Abstract
BackgroundStrongyloidiasis, 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 are 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 sensitivity of the diagnostic tests used in the diagnose of S. stercoralis infection.MethodsThis cross-sectional study was performed from 2019 to 2020 among 300 high-risk patients in Khuzestan Province, southwestern Iran. Patients with autoimmune diseases, uncontrolled diabetes, HIV/AIDS, cancer, organ transplant, hematological 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. Since agar plate culture was considered the reference diagnostic test, culture-positive samples were confirmed by PCR amplification and the sequencing of the nuclear 18S rDNA (SSU) hypervariable region (HVRIV) of the parasite.ResultsThe 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 the Baermann funnel technique with the sensitivity of 75%. Direct smear examination, formalin-ether concentration technique, and Baermann funnel technique had the highest PPV (100%) while the ELISA test had the highest NPV (100%). Significant eosinophilia was observed in the patients whose culture test was positive (7/8; P < 0.05). In the present study, the majority of the positive cases by the agar plate culture had a history of prolonged exposure to soil and of asthma and COPD and were > 60 years old.ConclusionsGiven that the ELISA test had the highest NPV, the screening of all high-risk patients for S. stercoralis infection in endemic areas is recommended prior to starting corticosteroid therapy with the ELISA test. The results indicate the importance of paying attention to patients with unknown eosinophilia in endemic areas. Ivermectin should be available to strongyloidiasis patients in the endemic areas.
Highlights
Strongyloidiasis, one of the neglected tropical diseases (NTDs), can be fatal in immunocompromised patients
Patient characteristics Of the 300 patients participating in the study, 27.3% had a history of uncontrolled diabetes, 34.0% had autoimmune diseases (17.7%) or asthma and chronic obstructive pulmonary disease (COPD) (16.3%) and were receiving steroids, 26.3% had malignant diseases, and 12.4% had other diseases (AIDS, solid organ transplantation, and malnutrition)
In this study, the prevalence of S. stercoralis with the agar plate culture was lower than that using the enzyme-linked immunosorbent assay (ELISA) test but was higher compared to the formalin-ether concentration technique, Baermann funnel technique, and the direct smear examination
Summary
Strongyloidiasis, one of the neglected tropical diseases (NTDs), can be fatal in immunocompromised patients. Strongyloidiasis is a soil-transmitted helminthiasis (STH), caused mainly by the species Strongyloides stercoralis This intestinal nematode, with a prevalence of nearly 30−100 million people worldwide, is one of the neglected tropical diseases (NTD) [1, 2]. Ashiri et al Parasites Vectors (2021) 14:37 infection generally occurs in tropical and subtropical countries, in areas with warm and humid climates [3, 4]. This nematode has a complex life-cycle, the most frequent infection route is percutaneous entry of the filariform larvae [4]. Various factors, including corticosteroid drugs, human T-cell lymphotropic virus type 1 (HTLV-1) infection, malnutrition, diabetes mellitus (DM), chronic obstructive pulmonary disease (COPD) [7], transplant, and human immunodeficiency virus (HIV) infection impair immune responses and put the patient at risk for the severe strongyloidiasis [1]
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