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While it is true that Taenia saginata tends to be benign as helminthic infestations go in humans, the same cannot be said for Taenia solium.
In both cases, ingestion of (encysted) larvae leads to enteric infestation with adult worms. In the case of Taenia saginata the eggs do not produce the encysted forms in human tissues.
Not so in the case of Taenia solium, where the eggs, even on vegetation, can be ingested by vegetarians, producing larval stages encysted in tissues, known as cysticercosis; an infestation in the brain, called neurocysticercosis, is particularly undesirable.
Segments of Taenia solium regurgitated from distal locations into the stomach can have their very numerous eggs all simultaneously activated by gastric juice, resulting in rather severe cysticercosis.
A species is an organism with a distinct group identity that can be maintaintained through multiple reproductive generations, even when hybridising across the entire group. Genetic drift limits species identity over time.
Here's a link to an hour-plus podcast from EconTalk (!) by a journalist about the growing interest in exposure to pathogens to promote better immune responses. Looks like the related book has been out a year, and has only 54 reader reviews. It sounds like the interviewer, Russ Roberts, was reluctant to do the interview, but relinquished after prompts from several folk. I've not heard of the author or the book, but both may show up elsewhere, and the interview may provide enough insight to determine if the book is worth reading. Thought Dickson might be interested in listening and commenting on the concepts.
Hello Drs D and R!
I just listened to TWIP #66 where Vincent expressed his “I’m not mad, just disappointed” feelings towards the lack of emails received lately – so I’ll do my best. I would like to take the story of Schistosoma mansonii resistance to oxamniquine that you presented and appeal to Dickson’s ecologist side. It was found in the presented study that a single amino acid change inactivated the sulfotransferase activity of a Schistosoma mansonii enzyme, interfering with activation of the prodrug and conferring resistance. Assuming Schistosoma mansonii evolved the sulfotranferase enzyme for a reason, this inactivation must have come with some kind of trade-off. In the presence of the oxa drug, this trade-off is clearly beneficial. I am wondering if these resistant parasites are somehow at a disadvantage during the “normal” life cycle in the absence of drug since they are short an enzyme. Is anything known about this? Do you think that by removing the drug from the equation the parasites will eventually revert back to the active enzyme form by “fixing” the single amino acid change, thus restoring the enzyme function? Thanks for another great podcast!
Dear Doctors R&D,
I love your podcast! It is wonderful to listen to commuting to work and while I am working as the support technician for the chemistry and microbiology teaching labs at our small state college. My favorite thing about your show is that the format is similar to the "seminar" or "journal club" courses that were my favorite in graduate school (that was back when I too wanted to be a "dr.", before I became a lapsed microscope jockey. Maybe I will go back to grad school....maybe...some day). Basically these 1-2 credit courses consisted of grad students getting together with a professor to pick apart papers in specific disciplines such as microbiology (we went over the "old" "elegant" research that was the foundation of modern microbiology), microbial genetics (we called that one "cloning club), current topics in molecular biology, current topics in elasmobranch biology, and current topics in shellfish aquaculture. My background is in fish and shellfish pathology, specifically the microbial and parasitic (and molecular aspects thereof) diseases of cultured fish and shellfish. Bearing that in mind, while I realize that you focus your podcasts on human/public health issues related to parasitism, might you consider doing an episode about epizootic parasites (or microbes or viruses) that impact humans economically and/or ecologically? Some examples that come to mind are my good friends QPX (quahog parasite unknown) or Perkinsus marinus in the New England shellfishery, "bumper car" disease in Long Island Sound lobsters, or the recent controversy surrounding the ISAV (infectious salmon anemia virus) outbreak in the Pacific Northwest. Then of course there are always parasites that are just fun for their "gross" factor like "salmon poisoning disease". Regardless if your decision regarding the discussion of parasitism of non-human animals I will continue to look forward to your TwiP, TwiV, and TwiM podcasts.
P.S. I read "Parasite Rex" as a freshman in college and it is still one of my favorite books!
P.P.S. "Monsters Inside Me" sometimes grosses me out, and that is saying a lot for it's accuracy!
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.
Dear Dickson and Vincent.
I saw this paper and thought that it could be discussed on TWiP:
Interview with lead author of the study Rebecca A. Cole, PhD, Parasitologist with the US Geological Survey’s National Wildlife Health Center
Dear Vincent and worm enthusiasts. I have been listening to your podcasts for a few years now. I have personally seen and have pictures to prove that there is new species that is infecting millions. Myself included. I copied the following url and am interested to know what you think about the following? http://ropeworms.com/ This is prolly TMI but to get these things out of me I have been administering MMS enemas and every single time I do these rope worms come out of me. WTF. I love your how you are both very witty and your worm info is awesome.
Hi, my name is Angelica. I have a question regarding Lamblia intestinalis. How long antibodies are produced in blood against lamblia if infection occurred? Can we detect infection by blood test even if it is chronic infection? I will be very grateful for answer by email
Hi, I recently listened to your podcast on Giardia and have a question about treatment and life cycles that I can't seem to find anywhere in research papers I have read on the subject.
I understand the 2 stage life cycle of this parasite and that antibiotics will kill it during the trophozite stage, but what about the cysts? Do they survive the antibiotics and therefore will just develop and reinfect once you've finished the treatment?
Consensus seems to be that it is a pretty difficult infection to get rid of, is this the reason why? It would seem to make sense to me to do a second round of antibiotics to kill all the Protozoa that were in the cyst stage during the first round, but I can't find any mention of this in the literature or anything on the life-span/timing of the life-cycle to know when to administer a second dose to ensure complete eradication?
I found your podcast to be very helpful in understanding this parasite and thought you might have the answer to my questions?
Those who get precise about ice ages say it something like this: "The last three million (I'm guessing) years have been an 'Ice Age'. During this ice age, there have been several discrete glaciations."
The height of the most recent glaciation was ca. twenty thousand years ago. It tapered off for a few thousand years before entering the (recently ) current interglacial.
Keybrd gone back.
El Niño is the Boy Child (Jesus). It is the warm anomaly in the Pacific. La Niña is a girl child, named for contrast, and is a cooling period in the area of the Pacific anomaly.
I don't know squat about the identification or naming of the anomalies in the Atlantic, but I wish I did. If somebody put La Nina in the Atlantic, it's news to me.
PS The Cali drought is the worst on record, beyond past dry periods associated with Niños. It is unknown if it will resolve, repeat, or persist for decades. The decline of glaciers in the Sierra (over past decades) may interact with decreased snow pack. In any case, a dry year means a decreased snow pack, the melting of which has been the primary source of water for ag and people in Central Cali. 0% of water contracts is going to most farmers this year. It is a big big deal.