Thread by @BoggildLab

1/19 Hope you can take a break from COVID-19 & Mpox reading for a Tuesday tweetorial on Eosinophilia in the Returned Traveler. This has taken me all of pandemic to push out but with planes in the sky, now is the time to be prepared😊 Buckle up for some serious tissue invasion🪱

2/19 Eosinophils participate in the critical Th2 arm of immunological control of helminthic infections through Fc-receptor-mediated IgE approximation to worm tegument followed by degranulation. Most labs & literature define eosinophils as ⬆️ when they are bw 0.4-0.5 bil/L

3/19 My approach to Parasitic causes of Eosinophilia categorizes the level of eosinophilia as Absent (<400), Mild (400-1000), Moderate (1000-3000), or High (>3000)

4/19 Blood & tissue protozoa + stool protozoa (w/ few exceptions) tend not to cause eosinophilia; thus, ⬆️ eos in your malaria, leish or giardia patient should raise concern for a competing / intercurrent infection, particularly in those born in STH- & schisto endemic regions

5/19 Mild eosinophilia often occurs in the setting of enteric Dientamoeba fragilis or Cystoisospora infection, with certain unencysted nematode larval infections like CLM, & with some enteric nematode infections such as strongyloidiasis (classic eo count 600-800) or hookworm

6/19 CLM occurs due to larval migration of dog or cat hookworm following penetration of intact skin (often of the feet) that has contacted fecally contaminated sand or soil. For more, see our paper on CLM in TMAID:
sciencedirect.com/science/articl…

@PatSchlagenhauf

7/19 Larva Currens occurs when larvae of Strongyloides migrate rapidly under the skin, producing a CLM-like eruption that is not quite as pruritic or topographical. Rapid rate of migration helps differentiate larva currens from CLM (several cm/hr): researchgate.net/publication/27…

8/19 On the DDx of mild eosinophilia are non-helminthic infections such as coccidioidomycosis and TB, both of which can also present with cavitary lung lesions, fever & erythema nodosum: link.springer.com/article/10.100…

9/19 Moderate eosinophilia (1000-3000) tends to be associated with some tissue based protozoa (Sarcocystis), adult trematode infections (schistosomiasis) & adult nematode infections (the filariases) sciencedirect.com/science/articl…

10/19 High-grade eosinophilia (>3000) is often due to helminthic ‘syndromes’ such as tropical pulmonary eosinophilia (TPE), visceral larva migrans (VLM), Loeffler’s & eosinophilic meningitis (EM), as well as acute trematodiases & acute nematodiases (like trichinosis & filariases)

11/19 Tropical pulmonary eosinophilia (TPE) is one of the ‘pulmonary infiltrates with eosinophilia’ (PIE) syndromes & arises due to a particular immunologic response to Wuchereria bancrofti antigen. Filarial antibody titres & IgE are ⬆️⬆️ : academic.oup.com/cid/article/39…

12/19 Loeffler’s is another PIE syndrome arising from acute infection with and larval lung migration by Ascaris, Strongyloides, or hookworm (ASH). Eosinophilia can be fantastically elevated as seen here in acute pediatric strongy after a trip to 🇨🇺: cmaj.ca/content/189/46…

13/19 Acute Fascioliasis leads to high-grade eosinophilia as the worm penetrates Glisson’s capsule (++pain) & migrates through liver parenchyma leading to formation of ‘sterile abscesses’ that can appear to move over time. For more see our @jtravmed paper: academic.oup.com/jtm/article/25…

14/19 Trichinella infection - due to ingestion of undercooked meat - causes a biphasic febrile syndrome of enteritis followed by eosinophilic myositis. See paper on an outbreak of trichinosis due to bear jerky: academic.oup.com/cid/article/64… High-grade eos can damage the ❤️ incl STEMI

15/19 Loiasis may present w/ high-grade eosinophilia, Calabar swellings & frank migration of adult Loa worms across the eye. Travelers are usually amicrofilaremic vs those living in endemic areas of the central African rainforest. See atypical case here: cmaj.ca/content/187/6/…

16/19 Any migratory helminthic infection may lead to ⬆️⬆️ eosinophils. For another case of larva currens due to #strongyloides presenting with high-grade rather than the mild eosinophilia profiled above, see our paper here: researchgate.net/publication/23…

17/19 Due to the lifelong nature of #strongyloides infection until treatment (owing to autoinfective capabilities of the worm), a high-index of suspicion in travelers & low-threshold to treat is advised esp in advance of immune suppression. See guidelines: canada.ca/content/dam/ph…

18/19 Eosinophilic meningitis leading to high-grade eosinophilia is often associated with CNS infection by Angiostrongylus, Gnathostoma, or Baylisascaris. Here’s a complication of baylisascariasis - DUSN - that did not result in peripheral eosinophilia: pubmed.ncbi.nlm.nih.gov/34113738/

19/19 Thanks for staying to the end🙏For more on parasitic infections of travelers in general, see our paper on the topic:
researchgate.net/publication/26…
Happy reading!