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Here’s What Happens When A Tick Bites You

Castor bean tick, or sheep tick. Credit; Richard Bartz
Castor bean tick, or sheep tick. Credit: Richard Bartz

When a tick bites, it does more than just stick you with the pointy end. Here’s what happens, in far more detail than you ever cared to know. You can thank Dania Richter from the Charité University Hospital in Berlin, who carefully analysed the mouths of ticks, and filmed them as they fed on the ears of recently euthanized mice.

The mouthparts of the castor bean tick (Ixodes ricinus) consist of three main sections. The centrepiece is a long, sword-like structure called the hypostome. It has rows of backwards-curving spines along its edges, as well as its entire bottom face. It also has a groove running down its centre, which channels the tick’s saliva into its host, and channels the host’s blood into the tick.

On top of the hypostome is a pair of chelicerae—long rods that end in hooked teeth. The chelicerae are telescopic, so they can extend to just beyond the hypostome’s tip, or pull back to around half its length. They’re also mobile—their toothed tips can swing out to a 45 degree angle.

Here's what the chelicerae look like when fully extended. Scale bar = 30 micrometres
Here’s what the chelicerae look like when fully extended. Scale bar = 30 micrometres

When a tick wants to bite, it starts by gently coursing its chelicerae over the skin of its host (at about 0:25 in the video). Each one ends in a tooth that’s tapered to an especially sharp point, which scrapes and punctures the skin with very little force. This also releases smells and other chemical information that the tick can weigh up.

Now, it’s time to break in (1:35 in the video). The chelicerae start to flex their tips. At first, they take turns; eventually they move together. With each sweep, the teeth snag on the host’s flesh and bury the chelicerae even deeper into the skin. After 30 of these movements, the entire tips are firmly embedded.

The tick then contracts both of its chelicerae while flexing both tips, like it’s doing a nightmarish version of a breaststoke (2:20 in the video). The motion drives the rigid, sword-like hypostome into the skin, and the backwards-facing spines keep locked in place. The chelicerae relax and extend, before flexing and retracting again. Each stroke ratchets the hypostome deeper and deeper. After six of them, it’s completely buried and the tick starts to feed.

This is a very different sequence of events to what happens when a mosquito bites you (and you can watch a video of that too). That’s because ticks, unlike many other blood-suckers, are adapted for the long haul. A mosquito bites, sucks and quickly leaves. A tick bites… and stays there for days. It needs to attach itself very firmly so that it can’t be easily dislodged. It does so with the curved teeth and spines on its mouthparts, and by burying them very deeply.

The same sticking power is also vital for the parasites that ride inside ticks, like the spirochete bacteria that cause Lyme disease. They only spring into action when the tick starts feeding, and they need to time make their way from the creature’s guts into its bloodstream, into its salivary glands, and finally into its host. The whole process can take a couple of days. If the tick wasn’t so good at anchoring its face into a host, Lyme disease wouldn’t exist.

Reference: Richter, Matuschka, Spielman & Mahadevan. 2013. How ticks get under your skin: insertion mechanics of the feeding apparatus of Ixodes ricinus ticks. Proc Roy Soc B http://dx.doi.org/10.1098/rspb.2013.1758

18 thoughts on “Here’s What Happens When A Tick Bites You

  1. “Here’s what happens, in far more detail than you ever cared to know. ”

    That is pretty much what I thought when I read the title. In fact, having been fed on by a tick or few I almost didn’t read it because I really didn’t want to know. Curiosity won out though. Next time I find embedded in my skin I’ll take a bit of time to marvel at how it broke into my skin before I terminate it with extreme prejudice (incidentally, also reread the Lyme disease chapter in Spillover this past weekend).

  2. out of all the organisms on the planet I hate nothing more than… THE TICK!!
    but ahh well, as human being we should be able to avoid them easily.

  3. Willy Burgdorfer found that although the mechanisms of transmission to host were still under investigation Lyme disease could be transmitted by saliva of tick, which is the first thing injected into the host and by regurgitated of stomach contents or possibly by means of infected fecal material.
    Far too many assumptions are made about times to transmit Borrelia to humans.
    Not enough attention is taken of the burden of disease ticks can transmit, in Italy one tick was found to have 108 genera of bacteria – several of which are known to cause human health problems and that is before we consider virus, protozoa and other pathogens or their interaction within the human host.
    Whilst understanding this unique process helps to move science along there is so much yet still unknown about Borrelia in relation to human health so many statements made to patients based on uncertain science. The James Lind Alliance reviewed the research with Public Health England overseeing the process and identified top ten research priorities http://www.lymediseaseaction.org.uk/wp-content/uploads/2013/01/JLA-top-10.pdf

  4. Having been bitten 4 times. I feel that researchers have no idea how long it takes to get infected. I felt a bit on my thigh immediately looked at it . Red bulls eye rash and a tick sticking out. Which I promptly removed and sent to have it tested, my point is I believe you get infected immediately no 7 hours waiting period for the tick to infect you. It’s done from the first bit…

  5. I am still curious as to what happens to the tick after it feeds? Does if fall out on it’s own if not removed? Can it bite you again?

  6. I was petting my dog and he had a tick on his scruff. It wasn’t in but it was still difficult to get off. However my dog hasn’t been outside for a while at that point… I was wondering if anybody knew how long it takes for a tick to finally bury itself to start feeding. This website really helped though and gave me lots of new information! I love it!

  7. I am still curious as to what happens to the tick after it feeds? Does if fall out on it’s own if not removed? Can it bite you again?

  8. I was wondering if anybody knew how long it takes for a tick to finally bury itself to start feeding. This website really helped though and gave me lots of new information! I love it!

  9. In response to Joanne Drayson;

    While the Spirochete is transmitted into the host via the tick’s saliva, it is unable to live in it’s saliva long term. So what happens, and the reason they gave the time frame they did, is that it has to travel the route described in the article into the saliva in order to be tramitted. When the tick latches on to its host and releases its pheromones, signaling it’s about to begin feeding, Spitochete picks up this chemical message and begins its journey.
    Having said that, I do agree with you that there is a wide discrepancy in the time it takes for a tick to pass Spirochete on to its host. Perhaps this is because there isn’t one specific time that can be given because it relies on too many factors for there to be a reliable time frame, let alone one general time.

  10. No a tick will not fall off on its own you have to manually pull it off the tick continues to suck your blood and it gets bigger and when you remove it it will crawl twords you again and try to bite you because it might not be done drinking your blood

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