Dr. Bill Sullivan
Victoria:
Hello, and welcome to Ask a Scientist, the podcast for kids and adults to ask scientists questions about anything they want to know. There are so many scientists out there doing a lot of cool scientific research in the news. We’re constantly hearing about scientists and there are new ideas and where those ideas are going to take us in the future, but just who are these scientists?
In this podcast, we will learn a little more about who they are and what inspires them as scientists. I’m your host, Victoria, every other week, I’ll sit down with a different scientist and ask them questions written by you, the listeners and by students from classrooms throughout the country.
Hello listeners. Welcome back to the next episode of Ask a Scientist scientists. Our guest this week is Dr. Bill Sullivan. He is a professor at the Indiana University School of Medicine in Indianapolis. He is also the author of Pleased to Meet Me: Genes, Germs, and the Curious Forces That Make Us Who We Are. The book describes how genes, epigenetics, psychology, and the microbiome conspire to shape our personality and behavior. But today Dr. Sullivan is going to be talking to us all about parasites. Thank you so much for being here.
Bill:
It’s a pleasure, Victoria. Thanks for having me on the podcast.
Victoria:
So that was just kind of a brief introduction. Is there anything about you and your work that you’d like to add to that?
Bill:
I, I thank you for that generous introduction. Like you said, I’ve been at the IU school of medicine going on 20 years now and I study parasites in my lab. So I’m looking forward to answering these wonderful questions.
Victoria:
(What are parasites, what problems do parasites cause and what are some common parasites that children might encounter?)
Awesome. Well, these questions come from Mr. R’s fourth grade class at Bromwell elementary in Denver, Colorado. With that, we can start off with this first question from the students. I think it’s a pretty good introductory question. The students want to know what are parasites, what problems do parasites cause and what are some common parasites that children might encounter?
Bill:
Yes, that’s a great question. Great way to start things off. So let me break this down as it’s going to be a little bit of a lengthy answer. So stick with me. A parasite is a life form that lives on or inside another life form, which we call the host and it gets its food and resources from the host. There are three main classes of parasites that can cause disease in humans. There’s protozoa, which are single cells. There’s helminths, which are worms.
And there’s ecto-parasites, which are tics and lice. Some people consider viruses parasites too, even though they’re not technically alive, they cannot reproduce unless they are inside of a host cell. Some people also extend the definition and consider bacteria and fungi that make people sick parasites as well.
Parasites cause many types of diseases and problems in people. They can also hurt people by killing farm animals or crops I’ll list some of the more common parasites that infect people. And I’m going to divide them into categories. First, we’ll start with the classic parasites, the protozoa, these single celled creatures. The one you’re probably most familiar with is the amoeba. Might’ve seen an in cartoons or under your science laboratory microscope. The one we worry about the most is the brain eating amoeba, which sounds as scary and nasty as it is. It’s inhaled up the nose while swimming and warm lakes or ponds. Some of the other classic parasites of medical concern include plasmodium. This is the parasite that causes malaria, which is transmitted by the mosquito. There’s two forms of trypanosoma parasites that live on different continents. The first is trypanosoma cruzi that causes something called Chagas disease and it’s, it leads to heart failure. It can be transmitted by kissing bugs. Trypanosoma brucei, on the other hand, causes sleeping sickness and it’s transmitted by tsetse flies. Another protozoan parasite that’s rather common is Giardia. And this is found in dirty water all over the world. it’s also found in diapers of infected people. So, it’s not uncommon for daycare centers to have a breakout of Giardia. So those are some of the key classic parasites. If we want to include bacteria in the mix, staphylococcus is usually a harmless skin bacteria, but if it gets inside the body, it can cause major problems. You might’ve heard of a disease called MRSA, and that’s a big problem because many of the medicines we use to fight bacteria don’t work against MRSA. Bacteria can also cause pneumonia, strep throat, or infect a cut or scrape that you might get.
Worms are really a big problem in many parts of the world. And those are another major group of parasites. Many of them live inside of your gut in your intestines. We’re talking about the tapeworm, the roundworm. Sometimes they can break out of the gut and get into the brain, which is a really serious condition called neurocysticercosis, usually caused by the pork tapeworm.
Personally, one of the grossest, you know, in my opinion, is loa loa, and this is a worm that lives inside of your eye. Really nasty. If we include viruses as parasites, there’s tons and tons of viruses. I’ll just name a few. The rhinovirus, you may be very familiar with. It causes the common cold. No doubt you’ve had one of those already. COVID is caused by a variety of virus known as the coronavirus, measles and chicken pox also caused by viruses. Some of the ecto-parasites, like I mentioned, ticks and fleas lice, these little tiny bugs, suck out your blood, and that’s why they’re parasitic. They don’t really confer any benefit to you. In fact, some of them can transmit harmful diseases. They can inject bacteria into you as they’re sucking the blood and some of these bacteria or pathogens they can cause Lyme disease. Or as in the case of fleas, they can transmit, in the past bubonic plague, which was also caused by a bacteria.
And then finally, some people would consider certain forms of fungi, fungal pathogens as parasites too. One of the more common ones is ringworm and despite its name, that’s actually not caused by a worm that’s caused by a fungal infection. And then one, you might be familiar with, skin infections. Athlete’s foot is one of the more common ones. And that’s when a fungus grows between our toes and causes skin irritation. So sorry for the long answer, but those are the major categories of parasites, things that make us sick, that I think are going to be relevant to the other questions we have today.
Victoria:
(Why do parasites live in us?)
That is awesome. Very, very informative. Lots of things I had heard of and lots of things I hadn’t heard of before. So that’s awesome. And then this is a great follow-up question from the students. Why do parasites live in us?
Bill:
Well, the simple answer is that our bodies offer free food and a place to stay.They, these parasites steal our materials and our energy in order to reproduce themselves and make more parasites to infect more people. So from a parasites perspective, it’s kind of a clever way to live.
Victoria:
(How many parasites are there and how many of them are deadly?)
Yeah, that does make sense. All right, this next question is how many parasites are there and how many of them are deadly?
Bill:
It’s, it’s really not possible to know the exact number of parasites that are out there, but suffice it to say there’s at least one parasite for every type of living creature. So,the number’s going to be very high. Many of them are deadly if you don’t get medical treatment. Now, fortunately scientists have developed vaccines and other medicines that usually help people fight off the parasites. Before those came along, many people died before the age of 50 because of these infections. And even today, malaria kills nearly half a million people a year. Most of them children under the age of five.
Victoria:
(At any given time, are there parasites on my skin?)
Yikes. All right. And this next question, at any given time, are there parasites on my skin?
Bill:
So not to creep you out, but most likely yes. But they’re, they’re usually nothing to worry about. A lot of people have mites, which are microscopic bugs. You can’t feel them. You can’t see them. And all they really do is eat your dead skin and the excess oil on your skin. So they’re not creating any harm here. As I said before, a bacteria like staphylococcus normally live on your skin too, and they can be helpful in some cases, you know, keeping other pathogens away. And in fact, you have stinky feet at the end of the day because of the waste produced by bacteria that are munching on your dead skin cells. They don’t cause any harm, except to noses that can’t stand the smell of stinky feet.
Victoria:
That’s awesome. I always wondered why feet were stinky.
Bill:
It’s the same bacteria they use to make stinky cheeses.
Victoria:
Oh, interesting. Now I’ll think of feet every time I have stinky cheeses.
Bill:
Yeah. It’s kind of embarrassing when people Google my name and stinky, or if they, if they Google stinky cheese, I usually come up. So that’s a little embarrassing too.
Victoria:
(How do you know if you have a deadly parasite?)
Oh, Oh man. All right. This next question. A good follow-up to that I think is how do you know if you have a deadly parasite?
Bill:
Oh yeah. That’s, that’s a really good question. And it starts by you not feeling well. Okay. You probably developed fever or chills. You get some aches and pains, perhaps a stomachache or diarrhea. Depends what kind of parasite it might be and where it’s affecting the body since parasites live inside of you. And can’t be seen with the naked eye. You need to see a doctor in order to get tested for parasites. The doctor will be able to give you a definitive answer.
Victoria:
Okay. That is good to know. So if you’re feeling fine, you probably don’t have a deadly parasite. Is that right?
Bill:
That’s right.
Victoria:
(Is lice the most common parasite, and what is the most common parasite besides lice?)
All right. Good to know. And now kind of switching gears a little bit from deadly parasites, we’ve got a question about lice: is lice the most common parasite, and what is the most common parasite besides lice?
Bill:
Lice is very common indeed, but studies suggest that a parasite called Giardia is even more common. I mentioned this one at the beginning. It’s a single cell. So, a protozoa that lives in contaminated water and can transfer from person to person. When you don’t wash your hands after going to the bathroom, giardia causes stomach pains and diarrhea. It’s it’s no fun to have. But usually it goes away on its own after a week or two, sometimes without even any medicine, intestinal worms are also very common. They affect billions of people around the world. Usually areas where people don’t have access to clean water, which unfortunately is, is quite common in many areas of the world. So intestinal worms remain quite frequent, you know, amongst people.
Victoria:
Wow. Yikes. And is it true, this isn’t one of the student’s questions, but something that I’ve heard about giardia is that, cause I, you know, I used to backpack and go camping a lot. And so if you, you know, drink water from a mountain stream or, you know, any sort of water without filtering it, you’d get Giardia and get sick. But then after that, you could drink as much contaminated water as you want, and you won’t get sick. Is that true?
Bill:
I’m actually glad you brought that up. Yeah. Giardia is very common amongst hikers and backpackers who don’t take care to, filter their water. Giardia is very common out in the environment in, in, in fresh water. So, I think, it’s known rather affectionately as Beaver Fever, even though it really doesn’t have anything to do with beavers at all. It produces the same symptoms that I described. There is a medicine that people can take, that’ll get rid of it called metronidazole, and that helps people who, have, have, have trouble getting over it normally. But hikers and backpackers should definitely take care to disinfect or boil their water to avoid getting the Giardia illness. And as for recurring infections, I think Giardia, you can get that time and time again. I don’t think we develop a robust immune response to it. I, I would not take my chances if you thought you had giardia in the past. I don’t think you should rely on that as, something you develop immunity to.
Victoria:
(How many parasites can be in people at once?)
That is good to know. All right. And back to the students’ questions. This next question is how many parasites can be in people at once?
Bill:
Well, that’s a good question. And I don’t think there’s any limit to the number of parasites that could theoretically, you know, infect you just because you have one parasite inside you doesn’t mean you can’t get another one. So you were saying, you know, you, you know, if you get giardia, for example, can you also get another parasite?
Absolutely. Yes. You, you can get many things from that same batch of contaminated water. Some people around the world fall prey to multiple parasites. So, if they drink dirty water, they could get Giardia, e-coli, an amoeba infection, intestinal worms, perhaps. And on top of that, if they get bit by a mosquito, they can get plasmodium on top of that.
So there’s no real limit to the number that can infect you and some parasites can indeed in fact, do more than once. Like we were just saying, for giardia, and the plasmodium parasites are really good example of that just because you get malaria. Let’s say as a young child doesn’t mean you can’t get it again, years later, or as an adult, we just don’t develop a robust immune response to it.
And that’s, that’s one of the things that’s been complicating, the development of a vaccine for malaria.
Victoria:
(What parasites are good for you? What kinds of parasites are bad for people?)
Hmm. Interesting. All right. And then this next question, what parasites are good for you? What kinds of parasites are bad for people?
Bill:
Well, by definition, a parasite is never good for you because they steal your resources and give nothing in return. They’re like the worst roommate you could ever have. Microbes that live on and inside us that can be helpful. For example, trillions of bacteria live in your intestines, and that might sound gross, but they’re friendly bacteria, which means they help us digest certain foods. Some of them even make vitamins. Some of them help our immune responses, but we don’t consider them parasites because they do good things for us.
Victoria:
Okay. That makes sense. Yeah. I definitely appreciate having those, all those trillions inside of my, my stomach and my intestines helping me digest. It’s always, you know, it’s like having helpers or something with you all the time.
Bill:
Yes it is. And that’s the difference between what we’re talking about today, parasitism versus something called, you know, symbiosis, which is where the two creatures get along together, you know, one hand washes the other, so to speak, scratch my back, I’ll scratch yours. We give these bacteria nutrients and a place to stay, but in return they make us vitamins. They help fight off other intestinal pathogens. They do good things for us. So it’s a, it’s a nice given, you know, give and take. They’re not parasites. They’re just all take take, take.
Victoria:
(What are the worst and best parasites?)
All right. And, I think you’ve kind of touched on this, especially with this last question, but the next question is: what are the worst and best parasites?
Bill:
Well, one of the worst, in my opinion is plasmodium. That’s the one that causes malaria. And I view it as one of the worst because so many people in the world get infected and the costs of battling that infection can keep entire nations in poverty. Collectively the parasites that cause diarrhea are also among the worst. Not only is diarrhea, no fun, but it can lead to dehydration and malnutrition, which can seriously damage the body and brain sometimes irreversibly.
Now, I don’t know if we can think of a best parasite, but I can tell you about one of the most successful ones. And it’s the one we study in my lab. The most it’s called toxoplasma gondii. I, this parasite, it’s a protozoa in a single cell. It’s infected around 3 billion people in the world, which is pretty amazing. When you think about it, how can so many people be infected and virtually no one’s ever heard of this parasite because it’s very sneaky. It actually sleeps in the brain and it’s not thought to cause disease unless that person has a bad immune system, toxoplasma rarely kills a person, but it will stay in their brain for the rest of their lives.
And there’s a few studies out there that correlates the presence of this parasite in the brain with behavioral changes in the animals that it infects. We most commonly, reproducibly see those in mice, whether it actually changes human behavior, there’s correlation studies, which means you can see associations, but there’s no real hard evidence that it occurs.
Victoria:
I’ve heard. And again, this isn’t one of the student’s questions, but I’ve heard that you can get it from cat waste, cat litter. Is that true?
Bill:
That is absolutely true. That’s one of the major routes of transmission. the cat is the only organism where the parasite can reproduce in its sexual stage. Okay. So that’s pretty unique. For the cousin parasite plasmodium, it uses the mosquito. Toxoplasma uses the cat. So, if we don’t, clean out the litter box, promptly and carefully, you can accidentally ingest the parasite eggs that come out of the cat. So, you do have to be careful about that. Especially women who are going to have a baby because toxoplasma can cross the placenta and cause damage, to the, to the growing infant inside. So that’s a major, that’s a, that’s a, that’s a problem with toxoplasma. Cats are not the only way you can get it though. You can also get toxoplasma from contaminated water or, under cooked food.
Victoria:
Oh, yikes.
Bill:
Yeah. Yikes.
Victoria:
Very good to know.
Bill:
t’s a great follow-up question because it also helps address why the parasite is so common. How in the world did this parasite get into 3 billion people? And it’s because it has so many different what we call routes of transmission. It has so many different ways to get into people and infect them, but you won’t even know you got infected. It doesn’t cause major symptoms. It just goes up to the brain and hangs out there for the rest, presumably, the rest of your life.
Victoria:
So would you say that if, you know, like if you have a cat, you probably have it or would you only get it if you didn’t handle the litter properly?
Bill:
Yeah, that’s a great question. And, I don’t think people who own cats need to be overly concerned, especially if they’re taking it. You know, if they’re cleaning the litter box promptly and carefully and washing their hands after doing so household cats, probably don’t acquire the infection if they’re kept inside and you don’t give them rare or under cooked meat, because that’s how they can catch it too. You know, if your cat’s a hunter and goes outside and gets birds and mice, there’s a reasonable chance that they would have contracted toxoplasma. But we also need to keep in mind when a cat does become sick, the cat will shed these oocytes for about one or two weeks. And then it’s done and then the cat will never do that again. So, you’re talking about a fairly small window where the cat’s infected and potentially transmitting this disease. So some people claim that most of the toxoplasma infection might actually come from under cooked or raw meats.
Victoria:
Okay. That makes sense. Yeah. I’ve always wondered that because I, I love cats, you know, I’ve had cats for most of my life. So I was just always curious about that. Yeah.
Bill:
The danger is, you know, there is a danger, but I think with very simple, you know, care, you can really minimize the odds of transmission.
Victoria:
(How small can parasites get? What is the smallest parasite in? What is the biggest parasite?)
Okay. That’s good. That that’s very good to hear. All right. And we can switch back to the students’ questions rather than just my questions. These are some questions about size of parasites, so the students are wondering how small can parasites get? What is the smallest parasite in? What is the biggest parasite?
Bill:
Oh, yes. Very good question. The biggest parasites are the intestinal worms because they can, they can grow to large sizes. So, they’re one of the few parasites that are not actually microscopic all the time. Some of the intestinal worms can probably grow, as tall as you, you know, there’s been reports of three- and four-foot worms inside of the intestine. You can’t see most other parasites unless you have a microscope and viruses. You can’t even see viruses with traditional microscopes. We need to use an electron microscope in order to see a virus because they are so incredibly small.
Victoria:
Oh wow. Very diff big difference in size range of sizes.
Bill:
Absolutely.
Victoria:
(What is the most deadly?)
That is cool. And the next question, maybe you’ve mentioned this one already, I’m not sure. The students want to know: what is the most deadly?
Bill:
I would consider the brain eating amoeba, also known as naegleria to be one of the deadliest. Like I said, you can catch this by snorting up contaminated water, you know, up through your nose, usually in a warm lake or a pond. There’s no cure. And most people die in about a week after snorting, this parasite up. Because it travels, after you inhale it through the nose, it travels right up to the brain and, just like its name, it just starts eating away the brain. Sounds very ghoulish and, and, awful, so that’s why it’s definitely one of the worst. But I, I hasten to add, you shouldn’t have too many nightmares about it because it’s extremely rare to catch. There’s only been 150 cases in the U S since the 1960s, but everyone who caught it virtually everyone has died from it. There’s only been three or four survivors that I know of.
Victoria:
Yikes. Did the survivors have like lasting brain damage or were they able to recover completely?
Bill:
I believe most of them made a pretty full recovery.
Victoria:
Oh, that’s good.
Bill:
So they must they’re, they, we really don’t know why we don’t know what is special about these people that allowed them to, avoid, the, this lethal infection, probably something in their genetics or immune system that squashed the parasite before it had a chance to do too much damage.
Victoria:
(Why are tapeworms and roundworms so gross?)
Okay. Yikes. All right. And then this is a, sort of fun opinion question. Why are tapeworms and roundworms so gross?
Bill:
Yeah, I guess most people would think of them as gross. certainly no one, I don’t know too many people, you know, who admire them and hang pictures of them on the wall. I know a few people who might do that, but that’s because they study them. So we, we probably consider tapeworms and roundworms to be gross because, while they’re creepy looking, and we don’t want to imagine something like that crawling through our body inside of our intestines. It really gives us the willies. We evolved a strong disgust response that keeps us away from things that transmit poisons or parasites. This is why poop and spoiled food smells so bad to us. It’s the body’s way of saying stay away.
Victoria:
Oh, that makes sense. Yeah. I never want to go close to something or, you know, eat something that smells bad.
Bill:
That’s right. And that’s, that’s because we evolved in aversion to those smells because it doesn’t do the body.
Victoria:
(Are parasites able to become more deadly just by infecting more people? If so, somehow can parasites become more deadly inside of someone?)
Good. Yeah. And this next question from the students: are parasites able to become more deadly just by infecting more people? If so, somehow can parasites become more deadly inside of someone?
Bill:
Viruses are not really considered to be alive until they infect someone. Then they can become very dangerous. The same can go for fungal spores. They are harmless in the air. But if inhaled could start growing and then cause an infection. These germs can be more dangerous and people who are immuno-compromised, which means their, their immune system is weak. They can’t fight them off as well as the average person. Now parasites, including viruses can also potentially become deadlier if they mutate. A mutation is when their DNA or RNA changes. And it produces a slightly different version of the virus than what it used to be. Now, the mutated parasite or virus might grow faster, or it might spread more easily from one person to the other, or could become resistant to our vaccines or medicines. And those are what give us the most concern.
Victoria:
Yikes. And we are recording this at the end of February when we are hearing a lot about mutations in the coronavirus and COVID-19. So is that, you know, is that what scientists are trying to figure out right now, how those mutations are affecting the virus and changing its behavior?
Bill:
That’s right. We’re keeping a very close eye on these mutations that are arising. This is not unexpected. This is what viruses and other germs do — they fight back, you know? So, we’re keeping a close eye on those variations. Fortunately, none of the ones that have come up yet seem to be resistant to the vaccines that are currently developed. Nut that remains a possibility, a new variation could form that becomes resistant to the vaccine. And we don’t really know the likelihood of that. But what we do know is that the way to stop it is to vaccinate people because viruses need to reproduce inside of a person inside of their cells in order to make more viruses and mutations arise, the more viruses that are made. So the more virus that is out there reproducing in people, the higher, the probability that mutations are going to arise. So, what we’ve, we’ve all got to work very hard, in keeping the social distancing and forced minimizing transmission of the virus. Getting as many people vaccinated as quickly as possible.T hat way the virus has fewer places to grow and therefore fewer opportunities to mutate.
Victoria:
(Is the coronavirus a parasite?)
That makes sense. All right. And this is, I didn’t even realize this is a good follow-up question that, was right up here in our list: is the coronavirus a parasite?
Bill:
I alluded to this a little bit in the beginning, but I can clarify it a little more. You know, scientists tend to be very precise, very exact with their definitions. So to most scientists, viruses or viruses, even though they act like parasites.
Victoria:
(Are scientists working on vaccines for the deadly parasites? And are there medicines that get rid of parasites?)
We’ve talked about vaccines a little bit, and so now we’ve got a question about, you know, vaccines for parasites and some treatments, series of questions about treatments coming up. The first one: are scientists working on vaccines for the deadly parasites? And are there medicines that get rid of parasites?
Bill:
Yes. I am always excited to talk about vaccines and developing new medicines. These are things that my lab does, and these are, these are things that we’ve been trying to do for the past 20 years. It’s very hard work, but we’re always engaged in research to develop new vaccines and medications to fight off these parasites, to help people. We’ve had many success stories, the vaccines for smallpox and polio, for example. Diseases you might’ve never heard of, but for most of human existence, these diseases were major problems. Thanks to the power of vaccines, we’ve virtually eliminated those two diseases from earth. We now have vaccines for coronavirus. Like we said, we have fantastic medicines, like antibiotics that can treat bacterial infections. And we have medicines against certain parasites, like giardia. And malaria. We also have good medicines to help get rid of intestinal worms. We do not however, have good medicine for parasites that affect mostly the people who live in poverty. We need more vaccines and research to treat, malaria, to treat Chagas disease, to treat another one called leishmaniasis, which is a major problem in the tropical areas of the world, sleeping sickness and brain eating amoeba. We really don’t have a lot of good medical treatments. We have some, but not too many. And they, these parasites are evolving resistance to the few drugs that we have. So, the future doesn’t look too bright unless we engage in more research.
The problem is people who live in impoverished areas can’t pay for that research. So, so the foot, in order to foot the bill, we have to get, other countries to pitch in, and, and pay for that research to save, you know, the people in the impoverished countries.
Victoria:
Yeah. Yikes.
Bill:
It’s a really sad situation because a lot of, one of the major reasons those countries remain impoverished is because they spend all their resources and money trying to fight these diseases. So, they’re stuck in this horrible cycle. That’s very difficult to escape from.
Victoria:
Yeah. Does the WHO help with, with things like that?
Bill:
They, they do. The World Health Organization as part of their mission is trying to eradicate these diseases in impoverished nations. They’ve had some remarkable success stories. The, the Guinea worm is, is one of the other, it’s not one of these intestinal parasites, but, I think you get it from contaminated water, burrows into the skin and starts to grow and you literally have to pull the worm out over time. It’s very painful, very disgusting. But Jimmy Carter led an effort, in order to eradicate the Guinea worm, utilizing not necessarily, you know, new medicines, but just education, telling people about it, telling people how to clean, clean water. And, he’s made remarkable strides in getting rid of the Guinea worm, in many places around the world. So it’s, the answer is not always vaccines and medicines. They certainly help. We should certainly try to do them, but a lot of times it’s just giving people basic things like clean water and uncontaminated food and the education that certain insects can transmit a disease to you. Or we can do things like bed nets, those, have a really good track record of minimizing, mosquito, born diseases like malaria.
Victoria:
Wow.
Bill:
It’s a real multi-pronged, solution. And I think all of those options need to be explored if we’re going to get a handle on this problem.
Victoria:
(Can parasites come out with no medicines?)
Yeah. Yeah. That makes sense. Come at it with as many aspects of a solution as possible. And this is a good follow-up to that speaking of medicines and treatments. Can parasites come out with no medicines?
Bill:
Yes. In some cases, your body can fight off parasites just fine. It might not be a pleasant experience, but, but you’ll get over them. We already mentioned Giardia. That’s, that’s one that your body can fight off on its own. Usually. You also recover from many viruses, on your own, like the common cold, or back in my day, when I was growing up, I had chickenpox, it was miserable, but I got over it. Our body is also equipped with an awesome immune system. But sometimes it needs a little help. I would never want my own children to have to go through chicken box. So thankfully now we have a vaccine, and they will never have to suffer through that infection because of it.
Victoria:
(Can you become immune to a parasite without getting it?)
That’s good. And a good follow-up to that: can you become immune to a parasite without getting it?
Bill:
Yeah. Again, through the power of vaccines, vaccines are amazing. I can’t say enough good things about them. They show your immune system a tiny piece of the germ so it knows how to defeat it if it ever tries to attack you. It’s kind of like when the Rebel Alliance in Star Wars saw the plans for the Death Star, it gave them the information they needed to destroy it.
Victoria:
(Can parasites, kill animals? Can parasites affect plants? Are there any animals that are immune to parasites?)
I love that analogy. That’s fantastic. All right. And we’ve got some questions coming up here about parasites affecting other animals. So this first set of questions, the students are wondering can parasites, kill animals? Can parasites affect plants? Are there any animals that are immune to parasites?
Bill:
There are parasites for every living creature plant or animal, even parasites can have parasites. No animal is immune from all the parasites out there.
Victoria:
Wow. All right. And then two, specific questions. How many parasites can a cat get? And can goats get parasites?
Bill:
Certainly sensing a lot of cat fans in this classroom and that’s just fine. All animals get multiple parasites. The cat is no exception. We’ve already mentioned that cats can get toxoplasma. In fact, any animal can get toxoplasma. It’s even been found in beluga whales, believe it or not.
Victoria:
Wow.
Bill:
And cats can also get worms. That’s another common one, especially in our pets, but we usually have veterinarians who can give medications to prevent worm infections, ticks, and fleas. So it’s important to use those collars, in order to prevent your cat or your dog as well from getting those ecto-parasites. Now goats also get parasites. The most common one, probably being worms that invade and grow in their intestines. Goats can also get a worm that grows in their lungs, which can also be, quite nasty.
Victoria:
(What’s the oldest parasite that we know did dinosaurs have parasites?)
Yikes. Good to know. All right. And then a question about other animals with parasites. What’s the oldest parasite that we know did dinosaurs have parasites?
Bill:
That’s a great question. And we’re still investigating the answer. We don’t know what the oldest parasite is, but that style of life has probably been around since the beginning of life. So, to us taking things without asking for them and giving nothing in return is kind of a form of cheating and it’s bad, but this strategy works really well for parasites. Now regarding dinosaurs, believe it or not, fossilized bones and even dinosaur poop tell us that dinosaur is most likely had to deal with a number of different parasites. So even, even back in their day, parasites were certainly around. The one that scientists have pretty good data that dinosaurs were afflicted with, include worms again, and amoebas. They probably had to deal with other ones too. There’s a type of plasmodium parasite, a type of malaria, that is specific to reptiles. So I imagine, dinosaurs were susceptible to certain forms of malaria as well.
Victoria:
Wow. That’s amazing to think, you know, the biggest creatures that have ever walked on earth getting, getting parasites too. So if you have a parasite, you’re just like a dinosaur.
Bill:
I always start off my parasite classes with a quote from Yoda, you can tell I’m a big Star Wars fan, you don’t judge these by their size. You know, just like Yoda more. These are tiny creatures, some of them microscopic, but they can bring down even a huge dinosaur. So you, you, we can’t ever underestimate, the germs that live amongst us.
Victoria:
(Can parasites get a parasite? Can parasites of parasites get a parasite? Is there a limit to parasites getting parasites, getting parasites and so on?)
Wow. All right. And speaking of, you know, what lives, the germs that live amongst us, this is a set of, interesting and fun questions. And I think you hinted at this for one of the other answers. Can parasites get a parasite? Can parasites of parasites get a parasite? Is there a limit to parasites getting parasites, getting parasites and so on?
Bill:
Fascinating question. And the answer is yes. Like I alluded to before, some bacteria, for example, they, they, they can be considered to be parasites. If they’re pathogens, bacteria can be invaded by specific types of viruses called phages. So, since phage viruses only attack bacteria and not humans, scientists have actually channeled, developed phages that can attack bacteria that make us sick. So, the fact that you can have a parasite in a parasite might actually be a good thing in this case, because we might be able to use that against certain pathogens. Ecto-parasites, like fleas and ticks can also be infected with parasites and sometimes give them to us like when a tick, a parasite bites us, it can give us another parasite that can lead to Lyme disease. We don’t know the limits. In theory, anything that is alive, including a parasite can become parasitized.
Victoria:
(Is there a parasite that comes from a fish?)
Wow. Interesting. All right. Now we’ve got a couple of questions here that the students are wondering about parasites that come from certain places. So this first one is, is there a parasite that comes from a fish?
Bill:
There sure is. As with any food not cooked properly, we can get food poisoning from bacteria that was on the food. And that’s going to cause upset stomach and diarrhea. Sometimes death. Uncooked fish can also give you intestinal worms too, mostly of a tapeworm and roundworm variety.
Victoria:
Yikes. And is that, could that come from sushi or is that, is, does freezing the sushi, or like the raw fish that goes into sushi, does that kill the parasite? When it’s flash frozen?
Bill:
Raw foods have an inherent danger, but most professional places who serve them, particularly sushi restaurants take tremendous care in keeping those, those types of foods that are going to be served raw clean and cold. As you alluded to, the cold temperatures are freezing, no parasite is going to grow under those conditions. So, you can, and that’s why we refrigerate our foods too, to prolong their life because, that way, whatever microbes might be on them, they really don’t grow very well in the cold. And they usually don’t grow at all if they’re frozen. So, so yeah, proper storage and handling techniques are critical. If you are going to be serving raw foods like sushi.
Victoria:
(Can parasites come from your breath?)
Okay. That makes sense. Good to know. This next question of where parasites can come from. Can parasites come from your breath?
Bill:
Viruses can be transmitted through the air. But they usually need to be coughed out or sneezed out a little more forcibly, you know, than just talking or whispering or, or breathing. It has been shown in some cases that shouting or singing or talking loudly is sufficient to propel some viruses into the air and then other people might be able to breathe them in. And this is precisely why, scientists and doctors are asking people to wear masks to help stop COVID from spreading.
Victoria:
(What is the limit of parasites you can get before dying?)
That makes sense. This next question is what is the limit of parasites you can get before dying?
Bill:
Yeah, I would say there’s no limit to the number of parasites you can get. The good news is that we know how to prevent catching most of them. And we use sanitizer. We avoid sick people. We cook our food properly, don’t drink dirty water. And we wash our hands after we use the bathroom or pet animals, and we have those vaccines and medicines that help the body fight them off.
Victoria:
(If a parasite is inside of us, when we die, will the parasite die with us?)
That’s good to know. Good to know that we can prevent things. All right. And then this is another, interesting question about, about parasites causing death. If a parasite is inside of us, when we die, will the parasite die with us?
Bill:
That’s a really good question. The parasite needs life in order to live. So, if you die, then most likely that parasite is gonna die with you. The one exception that I can think of is. If you’re eaten by a bear or something, then the parasite might move on to infect the bear or whatever eight years.
Victoria:
(What inspired you to study parasites?)
Okay. That makes sense. All right. And now we’ve got a couple questions, a few questions to end us off about you and your study of parasites. So, this first question in that category, what inspired you to study parasites?
Bill:
I became fascinated by them when I saw them squirming around under the microscope for the first time. And like I said, the main one I study is toxoplasma and the parasite we get from the cat litter box or contaminated food and water, I found it amazing that something so small could cause so much trouble and make so many people sick or even die. I wanted to do something about that. So I dedicated my life to trying to develop new ways to prevent and cure parasites so people wouldn’t get sick.
Victoria:
(Have you ever had a parasite?)
Awesome. This is an interesting question. Have you ever had a parasite?
Bill:
Yeah. Good question. I’ve had ticks, I’ve had viral infections. I’ve had bacterial infections, but none of the classic parasites that I’m aware of. I had a cousin who got intestinal worms once when she was a kid, probably from under cooked pork. But she was fine after taking medicine.
Victoria:
(How do you study parasites? Do you dissect them?)
Oh man. All right. And this is our last question. How do you study parasites? Do you dissect them?
Bill:
Well, we have to use microscopes in order to see them. We use lots of different methods to study the parasites. We grow them in the lab using special flasks and liquid that they need to grow. And since many parasites infect cells, we first have to grow those cells in a dish. And then we put the parasites on top of them and let them infect them and grow them that way. Now we don’t dissect them in the traditional sense that we have scalpels and razors that can, you know, slice them open and look inside. They’re just too small for that sort of thing. So the way we have to dissect them is through genetics. We can add or remove genes from the parasite to learn what that gene does and whether it’s needed for the parasite to live or reproduce. If the parasite needs that gene in order to live. We can then develop medicines that target the gene. And that’s the, the main approach that we use in my lab.
Victoria:
Wow. That is cool. And that’s all of our listener questions, but I do have one more question for you and that is, do you have any questions of your own to ask the listeners?
Bill:
Yeah, I don’t know. You got me got me in the spot on that one. I would just love to hear what people learn today. And if they think about the world in a slightly different way, we talked a lot about living creatures that affect us in very big ways, but we can’t even see them. And I’m just wondering if that changes, how, students look at the world and, and what is their outlook, knowing that there are things that we can’t see that can affect us so greatly.
Victoria:
That is a great question. I know it’s definitely made me think and, you know, change my outlook on the world a little bit. So, I’d be curious to hear the answer to that question too. And do you have a professional social media account that the students can get in touch with you?
Bill:
I do. I have. They can contact me through my website, which is http://www.authorbillsullivan.com. There’s a contact link there as well as links to all my social media channels. But the one I use the most is Twitter. I don’t know if too many students of this age are on Twitter, but that’s at @wjsullivan, S U L L I V A N.
Victoria:
Awesome. I’ll put links to your website and links to your Twitter in the episode description, so they can go ahead and just click on that, to get to your website and your Twitter.
Bill:
Super that’ll be great.
Victoria:
Awesome. Well, that’s all of our questions. Thank you so much for doing this. This was fascinating. I feel like I could sit here and ask you parasite questions all day.
Bill:
And I could answer them all day, to be honest with you. I tried so hard to limit some of these answers because I knew I could go on and on and on.
Victoria:
Thank you so much for joining us on Ask A Scientist. I hope you learned something and enjoyed meeting Dr. Sullivan. If you have something you would like to ask a scientist, you can send in your questions to askascientistpod@gmail.com. You can also submit questions and follow the podcast on social media. Twitter @_askascientist. Instagram @askascientistpod, and Facebook @askascientistpod. And check out the website, askascientistpod.com. If you’ve enjoyed the podcast, please share it with your friends and family and go on apple podcasts and give us a five-star rating and a positive review. It really helps us to reach a broader audience.
If you would like to contribute financially to the production of the podcast, you can support it on Patrion. Thanks Dr. Sullivan for talking to us today and thanks to the students in Mr. R’s fourth grade class at Bromwell elementary for writing the questions that we asked.
And don’t forget to check out Dr. Sullivan’s book, Pleased to Meet Me: Genes, Germs, and the Curious Forces That Make Us Who We Are.
Thank you to anchor for hosting the podcast and special. Thanks to Webberized for making this podcast possible. And thank you to production assistant Wanyue Wang for doing the episode transcription and the links to more information that’s available on our website. The theme music was written and performed by Joe crystal. Thanks for listening!
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