Comparison of parasitological methods for the identification of soil-transmitted helminths, including Strongyloides stercoralis, in a regional reference laboratory in northwestern Argentina: An observational study.

Soil-transmitted helminths (STH) are a significant public health problem in impoverished communities of tropical and subtropical areas. Improved diagnostic methods are crucial for Neglected Tropical Diseases programs, particularly for S. stercoralis, as traditional methods are inadequate. Thus, it is important to identify the most accurate and efficient methods for the diagnosis of STH. We performed a retrospective study analyzing laboratory data at the Instituto de Investigaciones de Enfermedades Tropicales from 2010 to 2019. The study included data from outpatients referred for stool analysis and public health interventions from urban and rural communities in northern Salta province, Argentina. Samples were included in this analysis if processed through sedimentation/concentration, Baermann, Harada-Mori and McMaster's, with a subgroup that also included Agar plate culture method (APC). Sensitivity was calculated against a composite reference standard. Of the 5625 samples collected, 944 qualified for this analysis, with a prevalence of 11.14% for A. lumbricoides, 8.16% for hookworm, 1.38% for T. trichiura, and 6.36% for S. stercoralis. The sedimentation/concentration method was the most sensitive for A. lumbricoides (96%), compared to the McMaster method, with a sensitivity of 62%. Similarly, for hookworms, sedimentation/concentration was more sensitive than McMaster's, Harada-Mori, and Baermann with sensitivities of 87%, 70%, 43%, and 13%, respectively. Most of these infections were of light intensity. For S. stercoralis, Baermann and sedimentation/concentration methods were the most sensitive, with 70% and 62% respectively, while Harada-Mori was the least sensitive. In a subset of 389 samples also analyzed by the APC, Baermann was more sensitive than APC for detecting S. stercoralis, and both methods were superior to Harada-Mori. Parasitological methods, mostly when used combined, offer adequate opportunities for the diagnosis of STH in clinical and public health laboratories. The incorporation of S. stercoralis into the control strategies of the World Health Organization requires rethinking the current diagnostic approach used for surveys. With sedimentation/concentration and Baermann appearing as the most sensitive methods for this species. Further studies, including implementation assessments, should help in identifying the most adequate and feasible all-STH diagnostic approach.

Human Strongyloides stercoralis infection.

Strongyloides stercoralis is an important soil-transmitted helminth occurring world-wide and affecting 30-100 million people. Because many cases are asymptomatic and sensitive diagnostic methods are lacking, S. stercoralis infection is frequently underdiagnosed. The increasing incidence of autoimmune and wasting diseases and increased use of immunosuppressive agents, as well as the increased use of immunosuppressants and cytotoxic drugs, have increased S. stercoralis infection and their mortality. This review provides information about S. stercoralis epidemiology, life cycle, aetiology, pathology, comorbidities, immunology, vaccines, diagnosis, treatment, prevention, control and makes some recommendations for future prevention and control of this important parasite.

A Pilot Study for the Characterization of Bacillus spp. and Analysis of Possible B. thuringiensis/Strongyloides stercoralis Correlation.

Differentiating between Bacillus species is relevant in human medicine. Bacillus thuringiensis toxins might be effective against Strongyloides stercoralis, a nematode causing relevant human morbidity. Our first objective was to evaluate genomic and MALDI-TOF identification methods for B. thuringiensis. Our secondary objective was to evaluate a possible negative selection pressure of B. thuringiensis against S. stercoralis. PCR and Sanger were compared to MALDI-TOF on a collection of 44 B. cereus group strains. B. thuringiensis toxin genes were searched on 17 stool samples from S. stercoralis-infected and uninfected dogs. Metagenomic 16S rRNA was used for microbiome composition. The inter-rate agreement between PCR, Sanger, and MALDI-TOF was 0.631 k (p-value = 6.4 × 10-10). B. thuringiensis toxins were not found in dogs' stool. Bacteroidota and Bacillota were the major phyla in the dogs' microbiome (both represented >20% of the total bacterial community). Prevotella was underrepresented in all Strongyloides-positive dogs. However, the general composition of bacterial communities was not significantly linked with S. stercoralis infection. The genomic methods allowed accurate differentiation between B. thuringiensis and B. cereus. There was no association between B. thuringiensis and S. stercoralis infection, but further studies are needed to confirm this finding. We provide the first descriptive results about bacterial fecal composition in dogs with S. stercoralis infection.

Dermatological Presentation of Strongyloides stercoralis Infection in Two Elderly Italian Inpatients.

Persistent infections caused by Strongyloides stercoralis are probably underestimated in the elderly Italian population. This nematode is unique among helminths: it can last asymptomatically in the host for decades and may present with a broad range of clinical pictures upon reactivation. Misdiagnosis often occurs even when the clinical picture is suggestive. If undetected, this parasitosis can lead to serious consequences when hyperinfection occurs. Herein, we report two peculiar clinical cases of complicated strongyloidiasis with multiple skin lesions. The aim of our report is to lead clinicians to familiarize themselves with skin patterns and clinical features that can suggest a possible underlying strongyloidiasis.

An evaluation of a lateral flow rapid diagnostic test for Strongyloides stercoralis infection.

Strongyloides stercoralis in humans often presents as a chronic asymptomatic infection. Diagnosis can be challenging due to the limited sensitivity of faecal-based parasitological techniques. A prototype lateral flow rapid diagnostic test (RDT) for the detection of specific antibodies against Strongyloides stercoralis (SsRapid) was evaluated using 143 samples from the serum bank of the Swiss Tropical and Public Health Institute. Group 1 (n = 30) comprised serum samples from larvae-positive individuals; the RDT's diagnostic sensitivity was 97 % (29/30). Group II comprised serum samples from patients with other parasitic infections (n = 86) and Swiss blood donors (n = 27); the RDT's diagnostic specificity for this group was 90 % (102/113). The RDT showed good diagnostic performance and is a promising point-of-care test for detecting human Strongyloides stercoralis infection.

Prevalence of Strongyloides stercoralis and other helminths in four districts of Madagascar.

BACKGROUND: Estimation of prevalence of Strongyloides stercoralis infection is required in endemic areas, in order to identify areas in need of control programmes. Data on prevalence of strongyloidiasis in Madagascar are scant. Aim of this work was to estimate prevalence of S. stercoralis in four districts of Madagascar. METHODS: Fecal and serum samples collected in the context of a previous study on schistosomiasis were tested with S. stercoralis real-time PCR and serology, respectively. A multiplex real-time PCR for Ascaris lumbricoides, Ancylostoma duodenalis, Necator americanus, and Trichuris trichiura was done on fecal samples collected in the areas demonstrating higher prevalence of strongyloidiasis. Comparisons between proportions were made using Fisher exact test, with false discovery rate correction used for post-hoc comparisons. A multivariable Firth logistic regression model was used to assess potential risk factors for S. stercoralis infection. RESULTS: Overall, 1775 serum samples were tested, of which 102 of 487 (20.9%) and 104 of 296 (35.2%) were serological-positive in Marovoay and in Vatomandry districts (both coastal areas), respectively, compared to 28 of 496 (5.6%) and 30 of 496 (6.1%) in Tsiroanomandidy and in Ambositra districts (both highlands), respectively (adj. p < 0.001). PCR for S. stercoralis was positive in 15 of 210 (7.1%) and in 11 of 296 (3.7%) samples from Marovoay from Vatomandry, respectively, while was negative for all samples tested in the other two districts. High prevalence of A. lumbricoides (45.9%), hookworm (44.6%) and T. trichiura (32.1%) was found in Vatomandry. In the multivariable analysis, strongyloidiasis was associated with hookworm infection. Hookworm infection was also associated with male sex and lower education level. CONCLUSIONS: S. stercoralis prevalence proved higher in coastal areas compared to highlands. Different climatic conditions may explain this distribution, along with previous rounds of anthelminthics distributed in the country, which may have reduced the parasite load in the population. The high prevalence of the other soil-transmitted helminths (STH) in Vatomandry was unexpected, given the good coverage with benzimidazole in control campaigns. Further studies are needed to explore the risk factors for STH and S. stercoralis infections in Madagascar, in order to align with the WHO recommendations.

A silent threat behind bars: Serosurvey and associated risk factors for strongyloidiasis in female inmates and correctional officers.

Strongyloidiasis has been a neglected parasitic infection caused by Strongyloides genus parasites. Despite assessment of S. stercoralis exposure in different vulnerable populations, seroprevalence in inmates worldwide remains to be fully established. Due to poor sanitation and lack of personal hygienic practices, incarcerated individuals have been considered prone to spread infectious illnesses. Accordingly, the present study has assessed exposure and associated risk factors for strongyloidiasis in women inmates and correctional officers at the Women's State Penitentiary of Parana, part of the third largest incarceration complex in Brazil at the time. Blood samplings were performed in 2020 and 2021from a total of 503 women inmates and 92 correctional officers. Participants voluntarily responded to an epidemiological questionnaire to assess associated risk factors to strongyloidiasis. Serological analysis was performed by ELISA for anti-S. stercoralis IgG detection. Statistical analysis was performed using R software, adopting a 5% level of significance. The data were submitted to univariate analysis by chi-square or Fisher´s Exact test for assessing the association among seropositivity and the variables. The variables with p-value < 0.2 in the univariate analysis were considered fit to be included in the logistic regression. In overall, 356/503 (70.8%; 95% CI: 66.7-74.6) inmates were seropositive for anti-S. stercoralis antibodies, with no statistically associated risk factor to seropositivity. A total of 57/92 (62.0%; 95% CI: 51.8-71.2) correctional officers were seropositive, and logistic regression revealed that individuals older than 50 years were more likely seropositive. In conclusion, the high endemicity observed herein has indicated a history of previous exposure to S. stercoralis and warned for a systematic strongyloidiasis screening for inmates, to prevent long term morbidity and disseminated infection during incarceration.

Detection of Anti-Strongyloides Antibodies in the Serum of Liver Transplant Recipients: Need of Screening for This Neglected Helminthiasis.

Immunosuppressed patients, particularly transplant recipients, can develop severe strongyloidiasis. This study aimed to detect anti-Strongyloides IgG antibodies in a panel of sera from liver transplant patients. Two techniques were used: ELISA as the initial screening test and Western blotting as a confirmatory test. ELISA reactivity of 10.9% (32/294) was observed. The 40-30 kDa fraction was recognised in 93.7% (30/32) of the patients, resulting in a positivity rate of 10.2%. These data highlight the importance of serological screening for Strongyloides stercoralis infection in liver transplant recipients.

High prevalence of anti-Strongyloides antibody in SARS-CoV-2-infected human sera in a Thai hospital: Rapid serological screening.

COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), can stimulate a systemic inflammatory response with severe lung involvement, multisystem dysfunction, and death in some cases. Immunosuppressive treatments have been proposed for management of COVID-19 patients, but these bring the risk of flare-up of pre-existing infections. Strongyloidiasis can become severe or fatal in immunocompromised individuals. This cross-sectional study determined the prevalence of anti-Strongyloides IgG antibody in sera collected from SARS-CoV-2 infected persons in a tertiary-care Thai hospital from January 2021 to January 2022. The survey was conducted using a rapid immunochromatographic test (ICT) kit based on a recombinant antigen of Strongyloides stercoralis known to be IgG-immunoreactive. High prevalence of anti-Strongyloides IgG antibody was found. Out of 297 SARS-CoV-2-infected patients 117 (39.4 %, 95 % CI 33.8-45.2 %) were positive for S. stercoralis according to the ICT kit. In areas where strongyloidiasis is endemic, we suggest using this point-of-care ICT kit for routine rapid screening in seriously ill COVID-19 patients who will be subjected to immunosuppressive treatment. Prompt anthelminthic treatment should be administered to prevent serious systemic strongyloidiasis in at-risk patients.

A case of disseminated strongyloidiasis diagnosed by worms in the urinary sediment.

Strongyloidiasis is a chronic infection caused by the intestinal nematode parasite Strongyloides stercoralis and is characterized by a diverse spectrum of nonspecific clinical manifestations. This report describe a case of disseminated strongyloidiasis with urination difficulty, generalized weakness, and chronic alcoholism diagnosed through the presence of worms in the urinary sediment. A 53-year-old man was hospitalized for severe abdominal distension and urinary difficulties that started 7-10 days prior. The patient also presented with generalized weakness that had persisted for 3 years, passed loose stools without diarrhea, and complained of dyspnea. In the emergency room, approximately 7 L of urine was collected, in which several free-living female adult and rhabditiform larvae of S. stercoralis, identified through their morphological characteristics and size measurements, were detected via microscopic examination. Rhabditiform larvae of S. stercoralis were also found in the patient's stool. During hospitalization, the patient received treatment for strongyloidiasis, chronic alcoholism, peripheral neurosis, neurogenic bladder, and megaloblastic anemia, and was subsequently discharged with improved generalized conditions. Overall, this report presents a rare case of disseminated strongyloidiasis in which worms were detected in the urinary sediment of a patient with urination difficulties and generalized weakness combined with chronic alcoholism, neurogenic bladder, and megaloblastic anemia.

The generation of stable transgenic lines in the human-infective nematode Strongyloides stercoralis.

The skin-penetrating gastrointestinal parasitic nematode Strongyloides stercoralis causes strongyloidiasis, which is a neglected tropical disease that is associated with severe chronic illness and fatalities. Unlike other human-infective nematodes, S. stercoralis cycles through a single free-living generation and thus serves as a genetically tractable model organism for understanding the mechanisms that enable parasitism. Techniques such as CRISPR/Cas9-mediated mutagenesis and transgenesis are now routinely performed in S. stercoralis by introducing exogenous DNA into free-living adults and then screening their F1 progeny for transgenic or mutant larvae. However, transgenesis in S. stercoralis has been severely hindered by the inability to establish stable transgenic lines that can be propagated for multiple generations through a host; to date, studies of transgenic S. stercoralis have been limited to heterogeneous populations of transgenic F1 larvae. Here, we develop an efficient pipeline for the generation of stable transgenic lines in S. stercoralis. We also show that this approach can be used to efficiently generate stable transgenic lines in the rat-infective nematode Strongyloides ratti. The ability to generate stable transgenic lines circumvents the limitations of working with heterogeneous F1 populations, such as variable transgene expression and the inability to generate transgenics of all life stages. Our transgenesis approach will enable novel lines of inquiry into parasite biology, such as transgene-based comparisons between free-living and parasitic generations.

Introduction to Strongyloides stercoralis Anatomy.

Strongyloides stercoralis, commonly known as the human threadworm, is a skin-penetrating gastrointestinal parasitic nematode that infects hundreds of millions of people worldwide. Like other Strongyloides species, S. stercoralis is capable of cycling through a single free-living generation. Although S. stercoralis and the free-living nematode Caenorhabditis elegans are evolutionarily distant, the free-living adults of S. stercoralis are similar enough in size and morphology to C. elegans adults that techniques for generating transgenics and knockouts in C. elegans have been successfully adapted for use in S. stercoralis. High-quality genomic and transcriptomic data are also available for S. stercoralis. Thus, one can use a burgeoning array of functional genomic tools in S. stercoralis to probe questions about parasitic nematode development, physiology, and behavior. Knowledge gained from S. stercoralis will inform studies of other parasitic nematodes such as hookworms that are not yet amenable to genetic manipulation. This review describes the basic anatomy of S. stercoralis.

High-throughput sequencing of Strongyloides stercoralis - a fatal disseminated infection in a dog.

The rhabditid nematode Strongyloides stercoralis is known worldwide as the causative agent of strongyloidiasis in humans. In addition to public health concerns, S. stercoralis also infects dogs, which represent a possible reservoir for potentially zoonotic transmissions. We describe the first confirmed case of fatal disseminated infection in a dog in the Czech Republic. The microscopic and histological results were supported by a complex genotyping approach. Using high-throughput sequencing of the hypervariable region (HVR-IV) of 18S rDNA and Sanger sequencing of the partial cytochrome c oxidase subunit 1 gene (cox1), the potentially zoonotic haplotype/lineage A of S. stercoralis was confirmed, while the solely canine haplotype/lineage B was not found. The development of the disease is mainly associated with immunodeficiency, and in this case, it was triggered by inappropriate treatment, in particular the use of corticosteroids.

Successful Prompt Diagnosis of Strongyloidiasis in an Outpatient Setting at Amami Oshima Island in Japan: A Case Report.

Strongyloidiasis is a parasitic infection caused by the nematode Strongyloides stercoralis that presents with a variety of nonspecific symptoms. Diagnosis is challenging unless physicians suspect this disease and perform sensitivity tests. We report a case of strongyloidiasis with protein-losing gastroenteropathy-like symptoms in a 92-year-old Japanese female with lower extremity edema and hypoalbuminemia. In this case, the patient refused invasive tests for a complete examination; however, an agar plate culture of a stool sample was used to diagnose strongyloidiasis. The patient was treated with ivermectin during the second visit. One month later, leg edema and hypoproteinemia improved. When the cause of the symptoms is unclear, physicians should be aware of the possibility of strongyloidiasis in a person residing in a tropical or subtropical environment, where human feces are used as fertilizer and individuals frequently go barefoot in agricultural settings.

Expression of Heat Shock Protein 70 (HSP70) and Astacin Genes of Strongyloides stercoralis as well as HSP70 and HSP17.1 Genes of S. ratti in Adult and Larval Stages of S. stercoralis.

Background: Uncovering the roles and characteristics of pathogenesis-related molecules can help us develop novel management methods in parasitology. In this study, we studied the expression levels of Strongyloides stercoralis heat shock protein70 (HSP70) (Sst-hsp-70) and astacin (Sst-ast) as pathogenesis-related genes as well as the expression of S. ratti HSP70 and HSP17.1 (Sra-hsp-70, Sra-hsp-17.1) in the larvae and adult stages of S. stercoralis. Methods: A hyperinfection isolate of S. stercoralis from Gilan Province, northern Iran was cultivated on nutrient agar. After a couple of days, parasites in different stages of life were collected, and total RNA was extracted. The expression levels of astacin and HSP genes were compared by real-time PCR. Results: Statistically higher expression levels of Sst-ast, Sst-hsp-70, and Sra-hsp-70 genes in L3 larvae than in adults were observed. However, the expression level of Sra-hsp-17.1 was non-significantly lower in the larval stage than in adult worms. Conclusion: Higher expression levels of Sst-ast, Sst-hsp-70, and Sra-hsp-70 genes in the larval stages of S. stercoralis suggest the potential role of these enzymes in parasite cutaneous invasion and pathogenesis. However, higher expression of Srahsp-17.1 in adult forms is probably involved in resistance and survival mechanisms. The similarity in gene expression between S. stercoralis and S. ratti can provide helpful hints to better understand strongyloidiasis from various perspectives, including pathogenesis, proper diagnosis, and targeted treatment.

Carbon dioxide shapes parasite-host interactions in a human-infective nematode.

Skin-penetrating nematodes infect nearly one billion people worldwide. The developmentally arrested infective larvae (iL3s) seek out hosts, invade hosts via skin penetration, and resume development inside the host in a process called activation. Activated infective larvae (iL3as) traverse the host body, ending up as parasitic adults in the small intestine. Skin-penetrating nematodes respond to many chemosensory cues, but how chemosensation contributes to host seeking, intra-host development, and intra-host navigation - three crucial steps of the parasite-host interaction - remains poorly understood. Here, we investigate the role of carbon dioxide (CO2) in promoting parasite-host interactions in the human-infective threadworm Strongyloides stercoralis. We show that S. stercoralis exhibits life-stage-specific preferences for CO2: iL3s are repelled, non-infective larvae and adults are neutral, and iL3as are attracted. CO2 repulsion in iL3s may prime them for host seeking by stimulating dispersal from host feces, while CO2 attraction in iL3as may direct worms toward high-CO2 areas of the body such as the lungs and intestine. We also identify sensory neurons that detect CO2; these neurons are depolarized by CO2 in iL3s and iL3as. In addition, we demonstrate that the receptor guanylate cyclase Ss-GCY-9 is expressed specifically in CO2-sensing neurons and is required for CO2-evoked behavior. Ss-GCY-9 also promotes activation, indicating that a single receptor can mediate both behavioral and physiological responses to CO2. Our results illuminate chemosensory mechanisms that shape the interaction between parasitic nematodes and their human hosts and may aid in the design of novel anthelmintics that target the CO2-sensing pathway.

Application of Nested-qPCR-High Resolution Melting (HRM) Technology on Strongyloides stercoralis Isolates from Iran.

PURPOSE: Strongyloides stercoralis is a parasite with special characteristics presenting it as a unique nematode. Iran is an endemic area for S. stercoralis. In this study, nested-qPCR-high resolution melting (HRM) technology was applied on some human isolates of S. stercoralis from this country by focusing on evolutionary genetics analysis. METHODS: Twelve human isolates of S. stercoralis were collected from four endemic provinces of Iran. Genomic DNA was extracted from a single filariform larva for every isolate. Using specific primers targeting partial regions in cox1 gene, nested-qPCR-HRM was performed and melting-curve profiles were analyzed alongside the evaluation of genetic proximity and phylogenetic analysis using MEGA7 and DnaSP5 software. RESULTS: The melting temperature (Tm) values of the isolates were 77.9 °C-78.3 °C. All isolates from Guilan, Mazandaran, and Khouzestan Provinces shared Tm values of 78.2 °C to 78.3 °C, while the isolates from Hormozgan Province showed Tm values of 77.9 °C, 78.0 °C, and 78.1 °C. The phylogenetic tree illustrated that the sequences of the current study included nine haplotypes. Tajima's D index analyses showed that cox1 gene in S. stercoralis isolates was negative (Tajima's D = - 0.27). CONCLUSION: The isolates were divided into five temperature groups. Although HRM assay compared to PCR sequencing identified more limited genetic changes, it revealed that the mean of Tm of the isolates from Hormozgan Province was lower than those of other provinces and represented specific haplotypes for this geographical region on the phylogenetic tree.