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TWiP 29 Letters

Dylan writes:

Dear Professors Racaniello and Depommier,

I hope this email finds you both in good health. I am a second year medical student from Ireland studying at the University of Cambridge, UK and I have been following the TWiP series with considerable interest. Please allow me to compliment the marvellous work you both are doing for science communication, which I am certain will help inspire both researchers and clinicians alike as well as the general public to learn more about infectious diseases. If I may, I would like to request that an episode be devoted to the helminth, Schistosoma mansoni.

Wishing you the best of luck with all the podcasts,

Yours faithfully,


Clint writes:

Love your show.

Have you seen this

The news clip covers a Chemotherapy Drug that Also Kills the Parasite That Causes Malaria.

It may be a malaria breakthrough could you give us your thoughts.

Thanks Again for a great program.


Ryan writes:

Hey Guys,

Thought I'd follow up with you on my email you read on #24.

You asked which university I attended and who taught parasitology there. I attended a smaller to medium size school in Texas called Tarleton State University, where I studied Limnology. My parasitology professor's name was Dr. Russell Pfau. Most of his work is with genetics and currently based around the cotton rat (Sigmodon hispids).

I also thought I would tell you guys how I have put my parasitology classes to use, as it might interest Dickson.

After I graduated with my B.S. I started working at a state run fish hatchery, where we produce game fish and do a fair bit of aquaculture research. We produce striped bass, smallmouth bass, channel catfish, and rainbow trout that are stocked in public water bodies around the state for angling enjoyment. We do regular sampling of our fish for various parasites and bacterial infections, so I've kept my microbiology skills fresh over the last few years.

Our arch-nemesis, however, is a single cell algae: Prymnesium parvum (golden algae).

It is a common algae found in estuaries around the world, but wreaks havoc when introduced to inland waters. P. parvum was first identified in Texas in the mid-eighties, and has gone on to destroy fish populations in several of our drainage basins throughout the state. Since then, it has reared its head in many different states in the U.S. Much of our resources (and most of my time) are spent dealing with golden algae at our facility and providing assistance to private land owners who have experienced blooms on their property.While we have good controls for dealing with it on a small scale, there is currently no solution for treating on a large reservoir scale.

Here is a link to more info on our website if anyone is interested:

Thanks again, for the great podcast. Since finding TWiP, I've also added your other podcast to my weekly downloads. They're all great.

(semi-professional phycologist)

John writes:

This show has stimulated an interest in the subject in me, an unlikely candidate.

Thank you

Coincidentally my dog is currntly being treated for heart wrom.

If you ever need an alternative name for the show I have;

1) Hold my hand, I'm a stranger in parasitism

2) Parisitism lost - paristism found.

3) Another shitty day in parisitism.

I hereby assign all rights.

Keep up the good work.


Alberto writes:

Dear Vincent & Dickson

Thanks for your wonderful podcasts. I have recently subscribed to both TWiP and TWiV and am slowly working my way back through the back catalogue.

I am a diagnostic molecular biologist working in the haematology department of a major teaching hospital in Sydney, Australia. Our lab's main tasks are PCR detection of various mutations and gene rearrangements found in leukaemias. This year marks the 20th anniversary of the first official diagnostic PCR report issued by our lab, so we have been involved in the field from the early days

I was particularly interested in TWiP #23 re. Strongyloides stercoralis since it is relevant to my work in molecular diagnostic haematology. One of the diseases that our lab works with is chronic eosinophilic leukaemia (CEL), particularly the myeloid subtype that is characterised by the presence of PDGFRA and PDGFRB gene rearrangements; this subtype is particularly sensitive to kinase inhibitors such as imatinib. Curiously, these gene rearrangements are almost exclusively found in males and they do not involve the sex chromosomes.

(Note for your listeners: Eosinophils are white blood cells that form part of the innate immune system. They are full of toxic protein granules that are released to kill invading organisms. However, if these granules are released in the host's tissues in large quantities they can cause significant systemic toxicity. Commonly affected tissues in hypereosinophilia [eosinophil blood counts above 1.5x10^9 /litre] include the skin, heart, lungs & gastrointestinal tract. )

Therefore, it is very important that patients with eosinophilia are correctly diagnosed so that the clinician can determine if they are eligible to receive this very effective targeted therapy. CEL is very rare compared to reactive eosinophilias, including those caused by parasitic infections. Other idiopathic eosinophilias are treated with corticosteroids which suppress immunity.

In my CEL powerpoint that I have presented to clinical haematologists I have a couple of slides stressing the importance of screening patients by Strongyloides serology prior to commencing corticosteroid or kinase inhibitor treatment for eosinophilia. It was not until I heard TWiP#23 that I really understood how serious strongyloidiasis is and why it is so important to avoid it.

Having no background in parasitology and very little in immunology beyond undergraduate biology, I appreciate that Dickson instructs us in the correct pronunciation of the names of the organisms and diseases that you discuss.

I hope you guys continue to keep up the good work and that you mentor a new generation of podcasters who will produce other interesting podcasts. I only wish there was a podcast of equivalent content and production quality in molecular haematology. Thanks again and I look forward to hearing more from you both.




Molecular Haematology Lab, Institute of Haematology

Royal Prince Alfred Hospital


TWiP 28 Letters

Chris writes:

Dear Dick and Vincent,

I am a doctor of pharmacy and I have listened to all of your podcasts and have read many of your book suggestions (TWIV and TWIP). I thoroughly enjoy them and hang on every word of Dick's stories. I would like to say a few things. First may I point out the obvious flaw with your name; This WEEK in Parasitology, and yet we don't have it weekly. I feel that we need more shows just to catch up with all of Dick's anecdotes. You also mentioned the island of Ceylon changing to Madagascar but in fact it is now Sri Lanka. The USGS was formed in 1879 as a bill signed by president Rutherford Hayes and I can't seem to find anything in it's history that relates to the Rockefeller Foundation. As best as I can tell Thiabendazole is not available in the US or Canada and Mebendazole oral is the current treatment for hookworm. I hope this helps. Keep them coming.


P.S. Why not have a TWIP/TWIV app for your iphone? All of the contacts, emails, shownotes and shows and access to literature can be in one place. Just a thought.

Lars writes:

Hello Vincent Racaniello and Dick Despommier,

this is my second mail to the TWIV/TWIP team. Thanks for some more background information last time about the Plasmodium falciparum/Gorilla story.

By now I have listened to all TWIP podcasts more than once and have been able to listen to nearly all the TWIV podcasts. I can understand that with your schedule does not allow to have a TWIP and TWIV podcast every week and I think in this field it is better to have less podcasts but the ones that are there go really into the subject. I think with a weekly but much shorter version a lot of the public learning benefits are reduced. So it would be great to have these long TWIP and TWIV podcasts in future as well.

I am sure you have heard about the The Carter Center and its fight against Guinea worm. It would be great to have a podcast about the Guinea worm topic since its said that this will be the second disease (the first parasitic disease) to be eradicated. And the first disease eradicated without the use of a vaccine.

Greetings from Germany


Jim writes:


What a terrific cohesive and comprehensive approach to hookworms. Such a delicate handling of the political and social issues, too. You may receive some response from listeners upset about the civil war and slavery and southern lethargy, but hopefully it will be balanced by positive reactions.

I just finished an article about a visit to Biloxi, Mississippi, in an 1865 edition of Harpers Weekly Magazine that talked about the lethargy that infects not only locals but visitors, too, referring more to the weather, I suppose, than parasites. Even in the 60's while living in California folks would refer to the much slower pace of life and speach in the South that supposedly derived from culture and weather. Interesting idea that parasite-derived group actiivity or mores might lead to social changes that perpetuate it.

Thanks for a terrific netcast. Looking forward to the rest of the story.

Smithfield, VA

David writes:

Love the show....

This delightful book has a section that is germane to your show and you might want to quote a few lines and discuss.

It details the occupation of Tongue examiner of pigs who would look for signs of parasite infection and sometimes cover it up.

Also....I have been a victim of Giardia three times as I was outdoor type of fellow who had a dog I traveled with extensively.

I got the classic symptoms each time: Painful abdomen often after eating, foul smelling stools that persisted, changes in stools consistency and color and it lasts until some form of treatment
Round one cured by Flagyl aka Metronidazole

Round two cured by Wheat Germ and I mean cured followed by Flagyl

Round three cured by Wheat Germ alone.

some research is here

here is a health page recommendation

scroll down for wheat germ



Jeannine writes:


I was a fellow graduate student at Notre Dame, graduating in 1970. I remember your discussions on parasites in the break room with pleasure. Your name keeps popping up everywhere, most recently on the TWIV netcast I receive, I suppose, as a member of the ASV. So I just wanted to say 'hello'.

Following a post-doc at the University of Chicago I had the good fortune to be hired as a grants manager by the Office of Naval Research in Chicago, where I lived at the time. I was hired at the recommendation of Morris Pollard, a friend of my soon-to-be boss. I went on to be transferred in 1982 to ONR Headquarters in Arlington, VA, where I still reside. I retired, sort of, in 2002. My 30 years in government work proved to be a delightful continuation of graduate school, as I site-visited hundreds of scientists most eager to discuss their research in areas ranging from shark behavior to fluid resuscitation of hemorrhage. I probably attended at least 200 conferences during my career as well. As a parting shot, so to speak, I fielded a battlefield hemorrage treatment used by the Marines in Iraq. During most of my government career I conducted part-time research in virology as a visiting professor at Loyola Med. School in Chicago, Uniformed Services University in Bethesda, University of Tennessee and Washington State University. My primary objective has been to understand how viruses make you sick--a field of minimal interest to virologists I must conclude following many hostile letters from journal editors. I have recently completed my work at WSU and plan to write a few more articles and then read books unrelated to virology! Three of my most recent articles are attached.

I am pleased that another student of Notre Dame has had a rewarding career.

Best wishes to you and your family,

Laura writes:

I am currently studying Zoology at university and starting a masters degree in Molecular parasitology and vector biology in september. I have recently seen a story on monsters inside me (its on the discovery channel) about a fireman who became infected with Ballamuthia an amoeba where there have only been a few cases in humans. Would you be able to tell us more about opportunistic amoeba?

TWiP 27 Letters

Jim writes:

Vince and Dickson,

You both have probably seen this already, but for TWIP and TWIM listeners fighting malaria with transgenic fungi is the first item in the 41 minute podcast for 25 Feb 2011, from . This sounds both fascinating as another means of dealing with animal and plant pathogens, and frightening from my understanding that fungi, at least as a human pathogen, are difficult to control. Could such fungi be transferred to humans and how can that be tested? Here's a hard copy source, too:

I think that podcast also talks about a new palm-sized NMR device! Man, it just keeps getting better and better...

On a totally different subject. Vince, you went through Weed, California some months back and I see you were just up in Washington state. As a kid I lived a few miles south of Weed, in the logging town of Mt Shasta (next to the mountain) as well as in a railroad town of Dunsmuir a few more miles south. You can also see Black Butte just north of the town of Mt Shasta along the interstate. Black Butte is a cinder cone about 2000 ft high with a path on the back side that's visible with Google Earth, that used to lead to a US Forest Service fire watch station that was continuously manned. I think it took us kids a couple hours to climb the path. If you get back that way in the summer, have the time and want the exercise, the climb up Black Butte would be a pleasant adventure. Mind the altitude, though. The starting point is about 4,000 ft.

For Dickson, a couple miles west of Mt Shasta up in the Cascades is a small mountain lake (almost a pond), maybe 20 acres in size with 2-foot-long rainbow trout that appeared to float in mid-air, the water was so clear. The lake only supported a few of these beauties and they were impossible to catch. The lake name, which you can locate with Google Earth, was either Porcupine or Toad Lake. Porcupine seems to be the one, but I don't see any logging roads to it as appear to exist for Toad Lake and the one with the fish could be reached by road, while you had to walk to the other. That was 50 years back, though.

There's a web cam for Mt Shasta, with several days worth of time lapse viewing that I look at. The same site provides temperature data. It was interesting as a kid to have a mountain in your back yard.

Smithfield, VA

Eric writes:

Dear Vincent and Dickson:

Thanks for reading my email. The "sync" trick I referred to was the synchronous mouse infection that Dickson describes at 15:20 into twip #5.

It's wonderful that Dickson shares this with the new researchers coming up. It's a bit like a magic trick - difficult at first to see how it's done, but much easier once you know the technique.

In rooting out computer bugs, if you can repeat the problem, you can always find its cause. The sync trick is like repeating the problem many times in parallel, so you only need to run the experiment one time. And if you have to destroy a cell to see what stage its at, you have many others still running at the same pace. Love it!



Jim writes:

This is for Dick, again, in the infomatics realm: just in case you've not kept up with the different presentations, .
I love these things.

Smithfield, VA

Sorry Dick, but I should have used the link rather than one that showed a couple of his TED presentations dealing with statistics.

Stephen writes:

Dear TWIP,

Isaac Asimov was a biochemist, not a physicist as mentioned in episode 23.

He did write many "Popular Science" books explaining physics and astronomy (I have 3 or 4 of those), so it is an easy mistake to make.

- Stephen

Judi writes:

Hello Drs R and D,

Thanks for the great podcast - I learn science, history, and a bit of politics from you and love the unexpected connections you make (Abe should have given a medal to the hookworm as the supreme undercover agent!)

I am a high school teacher and I try to teach my students to think about things - and one of the things I've been pushing is that virtually every decision or action has a potential positive and a potential negative - you weigh both sides to make your decision.

In that vein, i have to ask the other side. When you talk about parasites, you talk about them in relation to human disease, and , rightly so, the goal is to rid the world of them to protect people. My question - do they have no other function in the larger ecosystem? Can we rid the world of onchocerca - or hookworm or malaria for that matter - and have no effect on the larger ecosystem?

If these are truly a single food chain, rather than being part of a food web, I will use them in class as an example. Right now I tell kids that almost all organisms are part of a food web and so we need to look carefully before to bulldoze or plow or pave or overfish.

Thanks for keeping me learning and interested - and for the best professional development I have ever gotten! I strive to teach as well as the two of you...

San Diego, CA

Raphael writes:

I've been doing some transcribing in my free time on your TWiP's "Hookworm" episode for my blog site and it seems that Dr. Dick made an error on mentioning the term "hematuria" for the dark-brown colored stools found in patients with intestinal bleeding. "Hematuria" is meant for blood in the urine. What Dr. Dick was supposed to mean was "melena," and contrasting this to the word "hematochezia" for the bright-red stools (undigested, fresh blood).

If you're interested to note the error, it's around 39 mins and 55 secs of the recording time.

The Learning Blog

TWiP 26 Letters

Jim writes:

Prof Dickson,

Does the same concern that you discussed with suppressed immunity after a transplant apply to folks who undergo chemotherapy for cancer? (re strongyloides)

Smithfield, VA

Spencer writes:

Hi Vincent and Dick,

On your Strongyloides episode, you spoke about final eradication of organisms such as polio virus. It was Dick's contention that the virus could be "reconstructed" from synthesizing the DNA, whose sequence is known. Are there any instances that you are aware of where a a full virus or other living organism (yes I know, viruses may not be living) were constructed in this way such that they could go on to have a normal life cycle and replicate? In other words, is just the creation of the DNA sequence sufficient for recreation for a virus?

As alway, thanks for making my day when I see that email announcement of a new episode.

Spencer MD PhD

TWiP 25 Letters

Casey writes:


I would like to thank you for the excellent podcasts regarding parasites and viruses. Although I must say, I think TWiP is more enjoyable than TWiV. I graduated with a bachelor's degree in Microbiology and a bachelor's degree in Clinical Laboratory Science from the University of Iowa, ultimately becoming board certified in Medical Laboratory Science with the American Society for Clinical Pathology (ASCP). I am currently working as a Clinical Microbiologist at a 500 bed hospital that just recently got rid of the parasitology laboratory.

Unfortunately, I wish the United States put more emphasis on parasitology as it does in the other areas of medical microbiology. While I was a microbiology major, the Department of Microbiology never offered a course in parasitology. In addition, as a CLS major, we were only given a 3 day lecture on parasites, which was really just brushed aside. Your podcasts continue to increase my interest in parasites pushing me to buy many books on the subject to add to my already growing microbiology library. I must admit though, I have not bought the book by Dr. Despommier yet. I can easily relate to some of the patient cases as I was recently infected with two parasites (giardia and E. histolytica) while I was in small villages in Vietnam and Cambodia.

I was just admitted to the University of Texas Medical Branch as a PhD student in the Biomedical Sciences Program, with an emphasis in Experimental Pathology. During my interview, they found it interesting that I mentioned parasitology as an area of research interest.

I do not know if you have mentioned it in previous TWiV or TWiP podcasts, but I would like to inform you of the Infectious Wearables website, I have bought several infectious disease ties from this website, which are always a conversation starter at family and professional gatherings.

Thank you and keep up the excellent work,


Suzanne writes:

I'm learning so much about history today! :) Just before TWiP I was listening to a podcast about Scotland and Ireland and the Scotch/Irish
who'd moved to the American colonies a couple hundred years ago. I'd known that one of the most hated British regiments had burned churches in the South and that was partly why they lost the favor of the royalists there at the beginning of the Revolutionary War. I learned
today that they were burning Presbyterian churches because the Presbyterian ministers were wandering the land trying to gather support for the Revolution.

Not that that has anything to do with your podcast :) Other than I was also interested to learn the role of hookworm in the South after the
Civil War. The South was pretty screwed up economically to begin with. There really wasn't great wealth by that point, just a few people who
were very wealthy. At the end of the war the few landowners who'd had enough land to make money left. Even before the war there was a lot of unemployment because of slavery and slavery itself wasn't nearly as economical as the landowners tried to convince themselves. Except in
the few cases where someone had enough land to profit on a small margin. Kind of like farming today. It wasn't just the machines in the
north that made businesses more profitable. Even small northern farmers were more profitable because they could hire fewer freemen who
would actually be interested in doing the work without the payment of a foreman to beat it out of them. Thomas Jefferson even wrote about
the problems created by slavery long before the Civil War. Frederick Law Olmsted (yeah! the park designer!) has an interesting book (The
Cotton Kingdom) he wrote after traveling through the South just before the war. I expect hookworm was the final nail in the coffin. Very
interesting to find out!

Thanks for all your podcasts. They're all in my list of favorites!

I also meant to say it's been fun listening to further information about things I already know a lot about like hookworm, which my mom
always warned us about when I was a kid in the 70s in Texas, and pinworm, which I first learned about from friends with kids. Let me
tell, you, my friend were not happy to find out that most of our kids probably had pinworms! I did feel the need to tell them, though, since
it does happen occasionally that someone's kid gets enough of them to be an annoyance. The trick I learned from the email list of moms I
used to frequent was to peek at your kid's bottom while they sleep at night. Evidently you can see the adult females crawling out of the
kid's anus if you're... lucky?

Rich writes:

Dear Vincent and Dickson,

I can't resist. In TWiP 12 Dickson asserts that sea otters eat only abalone. This is incorrect. They eat all sorts of stuff:

I spent part of my youth watching these critters and they are not only fascinating and an important part of the ecology, but they are decidedly gourmets as well. The reason abalone loom so large on the human perception of sea otters is that the abalone fishermen blame the comeback from near extinction of the sea otters for the decline of the abalone industry. There is vigorous debate about whether the sea otters or the fishermen themselves are in fact responsible for the decline of the industry:

Keep up the good work.


Richard Condit
Department of Molecular Genetics & Microbiology
University of Florida
Gainesville, FL 32610

Joe writes:

Dr. Racaniello and Despommier,

I very much enjoy listening to your TWiP podcast since I recently discovered it on iTunes last month. I particularly find the clinical presentation information and patient anecdotes informative. I will be starting medical school in the fall and will be sure to keep this information in mind as I go through my training.

There was mention in your broadcasts on Trichinella spiralis about the lack of current research being conducted on this parasite. I'm not sure if you are already aware of this article, but I thought you would be pleased to know that in the March 2011 issue of Nature Genetics the genome of Trichinella spiralis has been has been drafted (Matreva et al. Nature Genetics 43(3): 228-235.

Keep up the excellent work!

Thank You, Joe

Godfried writes:

Dear Hosts,

Did you ever considered yourself as addictive substances?
Some weeks ago a friend of mine suggested twip and twiv and now i find myself listening to your podcasts too frequently. There's a huge trove of episodes that i'm overdosing on (with horrible clinical effects as well as collapse of my social networks).

Currently i'm doing an MSc in infectious disease and combining this with your podcasts.
Thanks a lot for your effort, it is seriously helpful and fun.

A had a note/question to Dr. Despommier. In an earlier episode the genome size/gene content of Trichinella was discusses and it was mentioned that it has more genes than C. elegans. Last week i saw a paper in pre-print in Nature Genetics that discusses the genome of Trichinella (The draft genome of the parasitic nematode Trichinella spiralis Nature Genetics 43, 228-235 (2011). It seems to have fewer genes than C. Elegans. I tried to work my way through the paper but it's dense and a lot of data (I failed). I wondered if Dr. Despommier, with his experience with this bug, could shine his light on this paper. I'm especially curious if the paper explains longstanding questions of Dr. Despommier regarding trichinella (that maybe the authors hadn't thought of). It must also be good news for him that "his" animal has been sequenced and that scientific research is continuing to be done on trichinella.

All the best,

TWiP 24 Letters

Betsy writes:

Dr.'s Racaniello and Despommier,

Hello! To start off like so many of the messages you receive thank you so much for this wonderful podcast! I'm a huge fan of both TWIP and TWIV and have listened to every episode to date in both. It's fantastic how you present all of the information in a conversational way that is understandable for such a diverse audience of listeners. You two, along with your cohorts on TWIV, continue to feed my interest and very very limited knowledge in the fields of parasitology and virology.

I am a medical and biological illustrator/animator who became very interested in the field of parasitology while working on my graduate thesis at the Johns Hopkins University School of Medicine. My preceptor, Dr. Rhoel R. Dinglasan, an associate professor at the Johns Hopkins School of Public Health (JHSPH), who besides being incredibly intelligent and enthusiastic, sparked my fascination with the malaria parasites, and the field in general. And thanks to you I can continue to stay up to date and expand my knowledge in this field.

That being said I thought you might enjoy the new issue of the JHSPH magazine. It's all about malaria! I really enjoyed articles and reading about what research is being done and also why some of the researchers focus on various aspects of combating this disease, such as control vs. eradication. Plus there is the main illustration that beautifully depicts the life cycle of the malarial parasite that was created by an incredible medical illustrator Jennifer E. Fairman. There is an interactive version of this illustration on the magazine site too. To view this issue please follow the link below:

I thought that you would enjoy this illustration too as you have mentioned aspects of my field on both your podcasts in the past. Specifically you have commented on molecular animations by David Bolinsky of XVIVO who is at the top of the field in this area. You might already know about this but in case you do not, the web site showcases some of the most beautiful molecular animations out there. This site has a two-part animation by another amazing medical animator, Drew Berry, on the life cycle of the malarial parasite. Don't despair Dr. Racaniello there are many animations on there about viruses there too!

Again thank you for putting all of the time and effort that it must take to prepare and deliver such a fantastic podcast! I'm looking forward to all of your future episodes!



P.S. In appreciation for your sharing of knowledge and enthusiasm for science I've attached an illustration of mine for you of the malaria life cycle with in the mosquito. I know it's not enough to repay you for your generous service but it's a start.

Weissbrod Studios

Helen writes:

I am a med tech and a member of a group of people with immune diseases who is interested in helminithic therapy. We listened with great interest to the TWIP on Trichuris trichiura, which some of us are already using. I wanted to ask you when you will be covering hookworm, and if you could discuss the therapeutic benefits of Necator americanus, which some of us are also using. I liked the Trichuris podcast so much I am going back and listening to all the old episodes. I am interested in how trichinella could be used therapeutically. I believe you said that if the larvae are injected directly into skeletal muscle, they would immediately infect the muscle cells. Would this mean that by bypassing the migration phase, the infection would not cause pathology?

I have a family member with eosinophilic esophagitis, which is a disease that fits the hygiene hypothesis perfectly: sudden recent increase in incidence, atopic disease, more common in children, and the eosinophilic response is supposed to fight off parasites. This is a horrible disease that causes much suffering and often leaves the person unable to tolerate any food, needing a feeding tube and elemental formula. Do you know anything about the incidence of this disease compared to the incidence of parasites worldwide?

Keep up the good work,

Rich writes:

Hi TWiP fellas,

I should be working but I'm procrastinating by writing you.

I'm finally hooked on TWiP. Great show. Sorry it took a while. Until now my taste in podcasts has been a bit narcissistic.

I know this is a family show, but I really need to know if tapeworms have sex. You keep talking about "eggs" but my sense is that these are not haploid nor are they zygotes, but rather multicellular larvae encased in a shell. Right?

So do tapeworms have a haploid phase? Are there sexes? Assuming there is a haploid phase, when, where and how during the life cycle does fertilization take place? If tapeworms are hermaphrodites, do they self-fertilize, or is there a chance to mix it up with other worms, or both?

Thanks and keep up the good work.


Richard Condit
Department of Molecular Genetics & Microbiology
University of Florida
Gainesville, FL

Laura writes:

Hiya im Laura from the UK, studying Zoology and wanting to comtinue onto an MSc in parasitology. I was wondering are there parasites of parasites? would microsporidia be a cadidate for this?

Ryan writes:


Just wanted to drop you guys a line and let you know I enjoyed the podcast. I found TWiP while actually looking for a podcast about photography, but gave it a listen anyways. I'll be downloading every episode from now on. Parasitology was my favorite class as a undergrad. Thanks for the work you do!


Todd writes:

Hey Docs!

I'm a computer programmer who listens to podcasts on my long commute. The highest science education that I've had was college Chemistry. As an Electrical Engineer the science classes we took tended to not be biology oriented, so while some of it is over my head, to say that I find biotech and molecular biology fascinating is an understatement.

On to my question: I was born in 1970 in southern Louisiana. My uncle had a horse and we (me, my Dad, my uncle) would scoop the manure out of the stall and put it into a pile on the side of the horse barn. Some months later, after the manure had been exposed to the weather and sun-dried, we'd scoop it into the wheelbarrow and put it, along with composted grass clippings, in the garden as we tilled the soil for planting. I was wondering what kind of worms and/or other parasites we might have been exposed to by using horse manure to fertilize our vegetable garden. If I'm understanding things correctly, I don't think there is any danger from worms lasting long enough to get into our veggies and infect
us, but what about direct contact when handling the sun-dried manure (shovels and gloves, but still "stuff" happens)? And is there really anything to fear other than worms? I am in good health, so I think the answer is probably no, I'm just learning for learning's sake.

P.S. Lately I've been listening to the FiB, TWiV, and TWiP podcasts to the point where I'm neglecting my techie podcasts. You guys are causing me to lose some of my geek creds :-)

Regards... Todd

TWiP 23 Letters

Eric writes:

Dear Vincent and Dickson:

I am retired (40 years in computers) and so I have lots of time to study
anything that interests me. It's good brain exercise and I simply loved
the 3 shows on Trichinella worms. What a fantastic job of explaining a
truly incredible piece of evolutionary 'design' - and the work of a
brilliant scientist who figured much of it out. Twip 3-5 is right up
there with Edward G. Robinson in Dr. Ehrlich's Magic Bullet. Following
along with the sketches etc. on the website was great. Vincent asked all
the right questions just as I got confused, which made it feel like I
was there one on one with Dick. I didn't feel I needed to have any
pre-knowledge. Simply a perfect presentation! Nothing like the biology
classes that bored me in high school.

My road to TWIP began by looking for interesting mp3s for my daily
walks. I found twit with Leo Laport. which led to futures in biotech
where one or both of you had been a guest.

Next was twiv which fascinated me because the study of viruses and all
that DNA and RNA stuff was so reminiscent of when I would solve computer
problems by getting out the machine code debugger. None of the younger
guys know that old stuff anymore (they're all 2 layers higher up). But,
just like in a virus, if you know the exact instruction that caused the
problem, you could walk your way back up to the higher level and find a
fix - i.e. intervene and cure the bug. Not always so simple, of
course, sometimes you had to be clever and think of ways to force the
bug out into the open or look at the preceding steps, but the idea seems
similar to the techniques Dick described, especially the "sync" trick he
used. That was a cool one.

For what it's worth, you guys would have made marvelous system geeks,
maybe working in some shop in Taiwan reverse engineering the latest
chips. After all, it seems that's what you're doing. You're working out
the APIs of life, without a manual by watching the ins and outs and
reading the machine code.

I can't help wondering why Dick didn't try to sell his idea in the
marketplace - the one about how to possibly cure diabetes described in
twip 4. Maybe some wealthy person with a child who has the disease might
become interested as a sponsor.

Well, now we have the internet and TWIP, so perhaps this is the best way
to reach out with your ideas. I hope someone takes the ball given the
tremendous lead you've given him or her and solves this problem. Maybe a
Craig Ventor researcher will hear your idea and code up a new bacteria
with some genes taken from Trichinella.

After all, just as computer tech is nearly all software today so it
seems biology has become a variant of IT (e.g. Ventor's Bacteria Shell).
I expect to see a Visual Biology program in the not too distant future -
just click and drag to insert a Sinusoid creating protein.

Regards, and thanks for the great brain exercises!


Jim writes:

Dear Professors, thank you very much for your fine podcasts. I'm a physicist, about the age of Dr. Racaniello, but my career since graduate school has been in public policy, not academia. Since I never took the time to study parasitology, your conversations are new and often astonishing to me - the world is truly wondrous.

And my two questions: First, in your (fairly) recent podcast on pinworms, Professor Despommier explained that each mammalian species seems to have their own pinworm. Do the other mammals also show a clearing of their pinworm parasites at a time analogous to puberty? Or is that an unusual characteristic of our human-pinworm relationship?

Second, a broader question suggested by an odd - to me - phenomenon in insect parasitism: As you probably know, parasitic relationships among insects are quite common. The most familiar are various small wasps (hymenoptera) that parasitize the caterpillars of moths or butterflies (lepidoptera), and which are often useful in controlling lepidoptera pests. The United States often searches for such a native parasite of newly introduced, economically damaging moths, and introduces them to control the moths

In some cases though, even the right parasitic wasp, effective in its native range, doesn't effectively control a new, invasive species of moth in a new region. Hyperparasitism is quite common in these insects - there are yet more species of parasitic wasps which parasitize a range of other wasps parasitizing the caterpillars in a region. They search out the eggs or larvae of the wasps laid in or on a caterpillar, and the hyperparasitizing wasps then infect those eggs or larvae. This can, too commonly, reduce the population density of the wasps parasitizing the caterpillars, and render them ineffective in reducing the number of caterpillars.

Does this occur more broadly? That is, do any of the human parasites you will cover have their own parasites? If they did, or could, that would seem to offer a different path to controlling our parasites.

Finally, on your rate for creating new podcasts - please continue to produce them at whatever rate you can tolerate! I am quite willing to wait to hear your conversations, and would rather wait longer to have more than to have you burn out trying to meet some schedule.

Take care,


Peter writes:

Malaria parasite caught in the act:

Luke writes:

Hello professors,
I saw this paper in Cell Host and Microbe where the authors have captured a movie of a malaria parasite invading a blood cell by using a combination of heparin and E60 to boost the number of events. The paper, itself, I believe is closed access, but the movie is available through this New Scientist article:

Thought it might work well as a pick of the week for twip. Thanks so much for opening up the world of parasites to me through this podcast.

John writes:

Dear Doctors,

I'm sure you will have this in your feeds or sent in by several folks but just in case...

A video of plasmodium entering a red blood cell. Really a series of stills strung together as a movie. Quite fascinating to see the effects about 3/4 of the way through.

Thanks again for the entertaining education and a belated happy new year to the crew.



PS "Another TWiP is spiral" is clearly a masterpiece tagline and should be reconsidered.

Arsen writes:

Hey! Just listened to twip#21, where you said, that the only way to verify, if Ascaris lumbricoides inhibits growth in humans would be to infect a bunch of kids with it and watch them grow (which wouldn't be ethically acceptable). I don't think that this is the only way. Because we have areas with high worm infections already, the incidence of worm infections in an area should be inversely correlated to average height of people living in that area (of course, we should correct for dietary factors etc, but we should know the data for those factors by now)

Keep it up


TWiP 22 Letters

Luca writes:

Hi Vince and Dick,

I am an avid listener of your podcast (and Twiv, too) - I started something like six months ago and I've retrieved all those whose title sounded interesting. I am not a parasitologist myself, though I am a pharmaceutical (computational) chemist with a deep interest in biology and virology. My passion for parasitology blossomed upon reading "Parasite Rex" by Carl Zimmer, and was re-stoked by your wonderful podcast. By the way, that book would definitely make for a wonderful pick of the week. Please excuse me if my english may seem a bit long-winded, but my brain is wired for Italian, where long, convoluted, interdependent phrases are the norm. And even after ten years of life abroad I can't seem to shake the habit.

I was listening to your latest when you were talking about the scientists of Antwerp's Tropical Disease Institute and their attempt at fighting L. Congolense. I happen to live in Mechelen, a Belgian city halfway between Brussel and Antwerp. One of you two (Dick, perhaps) suggested raising zebras and eland for meat rather than cows, in Africa. I believe this is already happening, although in a limited fashion. Africa is probably a bit too far for meat grown there to reach you, or maybe American habits are different. Here in Belgium, it's rather easy to find zebra's, ostrich, antelope's and even crocodile's meat in most supermarket. The origin is usually South Africa, where I believe they're farmed or at least reared in semi-wilderness. Needless to say, I've tried them all... As a native of the mediterranean island of Sardinia, I am deeply passionate about thin sliced horse meat quickly roasted on the fire, seasoned with garlic, olive oil and spicy 'peperoncino', or chili as it
's known to you. I am probably a very good parasite host, since I like my meat almost rare and when abroad I nibble on wild plants, from Rwanda to Turkey. What's the point is going to see Gorillas if you don't try their wild celery?

Thanks so much for your effort in diffusing your knowledge, I'll keep listening and will suggest your podcast to my research group and people in compoanies who sometimes are hard-pressed to find the time to keep abreast of interesting literature.

As for This week in Physics, I guess that field is pretty well covered by the various Nature and Science Podcasts and the likes of them... What's hard to find in my opinion is a decent podcast in the field of drug dveelopment. Nature runs a couple but they're sporadically updated, so they don't cut it for me. If you have any suggestion...

All the best with your endeavour


Debora writes:

You were going to describe how the trichuris trichuria causes anemia; not from blood sucking, but you mentioned within the bone? But you never elaborated. Could you explain?

I've been using necator americanus for my Crohn's disease with good success for 3 years now. I lose my worms within 6 months, however, and the Crohn's returns. I recently tried adding trichuris suis ova, and had a very negative reaction, which was unexpected.

You made a few mistakes about Crohn's... it is not located only to the colon, it can affect the entire digestive track, from mouth to anus. Ulcerative colitis is colon only. Both are IBD, and both trichuris and hookworms are being investigated currently as "therapy" .

Thank you for your interesting information and for mentioning the hygiene hypothesis. I learned more about whipworms and would like to hear more their relationship with allergy and autoimmunity.

Herbert writes:

I was also able to achieve remission from Crohn's after getting hookworms and whipworms. You can follow my progress here:
Also, there's a wiki page that contains a ton of information on this topic, including helminthic therapy providers:
A whole lot of research articles on helminthic therapy can be found here:

Richelle writes:

Thank you Vincent and Dickson for your fantastic podcast. I am a police officer with a hobby in science. Trying to squeeze in some study and was in a panic about how I would cram for my microbiology exam next Thursday since work is sending me away for 4 days. I will be sitting in airports for much of that time. But now I have all of TWiP and many TWiV. I already listened to them all but will listen over and over while I am away. I wish you had more on schistosomas and fungi. I love the history you include in your information and also the references to scientists currently working on various things. Vincent asks almost all of my questions. I hope you dont get bored doing these podcasts because I will be a faithful follower from now on. I looked to vote for you in the podcast awards but you weren't there. I voted for the Brain Science Podcast instead. Am sure you will be there next year.

Love from Richelle in Canberra.

TWiP 21 Letters

Carolyn writes:

Dear Dick and Vincent,

Thank you very much for discussing my question on Crypto and the Miox disinfecting system on the last podcast. I appreciated the additional information.

My daughter sent me this link to a CDC report on killing crypto oocysts with miox.
I know you would probably still recommend the filter, but I just want to be sure of all my options.


Chad writes:

One of my friends posted this movie on Facebook, and I thought you would be interested.

Eric writes:

Hi Vincent and Dickson:

I'm up to TWIP 13, and I'm learning quite a bit. Got a couple questions:

1. I understand that sickle cell trait affords some resistance to malaria, could you comment on this. I've heard that if you have 2 (genes?) you get the sickle cell disease, but if only 1, just the trait and it's speculated that this evolved for protection against malaria. Is this still the belief?

2. I thought sex evolved to provide an organisim with a faster way to adapt. With sex there are more slightly different members of a species and so allows for faster adaptation in a crisis than would clones.

I'm confused about sex in the single celled parisites. If there's only a single cell, and it makes both males and females, how does this result in more choices. Where do these join up in sexual combinations that are not all from the same "mother" cell. If a cat eats a rat that is infected with Toxoplasma, how did the rat get more than one set of different offspring. Does it have to be infected multiple times by different lines and then meet up in the gut? Or eat multiple infected rats? Ditto for malaria.

Keep em coming, I am still listening even though for a few moments I worried that my flu this year was malaria. Fortunately, no big headache or backache. But I did wonder about whether mosquitos were still dangerous in the "winter" in S. California. How cold does it have to be for them to die. It's been no lower than 45 deg F. at night here in L.A.

Regards, and great job,


Alan Dove writes:


This might be interesting to cover on the next TWiP.

-- Alan

Jim writes:

For TWIP in case you didn't see it. How difficult might it be to use this approach to cure/prevent river blindness?

Smithfield, VA

Study sheds new light on river blindness parasite
via e! Science News - Health & Medicine on 1/12/11

The team found that a bacterium inside the worm acts as a 'disguise' for the parasite, resulting in the immune system reacting to it in an ineffective way. The bacteria protect the worm from the body's natural defences, but once the bacteria are removed with antibiotics, the immune system responds appropriately, releasing cells, called eosinophils, that kill the worm.

Jim writes:

Dick and Vince:

I understand bed bugs can be killed with heat. This article about lice indicates dehydration is the killing mechanism. I wonder if the same applies to bed bugs and the heat just hastens the process. If so, might running several dehumidifiers and a heater in a sealed room be a faster means of ged bug disinfection.

Smithfield, VA


TWiP 20 Letters

Jim writes:

For TWIP file (link).

Smithfield, VA

Marc writes:

Dear Vince and Dickson

Wonderful job on both podcasts. I just finished listening to the Cryptosporidium episode. I love all topics regarding the apicomplexa, and unless I am mistaken there is a fascinating aspect of this phylum which I have not heard discussed on your show. This is the apicoplast. As I am sure Dickson is aware some time in the early 1990s a degenerate plastid was discovered in Plasmodium and later discovered in most apicomplexans. Interestingly it was also noted that Cryptosporidium lacked this organelle and present evidence indicates that gregarines (another type of apicomplexan) also lack a plastid. The presence of this plastid is interesting for many reasons. Primarily this organelle may provide drug targets that would not interfere with host biology (due to the cyanobacterial origin of plastid). However what I find most fascinating is what this implies from an evolutionary perspective, that modern day bloody parasites like Plasmodium have an algal/photosynthetic ancestry. Talk about wild evolution! This has been exemplified by a discovery in 2008 of Chromera velia, a photosynthetic alga that is close phylogenetically to the apicomplexa. Evolutionary implications of this plastid are indeed fascinating from both the perspective of horizontal gene transfer as well as the evolution of the relationship between these parasites and their hosts. These relationship are ancient, indeed! These discusisons tend to stray from topics regarding virulence however I feel your listeners would enjoy hearing something about the evolutionary history which developed these truly chimeric yet single-celled critters!
Keep up the good work


Carolyn writes:

Dear Vincent and Dick,
I am really enjoying your podcasts on parasites. I took special note of the one you did on cryptosporidium.

I am a 52 year old beginning backpacker. In doing the research on water purification, I found that giardia and crypto were the two that came up the most. Since I would prefer not to use a mechanical filter and don't mind the taste of chlorine, I want to use a Miox system. (a super-chlorination system using table salt and a battery) The instructions say that it kills giardia within 30 minutes, but it takes 4 hours to kill crypto.

In listening to the podcast, I found that every time it looked like some questions might get answered, the point of the topic shifted to something else.

Here are the conflicts I have:
When I hiked Pikes Peak, the Barr Camp personnel said they only knew about protecting against giardia. Is crypto not something to really worry about? Or is it really everywhere?

You mentioned immunity. If a person is immune, does that mean they won't have symptom? Symptoms are less? I drank out of a lot of creeks and even ditches when I was a kid. Am I immune?

You said that chlorine won't kill it. Will Miox solution kill it in 4 hours, or are the instructions wrong? (The army uses miox)

I REALLY don't want to get sick, but I can't lug around gallons of water everytime.


Sam writes:

What about this for a catch line:

Another twip is hosted.

Another twip is vectored.

Another twip is spiral.

Jesper writes:

All in the Mind, a great radio show from Radio National Australia mainly about things pertaining to the brain, did a show about
parasites and their effect on populations. You'll find it on
including a transcipt.

One comment references RadioLab, which I must assume is the one where Prof Despommier was featured.

All the best,


Felix writes:

Hi Prof,

I don't think in your program on Crypto that you actually said by what mechanism it causes diarrhoea.
Whereas you have given similar explanations for other organisms.


Atila writes:

Dear Twipers and Twivers,

After listening to all TWiPs (although I will listen twip 19 in some minutes) I have noticed many readers send suggestions of parasites that manipulate hosts behavior, such as Cordyceps fungus. So, I wanted to make my contribution too, and add to the discussion of modifying mosquitoes to bite less and decrease malaria transmission.

The problem I see in this approach is that the plasmodium already does it! Plasmodium is able to make the infected mosquito bite more frequently, thus increasing its transmission:

Koella, J. C. (2005). Malaria as a manipulator. Behavioural Processes, 68, 271-273. doi: 10.1016/j.beproc.2004.10.004.

Also, it is not only the mosquito that plasmodium can modify. It makes infected people more attractive to mosquitoes:

Lacroix, R., Mukabana, W. R., Gouagna, L. C., & Koella, J. C. (2005). Malaria infection increases attractiveness of humans to mosquitoes.PLoS biology, 3(9), e298. Public Library of Science. doi: 10.1371/journal.pbio.0030298.

As a regular TWiV listener (and a big fan) I like the differences between the two podcasts. Professor Despommier's impeccable narration (I liked this letter) makes parastism really interesting. I had a terrible impression of parasitism in college, it is a big topic of biology in Brazil, since there where many parasitic diseases here not so long ago, and some parts of the country still have it, and the lectures were all focused on long life cycles a lots of different names.
Only after reading the histories behind the diseases, the patients and the discoveries, as well as learning the host-parasite interactions I started to like this topic. Carl Zimmer's texts had a big role in this change and I am very fortunate to hear someone with so much experience and personal history as Dick Despommier in TWiP. Specially now that he is a busy popstar and bestseller writer.

Long and prosper success to TWiP,


p.s. I have great expectations for the guests you may invite, given the quality of TWiP and the guests of TWiV.

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