Fri May 25, 2012
Tick Talk: Lyme Disease Under The Microscope
JOHN DANKOSKY, HOST:
This is SCIENCE FRIDAY. I'm John Dankosky, in for Ira Flatow. You've probably already encountered them this year, buried deep in your pet's fur, maybe on your own skin - yes, ticks. These bloodsuckers are often no bigger than a poppy seed, but they can wreak havoc with your health and your pet's.
Infected ticks are the main culprits in the transmission of Lyme disease. It's being blamed for causing a senior banker at JPMorgan to miss a lot of work, leading to a more than $2 billion blunder. Lyme disease can be debilitating. The symptoms can range from fever and fatigue to neurological problems, but there's not agreement about how to diagnose and treat the infection.
After all, Lyme disease has been called the great imitator. Its symptoms often mimic those of many other ailments. So how is Lyme disease transmitted? Why is it so tricky to detect and treat? And are we really seeing more of these nasty ticks than ever before?
If you have a question about Lyme disease, give us a call. Our number is 1-800-989-8255. That's 1-800-989-TALK. If you're on Twitter, you can tweet us your questions by writing the @ sign, followed by scifri. If you want more information about what we'll be talking about this hour, go to our website at www.sciencefriday.com, where you will find links to our topic.
Let me bring in our guests. Dr. William Schaffner is professor and chair of the Department of Preventive Medicine and professor of medicine in the Division of Infectious Diseases at Vanderbilt University School of Medicine. He joins us from Nashville today. Welcome back to SCIENCE FRIDAY, Doctor.
WILLIAM SCHAFFNER: Good to be with you, John.
DANKOSKY: Dr. Thomas Mather is a professor of public health entomology and director of the Tick Encounter Resource Center at the University of Rhode Island. People refer to him as the tick guy, and he joins us today on the phone from Kingston, Rhode Island. Hi there, Dr. Mather.
THOMAS MATHER: Hi, John. Glad to be with you today.
DANKOSKY: I'll start with you, Dr. Mather. When exactly is one most at risk of contracting Lyme disease?
MATHER: Well, the season of greatest risk is when the nymphal stage ticks are out. That's the poppy-seed-size tick that happens to be out right now. So this year, with the warmer winter, I think they came out a few weeks earlier than normal. So we're not quite in the peak of their season yet. It's still a little bit early, but people are finding them right now and through July, usually.
It depends on the humidity that we get in the early part of the summer. If it's hospitable to ticks, which means higher humidity, then the ticks will linger on into the summer longer. And if we get drier conditions, they'll die off a little bit sooner, and so people's tick encounter risk will be a little bit less.
DANKOSKY: What kind of habitat do they like? It is just woods? It is fields, any types of plants more than others?
MATHER: Yeah, so, definitely woods. They're in leaf litter. These poppy-seed-size ticks hide in the leaf litter, and then will latch onto small animals that run through the leaf littler, like mice and chipmunks or ground-dwelling birds, or people that are shuffling through the leaf litter along a woodland trail.
But they often are around the edges of people's yards and in their shady gardens, as well, places where you see mice and chipmunks running, then - those are likely places that these ticks can be, as well.
DANKOSKY: And explain the different types of ticks we're talking about, here - deer ticks, dog ticks, what are the ticks we need to be worried about?
MATHER: So there are about nine species of human-biting ticks across the United States, and happily for us, only two species really are transmitters of Lyme disease spirochetes. Both are - have fancy names, called Ixodes as the genus. And the main culprit is Ixodes scapularis. That's the Eastern black-legged tick. Some people refer to it as the deer tick, as well.
And then there's the Western black-legged tick, and people just refer to that as the Western black-legged tick for some reason. Don't know why. And so we get transmission wherever those ticks occur.
The other ticks, like the American dog tick that people are probably a little bit more familiar with, or let's say if you're from the South, the Lone Star tick, yes, they bite. They suck blood. They don't transmit Lyme disease spirochetes, though.
DANKOSKY: So, Dr. Schaffner, are you at greater risk of getting Lyme disease in certain parts of the country? Are these ticks everywhere now?
SCHAFFNER: Well, the ticks are pretty widespread, and as Dr. Mather said, the different species are in different parts of the country. But Lyme disease is concentrated particularly in the Northeastern and North-Central states: New York, New Jersey, Connecticut, where it was first described, Pennsylvania. And then there's a cluster up in Minnesota and Wisconsin, and then another cluster across the country in Northern California and Oregon.
DANKOSKY: And are these ticks moving around as the weather changes, as maybe the temperatures warm up?
SCHAFFNER: Well, I think they're transmitted usually locally, but if they get on deer, for example, the deer can carry them from one part of the forest or the woods to another.
DANKOSKY: So how exactly is Lyme disease transmitted to humans? And maybe you can explain this. Dr. Mather, I'll go to you first, and then maybe Dr. Schaffner, you can jump in there.
MATHER: Well, so people get Lyme disease after they're bitten by a tick. The ticks carry pathogens that they pick up from reservoir hosts. So it's a bit of a complex life cycle, in a sense. There are two - I'm going to have to describe two groups of animals involved in this.
There's a group of animals that just provides blood for the adult-stage deer tick, or Western black-legged tick. Those are white-tailed deer, for the most part. They'll feed on dogs. They'll feed on cats, but the populations are really supported by feeding on deer.
But the deer don't infect these ticks. The deer probably infected themselves, but they don't have enough of a dose of the pathogens to infect the ticks. So they provide blood. The blood is used by the adult ticks to reproduce, to lay eggs. They can lay 1,500 or 2,000 eggs, each tick.
And so then the stage that hatches out of the eggs, though, they're called larvae, and the larvae will feed on a whole variety of animals. And if they happen to feed on another group, mainly rodents, white-footed mice, chipmunks, then they potentially pick up pathogens from them. And then they carry those pathogens into the next stage, which is that middle stage that we refer to as the nymph. It's the poppy-seed-stage tick.
So, generally speaking, nymphs that bite through the summer and then adults that bite in the fall and winter and spring are the stages that are infected. But because the adult ticks are a little bit bigger, they're more readily seen by people and more frequently removed before the transmission of the pathogens occurs.
But the nymphs, being so small - basically, sneaky biters - they crawl up to places that most people never look, like around their backsides, and they get bitten. And before you know it, that's how the transmission can occur.
DANKOSKY: Dr. Schaffner, what else should we know about this, about this cycle that they go through when they start biting you? Do they have to hang on for a certain amount of time before you get infected?
SCHAFFNER: Well, the longer they hang on, the more likely it is that transmission - if that tick happens to be infected - will transmit the organism, the bacteria, to us. And so there's much to be said that if you've been out and about, check yourself when you come back in and have somebody else check the back of your hair and, as Dr. Mather says, your backsides also, because you can't really twist around and see that very well.
DANKOSKY: If you want to join us - what's that?
MATHER: They can be pretty clever. My story is that a few years ago, my wife bought me the biggest mirror the local furniture store had, and - with a little note that said: You're on your own, buddy. Good luck. So...
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DANKOSKY: Well, if you want to join us with some of your tick stories and to ask questions about Lyme disease, 1-800-989-8255. That's 1-800-989-TALK. Let's go to Dustin, who's in San Antonio. Hi, Dustin.
DUSTIN: Hi. My question was - I'm an avid hiker. Most of my hiking has been in the Appalachian Mountains around Virginia. And I've probably been bitten by at least two or three dozen ticks and have caught, I don't know, maybe 100 or 200 throughout my hiking career.
As I understand it, Lyme disease is very difficult to detect, and I don't know of any symptoms that I have. But what should someone in my position do? Should I get checked? Is the test even reliable?
SCHAFFNER: So, Dustin, what you ought to do is just be aware the fact if you develop any skin lesions, because the hallmark of the early stage of Lyme disease is a really quite prominent skin lesion, which is red and spreads in a circular fashion. It just kind of spreads out. And that's called erythema migrans - the migrans because it continues to enlarge. Erythema means that it's red, and that's the hallmark.
And if you get that, get some attention quickly. They can diagnose Lyme disease and give you appropriate treatment.
DANKOSKY: This is the so-called bull's-eye lesion, but not everyone gets it, right, Dr. Schaffner? I mean, you can have Lyme disease, but not get this rash.
SCHAFFNER: That is correct, but the vast majority of the people do. Some of the people who think they didn't have the lesion probably had it someplace where it was not readily seen.
DANKOSKY: So does this warm winter mean that we're going to see more cases of Lyme disease this year? We were hearing early on about the humidity maybe making ticks a little bit more active. Dr. Schaffner, do you think this warm winter means we're going to see a lot more Lyme this year?
SCHAFFNER: Well, I dare say. Now, down in Tennessee, we have more of the dog-tick-transmitted Rocky Mountain spotted fever, and we've already had more cases this year than we've had in comparable periods in the past. So we're looking out for all kinds of tick-transmitted diseases.
DANKOSKY: So Rocky Mountain spotted fever, not just Lyme disease. There's a host of these other disease that ticks can carry. Do we need to worry about all of them?
SCHAFFNER: Sure. There are just more ticks going to be out there, because the winter has been mild, just as Dr. Mather said. So there's another disease called Ehrlichiosis, and the variety of ticks are going to be out there, I think, in abundance this year.
DANKOSKY: And, Dr. Mather, do you think the same thing?
MATHER: Well, I think that there are definitely more ticks in more places than ever before, and I will include all of the different species of ticks in that statement. And that, I think, is something worse exploring a little bit. I have my pet hypotheses about that.
But I really am not as sure that the warm winter has much to do about the levels of ticks. I think the timing of them is affected by the warmer winter. But, for instance, in the case of deer ticks, the adult-stage ticks were active all winter. A lot of times in the Northeast and North-Central states, they are buried in snow, and so they're not really active in the winter.
So this year, they were active across the winter season, and I believe that caused them to actually disappear a little bit sooner than they normally do, because they had used up all of their energy reserves.
DANKOSKY: Well, when we come back from this break, we'll talk a little bit more about diagnosing Lyme disease and why that's so difficult.
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DANKOSKY: And this is SCIENCE FRIDAY, from NPR.
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DANKOSKY: This is SCIENCE FRIDAY. I'm John Dankosky. We're talking this hour about diagnosing and treating Lyme disease and about the blood-sucking ticks that carry Lyme. We're talking with Dr. William Schaffner, professor and chair of the Department of Preventive Medicine and professor of medicine in the Division of Infectious Diseases at Vanderbilt University School of Medicine. Dr. Thomas Mather is professor of public health entomology and director of the Tick Encounter Resource Center at the University of Rhode Island.
If you have questions about Lyme disease or ticks, 1-800-989-TALK, 1-800-989-8255. So Dr. Schaffner, why is Lyme disease so tricky to diagnose?
SCHAFFNER: Well, it's tricky to diagnose because first of all the skin lesion may not be something that you see if it's in a part of the anatomy that you don't normally look at. Second, it can be associated with a number of symptoms - not feeling so well, neck pain, headache, a sense of fatigue and then chills and fever. You notice they're all rather non-specific, and they may not be severe enough to take you to the doctor.
And then, of course, the disease can have in its later phases some other manifestations. You can get more than one skin lesion, and you can have some neurologic effects. You can get a form of meningitis or a paralysis of one of the nerves of the face.
So you can see these are unusual manifestations that both patients and some doctors won't put together if they are not familiar with the disease.
DANKOSKY: Jared's in New York City. Hi there, Jared.
JARED: Hi. My daughter had Lyme disease for over a year, and the trouble we had with diagnosing it was, as we later learned, the symptoms show up differently in children than do adults. She didn't have any skin lesions or any of the fevers, things like that, but she had swollen joints. And so between the episodes of these symptoms occurring, the doctors just didn't think it was - just didn't think to check if it was Lyme disease. I just wanted to make that point. I'll take my response off the air.
DANKOSKY: Thank you very much, Jared. Dr. Schaffner, is that true? Do kids get it differently than adults?
SCHAFFNER: Well, the emphasis may be a little bit different, but Jared is actually right. A later manifestation of Lyme disease can be arthritis of many of the different joints but particularly of the larger joints. And that may not be a diagnosis that comes immediately to mind when you see a child with arthritis.
DANKOSKY: John's in Green Bay. Hi there, John.
DANKOSKY: What's your question?
JOHN: I had Lyme disease about four years ago and had the whole range of symptoms: fever, chills, profuse sweating, 103 degree fever. I'm wondering if there's been any immunity connected now with my having had this in the past.
DANKOSKY: Good question. Is there immunity?
Yeah, John, there is some immunity, although second cases have been described on occasion. The important thing to also note is that these are treatable infections, and the earlier we can see the patient, the more effective and easy the treatment is.
Now, second cases is one thing. What about the idea of chronic Lyme disease? This is something that is very, very controversial. Some people say once you get Lyme disease, you can have Lyme disease forever. What do you think, Dr. Schaffner?
SCHAFFNER: Well, you won't find that described in the medical literature, and it's controversial in the sense that there are indeed a group of people, patients, who have longstanding symptoms who believe they have a form of what is called chronic Lyme disease. But the medical evidence for that, the scientific evidence for that, is thin if not nonexistent.
And so the experts don't believe that such a syndrome exists, and it must be another illness that is causing those symptoms.
DANKOSKY: But what about those people who have long-term illnesses who keep coming back with some of the same things, some of these things that you've described before, maybe even neurological problems that persist after being diagnosed with Lyme disease?
SCHAFFNER: Well, Lyme disease ought to be treated definitively, depending upon the stage of the illness, with antibiotics. And then to the best of our scientific evaluation of patients, they should be cured of the infection, and that if one has continuing symptoms, one would be advised to look elsewhere for a cause for those symptoms.
DANKOSKY: Let's go to Mary, who's calling from Indiana. Hi there, Mary.
DANKOSKY: You're on the air, go ahead.
MARY: Yup, okay. I had Lyme disease 21 years ago, and at the time I was four and half months pregnant. I went through the treatment, which for me had to be erythromycin because of a penicillin allergy. And my child was born with an angry red rash, and she's now 21, and boy, those rashes have persisted. She has a lot of allergy problems.
And at the time of my diagnosis, the CDC didn't really have much information at all about Lyme disease and pregnancy, and I'm kind of wondering if there is much more information now.
DANKOSKY: Thanks, Mary.
SCHAFFNER: Well, I'm sure I have to respond to that. I can't look to Dr. Mather. But I'm not aware of a great deal of information on Lyme disease in pregnancy, and I'd have to go to the literature and look that up, John.
MATHER: There were some studies back probably in the '90s that suggested statistically that there was no higher incidence of issues in human fetuses than from mothers with Lyme disease diagnoses than others. People had taken that to issue because they were smallish studies.
We at the time had done a mouse study where I know mice aren't people, but we showed that there actually was no congenital infection from infected mice to their offspring. So that calls into question whether there is any real relationship, but I would argue that probably more studies are needed.
DANKOSKY: Now, James is calling from New York. James has a question about the test for Lyme disease, an important question. Go ahead, James.
JAMES: Hi, I have had chronic Lyme disease for seven years, leading to widespread joint pain throughout my body. One of the first thing that I suspected was that it was Lyme disease, and I got a Western blot test, and it came out false negative.
Five years later, after several doctors, I find out that it was in fact Lyme disease with a more rigorous test. How often is there a false negative with Western blot?
SCHAFFNER: Well, James, you open up all kinds of things. As I said, the diagnosis of chronic, so-called chronic Lyme disease, is in medical circles suspect. And perhaps that first test was negative, and we are concerned about some laboratories that over-interpret weakly positive results.
So I can't speak to your individual case, but would hope that you're in the hands of a good physician who's knowledgeable in this area.
DANKOSKY: Is it true, though, Doctor, that the testing is not always reliable? You end up with false positives sometimes, false negatives. It's not as reliable, perhaps, as it could be. Why don't we have a better test for Lyme?
SCHAFFNER: Well, science can do only what science can do, and we would all like a more precise test for Lyme disease. The testing is better now than it was 20, 25 years ago, and we just hope that the folks in the laboratory can come up with a better test.
DANKOSKY: So in the absence of some reliable testing and all these trickinesses about diagnoses, Dr. Mather, what about prevention? What can we do to keep ticks form feeding on us and passing on Lyme?
MATHER: Well, there's a lot of great opportunities there, I think, that we already know, and there's ongoing research to try and improve that as well. Let me start with personal protection. The best personal protection against deer tick bites and pretty much any kind of tick bite is tick-repellant clothing.
It's kind of something that people don't really know much about, despite the fact that the military has used this for 30 years to protect troops. It's clothing that is impregnated with the active ingredient Permethrin. You can buy sprays and soaking kits and do it yourself, or there are - is - there are commercially treated clothes available as well.
And these clothes, it provides protection that really makes - it's as easy to do as getting dressed in the morning if you do it regularly because you have these treated clothes and they can go through - the commercially treated clothes can go through 70 washes and still be effective.
So it's something that we wish more people knew about because it takes just a brief contact with this clothing for the ticks to sort of fall off. And they don't just fall off. If they've gotten enough of a dose, they actually die. So that's good news.
DANKOSKY: And Dr. Schaffner, very, very quickly, what should you do if you find a tick on your skin?
SCHAFFNER: Well, the way to remove the tick is to take some tweezers, grasp the tick absolutely as close to the skin as possible and then slowly pull back. Don't jerk the tweezers.
DANKOSKY: Because you don't want to leave anything behind.
SCHAFFNER: You don't want to leave the head behind - that's correct - because then transmission can still occur.
DANKOSKY: We've just about run out of time here. Dr. William Schaffner is professor and chair of the Department of Preventive Medicine and professor of medicine in the Division of Infectious Diseases at Vanderbilt University School of Medicine. Thanks for joining me.
SCHAFFNER: Thanks, John.
DANKOSKY: Thanks also to Dr. Thomas Mather, professor of public health entomology and director of the TickEncounter Resource Center at the University of Rhode Island. Thanks so much.
MATHER: Thank you, John. Transcript provided by NPR, Copyright National Public Radio.