What Causes Lyme Disease?
Interview with Entomologist Dr. Adela Oliva Chavez
We take a deep dive into the science of Lyme disease transmission by talking with Texas A&M Professor of Entomology, Dr. Adela Chavez, to find out how ticks and bacteria work together to spread Lyme, and how her research is uncovering ways to stop these harmful “vectors” and “pathogens” in their tracks.
Dr. Chavez at Texas A&M University Department of Entomology
Dr. Chavez’s recent article about Ticks and Bacterial Infection
What pathogen causes lyme disease?
Lyme disease is caused by the bacterium Borrelia burgdorferi, which is transmitted to humans through the bite of infected blacklegged ticks, commonly known as deer ticks. These ticks acquire the bacteria by feeding on small mammals, such as mice and chipmunks, which serve as reservoir hosts for the germ. Lyme disease is prevalent in certain regions where these infected ticks are abundant, particularly in wooded and grassy areas. If left untreated, Lyme disease can lead to a range of symptoms, including fever, fatigue, joint pain, and neurological issues. Early detection and prompt treatment with antibiotics are crucial in managing Lyme disease and preventing more severe complications.
Does lyme disease compromise your immune system?
Lyme disease itself does not generally compromise the immune system, but the symptoms and complications associated with the infection can impact immune function. The bacterium Borrelia burgdorferi, which causes Lyme disease, primarily affects the joints, skin, heart, and nervous system. While the immune system responds to the infection by producing antibodies and activating immune cells, the bacterium has evolved mechanisms to evade the immune response, leading to persistent infections in some cases. Additionally, the inflammatory response triggered by Lyme disease can cause fatigue and stress on the body, potentially affecting overall immune function. It's crucial for individuals with Lyme disease to receive prompt and effective treatment to reduce the risk of complications and support the immune system in combating the infection.
Are ticks born with lyme disease?
No, ticks are not born with Lyme disease. Instead, they acquire the bacterium Borrelia burgdorferi, which causes Lyme disease, by feeding on infected hosts during their life cycle. Ticks go through several stages of development, including larva, nymph, and adult. The larval and nymphal stages usually feed on small mammals and birds, which can be reservoir hosts for the Lyme disease bacterium. If these hosts are infected, the ticks can acquire the bacteria during their blood meal. Once infected, the ticks can transmit the bacterium to other hosts, including humans, during subsequent feedings. It's important to note that not all ticks carry the Lyme disease bacterium, and the risk of transmission depends on various factors, including the tick species, geographic location, and the prevalence of infected host animals in the area.
What insect carries lyme disease?
Lyme disease is primarily transmitted to humans through the bite of infected ticks, with blacklegged ticks, also known as deer ticks, being the primary vectors for the causative bacterium Borrelia burgdorferi. Blacklegged ticks (Ixodes scapularis) in the eastern U.S. and western blacklegged ticks (Ixodes pacificus) are responsible for almost all human cases of Lyme disease. Although mosquitoes and other insects are not known to transmit Lyme disease, taking precautions such as using insect repellent and wearing protective clothing in areas where ticks are prevalent is crucial in preventing tick bites and reducing the risk of contracting Lyme disease.
You may also like...
Transcript of the Interview
Mark at Insect Shield
We're talking today with Dr. Adela Oliva Chavez, who's a Professor of Entomology at Texas A&M University, and we are going in depth today. Her research focuses on interactions between three things: ticks - that spread disease - sometimes called the “vector”, and bacteria carried by the ticks - that cause the disease - and then their hosts. So those could be humans, or other animals. And we're going to try to understand a little bit more about this. From what I understand this research also can have applications in the area of medicine, even vaccines, and veterinary treatment for things like livestock. So, Dr. Chavez, welcome to the Insect Shield blog. It's really nice to have you here.
Dr. Chavez
Hi. Thank you for having me. This is a great opportunity. And I really love that you're educating people about transmission of vector-borne diseases.
Mark at Insect Shield
We have other entomologists that we work with, and they're kind of focused on the prevention side, like Dr. Thomas Mather, who is working on a kind of sign that can be placed with a QR code, that can be scanned, and people can get information immediately. One of his things is, like, when [people are] going to go for a hike, they can't really change [into bug repellent clothes] at that point. I mean, you know, they need something they can use right then. So, that's the kind of stuff we're [supporting].
But today, we're really honored to have you here and talking about the research more in depth into this area. So I think with those three things: the ticks themselves, and the pathogens that they carry, and then the human that's going to suffer from these infections, and you've done a recent paper about this, too.
Dr. Chavez
Yes. So we look at the interface between the three. So if we think about it, when they are transmitting those pathogens is when they are biting you. So that is what we call the interface at the skin side. And it's not a vague area, it's just a couple millimeters around where the tick is biting. And what happens is that ticks have evolved to actually diminish the immune responses in animals, in vertebrates, and also in humans, because they are what we call obligatory blood feeders, meaning that it's not like a mosquito, for example.
The mosquito, you have the male that doesn't bite humans. It just feeds on sugar. Ticks, both the female and the male, and all the life stages, they need to feed on blood, because that's where they get the proteins and the fats in order to pass to the next life stage or to develop the eggs.
And they feed for a very long time. So if you think about the bite of a mosquito, it comes for a couple seconds, it pierces through the skin and finds a blood vessel. And that's how they feed. In the case of the tick, what they do is they are what we call “pool feeders.” They come in with their mouth parts that we call a hypostome. And they have what we call chelicerae. That is two cutting extractors. They cut through the skin, and the tick puts the hypostome in. And in the first 24 hours, they put in a solution that we call “cement” that is like a glue.
Actually, it's funny that you mentioned the medical application because people are looking at this cement as a probable glue for surgery, you know, because it's very potent. Like if you pull a tick, it's really hard to get out. And it's because of this cement that they put on the spot. And it also protects the mouth parts from cells that might come to try to kill the tick. And after those 24 hours, they start injecting other molecules that delay the closure of the hole and also work as facilitators making the blood vessels bigger so there is more blood coming in so that they can feed better.
And all those molecules are also helping the pathogens, because there you have an area that is going to have diminished immune responses, and it’s perfect for any pathogen to actually get established there, because you have a different set of cells that will not normally be there. So they can escape the immune response. And then that's how you get Lyme disease and other diseases. Because as I was telling you, Ixodes scapularis [i.e., the blacklegged tick, or deer tick] transmits many more pathogens, not just Lyme disease [for example] anaplasmosis, ehrlichiosis in the area of Minnesota and Wisconsin, and there are other pathogens that are transmitted by the same tick.
Mark at Insect Shield
Yeah, that's something that people haven't been aware of. But some of these are more serious, right? In terms of the diseases that they can spread.
Dr. Chavez
Yes. Because what happens is that people can get even more sick. So there have been studies where they have shown that when people have Lyme disease, then there’s another [bacterium] called human babesiosis. This is a protozoa. So it's actually similar to the agent of malaria. It’s actually a eukaryote; it’s not a bacteria. And people get very sick with that particular pathogen. And the other one that I work with is anaplasma phagocytophilum, and human granulocytic anaplasmosis. And that one makes it hard to diagnose. So they can be misdiagnosed for Lyme disease.
And then you get the late Lyme disease, which is when people start developing palsy, arthritis, and heart problems. Because if you treat all the diseases early on, it's not such a big problem, like human granulocytic anaplasmosis causes high fevers and you feel really sick, but it's like flu. But if you're immunocompromised, you can even die. And in the case of Lyme disease, if you don't treat it early on, there are chances that you're going to have complications.
Mark at Insect Shield
So this is really interesting, in terms of the way that these bacteria have evolved, right, because they have this sort of ability, but the tick is facilitating the same kind of thing. So I think I read that they have kind of a symbiotic relationship.
Dr. Chavez
Yes they do. Because we don't think about the amount of time that they have been in a relationship. For example, borrelia or the first borrelia-like organism found in ticks was 15 million years ago. They have been together for millions and millions of years. It's just that we either have not been aware that they are in humans, or we have not been paying attention.
Many of the times the fact is that people are not aware of the pathogen being in a specific area, and like a specific set of symptoms we tend to say this is something else. Like my sister when she was younger, she got rickettsia, and the doctor said, “Oh, this is dengue,” because they are so used to diagnosing dengue where I am from, that they just misdiagnosed it.
Mark at Insect Shield
Dengue is the disease that you're referring to?
Yeah. Dengue fever. I come from Honduras. And we have a very pronounced dengue season, but my sister actually got a rickettsial disease. It’s transmitted by a different tick. It's also tick transmitted. But back in those days, we didn't know about it.
So they were like, “Oh, this is dengue,” because she had fevers. But she got treated with antibiotics and then she got better, but that's one of the problems. We're not aware of the presence of the disease and then it gets misdiagnosed.
And so because they are symbiotes living on the tick, they also have a way to change the saliva of the tick. So pathogens can also manipulate the expression of specific genes in their advantage. For example, borrelia burgdorferi needs a particular protein that is called Salp15. And it’s very interesting because what the bacteria does is it coats itself with this protein that is in the saliva of the tick. And this protects the bacteria from antibody recognition. And the bacteria itself increases the expression of this protein in the saliva of the tick.
So these little creatures have evolved all these mechanisms to be able to infect you.
Mark at Insect Shield
Right. Like you say then, we're only just now learning about how these things work. So it's, in some ways, the more you look into it, the scarier it gets! That's not really the point. But yeah, so that's really fascinating. Now, if you're doing this research, obviously, you want to do more. I think you pointed out in your paper, we're only kind of scratching the surface, in terms of our understanding. But what about the applications for this? Like, I think you mentioned possible development of a vaccine, which would also be based on the research, right?
Dr. Chavez
The paper I published, it actually looks at some small particles called exosomes, an extracellular vesicle. And we all produce them, like we humans, we produce exosomes. And, we find them in the saliva of ticks. We find these micro vesicles, these exosomes.
Many of these exosomes have all these effector proteins that the pathogens are taking advantage of. So if we can take these exosomes, which they already have all these proteins that the tick needs and the pathogen needs, and we can then use them in a vaccine, injecting into an animal or injected into humans after FDA approval, then the humans will, and the animals will, develop an immune response against those proteins.
So if we are recognizing these proteins, and we are destroying these proteins, then we can stop the tick from feeding, because now we can kill the tick. And now we can potentially also deal with the pathogen. So that's one of the things that we're investigating right now: Can we use these exosomes as vaccines to prevent the feeding while proteins in these particles, in these exosomes and intracellular vesicles are being recognized by the immune responses.
Because the process of purifying these vesicles is very complicated. The idea that we have is if we can recognize what proteins these are, then we can engineer our own vesicles. Most people don't know this, but if you think about the COVID vaccine, this COVID vaccine is messenger RNA that is inside of what we call a liposome, this liposome is actually a vesicle, an artificial vesicle made to carry the messenger RNA. That's what we want to do. We want to make our own liposomes carrying these proteins so that we can vaccinate people.
Mark at Insect Shield
That makes sense. And so you're talking about the extra cellular vesicle, right? But every sort of organism, in some sense, uses those same kinds of vesicles to transport or interact between cells.
Dr. Chavez
Yes they do. But each of the cells in your body makes their own vesicles. So the message in the vesicles in your body are different to the messages in the tick. And these vesicles are fascinating because now we're finding that they can be used for many things. So they are using them for cancer diagnostics, for looking to see if you can use it for diagnosis of Alzheimer's, even malaria, because any disease changes the cargo of the vesicles, the message that is being sent. Like in the case of cancer, the cancer cells change the vesicles. So that they can metastasize.
It is like sending a message to wherever they are going to go. Okay, we're going to establish in this other organ, so we're sending out these vesicles. So now we can harness those vesicles knowing that they have a different message and looking at it, like, “Okay, what is this different message?” And what in these vesicles is causing an immune response so that we can take advantage of that immune response in order to then attack whatever this is, the disease or a pathogen, or in my case, the tick.
Mark at Insect Shield
Got it. So the vesicle is just this thing that communicates from a cell, or you can have that communication happening inside the cell. Is that right?
Dr. Chavez
Yes. And the interesting thing is that these vesicles accumulate in certain places, like liquids, so for example, you can find certain vesicles in the saliva. And so that's what we're working with, the vesicles from the tick saliva, and I actually am also working with the vesicles from the mid gut of the tick, because if we can produce antibodies that will damage the mid gut of the tick, the ticks will die as they are feeding, is the hypothesis that we have, so all the organs or the cells in your body, they are producing these messages. So we are looking at that: How can we use these messages that the tick is using to live, in order to kill it?
Mark at Insect Shield
So what would that look like in terms of administering that? Is that called a vaccine then when you apply that knowledge?
Dr. Chavez
It will be an extracellular vesicle-based vaccine.
Mark at Insect Shield
Got it. And there's talk about this, because I think that the idea right now is there's no vaccine for Lyme disease. Right?
Dr. Chavez
No, not for human use. So there was one back in the 90s. I think it was before I came to the United States. That was based on a protein that is in the outer surface of the bacteria. Yeah, and it’s a protein that is needed for the bacteria to infect. But what happened is that there was a public backlash against the vaccine, because some people were actually reacting badly to the vaccine. So it was taken out of the market. But now there is a vaccine available for dogs that is based on Humira [adalimumab].
So what happened with this protein is that this outer surface protein, is that it changes from different isolates. So that was the problem, the vaccines against one particular bacterial isolate will not work against another bacterial isolate. So now they are making what is called a “chimera,” that is a protein made of several proteins, so that the same vaccine will work with all different isolates of the bacteria, but this is only available for dogs. So there is not anything that is available for humans. From what I know, they are trying to see if this vaccine is safe for humans, but it's not available on the market.
Mark at Insect Shield
Obviously it has to go through the whole approval process and so forth. So that could take years. And, you know, Insect Shield works with a number of Lyme organizations across the gamut of prevention and treatment, diagnosis, [but] there's still, like you were saying, there's not a great understanding at this point. So you can go a long time without getting a proper diagnosis. But who would want to use the vaccine then if it were available for humans? Would it just be that everybody would get it?
Dr. Chavez
It used to be that Lyme disease was affecting specific groups of people, like people that tend to be outdoorsy, people that work in parks, things like that, like those who are more prone to have it. But right now, like I was telling you, because of the expansion of tick populations, and the fact that now we have urbanization like suburban areas going into wooded areas. So you have deer passing through your yard or something.
Mark at Insect Shield
Yeah, against the woods, in the woods.
Dr. Chavez
Exactly. So now these people can be exposed to a tick carrying the pathogen in their backyards. And that's a problem. So I will say that anybody that is in areas where there is high prevalence of Lyme disease, should get vaccinated, because I know people that had the disease and it is very debilitating. People can get palsy, or lose movement of one region of the body, or develop heart problems and cannot do the things that they were doing before.
Mark at Insect Shield
So along those lines, I mean, these bacteria are somehow benefiting, right? They're in the body to benefit from the environment? Or why are they doing this?!
Dr. Chavez
It’s like anything. It’s survival, right? Because this is a special kind of bacteria. So these bacteria, they need to be in both the tick and the vertebrate host, because there is a process that we call transovarial transmission that happens in some pathogens, when the mother can pass it to the offspring in the case of the vector, so let’s say that the female tick passes it to the larvae. That doesn't happen with borrelia. That doesn't happen with anaplasma phagocytophilum. They are not passed from the mother to the offspring. So if you don't have that vertebrate host that get sick, then the bacteria is dead; they disappear. So they are doing it to complete their cycle. They are selfish. They don’t care about, “I'm gonna make this person sick.” They just want to survive.
Mark at Insect Shield
Oh, I got it. So one of the folks that we interviewed, Dan Wolff, was talking about this, that it's the case because it's not passed from one tick to another, that the larva at the very early stage don't carry it. So you could be bitten by those larva. But you're not going to get Lyme because they don't have it yet.
Dr. Chavez
Yes. They don't have it. So if you if you are, that's what I tell my students all the time, if you're bitten by the larvae, don't worry about it, because they are not likely to have it. They might have viruses like the Powassan virus, because that can be transovarially transmitted.
Mark at Insect Shield
Powassan? Which can even be deadly. Right?
Dr. Chavez
Yes, that is like a tick borne encephalitis in the United States, and you find it in some areas, like in the New York area. In the Northeast, mostly, we find cases. It's not that many cases, but those are going up too.
Mark at Insect Shield
Right. I think it's important for people to understand those differences, because we're talking basically about the deer tick, right that carries Lyme. But there's like four different stages of the life cycle. Is that right? We're talking about larva and nymph, but the nymph from what another of the people that we interviewed, Logan McCullough, said, he had nymph bites, 20 nymph bites, but that was enough to carry this severe Lyme disease. And then after that, they grow bigger. Most people are only familiar with the larger ones, the adults.
Dr. Chavez
Yes. And the funny thing is, that it’s not so much of a problem as a nymph. Most of the transmission happens during the bite of the nymph, because they are so small, and you can have many and you don't realize it. So what happens during the cycle is that usually you have the eggs. That's the first stage. The eggs hatch, and then you have larvae, and the larvae will feed on likely an uninfected host. But they can feed on a mouse or another host that is infected with Lyme disease. And then they acquire it.
Once they acquire the bacteria, they will go through the molting. So they will retain these bacteria, and then the nymph is infected. And then when this nymph bites a human, then they will transmit the disease. And then the more ticks you have transmitting it, because they do this. So ticks have pheromones that they send to each other. It's like a chemical, a cue that they send to each other: “I found a place where we can feed.” So they congregate, and they feed together.
Mark at Insect Shield
Like a party.
Dr. Chavez
Like a party, yeah, like, “There are drinks here. Come over!”
Mark at Insect Shield
They're not social distancing either when they have these parties.
Dr. Chavez
Yeah. They go like, “Oh we don’t care about corona!” So sometimes you can have ticks aggregate and then this immunocompromised site is even more immunocompromised, because you have many ticks throwing these effector molecules that are affecting our immune system, and then you have even more bacteria that establish themselves and then you get even more severe Lyme disease.
Mark at Insect Shield
So that was one point that Logan McCullogh made, which I found really interesting. He said the first line of defense is really the immune system. So if it's already compromised in some way, then you're much more susceptible to bacteria. But that's not a guarantee, I mean, anybody, even if their immune system is in good shape, is still susceptible to the bacteria?
Dr. Chavez
Yes, we're all susceptible to the bacteria. Bacteria use what are called receptors, they use receptors that are found in bodies to bind and to infect us. And we all have them. Just some people have a better immune system, and they might be able to clear the disease without it becoming severe. But even if you don't, if you're not immunocompromised, you might have some other disease that is affecting your immune system, and then you might get severe complications. So it's not that many people develop the late severe Lyme disease, but a big percentage, like 10% of people that might actually [get Lyme disease] are not just immunocompromised.
Mark at Insect Shield
So it sounds like one of the keys there, like you mentioned, is really early diagnosis or finding these ticks early on, and that's something that people can do. I mean, from Insect Shield’s standpoint, prevention is easier than reacting to actually getting the infection. I mean, it's not hard to put on insect repellent clothing. And then to follow guidelines like walking in the center of the trail, but if it's in your backyard, I mean, that's tough too, and then the dog also can go out and bring them in the house.
Dr. Chavez
Yes. That’s where it becomes key checking yourself like even when you are taking a shower, after you went outside, or work in your garden, if you were close to the wooded areas, because what happens is that it takes quite some time for transmission to occur, like I was saying the secretion of the saliva changes through phases and it’s the same with the transmission of pathogens. So in the case of bacterial pathogens, like the Lyme disease agent, this pathogen has to replicate inside of the tick. So what happens is when the tick bites you and it starts to take in blood, that sends a cue to the bacteria telling them okay, now we can be transmitted.
So they start replicating in the mid gut, and then they have to make their way to the salivary glands. So for Lyme disease to occur, that tick has to be feeding for more than 48 hours. So if you got that tick in the first 24 hours when they were feeding, you are likely to be okay. So people should be checking themselves after doing outdoor activities or when they are taking a shower, like we shower every day, right? So if you live close to wooded areas where your dog might bring in a tick, to check your kids when you're showering them and check yourself when you take a shower.
Mark at Insect Shield
Yeah, and so the other important part of that, I guess, is if you find a tick, the way to remove it is also really key because you don't want to squeeze it or try to do it with your fingers.
Dr. Chavez
Yes. Don’t put Vaseline - I have heard everything - like put Vaseline on top of the tick. That doesn’t work! Mark at Insect Shield
I mean, killing the tick is not the goal, you know, you can be mad at the tick, but it's not really gonna help. It's important to use these very fine tweezers and then grasp it and like you said, it's got that kind of cement. So you really have to be careful to pull it straight up. Yeah, those kinds of things. So that's really critical, too. You know, like Dr. Mather, like I mentioned, it's like education around this, the tick habitats, all this stuff. And then removal is really important. And I think there's still a lot of [misunderstanding] out there about these things.
Dr. Chavez
Yes. People don't know where to find the information that they need about the problem. But because of the Internet it’s becoming a little bit easier. So you can actually put on YouTube, how to remove a tick, and you're likely to find a video showing you or like, for example, what you guys are doing at Insect Shield, you're doing these education videos, so it has become a little better because of the internet.
And the CDC has a webpage, where you can see how to remove a tick. And they give you like a list of things that you can use, of repellents that work against ticks, that there is scientific data showing this works. So I think it's becoming a little better. We just have to let people know, this information is out there, you can find it.
Mark at Insect Shield
I think the one downside of just trying to use Google is a lot of times there's a lot of information, [but not] the real story. So we're trying to do that too, make it easier to find actual stuff. And then, you know, there are more support groups, I think, than there used to be, and the Internet has helped. People can find doctors - or organizations that help them to find doctors - and, can help support people that have these longer term illnesses as a result.
So this is all great, I really appreciate you taking the time to talk to us about this. And it's, it's pretty fascinating. I especially like the idea that by understanding this and doing more research, we can come up with better ways to solve the problem. And I know people get very excited when they hear there might be a vaccine, but I don't think they really understand all the important things that are involved in getting that done.
Dr. Chavez
Yes. Because there are many aspects to it. First, we have to identify what would work, why we will generate an immune response after that, we have to investigate: Is this safe? Are we going to make people sicker? Is it going to, instead of blocking the transmission, is it actually going to make it worse? And then you have to do the same thing with kids because the immune system of kids is different to a well-developed immune system of an adult. So those are all the things that have to go through the process.
That's why it takes normally several years for the development a vaccine. But the good thing is that they are understanding the process. We're not limited to just vaccines. We might find molecules, that if we treat somebody with this, a specific molecule, we enhance their immune system and then their immune system can kill the bacteria.
So, there are prophylactics, too. Like you can take a pill, or get an injection of something that might prevent you from acquiring it. That's what they do with malaria. There is a prophylactic for malaria. If you go to a country where you know there is malaria, you can take it before going there. So, there are other options that people are exploring as well, besides just vaccine development.
Mark at Insect Shield
Got it. Well, Dr. Chavez, it's been a pleasure. Thank you so much for “making the trip from Texas.” And we we'd love to have you on again, at some point, if you're interested. And I hope your continued research goes well, and you can keep finding these insights about pathogens and especially Lyme. We like to try to keep ahead of that and educate our readers and viewers. So, thanks so much. That's Dr. Adela Chavez from Texas A&M University Department of Entomology.
Dr. Chavez
Thank you very much. It was a pleasure.