Strongyloides Hyperinfection Syndrome

Strongyloides hyperinfection syndrome is accelerated autoinfection with Strongyloides stercoralis in immunosuppressed hosts, leading to massive larval proliferation, and disseminated strongyloidiasis when larvae spread to extraintestinal organs.

• Triggers: corticosteroids (most important), HTLV-1, haematological malignancy, solid organ or stem cell transplant, TNF inhibitors, and malnutrition; not HIV alone.
• Strongyloides persists for decades in chronic carriers (about 600 million infected worldwide) in tropical and subtropical regions, and in migrants and travellers.
• Mortality 60 to 85% when disseminated disease occurs, usually from Gram negative sepsis, meningitis, and respiratory failure.

• Prior chronic symptoms: urticaria, larva currens (rapidly migrating serpiginous skin eruption), abdominal pain, diarrhoea, and eosinophilia.
• Hyperinfection: severe abdominal pain, diarrhoea, vomiting, paralytic ileus, GI bleeding, cough, wheeze, haemoptysis, and respiratory distress.
• Dissemination: Enteric bacteraemia (E. coli, Klebsiella, Enterococcus), meningitis, pneumonia, ARDS, periumbilical "thumbprint" purpura, liver and CNS involvement.
• Eosinophilia is often absent in hyperinfection (poor prognostic sign).

• Stool, sputum, or bronchoalveolar lavage microscopy showing filariform larvae in large numbers; agar plate culture or Baermann technique; repeated stool samples increase sensitivity.
• Serology (IgG ELISA) for chronic strongyloidiasis (may be negative in immunocompromised), and PCR.
• Blood cultures and CSF analysis; chest X-ray (diffuse infiltrates).
• Screen at risk patients (travel or residence in endemic areas, eosinophilia) before steroids or immunosuppression.
• Exclude bacterial sepsis alone, tuberculosis, CMV, and other causes of ARDS.

• Ivermectin 200 micrograms/kg orally once daily until stool and sputum are negative for at least 2 weeks (typically 2 weeks or longer); if oral absorption is poor (ileus), use subcutaneous veterinary formulation or rectal ivermectin (compassionate use).
• Add albendazole 400 mg twice daily for severe disease (limited evidence).
• Broad spectrum antibiotics covering enteric Gram negative organisms and anaerobes (e.g., piperacillin tazobactam 4.5 g every 6 hours or meropenem 1 g every 8 hours; ceftriaxone plus metronidazole for meningitis).
• Reduce immunosuppression where possible (taper steroids); ICU support for sepsis and respiratory failure.
• Prevention: presumptive ivermectin 200 micrograms/kg once daily for 2 days (repeat in 2 weeks) for patients from endemic areas before immunosuppression; exclude Loa loa co-infection first in West and Central Africa.
• Follow up stool examinations and serology (falling titres) to confirm cure.