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Letters

TWiP 79 letters

Jesse writes:

Doctors TWiP,

I came across this paper and thought it sounded interesting for a discussion on TWiP:

Colonisation resistance in the sand fly gut: Leishmania protects Lutzomyia longipalpis from bacterial infection
http://www.parasitesandvectors.com/content/7/1/329

Press release for it: www.sciencedaily.com/releases/2014/07/140723110659.htm

Thanks for your good work,
Jesse

Jesper writes:

Professors,

Thank you for your continued effort in sharing your knowledge and scientific enthusiasm. It is always a pleasure to listen to the TWIx-shows and I have learned lot from them all.

I just ran into an interesting article on how T Gondi may change the behaviour of its human host. You might find it worth reading. http://www.theatlantic.com/magazine/archive/2012/03/how-your-cat-is-making-you-crazy/308873/.

On a side note, it seems TWIP does not have facebook presence. Unless that depends on my poor searching ability you may want to consider rectifying that.

Best regards,

--Jesper

Simon writes:

Dear Professors,

Firstly I would like to share with you the attached photograph. I was in London a few weeks ago waiting to meet a friend in Cavendish Square, which is right next door to the Royal Society of Medicine. In order to kill time I was walking around the square and I noticed a blue plaque on a nearby house (they are quite common in London denoting places of historic interest). As soon as I saw it, I knew I had to take a picture to send in to you, particularly as I have recently been listing to the series of episodes on malaria from the early days of Twip.

Secondly, in a free moment I was browsing the PLOS website the other day (I think Neglected Tropical Diseases has to be my favorite journal name), and came across the following paper: Diverse Host-Seeking Behaviors of Skin-Penetrating Nematodes (http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1004305).

Interestingly, the data seem to suggest the key role of olfaction in nematode host identification, and this reminded me of your discussion on TWiP 78 of odor detection by mosquitos. The fact that both mosquitos (as carriers of malaria), and these skin-penetrating nematodes have evolved sensitive olfactory responses led me to wonder if this is a very common host detection strategy among free-living/moving parasites? Do you know of other examples?

Thank you in advance for your comments.

Simon

Anne Marie writes:

I went to Belize this summer and noticed the attached sign at a roadside tamale place. I thought you two might appreciate seeing it. I don't know if you guys speak Spanish so I thought I'd translate it as best I can:

"For a community free of Leishmaniasis

These are diseases caused by a parasite called Leishmania that transmit to humans through sand fly bites.
Wear a thick, long-sleeved shirt, thick pants, a hat with a wide brim and work boots in the forest or jungle.
Keep you house clean, ordered and free of trash and weeds.
Keep animals (including dogs and cats) out of the house, in clean, secure places.
Use fine mesh mosquito nets daily. Cover yourself after dark and cover children after 5 pm.
Go to the nearest Health Service, TREATMENT IS FREE."

Also: my dad got ehrlichiosis while orienteering in Maryland. He felt cruddy for a long time but had no lingering ill effects. (He's also been bitten by a rattlesnake!)

My best,
Anne Marie

Abe writes:

Hi,

I just started binge-listening to all the episodes of TWIV and TWIP from the beginning. These are great! As an interested scientist in a completely different field, I wanted to ask:

TWiP: Are there any examples yet of Archaea acting as parasites to hosts in the other kingdoms? If not, are there specific biochemical reasons why it would be impossible?

Yours,
Abe

Chelsea writes:

Hi Vincent and Dickson,

I hope this e-mail finds you both well! I am a big TWiP fan - the podcast is fantastic for getting good science across in an entertaining way. I'm even assigning several of your episodes to students in my "Ecology of Human Parasites" course at UMich!

I'm attaching info on an opportunity for early career scientists to present their work on "ecosystems within organisms" - any aspect of ecology and evolution of the microbiome. This Early Career Scientists Symposium will be held at UMich in late March. Many of your listeners may be excellent candidates, so I would be very grateful if you could mention the call for nominations on your next episode.

Keep up the great work!

Christophe writes:

Hi Guys,

I saw this article and thought it would interest Dickson (assuming he hasn't seen it already)

http://arstechnica.com/science/2014/11/mosquitos-evolved-to-specialize-on-human-prey/

Stephen writes:

Dear Professors Racaniello and Despommier,

I have two "corrections" for you. First, in episode 2, Prof Despommier named Darwin's Bulldog as Aldous Huxley. The correct Huxley is Thomas Henry Huxley. Aldous was a much more recent philosopher and writer of fiction.

Second, in episode 17 (Entamoeba histolytica) - which I'm only half way through - polar ice melt and consequent sea level rises were mentioned. Prof Despommier's explanation for the difference in effect of melting at the north and south poles was not really right. The real difference is that the ice at the north pole is almost all floating sea ice, so it's already displacing a mass of water equivalent to the mass of the ice - thus when the ice melts, it will have no nett effect (ignoring the warming of the water which would result in some thermal expansion). The antarctic ice, however, is most sitting on top of the vast landmass that is the continent of Antarctica. So when it melts, there will be water - and plenty of it - added to the ocean system.

I came to TWiP via TWiV (which I started listening to during the height of ebola news coverage this year). Last week I also added TWiM. I'm slowly working my way through the back catalogue. All of the podcasts have me feeling vague pangs of regret at having left science after graduating. Thank you for making great shows that are accessible, entertaining and educational all at the same time.

Regards,
Stephen

TWiP 78 letters

Meliani writes:

Dear Sir,

My research is focused on the biofilms formation, Motility (swarming and swiming ) and QS in fluorescent Pseudomonas (P. aeruginosa and P. fluorescens).

In laboratory a interaction had been with insect and bacteria metaboliye EPS (so a Bacteriophile insect).
I do not know the identity of this namtode, is a parasitism interaction? or symbiosis one , to interprete my figures.
Please could you give me it name?

Hope to read you, I ask you to please accept my best wishes.

Thank you very much for Reading my message.

Best regards

Dr. Meliani

Microbial Ecology Professor researcher at the University of Mascara, Algeria

Peter writes:

Dear TWiP team
I saw this report on the BBC and thought it may be worth a mention on TWiP:

A woman was horrified to discover that her nosebleeds had been caused by a leech living in her nostril. Daniela Liverani from Glasgow started having persistent nosebleeds after a backpacking trip around South-East Asia, At first she thought her nosebleeds the result of a motorcycle accident but sought medical assistance when she noticed the nosebleed "had ridges" and had started "poking out" of her nose and wriggling.

http://www.bbc.co.uk/news/uk-scotland-29595164

Regards

Peter writes:

Dear Dickson and Vincent.

I recently finished reading Dickson's book "People, Parasites, and Plowshares'.
Looking for further information on the topics covered in the book I found this paper reviewing studies of the effects of helminth infection in reducing the rejection of transplanted tissue.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3940291/

Maybe it could be discussed on TWiP, or be a listener pick of the week.

I would also like to recommend the Coursera course Epidemics - the Dynamics of Infectious Diseases
which I am sure would interest TWiP and TWiM listeners.

Regards

TWiP 77 letters

Andy writes:

Dear Professors,

I have been following TWIP for several years. I am a software engineer and parasitology is only an avocation. As an undergraduate in the early 80's I discovered my love of history of science and ecology, although I continued the path of a software developer. As an adult I read Carl Zimmer's Parasite Rex and became totally fascinated with parasitology. Later I read The Coming Plague by Laurie Garrett. What I love about both Mr Zimmer's and Ms Garrett's writing is how they tie the science to the scientist. I look at The Coming Plague as a masterpiece in history of science with really touching stories of the scientists and their impact on the world.

I'm writing to ask you to make sure that when you talk about the science of parasitology, you keep including the stories of who figured out what and why it was important. The two of you bring a lot of experience in parasitology, microbiology, and virology and have lived the history of it--keep the stories coming!

If you haven't watched this, I recommend that you do. It's a lecture by Prof Walter Munk on his life's work in the field of oceanography. Fascinating!

http://www.uctv.tv/shows/Where-the-Swell-Begins-24248

Andy
Saint Paul, MN

P.S. I also recommend the book Krakatoa: The Day the World Exploded as a great book with history, anthropology, and science all tied together with history of science.

Mike writes:

Bobbi Pritt was a superb guest. As Vincent commented, 'now we get to hear the pronunciations of the parasites' or something along those lines which I also found helpful. I had almost given up on this podcast because it seems to lack focus and rambles a bit. Hope you are able to get more people like Bobbi on your show.
Mike in Oregon

Kyrie writes:

Hi Dixon & Vincent,

Recently I got a wonderful pug puppy from a local puppy mill store ( which I know no one should ever do but I had just lost another dog that was with me for 12 years and I walked by not a puppy trap not in a rational state) the puppy it turns out has demotic mange.

I had read about an oil from India called neem that by some mechanism blocks the reproduction if bacteria, parasites, fungus everything!

I put it on my dog and weird white things started coming off within a half hour. I dusted her off and they came back again 4 times. What is that? I also wash her twice a week with Borox and vinegar.

What do you know about neem oil and its effects on the parasitic life cycle and what can you tell me about demotic mange and their behavior ?

Anything would be helpful. The dog I bought is super cute but has many health issues so I am trying the natural path to reduce complexity.

Also a side note Vincent your are wonderful and fascinating but why so hard on your good friend Dixon?

He seems like such a sweet person sometimes I want to yell as the podcast at you leave him alone!

BTW: I listen to all the twi + x podcasts as I go to sleep every night! Best science podcasts out there. Thank you and all the wonderful people on the show for giving the lay people a little real science.

As a side note, I am a software developer that has zero to do with microbiology outside of the fact that it effects us all. Thank you for the peek into the very small universe it's really fascinating.

I am so grateful!

Thanks for everything you do,

Kyrie

Rebeka writes:

Hello Doctors,

I have just started listening to TWiP and am on episode 20 currently. I had a couple things I wanted to share and I apologize if these are things you have already covered in more recent episodes. First in the episodes regarding Giardia and Entamoeba histolytica it was stated that these are not reportable. Being a Medical Laboratory Scientist (once called Med tech) I do report these to the local health department when we recover them. I live in Michigan, so maybe the regulations are different where you are. I have attached a copy of the MDCH reportable diseases for you.

Also, when I was an undergrad I read an article about a vaccine that targeted the gut of ticks, so that when the tick took a blood meal from an animal the antibodies would be ingested as well and kill the tick. This reduces the amount of ticks in an area and the overall tick borne diseases. I did a quick search and sure enough this research is still going on! What do you think about the possibilities of a vaccine similar against say mosquitoes? Ticks take a larger blood meal, so it might not work, but it is still an interesting idea. Here is the link to the current work :http://www.parasitesandvectors.com/content/7/1/77

I absolutely love the show! I also teach Microbiology to Medical Laboratory Technicians at a community college and I am going to recommend this podcast for them to prepare for their board of certification exams.

Thank you again for the fantastic show.

Rebekah MLS (ASCP)

Erica writes:

Hi

I'm a Zoology graduate currently working in a parasitology lab and applying for molecular parasitology PhDs in Ireland.

Recently found your podcast and really enjoying listening to it in the lab.

Wanted to say thanks, I was surprised at the lack of parasitology podcasts out there and I'm glad you have it covered :)

Would enjoy it if you delved into some parasites of agricultural importance such as PPNs.

Keep it up

Regards

Erica

Alex writes:

Hi guys

Love your twip. Dickson, you mentioned in Twip 76 that H. polygyrus is the best model we have for human hookworm. You might be interested in this paper attached that we recently published which highlights how similar Nippostrongylus and Necator really are in terms of their biology and secretomes. I now think of Nippo as a better model for human hookworm infection than H. poly. Keep up the great work on the show! Thoroughly entertaining and informative.
Cheers
Alex Loukas

Professor Alex Loukas, PhD
NHMRC Principal Research Fellow
Director, Centre for Biodiscovery and Molecular Development of Therapeutics
Australian Institute of Tropical Health & Medicine
James Cook University
Cairns, Australia

Robin writes:

Dave from Fresno (that's where I live!) in your emails suggested that DVT may embolise to the brain. If it does, it would indicate an atrial septal defect or a ventricular septal defect: the emboli are too big to traverse the pulmonary capillaries.

Also aspirin and other antiplatelet agents are primarily effective against platelet thrombi, which are aggregations of platelets, like snowdrifts, at sites of rapid flow, viz. arteries. Such thrombi are friable, adherent, and less likely to detach en masse. DVT is more akin to a blood clot in a test tube.

Multiple ring forms of the malarial parasite in an erythrocyte is indicative of Plasmodium falciparum infection.

TWiP 76 letters

Daniel writes:

Dear Vincent and Dickson,

I just returned from the annual meeting of the International Society of Travel Medicine (ISTM) where I enjoyed many fantastic lectures and caught more Cutthroat Trout fly fishing the upper Snake River during one evening than I could count. I will confess to using a hopper with a bead head dropper to achieve this. I was relaxing on this beautiful Sunday morning with a cup of coffee in hand and the August 1st issue of Science. To my delight I saw that the cover had a colorized scanning micrograph of a dog roundworm (Toxocara canis). This image on the cover directed the reader to a commentary and to two research reports about how infection with parasites influences the immune system in such a way that antiviral immunity is impaired.

I am an MD trained as an infectious disease specialist and am active in the care of immigrants, travelers and indigent patients suffering from infectious diseases. At NYU School of Medicine I received excellent training in parasitic disease from a dynamic visiting professor that has served me well in China, Africa, Nepal and here in the states. My PhD is in Immunology and my early work involved defining the phenotype of human B1 cells, an innate subset of B cells. My current work is on HIV latency in hematopoeitic stem cells. These research reports were thus as they say ‘right up my alley’. The commentary is readily accessible to a broad audience and explains how the two research reports demonstrate that helminth infections induce viral exit from a latent state. The two research reports contain the expected rigor one sees in Science.

These reports seem a perfect crossing of both your areas of focus, Vincent’s expertise in virology and Dickson’s expertise in eukaryotic parasites. Schistosoma mansoni is one of the parasites involved in the first article and one even my kids know about after swimming in Lake Malawi this past winter. Trichinella is used in the second paper and is not only dear to Dickson’s heart but something we still see up in Alaska, where I worked until recently. To fully disclose my fascination with parasites, the discussion my physician friend from Alaska and I were having as we caught cutthroat trout on the Snake last week was about the two cases of acute Trichinosis that he recently managed in a married Alaska couple from eating undercooked bear meat.

I am left thinking that Dickson needs to fish the upper Snake River in Wyoming, but more importantly he might consider writing a monograph entitled not People, Parasites & Plowshares but: Parasites: When Plowshares become Swords!

Sincerely,

Daniel Griffin, MD PhD
Associate Research Scientist
Department of Biochemisty and Molecular BioPhysics
Columbia University

Francois writes:

Vincent, you’ve got French listeners, at least one!

I'm living in Montpellier (south of France) were the sun is shining.

Here two very visuals picks of the week.

You already know of the glass virus of Luke jerram, but here the malaria model
http://www.lukejerram.com/glass/gallery/malaria

And also for sheer beauty ... Giant glass flower from Jason Gamrath
http://www.demilked.com/gigantic-glass-flowers-jason-gamrath/

François

Robin writes:

Various items

Malaria prevalence
Can be so high that asymptomatic parasitaemia is the norm: it was 95+% among adults of some New Guinea tribes and over 70% among the adults in the territory of Anopheles gambiae.

French speakers
Among the reasons I am not a French speaker were Horatio Nelson and the Duke of Wellington, to neither of whom I have any affinity or allegiance. But they were among the reasons that the Raj was a British Raj, and not a French one. An important reason also why so many Indians (& Pakistanis) speak adequate if not good English, and little or no French.

Schizont pronunciation
http://www.thefreedictionary.com/_/dict.aspx?word=schizont

Single vs multiple ring forms
Multiple rings in an RBC is bad news.

Parasites are doomed
As in the answer to the question about Bob Dole in the 1996 presidential election - "Does he wear boxers or briefs?": "Depends". Those that adapt well enough may become a necessary feature, as Dr. Dickson has explained with regard to intestinal parasites and autoimmune disorders of the gut (and perhaps elsewhere). And let's not forget the bacterium that invaded an Archean to produce the great*gazillion grandparent of all of today's eukaryotes. Mitochondria are no longer parasites.

Extra membrane protein in RBC cytoplasm
One reason for it may be to prolong the life of the RBCs. Think of a tire filled with tread that can migrate to the outside as the tread on the outside is worn away. RBCs are subject to plenty of wear as they squeeze through narrow capillaries.

Movement of Homo sapiens and other hominids outside Africa Extincted by human disease
There were two (known) non-sapiens lineages outside Africa in later times that we met: neanderthals and denisovans. We may have also met floresiensis but there is no genetic evidence for commingling. Just about all other hominid species were in Africa and were exposed to the infective load found there. Moreover, we coexisted with Neanderthals for ten millennia or more.

Within our species 14 disease-free millennia after crossing the Bering land bridge into the New World and several more disease-free millennia preceding in Siberia helped to make Native Americans susceptible to smallpox and measles, thus enabling settlement of vacated territory by Europeans who brought those diseases as naturally as their ectoparasites.

Homo habilis evolved into Neanderthal
I had the impression that it was a more advanced form: Homo heidelbergensis.

Colder climate - invasive species
The hairless ape is adapted to year-round tropical weather. Anywhere else it is an invasive species: to survive elsewhere it has a cultural/technological adaptation that proceeded much faster than evolution: shelter & clothing.

Cause of migration civil war
Not necessarily. It would be doubtful whether the migration across the Bering land bridge was due to civil war. The migration of Jews out of Europe in the time of the Third Reich was not quite due to "civil" war. Or of Armenians out of their lands annexed by Turkey.

Extravasation
Coming out of a vessel (vas=vessel). Could be a tubular vessel such as for blood or lymph, but also a sac-like vessel such as for urine or bile. Malarial parasites coming out of an RBC don't quite cut the mustard.
A reminder for the upcoming podcast:
Ask parasitologist from Mayo clinic about lice & anemia.

My personal guess is that it would not be due to depletion by volume, but perhaps the adaptation of the body of some substance injected by the lice to act as a signal that causes the body to make the blood less nutritious.

And in case Dr. Dickson wants to know what she looks like:
http://instagram.com/p/XScFXyvaOy/

David writes:

Dear Vince,
Long long flight, yes.
What is a chief, but invisible, physiodynamic consequence of even short flights?
Deep vein thrombosis in lower extremities. Cuts loose as ambulating off plane. Throws embolis to lungs, even heart, brain. Pulmonary embolism is a big deal.
Prophylaxis? Wiggle your feet, ankles, calves regularly. Venous return is passive, and hydraulically driven by muscle massage of lower veins in the course of everyday activity.
Lack of activity lets blood accumulate above vein valves. Leg bent at knee, and dependent, further kinks veins. Unmoving blood begins clotting, especially in guys of a certain age. If not troubled in flight, they then walk off plane and collapse.
To prevent, extend legs, and isometrically flex and extend them even when bent. Get up and about in flight at any excuse, and for none.
Alcohol may repress clotting some. At minimally higher risk of uncontrolled bleeding, a bit of aspirin probably wouldn't hurt. Bloody Marys are nutritious.
Travel well. Wish I were there.
Dave
Fresno

Tristen writes:

Dear Vincent and Dixon,
I'm not sure if you got my email a few weeks ago since I sent it from my personal email and not through the website so I'm sending it again just in case.

I have to tell you that I'm a huge fan of TWiP and I love listening to you guys! In November 2013 I did my first medical mission trip to Nzara, South Sudan. Vincent you probably already know an interesting virology fact about Nzara- it's one of the first places Ebola virus was discovered in 1976. After the short trip I enjoyed the work so much that now I am trying to gain funding so I can leave life here and continue the work in Nzara for a couple years. I appreciate how your podcasts are both educational and entertaining at the same time. My favorite one so far is when you had Peter Hotez on talking about neglected tropical diseases.

You guys should really do an episode about chronic malaria infection in children living in sub Saharan Africa and the connection between Epstein Barr virus and the high rate of pediatric burkitts lymphoma diagnosis. People get tired of hearing about malaria, but this would be a great podcast because it combines parasitology and virology. I find it quite interesting and happen to learn about this connection when I had plasmodium malariae after returning from my trip (despite taking malarone). Thank you both for your good work and for giving me such valuable information which I can take back with me to South Sudan!

Malaria-EBV-lymphoma research:
http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.0030080

http://www.newscientist.com/article/dn12033-malaria-linked-to-child-cancer-in-africa.html#.U53aWye9KSN

Truly,
Tristen

Zephyr writes:

Hello, Doctors Vincent and Dick,

In the episode TWiP 73 (Entamoeba histolytica) I heard the following misconception:

Dick Despommier: (44:33) "Name a mammal that has nucleated red [blood] cells. Camels." (44:35)

In spite of their rather peculiar elliptical shape and other abnormal features (see below), camelid red blood cells are by no means nucleated:

"The elliptical, anucleate erythrocytes of camels have been examined for the presence of marginal bands and their constituent microtubules. Lysis of erythrocytes under microtubule-stabilizing conditions readily revealed marginal bands in at least 3 % of the cells, as observed by phase-contrast and darkfield light microscopy. Microtubules plus a marginal band-encompassing network of material are visible in lysed cell whole mounts with transmission electron microscopy. Marginal band microtubules are also evident in electron micrographs of thin-sectioned camel erythrocytes identifiable as reticuloyctes on the basis of submaximal electron density (reduced haemoglobin iron content) and presence of polysomes. The results suggest that marginal bands may be involved in morphogenesis of camel erythrocytes but are not required for maintenance of their ellipticity after cells are fully differentiated."

“Among the mammals, members of the family Camelidae (camels, vicunas, guanacos, llamas, alpacas) are unique in that their erythrocytes, though anucleate, are elliptical (Andrew, 1965). The question thus arises as to whether MBs play a role in cell shape generation and/or maintenance in these species.”

— Cohen WD and Terwilliger NB. "Marginal bands in camel erythrocytes." J Cell Sci (1979) vol. 36 pp. 97-107
Open access: http://jcs.biologists.org/content/36/1/97.long
http://www.ncbi.nlm.nih.gov/pubmed/457820

More pics of camelid red blood cells, this time from one of the camel’s close relatives, llamas:

• Azwai SM et al. "Morphological characteristics of blood cells in clinically normal adult llamas (Lama glama)." Veterinarski arhiv (2007) vol. 77 (1) pp. 69-79
Open access: http://hrcak.srce.hr/file/39723
http://hrcak.srce.hr/index.php?show=clanak&id_clanak_jezik=39723
http://www.vef.unizg.hr/vetarhiv/papers/2007-77-1-9.pdf

It seems to be a rather widespread confusion in educational circles, I also succumbed to this false notion during my undergraduate years. Then one day I decided to look up the possible advantages that could offer the presence of nucleated cells in camels. My wild guess was that perhaps those red blood cells could work in tandem with their also rather peculiar subset of homodimeric immunoglobulins G to keep at bay particularly harmful parasites that might have infested those animals at some point. It turned out that it had nothing to do, and the characteristic elliptical shape of their red blood cells are thought to be an adaptation to extreme dehydration and rapid rehydration, and possibly to increase the efficiency for carrying oxygen at high altitude:

In camels (Cohen and Terwilliger):

“The occurrence of MBs in camel erythrocytes is possibly correlated with ontogeny of distinctive physiological properties. Camels are adapted to survive extreme dehydration and rapid rehydration. Their erythrocytes can withstand considerable osmotic stress, responding in a manner more similar to the elliptical, nucleated erythrocytes of non-mammalian vertebrates than to the biconcave diskoidal cells typical of other mammals (Ponder, 1942; Trotter, 1956). Camel erythrocytes are highly resistant to hypotonic haemolysis (Perk, 1963; Yagil, Sod-Moriah & Meyerstein, 1974), exhibit a low rate of water transport (Naccache & Sha'afi, 1974), and are also relatively stable under hypertonic conditions, in which crenation was not observed (Yagil et al. 1974). In addition, very young camels (6 months or less) apparently possess 2 populations of erythrocytes with respect to osmotic resistance: one population with adult-type response, the other with still greater haemolytic resistance (Pe
rk, 1966). Direct studies of the possible correlation between occurrence of MBs and osmotic resistance in camel erythrocytes would therefore appear to have potential value for understanding MB and erythrocyte function.”

In llamas (Azwai et al.):

“Llamoid erythrocytes were small (7.32 ± 0.95 × 3.9 ± 0.52 μm), elliptical, flat and their counts obtained in the present study (10.3 to 15.0 ×106/ μL) were higher than those in other domestic animals (FELDMAN et al., 2000). The flat shape and the presence of the few folded erythrocytes were attributed to the low thickness to diameter ratio of llama red blood cells (VAN HOUTEN et al., 1992). The small volume resulted in a high concentration of erythrocytes for any given PCV. The high MCHC of llama (38.6 to 48.0 g/dL) in comparison with those in other species might be due to the flat nature of the erythrocytes, which allowed more space for haemoglobin molecules to increase their efficiency for carrying oxygen at high altitude (HAWKEY, 1975). It was evident that llama bone marrow, unlike other ruminants except dromedary camels (MOORE, 2000), was normally releasing immature erythrocytes, including polychromatic rubricytes, metarubricytes (0.8%) and reticulocytes (0.4%) i
nto circulation.”

“In general, the unique elliptical, flat camelid erythrocytes facilitate their movement in capillaries at times of dehydration in arid areas, (SMITH et al., 1979; SMITH et al., 1980) minimizing the likelihood of sludging.”

Sincerely,

Zephyr

Curtis writes:

Maybe you've already done a segment on Toxocara and it's hidden under a clever title, but if you haven't done one so far, would you consider doing a podcast?

I just discovered TWIP and what a treasure trove it is! Thanks for all your efforts.

Best,

Curtis

John writes:

Dickson sometimes mentions how crows eat roadkill. They eat the contents of the animal's intestines, rather than its parasite-infested organs. I witnessed a crow eating a California Ground Squirrel and Dickson's explanation helped me understand that the crow was not playing with its food, but rather being picky.

I shot a video, which may be too graphic for some listeners:

https://www.flickr.com/photos/31715949@N00/9653686629>

Technically my crow is a raven, which is a fancy name for a crow with a big beak.

 

TWiP 75 letters

David writes (re lice and iron):

All I remember that I know is that one time I let my cat endure a heavy flea infestation for an unconscionably long time. I redeemed myself, if at all, by the knowledge that I slept with her a lot, and so endured a share myself (but I'm extraordinarily thick skinned, so it wasn't so bad, and I didn't get plague).

Anyway, the situation's gravity was brought home to me when I discovered that she was significantly anemic. Clearing the fleas and maintaining her freedom from parasites of any kind found the anemia gone and blood restored to a normal hct, hgb after a few months. In other words, the insects consumed a significant quantity of blood.

Lice aren't fleas of course, and people are bigger than cats, so I don't know if the lady who corresponded with you about her and her daughters' lice and her longstanding iron supplementation will have her case at all illuminated by my anecdote, but I do know that fleas can drain a consequential amount of blood from some of us.

What do you think?

Yours,
Dave
Fresno

TWiP 73 letters

Robin writes:

Liquids

Liquids are capable of forming a gas-liquid interface: maintenance of the surface requires adequate pressure in the gas. Adequate in this instance means a gas pressure greater than the vaporisation pressure in the liquid. The gas pressure is a sort of cork preventing the liquid from boiling away.

The vaporisation pressure increases with the temperature. When the vaporisation pressure equals the gas pressure, the liquid starts to boil. In the absence of any gas pressure, a liquid-gas interface cannot be maintained: that is why astronauts' blood would boil if they are exposed to the vacuum of space.

Also in the vacuum of space, when a solid is heated to its melting point it will convert directly into gas, the process being known as sublimation. In earth's atmosphere if the solid's vaporisation pressure at its melting point is greater than the atmospheric pressure, it will transit directly from solid to gas, as in the case of carbon dioxide.

Toads vs. frogs:

While toads are not a taxonomic group, use of the word "toad" implies the exclusion of or differentiation from frogs.

Toads tend to be more terrestrially adapted, with a dry skin, no cutaneous respiration, no webbing between the toes, and spending most of their adult lives on terra firma.

Reptiles are a paraphyletic group:

http://en.m.wikipedia.org/wiki/Paraphyly

“a group is said to be paraphyletic if it consists of all the descendants of the last common ancestor of the group's members minus a small number of monophyletic groups of descendants, typically just one or two such groups. Such a group is said to be paraphyletic with respect to the excluded groups. For example, the group of reptiles, as traditionally defined, is paraphyletic with respect to the mammals and birds: it contains the last common ancestor of the reptiles—including the extant reptiles as well as the extinct mammal-like reptiles—along with all descendants of that ancestor except for mammals and birds. ”

Dinosaurs are tossed into the reptilian bin, but if they had been around to think and opine about it, they might have demurred:

http://en.m.wikipedia.org/wiki/Reptiles

“In addition to the living reptiles, there are many diverse groups that are now extinct, in some cases due to mass extinction events. In particular, the K–Pg extinction wiped out the pterosaurs, plesiosaurs, ornithischians, and sauropods, as well as many species of theropods (e.g. tyrannosaurs and dromaeosaurids), crocodyliforms, and squamates (e.g. mosasaurids)."

Infraclass Archosauromorpha
Order Prolacertiformes
Division Archosauria
Subdivision Crurotarsi
Superorder Crocodylomorpha
Order Crocodilia
Order Phytosauria
Order Rauisuchia
Order Rhynchosauria
Subdivision Avemetatarsalia
Infradivision Ornithodira
Order Pterosauria
Superorder Dinosauria
Order Ornithischia
Order Saurischia

Dinosaurs are lumped with reptiles:

http://en.m.wikipedia.org/wiki/Dinosaur

“Although the word dinosaur means "terrible lizard", the name is somewhat misleading, as dinosaurs are not lizards. Instead, they represent a separate group of reptiles that, like many extinct forms, did not exhibit characteristics traditionally seen as reptilian, such as a sprawling limb posture or ectothermy.”

"Ship's captains flaunting this"

Flaunt:

http://www.thefreedictionary.com/_/dict.aspx?word=flaunt

v.tr.
1. To exhibit ostentatiously or shamelessly: flaunts his knowledge. See Synonyms at show.
2. Usage Problem To show contempt for; scorn.

Flout:

http://www.thefreedictionary.com/_/dict.aspx?word=flout

v.tr.
To show contempt for; scorn: flout a law; behavior that flouted convention. See Usage Note at flaunt.

John writes:

Dear TWiP Team,

On the latest episode you insinuated perhaps that the host was chosen for his looks and why couldn't they find someone that actually studied parasites. Well, as it happens, the host, Dan Riskin, just did an AMA (ask me anything) on reddit.com His expertise and passion is actually bats but he has become a science communicator full time.

When asked how he ended up as a science presenter his response was this:

"I was working as a scientist in a basement, when the phone rang. A production company was doing a show about evolution (called Evolve, for the History Channel), and they needed "an evolutionary biologist who is not an old man." They'd gotten my name from someone who had seen me give talks at conferences."

http://www.reddit.com/r/IAmA/comments/26p2ge/im_dan_riskin_biologist_turned_animal/

So yes, he was picked for his looks! Showbiz.

Best,

John

 

Robin writes:

Greetings Vincent and Dickson,

A quick note from one of your probable many silent listeners. I am enjoying the TWIV and TWIP podcasts very much! Great learning to supplement my background in ecology and public health. Quick followup on the meaning of "invasive". I think the student of ecology (Vincent) got this one right over the teacher (Dickson). I believe invasive does mean it takes over and outcompetes native species, whereas exotic is something occurring where it isn't natural. There are exotic species that are not considered invasive, although it is probably a matter of degree since any exotic species would compete with natives for resources at some level. Perhaps, that is what Dickson was implying?

Keep up the great work.

Robin

Ecologist

Missoula, MT

Bobbi writes:

Dear Twip group, first I'd like to say that I love your program - great work! Second, I wanted to introduce you to my Parasite Case of the Week blog at http://parasitewonders.blogspot.com

We just hit our 300th case. It's a simple blog - short cases and short answers the following week. I'd be happy to talk to you about it if you're interested. Best wishes,
Bobbi

Bobbi Pritt, MD, MSc, DTMH
Director of Parasitology
Mayo Clinic
Rochester, MN

John writes:

Hello,

iTunes says it has been almost a month since your last episode. It is spring (15 C in Massachusetts) and time for you to emerge from hibernation.

I wanted to call your attention to two related papers on nonhuman parasites. I mean, parasites infecting nonhuman hosts.

I was disappointed to learn from an early TWiP episode that tapeworms do not cause ravenous hunger. So my parents were wrong about the reason for my appetite as a child.

Some rodent biologists (that is, human biologists studying rodents) got to wondering what parasites did to the appetites of their favorite mammals.

Researchers treated African ground squirrels with ivermectin and fipronil. Treated squirrels stopped itching and spent more time eating. Surprisingly, they did not gain weight. Parasites had depressed the squirrels' resting metabolic rate. Parasite-free squirrels had to eat more to maintain normal weight.

Despite not gaining weight, treated squirrels did have a lot more babies. So they were healthier.

Now when is Merck going to donate a billion doses of ivermectin to the squirrels of the world?

References:

Scantlebury M. et al. 2007. Energetic costs of parasitism in the Cape
ground squirrel Xerus inauris. Proc R Soc Lond B Biol Sci
274:2169-2177.

http://rspb.royalsocietypublishing.org/content/274/1622/2169.full

Hullegass, M. et al. 2010. Parasite removal increases reproductive
success in a social African ground squirrel. Behavioral Ecology
21(4):696-700.

http://beheco.oxfordjournals.org/content/21/4/696

Cape Ground Squirrel on Wikpedia

http://en.wikipedia.org/wiki/Cape_ground_squirrel

Johnathan writes:

Dear Drs. Racaniello and Despommier,

Thanks for the wonderful job you do with TWIP and TWIV. I appreciate all the time and effort you put into the podcasts and look forward to each new episode.

I was wondering why you haven't yet given much if any attention to bed bugs on TWIP? They're arguably the most important human parasite in the United States and growing at an alarming rate. Twenty years ago bed bugs were extremely rare in the United States, but now cost the US economy an estimated $3 billion annually. The emergency department where I work is forced to close and decontaminate a main-treatment area room approximately every three days for an average of 17 hours at a time due to a bed bug being found on a patient. While bed bugs are not vectors of human disease, they can cause itchy rashes and less commonly asthma and angioedema. Bed bugs are also associated with depression, social isolation, suicidal ideation, anxiety, nightmares and other mental health concerns. Of all the parasites you reasonable could acquire in the United States, bed bugs would have to be the least desired given their itchy bites, social stigma, difficulty with diagnosis and treatment, and the time and costs associated with eradicating them. The CDC neglected to place bed bugs on their list of the top neglected parasitic infections yet I can't think of a human parasite which more adversely affects the health and well being of Americans than bed bugs. Any thoughts?

Thanks and keep up the wonderful podcasting!

-John Sheele

Johnathan Sheele, MD, MPH, MHS
Assistant Professor, Department of Emergency Medicine
Associate Fellowship Director, Global Emergency Medicine
University Hospitals Case Medical Center
Case Western Reserve University

Jim writes:

Nothing new here, but it's in your region, so just in case it's of use: Ticks in NY

Jim, Smithfield, VA

Heather writes:

Hi Dr.s R&D!

Just a quick clarification: all invasive species are exotic species, but not all exotic species are invasive. Invasive species generally cause ecological, health, or economic problems. Dr. D.'s beloved trout are exotic across much of their current global range. In many areas where non-native trout, such as rainbows, have been introduced they are not considered invasive but they are exotic. Large and smallmouth bass are in a similar situation. However, brown trout in public waterways in the US are considered invasive. Pike in Alaska salmon rivers are one of the most recent and serious human-caused aquatic invasions.
Regards,
Heather

Scott writes:

Dear Dick and Vincent,
Sarcoptic mange is having a significant impact on the current wolf population in the Yellowstone area. In addition mange is also affecting the fox and coyote population in the front range of Colorado, and I suspect the problem extends even further. I think people would enjoy listing to a program on mange. Where did it originate, is it the same scabies mite humans can get? I also have photographs of fox and coyote with mange you could post on your website.
Thanks
Scott

Greg writes:

Greetings professors,

I am a soon-to-be first year veterinary student and long-time lover of parasitology. I just discovered TWiP and am working my way through the early episodes, where you discuss, among other things, the discovery of Trichinella spiralis. You mention Paget and Virchow, but do not mention Joseph Leidy. Leidy, a noted anatomist, paleontologist, parasitologist, and overall polymath (and one of my favorite scientists) is often credited with the discovery of encysted worms in pig flesh. In 1846 (several years before Virchow's work), Leidy made the connection between undercooked pork and human trichinosis, and advocated for the thorough cooking of meat before consumption. Apologies if you touch on this subject in a later episode. I'm working through them as fast as I can! Big fan of the show.

~Greg

 

 

TWiP 74 letters

 voxsciurorum writes:

Dear water-based life forms:

It is 24 degrees in Overland Park, Kansas and I am looking at a slide labeled "Giardia lamblia", part of a museum exhibit on water and human (over) use of water.

I see a greenish lump. I don't know if it's alive. I was not meant to be a diagnostic technician.

The exhibit is produced by AMNH and/or water.org, and located in the Museum at Prairiefire (museumofpf.org). It may be interesting to listeners in the Kansas City area.

Heather writes:

Hi Dr.s R & D!

I think I recall one of you mentioning a younger relative enjoying the game Plague, Inc. during a podcast somewhat recently. With this vague notion in mind I downloaded the game and have been enjoying it ever since. Normally I don't like electronic games, but this one seems to use some very accurate algorithms to simulate the spread of various real and imaginary pathogens, with the ultimate goal of the player being the total annihilation, or enslavement, of humanity. The game is played from the perspective of the pathogen and DNA is the "currency" of the game, which I thought was very clever. Most of the "science" the game is based on seems to be quite well-researched also. I think a discussion of the game, from the viewpoint of scientists who work with microbes and pathogens, would make for a very interesting TWiM or TWiV (there are many kinds of pathogens, besides parasites, including viruses. I have good luck winning with both, even on the "brutal" level of difficulty).

I have just subscribed to Urban Agriculture. I have no idea how I will keep up with four podcasts now! I have no idea how Dr. R. keeps up with four of them! I can keep on top of TWiP and TWiM easily enough, since that is my background but I sometimes have trouble with TWiV, since I only have the most elementary virology background. Perhaps a virology primer, like the early episodes of TWiP, would help me and other listeners who don't know a ton of virology?

Thanks for the great podcasts!

Regards,
Heather

Tristen writes:

Dear Vincent and Dixon,

I have to tell you that I'm a huge fan of Twip and I love listening to you guys! In November 2013 I did my first medical mission trip to Nzara, South Sudan. Vincent you probably already know an interesting fact about Nzara is that it's one of the first places Ebola virus was discovered in 1976! After the short trip I enjoyed the work so much that now I am trying to find funding or sponsorship to leave life here and work in Nzara for a couple years. I appreciate how your podcasts are both educational and entertaining at the same time. My favorite one so far is when you had Peter Hotez on talking about neglected tropical diseases.

I want to request you guys do an episode about chronic malaria infection in children living in sub Saharan Africa and the connection between Epstein Barr virus and the high rate of pediatric burkitts lymphoma diagnosis. This would be a great podcast because it combines parasitology and virology! I learned about this connection after having malaria myself after my trip and find it very interesting. Thank you both for your good work and for giving me such valuable information which I can take back with me to South Sudan!

Truly,
Tristen

If you are interested in seeing the page about my work, visit here:
www.facebook.com/berawenzara

Claire writes:

Hi Dickson and Vincent,

I wrote to Twiv recently but had to also write in here to let you know that without your podcast I would have been totally lost last month when I heard a series of talks on some of the more "popular" parasites (tryps, leishmania etc). I didn't know an amastigote from a billy goat before studying up with your podcasts. Thanks for the help!
-Claire in Seattle

Jim writes:

Here's a link to a short story in our local "Daily Press" for the Norfolk area, about a museum in Tokyo about parasites. Perhaps it's provide Prof Despommier a side trip one day when he's in that part of the world. - Jim; Smithfield, VA

Museum might put you off sushi for a while

For something educational to do before lunch, I admired bottle after bottle of pickled parasites. Some frilled. Some with suckers. Most hermaphrodite. And all gross...

Suzanne writes:

I found lice in my 7 year old's hair about a month ago. My 11 year old had been asking me to check her hair for months and I never could find anything. Checking more closely with a lice comb revealed she did have them. A quick comb through my hair came up positive, too. Yay. Lucky for my husband, he keeps his head shaved.

There was a funny thing I noticed, though. I had been taking a low dose of iron daily and can pretty easily tell when I'm... eliminating... the extra and ought to skip a day or so or when it's all being used up. As soon as we shampooed and combed out the lice, I stopped using all the iron.

Remembering your comments on hook worm and anemia, I looked up lice and anemia. Google had links to a few cases where kids who were very infested showed up at doctors' offices or hospitals with severe anemia that had no other cause the doctors could find. This and the information about lice that mentioned some people have asymptomatic cases (evidently the itching is due to an allergy, not their bites) made me wonder just how long we had all been infested. I've had off and on times of slight iron deficiency since I was pregnant with my youngest and my oldest was in preschool. That's not too uncommon in women and I'm healthy otherwise. This could be totally coincidental, I know, but it's making me wonder.

I'd love to know if anyone has studied how prevalent lice are in the US. I'm starting to suspect that quite a few of us could carry them around in low numbers and not know for... maybe years? It does seem, like bed bugs, that lice are turning up more. At least around here in Central Texas where the weather is barely even worth mentioning. It's summer so it's hot. Seriously hot. But we've been getting more rain this year so that's something.

Peter writes:

Dear TWiP team,
I thought this report from The Lancet Infectious Diseases may be worth a mention:
http://www.thelancet.com/journals/laninf/article/PIIS1473-3099%2814%2970794-7/fulltext

Evidence of schistosomiasis has previously been found in 5200-year-old Egyptian mummies, that date has been pushed back a thousand years by the find of a flatworm egg in a grave at a Neolithic settlement site in northern Syria.

Piers Mitchell at the University of Cambridge and his colleagues examined sediment collected from beneath the pelvises of 26 skeletons, all between 6500 and 6000 years old. In one 6200-year-old sample they found a 130-micrometre-long flatworm egg that belonged to one of the species responsible for schistosomiasis.

More information on the Tell Zeidan site:
https://oi.uchicago.edu/support/tell-zeidan-syria

Regards

Rabbit writes:

I just started listening a couple weeks ago, so I'm not caught up yet, but TWiP is the best science podcast I've found. It's so hard to find resources for laymen about parasite that aren't full of misinformation. I've been teaching myself about parasites for a while (I'm autistic, and they're one of my special interests). As is the case with many subjects, it's hard to find resources about parasites that appeal to an audience that's not made up of either experts or complete novices. It's easy to find very basic information, and it's not too difficult to find academic resources, but TWiP is by far the best resource I've found for my level of knowledge.

I have a question: I've read that cat owners aren't significantly more likely to be infected with toxoplasma gondii than people who don't have cats. Is that true, and if so, why/how do you suppose that is?

 

TWiP 74 letters

voxsciurorum writes:

Dear water-based life forms:

It is 24 degrees in Overland Park, Kansas and I am looking at a slide labeled "Giardia lamblia", part of a museum exhibit on water and human (over) use of water.

I see a greenish lump. I don't know if it's alive. I was not meant to be a diagnostic technician.

The exhibit is produced by AMNH and/or water.org, and located in the Museum at Prairiefire (museumofpf.org). It may be interesting to listeners in the Kansas City area.

Heather writes:

Hi Dr.s R & D!

I think I recall one of you mentioning a younger relative enjoying the game Plague, Inc. during a podcast somewhat recently. With this vague notion in mind I downloaded the game and have been enjoying it ever since. Normally I don't like electronic games, but this one seems to use some very accurate algorithms to simulate the spread of various real and imaginary pathogens, with the ultimate goal of the player being the total annihilation, or enslavement, of humanity. The game is played from the perspective of the pathogen and DNA is the "currency" of the game, which I thought was very clever. Most of the "science" the game is based on seems to be quite well-researched also. I think a discussion of the game, from the viewpoint of scientists who work with microbes and pathogens, would make for a very interesting TWiM or TWiV (there are many kinds of pathogens, besides parasites, including viruses. I have good luck winning with both, even on the "brutal" level of difficulty).

I have just subscribed to Urban Agriculture. I have no idea how I will keep up with four podcasts now! I have no idea how Dr. R. keeps up with four of them! I can keep on top of TWiP and TWiM easily enough, since that is my background but I sometimes have trouble with TWiV, since I only have the most elementary virology background. Perhaps a virology primer, like the early episodes of TWiP, would help me and other listeners who don't know a ton of virology?

Thanks for the great podcasts!

Regards,
Heather

Tristen writes:

Dear Vincent and Dixon,

I have to tell you that I'm a huge fan of Twip and I love listening to you guys! In November 2013 I did my first medical mission trip to Nzara, South Sudan. Vincent you probably already know an interesting fact about Nzara is that it's one of the first places Ebola virus was discovered in 1976! After the short trip I enjoyed the work so much that now I am trying to find funding or sponsorship to leave life here and work in Nzara for a couple years. I appreciate how your podcasts are both educational and entertaining at the same time. My favorite one so far is when you had Peter Hotez on talking about neglected tropical diseases.

I want to request you guys do an episode about chronic malaria infection in children living in sub Saharan Africa and the connection between Epstein Barr virus and the high rate of pediatric burkitts lymphoma diagnosis. This would be a great podcast because it combines parasitology and virology! I learned about this connection after having malaria myself after my trip and find it very interesting. Thank you both for your good work and for giving me such valuable information which I can take back with me to South Sudan!

Truly,
Tristen

If you are interested in seeing the page about my work, visit here:
www.facebook.com/berawenzara

Claire writes:

Hi Dickson and Vincent,

I wrote to Twiv recently but had to also write in here to let you know that without your podcast I would have been totally lost last month when I heard a series of talks on some of the more "popular" parasites (tryps, leishmania etc). I didn't know an amastigote from a billy goat before studying up with your podcasts. Thanks for the help!
-Claire in Seattle

Jim writes:

Here's a link to a short story in our local "Daily Press" for the Norfolk area, about a museum in Tokyo about parasites. Perhaps it's provide Prof Despommier a side trip one day when he's in that part of the world. - Jim; Smithfield, VA

Museum might put you off sushi for a while

For something educational to do before lunch, I admired bottle after bottle of pickled parasites. Some frilled. Some with suckers. Most hermaphrodite. And all gross...

Suzanne writes:

I found lice in my 7 year old's hair about a month ago. My 11 year old had been asking me to check her hair for months and I never could find anything. Checking more closely with a lice comb revealed she did have them. A quick comb through my hair came up positive, too. Yay. Lucky for my husband, he keeps his head shaved.

There was a funny thing I noticed, though. I had been taking a low dose of iron daily and can pretty easily tell when I'm... eliminating... the extra and ought to skip a day or so or when it's all being used up. As soon as we shampooed and combed out the lice, I stopped using all the iron.

Remembering your comments on hook worm and anemia, I looked up lice and anemia. Google had links to a few cases where kids who were very infested showed up at doctors' offices or hospitals with severe anemia that had no other cause the doctors could find. This and the information about lice that mentioned some people have asymptomatic cases (evidently the itching is due to an allergy, not their bites) made me wonder just how long we had all been infested. I've had off and on times of slight iron deficiency since I was pregnant with my youngest and my oldest was in preschool. That's not too uncommon in women and I'm healthy otherwise. This could be totally coincidental, I know, but it's making me wonder.

I'd love to know if anyone has studied how prevalent lice are in the US. I'm starting to suspect that quite a few of us could carry them around in low numbers and not know for... maybe years? It does seem, like bed bugs, that lice are turning up more. At least around here in Central Texas where the weather is barely even worth mentioning. It's summer so it's hot. Seriously hot. But we've been getting more rain this year so that's something.

Peter writes:

Dear TWiP team,
I thought this report from The Lancet Infectious Diseases may be worth a mention:
http://www.thelancet.com/journals/laninf/article/PIIS1473-3099%2814%2970794-7/fulltext

Evidence of schistosomiasis has previously been found in 5200-year-old Egyptian mummies, that date has been pushed back a thousand years by the find of a flatworm egg in a grave at a Neolithic settlement site in northern Syria.

Piers Mitchell at the University of Cambridge and his colleagues examined sediment collected from beneath the pelvises of 26 skeletons, all between 6500 and 6000 years old. In one 6200-year-old sample they found a 130-micrometre-long flatworm egg that belonged to one of the species responsible for schistosomiasis.

More information on the Tell Zeidan site:
https://oi.uchicago.edu/support/tell-zeidan-syria

Regards

Rabbit writes:

I just started listening a couple weeks ago, so I'm not caught up yet, but TWiP is the best science podcast I've found. It's so hard to find resources for laymen about parasite that aren't full of misinformation. I've been teaching myself about parasites for a while (I'm autistic, and they're one of my special interests). As is the case with many subjects, it's hard to find resources about parasites that appeal to an audience that's not made up of either experts or complete novices. It's easy to find very basic information, and it's not too difficult to find academic resources, but TWiP is by far the best resource I've found for my level of knowledge.

I have a question: I've read that cat owners aren't significantly more likely to be infected with toxoplasma gondii than people who don't have cats. Is that true, and if so, why/how do you suppose that is?

TWiP 72 letters

Robin writes:

plethora (n.)

1540s, a medical word for "excess of body fluid," from Late Latin plethora, from Greek plethore "fullness," from plethein "be full" (see pleio-). Figurative meaning "too-muchness, overfullness in any respect" is first recorded 1700. Related: Plethoric.

http://www.etymonline.com/index.php?term=plethora&allowed_in_frame=0

Are birds infected?

"No" "Only warm blooded animals".

"Warm-blooded animals" includes birds.

David writes:

Dear guys,

Question, who is Spencer Wells, arose in final minutes of TWIP show I just heard, near mention of tragocytosis (sp?) and a couple of enjoyed PBS series.

Spencer Wells also had a PBS (I think) bit of his production. Must be something <ten years ago now, but charmed me so that it seems fresher than that. I've always wished to see him back with more. Wish I knew the title.

He is a geneticist, and I guess was on the cutting edge of reconstructing the origins of human dispersal. He clarified the first spread of sapiens along the South Asian corridor, ultimately to Australia. Your context was "tropical species which went where it didn't need clothes."
His bearing seemed a little (American) aristocratic, but not in an offensive way. I thought his discussion was especially smart, and I felt exceptionally well informed by the show. Is it conceivable that it was a bit too far above intellectual middlebrow to satisfy the viewing demographic? I don't know, and shouldn't even speculate, and must add that I too have enjoyed the other PBS productions you guys named. Besides, human origins has always been a favorite hobbyhorse of mine.

Anyway, the genetics-based reconstruction of human population origins has moved by leaps and bounds since, as you know, yet I haven't encountered any but snippets of detail in public productions. I wish Spencer would come back with a new show on the subject.

That's who I think he is.

Fondly,
Dave

PS So what is tragocytosis?

Rachel writes:

Dear TWiP Team:

In listening to TWiP episode 71 whilst gently tending my cell culture garden, I noted an inaccuracy in your classification/description of birds. In the context of the host range of Strongyloides, Vincent asks, "Are birds infected?" To which Dickson replies, "No... warm blooded animals," implying that birds are not warm blooded animals. This is a mistake that I have noted being made in previous episodes of the TWiX family of podcasts as well. Most birds are, indeed, warm blooded animals, more precisely homeothermic endotherms, as are most mammals.

A one-time point in need of clarification the same part of the conversation, which seemed to be about Strongyloides in general, not S. stercoralis specifically, is that, while it is true that S. stercoralis only seems to infect mammals, there is at least one species which does infect birds, S. avium.

Thanks for the interesting podcasts.

Sincerely,
Rachel Tell

==
Rachel Tell, DVM, PhD
Postdoctoral Research Fellow
University of Iowa

Colin writes:

hi, is there a parasite known to kill all virus it encounters.
is there a virus known to kill all parasites?

Has any virus been found to have parasites yet? and if so do they have virus? and so on and on?

I know these questions may seem a little perhaps different, but what do you guys think?

Kind Regards,
Colin

James writes:

I’m not a veterinarian or a fish farmer. But I trained as a marine scientist, including a large part of my studies at the Institute of Aquaculture, and worked on the production of a vaccine. A bit of feedback concerning show TWiP 70 (which was great as always!).

Apologies if anything has been discussed across TWiX, feel free to center on interesting bits (if any).

Zoonotic or non-zoonotic invasive bodies

Just as significant, if not greater risk of invasive aquatic species likely to be through ballast water in shipping. This has already had significant impact across the atlantic. Carcinus maenas (Green crab / european crab) has been well studied and decimated your soft shelled crabs in parts of America. They hitchhiked as larvae in the ballast, which when expelled at shore to raise the height of the ship to enter so do the larvae. Conversely America then sent signal Crayfish over by the same means to pay Europe back!

This is why in Australia in addition to strict animal import rules (i.e. never, almost), ships are order to remove ballast much further out at sea in order to protect the barrier reef. As well as severe consequences for shipping firms, ship captains flaunting this will have severe consequences (non-nationals face banning from the country and it’s territorial waters- a career ender).

‘Aquaculture’ vs Rearing

Unlike True Eels, the Monopterus albus does not require migration to, for example in European species, the Sargasso Sea in order to complete it’s life cycle. However, I suspect (although I cannot find any exact confirmation) that M. albus has still yet to have it’s full life cycle closed in aquaculture. Hence the phrase ‘farm raised’ or ‘reared’ being used. In my quick search the only specific confirmation to captive either way to breeding of M albus was a negative one (http://www.seriouslyfish.com/species/monopterus-albus/), with a few US government agencies refering to ‘escapes from aquaculture farms’. But these could refer to those that escaped from a farm of another species, e.g. fish. Sorry I can’t be more specific most of my documentation is in storage in Scotland.

In Anguilla it actually still requires the capture of live elevers (young), and ongrowing in capture. They cannot be ‘bred’. Despite this is similar to the maturation of Salmon, which can have it’s life cycle closed, the closing of the Anguilla sp life cycle has still eluded scientists. I did find one reference to use of hormone treatments for M. albus, but I am sceptical barring further documentation.
fresh/salt

DD, brisked over there being fresh and salt water eels. Anguilla anguilla (European eels), that are part of the true eels (Anguilla) and are normally fresh living but migrate to sea for spawning. European eels migrate all the way to the Sargasso sea! (satelite tracking of eels: http://www.sciencemag.org/content/325/5948/1660.abstract). Larvae return via the gulf stream.

The same is true for the American eel (Anguilla rostrata http://www.fishbase.org/summary/Anguilla-rostrata.html) which also travels to sea for spawning, although the journey is less dramtic as it’s european cousin.

The whole of the Anguilla is often described as freshwater due to the greatest part of its life being freshwater.
Eels have strict protection in the UK. It means criminals try to harvest elevens at night. Leading to police waiting in the dark for them!

Polyculture

You mentioned polyculture. It has been known, on developing areas for pigs to be cultured in wooden sheds. On the lower level, chickens are cultured. Both floor have gaps between floorboards for the excrement to fall through to the lower level. Below the fish? It is built over rivers, so below the chickens are small fish cages!

This also kind of side arches into DD's new podcast (first episode was great) but i will save that for a separate email.

Didn’t catch many eels (100)- I can beat that!

There was a now infamous article of contamination in fish feed and effects on human health due to PCB’s. It rose to stardom due to the BBC being reprimanded for its use as part of a ‘documentary’ that was highly biased. It involved a sample of less than ten fish (five I think). It was a farmed versus wild comparison assuming feed would result in the changes on the chemical. Of the fish sampled some were from America, some UK. The ONE ‘farmed fish’ that was ordered, it turned out wasn’t even farmed (never specified when ordered). It got published and was being reviewed as part of EU policy. The blunder only got found out through coincidence of a scientist being on the EU review board also being at the Institute supplying the fish, knowing they only used wild samples of that species (and later confirmed this).

great to hear all your collective podcasts
James
(too warm at about 18oC)

Rachel writes:

Hello TWIP team-

I would like you to know that there are veterinarians listening to This Week in Parasitism. I am a veterinarian, immunologist, and steady TWIx listener. I have recommended all three TWIx podcasts to many colleagues, veterinary and otherwise, over the last year since I came across them for the first time. I find TWIP, in particular, is interesting to the me due, in no small part, to my veterinary training. We spent a lot of time on eukaryotic parasites, especially those with zoonotic potential.

Additional Episode 70 notes: I would really like it if you would spend more time explicitly on the non-human side of zoonoses, as you brush up against it during many episodes but rarely spend much time on it. Also, add me, along with letter-writer Heather, to the list of people who would love an episode here and there devoted to aquatic or aquaculture themes (my background is largely in the immunology & diseases of fish).

Keep up the good work, I like having TWIx in my rotation of cell-culture listening.

Sincerely,
Rachel Tell

--
Rachel Tell, DVM, PhD
Postdoctoral Research Fellow
University of Iowa

TWiP 71 letters

Heather writes:

Hi Dr.s R&D,

I thought you might be interested in this news article about aquaculture in Hong Kong. Perhaps it's time for another fish parasite episode? I love the podcast, keep up the great work.

Heather

Bill writes:

Trichinella (1835-2007)

After a long and productive life, I am sad to tell you, poor Ella is gone, it seems she was always around, that she had such an infectious nature that she would never fade into history in this manner...

http://www.trichinella.org/ needs an update datewise...

Your web guy can set an autoupdater for dates and copyright notices etc, so as each year passes, the year is incremented upwards. Each date you update needs to be told to the web guy, so it is included in the update and does not change the font or color.

It makes the website look fresh.

Ellen writes:

https://www.etsy.com/listing/111428571/cross-stitch-pattern-set-malaria-life?ref=related-2

Thought you'd enjoy this :-)

Alicia Watkins' Etsy shop has many cross stitched bacteria and viruses too!

Fishpathologist writes:

Dear Doctors R&D,

I'm catching up on old episodes and I very much enjoyed Dr. D's reading from his new book. I see that his vertical farm book is in audio format, will the new book also be available in audio format? Dr. D telling "stories" is one of my favorite parts of TWiP and I would love a whole book of them.

I also wanted to tell you how far-reaching your podcasts are. My husband works coordinating volunteers for a state park. A science club from a community college in Tennessee came to volunteer in the park during their spring break. My husband was very taken with how industrious and intelligent the group was. I work managing chemistry and microbiology labs for undergraduates at a state college, so I was naturally slightly suspicious of these assertions. The students and their advisor invited us to have dinner with them and I must admit I found them very engaging young people. Due to my interests and previous work with parasites and microbiology the conversation naturally turned in that direction. One of the young ladies, who couldn't have been more than 18 years old, mentioned that she absolutely LOVED all the TWiP, TWiV, and TWiM podcasts and is pursuing microbiology as a field with an interest in cyanobacteria. I thought you would enjoy hearing how your work inspires some of the youngest of the new generation of scientists. Thank you for the excellent podcast. I look forward to more "stories" and I really like having guests like Sagi on TWiP.

Ellen writes:

Hi Vincent and Dickson,

I enjoy the TWIP podcast as someone who's interested in science so please excuse me if bubonic plague isn't a parasite. But if it is... did you see the 3/29 article in The Guardian where archaeologists and forensic scientists say "only an airborne infection could have spread so fast and killed so quickly"?

http://www.theguardian.com/science/2014/mar/29/black-death-not-spread-rat-fleas-london-plague

What do you think? Does this make more sense than transmission by rat fleas?

Jody writes:

Hi,

Just a couple of corrections for when the discussion veered off into climatology.

La Niña is only the opposite case of El Niño and has nothing to do with the Atlantic. There are how ever oscillations in the ocean and atmosphere in the Atlantic as well, such as the North Atlantic Oscillation (NAO). It has been partly implicated in this cold winter in the US and the warm wet winter in Europe.

El Niño/La Niña also have nothing to do with undersea volcanos. At the most basic they are caused by changes in the trade winds affecting the depth and warmth of the upper layers of the Pacific. When the trade winds flow in one direction they expose cold currents (rich in nutrients) off the coast of South America and build up warmer water above Australia. The other way the warm water covers up the cold South American currents, cutting off the important marine food sources, and reducing the sea temps above Australia.

As a New Zealander I am very familiar with the Southern Oscillation Index which is one of the main measures of El Niño intensity. As a resident of Finland I am now learning of the effects of the NAO. Wikipedia as always has quite good descriptions of both and as well as other regional phenomenon.

And as a side note, I would say that human caused climate change is about as controversial among climate scientists as HIV causing AIDS is amongst virologists.

Thanks for the great podcasts. Even as a software developer I enjoy the whole TWiX series, although it is only TWiP that makes my skin crawl :-).

Regards,
Jody

PS. Has Vincent thought of giving all the regular TWiX hosts the interview treatment like his recent podcast? I'm sure many are also interested in everyone else's backgrounds.

Scott writes:

Gentlemen,

As always I listened with considerable interest to your discussion of malaria, having had it many times. But when you got to the discussion of El Niño, that's where things went wrong.

El Niño is not the result of oceanic volcanism as you were speculating in the TWIP podcast of late March.

The El Niño and La Niña pattern is the result of the interaction of persistent trade wind patterns and surface water temperatures in the Pacific Ocean.

In normal years, the trade winds, which blow persistently from east to west, push surface waters in the Pacific towards the west. Current (last three hours) trade wind activity in the Pacific can be seen dramatically in this graphic:

http://earth.nullschool.net/#current/wind/isobaric/1000hPa/orthographic=-146.83,-0.62,441

So ocean water that is pushed to the west by the trade winds, has to be replaced, and it is replaced by water rising from the depths along the west coast of South America. That water is extremely cold - and hence, the penguin populations in the Galapagos, which are located on the equator - the last place you'd expect to see penguins, and hence the chilly climate of Lima, on the tropical Peruvian coast. The penguins feed on herring and sardines, both cold water species, which flourish along the west coast of South America, in the upwelling cold water. The cold water generates little evaporation, hence the coastal deserts.

As the surface waters are pushed to the west, they accumulate around Indonesia/Malaysia, where they are pushed down into the depths. That deep, warm water is why that region is one of the most active thunderstorm regions in the world and the world's most active typhoon region - and, with global warming, becoming increasingly active.

On occasion, and for various reasons, the trade winds die down over a period of time, and the accumulated warm water in the western Pacific comes sloshing back to the east. Once it arrives in the eastern Pacific, the surface waters warm substantially, the sardine and herring fisheries die off, and the Peruvian fishermen starve. This usually happens around Christmastime, and hence, the Peruvians gave this phenomenon the name, "El Niño" referring to the Christ Child - in reference to Christmas. When this occurs, the warm water leads to increased precipitation, hence the flash floods in the Peruvian and Ecuadorian coastal deserts in El Niño years.

When the trade winds increase above normal, the pushback to the west is increased, and the opposite hydrologic effects occur. The cold water upwelling along the South American west coast is enhanced, and the herring/sardine fishery flourishes. This is a "La Niña."

Here in Costa Rica, our climate is dominated by the El Niño/La Niña cycle, so we watch it very closely (our worst drought on record by far was in the Great El Niño of 1984). So here is the current forecast for the "El Niño 3.4 index" for the next year, based on current climate models. A +0.5 or greater indicates an El Niño, and a -0.5 or greater indicates a La Niña. Close to the centerline has been dubbed "La Nada" The Nothing. The red line is the most watched model, the cyan line is the model consensus:

http://www.cpc.ncep.noaa.gov/products/predictions/90day/tools/briefing/sstaa.gif

I hope this clears things up for you.

Regards from sunny and abnormally dry Costa Rica (77º as I write this),
Scott
Cartago, Costa Rica

Stacey writes:

Hi Vince and Dickson,

I came across this article on the IFLS website on facebook and thought it was really interesting. I do confess that I dont listen to TWIP as often as I listen to TWIV, but would love to hear your thoughts about this study (I promise to listen to the episode!). I can’t seem to download the article yet, apologies for only sending the link: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13242.html

The weather here in sunny Pirbright is 16C and partly cloudy, quite a nice day in England lets be honest!

All the best,

Stacey
Arbovirus Pathogenesis

Robin writes:

Homo sapiens is mostly an invasive species.

The species is adapted to life in tropical climates: any place that it needs clothes, it is an invasive species. Its natural migratory spread from Africa was through the (now) Middle East and South Asia to the Indonesian archipelago and thence to Australia. It did not need clothes for this.

Spencer Wells:
The Journey of Man PBS (playlist)
http://m.youtube.com/playlist?list=PL895E779F2D722DAF

Everywhere else, it is an invasive species, needing clothing (and shelter) to survive. This includes the migration to the New World which passed through Beringia.

Gnathostomata are the "jaw-mouthed" vertebrates, as distinguished from the Agnatha, the jawless vertebrates (fish). The jaw is derived from the second branchial arch anlage. The clade includes the Sarcopterygia, the "flesh-finned" fish (with muscles in their fins) which in turn cladistically extends to the Tetrapoda: so, Gnathostomata 'R Us!

Thanks as usual for these most entertaining hours+. A whole lot more interesting because the subjects are intellectually stimulating. Dr. Dickson's resolve to stay at the tiller till the stars guide him elsewhere is much appreciated.

 

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