Choumet could see the saliva as small bubbles that hung around the tips of the mouthparts. And even after the mosquito stops feeding, pockets of saliva linger in the lower layers of the skin. Plasmodium parasites seem to stay in the same place—perhaps they work together with the salivary chemicals to suppress the mouse’s immune system.

The team also tested “immunised” mice, which were loaded with antibodies that recognise a mosquito’s saliva. “Some people, especially in Africa and Asia, are bitten several times every day, so we wanted to know if mosquitoes behaved differently when they bit animals that were immunised against their saliva,” says Choumet.

She found that the antibodies reacted with the insect’s saliva during a bite, forming noticeable white clumps at the tips of the probing mouthparts. This clogged up smaller blood vessels, which stopped the mosquitoes from drinking from them. But the insects got around this problem by probing around for longer, and by hitting the largest blood vessels.

Beyond the stunning videos, these discoveries are unlikely to lead to new ways of preventing or treating malaria by themselves. However, they do tell us a lot more about the event that kicks off every single malaria case—a mosquito bite. It’s a resource that other researchers will undoubtedly use. “I have submitted  a grant application to investigate  aspects of the interactions between mosquitoes, hosts and parasites,” says Logan. “The techniques and discoveries from this paper are very exciting to me, and will be of value to future activities of my own research group.”

Hat-tip to James Logan for alerting me to the story via Twitter, and inspiring the headline!

Reference: Choumet, Attout, Chartier, Khun, Sautereau, Robbe-Vincent, Brey, Huerre & Bain. 2012. Visualizing Non Infectious and Infectious Anopheles gambiae Blood Feedings in Naive and Saliva-Immunized Mice. PLoS ONE http://dx.doi.org/10.1371/journal.pone.0050464

49 thoughts on “Here’s What Happens Inside You When a Mosquito Bites

  1. Freaking fascinating, but so gross at the same time. A giant, twisty, sucky mouth is all I will think about when I see a mosquito on me now. Ew.

  2. As someone seriously inconvenienced by those little whizzing monster bitches, I have to say: Pretty impressive.

    Evolution. It works.

  3. This is just how oil companies drill for oil now. Interesting how blood-sucking insects came up with the idea many millions of years earlier.

  4. I wonder how it actually searches for the blood vessel. Is it heat-seeking? Does it depend on neurons in the mouthpart? Or is some neuron-free innate function of mouthpart proteins?

  5. Absolutely fascinating and revolting at the same time! Makes you wonder what nature was thinking when she invented these parasites, but she definitely was creative. Thanks for sharing!

  6. Wow!!! That pretty much sums it up. However I am no expert by any means, but to me it seems this would help treat malaria. I mean they know now that mosquito with the parasites behave differently. Maybe there is some way to breed this reaction out and release these into the breeding populations. Or perhaps there is some chemical that can be used to spray breeding locations to counteract this problem. Also knowing now how they saliva and parasite work together perhaps some one with a much better brain than mine can develop a medicine that acts on this I know vaccines already exist but they hold no value when already infected but maybe knowing this a treatment can be developed that make the active germs pool into areas they think is mosquito saliva and be destroyed. I guess though effective malaria treatments exist and all I just said is moot as the treatment problem in remote places is the availability of medicine not the treatment. So even though I have no idea what I am talking about that was still really cool videos. Up there on my list with those videos of cats drinking, not all that useful but very cool non the less.

  7. @DuVilkai. From what I saw and read it seems they search haphazardly until they strike blood. It says they search upward of 5 minutes especially if they are infected. So as a poster above asked if they are heat seeking I would venture a guess as to say know, out side of knowing the taste of blood they just poke around until they find what they seek.

  8. I usually kill mosquitos while they are in the process of sucking my blood. Does their mouthparts remain in my body? If yes, do they harm me?

  9. More research needs to be done into whether mosquitos also carry Lyme disease and other infections like babesia, bartonella, ehrichlia etc. Also how tick bites work at this level of detail and therefore how quickly they can transmit infections like lyme disease. At present it is thought that it requires at least 24-36 hours to transmit diseases, but that’s only if the infection resides in the stomach of the tick, not if it’s in the saliva. As this research shows, the saliva is a hugely important mechanism in the way infections are transmitted from vector to host.

  10. Mosquito is the last stuff I want to be with in the world. I belong to the kind of people who attract mosquitoes most even if there are many other people that wear much less in the same room. In terms of our convenience, I hope mosquitoes will not be fed on blood any more.

  11. @Shashwat Singh: No, I don’t think they hurt you. They probably just stay there…maybe decompose…I have no idea. But I don’t think it hurts you — your muscles would probably just around it.

    But seriously, YUCK. I’m so glad I didn’t eat lunch before watching those videos. >.<

  12. Fascinating and disgusting at the same time.
    I hate mosquitos! I cannot sleep at night until i know i killed every mosquito in the room.
    By the way, does anyone know why they are attracted more by some persons more than other? If i am together with 5 more people, all mosquitos come for my blood, the others don’t have to worry about them.

    1. I hate to be the “bad guy” but after reading several comments (without pointing out posters) I have to wonder how many people actually read the article and did not just either A. watch only 1 or more of the videos or 2. just skimmed through the piece and buzz over the comments.

      On a totally unrelated note. To the posters that asked what happened to the suckers when you killed a mosquito while it fed. I would, without knowing for certian, venture a guess to the answer here. If the suckers did stay in it would almost certainly be rejected from your body at some point as is most other foreign objects. Much in the same way a body might reject a donated organ. In my own personal experience I had stitches when I was about 8 years old, when I came to the doctor 2 of them had grown into the skin, because I healed faster than average in that location. The doctor simply cut them and left them in. I could see them however and in about 2 weeks time I looked at my arm and noticed they were no longer there. This is a personal example of the idea I was conveying above. I feel certian the same would happen with the suckers and other instruments said mosquito may or may not leave behind.

  13. Yes totally agree, gross but fascinating!
    Surely it’s the body’s response, releasing mast cells (hystamines) that causes the inflamation and itching?

  14. En mi humilde opinión, y después de ver el excelente descubrimiento de como actúa en mosquito al picar, con todos sus desencadenantes; debe de ser cuestión de tiempo, el que se encuentre el tan deseado medicamento para curar la malaria, o antídoto en su defecto.

  15. Wow! Very interesting, I live in North Dakota and mosquitos rein supreme. The Air Force sprays every before the state fair but with all the standing water and consistent rain this spring/summer there’s no getting rid of them. I was just doing some yard work and couldn’t take it anymore. I thought they just stung you got in and got out. So when we smash them we leave mosquito saliva and their stinger inside us. I feel so much better knowing this. Honestly though awesome research.

  16. There is nothing in those videos or article to suggest that killing a mosquito while it’s biting you will result in the mouthparts remaining under your skin. More likely when you brush it off or it falls off, they’re still attached to the mosquito.

  17. A good mosquito deterrent that they cannot grow immune to is bats. Properly placing a bat house could help tremendously. Little brown bats can catch up to 1k/hr.

  18. Take hold of the little sucker with your thumb and index finger and pull him and his sucker out of your skin, before you crush her.

  19. Amazing! Makes the “awe” live up to the word “awesome”, but there is more than “some” awe in this.

    Awful, being a terrible pun, seems pivotal. With Anopheles’ capacity to second-hand kill (Plasmodium, of course, being the real killer- if unable to do so without help), they are both terrible and enlightening, to us (mere hosts).

  20. just been bitten 15 times in few days in Venice..some of the bites are huge and slightly worrying..and my poor face is swollen..not amused at all.

  21. I am a walking Mosquito magnet. I have tried numerous things to keep them away and they still swarm me. We have had several cases of West Nile Virus in my area in the past few years resulting in numerous deaths, so this is a huge concern for me. And due to our out of the norm rainfall this year the mosquitoes numbers are off the charts this year. Thanks for continuing to do research on ways to keep them away. We are doing all we can around our home to keep them at bay but still, they are vigilant this year.

  22. that is very interesting…but I am still trying to find out when I let a mosquito suck my blood then fly away why doesn’t it leave a bump…I have had only one mosquito bite in my entire life and I am 48 and cant find the answer to my question…sometimes I will even swat them away and still no bump or itching…cant understand that…and I figured out that I have grown immune to poison ivy and oak…have only had poison ivy once when I was a child…and not since then, even tho I have walked thru ivy or oak many times…but the mosquito thing has me stumped, have tried for a long time to try and get bumps but nothing..when I was a teenager a friend of mine and I were out one night and we had the mosquitoes going nuts around us, I was plenty bit and so was she and she had bumps all over her while I had not a one…can anyone explain that to me…

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