Disseminated Strongyloides and Hyperinfection
If you've ever rotated through any type of rotation that involves an immunocompromised host, your boss will have obsessed over the same few bugs. Including the parasite strongyloides. Aka threadworm.
They will never forget it, nor will they let you. They all seem to have that one case of disseminated disease that got missed and ended badly. Of all the bugs in the world to screen prior to starting significant immunosuppression, this is one of them, along side HIV, viral hepatitis and TB.
It's endemic to tropical environments in the developing world.
The concern is hyperinfection and disseminated disease in the case of the immunocompromised, in which case the mortality is 90%.
Hence the universal acceptance of screening for it in serology (I.e. IgG) in patients about to be immunocompromised on long term or high dose steroids. I.e. solid organ transplants, BMTs, rheumatology patients needing strong long term immunosuppression etc.
image source: NEJM, Case report ssx: rash and diarrhoea after starting steroids for malignant spinal cord compression (common practice), preceded by intermittent eosinophilia (the WCCs that are directed against parasites etc.)
The how: As part of it's infective lifestyle, the larva penetrate the skin, and via skin & the mucosal layers, it enters the blood stream, travels to the right heart and into the lungs. As the host coughs, they swallow the larvae and it enters the GI. Does that sound completely skin crawling and eerie?
Clinical manifestations:
Pulmonary - eosinophilic pneumonitis (the WCCs directed at parasites increase and are the sources of inflammation in the lungs), alveolar bleeding from larval damage (yikes). On CT imaging, essentially you just see ground glass changes - non specific findings of inflammation (which can be caused by a huge array of things, of which, disseminated strongyloides would actually be the last on your list if you're not in an endemic area...). classic presentation in any GG inflammation is SOB, sometimes cough.
GI: larvae mature, embed into the intestinal mucosa and produce eggs. The eggs perpetuate the lifecycle and the host gets diarrhoea, abdominal pain etc.
Skin - rash, from dissemination of the larvae but also at the penetration site (may go unnoticed).
So then what's hyperinfection?
T cell mediated immunity is suppressed in immunosuppression either by broadly suppresive steroids (dexamethasone, prednisolone etc.) Or transplant patients on therapy directed at the T cells, in order to prevent them rejecting their organs (maybe I'm still doing this, I'll make a blog on rejection).
Hyperinflation...wait.. hyperinflation..freudian slip but equally bad.
I mean hyperinfection results from the immune system leaving the worms to proliferate unchecked. "Excessive" worms are seen in usual affected organs - skin, lungs and gut. So expect an excess in clinical presentation, bloody diarrhoea, weight loss, malabsorption etc.
Disseminated disease occurs when it spreads outside the 'usual' routes of skin, lungs, gut and the numbers lead to catastrophic damage. Respiratory failure, AKI, shock, DIC, meningitis. Can spread widely to liver, heart, etc.
As added flavour, it can also lead to gut bugs causing bacteraemia. E.g. Ecoli, strep bovis (so look for malignancy as well as Strongyloides).
Given how devastating severe disease is, it's common practice for any immunocompromised host with eosinophilia and who's traveled to the subtropics/tropics to be screened. I've seen some really paranoid ones will send off serology on seeing eosinophilia.
As the bug can autoinfect a host, expect it to be there for a lifetime once infected.
Chronic/mild forms of the disease present as well, chronic GI symptoms (heart burn, anorexia, reflux, abdo pain, diarrhoea) and is often mistaken for IBD. Hence the importance of scopes and biopsies given therapy for IBD is immunosuppression.
investigations: easy pick up on biopsy if scoped or bronch'd. otherwise, serology. Suspect it on seeing eosinophilia. Stool mCS also an option. in chronic disease - mildly elevated eosinophilia and elevated IgE
Treatment of strongyloides vs hyperinfection: ivermectin or albendazole. Ivermectin is so infamous now post pandemic.
Issues: serology can take time to return, if in doubt, I've see some consultants/attendings empirically treat with ivermectin because the risk of mortality in hyperinfection is so high. But only in cases where patients are from or travelled to endemic areas. It's considered low risk if they have done neither.
Sources (will always aim for free ones)
Gastroenterology & Hepatology Journal 2011
Give me a shout if you've treated this!
