Case guesses:

Anthony writes:

Congenital toxoplasmosis

T. gondii infection — don’t blame a cat; blame a cook.   The parasite is present in raw meat.

Thank you.


K writes:


Thanks for all your hard work. Twi___ are my weekly podcasting highlights. For this particular case, my first suspicion would be Toxoplasma gondi infection. Toxo can be acquired from raw/rare/undercooked meats. HOWEVER, I also suspect this might be a ruse and the cause in this case could just be one of many congenital causes of hydrocephalus. One that comes to mind is arachnoid cysts. I’m not a parasite expert (I’m just a teacher, biologist, and pharmacist) but could you test for toxo before moving on to other causes?

thanks again,


David writes:

Hello TWiP’ers,

I’m just a retired IT guy with an undergraduate Biochemistry degree (from about 40 years ago) who worked at a government public health organization for 38 years. Discovering after the COVID19 pandemic began has rekindled the biology and public health connections I have missed since leaving the day to day workforce. Thank you for the stimulating and informed discussions across TWiP, TWiV, and Immune.

For the new case that Dr. Griffin describes in TWiP episode 187, a review of results from google searches for parasite induced congenital hydrocephalus show many references to toxoplasmosis and cycsticercosis.

The CDC and PubMed sites provide an overview of cysticercosis, which at first seemed like a possible contender in this case, however the CDC site at: states that “cysticercosis is only acquired from the fecal-oral route (ingestion of eggs), not via the ingestion of cysticerci in undercooked pork”.

Information from the University of Chicago Medicine site,, presents what seems to be a stronger case for toxoplasmosis.

Toxoplasma gondii, is a parasite found throughout the world that has infected roughly 2 billion people. It can pass from a mother infected for the first time to her unborn baby, and causes several birth defects, including hydrocephalus, which causes a dangerous build up of fluid in the brain.

The PDF version of “Parasitic Diseases , Seventh Edition, (Dickson D. Despommier, Daniel O. Griffin, Robert W. Gwadz, Peter J. Hotez, Charles A. Knirsch)” also seems to lend credence to the toxoplasmosis diagnosis. What a fascinating resource!

Given the facts of the case – this is the first baby for the mother, and her recent exposure to undercooked meats – I will submit a guess of toxoplasma gondii as the root cause of the hydrocephalus.

As an aside, was one of the sources I looked at during my searching, and I noted the recommendation on that site to remove the skin from fruits and vegetables. What are your thoughts on this, and in particular, does this mean that we should peel all our cucumbers, tomatoes, peppers, etc., from our home gardens if eating them raw? Thoroughly washing them under running water has been the standard in our household, but perhaps more extreme measures should be taken. What does Dr. Racaniello do with the vegetables he harvests from his garden?

Thank you again for the stimulating, entertaining, and enlightening scientific discussions you provide. The shows are a lighthouse of rational thought in the storm of chaos we are navigating through.

Best regards,


Katie writes:

Good Evening,

My guess is Toxoplasma gondii.  She probably got it from the uncooked meat her husband cooked for her. I just learned that the organism can remain infectious in meat for very long periods of time refrigerated or even frozen but the simple act of cooking will prevent infection. Unfortunately, she could have been tested and the child treated had she gone for prenatal checkups.

I’m a vegetarian but also a crazy cat lady. Do those cancel each other out? I’ve read that latent t gondii infection can lead to behavioral changes in the host so being a crazy cat lady really is a thing.

Speaking of cats and parasites, I once got ringworm from a stray cat and it was extremely hard to get rid of. There is currently a neighbor’s cat that likes to visit me on my porch but I put a glove on before petting him. My own “children” are not allowed outside.

Thanks again for intellectual stimulation and entertainment.

-Katie from Missouri 

PS: 71F, 89% humidity, and a 93.4 five day SARS-CoV-2 case count average with a 44% positivity rate here in Boone County

Alexander writes:

Dear TWIP-trifecta,

here in Vienna, Austria it’s 20°C (68°F) and very windy with a thunderstorm just waiting to hit us in the afternoon. When I first wrote to you a few months ago I thought that I could pick up a habit and participate in this podcast regularly. Alas, the phase-II trial for severe COVID I‘m working on is taking up so much time and effort that I simply forgot. Thankfully, an end to this tedious work is on the horizon and I’m looking forward to having our results torn apart on TWIV a few months from now. However, on to the case.

Of course, most cases of congenital hydrocephalus are not caused by parasitic disease; rather, aqueductal stenosis, intraparenchymal cysts, meningitis, intracranial haemorrhage, arnold-chiary malformation, dandy-walker syndrome and many other genetic syndromes can cause hydrocephalus and should first be considered depending on the clinical scenario and history. However, this is a podcast about parasites, in this case, the kind that make you sick. 

One of the most common parasitic diseases that can lead to foetal morbidity if acquired during pregnancy is of course toxoplasmosis, caused by T. gondii, which is named after an exceptionally cute North African rodent called “Gundi” in which the parasite was first described in 1908. While most people think of toxoplasmosis as a disease spread by cats (if they are not properly autoclaved), consuming the uncooked meat of any animal infected with T. gondii can spread the infection, since the cysts are frequently found in muscle tissue. Common symptoms of congenital toxoplasmosis include hydrocephalus, retinochoroiditis and meningoencephalitis, which often result in sensoneuronal hearing loss, reduced intelligence and epileptic disorders in the affected infant. 

Due to the high prevalence of T. gondii oocytes in soils, some developed countries have screening programmes during prenatal doctors’ visits, which our patient might have neglected in favour of a gestation strategy she might have considered to be more “natural”. Since congenital infection is much more likely if the mother is infected for the first time during pregnancy and she has only recently started snacking on exotic meats, the risk is obvious.

A differential to consider would be meningoencephalitis due to infection with Baylisascaris procyonis, which is an exceedingly rare roundworm found primarily in racoons. It’s known to cause eosinophilic meningoencephalitis, which might also explain hydrocephalus, but I haven’t managed to find any reports on congenital cerebral larva migrans due to B. procyonis.

I believe this is a classic case of congential toxoplasmosis. The kid likely needs some imaging, an eye exam, maybe a surgical intervention with or without the implanation of a permanent shunt and pharmacological therapy with pyrimethamine, sulfadiazine, and leucovorin for one year.

Thank you for your excellent podcasts and the high-quality banter, all the best and stay safe,


Maggie writes:

Dear doctors,

Long time listener, first-time guesser. My guess for the hydrocephalitic baby is that its mother is unknowingly serving as an intermediate host for Toxoplasma gondii.  Likely, she consumed contaminated food or drink (maybe the undercooked meat?) with oocysts from a barn cat’s feces, and the crossed through the placenta to infect the developing fetus within the first couple of trimesters. As far as I know, there would be no transplacental transmission if the mother had eaten tissue cysts in undercooked meat, so must have unwittingly been exposed to infected cat feces. Washing hands (a recent theme that should be continued into the future!) and washing the meat that will be served rare would make this much less likely. 

I’m sorry to hear about this story and wish the family luck in raising their child.

Thank you for all that you do to share firsthand stories of medicine and science with us all. 

Keep Twipping!



PhD Candidate

Dearing Lab

School of Biological Sciences | University of Utah

Josh writes:

Hello TWiP hosts,

It is a balmy 70 F (21 C) in Baltimore, Maryland. I think the neonate with hydrocephalus in TWiP 187 may be suffering from a Toxoplasma gondii infection acquired congenitally – potentially through the contaminated ‘rare meats’ in the home. Ultrasound is likely to reveal evidence of elevated ICP in the child. CT with contrast may show ring-enhancing lesions in the brain of the child and/or mother. Testing peripheral blood of both the child and the mother for Toxoplasma IgG, toxoplasma-specific IgM will likely reveal a positive IgG and IgM in the mother and IgG in the child.

If serologic testing is negative, PCR of the CSF should be performed when there is strong clinical suspicion for Toxoplasma infection.

I’m a medical student at the Johns Hopkins University School of Medicine and love your podcast. I’m currently doing an elective in the clinical microbiology lab led by Dr. Karen Carroll (of Manual of Clinical Microbiology fame!) and your podcasts are constantly providing me with interesting tidbits to share with the rest of the microbiology staff here who love hearing about all of the interesting parasite stories shared by you all each week.

Thanks for all you are doing to promote the awesome science of microbes,


Catherine writes:

Hi All,

Regarding the sad case of the lady from Long Island with a child born with hydrocephalus, my guess is that she became infected with Toxoplasma gondii during her pregnancy, which resulted in hydrocephalus in her fetus. This guess is based on a quick consult with my web browser – I entered ‘parasites and hydrocephalus in neonates’ and toxoplasmosis showed up. The description of common sources of T. gondii included cat feces (which fit with the possibility of feral cats roaming on the brother’s farm) and eating undercooked meat (which fit with the mother’s ingestion of ‘very rare’ meat). Also noted that bloodwork is used to diagnose toxoplasmosis and that Dickson seemed to to know the answer before Daniel described the testing. So will leave it at that. 

I’m new to TWIP but the episode was so interesting it overcame my usual repulsion to anything parasitic. Live and learn. 



Victoria, British Columbia

Akhar writes:

Hello TWIP from a cloudy Stockholm!

Hope this finds you well and healthy! I’ll try to stay short and to the point as time always seems to be in short supply, which makes your podcast empires productivity even more impressive! I do love the work you do and the community it makes me feel I belong to! 

To the point, if other structural or obstructive reasons for congenital hydrocephalus has been excluded I’d consider infectious causes. And if no other neurological deficits are present, the other TORCH infections sound unlikely and the most likely culprit seems be toxoplasmosis. Oocysys from undercooked meat is likely, the advent of that risk factor also coincides with her pregnancy. 

     I find it odd though, in Sweden there a strict and generally well known dietary guidelines for pregnant women. Ex avoid raw/undercooked meat, unpasteurized products, some fish such as lake fish (parasites), baltic fish and high tier/apex predators (accumulation of heavy metals/environmental toxins) and so on. And a routine ultrasound is nearly always performed around gestation week 19. What are the recommendations in the US?

Anywho, amniotic PCR is a bit post festum, serological diagnosis a bit difficult due to transferred IgG from the mother. IgA, IgM could be useful. PCR of blood and CSF gives diagnosis, as well as serology (mainly IgM – barrier damage  -> high protein permits serum IgG leakage). CSF eosinophilia together with markedly elevated protein levels can be seen. 

Hopefully I’ll have time for a Kevin-esque letter sometime in the far post pandemic future. 

With regards and endless admiration!


ID physician 

Tim writes:


The rare meat vector is suggestive of toxoplasma gondii infection as is Dickson’s smirk when this vector is presented.

I wish I could expound as many of your listeners do but I can’t – my backstory doesn’t fit this podcast to say the least.  

I searched the web, downloaded a seventh edition textbook of parasitic disease and this seems to fit the bill.

Toxoplasmosis likely due to the relatively new diet and novel culinary technique – though this can happen to anyone and is common.

I’m interested in these cases, but researching and thinking about the people here… I wish for a gentler diagnosis.  

Please help me with that… I will gladly sacrifice my textbook lottery for a happier outcome for this child and family.


James writes:

I teach Neuropath and Microbiology…

Causes of neonatal hydrocephalus:

Hemorrhage into ventricles, subarachnoid (trauma, hypoxia?)

Genetic conditions

Spina bifida (neural tube defects)

and, drumroll, infections.

Toxoplasmosis, syphilis seem like leading contenders.

Toxo is almost “the perfect parasite”, it can infect many animals. We normally think of “cat poo” as the infectious source, but lots of animal meat from seafood to birds to mammals can have Toxo cysts in the muscle. So I think it’s Toxo. (We usually think of the disastrous “brain eating” that happens in the first trimester along with the TORCH group: Toxo, “other/syphilis”, Rubella, CMV, Herpes.)

By the way there’s an entertaining SciFi book called Parasite by Mira Grant in which scientists comingle Diphyllobothrium, Toxoplasma, and a bunch of therapeutic genes to give people to cure them from various ailments–what could possibly go wrong? And of course…it does.

Thanks for all you do. Taking any TWIPS in the near future?

James M. Small, MD, PhD, FCAPAssociate Professor of Pathology and MicrobiologyClinical Career AdviserRocky Vista University

Barry writes:

Greetings from Baltimore where it’s another hot day on this, what feels like the 97th of March…

I’ve been subscribing to TWIP podcasts for a few months now and have thoroughly enjoyed working my way through the back catalog. Who knew an experimental psychologist working for the US military would find parasitism so fascinating! I look forward to each new episode, and though I have effectively no formal education in biology or medicine I always try to reason my way through Dr. Griffin’s case studies.

I’m going to throw my hat into the proverbial parasitic ring this week with a guess as to the case of the woman with the hydrocephalic infant: I believe her child’s misfortune is a case of congenital toxoplasmosis, the result of in-utero infection by Toxoplasma gondii, an amoebic parasite whose definitive host is the cat.  Dr. Despommier often refers to T. gondii as the world’s most successful mammalian parasite due to its ability to infect any cell, and it’s this ability to infect macrophages in particular, and the unfortunate timing of the initial infection of the woman likely during the first trimester of pregnancy, that led to the child’s pathology. According to PD 7, T. gondii is transmitted via ingestion of one of two phases of the parasite’s life cycle: (1) Oocysts from cat feces — from drinking contaminated water or from eating food handled by someone who was exposed externally (as in the oft warned against practice of cleaning the cat box) and didn’t practice good hygiene practices prior to food preparation; or (2) more often in omnivores and predators, pseudycysts lurking in raw or undercooked meat. Pseudocytst are found throughout the tissues of infected organisms and represent a more or less stable chronic state of infection, held in check by a number of immune responses too complicated for my social scientist brain to understand in any detail.

Dr. Griffin mentioned two potential sources of the microbe during his presentation, though his tone and repeated mention of one lends me to believe it to be more probable. The less likely possibility comes from the woman mentioning that her brother’s family has a farm, and as has been noted a number of times in TWIP, farms often have a resident barn cat or two. It could be that her direct exposure to cat feces was from working in the barn or eating food prepared by someone else working there, with the infection likely through whatever activity one does when working in a barn. (Did I mention being a city boy as well? Enough said.) The more likely cause, though, was the hint that the woman’s husband enjoyed gourmet cooking, including preparing various meats. I suspect undercooked meat, fresh from the butcher and never frozen (which could have killed the parasite), and prepared rare or even in the French manner of bleu (pronounced ‘ble’; see footnote) as the source of the pseudocysts. It was the especially poor timing of the woman’s initial infection during pregnancy that led to the parasite hitching a ride within a macrophage and, after crossing the placental barrier, infecting the developing fetal CNS.

If I’m lucky enough to be chosen for the book, please draw another number as I already purchased a hardcopy from Amazon – I personally don’t get much from ctrl-F’ing through a PDF when I don’t know the material well. Besides, the book’s placement on my coffee table next to “Birds of the Chesapeake Bay” garners lots of comments and quizzical looks!

Thanks again for the podcast and especially thanks to Dr. Griffin, Parasites without Borders, and groups like Floating Doctors – I made my donation today – for reminding us all that parasites aren’t just a nuisance on a camping trip or cookout.

(Note) “Bleu is also the French word for the color blue, and for a steak it means very, very rare; leaking onto the plate when cut.  When you feel the need for an almost raw steak, then a steak bleu will fill that need. A steak bleu indicates that the chef will have allowed the steak to take a quick peek at the grill or frying pan, in passing, on its way to your plate. A steak bleu is just sealed on the outside; when cut that steak will leak copiously onto your plate; it will have been cooked, maybe, for one to two minutes on each side.” (

Martha writes:

Dear TWIP,  This is my first time responding to your quiz. I am just a retired OB. The detail that jumped out at me was taking a newborn to an OB. I hope that when the folks called to make an appointment with the OB, that the OB directed them to a neonatologist. 

I’ll guess that the cause of the hydrocephalus was Toxoplasma gondii. The mother had not been infected prior to pregnancy, acquired the infection in pregnancy and this passed the placenta to the fetus. I think the treatment would be a shunt.

I enjoy all your podcasts. They help pass the time while physically distancing in the pandemic.

Best wishes to you all.

Anthony writes:

The case presented here is the usual “textbook” case of toxoplasma that those interested in infectious disease usually learn and sadly these types of cases appear to be somewhat common… I really think there needs to be a public campaign to tell people about eating undercooked lamb during pregnancy – since if you were to ask people on the street what meats should never be eaten undercooked I’d bet that >95% would say just chicken and pork and not be aware of the pregnancy risk undercooked lamb carries!  The diagnosis I believe is done by detecting IGG antibodies to the protist or by detecting protist DNA in the blood via LAMP or RT-PCR.

A few episodes ago Dickson wanted to learn more about the home PCR kit me and a colleague have been using so I shall provide a short article as written by my colleague:

Maybe Vincent could also share this with Elio since he is one of us mushroom people! 

– Anthony

Debra writes:

Dear TWIPers,

I am writing from Pittsburgh, PA where it is a delightfully chilly 55 F in the early morning. I love listening to the podcast while I work the overnight shift as a lab tech. I usually miss sending in my guesses by just a few days but not this time! 

I believe this new mother and her son have toxoplasmosis. A cursory google search tells that toxoplasma gondii is a common parasitic cause of infant hydrocephaly due to congenital toxoplasmosis. If the mother eats rare meats often, it is quite possible that she would become infected with no noticeable symptoms. If she was infected very early in her pregnancy, she might not have been aware of her condition and have still been eating her husband’s rare carnivorous diet. 

I assume the blood tests are to detect antibodies against the parasite, and the CT to detect any cysts.  

This all said, I am writing during my short break at work and I may have fully overlooked the clue to lead me away from this obvious guess. 

Thanks for the hours of entertainment 


Carol writes:

Greetings from Upstate NY! I am now addicted to this podcast–lol. I have also been listening to and enjoying TWIV to get the latest on SARS-COV2. Daniel’s voice is so soothing to listen to. 🙂 I also enjoy the friendly banter between everyone and my husband can hardly believe that I’m listening to a science podcast! Here is my answer to case # 187– First time pregnancy (immunocompromised host) + raw meats (organic or not) + hydrocephalus in newborn = Congenital toxoplasmosis! Why did this happen in the US? It appears that there is no protocol for testing American pregnant women for Toxoplasma antibodies as compared to European pregnant women who are tested for prior exposure to the parasite. Raw meats, especially ground burgers or steak tartare, are known for harboring the organism. Damn that juicy, rare burger at the picnic! I have heard that much more steak tartare is eaten in Europe, so possibly the reason for the testing protocol for pregnancy there. It appears that mom had never had an exposure to Toxoplasma resulting in ZERO antibodies to protect her fetus when she ingested the tissue cysts in the raw meat, resulting in a more severe situation in the fetus. The fetus becomes infected when the organism crosses the placenta and disaster results. I hope I’m right about this one! Thanks for always providing an interesting case!

Until next time-


Kevin writes:

Long time lurker, first time guesser.

I suggest the patient in TWiP 187 and her baby are dealing with Toxoplasma

Gondii, most likely acquired through the undercooked meats.   

Treatment: ask your health practitioner, I’m in IT, and my recommendation would be “have you tried turning it off and on again?”

 In other Parasite news, I ran across this archaeological study of parasite burden which suggests that the rate of infection remained steady until societal changes in hygiene, plumbing, and sanitation were more widespread in European countries.

Thanks for the always informative and delightful podcast.


Minneapolis, MN USA.

Sean writes:

Dear TWIP Team,

I have been enjoying the entire MicrobeTV ecosystem since first discovering the podcast in January.  I have been thrilled and amazed with the rapidity and ever increasing production quality since that time, and to finally put faces to the voices!  Your views and perspectives have been the horse to which I have hitched my cart these last months. 

I am ‘just’ a Physician Assistant and live in Virginia where it is 71*F today and actually feels like 71*F for once (we have finally gotten a reprieve from ‘real feel’ temps that were in the triple digits much of the summer).

I began listening to TWIV partly for professional reasons (more on that another time) and I love it! In response to a previous letter you read on TWIV, the episodes are indeed long, but NOT onerous.  The episodes occupy my workouts and commute all week long.  You keep me informed, encourage me to think critically, and help me speak knowledgeably to others in my official capacity where I direct healthcare policy.

I sincerely enjoy and appreciate Dr. Griffin’s clinical updates on TWIV, and these parasitology case studies are really enjoyable, they help me flex parts of my brain I have not used much since my Tropical Medicine course years ago.  As a Physician Assistant, I sometimes wish I could claim the hours I spend weekly as Category one Continuing Medical Education (it is Cat 2 at least, journal reading and such), but the time is just so enjoyable and the banter makes us feel like part of the group.

As for the case of neonatal hydrocephaly in the affluent, organically minded mother whose husband entertains dinner guests with tartar… I think we have a great setup for Congenital Toxoplasmosis gondii.  Typically, this is a reason that we encourage mothers not to interact with or clean a litter box least during pregnancy.  T. gondii is also transmitted via consumption of undercooked meat and unwashed (natural) produce, of which the mother has a good history of exposure.  The outcome for the child can be variable, and is somewhat related to when the disease was contracted, but can certainly lead to visual problems and learning disabilities, if not more. 

Thank you for sharing this interesting, albeit, sad case.  Can’t wait to hear how things are going once Dr. Griffin gives the answer.

Yours in health,


Kevin writes:

Hello Heroes of TWiP,

Case guess for TWiP 187: I’ve finally caught up on all of TWiP (and Immune)–time for my first case guess, and it sounds like an easy one! Congenital toxoplasmosis explains the hydrocephalous in the baby and fits the history of the mother. If she had not eaten much meat prior to marriage, she was unlikely to have acquired T. gondii until the time of her pregnancy, when she encountered this master parasite in some undercooked meat. Treatment is pyrimethamine, sulfadiazine, and leucovorin for the baby. The prognosis is sadly usually severe, although the birth was not premature and few other signs were mentioned, so I am hoping the baby can still have a good quality of life.

I leave a discussion of the various non-parasitic possibilities or the less likely involvement of Taenia solium to my capable colleagues. 

I have been dreaming of volunteering with Peace Corps for years. I always get excited when Dr. Griffin gives case studies from abroad or involving Peace Corps, and I think “Oooh I might see that!” or “Oooh I might get that!”. 

In addition to parasites, I’m fascinated by organ donation and have researched living donor kidney donation. For the most part, living kidney donation is safe. However, would running around underdeveloped countries with a single lonely bean be a bad idea? I know this isn’t a parasite question (or is it??) and that I can talk to my living donor evaluation team or PC recruiters about it, but I first thought to ask Dr. Griffin. Feel free to leave the question off the podcast if irrelevant.

In honor of my homonymous fellow TWiPster, I offer an ending oddity: the Talmud states that the heart understands, the spleen laughs, the liver brings anger, the stomach brings sleep, and the kidneys advise. Specifically, the right kidney advises good while the left kidney advises evil. Better then to donate your left kidney, I guess.

Shalom va shanah tovah (happy New Year),

Kevin H

Peter writes:

Dear Drs of TWIP

In TWIP 187, Dr Giffin reported the case of a newborn with hydrocephalus. A search in Parasitic diseases (7th Edition) shows that hydrocephalus is associated with both T, solium infection (in some forms of neurocysticercosis) and also in toxoplasmosis. Matushita et al [1] however report that hydrocephalus is more commonly found in adults with cysticercosis, not in neonates. On the other hand, hydrocephalus is also a symptom of congenital toxoplasmosis.

Congenital toxoplasmosis is caused by lesions in the central nervous system which in turn are caused by the apicomplexan Toxoplasma gondii. Infection is most common during the later stages of pregnancy but clinical symptoms are more common in infections early in pregnancy. The adult mother could have been infected from some of the “rare meats” her husband likes serving as the oocysts of this parasite are often ingested in undercooked meat. 

Prompt treatment of the disease (with antibiotics such as methamine and sulfadiazine) and hydrocephalus (through the placement of a shunt to drain fluid) can lead to good outcomes [2] and prevent problems later in the child’s life. The husband should be urged to cook his meat more thoroughly.


P.S. writing from a cloudy Cape Town.

P.P.S. please give the Ebola outbreak in Equateur Province, DRC, a mention on TWIV. There have now been 124 cases (, and 50 deaths, making this the 10th worst outbreak of the disease. Health workers are fighting this disease in very difficult circumstances.

[1] Hamilton Matushita et al ‘Hydrocephalus in neurocysticercosis’, Child’s Nervous System

[2] David McLone, et al. ‘Outcomes of hydrocephalus secondary to congenital toxoplasmosis’, J Neurosurg Pediatr

Andrew writes:

Kia ora from Pongaroa,

Book: I have not won yet but I can see my future copy in some of the videos. Vincent has two stacks of them behind him in some videoed podcasts. Mine is the one second from the bottom in the stack at the rear.


spring has arrived and we have a windy day with a temperature of 18°C. A mild La Niña, just called by NOAA, will mean a warm and wet spring and summer for us.

Covid-19: It is the secondary effects that are most intriguing here. Health officials are racing to make sure MMR vaccinations, that were missed during the lock-downs, are administered. We have had almost no flu-season here and it will be interesting to see if there is an increase in non SARS-CoV-2 infections as normal life returns or not. Should we beat the odds and remain relatively free from viral respiratory diseases, will we be in for a deluge when the borders open again?

The case of the baby with hydrocephalus:

I love the video version of the podcast. Dicksen’s wry mute chuckle at 1:13 in the video is the most telling clue. It coincides with Daniel relaying the woman’s husband’s love for rare meats. A quick look in PD7 and I checked for parasites that can cause hydrocephaly and came up with Taenia solium,  the Pork Tapeworm, and Toxoplasma Gondii. 

T. Solium does not seem to readily pass through the placenta but T. Gondii sure can. To quote PD7 p133 “In 1923, Josef Janku, described the congenital manifestations of the infection, which he accurately characterized as causing hydrocephalus and chorioretinitis.”  So my guess is Toxoplasmosis. 

Ngā mihi,  (na – me he)


Elise writes:

Dear TwIP Trifecta, 

The sky is bright blue and it is 64 degrees F (17.7 C) in Lower Manhattan, though it feels as if the world is on fire. Thank you so much for providing a well of intelligence, compassion and interest in a moment where I feel thirsty for anything that doesn’t make me angry or despairing. 

I do believe I have a diagnosis for the mother and baby in the case described in TwIP 187. I believe the mother has toxoplasmosis and the baby’s hydrocephalus is also the result of the infection. 

Toxoplasma gondii is a common parasite, found all over the world, and it is frequently found in cat feces and in raw meat. Adults who are infected frequently have no symptoms at all and infection is mostly a problem when people have compromised immune systems. Pregnant women and the fetus(es) are much more vulnerable to infection. (I believe I heard somewhere that pregnant women are encouraged to get someone else in the household to change cat litter.) 

Infants born with toxoplasmosis can have many symptoms including retinal damage, seizure disorders, developmental delays, hearing loss, and hydrocephalus. It seems likely that, given that the family lives on Long Island and that the young mother was eating a considerable amount of raw or rare meat and spending time on a farm, that toxoplasma gondii is the culprit.

One thing I noticed in my research is that pregnant women are most likely to infect their babies with toxoplasmosis if this is their first infection. In this case, given that the young woman didn’t tend to eat much meat before indulging in her husband’s culinary habits, it seems that this easily could have been her first infection. Why is the first infection in the mother so much more likely to spread to the fetus than a subsequent one? 

If my diagnosis is correct, what did Dr. Griffin recommend for the baby and for the mother? (How was her mood with regard to her husband and his cooking after this? Did she perhaps decide to blame her farm visits for the infection instead?) 

As always, I’m so grateful and many many best wishes to all of you.

Best best

Elise in Lower Manhattan 

Jody writes:

Greetings, Tamers of Intestinal Terrorists in TWiPlicate,

Hi from sunny Seattle, where civic order has not yet broken down despite our fair city having just yesterday received the prestigious designation of “anarchist jurisdiction” from the Trump administration. The microbreweries and tech offices are all still standing, the streets are full of runners and dog-walkers and stroller-pushers complying with mask requirements, and the free PCR testing sites are all still humming along and providing test results in under 36 hours.  It’s 72F with clear blue skies, and we can leave our homes once again now that the hazardous air caused by our state’s devastating wildfires has finally cleared out. You mentioned on TWiP 187 that you have a full mailbag right now, so I will keep it short! Well, short for me anyway.

In my brief research into the case of the affluent north shore Long Island mom whose infant was diagnosed with hydrocephalus, PD7 served up two eukaryotic parasites that can cause hydrocephalus after oral ingestion of pseudocysts or embryonated eggs in raw or undercooked meat: Toxoplasma gondii and Taenia solium. However only one of these appears to cause congenital hydrocephalus via vertical transmission from mother to child during pregnancy. Toxoplasma gondii is best known around the US as the excuse pregnant women use to avoid cleaning the litter box throughout their pregnancy (guilty), or more recently in pop science articles as the organism that causes an infection that can lead to reckless driving and sexual promiscuity, but it is a parasite that can infect most warmblooded animals, including mammals and birds, around the world. As Dickson has said many times, it is one of the most successful parasites on earth. 

Congenital toxoplasmosis usually occurs when a woman becomes infected for the first time in her life while pregnant, and the most severe damage to the fetus seems to occur early in the pregnancy. Based on Daniel’s report of our patient adopting her new husband’s penchant for raw animal flesh, as well as Dickson’s chuckles immediately after hearing about this new habit (and his subsequent pass on asking questions about the case), I’m guessing that she rejected standard recommendations of no-go foods for pregnant women and indulged in a little taboo tartare

Hoping for a book. 

Stay safe, and thanks for keeping me company (and making me squirm) for the last six years, but most especially during the pandemic. Hi mom!


Jody   //   L O S T    L A B O R A T O R Y   //

Anna writes:

Hello TWIP! 

I have been binging on the episodes while I am alone looking for squirrel parasites in the backroads of southern Utah (where the weather is a dry upper 70s). I thought I would send a quick guess on the case 187: Toxoplasma gondii. I’m sure the pregnant housewife would have ample opportunity to ingest the parasite either through undercooked meat at her hubby’s parties, crunching on unwashed veggies, or encountering a cat latrine on her brother’s farm. 

Free ranging cats and their contamination of farms w T. gondii is an interesting topic! See this paper by Simon et al. last year 

Simon JA, Chancel E, Hubert P, Aubert D, Villena I, Gilot-Fromont E, Poulle ML. Pattern of latrine use by domestic cats on dairy farms and the implications for Toxoplasma gondii transmission. Veterinary parasitology. 2019 Sep 1;273:112-21. 

Can’t wait to hear more, 


Owain writes:

Dear TWIP trio,

My guess this week is congenital acquisition of toxoplasmosis for this child. The mother didn’t eat much undercooked meat and has no pets, so may have avoided being exposed previously, but was probably exposed when she started eating meat that was cooked rare when her husband started serving it. Hydrocephalus is a feature of congenital toxo, so I think it fits.

I’ve started listening to your sister podcast, TWIV, from the beginning as well as the COVID episodes, and am struck by how much the early episodes from 2009 come full circle to the most recent ones. The 2009 pandemic episodes have you discussing pandemic preparedness, masks, antiviral agents, conspiracy theories and all – sometimes it’s hard to remember which pandemic you’re discussing!

I bring this up because in early episodes you discuss arboviruses, which I count as a TWIP subject given they involve ectoparasites (tenuous I know..!). I looked up getting a copy of West Nile Story, Dickson’s book that he mentions early on in TWIV. Have you guys seen how much it’s selling on amazon for (link below)?! A new paperback copy is selling for $985!! If you have any spare crates of it lying around Dickson you could make a tidy sum…

I find myself waiting for each episode of TWIP the week it comes out – keep doing what you do to slake our thirst for parasitic knowledge!


Kevin writes:

Terrible tropisms or first-hit good news

Pregnancy automatically yields two patients. The most compelling part of this case for me was the devastating idea of hydrocephalus as well as the appalling proclivity of a parasite to live in our brains. My horror of hydrocephalus was of course due to preconceptions and lack of experience. The very word, brutally but literally translated as “water head” doesn’t do much to mollify. I had been previously brainwashed by an early embryology text photograph of an extreme congenital hydrocephalus case, ghoulishly transilluminated

Fortunately, a bit of relief was obtained via a Google search thus constructed: “parasitic causes of congenital hydrocephalus” which yielded the first hit stating “Babies with hydrocephalus and toxo have good outcomes [ref in endnotes] . Spoiler alert not averted.

Raw meat and congenital disease rubs our noses in toxoplasma. A related case was discussed in TWiP 162, though not involving a neonate. A differential diagnosis should, out of good habit, not be neglected. Turning aside noninfectious causes such as anatomic malformation, tumor and cysts, there are other infections such as rubella, CMV and lymphocytic chroiomeningitis virus, syphilis and Zika. It would be fanciful to consider intraventricular neurocysticercosis though in a review from Nepal involving 229 cases, the youngest patient was 11 months of age. I couldn’t find a single case report of congenital/neonatal neurocysticercosis. 

PD7 gives a chilling account of toxoplasma with such statements as “one of the most successful parasites on earth” and “It can remain alive as a dormant infection for the life of the host.” Cats (felidae) are the definitive hosts. Rodents, humans, birds and a wide variety of other animals are incidental hosts. Another bright spot, in addition to the ‘good outcomes’ news cited above, the majority of congenital toxoplasma infections are asymptomatic. Vis a vis transmission: avoid cat feces and raw and undercooked flesh. 

What causes the hydrocephalus? A review by Hutson involving 210 patients showed that CSF flow was blocked in various intraventricular locations, though no obstruction could be demonstrated in 21% of cases. Ventriculitis and subsequent obstruction of CSF flow is postulated as the cause of the fluid accumulation. 

Speaking of parasites and the puerperium, a reference that I stumbled across stated that ascaris infected women were actually more fecund than noninfected. Hookworm infection however was associated with decreased fecundity. Go figure.

As intimated earlier, treatment of the neonate with sulfadiazine and pyrimethamine and ventriculoperitoneal shunt if needed has been shown to improve motor and cognitive outcomes. 

One last thing. The privileged home of toxoplasma in the brain gives it an opportunity to be something of a puppet master, and the literature on the parasite’s effects on host behavior is the subject of a large number of papers. Could an asymptomatic chronic cerebral toxoplasma infection direct the host, (who may simultaneously be the host of a barbecue) to serve undercooked infected meat to his guests? ‘Tis food for thought. Bad thoughts. 

I end with an adage, one quoted by Erasmus in his Adagia: percussus resurgo(Struck down, I rise again). 

Thanks and strength to thee three.

ENDNOTES (09/23/2019)

Kalipatnam Seshagiri Rao,et al, Time trend of neuro- cysticercosis in children with seizures in a tertiary hospital of western Nepal, PLOS May 10, 2017

Persson G, Ekmann JR, Hviid TVF. Reflections upon immunological mechanisms involved in fertility, pregnancy and parasite infections. J Reprod Immunol. 2019 Nov;136:  Authors cite Blackwell et al 2015–Tsimane people, experiencing natural fertility and a helminth prevalence as high as 70%. After correcting for likely confounding effects that could influence fecundity, they showed that women infected with the roundworm Ascaris lumbriocoides achieved pregnancy for the first time at an earlier age and showed significantly increased chances for pregnancy under the age of 32 years compared with non-infected women (hazard ratio (HR)=3.06; confidence interval (CI): 1.91–4.91; P < 0.001). Moreover, seen across the life span of the women, an infected woman was expected to give birth to two more children than women, who were never infected…Contrast the above with hookworm infection, which results in a delay in first pregnancy and a greatly reduced fecundity. 

Samuel L. Hutson et al. Patterns of Hydrocephalus Caused by Congenital Toxoplasma gondii Infection Associate With Parasite Genetics Clin Infect Dis. 2015 Dec 15; 61(12): 1831–1834.

Sarah Dotters-Katz et al, Parasitic Infections in Pregnancy, Obstetrical and Gynecological Survey, 2011; Volume 66, Number 8 …some parasites primarily affect the mother (helminths), others the placenta (schistosomes, malaria), and others the fetus (leishmania, filaria, toxoplasma). The authors invoke the Dawkins concept of ‘extended phenotype’, where an animals behavior will maximize the survival of the genes governing that behavior, regardless of the origin of those genes (i.e. it don’t matter if the genes are from the host or the parasite…)

McLeod R, Boyer K, Karrison T, Kasza K, Swisher C, Roizen N, Jalbrzikowski J, Remington J, Heydemann P, Noble AG, Mets M, Holfels E, Withers S, Latkany P, Meier P; Toxoplasmosis Study Group. Outcome of treatment for congenital toxoplasmosis, 1981-2004: the National Collaborative Chicago-Based, Congenital Toxoplasmosis Study. Clin Infect Dis. 2006 May 15;42(10):1383-94. doi: 10.1086/501360. Epub 2006 Apr 11. PMID: 16619149.

McLone D, Frim D, Penn R, Swisher CN, Heydemann P, Boyer KM, Noble AG, Rabiah PK, Withers S, Wroblewski K, Karrison T, Hutson S, Wheeler K, Cohen W, Lykins J, McLeod R. Outcomes of hydrocephalus secondary to congenital toxoplasmosis. J Neurosurg Pediatr. 2019 Sep 6:1-8. n=65 cognition & motor skills were scored….delayed shunt placement (>25 days beyond time of dx)was associated with worse outcomes….

Roizen N, Swisher CN, Stein MA, Hopkins J, Boyer KM, Holfels E, Mets MB, Stein L, Patel D, Meier P, et al. Neurologic and developmental outcome in treated congenital toxoplasmosis. Pediatrics. 1995 Jan;95(1):11-20.  36 children in study. Were treated during the first months of life for ONE YEAR with sulfadiazine/pyrimethamine…Conclusions: Neurologic and developmental outcomes were significantly better for most of these treated children than outcomes reported for untreated children or those treated for only 1 month (P < .001). Study was conducted between 1981-1991

McConkey GA, Martin HL, Bristow GC, Webster JP. Toxoplasma gondii infection and behaviour – location, location, location?. J Exp Biol. 2013;216(Pt 1):113-119. doi:10.1242/jeb.074153  Hypotheses that propose a parasite advantage in tissue tropism, specifically: parasite location in the brain results in host behavior change that benefits the parasite….Brain parasite may strip away rodents’ fear of predators—not just of cats Science Jan. 14, 2020 …n several other behavioral tests, the team found that infected mice showed less anxiety and a stronger tendency to explore. For example, they spent more time in the arms of a maze that were open and exposed—areas that mice typically find threatening….T. gondii “clearly manipulates the crap out of the host,” says Laura Knoll, a parasitologist at the University of Wisconsin, Madison…Up to one-third of humans are thought to harbor a T. gondii infection, known as toxoplasmosis, and some research has linked it to schizophrenia and other mental illness.


PD7 schooled me up on the origins of the genus/species name of our parasite….Ctenodactylus gundi, the common gundi, native to North Africa. The animal that Nicoll first found the organism named Toxoplasma gondii. Maybe a bit cute, the gundi, not the toxo. 

Intimations of coming curiosities; A recent NYT story about scientists testing their homemade SARS-CoV-2 brews on themselves reminded me that I want to outline some of the bold self-experiments performed by parasitologists, as well as the inadvertent infections (many fatal) suffered by earlier investigators. It will not be titled “Curiosity Killed the Parasitologist”…I will begin with the great but possibly apocryphal Hunterian experiment….stay tuned. Dr. Despommier’s ruminations will be appreciated. 

University of Central Lancashire Parasitology Club   writes:

Dear TWIP Professors,  

Hello from the Parasitology Club at the University of Central Lancashire  located in the  beautiful  North West of England.  

The Parasitology Club believes that Toxoplasma gondii (which causes  Toxoplasmosis and, more specifically, Congenital Toxoplasmosis) is the  cause of the baby’s enlarged head.  

Toxoplasma  is commonly found in  cat’s  faeces and the Toxoplasma gondii  oocytes  can be  transmitted into other  intermediate  hosts  through ingestion of contaminated  materials. The pregnant woman in this  case is likely to have been infected with toxoplasmosis by consuming unwashed vegetables  (contaminated with oocytes)  or undercooked meat (provided by her husband) of animals containing tissue cysts. 

Individuals with a strong immune system usually experience no or mild symptoms. However, pregnant women are more vulnerable to infection especially if infected a few months before conceiving or during pregnancy. Congenital infection occurs after primary infection of a pregnant woman and according to McAuley (2014), the severity of symptoms is inversely related to the gestational age at the time of infection – severe clinical disease would be displayed in an infant whose mother was infected during the first trimester.  If she had the infection months before the pregnancy the immune system would have created antibodies to fight the parasite leading to minor symptoms or immunity.  

We appreciate the case studies that are provided  and are very thankful for the podcasts.   

Yours  sincerely  


on behalf of the University of Central Lancashire Parasitology Club  

 References McAuley, J. B. (2014) ‘Congenital Toxoplasmosis’, Journal of the Pediatric Infectious Diseases Society, 3(Suppl 1), pp. S30 – S35.