To my great delight, I just discovered your podcasts twiv, twim and twip.
The first twip I heard, about Strongyloides stercoralis, although informative and interesting, seemed to have several inaccuracies. I was not able to find the email from Dick Despommier, and therefore I am writing to you.
Dick said that Strongyloides, when it enters into the host, becomes a protrandrous hermaphrodite adult. Actually this is not true. The parasitic stage of Strongyloides is a female that reproduces by parthenogenesis.
He also said that a protrandrous nematode is first male and then becomes female, so that it can self-fertilize. Actually, as I said, Strongyloides is not a hermaphrodite and therefore it cannot be protrandrous. The only nematode parasites that I know to be a protrandrous hermaphrodites are worms of the genus Rhabdias, which usually infect amphibians and reptiles.
C. elegans is a good example for a protrandrous hermaphrodite nematode. The term protrandrous means that the organism first produces male gametes and later shifts to the production of female gametes. The only difference between C. elegans hermaphrodites and females of closely related species is the ability of the hermaphrodites to produce a limited amount of sperm just before becoming adult. These "female-bodied C. elegans with sperm" are not considered males because they cannot transfer their sperm to other individuals. The sperm of these worms are stored in the spermatheca and used for self-fertilizing the oocytes produced during adulthood. C. elegans males are morphologically very different from hermaphrodites, produce only sperm, and have specialized mating structures used to find and fertilize the hermaphrodites.
My field of specialization is actually evolution of modes of reproduction of nematodes. I study a free-living nematode that can produce males, females and hermaphrodites. In many ways, it resembles parasitic nematodes, because larvae that sense the lack of food become "dauers", which is the dispersive stage of free-living nematodes. Dauers are the equivalent larval stage as the infective stage in parasites. Dauers can resist to harsh environmental conditions, crawl in arthropods and be transported to new places. For the species of nematode that I study, the dauers develop into self-reproducing adults once they encounter a habitat with food. This makes sense, because they can then colonize new environments without the need of a mating partner. The larvae that grow in an environment with enough food develop into females and males.
In case you are interested in reading more about it, check the paper Chaudhuri et al in the website http://wweb.uta.edu/faculty/apires/publications.html.
Dear Prof. Racaniello,
I have been a huge Twiv, Twip, and twim listener for about a year, I love the show.. Twip the most.. I love listening to you and that Deponia guy.. you guys make me laugh but more importantly I have attained a great deal of knowledge from the podcasts can't help but tell my collieges about the amazing things you two talk about from Toxoplasmosis or several parasite epidemics.
I am writing you b/c tommorow night I am going to post you as The American of the Day in my facebook group because of your great
accomplishments and devotion to educate the public about science. If you get time on the 10/23/13 search the Facebook group American of the Day and you will see your photo and bio added to our list of great Americans... it's a small honor..lol and I have a feeling you won't have time but thankyou so much for the podcasts there is nothing like it out there, if it wasn't for you guys I would have to read these journals all by myself and that gets both confusing and lonely. Thanks again-
Noah RN --- Lebanon PA
I am from the San Francisco Bay Area and I wanted to extend my appreciation for the show! I listen to both TWIP and TWIV and would be disappointed if you didn't produce the show into the future. The conversations require the listener to pay attention a bit more than the average podcast, I believe. This may, in part, be due to the use of terminology that I often find myself looking up during the podcast or later when I've heard it more than once on the show. As a result I feel like I'm in on a conversation that I normally wouldn't be and this inspires me to try even harder to understand the concepts.
One more thing: While out at a bar the other day I had randomly met someone who had his Phd in the biosciences (I don't remember specifics -- I studied Earth & Planetary Science) and I had mentioned that I listen to TWIV and TWIP and he knew who Vincent was, which led to him to add your podcast to his iTunes at the bar.
Keep up the good work. I looked for your podcast page on Facebook and didn't find it -- did I miss something? If not, you should create one. Its a good way to promote your show.
Remember for every person that writes an email there's probably a bunch more that want to but just don't get to it.
It is 1 degree outside my window as I write three comments about TWiP 63.
1. You wondered how Plasmodium DNA ended up in ape feces. I learned biology when life was made of cells rather than molecules, so I think of the body not as a big amino acid sequence but rather as a series of tubes. With this old-fashioned background, I thought the path dismissed by Dickson was obvious.
The liver recycles old red blood cells to recover iron. It dumps the rest of the cell contents into the intestines. If it recycles an
infected red blood cell, the waste may include Plasmodium DNA.
2. How do merozoites know when to stop producing copies of themselves and make gametocytes instead? I can imagine three mechanisms:
(a) random chance
(b) a molecular clock like telomeres, which allow cells to count generations
(c) environmental cues related to overpopulation, such as oxygen concentration
If you give me a grant and a lab I would be happy to watch a team of grad students investigate.
3. Do I understand correctly that a deadly infection can result from just one Plasmodium sporozoite cell lodging in the liver? (15 minutes in)
As a resident of Latin America, it was with some interest that I noted this story in Science Daily. I would appreciate your comments:
As I have, on several occasions, discovered the insect vector in my living space, this parasite is of some concern to me.
I would like to know if the parasite is a threat to the two cats who live in the house with me, or my dog who lives in my yard. I have not been able to find any information on the veterinary implications of this parasite.
Regards and thanks for a great podcast,
Cartago, Costa Rica
Hi Dickson and Vincent,
I guess the tri-caster medical device is almost here. If this is viable, very cool! What's next?
Rice University researchers have developed a noninvasive technology that accurately detects low levels of malaria infection through the skin in seconds with a laser scanner. The "vapor nanobubble" technology requires no dyes or diagnostic chemicals, and there is no need to draw blood.
Never miss your great podcasts!
Neva from Buda
I got recommended your podcast from a colleague. I just wanted to know what song by RJ do you play in your intro? I emailed him and he thought it was "Guitar Sounds" but it's not quite right. Do you mind posting the title somewhere ?
Greetings Vincent and Dick,
Hooray for finally mentioning G. pulchrum in episode 62, my most favorite parasite and one worthy of further discussion. As a diagnostic veterinary pathologist, I encounter this spirurid in approximately one third of the dairy cows I autopsy. It is much more common than you surmised. I make a big deal out of its frequent occurrence, not because of its pathogenicity (essentially none), but because it is a paradigm organism. It insinuates itself in the esophageal mucosa, wriggling back and forth in the epithelial layer as it advances (that is why it is called the 'ribbon candy' worm) thereby maintaining its hold and evading immune surveillance. The paradigm is that it is a beautiful example of an innocuous host parasite realtionship and the fact that most diagnosticians readily overlook it. Students of pathology all too often 'look' but fail to 'observe'. A south african veterinary pathologist told me that Gongylonemiasis occurs in the mouth of poor ruaral children, presumably due to the ease with which they ingest an infected beetle intermediate. It has been some time since I last reviewed the literature, but I believe the nematode is world-wide and capable of parasitizing innumerable mammalian species. I enjoy your program, biomedical science musings and digressions. Keep up the good work.
Hello, Vincent and Dickson!
First, let me start with some praise. I thoroughly enjoy all of the TWiXcasts, but I appreciate TWiP in particular for its one-on-one format and the wealth of clinical experience and case studies that Dickson brings to bear in every episode. I finished Vincent's outstanding Coursera course recently- looking forward to part two, on that note- and it set me to wondering when Dickson is planning on doing a Coursera class on parasitism.
I'm writing because I'm curious if the military has ever tried to weaponize helminths. I'm aware of past efforts by the military to weaponize practically everything, especially in the realm of pathogens- running the spectrum from from Y. Pestis and Smallpox to Coccidiodes fungi. I wouldn't imagine that an attempt to weaponize helminths would be very successful, though, and attempts to imagine such a program are baffling at best.
Keep up the outstanding work, gentlemen, and thanks again for your time and effort.
Dear Professors Despommier and Racaniello,
I wanted to write to you to thank you for taking the time to do these fantastic podcasts. TWiP was recommended to me by a former colleague with whom I worked in Professor Paul Duprex's virology lab at Queen's University Belfast, before he moved to Boston University. Since working with Prof. Duprex I got my PhD in molecular parasitology, and now I work in St. George's University of London on the nanomal project (the link for which I've included) which you may find interesting:
We're developing a hand-held point-of-care diagnostic device for malaria that can give a diagnosis in under 20 minutes, but the really exciting part is it will be able to speciate and detect drug resistance-conferring mutations so an informed treatment choice can be made.
Being a malariologist I particularly enjoyed TWiP#35 with David Fidock, and my interest was especially piqued when the contentious subject of artemisinins' mode of action was brought up. I thought this was about to be explored but alas, it was not. Of course, there are not enough hours in the day to debate that subject. If you are interested, however, we recently published an opinion article in Trends in Pharmacological Sciences on the subject which I have attached. Professor Fidock mentioned the haem hypothesis, but I am more in favour of the SERCA hypothesis, which postulates that artemisinins specifically inhibit the sarco/endoplasmic reticulum calcium ATPase (SERCA) of the plasmodia parasites. People may feel that knowing the mode of action of a drug is purely academic, but as you are well aware drug resistance is a serious problem for controlling malaria, and knowing how a drug works can help identify any mutations responsible and hopefully overcome resistance.
Thank you again for all the time and effort you put in to these podcasts. I have thoroughly enjoyed learning about different parasites, not to mention american history and piscatorial pursuits, and constantly recommend TWiP to my fellow parasitologists. I plan to start listening to TWiV but it's been quite a while since my virology days. I hope I can keep up!
Hello to Vincent and Dickson, TWIP
First may I say, that it's great you are putting such in-depth content out in the public domain, People such as yourselves, with vast amounts of knowledge and years of experiences giving your knowledge freely is fantastic and I apualde your for it. And not to mention your presentation style is superb and funny.
The Microbe world fascinating to me, I bought a decent Amscope microscope last year, I have always wanted one but after getting into TWIV /TWIP /TWIM, I finally bought one. I've used it many times looking at pond life/mouth bactria/poo from my dog "Bella" who is female and very coprophagic towards next doors cat :( I basically put anything i dare put on a slide to the horror of my fella, Our daughter loves it too, with all the "yucks" and "Errrs".
Anyway to cut a long story short, Not that I have been waiting for a decent infection but last week I contracted what I thought could only be described as food poisoning, after 24 hours of (diarrhea/vomiting/burping/feeling bloated/major cramps) I thought the best thing to to is check a stool sample, naturally..... As I had never been so ill
My thoughts were that it could be Food poisoning but i wasn't convinced, after going back and hearing TWIP #16 Giardia Lamblia it rang a few bells.
On investigation all could see no Giardia Cysts but I could see many uniform tubes with constrictions at the end, Being uniform and tube like my first thought was Dog Tapeworms? Or could it just simply be something I ate as it looks like plant matter, I'm sure if it is parasite debris then Dickson can identify it in a jiffy.
After searching Google to no avail, I feel I may need a copy of "People, Parasites, and Plowshares" for future use?
Here are a few pictures of the tube like forms? Seeing as though Dickson has seen many stool samples in his time, I thought it to be great opportunity to write in and express my gratitude for all the great work you are doing plus a token of that appreciation.
Keep up the good work and thank you so much for bringing science to the rabble.
Good morning, day, evening (depending on your time of day). Esteemed professors!
Firstly my weather report, for Weston super Mare, uk.
It is currently 3 centigrade (feels like 2C), dew point 4C, humidity 78%, there has been 1mm of rain/sleet, with a 50% chance of further precipitation, and the wind is 16 km/h from the WNW. It is currently dark so no visibility, but this is estimated as 2 miles, as it is cloudy with light rain.
The predicted high for the day (2PM) 9C, with humidity of 68%, and dew point of 4C, with predicted wind of 21km/h, a 40% chance of precipitation (rain or sleet), to is expected to be partly sunny, with good visibility >10 miles predicted.
I hope the weather report meets your increasingly exacting requirements :)
My question is actually fairly simple; Giardia lamblia and a number of other eukaryotes lack mitochondria. Most of them appear to be anaerobic, and I can see the point that the mitochondria and electron transport mechanism might well be selected against.
However, no where can I find if it is clear that mitochondria where selected against, and lost. Or if these bugs are a branch, that where started before eukaryotes adopted mitochondria.
I'm not scientist, but simply an interested party. I actually work as an engineer, on sewage treatment plants. So I do get to see a lot of bacteria, since they do all the work, treating the sewage. Given plenty of oxygen, and the correct nutrients, they do a fine job of this, and then happily settle out, leaving clean enough water that it can be returned to the environment (or with minimal treatment, and filtration, to the drinking water supply, as is becoming more popular).
However it is my personal theory, that apoptosis in eukariotic cells derives from the incorporation of a once parasitic bacterium. Such a parasite requiring a method to kill the host cell, in order to proliferate into the medium, to infect other cells. I hypothesise that this was co-opted by eukaryotes, in order to allow for apoptosis (or programmed cell death).
Knowing if apoptosis odours in eukaryotes, that lack mitochondria, and if they are a pre mitochondria branch, would answer my question. However I have been unable to find the required information.
I wonder if you can point me in the right direction, and also thought the subject might lead to an interesting conversation on the podcast.
Many thanks for your ongoing series of podcasts.
I have emailed this to both TWIP, and TWIM. I suspect it is better suited to TWIM, but my research has been on parasites, since these seem better studied, so have included TWIP.
Thanks in advance for any insights you may be able to provide, or simply interesting conversation.
Hiya! Entering mid-dialogue, so sorry for out-of-touch points hereafter. Trivial anyhow.
As to fuel powered machines and discovery of oil deposits (identified as refineable fuel, since deposits were mined for minor purposes in antiquity), um, as I recall, Henry Ford intended his internal combustion engines to run on ethanol at the outset. I have no idea how far earlier the engine-makers planned ethanol, but.... Anyway, Rockefeller et al came along shortly to amend all that. Besides, obviously y'all were perfectly accurate about all that machinery thing and slavery.
More to the point of parasitology, another trivial emendation may be that the first hookworms didn't necessarily enter N. America on African feet after 1600. West Africans had been transported to Caribbean islands for labor by mid 1500s. They may have inoculated soil there with hookworms, which may have been picked up by sojourning barefoot non-Africans, and transported to N. America first by those people after 1600. Maybe. (If I haven't misremembered the true mid-century. Got it from "Diary of an Irish Slave Girl," a novel about a kidnapped child who was taken to a British sugar plantation and ended up marrying an Ashanti man. Therefore my historiography may be off. But I do think those island plantations were started up in the 1550s or so -- and, from other sources, European population growth began to explode, apparently correlated with sudden availability of enough extra calories to delay starvation, preserving more children, etc.)
So anyway. Hope It's not wasted your time. Entertained me, but not enough to edit it down.
I love your show, I hear it on the way to work and home again each day. Would love to hear during work as well but my coworkers would complain I guess. I have a question regarding the theme song at the beginning of twip63. What song/remix is that?
Kind regards and all the best!
I have listened to you discuss parasitic diseases in mice, fish, mosquitoes, ladybugs, cats, and even humans, and feel you have paid relatively little attention to squirrels. A recent paper in BMC Veterinary Research could help cure that deficiency.
British veterinarians studied 163 dead red squirrels. The squirrels were mostly found near houses and roads, and half of them were killed by cars or pets.
The dead squirrels were examined to determine cause of death and inventory parasites and other disease causing agents.
I spotted at least four eukaryotic parasites -- three Apicomplexa and a nematode -- only one of which I recall hearing about on TWiP.
Toxoplasmosis was blamed for one sixth of squirrel deaths on the Isle of Wight. It was considered a direct cause of death rather than a contributing factor like when it prevents mice from avoiding cats.
Hepatozoon infections were common in lungs and heart muscles, and Eimeria in gut contents, but neither seemed to be a primary cause of poor health.
The last parasite is so obscure it does not even have a Wikipedia page. It is related to pinworm, which you have discussed. Quoting the paper:
"Nematodes were sometimes observed during gross and histological examination of intestine. Morphologically they resembled pin worms (Enterobius sp.) but, apart from one case where they were identified as Rodentoxyuris sciuri, none were submitted for species identification. Typically there was no apparent associated pathology but one juvenile with a heavy nematode infection died due to an intestinal intussusception. However, in a second case of intussusception involving an adult there was no significant worm burden and the aetiology was obscure."
The squirrels also had viruses and bacteria, in case you want to have a squirrel week across all three "this week in" podcasts, end ectoparasites and fungus if you want to expand to five podcasts.
I couldn't remember being tested for Toxoplasmosis with any of my pregnancies while listening to your most recent podcast so I looked it up. According to MayoClinic.com most women aren't tested automatically these days. I didn't find any specific recommendations anywhere, though, so maybe it's something that depends on the doctor.
I do remember tests for AIDS and Hepatitis. Especially since with the most recent one the lab gave me someone else's positive Hepatitis result and missed my anemia :p
These days they just tell every pregnant woman to avoid under cooked meats and litter boxes.
PS It's cold down here in central Texas! I can translate easily from Fahrenheit to Celsius because it's been hovering just above 32F/0C for the last few days. We may even get what passes for snow around here... a few flakes mixed with the rain. I expect by next week it'll be shorts weather again, though.
Maybe that would make more sense as While listening to your most recent podcast, I couldn't remember being tested for Toxoplasmosis during any of my pregnancies...
Hello TWIP! I write to you again from Tucson, where we are having quite a warm December. Today was a beautiful day, 75F, with sunshine and scattered clouds.
I was listening to Dickson explain the difference between Plasmodium vivax and P. falciparum on a historical TWIP whose number I don't recall, when later that day what should I read but the links below, reporting P. vivax infections in Duffy negative humans. The articles report that duplication of the Duffy binding genes seems to enable infection even without the Duffy receptor (per http://www.eurekalert.org/pub_releases/2013-11/cwru-vmm111413.php another report is expected 12/5, in just a few days).
It seems odd to me that duplicating this gene would have this effect - after all, wouldn't this be like having multiple keys to a door with no lock? It must be using a receptor of some kind, right? If it's not using Duffy, then it must be using another one - is Duffy part of a family of related receptors, or has the gene duplication produced a match for some other receptor altogether? I also wonder how this mutated parasite will fare in ordinary Duffy positive humans. I'd love it if you all could revisit this topic on the show.
On an unrelated note, I must say that the presentation of this open access paper (link below) is really great. No truncated article, clear navigation and organization, and it even includes a twitter interface. Three cheers for PLOS!
Thanks again, Victor and Dickson, for the podcast - Sam
As a new listener, I don't know whether you've later corrected this or not, but you got several important things wrong in describing the antebellum South in the first episode on Hookworm. They did have machines, and they made good use of them. What they did not have was factories, because they were making plenty of money farming on the backs of unpaid slaves.
The first Africans arrived in Jamestown in the early 1600's, not long after the European settlers arrived. (You said the 1830's.) The cotton gin was invented in 1793. It made cotton farming *far* more profitable, greatly increasing the slave trade until the international slave trade was banned in 1808. Internal slave trading continued, and the slave population continued to grow dramatically because the slave women were forced to have as many children as possible. Children born to female slaves became slaves, whether their fathers were slave or free. "Due to its inadvertent effect on American slavery, the invention of the cotton gin is frequently cited as one of the ultimate causes of the Civil War." The American South provided two thirds of the world supply of cotton by the start of the Civil War.
So hookworm must have been endemic long before the Civil War. There wasn't much more introduction after 1808. However, substantial parts of the South were still under Native American control, and thus perhaps free of hookworm, until the Trail of Tears forced relocation in 1830, and the land was sold for agricultural use.
Also, there was slavery in the north, though certainly not as much. There were still slaves in New Hampshire and New Jersey until the emancipation proclamation in 1865. Other northern states had banned it earlier. Southerners brought their slaves with them when they came north. You can see George Washington's slave quarters in Philadelphia across the street from the Liberty Bell. Slaves who got their freedom in various ways migrated north.
The American history mistakes start about 10 minutes into the episode.
Thanks for a great podcast!
Hi Dickson and Vincent,
I recently started listening to TWIP and TWIV, and I love them both! It's been hard trying to catch up and listen to them all (needless to say, I'm not even close).
I'm wondering if you guys know of any neotropical parasites (or viruses for that matter, I just thought parasites might be more likely) that live some part of their lives in both snails and bats.
I'd appreciate any thoughts you may have :)
Thanks so much!!
Hi TWIP Twosome,
A story about how the US planned to weaponize bats during WWII.
Ed Yong tweeted this. What a batty tale.
You guys are da bomb,
Neva in Buda TX
Hi Dickson and Vincent,
I listen to every episode of Twiv, Twip and Twim and often follow along with Wikipedia to help me understand terms i am not familiar with and also check out most of your picks.
I also watch Monsters Inside Me with my 12 year old daughters. I am up to Season 2, Episode 3 and was just wondering if you (Dickson) were still advising on this show?
In this episode a man got very ill and his spleen swelled to 5 times it's normal size, after a battery of tests finally a test for leishmaniasis came back positive, would this be visceral leishmaniasis?
I didn't pick this as I would expect some sort of skin lesion. Also they treated him with anti-biotics and he recovered, I am only a computer programmer but I would not think anti biotics would be the recommended treatment for leishmaniasis
Thanks for the awesome work of the entire TWIx crew puts into producing these podcasts
Shane from Australia
P.S. It's a balmy 20 degrees C at 11pm
I recently found out that when my mum was pregnant with me she was tested for toxoplasmosis, and it turned out that she had very high titres of IgG against toxoplasma. However, she took no treatment, and had absolutely no symptoms of disease. I turned out ok, I think, so it doesn't seem to have done anything bad. So I was wondering, are all pregnant women tested for toxoplasmosis and if so why? My mum was pregnant in 1992 and it was in Lithuania, so I wouldn't be surprised if things have changed from that time or have always been different in US. Does carriage of toxoplasma pose any threats for pregnant women and their foetuses? Also, Is it likely that I now have antibodies against toxoplasma because my mother was infected while pregnant?
I saw today in the New York Times that a hookworm vaccine will be tested in Gabon. I found this very intriguing as your discussions of parasitic worms have rarely included the possibility of vaccines. Can you please comment on this. Are there certain biological challenges to making vaccines against worms? Or is there simply no money in making these vaccines since they are not needed in rich developed countries? It seems to me that it would be much simpler (and cheaper) to just educate people on how to avoid most of these parasites than to produce a vaccine. Simple practises, such as digging your outhouse six feet deep, or curing your feces before using it as fertilizer would eliminate many of these parasites. I would love to hear your comments on this matter.
Fort McMurray, AB, Canada
PS. The Link to the NYTimes article is here:
In a local newspaper:
"Zoonotic research taking Framingham man to Peru"
Parasites may be sneakier than we surmise:
Transformation of malaria parasites by the spontaneous uptake and expression of DNA from human erythrocytes
We may have more baggage than we know:
Invasive Genes: Humans incorporate DNA from parasite
A pdf made from a local newspaper article is attached concerning a biologist who found a nematode embedded in his mouth. The article is available online from The Daily Press, but you have to subscribe to read it. I assume it's ok to make the pdf available to your listeners, if you desire.
I know that insect larvae are much bigger than your usual fortey, but I find the bot-fly life-cycle fascinating. I don't think it can be defined as an ecto-parasite, as it actually develops inside the skin, not on top of it. Care to discuss it a little? I would love to hear your take Dick.
Here's another one, and I quote,
"A scientific discovery falls out of this epidemiologist's nose
Tuesday, October 15, 2013 1:28 PM
Imagine finding a tick up your nose — and being happy about it.
Epidemiologist Tony Goldberg was working with primates in Kibale National Park in Uganda. But, when he returned to his lab at the University of Wisconsin, he began feeling some pain in his nose.
That's when Goldberg discovered a tick inside his right nostril. Definitely not something that's cause for celebration, usually.
"I made use of a mirror, a flashlight and some forceps to remove it," Goldberg said. "I was fortunate to grasp it firmly by the mouth parts and I got the tick in its entirety out of my nose, sparing the surrounding nose hairs."
But, being a man of science, after he removed the tick, Goldberg analyzed its DNA.
The nostril tick belonged to the genus Amblyomma. But it didn't match any known bugs in various databases.
That means it could be a tick that hasn't been genetically characterized yet — or a completely new species.
"We're still learning the pathways that diseases can use to move between wildlife and people. And this nose tick is a slightly amusing and particularly gross example of how diseases move in nature," Goldberg said.
Dear esteemed and honoured Professors,
I'm writing in response to TWIP 57 where in the intro Prof Despommier mentioned that he had just returned from Singapore. The question was asked if water is spins clockwise or anticlockwise down the toilet since Singapore lies 1 degree north of the equator and I am pleased to announce, as a Singaporean, that water spins anticlockwise in Singapore.
I just did this experiment in my lab sink and toilet. Finally, I've produced some research worth noting.
Apparently the fact that it does not spin clockwise here has been noted before (check out the last paragraph). But i'm still searching as to why this is so. I do know that the coriolis effect is strongest away form the poles and that it does not have much of an effect on small sinks, ie, you can easily push water in the opposite direction and the water would willingly change its course, but none of these explains why the water rotates anti clockwise.
A student in virology, not so much in the coriolis effect.
Just got this link to an Australian Video via Digg in case it's of interest.
I just finished listening to the superb Twip #56 and I am thrilled because I am a huge fish nerd. In fact I spent much of my youth catching and chasing fish on the same lovely New Jersey barrier island mentioned in that episode. In my enthusiasm, I wanted to write in with a few thoughts.
The first is nit-picking, but the gar discussed around the 13:00 minute mark is more likely a specimen of Atlantic Needlefish, Strongylura marina, than a member of the “true gar” family Lepisosteidae. Like members of Lepisosteidae, needlefish have elongated, tubular body plans, and are sometimes referred to in common usage as gar. Needlefish often spend time at the surface, but do not gulp air in the cool way fish such as the Florida Gar do. This mix-up might explain Dickson’s surprise at hearing about gar so far north.
As an aside, I might add that I have heard that --if presented with a fly small enough to fit in their diminutive mouth--needlefish make for wonderful sport fish. I myself have caught a needlefish on Barnegat Bay, although not in the manner one might think. I spend my free time sailing a catamaran around the bay. On one windy day I had the rude surprise of a large needlefish jumping out of the water and landing in my boat! My crew and I were as shocked as the fish! It was a memorable experience; particularly because, like many angry fish, the needlefish displayed a heightened, more vibrant coloration than I usually get to see. The fish was promptly returned to the water and I was left relieved that I hadn’t been added to the list of people who have been impaled by needlefish (http://the.honoluluadvertiser.com/article/2005/Jul/30/ln/507300340.html).
In the spirit of “This Week in Fish” I would like to suggest “The Founding Fish” by John McPhee as a pick of the week. The book is a wonderful examination of everything Shad, written by a wonderfully gifted writer. I’m picking it because Twip #56 included a question about shad’s tastiness. As the book points out, the species name of the American Shad, Alosa sapidissima translates to “most delicious”. I am salivating just thinking about a meal of baked shad, perhaps with a side of Atlantic blue crab, whose species name also derives from sapidus the Latin word for savory.
As always, much thanks for all the work that goes into the TWiX podcasts. I am about to leave on a road trip across the US in order to start grad school for biology, and I am looking forward to having tales of viruses, microbes, and parasites keep me company along the way.
First of all, thank you for producing such fascinating podcasts! I got interested in parasites when I read Carl Zimmer's book - I've just discovered TWiP, through Professor Racaniello's course on Coursera, and I intend to try and listen to them all!
I've just got one question so far: is the cover photo for the page of Trichinella?
I enjoy your show although parasites are not related in any way to what I do for a living.
You have mentioned the death of the S. A. Andrée's Arctic Balloon Expedition of 1897 crew in a couple of TWIPs including in episode 60 and how they probably died of Trichinosis from eating polar bear.
I was fascinated by this and repeated it a couple of times to friends, but when I was looking for details I came across this entry in Wikipedia which says this theory was "discredited in 2010." The cited links are in Swedish and one appears to be broken at this time. The other one is very brief but using google translate it says they think it was polar bears instead. Obviously anyone can put whatever they want on the internet, but I wonder what your thoughts are on this?
Dear Vincent and Dickson,
Just a note about something that Dickson mentioned in TWiP 60, I am sure Dickson realised that he simply misspoke after it went on air, but the digenean responsible for the "Barber Pole Effect" - Leucochloridium paradoxum - is not a schistosome but belongs to the Leucochloriidae family which is on an entirely different branch of the digenean/fluke tree to the schistomes.
There are many different species of Leucochloridium and they come in different colours. For example Leucochloridium paradoxum have green bands or red-brown bands on its sporocyst brood sac (the structure which invades the tentacles of the infected snail) whereas Leucochloridium millsi has yellow or orange-yellow bands. A good paper on this topic can be found below.
Kagan, I. G. (1951). Aspects in the life history of Neoleucochloridium problematicum (Magath, 1920) new comb. and Leucochloridium cyanocittae McIntosh, 1932 (Trematoda: Brachylaemidae). Transactions of the American Microscopical Society, 70(4), 281-318.
Additionally, there is some indication that the behaviour of the snail is altered, as noted by Carl Wesenberg-Lund in this paper below.
Wesenburg-Lund, C. (1931). Contributions to the development of the Trematoda Digenea. I. The biology of Leucochloridium paradoxum. Memoires de l'Academie Royale des Sciences et des Lettres de Danemark, Copenhague, section des sciences 4, 90-142.
It was cited in Janice Moore's 2002 book "Parasites and the behaviour of animals". Wesenburg-Lund noted that "It seems as if the infested snail seek the light; they are very often see balancing on the borders of the leaves, or sitting on the underside of the leaves with only the antenna infested with the Leucochloridium protruding from the border
of the leaves..."
Now compare this with the behaviour of most terrestrial snails which prefer more damp and secluded surrounding. Such altered behaviour would expose the snail (and it brightly coloured parasite) to predation by the potential bird host.
As a side note, here is a link to a cartoon I drew about Leucochloridium a few years ago
It contains a pop culture reference, which might not be obvious to everyone, though most people below a certain age would immediately recognise it. For the listener who cannot see the imagine, it is a reference to the 2003 song "Milkshake" by Kelis.
Keep up the good work Vincent and Dickson, I look forward to more parasite tales from you in the future.
'Tain't just mice that have adverse behavioural outcomes with Toxoplasma.
Should humans attacked or killed by big cats be checked for Toxoplasmosis?
Thank you for the Bt and mosquito info. I had a feeling there had to be a catch. Since there's always plenty of other water that isn't treated I expect Bt wouldn't become completely useless but it's good to know it's not a wonder fix, either. Ah, well.
Our vaccine unit here at NIH did a study of malaria vaccine with some promising results. I know Dickson has been a champion of conquering malaria.
Dear Vincent and Dickson,
I just received a confirmed case of Cyclospora from the lab on one of my patients who has had several weeks of diarrhea. It appears to be the first one in New Jersey. The patient ate salad that tasted rotten in a local supermarket salad bar. Good thing I am a loyal and avid listener of TWIP! BTW - I am reading "Peoples, Parasites and Plowshares" and I'm really enjoying every page but my wife is scared of the cover!
Spencer Kroll MD PhD
Dr. Steven Reeves writes:
I discovered this podcast only in the past few months. Love it! I am a practicing Internist in a small (8,000 pop.) community in Iowa. I listened with interest as you discussed the ongoing cyclospora outbreak. Just as a point of interest I have three patients in my practice with a confirmed diagnosis. What I also wonder is whether we are experiencing an observational bias?? We are finding cyclospora because we are looking for it. In addition, when we send stool specimens for evaluation (culture, O&P and WBC) we must specifically ask for cyclospora testing just as we must also ask specifically for Norovirus. I find this interesting and wonder if it might be playing a role in the current numbers. Thanks again for a great podcast!!! BTW: temp today is a perfect 76 degrees F. Finally!! We have been in the grip of a heatwave.
Dear Vincent and Dickson,
I'm writing this email because of a comment made by Dickson on TWiP 57 regarding the CDC. Dickson mentioned that the CDC was underfunded and the campus still looked like something out of the 19th century. I was wondering if Dickson has visited Roybal campus (the main campus) since the turn of the millennium? A series of renovations took place starting around 2003/2004, and almost all buildings have since been replaced. The end result is quite stunning, with the campus resembling a booming metropolis (I included a link with pictures).
Unfortunately, this change has not really been reflected in scientists' salaries, and according to most standards, I would say that compensation is still less than adequate, especially considering the nature and complexity of work being done there.
Anyway, be well and keep TWiPping!
This is for Dickson. The Dec 73 National Geographic has an article about Greenland which says on p 867,"We were crossing a frozen inlet," he recalls, "when we went through the ice, losing our food and nearly all our equipment except two sleeping bags and a tent. We scrambled ashore with the dogs.
"I knew there was a trappers' hut up the coast, probably with a cache of food. In the meantime we could always eat the dogs in an emergency -- or so I thought, until the weather took a sudden warm turn.
"You see," Steen explains, "some Greenland dogs, like others in the Arctic, carry trichinosis. Dogs seem to be only mildly affected by this disease, which is caused by small worms. To humans, it can be fatal.
"To kill the worms, you either cook the meat or let it stand for several days at below-zero temperatures. The only trouble was that we had lost our stove fuel and the temperature stayed above zero."
In fact, it stayed above zero for three weeks, while a snowstorm raged. In their tent, the men grew weaker each day At last the snow stopped and they managed to walk and crawl to the hut -- followed by the dogs, who were even weaker than they. A trapper making his rounds finally rescued them.
I can send a pdf of the article, if you want it, or the hard copy for which I'll need an address. I've just dismantled a bunch of the NG's to extract indian-related material for a relative in Arizona after learning the whole magazines can't be sent by media mail because they contain advertisements! They weight about a pound each! Too bad.
Why can't Dr. Dickson TWIP via Skype when away?
Dear Esteemed and Erudite Professors,
I’d like to revisit something Dr. Despommier said about why the whole sporozoite vaccine produces immunity whereas natural infection does not. He was surprised that intravenous injection of the sporozoites was effective vs the natural way of the mosquito injecting them into the skin. I’m pretty sure if he listened to the episode later he realized he misspoke since the female mosquito indeed delivers the parasites intravenously because that is where it is getting it’s blood meal. The abstract of that paper in science contains what the authors believe is the reason it works. “These data indicate that there is a dose-dependent immunological threshold for establishing high-level protection against malaria that can be achieved with IV administration of a vaccine that is safe and meets regulatory standards.” The series of injections delivered a total dose of between 540,000 (30% protection) and 675,000 (100% protection) attenuated sporozoites vs. the much lower numbers of infectious sporozoites delivered into venules by the vector. From the parasites’ point of view less is better since a few continue the replication cycle whereas many would cause immunity or possibly death of the host by overwhelming infection.
As always, thanks for continuing to make these three series of the best science podcasts available in the universe.
I found this delightful account of a beef tapeworm infection on the internet:
"The Worm Within" http://www.fray.com/drugs/worm/
It is a fantastic read that I am sure many listeners would love to check out.
Yours in parasitology,
Fort McMurray, AB
Foyle’s War episode invoving a tick bite.
It's noteworthy by its rarity. Here's the link to an episode description which omits the tick, but the bite is crucial to the ending! Some good British TV.
I have a question possibly more related to TWiP. I've heard a couple of gardening radio show hosts mention making a mosquito trap out of standing water with mosquito dunks (Bt) in it. The idea is that any area mosquitoes lay their eggs there and don't go looking for other places with standing water. The larvae are eaten and you have fewer mosquitoes in the next generation than you would have if you'd just emptied all the standing water you could find. I was interested to hear what Dickson thought about that.
You have the best podcast on the web, hands down. I use your TWiP episodes in both my undergraduate and graduate classes.
I've recently seen a family in Hawaii with recurrent pathogenic Blastocystis hominis and Dientamoeba fragilis and I'm suspicious if they are getting it from close association with feral pigs. I see a little published on the possibility from Italy, but do you know how prevalent it is in pigs and particularly, does D. fragilis even have a transmissible cyst stage? Are both of these parasites considered emerging pathogenic diseases?
Any suggestions on setting up an investigation to answer these questions?
Allan Robbins, DIH, MPH
University of the Nations-Global Health
My name is Andy- I was wondering if you may be able to provide me some feedback on something I'm developing. I'll try to make it explicit as possible. First off, I was wondering how difficult it is to engineer a Virus's Ligands to match up with a desired Host Cells surface receptor. The relevance behind my first question is, would it be possible to engineer a virus that can attach to T. gondii surface receptors and ultimately infect the parasite? Of course there are lots of things to consider, but I'm really only curious of the concept itself. I haven't found any literature that specifically applies to my question, so I've turn to you! Any thoughts? If engineering is possible, Viable infection would be the first step and then developing an idea on how to kill the parasite would be the following (in my amateur perspective at least).
Sent from my iPhone hi you guys I am Karl from Northern Ireland :) . I would like to thank you for all the weird and wonderful information about parasites viruses and bacteria and general information discussed in you topics. It has been a pleasure writing about it so I don't forget it which helps keep me informed and can read over to remind myself of all the parasites as there are so many. I am a chef in the food industry and reminds me to be careful when handling raw food products I always were latex gloves now to keep me protected and think that more people in the catering industry should be put through a parasite awareness course for themselves and others. I say this because of my own experience of having a parasite in my body which thankfully was taken care of . :)). I am now a vegetarian and have never felt better. I have evolved at last haha. It's like the Adam and Eve story and the serpent and to choose what to eat and knowing what is good for us and what is bad for us. The ancients spoke and drew of the ouroborus now I understand what it all means. We are part of the food chain not at the top . So makes me think what is are purpose to be food for parasites so the can live and survive amount us secretly . Makes me wonder if mars has water ??,,,is there forms of parasites that may exist there also . Anyway don't want to write a book about it for use to read just taught of saying thanks again and look forward to continuing to listen to the both of your podcast and many more Interesting conversations as not many people want to talk about parasites :((. Xox
Dickson and Vincent,
By way of an introduction, I am a retired IT professional who took an undergraduate degree in biology many many years ago. TWIP, TWIV and TWIM are wonderful listening and I particularity enjoy the informal format of their broadcast.
Dickson, I am a person with Celiac, and I cannot help but wonder if Celiac evolved and survived because it might have had a survival
advantage for ridding the body of parasites which lodge in the small intestine and are hidden from the immune system. Ongoing regular
treatment by gluten would not be great for health and longevity but perhaps symptomatic or seasonal treatment by gluten containing grains
would confer some added benefit for primitive man. Could you please speculate on this possibility?
Thanks and keep up the great shows. I always look forward to listening to them on my not-an-ipod during my daily dog walk.
Dear Vincent and Dickson,
I am a huge fan of your show and I really appreciate the work that you do to make science more approachable. I especially like TWiP, because I think that parasitology is very underappreciated, not because it's any less exciting than other disciplines but possibly because of the 'yuck' reaction many people have when hearing the word 'parasite'. Your show is just another proof that parasitology can be interesting in a non-horrid way.
I guess you can apply Terence words "Homo sum, humani nihil a me alienum puto" (I am sure Dickson will enjoy translating it, as I noticed he's really into latin) even to parasites.
I have a question for you, that came to my mind when eating my garden-grown plums, which turned out to be more organic than I expected, with some worms enjoying their taste probably as much as I do: Are there any parasites that use worms (or in general insects) as vectors to get into their host via oral route?
Thanks for the great show!
You've probably already been notified on this, but the Coriolis effect has nothing to do with the way water spirals out a drain. On a body of water the size of a sink or even the Oculus the Coriolis effect is far too small to have a significant effect. The direction that water swirls in the toilet is determined by the shape of the water jets around the rim of the toilet.
Dear TWiP Hosts,
Concerning your discussion near the beginning of TWiP #57, as a youngster I was fortunate to witness a demonstration of the Coriolis effect right at the equator (in Kenya). My family and I watched a man drain water out of a plastic bowl with a hole at the bottom. A few meters north of the equator, a matchstick floating in the water spun clockwise. Literally a few meters to the south, the experiment was repeated and it spun the other way. To my amazement, directly at the equator, the water drained straight out without any rotation!
Only much later, as a student of physics, did I learn that we had been deceived. The apparent acceleration caused by the Coriolis effect is of the order of the velocity of a moving object times the angular velocity of the Earth. Even if we generously give the draining water a velocity of a meter per second, this gives an acceleration that is a hundred thousand times smaller that the acceleration due to gravity. So other effects will easily determine which way water drains out of a bowl (or a toilet bowl for that matter). I speculate that the man doing the demonstrations at the "equator" would shake the bowl slightly, perhaps even unconsciously, to get the desired outcome.
The Coriolis force has a noticeable effect in phenomena occurring over longer timescales, accumulating the effect of the very small acceleration, such as weather patterns or the precession of a Foucault pendulum, or in phenomena with very large velocities, such as the trajectories of missiles.
I hope you will excuse this digression into the world of classical mechanics, and its applications to detecting fraud in the tourism industry.
Keep up the excellent work!
Dear Vincent and Dickson,
Listening to TWiP on cyclosporiasis. Because I am all too aware of the possible contamination of many crops as a former public health nurse who worked in epidemiology for my state (Florida), I always wash my fruits and vegetables with a product called Fit. It may not be perfect in that pathogens are tenacious but I believe it reduces risk. (Could be hopeful thinking, I know.) Also, it does not alter the flavor of even delicate raspberries. I would be interested in what you think of this approach. http://www.tryfit.com I have no connection to this product whatsoever other than that of a consumer. I used to add a drop or two of liquid castile soap to fruits and vegetable wash water instead of Fit. Both approaches involve a short soak and gentle but thorough rinsing.
I was working in the Communicable disease clinics when Florida had a multi county outbreak in the 1990s. Our protocols allowed for distribution of stool culture kits then. Before I left my role, the onus was on the private sector. Unfortunately many people do not seek medical attention but treat with OTC remedies and many physicians do not test either. So the great unreported levels of both food and waterborne illnesses is a real challenge to any investigation.
Raspberries, blackberries, blueberries and strawberries were nestled in my cereal bowl this morning along with a bit of cereal! ;-) Is my approach biofilmsly?
As usual, your podcast is interesting, fun and informative. Happy that Dickson has been more available of late!
Warm and humid regards form Naples, Florida,
Dear TwiP team,
Interesting if rather gruesome report on the BBC news about a British woman who found that the headaches and pains she experienced on return from a holiday in Peru were due to an infestation of screw worm maggots in her ear.
The Coriolis effect
It even affects bicycle wheel spoke screws.
“Cyclists who regularly travel back and forth between the Northern and Southern hemispheres would be well advised to build up two rear wheels, one for use in each hemisphere...however, there's no need to have two front wheels, since the same front wheel will work in either hemisphere simply by reversing it in the fork!”
Back in the old country, decontamination of food items by a potassium permanganate solution was a standard recommendation.
Three stools negative in a row: how often?
cDc: Cult of the dead cow.
So what happens when the pupfish owl dies?
The Alternative Energy Matrix:
I found TWIP just a week ago and feel I've found a home. I'm a pharmacist, usually on the night shift, and stay excited all night listening to you. Parasites have always been my hobby. In fact, I recently divorced one. His life cycle is unique. I get oddly thrilled when dispensing anti-parasitic drugs. Thought I was odd. Thanks for normalizing me. Annie
Hello dear TWIP hosts!
Just in case you are not already exposed to this, I send you the web address for a recently launched worm-watching game:
It consists of video feeds of C. Elegans, which are being recorded automatically by tracking microscopes. As far as I understand it, the researchers want to measure the efficacy of the serotonin-regulated musculature of egg-laying for each worm, so recording when the eggs are layed is a vital piece of information.
This game is from the same guys that spawned Galaxy Zoo, where you classify galaxies, and Planet Four, where you classify terrain formations in Mars. Actually they have several interesting "scientific games", so I'd like to pick their project menu for this week:
Also, there is something I'd like to ask Dixon. In TWIP 56 you and Vincent had a brief discussion about the name TWIP, why it uses the word "Parasitism" instead of "Parasitology". It has occurred to me sometimes that the "P" in a "TWIP" show name could also mean "Pathology". Whenever I think that, I wonder if all parasitism is a pathology - not necessarily a human pathology, but some living being's pathology. I then usually imagine that Dixon could argue that not all parasites cause harm to their hosts, and therefore parasitism is not completely within the scope of pathology. Is that the case?
Thank you and all your guests for the shows!
Oops, terribly sorry for misspelling your name, Dickson!
(I guess I always think of the Dixon from the "Mason & Dixon" line when I hear your name. By the way, the book by that name by Thomas Pynchon is an awesome read (well, all Pynchon books great, but M&D is arguably the best one so far)).
On your last TWiP someone mentioned the Pandemic Board Game. I stumbled upon a YouTube video of it being played and explained by Wil Wheaton (the actor who started out as a teenager on Star Trek, and now shows up on various television programs):
Apparently the person who starts is someone who had recently been sick, or had the worst disease. It turned out three of the players had caught H1N1 in 2009 at a gaming type convention in Seattle (link so you can understand what they mean by "Pax": http://prime.paxsite.com/ ), but one of them had suffered worse a few years before with a sequences of strep infections.
Enjoy. Just like I enjoyed learning about parasites in fish due to transporting them elsewhere.
(And I really hope that my two college age kids going to that same gaming convention don't get some kind of infection!)
I have a short bit of trivia to add to TWIP #56. You briefly discussed the topic of fish spawning and the salinity or not of the water in which the fish spawn. The question of a salty river was oh so very briefly brought up and dismissed. Well there does in fact exist a salt water river. I have been there and it is on the Island of Okinawa. The river is spring fed and the spring is so close to the ocean that the ocean water actually infiltrates the spring and it flows its extremely short length back to the ocean. It is something like 1-2km long. I have a picture burred around here somewhere but I know not where at the moment.
Vince and Dickson,
Here is a follow up on your biofuels question. To make fuels from crops succeed we need a biotech breakthrough that I really thought someone would have done already. Basically we need a bug that eats cellulose and converts it back to sugar so you can ferment it. Personally, I think there is a Nobel Prize in it for the group that creates an e. coli strain that converts cellulose to sugars. Once you have that, then you can feed the farm animals the corn and run your tractor on the corn stalks! Or you could use hay or grass clips or wood chips or waste paper, whatever is available cheaply. Until we get that bug, ethanol from corn will just be a niche technology.
People will keep pushing to use corn crops or other high sugar crops to make fuel, but the economics are not good and the lost opportunity costs are too high. Look how the modest current efforts in the USA have pushed up food prices and still required government subsidies to be competitive. No doubt there is a listener out there with lots of arguments for how great ethanol from corn is but I don't see anything like the margin needed to make it a viable market changing crude oil substitute.
I will show my age and tell you that as a senior chemical engineering design project in 1980 at Purdue, we looked at how to convert crop waste materials (like corn stalks) into fuel and it wasn't pretty. The only real way to break down the cellulose was to grind it up and treat it with hot fuming sulfuric acid in big reactors. Fuming sulfuric is 98% concentrated acid that is saturated with sulfur trioxide gas, brute force chemistry for sure! As I remember, you could get pretty good conversion of the cellulose, but the ugly part was separating the good stuff from all the waste acid and the non reactive lignin. Once you got all the acid out of the good stuff, then you still had to ferment the sugars. It is not surprising that you don't see anybody running this process to make fuel! We need a biotech solution to break down the cellulose without all the mess. I think folks were looking at the microbes in termites' stomachs as a place to start., but I have not heard of any progress on this in several years.
I will add that biofuels are not the only option for our fuel supply. For the past 100 years, we have had repeated dramatic reports that we are about to run out of oil and yet it never seems to happen! I remember a particularly detailed one in Scientific American about 10-15 years ago with beautiful graphs and everything. Each time the trumpets of doom sound, some smart engineer or geologist comes up with a new way to extract more oil. I don't see any reason why this trend will suddenly stop this time, we still have lots of tar sands, deep oil, and shale oil that have not been touched. Please note that I am not expressing a political view on the social correctness of these options just the technical aspects. Even more impressive are the reported quantities of frozen methane hydrate clathrates on the ocean floor that would likely be fairly easy to extract. Some estimates are that there is more than 10 times the amount of energy stored there than in all the oil we have ever used. Obviously none of these fossil fuels address the CO2 generation concerns that many people have.
Wind, solar, hydro and even nuclear power all have their places and I hope their niches keep growing as the technology improves, but nothing comes close to competing with chemical energy as a cheap, portable, high density source of energy. One just needs to look at biology to see the truth of this; plants fix the suns energy into chemical forms that then cascade through the food chain ever evolving into more complex forms. How cool is that!
Thanks for helping me stretch my brain each week! Thus ends "This Week in Chemical Engineering"!
Dear The Good Doctors!, I hope you are well!
I became fascinated with parasites at Uni when I was studying Freshwater and Marine Biology and took zoology and again relating to shifting global distributions of aquatic infectious organisms by climate change. I loved every aspect of parasitim but they were such small parts of my course I didn't think I could go into parasitology. I left college and went into aquaculture, listening to you all the while, which nudged me into returning to study. I'll be starting a masters in molecular parasitology at Glasgow Uni next year. I'm certain I wouldn't be, if not for you two and TWIP! I cannot express my gratitude in words for your effort and work making TWIP!
I love TWIP (et al.), I've been following it for years. However, I'm currently working at a remote pearl oyster farm in Australia (Beagle Bay, WA). As the podcast is over 50mb, my iPhone won't download it without a wifi connection. There is no wifi...
Is there anyway you can reduce the podcast file size? Without reducing the length of the show, of course!
File compression or something?
It's been months since I've had a TWIV fix and I'm starting to get the shakes!