James writes:

Hello all TWiPers

I believe I wrote about this in a couple of Substack posts, likely Looking at

AGS (Alpha-gal Syndrome). Both have been addressed in MMWR and a HAN

alert. This is spreading with the effect of climate change.

Updates on previous posts and COFFEE!


DEC 3, 2023



Håkon writes:


This week was sure a thinker- not sure I got there but given the spartan race hint and the active outdoors work and urticaria and asthma the only thing I could come up with that had all the symptoms in one would be a strongyloides infection. Seemed like giardia and being allergic to even small amounts of dog dander would potentially do it as well. Best wishes this holiday seasons-


Mikayil writes:

Dear TWIP team,

As I write this, here in Knoxville, Tennessee, it is a gloomy and rainy Christmas day. I am lucky enough to be working a split shift at the veterinary hospital, so I have a relatively sizable break to rest and reply to this episode’s case.

I spent a good few hours pondering this case. I thought that my veterinary background would aid me in this case, but I think I overestimated the degree to which it was helpful. 

In the case of the man with sudden diarrhea and presumably anaphylactic reaction. I originally thought the diarrhea was a red herring, as if there was involvement of an endoparasite it would warrant treatment beyond a simple “change in lifestyle.” Continuing down that down that line of thinking, the cause of this man’s anaphylaxis may have been caused by an allergic reaction from the bites of fleas/and or other mites that he could’ve acquired from his “hypoallergenic” dog (for those unaware there is sadly no such things, as human allergy is usually caused by dog dander, not the shedding of fur). If it were a mite infection a “change of lifestyle” could be a potential treatment, but there’s no mention of profuse skin lesions aside from hives or treatment of the man’s environment which would be warranted if there was some kind of flea or mite infestation.

Thinking of other canine ectoparasites and after discussing the case with a friend, I remembered how a specific parasite can lead to the development of an allergy. This would explain the diarrhea, anaphylaxis, lack of antiparasitic treatment, mention of the specific region, and Dr. Griffin’s question about the patient’s diet. I believe this man has a case of Alpha-gal syndrome, which leads to an allergy to red meat. He must have acquired this after being bitten by Amblyomma Amerinacum (the lone star tick), which he may have picked up either from his dog or on one of his hikes through the Tennessee wilderness. As long as he avoids eating red meat he can avoid future anaphylactic episodes, and I would also verify that his dog is on flea and tick preventatives in case that is how he acquired the tick.

Thank you for another great case! I hope I will be in the running for a textbook!



Inge writes:<=winner

Warm greetings from the cool and wet north of the Netherlands, where we are experiencing a wet and windy tail of storm Gerrit passing over the UK with a typical 11 degrees Celsius. To my disappointment I noticed I was a mere one day late with my response to the previous case. I’ve pushed my research for the next case more to the front, hoping to be on time for this case, which was quite the challenge. I hope to have thought somewhat in the right direction and take part in the chance for winning a book. 

The case of a 41-year old man from Tennessee with episodes of GI distress with diarrhea and complaints of urticaria, shortness of breath and wheezing with ultimately what appears to be an anaphylaxis-like symptoms. After researching these complaints it seems that there are quite a number of parasites that could cause both GI and allergic complaints. Among those that may appear in the US and are more likely in semi-rural communities, the ones that jump most to the front for me are echinococcus (both granulosus and multilocaris), ascaris lumbricoides and strongyloides stercoralis. Echinococcus could cause GI complaints when a cyst ruptures with fluid irritating the peritoneal cavity, and its rupture leading to allergic reactions. Ascaris is known to cause both GI complaints and Loeffler’s syndrome with asthmatic complaints and bronchial hyperreactivity and can lead to anaphylaxis during worm migration. Strongyloides is known to cause GI complaints and can cause pulmonary complaints amongst which are bronchial hyperreactivity and urticaria. However, there are more parasites that should be thought of, including toxocara and the hookworms. As for the experienced ED physician recognizing the complaints from similar cases, I commend him, but I’m not as experienced in which of these or other pathologies could be most likely here. I would therefore recommend broad diagnostic tests, at least including a stool exam, preferably high volume with sedimentation, as to increase the likelihood of catching strongyloides if present, as well as serodiagnosis for echinococcus. Imaging studies could be done as well, for echinococcus, in which case I would start with ultrasound of the liver, but wait with further imaging studies until serodiagnosis is returned, or unless the patient’s complaints continue to progress. In that case a more speedy tract may be necessary. In that case a CT could be recommended, if cysts are seen, surgical evaluation may be necessary but oral treatment with albendazole is recommended. In the case of no cysts it could be opted to treat with ivermectin for strongyloides and albendazole for ascaris, where albendazole may have some added benefit for treating strongyloides as well.    

Kind regards and many well wishes for the upcoming New Years, 


Christian writes:
Dear Twip Team,

Greetings from rainy Basel.

I think that the recurring and intensifying allergic reactions of the patient in addition to the geography and his outdoor activities makes it very likely that this is a case of alpha-gal syndrome.

AGS is an incredibly interesting problem, as it is caused by the saliva of the lone star tick, with some other species potentially being able to cause it too.

However, AGS is particularly intriguing as it is thought that we as a species, apes and old-world monkeys have lost the ability to produce galactose-alpha-1,3-galactose (alpha-gal) due to evolutionary pressures millions of years ago in our common ancestor. Therefore, now the immune system recognizes it as foreign. Also, a problem involving xenotransplants of organs.

There are even more peculiar factoids to it, such as AGS being a delayed food allergy, and an allergy against a carbohydrate and not a protein.

For this patient it would therfore be important to avoid any meat of mammals to prevent further allergic reactions and with a bit of luck he will be able to eat meat again in a not so distant future.

Best Wishes,


Jay writes:

Dear TWiP Team, 

This 41 year-old man’s symptoms — along with his improvement after a lifestyle intervention — are consistent with the alpha-gal syndrome.  

It’s often helpful to cast a wide net when developing a differential diagnosis. Even when we suspect there is an infectious (or more specifically parasitic cause) to a condition, we should consider non-infectious causes as well.  

There were some strong clues that led to this diagnosis. He has allergies, so much so that he chose a hypoallergenic dog, Rafael. His current symptoms began after moving to Chattanooga, a part of the country where the lone-star tick is common. His severe symptoms improved with bronchodilators, intramuscular epinephrine, and antihistamines.  

The clincher is that the ED physician ordered a diagnostic test, and the man’s symptoms abated with a lifestyle intervention.  I suspect the diagnostic test was an alpha-gal IgE panel and the lifestyle intervention consisted of a change in diet (avoidance of mammalian meat and dairy products). It was also likely recommended that he keep an epi-pen and antihistamines on hand and that he does what he can to avoid further tick bites.  

Alpha-gal syndrome (AGS) is an allergy to a carbohydrate, galactose-a-1,3-galactose (aka alpha-gal). Alpha-gal is found in all non-primate mammals. Alpha-gal is also found in the saliva of the lone-star tick. When a lone-star ticks bites, it passes alpha-gal on through its saliva. For someone with AGS, this exposure to alpha-gal eventually leads to immune sensitization. The immune system becomes hyper-sensitive to alpha-gal, and, as a result, exposure to small amounts of it – such as the mammalian meat this omnivorous man ate – leads to an allergic reaction 2 – 6 hours after ingestion. 

The syndrome does not occur when eating non-mammalian meats such as chicken and fish. He can continue to be an omnivore, just a more selective one. AGS also occurs worldwide. In the US, the bite of the lone-star tick leads to this immune sensitization. Alpha-gal is found in other tick species elsewhere in the world. 

This case is a good reminder to cast a wide net when developing one’s differential diagnosis. 

Thank you. Keep up your great work. 


Jay Gladstein, M.D. | Chief Medical Officer

APLA Health & Wellness

First Vienna Parasitology Passion Club writes:

Dear alpha-gals and alpha-guys,

The case presented is consistent with alpha-gal syndrome, a kind of allergy to mammalian meat. While we would usually give some information about epidemiology, pathophysiology, diagnosis and treatment of the disease, we feel that this is not necessary at this time.

Just a few days ago, our very own Michelle Naegeli published a article on the AMS website which can be found here: https://asm.org/Articles/2023/December/Alpha-gal-Syndrome-When-a-Tick-Bite-Turns-to-a-Mea . It outlines everything the casual listener should know about the syndrome, so we shall leave you with that.

However, it is interesting to note that there is, as of now, no consensus within our club on whether or not people being unable to eat mammalian meat is actually a bad thing.

Thank you for this great case. All the best, 

Michelle and Alexander from the First Vienna Parasitology Passion Club

PS: The voice artist is really doing a fantastic job, especially concerning the difficult pronunciations! However, we both miss the character that your own readings lend to the letters, including your quips, comments and tangents.

Michelle & Alex

Rafid writes:

Hello TWip team,

Greetings from wintry Quebec. I would like to take a moment to thank the TWIP team and Vincent in particular for sending me the Parasitology book which I received on Christmas Eve in the mail. I have been thoroughly enjoying this book. It is detailed and at the same time to the point, written in a simple and clear language. It is a rare gift to be able to express complex information in such a readable way. It will definitely be a cherished part of my library for years to come. I also really appreciate that it signed. I cannot thank you enough.

Back to the case at hand, Our hospitals are still full of the  unvaccinated masses suffering respiratory, cardiac and other complications of respiratory viruses so I have been pretty busy lately so I will not be able to give a broad differential diagnosis for this challenging case that I admit has left me stumped. If I had to make a quick guess as to a dog owner who lives in a hot climate and tends to his rural plot of land and develops intermittent urticaria, GI and respiratory symptoms, I would say that toxocaria canis infection would definitely be possible. I did read the excellent chapter 27 on Aberrant nematode infections in my new personally signed book on Parasitic diseases and although many zoonotic nematodes can cause urticaria, most are quite rare. T. Canis seems to be the most likely culprit in this case. Looking forward to hear the answer.


Felix writes:

Dear hosts,

I am unsure this time, but some research brought up parasitic nematodes called Anisakis which then causes allergic reactions. The dog really doesn’t fit the picture and there was no mentioning of raw fish consumption but the symptoms on the other hand fit really well. The lifestyle intervention mentioned would be to skip the tasty sushi, which is quite a tough one.

Props to the ED physician for getting that one right!



Leon writes:

Hello dear TWIP team,

The 41-year-old male from the US experiencing GI distress, itchy hives, and trouble breathing likely suffers from an infection with Strongyloides stercoralis. Infection usually occurs by coming into contact with soil containing the infectious filariform larvae of this nematode. The larvae penetrate the skin, enter subcutaneous lymphatic vessels, and travel to the lungs. Parasites that reach the tracheobronchial tree are coughed up and swallowed, ultimately ending up in the small intestines, where they complete their life cycle to be either passed out into the outside world or reinfect the host.

The itchy rash aligns with symptoms caused by the entry of larvae into the skin. Diarrhea is a consequence of the parasite residing in the GI tract, and shortness of breath corresponds to its presence in the lungs, causing irritation as the larvae migrate. This may be exacerbated by his asthma. I have very limited medical knowledge but could the intake of Benadryl may have caused the sudden exacerbation of the respiratory problems? 

He likely contracted the infection through contact with contaminated soil during his various outdoor activities. Alternatively, he could have obtained the infection from getting in contact with feces of his dog which could be infected as well.

The disease can be easily diagnosed with an antibody test or microscope analysis. Ivermectin would be the first line treatment. To prevent future infections, the individual should wear shoes when walking on soil, avoid contact with fecal material, such as that of his dog, and wash his hands regularly. Testing and treating the dog may also be considered to exclude this potential source of infection.

On a side note: While backpacking through Guatemala and South Mexico this summer, I was surprised that within seven weeks of travelling, hardly any locals I spoke to know about Chagas or Leishmania. Is this normal? Only the doctors in Antigua in the hospital were aware of it while suffering from a severe case of Montezuma’s revenge (unfortunately, it turned out to be a bacterial infection, I was already excited to share my case with you.) Is there really such a lack of public awareness of these diseases?

I hope this time i have a correct answer, since the last time i failed to do so…and finally get a book.

Greetings from the smaller and older York in England,


Justin writes:

Hello all,

It has been a while since I last guessed, and I thought I should take a shot at this one.

The location of Tennessee and the semi-rural living conditions made me think of hookworm.

The GI distress and the rash fit well for hookworm, and respiratory problems can also be seen in hookworm cases.

I am puzzled that the only treatment was a lifestyle intervention and no medication, but if a lifestyle intervention was suggested for a hookworm patient, I would guess it involves fecal sanitation and wearing shoes outdoors as hookworms are a soil-transmitted helminth.

Therefore, my guess would be one of the hookworms.

Thanks for the lovely podcast,