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 symptoms 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
• Antibiotics 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