infectious diseases
Strongyloidiasis
Diagnosis of Strongyloidiasis
Identification of larvae by microscopic examination of samples, including stool or duodenal aspirate and, in patients with hyperinfection syndrome and disseminated strongyloidiasis, bronchial washings, sputum, or other body fluids Enzyme immunoassay for antibodies Microscopic examination of a single stool sample detects larvae in about 25% of uncomplicatedStrongyloidesinfections. Repeated examination of concentrated stool samples raises the sensitivity; a minimum of 3 and up to 7 stool samples is recommended. Specialized methods of stool examination increase the sensitivity. They include nutrient agar plate culture, the Baermann funnel technique, and the Harada-Mori filter paper technique. Endoscopic small bowel aspiration or biopsy of suspicious duodenal or jejunal lesions may be positive in low-level infections. In hyperinfection syndrome and disseminated strongyloidiasis, filariform larvae may be found in stool, duodenal contents, sputum, and bronchial washings and, uncommonly, in cerebrospinal fluid (CSF), urine, or pleural or ascitic fluid. They may also be seen in biopsies of lung tissue or tissue of other organs. Chest x-rays may show diffuse interstitial infiltrates, consolidation, or abscess. Several immunodiagnostic tests are available to identify anti-strongyloides antibodies in serum. Enzyme immunoassay (EIA) is recommended because of its greater sensitivity (>90%). Serum IgG antibodies can usually be detected even in immunocompromised patients with disseminated strongyloidiasis, but the absence of detectable antibodies does not exclude infection. Cross-reactions in patients with filariasis or other nematode infections may result in false-positive tests. Antibody test results cannot be used to differentiate current from past infection. A positive test warrants continuing efforts to establish a parasitologic diagnosis. Serologic monitoring may be useful in follow-up because antibody levels decrease within 6 months of successful chemotherapy. Molecular tests for the diagnosis ofS. stercoralis, including polymerase chain reaction (PCR)-based methods, are available at some reference laboratories. Sensitivity and specificity of molecular tests vary, and they have not yet replaced microscopy and serology for diagnosis. Eosinophilia is often present but can be suppressed by drugs such as corticosteroids or cytotoxic chemotherapeutic drugs. People who were possibly exposed toStrongyloidesshould be screened using stool examinations and/or serologic testing. Candidates for screening include people with a history of travel to or residence in endemic areas (recently or even in the distant past) and any of the following: Symptoms that suggest strongyloidiasis Unexplained Eosinophilia None Infected with HTLV-1 Impending organ transplant (recipient or donor) Impending treatment with corticosteroids Patients with HIV/AIDS do not appear to be at a disproportionally high risk of hyperinfection or disseminated strongyloidiasis and are not candidates for screening in the absence of other risk factors. 