Strongyloides stercoralis

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Background

  • Intestinal nematode; roundworm
  • Endemic in tropical/subtropical areas such as Africa, Southeast Asia, Central/South America[1]

Life Cycle

  • Present in contaminated soil → larvae penetrate skin of hosts walking barefoot → enter venous circulation, migrate to lungs, then are expectorated to pharynx and swallowed → larvae develop into females that lay eggs asexually into GI tract, which hatch into larvae and are excreted into stool
  • Larvae either become sexually reproducing males/females or filariform larvae that can reinfect host
  • Autoinfection: Unique to Strongyloides; GI larvae can migrate from GI tract to venous system, then to lungs and proceed with life cycle
    • Can lead to dramatic increase in worm burden and hyperinfection in immunocompromised

Risk factors

  • Corticosteroid use, immunosuppression
  • Transplantation
  • Hematologic neoplasm
  • Human T-lymphotropic virus-1 infection (HTLV-1)
  • Malnutrition
  • Diabetes
  • Chronic renal failure
  • Chronic alcohol use

Clinical significance

  • Chronic infection in immunosuppressed can lead to fulminant dissemination with case fatality rate as high as 70%; strong index of suspicion is needed in such cases

Clinical Features

Dermatologic

  • Larva currens: rapidly progressive pruritic linear eruption due to migration of larvae
  • Perianal pruritus
  • Foot pruritus (“ground itch”)

Respiratory

  • Dry cough
  • Wheezing
  • Loeffler’s-like syndrome: fever, shortness of breath, wheezing, pulmonary infiltrates

Immunocompromised patients

  • Respiratory and systemic symptoms such as fever will be more common[3]
  • Disseminated disease will invade multiple organ systems, including liver and brain

Differential Diagnosis

Evaluation

  • Establish possibility of infection (travel to endemic areas, etc)
  • Uncomplicated strongyloidiasis: 3 serial stool samples screened for ova and parasites, as well as ELISA for Strongyloides
    • Complicated strongyloidiasis: blood/sputum cultures, in addition to above
  • Notable eosinophilia in up to 70% of cases, though can be absent in immunosuppressed
  • Gram negative bacteremia may be present in immunocompromised

Management

Uncomplicated strongyloidiasis, normal immune system

  • Ivermectin 200 mcg/kg daily x 1-2d (drug of choice)

OR

  • Albendazole 400mg BID x 7d
  • Can consider albendazole prophylaxis in immigrants from endemic regions with consistent clinical presentation

Immunosuppressed

  • Combination therapy: albendazole 400mg BID x 7d AND ivermectin 200 mcg/kg daily x 1-2d[4]
  • Antibiotics may need to be continued until there is evidence that parasite is cleared[4]

Disposition

  • Discharge uncomplicated cases in those who are not immunosuppressed
  • Admit if immunocompromised or systemic symptoms

References

  1. Buonfrate D, Requena-Mendez A, Angheben A, Munoz J, Gobi F, Van Den Ende J, Bisoffi Z. Severe strongyloidiasis: a systematic review of case reports. BMC Infectious Diseases 2013, 13: 78. doi:10.1186/1471-2334-13-78
  2. Greaves D, Coggle S, Pollar C, Aliyu SH, Moore EM. Strongyloides stercoralis infection. BMJ 2013;347:f4610 doi: 10.1136/bmj.f4610 (Published 30 July 2013).
  3. Lim S, Katz K, Krajden S, Fuksa M, Keystone JS, Kain KC. Complicated and fatal Strongyloides infection in Canadians: risk factors, diagnosis and management. CMAJ 2004; 171 (5): 479-484.
  4. 4.0 4.1 Feely NM, Waghorn DJ, Dexter T, Gallen I, Chiodini. Strongyloides stercoralis hyperinfection: difficulties in diagnosis and treatment. Anaesthesia 2010; 65: 298-301.