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TWiP 41 Letters

Adam writes:

What up Doc's?

I'm writing to voice my complete disagreement with the sentiments of Sven Urban, in his letter on TWIP 38, that you as hosts are prone to engage in a ‘degree of banter which is distracting'.

I'm sure Dickson does not mind being antagonised, and like caffeine on an adenosine receptor the antagonist in this case is a vital educational aide serving to keep me awake.

I will concede the point that Dr. Racaniello is most often the instigator of these disruptions. For negative control please see the first episode of TWiV which Alan and Rich did on their own - this ran disappointingly efficiently, depriving me of company and edu-tainment on the latter half of a long commute to uni.

I will end with this observation - If you can't play as a child you can't be imaginative, and the last thing we need is scientists without imagination (I believe these are called accountants btw).

You have this listener's permission to be as disruptive as you like.

Keep up the good work.


Melbourne, Australia (26◦C Partly Cloudy)

PS: Consider this my vote against This Week in Old Guys Reading Aloud from Textbooks (TWiOGRAFT).

Liesbeth writes:

Hi Vince, hi Dick,

my name is Liesbeth and I'm doing my Masters in Epidemiology of Infectious Diseases at the Oswaldo Cruz Institute in Rio de Janeiro. I started to follow TWIV a couple weeks ago and now I'm absolutely infected with TWIP and trying to catch up with TWIM also. Thank you so much for this great initiative, for the effort and time dedicated... it's really appreciated and highly contagious! Keep up with the amazing podcasts!

All the best,

Bill writes:

Dear TWIP Team

30-40 years ago, completely unaware of giardia, when hiking in the high Sierra we commonly drank from mountain streams without any ill effect. There's much greater awareness since then, but I wonder if the risk of infection has really increased. i.e. if drinking from fast flowing streams at high elevations is as safe now as then. What do you think?

Arthur writes:

Vincent Racaniello and Dick Despommier- you guys are GREAT!

I discovered TWiP one month ago and so far I'm addicted, I don't know how many guys in Kenya listen to TWiP, I suspect I'm the only one but I'm quickly spreading the gospel. I have special interest in the Leishmania podcast because I came across so many patients with Kala Azar especially during my internship year in Eldoret- Kenya, last year and I have seen firsthand the kind of clinical havoc the parasite can cause. A few questions;

Q.1 Why do patients with Kala Azar have pancytopaenia (most of the time-severe)?

Q.2 Apart from the BMA and the Splenic Aspirate, what are the rapid diagnostic methods that are available and how accurate are they?

The doctors working for MSF- (doctors without borders) in Pokot (an area near the border of Kenya and Uganda where Visceral Leishmaniasis is endemic) usually base there diagnosis on epidemiology and some rapid testing methods and start treatment- mainly sodium stybogluconate but some patients still die, so over to my next

Q.3 How effective is Sodium Stybogluconate in the treatment of Kala Azar? Is Amphotericin B more effective despite its side effects?

Observations: In Kenya the most vulnerable age group are kids around the age of 6 years because they play on and around anthills where most sandflies are found.

Prof. Despommier and Prof. Racaniello, it would be really great if you give lectures in Kenya- the medical fraternity here will really appreciate it.

Dr. Arthur Mumelo - Medical Officer - rural Kenya.

Roxanne writes:

I am a new to the podcast. I gotta say I love the repartee. I find it entertaining and it sometimes adds suspense when the answers are put off for a bit. As a disclaimer: I am an avid CarTalk fan. Your names, Vincent and Dickson, even share an alliteration component like Click and Clack.

Roxanne, PhD (microbiologist turned forensic DNA analyst, public health hopeful)

Daniel writes:

In the early TWiP episodes Dr. Despommier spoke at length about neurocysticercosis. You mentioned that the neurocysticercoses remain dormant and the patient is asymptomatic (unless they obstruct the foramen magnum) until they begin to die and subsequently cease to suppress immune response. My question is, if cestodes that become neurocysticercoses have no aging genes what causes them to die? Is it because they are encysted and can't gather nutrients from their environment?


Ethan writes:

I had some questions regarding the difficulties in producing successful vaccinations for sleeping sickness. From my understanding, the biggest trouble is that as the immune system produces effective antibodies and the trypanosome populations decline in the host, gene expression for molecules making up the outer VSG coats in progeny switch to quiet genes thus changing the VSG molecules and rendering the host's current antibodies useless.

Why can't we vaccinate against all of these antigen variations? If that is impractical, why can't we vaccinate against every 10th antigen, for instance, so that once the trypanosomes turn on one of those genes it is then eliminated by the host's inoculated immune system? I'm also curious as to whether the trypanosomes always begin their life in their host with the same VSG or if it will vary its first expressed gene. If it always starts in the same place and uses a specific order, we could better select which ones to make vaccines for.

Since the trypanosomes switch these genes in a specific order, can we catalog this progression in a model and use that as a reference for the host's current and future antigens? If so, we could select the most relevant vaccine that would be effective against the impending wave of new antigens, playing the waiting game for our target gene to be switched on.

Sorry for the barrage of questions, this just had me thinking the last few days. It seems to me a vaccine for this should be easy - but obviously I'm wrong!

Christopher writes:

Hello gentlemen,

First off I want to thank you both for an excellent and entertaining podcast. I am a regular listener and I enjoy your show immensely!

I had a question regarding the "successful systems attract parasites" quote. Dr Despommier mentioned that this quote had won a poll in which readers were asked to vote for the pithiest statement on biological research over a specific time frame (or perhaps that best summarized 100 years of biological research??). As part of an upcoming faculty lecture series, I am preparing a talk on how- at least from an ecological perspective- that statement is perhaps better worded this way: "parasites play key roles in defining and structuring successful systems". Unfortunately I have been unable to find any reference to this poll online, and I was hoping Dr Despommier would be so kind as to remind me of the details (what publication / organization ran the poll, what were the "rules" of the contest).

Thanks for your time, and I look forward to more awesome podcasts in the future!

Cheers, Chris
Christopher Blanar, Ph.D.
Assistant Professor of Biology
Division of Math, Science, and Technology
Farquhar College of Arts and Sciences
Nova Southeastern University

Stephen writes:

Re: using sari cloth to filter water to reduce cholera, the agent being filtered is a copepod that carries Vibrio, not the Vibrio itself:

"In laboratory experiments employing electron microscopy, we found that inexpensive sari cloth, folded four to eight times, provides a filter of [about] 20 [microns] mesh size, small enough to remove all zooplankton, most phytoplankton, and all V. cholerae attached to plankton and particulates [greater than] 20 [microns]."

Links to download a pdf of the PNAS paper:

Reduction of cholera in Bangladeshi villages by simple filtration


PS, I wrote to TWIV previously regarding hyperparasitoids. I really like the extended format and the fact that your shows feature people who know what they're talking about, or admit that they don't know.

Chris writes:

Hi Vincent and Dickson,

Love all your podcasts. I just wanted to write in to clarify a couple of things that were said on a couple of recent TWiP episodes.

On TWiP 37, you were discussing the use of water filtration in the eradication efforts of dracunculiasis and the subject of the work of Rita Colwell came up in which she used sari filtration to filter out Vibrio cholerae from natural water sources. Dickson mentioned that this might be possible due to V. cholerae's long flagellum. In fact, the reason this is possible is because of V. cholerae's affinity for chitin. The majority of the bacteria in nature tend to be attached to small crustacean zooplankton. It is this property that allows enough of the bacteria to be filtered out of the water to significantly reduce the incidence of cholera in areas using this practice. Thus, because of this, I think it would be unlikely that this type of filtration would have a significant effect on removing other enteric bacteria (infectious dose playing a role here too).

On TWiP 38, you were discussing Babesia, and Dickson said that the species was bigemina. However, B. bigemina is vectored by Boophilus ticks and is the cause of a cattle disease known as 'Texas cattle fever' or 'red-water fever'. In the United States, Babesia microtiis the species that most commonly infects humans and is vectored by Ixodes scapularis ("deer tick") in the U.S. Northeast and New England regions. Thus, it is B. microti that is the most important species infecting humans and has a deer tick - rodent life cycle. Since it infects red blood cells, it has also been an issue for the blood supply.

Just wanted to clarify those two statements not as criticism, but more to get the correct information out there. Keep up the great work with the podcasts.

Chris Whitehouse, Ph.D.
Microbiologist working for the U.S. Government in the Washington, D.C. Area

Allan writes:

I've enjoyed listening to your your TWIP podcast. You are a wonderful story teller and though I have worked in this field a bit as well, I never fail to learn something. I listen in the car on Sticher. My kids think I'm weird but they like it too.

In the episode today (1MAR12) on dracunculosis, you made the natural connection that we come across cyclops both in Malaria and the Guinea Worm programs, but in the podcast you mentioned a couple times that mosquito larvae eat the cyclops and I think you probably meant the converse.

We add cyclops to family water jars in Cambodia to eat the mosquito larvae.

Anyway keep up the great work. You strike a nice balance of making the field more approachable, while keeping it interesting enough even for the grouches.

Best regards,

Allan, DIH, MPH



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