Hyperinfection

Hyperinfection refers to an accelerated, intensified autoinfection cycle of the parasite Strongyloides stercoralis, resulting in a higher larval burden within the host. It is most often seen in individuals with impaired cellular immunity, particularly those receiving systemic corticosteroids or other immunosuppressive therapies. Other risk factors include HTLV-1 infection, HIV, malignancy, malnutrition, and organ transplantation. Hyperinfection can progress to disseminated strongyloidiasis when larvae migrate beyond the usual life cycle to other organs.

Pathophysiology involves ongoing autoinfection, where autoinfective larvae produced in the gut re-enter the circulation and repeatedly seed the lungs and gastrointestinal tract. Corticosteroids are thought to promote the maturation of larvae and accelerate autoinfection, leading to a rapid increase in larval transmission and tissue invasion. This burden can cause damage to the lungs and gastrointestinal tract and may enable translocation of enteric bacteria, precipitating sepsis.

Clinical presentation commonly includes worsening GI symptoms such as abdominal pain, nausea, vomiting, and diarrhea, along with pulmonary manifestations such as cough, wheeze, dyspnea, and infiltrates on imaging. Fever and bacteremia may occur due to bacterial translocation. Eosinophilia may be absent or blunted in hyperinfection, making diagnosis more challenging. Diagnosis relies on demonstration of larvae in stool, sputum, or other body fluids, supported by serology or molecular tests in appropriate settings.

Treatment centers on prompt antihelminthic therapy, with ivermectin as the preferred agent; albendazole may be used as adjunct or alternative in some cases. Therapy is usually prolonged and tailored to clinical response, with attention to treating any concurrent bacterial infections and, if feasible, reducing immunosuppression. Prognosis is guarded, especially if dissemination occurs, but early recognition and treatment improve outcomes. Screening and preventive measures are important for high-risk patients before initiating immunosuppressive therapy.