Over at Doc Around the Clock, Dr. IBear has a nice post on Lyme disease: what it is, what it's not, and how to deal with ticks (appropriately, not as his mom removed them). He mentions this:

Most of the time people who get Lyme disease don't even know or remember being bitten by a tick. Thus, it stands to reason that if you do remember being bitten by a tick you probably don't have Lyme disease.

I want to elaborate on this just a bit, below.

A reason many people don't realize they've been bitten is because when the tick bites the human to transmit the Borrelia spirochete, it's not always a full-grown tick that does the biting.

Ticks undergo a complex life cycle with a series of molts (egg --> six-legged larvae --> 8-legged nymph --> 8-legged adult tick). WIth the obvious exception of the egg stage, at each other part of the life cycle, the tick needs a blood meal. Typically in the early stages, that meal will come from smaller animals, such as mice or other rodents. This is where the tick picks up Borrelia burgdorferi: from species such as the white-footed mouse Peromyscus leucopus and others that act as the reservoir of the bacteria. Once the tick is infected, it remains so for life, spreading the bacterium when it bites--and so, subsequent hosts may also become infected. The human is one of these. Typically, we're an "accidental" host--in many areas where Lyme disease is endemic, ticks prefer to feed on deer (and hence, the importance of this animal in maintaining the tick population in the region). Now, even adult ticks are pretty small. Nymphs are smaller, and larvae are very hard to see, even when you're looking. So it's not just because ticks are small that you don't notice their bite; it's because the immature ticks are even smaller and less conspicuous. The images to the left are shown actual size; you can see that, while you may not notice an adult tick, even careful checking might miss a larvae or nymph.

Imagesfrom and


More like this

Student guest post by Kyle Malter In many areas of the country there is a vile blood sucker that lurks in our forests, our parks and even our backyards.  What concerns us is not what this creature takes but rather what it leaves in our body after it bites us:  corkscrew shaped bacteria called…
This is the last of 16 student posts, guest-authored by Jessica Waters.  Climatologists have been warning us about the ongoing and impending consequences of global warming for years. But the results of climate change affect more than just polar bears and penguins  - if you live anywhere in the…
Re-post from May 17, 2006, under the fold... When teaching biology, one has to cut up the syllabus into edible and digestible chunks, and it makes sense to cover various subdisciplines in separate lectures. As you know, I strive to find ways to make connections to students so they don't leave…
I had a strange worry as a kid. I was very scared of getting bit by a tick and developing Rocky Mountain Spotted Fever (RMSF). I know, weird--even for nerdy kids like me, who knows about Rocky Mountain Spotted Fever? How many readers are even familiar with it? For those who aren't, RMSF is a…

I got Lyme disease when I first came to the USA. I had a tick, I removed it, got a target-shaped rash, went to the ER, got antibiotics (tested positive in the meantime) and am still alive and well 15 years later. Luckily, my wife (at the time still wife-to-be) knew all about it and made me go to the doctor - I had never heard of Lyme disease back in Europe.

Ticks. What could the Intelligent Designer have had in mind when it made them? We are overrun with them this year. Fortunately, at least so far, Lyme and Rocky Mt are not common here.

By Mark Paris (not verified) on 09 Jun 2006 #permalink

A great point to make, re: the easily unnoticed nymphal-stage ticks, which transmit the vast majority of Lyme disease in humans. Also of note is the fact that while adult ticks prefer deer, nymphs prefer small rodents like mice and chipmunks. Researchers have recently found that the key to Lyme disease risk is the rodent population, not the deer population as was previously thought.

"Most of the time people who get Lyme disease don't even know or remember being bitten by a tick."

True. Only 20% are aware according to a study cited in the Wikipedia-Lyme disease article. Another reason for this, in addition to the small size of the tick in its nymphal stage, is that the tick secretes chemicals that act as an anesthetic, so you don't feel the bite at all.

But back to Dr. Ibear's quote:
"Thus, it stands to reason that if you do remember being bitten by a tick you probably don't have Lyme disease.
Huh? Awareness of tick bite is independent of whether or not the tick carries Lyme. The only way noticing the bite reduces your risk of contracting Lyme disease would be if you pulled the tick off before it has a chance to transmit the infection (the time is disputed, but the risk is certainly greater at 24 hrs and beyond; if the tick is engorged, concern is most definitely warranted).