Strongyloides stercoralis

Background

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

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

Diagnosis

Clinical Presentation

• Asymptomatic in up to 60% of those infected
• Nonspecific GI complaints are most common presentation
  • Weight loss, diarrhea, abdominal pain, vomiting
• Dermatologic
  • Larva currens: rapidly progressive pruritic linear eruption due to migration of larvae
  • Perianal pruritis
  • Foot pruritus (“ground itch”)
• Respiratory
  • Dry cough
  • Wheezing
  • Loeffler’s-like syndrome: fever, SOB, wheezing, pulmonary infiltrates

Immunocompromised patients

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

Differential Diagnosis

• Inflammatory bowel disease
• Schistosomiasis
• Filariasis
• Hookworm
• Toxocara canis
• Atopic dermatitis
• Asthma
• Allergic bronchopulmonary aspergillosis
• Coccidioidomycosis
• HIV
• Churg-Strauss syndrome
• Eosinophilic leukemia

Work-Up

• High index of suspicion, good travel history

Labs

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

Treatment

Uncomplicated strongyloidiasis, normal immune system

• Albendazole 400 mg BID x 7d

OR

• Ivermectin 200 mcg/kg daily x 1-2d (drug of choice)
• Can consider albendazole prophylaxis in immigrants from endemic regions with consistent clinical presentation

Immunosuppressed

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

Disposition

• Often diagnosed in outpatient setting, can discharge uncomplicated cases in those who are not immunosuppressed
• Immunocompromised patients or those with systemic symptoms will require admission

Sources

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. Feely NM, Waghorn DJ, Dexter T, Gallen I, Chiodini. Strongyloides stercoralis hyperinfection: difficulties in diagnosis and treatment. Anaesthesia 2010; 65: 298-301.
3. 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).
4. 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.
5. http://www.ncbi.nlm.nih.gov/pubmed/15635141

Authors

Kyle Brown, MD and Alex Koyfman, MD