The Strongyloides hyperinfection syndrome

Strongyloides stercoralis, is a nematode parasite widespread in the tropics. Humans are infected via skin penetration by filariform larvae from moist soil. Strongyloides larvae have an ability, almost unique among nematodes, to reinfect the same host. This autoinfection cycle enables the parasite to remain in the same host for many years, sometimes for as long as three to four decades. Long-established strongyloidiasis in a normal host is often asymptomatic. The danger occurs when a patient with non-apparent infection becomes severely immunocompromised by way of underlying disease or iatrogenic immunosuppression. This permits massive autoinfection with the development of an enormous worm burden, often complicated by secondary Gram-negative sepsis in the blood and occasionally the cerebrospinal fluid.

The diagnosis of Strongyloides hyperinfection should be suspected in any patient who has, at one time or another, visited or lived in an endemic area, has depressed immunity, and develops any of the following complications.

1. Gastrointestinal: steatorrhea, protein-losing enteropathy, ileus, necrotizing jejunitis, small bowel infarction, gastrointestinal bleeding.

2. Respiratory: shortness of breath and wheeze, respiratory failure.

3. Central nervous system: meningitis, cerebral abscess.

4. Gram-negative shock.

Risk factors for disseminated strongyloidiasis are systemic corticosteroid therapy, human T-cell lymphotropic virus I infection, HIV infection, anticancer chemotherapy, leukemia, lymphoma, lepromatous leprosy, visceral leishmaniasis, systemic lupus erythematosus, and malnutrition.

The disease is often missed and at least 50 per cent of cases are diagnosed at postmortem. The intensive care unit (ICU) staff should maintain a high index of suspicion, as it is likely that this disorder will increase in frequency over the years as more people visit tropical areas.

The diagnosis can be confirmed by finding Strongyloides larvae in stool, duodenal fluid, sputum, tracheal aspirate, ascitic fluid, or cerebrospinal fluid, depending on the sites invaded. Widespread dissemination of larvae is common. The laboratory must be asked to look specifically for parasites. Peripheral blood eosinophilia is usually absent. Serology may be helpful.

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