Screening of Strongyloides stercoralis Infection in High-Risk Patients in Khuzestan Province, Southwestern Iran

Abstract

Background: Strongyloidiasis, one of the neglected tropical diseases (NTDs), can be fatal in immunocompromised patients. Available data on Strongyloides stercoralis infection in high-risk patients in Iran; however, is limited. The aim of the present study was to determine the prevalence of S. stercoralis infection and associated risk factors among high-risk patients, as well as to evaluate the accuracy of the diagnostic tests used in the diagnose of S. stercoralis infection. Methods: This cross-sectional study was performed during 2019 to 2020 among 300 high-risk patients in Khuzestan Province, southwestern Iran. Patients with autoimmune diseases, uncontrolled diabetes, HIV/AIDS, cancer, organ transplant, hematologic malignancy, asthma and chronic obstructive pulmonary disease (COPD) were examined using direct smear examination, formalin-ether concentration, Baermann funnel technique, agar plate culture, and ELISA test. Culture-positive samples were confirmed by PCR amplification and sequencing of the nuclear 18S rDNA (SSU) hypervariable region (HVRIV) of the parasite.Results: The prevalence of S. stercoralis infection was 1%, 1.3%, 2%, 2.7%, and 8.7% using direct smear examination, formalin-ether concentration, Baermann funnel technique, agar plate culture, and ELISA test, respectively. All culture-positive samples were confirmed by SSU-PCR. According to the results, the most sensitive test was ELISA, with 100% sensitivity, followed by Baermann funnel technique with sensitivity of 75%. Direct smear examination, formalin-ether concentration technique, and Baermann funnel technique had the highest PPV (100%), while ELISA test had the highest NPV (100%). Eosinophilia significantly was observed in patients whose culture test were positive (7/8; p= 0.001). Of these, 5 patients had a history of asthma and COPD. In the present study, the majority of the positive cases by the agar plate culture had a history of prolonged exposure to soil, history of asthma and COPD, and were over the ages of 60. In two cases, S. stercoralis larva was observed 6 months and 8 months after treatment with albendazole.Conclusions: Given that the ELISA test had the highest NPV, screening of all high-risk patients for S. stercoralis infection in endemic areas is recommended prior to starting corticosteroid therapy with ELISA test. Ivermectin should be available to the strongyloidiasis patients in the endemic areas.

Modified Nonnutrient Agar Plate Culture for the Diagnosis of Strongyloides stercoralis and Hookworm Infections in La-Ngu District, Satun Province, Southern Thailand

“…However, this culture method has limitations due to the need for fresh stool. It is also cumbersome and time-consuming [8,[31][32][33]. Our study attempted to modify nonnutrient agar, which is available in local markets, to replace nutrient agar, in order to reduce costs of testing.…”