Strongyloides hyperinfection in the immunosuppressed — recognition and management

Diagnosis: Strongyloides stercoralis hyperinfection / disseminated disease, precipitated by high-dose corticosteroids in a patient with decades-old chronic strongyloidiasis acquired in rural India. The filariform larvae in sputum and stool, the Gram-negative septicaemia and meningitis, and the temporal link to steroids are pathognomonic.^[9]

Pathophysiological basis.

• Chronic auto-infection. Strongyloides stercoralis is the only common human helminth that auto-infects — rhabditiform larvae in the bowel lumen moult to filariform forms, penetrate the perianal skin or colonic mucosa, and re-migrate through the lungs, sustaining infection for the life of the host (here, two decades after leaving an endemic region).
• Immunosuppression tipping the balance. Corticosteroids suppress the Th2 cytokine axis (IL-4, IL-5, IL-13) that holds auto-infection in check, AND directly stimulate larval moult via ecdysteroid-like receptors. The auto-infection cycle accelerates massively, producing thousands of migrating filariform larvae.
• Gram-negative translocation. The larvae carry enteric bacteria (E. coli, Klebsiella, Enterococcus, Bacteroides) on their cuticle and disrupt the bowel wall, producing Gram-negative bacteraemia, meningitis, and pneumonia — the cardinal, often confusing, clue.
• Paradoxical absence of eosinophilia is common in the immunosuppressed; do NOT be reassured by a normal eosinophil count.^[9]

Immediate management (resuscitation — the first hour).

• ABCDE + ICU. Mechanical ventilation for ARDS.
• Sepsis resuscitation. Blood cultures, broad-spectrum empiric antibiotics covering gut-origin Gram-negatives and anaerobes, intravenous fluids, and vasopressors for fluid-refractory shock.
• CSF-directed therapy. Use a regimen that covers Gram-negative meningitis given the CSF findings.
• Reduce immunosuppression where possible (taper/hold steroids if the underlying condition permits).^[9]

Definitive antiparasitic therapy (the life-saving drug).

• Ivermectin 200 micrograms/kg orally in multiple doses, duration based on disease severity and larval burden, until stool and sputum are repeatedly negative. In the intubated patient give via nasogastric tube.
• Consider adding albendazole if infection is severe (ivermectin remains first-line).
• Treat until parasitologically clear — relapse is common; repeat stool/sputum at 2-week intervals for at least 6 to 8 weeks after the course ends.^[9]

Prognosis and prevention. Case fatality is more than 60 percent. The cardinal preventive reflex — and the point the examiner is testing — is to screen every patient from an endemic region with Strongyloides serology BEFORE starting immunosuppression (corticosteroids, transplantation, biologicals, chemotherapy), and to treat positive cases with single-dose ivermectin 200 micrograms/kg before immunosuppression (multiple doses if already immunocompromised). HTLV-1 carriage is a specific additional risk and should also be screened.^[9][10]