Infection with rat lungworm, Angiostrongylus cantonensis.
Several of the patient’s symptoms suggest CNS involvement, and the eosinophilia found by lumbar puncture helped me narrow down possible causes, being possibly indicative of eosinophilic meningitis. A few parasitic nematodes are closely associated with this condition, and the patient’s recent visit to Hawaii implicates one in particular: Angiostrongylus cantonensis, the rat lungworm. Humans are incidental hosts, and can acquire the infection by consuming L3s in slugs and snails, with symptoms arising when the worms die in the meninges. Given her history, the salad is likely to blame.
Diagnosis cannot be made directly, so her symptoms and history must suffice. Disappointingly, no specific treatment is suggested, so she would need to wait for the infection to resolve on its own (typically 2 – 8 weeks), but during this time serious neurologic sequelae and death can occur. Very interesting parasite, but this neurotropism is kind of sobering.
As an odd counterpart to the earthworm story you related in the last episode, this lungworm has been contracted from the socially motivated consumption of slugs.
Looking forward to your thoughts,
Chris (in Athens, GA)
A cháirde TWIP,
After my long email last episode I will be nice to Dickson and endeavor to keep them shorter.
To investigate this case study I was joined by Gwen Deslyper, Paula Tierney. Rachel Byrne couldn’t be there but sent her thoughts by email.
Lots of symptoms and a detailed case history given, originally making us feel despondent as our list of possible important factors grew longer and longer. One thing stood out, a suspect salad in Hawaii. It made us think of Angiostrongyliasis or rat lungworm disease, caused by the parasite Angiostrongylus cantonensis. We searched the literature and one by one we were able to tick off the symptoms: Itchy rash on chest, back and abdomen, waning pins and needles and worsening stabbing pain, febrile, painful and slow movement of extremities, 32% eosinophilia in the cerebrospinal fluid and higher than usual levels of proteins. All symptoms linked to Angiostrongyliasis. Our despondency turned to euphoria. That of course does not mean we are right, but we did have a nice parasitic journey of discovery. Diagnostic tools seem still under development, but we did find reports of some success carrying out PCR on the cerebrospinal fluid. Supportive treatment should be carried out. Using anthelmintic treatment is controversial due to fears of complications caused by dying worms. Infection most likely via ingestion of a snail or slug in the salad, most likely via the invasive semi slug Pamarion martensi. Prevention by thoroughly washing hands, fruit and veg and properly cooking paratenic hosts such as frogs and shrimp. Also increased biosecurity to stop more reservoir hosts arriving and ecological based pest management to keep those already present in check. Also of course further funding for Paula and I, who work on parasites in bio-invasion systems.
Interestingly just last week Rachel found a different Angiostrongylus species in some badger lungs. It was interesting as although it had been frozen for 6 months, then thawed and refrozen the larvae were still alive (video here). Best to be sure to flash freeze your sushi shrimp and not just freeze it!
Finally I would have taken part in the schisto infection programme. Although not intentionally infected, I did catch pummula hantavirus. I knew through my work with bank voles in Finland there was a high risk of infection but low risk of serious virulence. I had better odds than I did each time I got into my car.
PS Hope it is ok to plug a recent blogpost for the Royal Society of Tropical Medicine and Hygiene by Gwen on Ascaris Wormy people: why some people are wormier than others
Dear TwIP hosts,
My guess is Angiostrongylus cantonensis, the rat lungworm.
I first thought about Loeffler’s syndrome with Ascaris and Strongyloides, which you mentioned earlier in the podcast both involve larva migrating through the lungs. The neurological findings had me stumped and mulling over whether the lesion was in the lower spinal cord or somewhere equivalent, and perhaps caused by neurocysticercosis (which I hadn’t heard of in Hawaii). I decided I’d review all the nematodes when I finished driving home. Then, the information about eosinophils in the lumbar puncture came along. Since the causes of eosinophilic meningitis are few, the clue had me fixated on searching precisely that term when I got home.
There’s a twist – I actually grew up in Hawaii. Facebook posts from friends back home are a large chunk of my home page feed, including articles in the local news a while back (sandwiched by appropriate emojis and #hashtags) about a terrifying-sounding disease: “rat lungworm”, which has emerged over the past few years on contaminated greens*. Given the recentness of the patient’s case, and my gut instinct that most helminthiases are very rare in Hawaii and the patient’s other developed-world destinations, I wondered if there could be a connection…
It was too much to resist, so upon parking my car I looked up ‘rat lungworm’ instead of ‘eosinophilic meningitis’. To my astonishment I found that Angiostrongylus is indeed the most common parasitic cause of eosinophilic meningitis. (Is it also the most common cause even in the USA?)
I feel quite bad for our patient to have contracted this disease, especially in my beautiful and otherwise generally safe home state, and I wish her a speedy and complication-free recovery.
I am a family doctor from Darwin, Australia. I came across your podcast while studying the Diploma of Tropical Medicine and Hygiene in Liverpool last year. I listen to your podcast most weeks while i do the washing up. I was most interested in the brief mention of eating garden worms at the beginning of last podcast. You may have heard the story of the rugby player in Sydney who acquired rat lungworm from completing a dare to eat a garden slug. Sadly he developed eosinophilic meningitis and several years down the track he is basically in a vegetative state. (The case has recently come back into light as the government assistance package for him is being reduced.) My veterinarian wife tells me that this type of worm is only prevalent mainly in the temperate parts of Australia, but perhaps that is just where they have been tracking it. Interestingly a brief google search to a veterinary article indicates that the inebriated adult male on a dare, eg on a buck’s night is not an isolated incident, at least in Australia!
Do you know the rates of infection in countries like Australia and also in South East Asia??
I believe the teenager from NYC is suffering from scabies infection from the mite Sarcoptes scabiei. The mites burrow into the skin to live and reproduce, and their presence causes an allergic reaction in the skin. To me, the smoking gun lay in the clue that the itching became worse at night, a common trait in scabies infection. This reaction to the mite builds over time, and there is a typical delay of about 4-6 weeks between the infestation and the onset of the itching. Furthermore, even after the mites are eradicated, symptoms may persist for one or more weeks after treatment. As scabies is a common condition found across the globe, it might be difficult to pinpoint exactly where she was infested with the mites, but she might be able to trace back to the original site if she remembers where she was 4-6 weeks before her symptoms began. She might have also contracted these mites from her dog, as they have been known to transmit the Sarcoptes mites as well. Treatment for scabies includes permethrin or ivermectin.
Thank you once again for the informative and entertaining podcasts.
I was very excited to hear that I won the book last week, and in the off-chance that this diagnostic email is selected as the winner, I would like to donate that book to another emailer.
Dear TWIP Triumvirate,
I am writing to weigh in on the teenager with eosinophilic meningitis from episode 148. As a private-practice ID doc, I have enjoyed recently finding this podcast and the related cousins in the microbe.tv universe. They are an interesting diversion from the usual daily grind of leg cellulitis and contaminated blood cultures!
Your teenaged patient almost certainly has Angiostrongylus infection. This is human infection with the rat lungworm and can present with the constellation of symptoms and findings that were mentioned – fevers, pruritic rash, mild eosinophilia, paresthesias, and meningitis. She is not depicted as particularly toxic, which also fits the picture. I suspect the infection was contracted during the family trip to Hawaii (Mahalo! What a great souvenir!), and may have involved the salad mentioned, though it was not clear where this was consumed. Diagnosis is usually clinical unless a migrating larva happened to be seen in the CSF, though I believe serology is available. Treatment would be with steroids and repeated LPs for pressure/headache control. Perhaps this is the reason for the readmission teased at the end of the presentation.
The aforementioned readmission did make me think that something more serious might be afoot. Strictly based on eosinophilic meningitis, Gnathostomiasis or Baylisascarasis would have to also be in the differential, though both typically cause a more severe CNS presentation and have more significant peripheral eosinophilia. She doesn’t really have good exposure history for either. I am also leaving out Coccidioides since this is not a mycology podcast.
So my final answer is Angiostrongylus.
Thank you for this interesting consultation. I will continue to follow with you and am always available to answer your questions about this or any other case.
Leland Allen MD
Associated Medical Group, P.C.
Southeastern Infectious Diseases
Currently 13 C and sunny
Hello dear TWiP hosts!
My name is Susanna and I work at a clinical microbiology laboratory in Stockholm, Sweden, where I am one of the lucky ones that gets the chance to look at all the beautiful parasites under the microscope!
I found this podcast 2 months ago and i absolutely love it!
These case studies are the best and this is the first time I’m sending you my guess, hoping it’s not too late.
So here is my guess for the case study for TWiP 148
I believe that this teenage girl has been infected by Angiostrongylus cantonensis, the rat lung worm, which is the most common cause of eosinophilic meningitis. I have heard the name of this parasite before, but i have never really read a lot about it so this is a bit new for me (which is fun!) and here is what i found out.
Angiostrongylus cantonensis is a nematode that has rats as its definitive host and snails and slugs as intermediate hosts. Some other animals such as freshwater shrimp, crabs, or frogs can get infected if they ingest snails or slugs (or parts of them). Humans can become infected if they eat raw/undercooked snails or slugs or raw/undercooked frogs, crabs or shrimps. It is also possible to get the infection by eating raw produce, such as lettuce, that contains small snails or slugs (or parts of them).
Most infected people don’t get any symptoms or get very mild symptoms that don’t last for long.
When symptoms are present they may include headache, stiff neck, fever, nausea, vomiting, photophobia, visual disturbances and tingling or painful feelings in skin or extremities.
So, I know that this girl did not have all the most common symptoms for eosinophilic meningitis but this will still be my guess because:
- She has been to Hawaii, where this parasite has been found.
- She ate a salad that no one else in the family ate and it is a possible source for the infection.
- Even if she does not have all the typical symptoms for eosinophilic meningitis the abnormal feeling in her legs is something that could be caused by this parasite.
- She had increased white cells with 32% eosinophils in her CSF which is a typical sign of eosinophilic meningitis.
Ok, so i hope my guess is right but even if it’s not it was very interesting to read about this parasite that i did not know a lot about before.
Thank you again for your awesome podcast!
Aloha nā Kumu TWIP,
Warm greetings from the Big Island where its 28ºC at the coast, 25ºC where I live and -7ºC at the top of the hill behind me.
The patient in your case study, with pins and needles sensations in her legs, progressing to more painful stabbing pains, along with eosinophilia in the CNS, sounds like it could be a Neuroparasitic nematode infection.
I would want to differentiate among nematodes such as
Baylisacaris, Gnathostoma, Strongyloides, Toxocara and Angiostrongylus.
Gnathostoma could have the pain, paresthesia and strange rash from migrating larvae, but she doesn’t have the history of eating raw fish or visiting Thailand.
Covert Toxocariasis: Patient is considerably older than a typical Toxocara patient, but Toxocara can cause a rash. No ocular, liver or spleen involvement were described.
Baylisacaris and Strongyloides don’t typically cause paresthesias.
However having lived on the Big Island of Hawaii for 3 1/2 decades, your patient’s recent visit to our island and recollection of eating not raw fish but a lettuce salad, made me think that this might be Angiostrongylus cantonensis or rat lungworm disease. While we have probably had a very, very low prevalence on our island at least since the 1960s, we had 17 cases last year, including a few that made it to other islands and the US mainland. I returned from Nepal last week to find we had had our first Rat Lungworm case of 2018 about 100 m from my office. That case seems to have resolved successfully but neither steroids nor antihelmenthics have appeared very helpful.
And like any disease that can affect the brain, has no specific cure, and sometimes causes lasting intractable pain, it has risen as a public concern even as the prevalence has remained low.
The primary reservoir are rats (certainly the three species we have here in Hawaii: Norways (Rattus norvegicus), black rats (Rattus rattus), and Polynesian rats (Rattus exulans) but apparently not mice or mongoose. The rats then pass 1st stage larvae in their stool which can infect several species of slugs, semi-slugs and Giant snails if they feed on the rat feces. People cannot be infected by the the 1st stage larvae in rat feces but can be infected by 3rd stage larvae if they should eat a raw slug or semi-slug for instance on a piece of incompletely washed lettuce (a young semi-slug is about the size of a piece of rice). There may be other routes of infection: a few 3rd stage larvae can be detected in slug slime and they can live in water for up to 72 hours, but my understanding is that human infection from contact with slug slime trails is not presently a confirmed route. Rats typically eat the infected slugs or semi-slugs and complete the nematodes life cycle, but in humans the infection is a dead end, often without symptoms or only flu-like symptoms, but if the nematodes invade the brain and CNS then an infected patient typically presents with fever, bitemporal or frontal headache, and meningismus often along with vomiting and migrating painful paresthesias. It certainly would explain the eosinophilia in the CNS, but my “what am I missing radar” is going off as your patient did not present with a headache and I’m not sure my guess of Angiostrongylus really explains the itchy rash.
Look forward to your guest’s diagnosis and discussion on case management.
Will use the Parasitic Disease 6th Ed with our Primary Health Care students should I win.
Again, keep up this wonderful labor of love. Best podcast out there!