Serodiagnosis and early detection of Strongyloides stercoralis infection

Modifications to the parasitological technique of Rugai increase the diagnostic sensitivity for strongyloidiasis

Strongyloidiasis is a neglected tropical disease caused mainly by Strongyloides stercoralis, a nematode that can persist for decades in the human host with a very low parasitic burden and without specific symptoms. Hence, it is difficult to diagnose and control. Larval concentration and culture methods with fecal samples show higher sensitivity for the diagnosis of Strongyloides-infected individuals; however, these techniques are not routinely used, primarily due to the challenges associated with processing a substantial volume of fecal samples. In the current study, we comparatively evaluated the sensitivity and applicability of modifications made to the Rugai parasitological method for the diagnosis of strongyloidiasis in fecal samples of experimentally infected rats and in 68 individuals from an urban community close to Maceió, Brazil. The presence and quantity of parasite larvae in the feces were comparatively evaluated using different parasitological techniques. In the experimental model, we demonstrated that the modified Rugai technique (RMOD) allowed for significantly higher recovery of larvae than the original Rugai technique (RO). Moreover, the sediment was cleaner and easier to evaluate using optical microscopy. Compared to other parasitological techniques, such as agar-plate culture (A-PC) and spontaneous sedimentation (SS), the RMOD technique showed higher sensitivity in the detection of larvae in all infected groups and presented comparatively better performance, especially in rats with a low parasite burden. In the human population, among the 68 stool samples evaluated, Strongyloides larvae were detected in the feces of six individuals with an estimated prevalence of 8.82%. However, the performance of each parasitological method was remarkably different. SS identified Strongyloides larvae in only two individuals and A-PC in three, whereas RMOD was able to identify six infected individuals, resulting in sensitivities of 33.3%, 50%, and 100%, respectively. In conclusion, the modifications introduced to the Rugai technique resulted in improved sensitivity for the detection of Strongyloides spp. infections, especially in stool samples with a low parasite burden, in comparison with other routinely used parasitological techniques.

Strongyloides stercoralis genotyping in a human population in southwestern Iran

BACKGROUND

Strongyloidiasis is a neglected tropical disease (NTD) that is caused mainly by Strongyloides stercoralis, with an estimated 600 million people infected worldwide, and in fewer cases by Strongyloides fuelleborni fuelleborni and Strongyloides fuelleborni kellyi. A number of studies have been conducted on the genetic diversity of S. stercoralis in East and Southeast Asia; however, there is very limited corresponding information from West Asian countries, including Iran.

METHODS

For Strongyloides worms collected from patients in southwestern Iran, the hypervariable regions I (HVR-I) and IV (HVR-IV) of the nuclear 18S ribosomal DNA (rDNA) locus (SSU) and a fragment of the subunit 1 mitochondrial cytochrome c oxidase gene (cox-1) were sequenced. For a subset of the worms, whole-genome sequencing data were generated.

RESULTS

The cox-1 sequences of 136 worms isolated from 23 patients indicated that all isolates were S. stercoralis. Among the cox-1 sequences, 33 polymorphic sites and 13 haplotypes were found. The phylogenetic analysis demonstrated that some sequences clustered fairly closely with sequences from humans and dogs from other parts of the world, while others formed a separate, Iran-specific group. Among 64 S. stercoralis analyzed, we found three of the previously described SSU HVR-I haplotypes, with haplotype II being the most frequent haplotype. In contrast to Southeast Asia, where S. stercoralis heterozygous for different haplotypes at the HVR-I locus are rare, we found 20 worms to be heterozygous for two different HVR-I haplotypes, 18 of which fell into the Iran-specific cox-1 cluster. SSU-heterozygous worms also showed elevated heterozygosity at the whole-genome level.

CONCLUSIONS

We conclude that the S. stercoralis population from the Khuzestan province shares much of the genetic diversity with the population in Southeast Asia, but there is an indication of additional genetic input. There appears to be some population structure with different subpopulations, which however do interbreed at least occasionally.

Improved diagnostic sensitivity of human strongyloidiasis using point-of-care mixed recombinant antigen-based immunochromatography

Strongyloidiasis is a neglected tropical disease that can cause fatal complications due to hyperinfection and disseminated strongyloidiasis in immunocompromised patients. We used two Strongyloides stercoralis recombinant antigenic proteins, L3NieAg.01 (NIE) and IgG-immunoreactive antigen (SsIR), to develop the recombinant antigen-based immunochromatography test (ICT) kit. We constructed and compared kits using either the NIE (NIE ICT kit) or the SsIR (SsIR ICT kit) antigens and a kit using a mixture of both (NIE-SsIR ICT kit) for detection of anti-Strongyloides IgG antibody in human serum samples. Serum samples from normal healthy individuals (Group I, n = 40), proven strongyloidiasis patients (Group II, n = 100), and those with other parasitic infections (Group III, n = 154) were evaluated. Sensitivity and specificity were 81.0% and 84.0% for the NIE ICT kit, 89.0% and 83.5% for the SsIR ICT kit, and 95.0% and 90.2% for the NIE-SsIR ICT kit, respectively. The NIE-SsIR ICT kit provided the best diagnostic results; it can supplement stool examination for clinical diagnosis and can be used to screen for asymptomatic S. stercoralis infection in people at risk in endemic areas. The NIE-SsIR ICT kit can also be used in large-scale sero-epidemiological investigations in endemic areas without the need for additional facilities or ancillary supplies.

Fatal Disseminated Strongyloidiasis in an Immunosuppressed Patient During COVID-19 Pandemic

INTRODUCTION

This report presents a fatal case of disseminated strongyloidiasis in a patient with myasthenia gravis and diabetes mellitus who had received corticosteroid therapy.

CASE REPORT

The patient was a 67-year-old woman living in a rural area endemic for Strongyloides stercoralis in northern Iran. Disseminated strongyloidiasis was diagnosed in the advanced stage of the disease, with enormous numbers of larvae demonstrated in direct smears prepared from stool samples and stomach biopsy. Despite treatment with ivermectin and antibiotics, the patient succumbed to the severity of the infection.

CONCLUSION

Clinicians working in endemic areas should be mindful of the possibility of gastric involvement in strongyloidiasis, even if symptoms are nonspecific. We recommend that high-risk individuals be screened for S. stercoralis prior to immunosuppressive therapy in endemic regions to raise awareness and prevent similar cases.

Diagnostic performance of Strongyloides-specific IgG4 detection in urine for diagnosis of human strongyloidiasis

BACKGROUND

Detection of parasite-specific IgG in urine is a sensitive method for diagnosis of strongyloidiasis and gives similar accuracy to serum IgG. However, there are no data concerning detection of IgG subclass in urine. To further explore the utility of diagnosis from urine samples, we evaluated the diagnostic performance of IgG4 in urine compared with parasitological and other immunological methods.

METHODS

The urine and sera included proven strongyloidiasis (group 1, n = 93), other parasitic infections (group 2, n = 40) and parasite negatives (group 3, n = 93). The performance of Strongyloides-specific IgG4 in urine for diagnosis of strongyloidiasis using fecal examinations as the reference standard was assessed.

RESULTS

With fecal examination as a gold standard, Strongyloides-specific IgG4 in urine had 91.4% sensitivity and 93.2% specificity while serum IgG4 had 93.6% sensitivity and 91.0% specificity. IgG4 in both urine and serum had almost perfect diagnostic agreements with fecal examination (Cohen's kappa coefficient was > 0.8). Cross-reactivity to Opisthorchis viverrini and Taenia spp. of IgG4 in urine were 7.5% and 12.5% in serum. Concurrent analyses of total IgG in urine and serum showed that the sensitivities (97.9-100%) and specificities (88.7-91.0%) were similar (P > 0.05). The sensitivity for parasitological examination by the formalin-ethyl acetate concentration technique (FECT) was 49.5% and that for agar plate culture technique (APC) it was 92.6%.

CONCLUSION

Our findings showed that specific IgG4 detection in urine yielded similar diagnostic performance to the same biomarkers in serum. This suggests that accurate diagnosis of strongyloidiasis can be performed using urine samples and IgG4 is a valid choice of diagnostic marker. Further assessment is required to assess the utility of urine IgG4 for measuring the response treatment in strongyloidiasis.

Soil-transmitted helminthic vaccines: Where are we now?

It has been tested and proven that vaccination is still the best strategy to combat infectious diseases. However, to date, there are still no vaccines against human soil-transmitted helminthic diseases, despite their high prevalence globally, particularly in developing countries and rural areas with tropical climates and poor sanitation. The development of vaccines against helminths is riddled with obstacles. Helminths have a complex life cycle, multiple stages within the same host with stage-specific antigen expression, and the ability to regulate host immune reactions to evade the immune response. These elements contribute to the main challenge of helminthic vaccines: the identification of effective vaccine candidates. Therefore, this article reviews the current progress and potential future direction of soil-transmitted helminthic vaccines, particularly against Trichuris trichiura, Ascaris lumbricoides, Strongyloides stercoralis, Necator americanus and Ancylostoma duodenale. The study design employed was a systematic review, using qualitative meta-summary synthesis. Preclinical studies and clinical trials on the development of protein subunit vaccines against the five soil-transmitted helminths were searched on PubMed and Scopus. Effectiveness was indicated by a reduction in worm burden or larval output, an increase in specific IgG levels, or an increase in cytokine production. Our findings show that only the hookworm vaccine against N. americanus is in the clinical trial phase, while the rest is still in exploratory research and pre-clinical development phase.

Seroepidemiology of Strongyloides spp. Infection in Balimo, Western Province, Papua New Guinea

Strongyloidiasis in Papua New Guinea (PNG) is poorly understood. There have been limited surveys describing the levels of endemicity in some regions of PNG, but in the Western Province, its occurrence and level of burden are unknown. This study aimed to determine the seroepidemiology of Strongyloides spp. seropositivity within a community located in the Balimo region of the Western Province. Plasma samples were collected from 120 adult participants and were subjected to anti-IgG Strongyloides spp. serological testing. Logistical regression analyses were performed to identify relationships between strongyloidiasis and attributes of sociodemography. In this cross-sectional cohort study, 22.5% (27/120; 95% CI: 15.9-30.8%) of participants were seropositive for strongyloidiasis. Participants with higher body mass indices were less likely to be seropositive for Strongyloides spp. infection (odds ratio [OR] = 0.85, P value = 0.008), and in the multivariable analysis, increasing units of age (adjusted OR [aOR] = 0.93, P value = 0.048) and participants ≤ 40 years old were associated with a decreased likelihood of Strongyloides spp. seropositivity (aOR = 0.07, P value = 0.034). The results from this study indicate that the occurrence of strongyloidiasis is high in the Western Province, PNG, and age is a determining factor of seroreactivity. This study provides evidence of endemic strongyloidiasis in this community and raises questions as to the impact of this neglected disease and other intestinal parasites on disease burden and comorbidities.

Epidemiology, clinical features, and outcomes of strongyloidiasis in Taiwan from 1988 to 2020: A case series and literature review

OBJECTIVES

We described a case of Strongyloides hyperinfection syndrome, reported a case series, and reviewed published cases of strongyloidiasis in Taiwan.

METHODS

Confirmed cases of strongyloidiasis at the National Taiwan University Hospital (NTUH) and NTUH Hsin-Chu Branch from 1988 to 2020 were identified in the medical record database. Literature search was carried out through Pubmed, Google Scholar, and Index to Taiwan Periodical Literature System to identify published cases of strongyloidiasis in Taiwan from 1979 to 2020. Data pertaining to the demographics, underlying medical conditions, clinical manifestations, laboratory findings, and outcomes were extracted.

RESULTS

A total of 117 cases of strongyloidiasis were identified, including 20 previously unpublished cases from the two hospitals and 97 published cases in the literature. Overall, 85 (73%) were male and the mean age was 64 years (range, 6-95 years). Classical symptoms such as diarrhea, cough, and skin rash were only observed in 43%, 37%, and 18% of the patients, respectively, whereas eosinophilia at presentation was only found in 48%. Strongyloides hyperinfection syndrome and disseminated strongyloidiasis were identified in 41 (35%) and 4 (3%) patients, respectively. Four (3%) patients had concurrent meningitis. In univariable analysis, being older and having pre-existing chronic obstructive pulmonary disease or asthma were associated with hyperinfection or dissemination (p = 0.024 and 0.003, respectively). The mortality rate was 43% among those with hyperinfection or disseminated infection.

CONCLUSIONS

Strongyloidiasis can cause serious complications and mortality. Efforts to diagnose strongyloidiasis early are urgently needed to improve the outcome of patients with strongyloidiasis in Taiwan.

Disseminated Strongyloidiasis Misdiagnosed as Guillain-Barré Syndrome: The Value of High-Throughput Genetic Sequencing of Pathogenic Microorganisms in Parasitic Infections

Background

With the widespread use of steroids and immunosuppressants in mainland China, disseminated strongyloidiasis is becoming a severely underestimated tropical disease due to the lack of disease-specific manifestations and well-established diagnostic methods.

Case Presentation

Here, we report a 70-year-old woman who was diagnosed with Guillain-Barré syndrome due to autonomic disturbance, symmetrical bulbar palsy, and lower-motor-nerve damage in the extremities; her symptoms continued to worsen after hormone and immunoglobulin therapy. Later, parasitic larvae were found in the patient’s gastric fluid, and metagenomic Next Generation Sequencing (mNGS) detection of bronchoalveolar-lavage fluid also found a large number of Strongyloides roundworms. The patient was diagnosed with disseminated strongyloidiasis. The patient was given albendazole for anthelmintic treatment, but died two days after being transferred to the ICU due to the excessive strongyloidiasis burden.

Conclusion

This case highlights the combined application of mNGS and traditional testing in the clinical diagnosis of difficult and critical parasitic infections in immunocompromised patients. mNGS is a new, adjunct diagnostic method to rapidly screen for possible parasitic etiologies.

The diagnosis of human and companion animal Strongyloides stercoralis infection: Challenges and solutions. A scoping review

Strongyloidiasis is the infection caused by soil-transmitted nematodes of Strongyloides species, infecting humans and some animals. Strongyloides stercoralis is the species with most clinical and epidemiological relevance in humans and dogs, due to its high prevalence and its capacity of inducing a life-threatening hyperinfection. Diagnosis of strongyloidiasis is challenging, due to the absence of a single reference standard test with high sensitivity and specificity, which also hampers the estimation of the accuracy of other diagnostic tests. In this chapter, we review the deployment and performance of the parasitological, immunological, molecular tests for the diagnosis of strongyloidiasis in humans and in dogs. Further, we comment the available evidence from genotyping studies that have addressed the zoonotic potential of S. stercoralis. Finally, we discuss the use of different diagnostic methods in relation to the purpose (i.e., screening, individual diagnosis, inclusion in a clinical trial) and the setting (endemic/non-endemic areas) and report the accuracy figures reported by systematic reviews on either parasitological, serological or molecular techniques published in literature.

A first attempt at determining the antibody-specific pattern of Platynosomum fastosum crude antigen and identification of immunoreactive proteins for immunodiagnosis of feline platynosomiasis

Background and Aim:

Feline platynosomiasis, also known as lizard poisoning, is a feline hepatic disease caused by the parasitic trematode Platynosomum fastosum. Since this helminth resides in biliary ducts and gallbladder, the heavy infection can lead to failure of the hepatobiliary system and can be associated with cholangiocarcinoma. The primary diagnostic tool currently used is conventional fecal microscopy. However, low sensitivity of detection could occur in the case of light infection or biliary obstruction. This study aimed to determine the antibody-specific pattern of P. fastosum crude antigen and to identify immunoreactive proteins to develop the immunodiagnostic techniques.

Materials and Methods:

We investigated potential antigens specific to P. fastosum infection using western blotting. Forty-six samples of cat serum, including 16 P. fastosum-infected sera, eight healthy control sera, and 22 sera infected with other endoparasites were used. The sensitivity, specificity, positive predictive value, and negative predictive value of each band were calculated. Immunoreactive bands with high diagnostic values were further analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) to identify the protein components.

Results:

Using immunoblotting, three proteins of 72 kDa, 53 kDa, and 13 kDa were found to be immunogenic. LC-MS/MS identified these proteins as a 70 kDa heat shock protein, a hypothetical protein (CRM22_002083) (adenosine triphosphate synthase subunit beta), and histone H2B, respectively.

Conclusion:

This study is the first to reveal three proteins that could be candidates for developing diagnostic tools for feline platynosomiasis.

Comparison of Two Serological Assays in Detecting Strongyloides Infection in Immunocompromised Patients

Strongyloides infection may develop into fatal hyperinfection and dissemination syndrome in immunocompromised hosts. Despite suboptimal specificity issues, the detection of IgG antibodies by ELISA has been central in the serodiagnosis of Strongyloides infection. Recently, an IgG4-based lateral-flow test (SsRapid) using recombinant NIE (rNIE) protein with good diagnostic performance has been reported. This study assessed the result concordance between a commercial IgG-ELISA and the SsRapid. Additionally, we determined the Strongyloides seroprevalence and its association with clinical manifestations. Immunocompromised patients (N = 200) were from Hospital Canselor Tuanku Muhriz, Kuala Lumpur, Malaysia, and were diagnosed with HIV/AIDS, hematological malignancy, and solid organ cancers. Their plasma samples were tested using a commercial IgG-ELISA and SsRapid. A fair concordance (κ = 0.27-0.33; P < 0.05) among the tests was demonstrated. The SsRapid exhibited a significantly higher (P < 0.05) seroprevalence (10.5% [21/200]) compared with IgG-ELISA (7.5% [15/200]). After adsorption with rNIE, all SsRapid-positive samples tested negative with the rapid test, thus showing binding specificity. There was no significant association with clinical manifestations. This study revealed that SsRapid is a useful diagnostic tool for Strongyloides infection, and there is a notable seroprevalence among the immunocompromised patients.

Using newly optimized genetic tools to probe Strongyloides sensory behaviors

The oft-neglected human-parasitic threadworm, Strongyloides stercoralis, infects roughly eight percent of the global population, placing disproportionate medical and economic burden upon marginalized communities. While current chemotherapies treat strongyloidiasis, disease recrudescence and the looming threat of anthelminthic resistance necessitate novel strategies for nematode control. Throughout its life cycle, S. stercoralis relies upon sensory cues to aid in environmental navigation and coordinate developmental progression. Odorants, tastants, gases, and temperature have been shown to shape parasite behaviors that drive host seeking and infectivity; however, many of these sensory behaviors remain poorly understood, and their underlying molecular and neural mechanisms are largely uncharacterized. Disruption of sensory circuits essential to parasitism presents a promising strategy for future interventions. In this review, we describe our current understanding of sensory behaviors - namely olfactory, gustatory, gas sensing, and thermosensory behaviors - in Strongyloides spp. We also highlight the ever-growing cache of genetic tools optimized for use in Strongyloides that have facilitated these findings, including transgenesis, CRISPR/Cas9-mediated mutagenesis, RNAi, chemogenetic neuronal silencing, and the use of fluorescent biosensors to measure neuronal activity. Bolstered by these tools, we are poised to enter an era of rapid discovery in Strongyloides sensory neurobiology, which has the potential to shape pioneering advances in the prevention and treatment of strongyloidiasis.

Association of Strongyloides stercoralis infection and type 2 diabetes mellitus in northeastern Thailand: Impact on diabetic complication-related renal biochemical parameters

BACKGROUND

Several studies have demonstrated that helminth infections provide a degree of protection against Type 2 diabetes mellitus (T2DM). However, the relationship between Strongyloides stercoralis infection and T2DM has scarcely been investigated and the protective effect of infection against development of diabetic complications is unclear. In this study, we aimed to investigate the relationship between S. stercoralis infection and T2DM in a rural area of Khon Kaen Province, Thailand. The impact of S. stercoralis infection on diabetic complication-related kidney function biochemical parameters and body-mass index (BMI) was also assessed.

METHODOLOGY

Using a cross-sectional study design, S. stercoralis infection and T2DM assessments were conducted between October 2020 and May 2021. Associations between S. stercoralis infection, T2DM, and socioeconomic factors were analyzed using multivariable logistic regression analyses. Diabetic complication-related biochemical parameters relating largely to kidney function (estimated glomerular filtration rate (eGFR), urine albumin-to-creatinine ratio (UACR), serum creatinine, uric acid, alanine transaminase (ALT), and low-density lipoprotein cholesterol (LDL-C)) and BMI of participants with and without T2DM were compared between groups with or without S. stercoralis infection.

RESULTS

One hundred and seven out of 704 individuals (15.20%) were positive for S. stercoralis, and 283 people were diagnosed with T2DM. Of those with T2DM, 11.31% (32/283) were infected with S. stercoralis and of those without T2DM, 17.82% (75/421) were infected with S. stercoralis. Multivariate analysis revealed that T2DM was inversely correlated with S. stercoralis infection (Adjusted OR  =  0.49; 95% CI: 0.30, 0.78; p  = 0.003), while male, increasing age, lower education level, and alcohol intake were positively associated with infection. Those infected with S. stercoralis had lower eGFR levels and higher ALT and UACR levels than those in the uninfected group.

CONCLUSION

This finding indicates that S. stercoralis infection was inversely associated with T2DM in northeastern Thailand, but participants infected with S. stercoralis had lower eGFR levels and higher ALT and UACR levels. Infection with S. stercoralis might lead to worse complication-related renal biochemical parameters.

The accuracy of a recombinant antigen immunochromatographic test for the detection of Strongyloides stercoralis infection in migrants from sub-Saharan Africa

Background

Strongyloidiasis, a nematode infection which is mainly caused by Strongyloides stercoralis in humans, can lead to a fatal syndrome in immunocompromised individuals. Its diagnosis is challenging due to the absence of a diagnostic gold standard. The infection is highly prevalent in migrants from endemic countries in tropical and subtropical areas, and a rapid diagnostic test would be helpful for screening purposes. The aim of this study was to estimate the accuracy of a novel immunochromatographic test (ICT) for the diagnosis of S. stercoralis infection.

Methods

A single-centre diagnostic accuracy study was undertaken using well-characterized frozen sera available from the biobank of a referral hospital for parasitic diseases in Italy. The included sera were from migrants from sub-Saharan Africa, and matching results were available for agar plate culture and/or polymerase chain reaction for S. stercoralis; moreover, the results of both a commercial enzyme-linked immunosorbent assay test and an in-house immunofluorescence test for strongyloidiasis were made available. Laboratory staff who read the ICT results were blinded as regards the results of the other tests. Two readers independently read the ICT, and a third one was involved when results were discrepant. The accuracy of the ICT was assessed both against the results of the panel of faecal tests and by latent class analysis (LCA).

Results

Agreement between the readers was excellent [Cohen’s κ = 92.7%, 95% confidence interval (CI) 88.3–97.1%]. When assessed against the results of the faecal tests, the sensitivity and specificity of the ICT were 82.4% (95% CI 75.7–89.0%) and 73.8% (95% CI 66.8–80.9%), respectively. According to the LCA, the sensitivity and specificity were 86.3% (95% CI 80.1–92.5%) and 73.9% (95% CI 67.0–80.8%), respectively.

Conclusions

The results of the ICT demonstrated ease of interpretation. The accuracy proved good, though the sensitivity might be further improved for screening purposes.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05249-z.

Strongyloidiasis in a Patient Diagnosed by Metagenomic Next-Generation Sequencing: A Case Report

Background

Strongylodiasis may be asymptomatic or cause mild gastrointestinal symptoms, and may be a fatal disseminated disease or Strongyloides hyperinfection syndrome. Non-specific clinical manifestations, such as pneumonia and gastroenteritis, pose a diagnostic dilemma.

Case Presentation

We report a case of a 67-year-old Chinese male who presented with abdominal pain, fever, headache, vomiting, constipation, and slight cough with sputum for nearly 2 months. He had been in good health and had no history of glucocorticoid use. He was diagnosed with enterococcal meningitis and intestinal obstruction at a local hospital and improved after treatment with vancomycin, but symptoms of headache and abdominal pain soon recurred. The metagenomic next-generation sequencing (mNGS) of the cerebrospinal fluid using Illumina X10 sequencer revealed seven sequence reads matching Strongyloides stercoralis. Strongyloidiasis was suspected. Microscopic examination of gastric fluid revealed the presence of S. stercoralis larvae, which was confirmed by PCR to amplify both S. stercoralis ribosomal DNA gene and mitochondrial cytochrome c oxidase subunit 1 gene and sequencing amplicons. Strongyloidiasis was diagnosed. Albendazole (400 mg, twice daily) was used, and the patient recovered gradually.

Conclusion

mNGS may be a useful tool for detecting uncommon infectious disease. The case would help clinicians to raise awareness of strongyloidiasis in non-endemic areas and reduce fatality.

The Association between Diabetes and Human T-Cell Leukaemia Virus Type-1 (HTLV-1) with Strongyloides stercoralis: Results of a Community-Based, Cross-Sectional Survey in Central Australia

In central Australia, an area that is endemic for the human T-cell leukaemia virus type-1 (HTLV-1), the prevalence of Strongyloides stercoralis and its association with other health conditions are unknown. A cross-sectional community-based survey was conducted in seven remote Aboriginal communities in central Australia, from 2014 to 2018. All residents aged ≥10 years were invited to complete a health survey and to provide blood for Strongyloides serology, HTLV-1 serology and HTLV-1 proviral load (PVL). Risk factors for Strongyloides seropositivity and associations with specific health conditions including diabetes and HTLV-1 were determined using logistic regression. Overall Strongyloides seroprevalence was 27% (156/576) (children, 22% (9/40); adults (≥15 years), 27% (147/536), varied widely between communities (5–42%) and was not associated with an increased risk of gastrointestinal, respiratory or dermatological symptoms. Increasing age, lower HTLV-1 PVL (<1000 copies per 105 peripheral blood leucocytes) compared to the HTLV-1 uninfected group and community of residence were significant risk factors for Strongyloides seropositivity in an adjusted model. A modest reduction in the odds of diabetes among Strongyloides seropositive participants was found (aOR 0.58, 95% CI 0.35, 1.00; p = 0.049); however, this was lost when body mass index was included in the adjusted model (aOR 0.48, 95% CI 0.48, 1.47; p = 0.542). Strongyloides seropositivity had no relationship with anaemia. Exploring social and environmental practices in communities with low Strongyloides seroprevalence may provide useful lessons for similar settings.

A point-of-care cassette test for detection of Strongyloides stercoralis

Strongyloides stercoralis is a parasite that causes strongyloidiasis worldwide. It may lead to a life-long infection in immunocompetent people and hyperinfection in immunosuppressed patients. A point-of-care (POC) rapid test is helpful for patient diagnosis in resource-limited settings and as a detection tool in elimination/control programs. Previously, we reported a rapid IgG4 dipstick test (Ss Rapid®) for Strongyloides suitable for a laboratory setting. A POC cassette format of the test, which is field-applicable, has since been developed. Here, we report on a laboratory-based evaluation of the Ss Rapid® cas sette test on 285 sera. We assessed the diagnostic sensitivity of the Ss Rapid® cas sette with 32 sera, comprising samples from larval and/or DNA positive individuals from three countries. Additionally, we also tested samples from 33 seropositive endemic areas residents. We evaluated the diagnostic specificity of the test using 220 samples, comprising sera from other infections (n = 101), allergy cases with high IgE antibodies (n = 4), and blood donors (n = 115). The test showed high diagnostic sensitivity (97%, 31/32), and all sera of the seropositive endemic residents were reactive. It also showed high diagnostic specificity (94.5%, 208/220), and all false-positive samples tested negative after sera adsorption using recombinant NIE-coated microsphere beads. Additionally, we showed that the test worked with spiked whole blood samples. The study results showed that the SsRapid® cas sette test merits further laboratory and field evaluations.

Atypical pulmonary presentation of Strongyloides stercoralis hyperinfection in a patient with philadelphia chromosome-positive acute lymphoblastic leukemia: Case report

Strongyloides stercoralis is a soil-transmitted helminth endemic to tropical and subtropical regions and can be acquired due to parasite penetration through the skin. It can remain dormant in the gastrointestinal system for decades after the primary infection. In immunocompromised patients, this parasite can cause autoinfection with progression to hyperinfection syndrome. Here we report a unique case of pulmonary strongyloidiasis in a 32-year-old female, originally from Guatemala, with a significant clinical history of Philadelphia chromosome-positive B-cell acute lymphoblastic leukemia diagnosed in 2019. The patient is status post chemotherapy with tyrosine kinase inhibitor plus hyper-CVAD regimen (Cyclophosphamide, Vincristine sulfate, Doxorubicin hydrochloride (Adriamycin), and Dexamethasone). History of drug-induced hyperglycemia and obesity was also noted. Her current chief complaint included dyspnea, tachycardia, and chest pain. Chest computerized tomography (CT) scan showed diffuse interstitial pulmonary edema with septal thickening, scattered ground-glass opacities, and small pericardial effusion. Due to normal ejection fraction, the differential diagnosis included non-cardiogenic pulmonary edema, pneumonitis secondary to chemotoxicity, and infection. She rapidly progressed to acute hypoxic respiratory failure, and a bronchoalveolar lavage study revealed numerous larvae consistent with Strongyloides hyperinfection. Further workup revealed eosinophilia with negative Strongyloides IgG antibody. Given the rarity of this infection in the United States and the patient's place of birth, acquired latent Strongyloides infection is favored as the initial source of infection. The reactivation of the infection process was most likely secondary to her chemotherapy treatment. Strongyloides hyperinfection diagnosis can be challenging to establish and entails a high level of suspicion. Cytology evaluation is an essential factor for diagnosis.

Diagnosis of human strongyloidiasis: Application in clinical practice

This review considers the advantages and disadvantages of parasitological techniques, methods of detecting antibodies and antigens, as well as molecular biology techniques in the diagnosis of human strongyloidiasis. In addition, it elucidates the potential of different techniques for rapid and effective detection of clinical cases, thus enabling early treatment and preventing fatal consequences of this helminthiasis.

Concentration of urine samples improves sensitivity in detection of Strongyloides-specific IgG antibody in urine for diagnosis of strongyloidiasis

Detection of IgG in urine is an efficient method comparable to that in serum for diagnosis of strongyloidiasis but effects of daily variation in urine dilution on diagnostic accuracy is not clearly known. This study evaluated effects of urine concentration on detection of parasite-specific IgG by urine enzyme-linked immunosorbent assay (ELISA), particularly in individuals with border-line results or false-negative diagnosis. Optimal concentration conditions were established by comparing Strongyloides-specific IgG antibody levels between unconcentrated and concentrated urine in participants with different infection intensities, namely healthy control (HC), low-negative (LN), high-negative (HN) and low-positive (LP) groups. The optimal condition was selected and validated in a field-trial study. The final urine concentration protocol required centrifugation at 4,000 g at 4°C for 10 mins using the Amicon® concentrator tube. This protocol was validated in groups of participants with varying diagnoses according to urine ELISA and fecal examination (n=148). The concentrated-urine ELISA increased the proportion of positive results in the LN group by 68.2% and by 100% in the HN group. Significantly elevated IgG antibody levels were seen in the LP group. In the group that was false negative by urine ELISA but positive by fecal examination (n=28), concentrated-urine ELISA yielded 100% positive results. Overall, the frequency estimates of S. stercoralis were 23.6% by fecal culture, 27% by standard urine ELISA and 90.5% by concentrated-urine ELISA. Concentration of urine samples prior to analysis by ELISA improved the sensitivity for diagnosis and is potentially useful in diagnosis of strongyloidiasis in immunocompromised individuals or in low-prevalence areas.

Diagnostic Techniques for Soil-Transmitted Helminths - Recent Advances

Soil-transmitted helminth (STH) infections (hookworms, Trichuris, Ascaris) and Strongyloides spp. are associated with a substantial global burden and high morbidity. Sensitive and specific methods for diagnosis of these infections are essential for mapping the burden in communities, accurate assessment of infection levels, to guide interventions and monitoring the success of STH control programs. Despite considerable progress to control STH over several decades, we are still far from identifying a fully adequate diagnostic test. Conventional microscopy-based methods such as direct Kato–Katz smear or mounts after stool centrifugation/flotation-based concentration techniques have been the mainstay of diagnosis, especially in resource-poor countries where these infections abound. However, recently, these are being adapted to closed, easy to perform, digital formats, thereby improving the sensitivity as well as applicability in a remote, resource-limited setting. The use of image analysis systems to identify and quantify helminth eggs, with potential adaptation to smartphones, is also promising. Antibody detection tests have a limited role mostly in the case of Strongyloides hyperinfection. Coproantigen detection tests have been developed and used in veterinary practice for detection of STH, but these have not been evaluated for use in humans. More sensitive molecular diagnostics, including assays developed with new bioinformatic tools and techniques such as polymerase chain reaction (PCR), quantitative PCR (qPCR) and loop-mediated amplification assay, can help in the clear and precise assessment of STH burden during elimination phase and are of immense value for diagnosis in areas with low endemicity and in travelers to endemic regions. Moreover, the molecular techniques will help detect new species that may emerge. Sample preservation and efficient DNA extraction are critical and significantly affect the efficiency of molecular diagnostic tests. In addition to the diagnosis of clinical or asymptomatic infection in humans, detection of STH eggs in environmental samples is imperative to boost STH control efforts. Overall the diagnostic performance, cost-effectiveness, ease of performance, rapidity and in-field applicability of any test should be considered when choosing from the various diagnostic assays in areas with different endemicity, in addition to striving towards the development of novel technologies and optimization of existing methods.

Parasitic Infections of the Gastrointestinal Track and Liver

Parasites have coevolved with humans. Several of them colonize the human body and establish a symbiotic relationship. Other parasites cause severe and lethal diseases. Prevalence of parasitic infections is decreased in highly industrialized countries, largely due to enforced hygienic practices. In contrast, parasites cause significant morbidity and mortality in parts of the world with barriers to effective public hygiene. Some parasites have emerged as potent pathogens in specific patient populations, such as immune suppressed individuals, regardless of sanitation. This article reviews common parasites encountered in clinical practice and, in the setting of host-parasite symbiosis, discusses their immune regulatory role.

Development of Immunochromatographic Test Kit for Rapid Detection of Specific IgG4 Antibody in Whole-Blood Samples for Diagnosis of Human Gnathostomiasis

Human gnathostomiasis is a harmful food-borne zoonosis caused by roundworms of the genus Gnathostoma. The parasite can occasionally migrate to the central nervous system, causing life-threatening disease and death. Here, we report a new point-of-care (POC) test kit, the gnathostomiasis blood immunochromatographic test (GB-ICT) kit. The kit is based on recombinant Gnathostoma spinigerum antigen and detects specific IgG4 antibody in whole-blood samples (WBSs). The GB-ICT kit showed potentially high diagnostic values with simulated WBSs (n = 248), which were obtained by spiking patients’ sera with red blood cells. The accuracy, sensitivity, specificity, and positive and negative predictive values were 95.2%, 100%, 93.8%, 81.5%, and 100%, respectively. Ten WBSs from clinically suspected gnathostomiasis patients were all positive according to the GB-ICT kit, while 10 WBSs from healthy volunteers were negative. The GB-ICT kit is a simple and convenient POC testing tool using finger-prick blood samples: venous blood sampling and serum separation processes are not required. The GB-ICT kit can support clinical diagnosis in remote areas and field settings without sophisticated equipment facilities.

Development of rSs-NIE-1 and rSs-IR Recombinant Antigen-Based Immunoblot for Detection of Antibody to Strongyloides stercoralis

Strongyloides stercoralis is a soil-transmitted nematode that can cause life-threatening conditions in immunocompromised persons. In the United States, strongyloidiasis should be considered mainly in immigrants, refugees, or travelers. The confirmatory laboratory diagnosis is usually performed by detecting larvae from the stool, duodenal material, and sputum. In persons who are immunocompromised with severe strongyloidiasis, adult worms and eggs can be detected from duodenal material. For serological diagnosis, most assays use crude antigens to detect anti-S. stercoralis IgG. Recently, recombinant proteins such as rSs-NIE-1 and rSs-IR have been used to detect IgG antibodies. We used rSs-NIE-1 and rSs-IR recombinant antigens to develop a biplex Western blot assay to detect the IgG4 antibody in individuals with strongyloidiasis. The sensitivities of rSs-NIE-1 and rSs-IR were 97.4% and 90.8%, respectively, whereas the specificities were 97.6% and 98%, respectively. In conclusion, the biplex rSs-NIE-1 and rSs-IR immunoblot performs well in detecting IgG4 antibody in S. stercoralis-infected persons.

Strongyloidiasis Serological Analysis with Three Different Biological Probes and Their Electrochemical Responses in a Screen-Printed Gold Electrode

(1) Background: The validation of biological antigens is the study's utmost goal in biomedical applications. We evaluated three different probes with single and multiple epitopes through electrochemical detection of specific IgG in serum for human strongyloidiasis diagnosis. (2) Methods: Screen-printed gold electrodes were used and probes consisting of two single-epitope synthetic peptides (D3 and C10) with different sequences, and a multi-epitope antigen [detergent phase (DP)-hydrophobic membrane proteins]. Human serum samples from three populations were used: Strongyloides stercoralis positive, positive for other parasitic infections and negative controls. To test the immobilization of probes onto a screen-printed gold electrode and the serum IgG detection, electrochemical analyses were carried out through differential pulse voltammetry (DPV) and the electrode surface analyses were recorded using atomic force microscopy. (3) Results: The electrochemical response in screen-printed gold electrodes of peptides D3 and C10 when using positive serum was significantly higher than that when using the DP. Our sensor improved sensitivity to detect strongyloidiasis. (4) Conclusions: Probes' sequences are critical factors for differential electrochemical responses, and the D3 peptide presented the best electrochemical performance for strongyloidiasis detection, and may efficiently substitute whole antigen extracts from parasites for strongyloidiasis diagnosis in electrochemical immunosensors.

Innovative approaches to improve serodiagnosis of Strongyloides stercoralis infection

Strongyloidiasis is a helminthiasis of neglected condition that has no gold standard parasitological diagnosis due to the intermittent release of larvae in feces. This study aimed to use an scFv (single chain variable fragment) obtained by Phage Display, previously validated to detect immune complexes in serum samples from individuals infected with Strongyloides stercoralis by enzyme-linked immunosorbent assay (ELISA). Now the ability of scFv to detect the immune complexes was verified by immunofluorescence, flow cytometry using magnetic beads and surface plasmon resonance (SPR). As ELISA, the SPR, immunofluorescence and flow cytometry demonstrated the ability of scFv to detect immune complexes in sera from individuals with strongyloidiasis and discriminate them from sera of individuals with other parasitic diseases and healthy individuals. Besides de conventional ELISA, the novel approaches can also be promptly applied as auxiliary diagnostic tools to the existing parasitological method for accurate diagnosis of human strongyloidiasis.

Screening of Strongyloides stercoralis infection in high-risk patients in Khuzestan Province, Southwestern Iran

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 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.

METHODS

This 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.

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 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.

CONCLUSIONS

Given 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.

Diagnostic Potential of an IgE-ELISA in Detecting Strongyloidiasis

Strongyloides stercoralis infection is prevalent worldwide and can cause lifelong infection in immunocompetent individuals, and potentially death in immunosuppressed patients. The diagnosis is hindered by the low sensitivity of microscopic examination, thus making serology an important complementary test to improve the detection rate. However, there were reports that some Strongyloides-infected individuals were negative with specific IgG and IgG4 assays, and other helminth infections were positive with commercial Strongyloides IgG-ELISAs. Thus, there is a need to develop better serodiagnostic methods for strongyloidiasis. We investigated the diagnostic potential of IgE-ELISAs using Strongyloides larval lysate. Sera from two groups infected with Strongyloides served as the positive reference, that is, 1) positive by commercial IgG-ELISAs and IgG4 rapid test, and stool samples positive by microscopy and/or PCR (group IA; n = 20); and 2) negative by IgG-ELISAs and IgG4 rapid test, but stool samples were PCR positive (group IB sera; n = 11). Sera from another two groups served as negative reference (controls), that is, 1) infected with other parasites (group II; n = 73) and 2) healthy donors (group III; n = 22). Results showed a 100% diagnostic sensitivity in detecting sera from groups IA and IB. The latter group of individuals probably had early infection because their IgG and IgG4 assays were negative. The optical density values of group IB sera were also significantly lower than those of group IA (P < 0.003). The IgE-ELISA was 100% specific when tested against sera from groups II and III. This study highlights the diagnostic potential of IgE-ELISA using larval lysate to detect strongyloidiasis, especially those with probable early infection.

Multi-Laboratory Evaluation of a Lateral Flow Rapid Test for Detection of Amebic Liver Abscess

Independent evaluations of XEh Rapid^®, an IgG4-based rapid dipstick test, were performed to assess its diagnostic performance to detect amebic liver abscess (ALA) using 405 samples at seven laboratories in four countries. The test showed high diagnostic specificity (97-100%) when tested with samples from healthy individuals (n = 100) and patients with other diseases (n = 151). The diagnostic sensitivity was tested with a total of 154 samples, and the results were variable. It was high in three laboratories (89-94%), and moderate (72%) and low (38%) in two other laboratories. Challenges and issues faced in the evaluation process are discussed. Nevertheless, XEh Rapid is promising to be developed into a point-of-care test in particular for resource-limited settings, and thus merits further confirmation of its diagnostic sensitivity.

Strongyloides stercoralis Gastric Ulcer: A Rare Cause of Upper Gastrointestinal Bleeding

Strongyloidiasis is an infection caused by Strongyloides stercoralis. Gastrointestinal manifestations typically include duodenitis, chronic enterocolitis, and malabsorption, while gastric involvement is very rare. In this case report, the -authors present a case of upper gastrointestinal bleeding caused by a gastric ulcer with a challenging etiological diagnosis. In Portugal, there have been reports in the past century of autochthonous cases of S. stercoralis infection suggesting endemic zones, but with the current sanitation infrastructure strongyloidiasis is thought to be rare. A 56-year-old Caucasian male smoker with a history of significant weight loss presented to the emergency department with hema-temesis and abdominal pain. Upper endoscopy revealed a giant gastric ulcer with a macroscopic appearance suggestive of malignancy. Further investigation with CT scan highlighted gastric wall thickness and a spiculated lung lesion in the upper right lobe without lymph node involvement or metastatic disease. Bronchoscopy with bronchial brushing was performed. Histological examination identified squamous cell carcinoma of the lung and the patient was referred to Oncological Pneumology. Gastric ulcer biopsies ruled out malignancy and identified fragments of nematodes with inflammatory infiltrates and fibrinogranulocytic exudate, suggestive of S. stercoralis. Accordingly, the diagnosis of strongyloidiasis was made and further confirmed with molecular methods and serology. The giant gastric ulcer was affirmed to be caused by S. stercoralis infection and the patient was treated with ivermectin with improvement of epigastric pain. On reevaluation 6 weeks later the patient was asymptomatic, had gained weight, parasitological stool examinations were negative, and upper endoscopy showed complete ulcer healing. Further tests were done targeting risk factors for strongyloidiasis, and in addition to the presence of malignancy, other underlying causes for immunosuppression were ruled out. In this case report strongyloidiasis was manifested by gastric involvement with upper gastrointestinal bleeding in a patient who was subsequently diagnosed with squamous cell carcinoma of the lung.

Effectiveness of Strongyloides Recombinant IgG Immunoreactive Antigen in Detecting IgG and IgG4 Subclass Antibodies for Diagnosis of Human Strongyloidiasis Using Rapid Immunochromatographic Tests

Human strongyloidiasis is an important soil-transmitted helminthiasis that affects millions worldwide and can develop into fatal systemic strongyloidiasis in immunosuppressed patients. We have developed two new rapid and simple-to-use immunochromatographic test (ICT) kits for rapid serodiagnosis that support stool examination for clinical diagnosis. Strongyloides stercoralis recombinant IgG immunoreactive antigen (GenBank: AAB97359.1; rSsIR-based ICT kit) was used for detection of IgG and IgG4 antibodies. The diagnostic efficacy of both kits was evaluated using human serum samples from strongyloidiasis patients, healthy individuals, and those with other parasitosis. At a prevalence of infection of 36.4%, the diagnostic sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the rSsIR-based IgG ICT kit were 91.7%, 83.8%, 76.4%, 94.6%, and 86.7%, respectively, and those of the rSsIR-based IgG4 ICT kit were 78.3%, 84.8%, 74.6%, 87.3%, and 82.4% respectively. The concordance between the two kits was 89.7%. The recombinant antigen can be produced to an unlimited extent and the kits can be used as point-of-care diagnostic tools and in large-scale surveys in endemic areas throughout tropical regions without necessitating additional facilities or ancillary supplies.

Strongyloides hyperinfection in an HIV-positive kidney transplant recipient: a case report

BACKGROUND

Strongyloidiasis is caused by the helminth Strongyloides stercoralis and is well-recognised amongst transplant recipients. Serious complications, including Strongyloides hyperinfection which is a syndrome of accelerated autoinfection, or disseminated disease, can occur post-transplantation, resulting in significant morbidity and mortality. Here we present the first published case we are aware of, describing post-transplant Strongyloides hyperinfection in an HIV-positive kidney transplant patient. We discuss the diagnostic challenges and the role of pre-transplant screening.

CASE PRESENTATION

A 58-year-old African-American male, originally from the Caribbean, received a deceased donor kidney transplant for presumed focal segmental glomerulosclerosis. He was known to be HIV-positive, with a stable CD4 count, and an undetectable viral load. Five months post-transplant, he developed gastrointestinal symptoms and weight loss. He had a normal eosinophil count (0.1-0.2 × 109/L), negative serum cytomegalovirus DNA, and negative blood and stool cultures. His Strongyloides serology remained negative throughout. A diagnosis of Strongyloides hyperinfection was made by the histological examination of his duodenum and lung, which identified the parasites. He completed his course of treatment with Ivermectin but exhibited profound deconditioning and required a period of total parenteral nutrition. He was subsequently discharged after a prolonged hospital admission of 54 days.

CONCLUSIONS

This case highlights the challenges in diagnosing Strongyloides infection and the need to maintain a high index of clinical suspicion. Non-invasive techniques for the diagnosis of Strongyloides may be insufficient. Routine pre-transplant serological strongyloidiasis screening is now performed at our centre.

Strongyloides stercoralis in Alcoholic Patients: Implications of Alcohol Intake in the Frequency of Infection and Parasite Load

Strongyloides stercoralis infection in immunocompromised subjects, including chronic alcoholics, can lead to a severe disease. Moreover, its prevalence in alcoholic patients seems to be higher than that in the general population. The aims of this study were to evaluate the frequency of S. stercoralis infection in alcoholic patients and to investigate the influence of alcohol intake on the parasite load, as well as to evaluate the sensitivity of three different parasitological methods according to the larval output. Fecal samples of 1290 chronic alcoholic patients were examined by spontaneous sedimentation, Baermann-Moraes, and agar plate culture (APC) methods. S. stercoralis was the most frequent parasite found (14.5%; n = 187). Alcoholic individuals infected with Strongyloides stercoralis had a higher daily consumption of alcohol than those who were not infected, 528.6 and 403.0 g/day, respectively (p < 0.05). In addition, individuals with higher alcohol intake presented an increase in parasite load. The S. stercoralis diagnostic method with the highest sensitivity was APC, 97.9% (183/187). In conclusion, S. stercoralis seems to be the most frequent parasite found in alcoholic individuals from endemic areas and alcohol intake is positively associated with S. stercoralis larvae output. In addition, this study confirms that APC is the most sensitive parasitological method used for Strongyloides diagnosis.

Lateral Flow Dipstick Test for Serodiagnosis of Strongyloidiasis

The conventional method of detecting Strongyloides stercoralis in fecal samples has poor diagnostic sensitivity. Detection of Strongyloides-specific antibodies increases the sensitivity; however, most tests are ELISAs that use parasite extract which may cross-react with the sera of other helminth infections. To improve the serological diagnosis of strongyloidiasis, this study aimed at developing a sensitive and specific lateral flow rapid dipstick test. Two recombinant proteins, recombinant NIE (rNIE) and recombinant Ss1a (rSs1a), were used in preparing the dipstick, with gold-conjugated antihuman IgG4 as detector reagent. In parallel, the corresponding ELISA was performed. Both assays demonstrated diagnostic sensitivity of 91.3% (21/23) when tested with serum samples of patients with Strongyloides infection, and 100% specificity with 82 sera of asymptomatic (healthy) and those with other parasitic infections. The ELISA and dipstick test results were positively correlated to each other (r = 0.6114, P = 0.0019). The developed lateral flow dipstick test may improve the serodiagnosis of strongyloidiasis and merit further validation studies.

Strongyloides stercoralis Infection at Different Altitudes of the Cusco Region in Peru

Strongyloides stercoralis affects 30-100 million people worldwide. The burden is underestimated because of the paucity of studies, limited geographical areas surveyed, and poor quality of diagnostic tests. This study aimed at determining the epidemiology of strongyloidiasis using sensitive microscopy testing in rural populations living at different altitudes in Cusco, Peru. Data were collected from subjects aged > 3 years living in Quellouno (elevation 2,600 ft) and Limatambo (elevation 8,379 ft) districts. Subjects provided one fresh stool sample and answer a standardized questionnaire. Fresh stool was tested on site using the Baermann's test and agar plate culture. Formalin-preserved stool was tested by rapid sedimentation. Eighty percent (585/715) of eligible subjects consented to participate; after excluding subjects with missing data, 65% (462/715) were included. Fifty-five percentage were female; the median age was 33 years (interquartile range 13-52), and 72% had government health insurance. Half had intestinal parasites, and Strongyloides was the most common (24.5%) followed by Giardia (15.5%), Blastocystis (14.9%), and hookworm (11.5%). The agar plate culture detected more cases of Strongyloides than Baermann's or sedimentation tests. Strongyloides infection was more common at low altitude (26.4%) than at high altitude (18.6%), but the difference was not statistically significant (P = 0.08). Older age, walking barefoot, bathing in rivers/streams, and using municipal sewage were associated with strongyloidiasis. Strongyloides was the most prevalent parasite in the areas studied and was associated with demographic, socioeconomic, and sanitary factors.

Infection by Strongyloides stercoralis in immigrants with Chagas disease: evaluation of eosinophilia as screening method in primary care

OBJECTIVES

To evaluate co-infection of Strongyloides stercoralis and Trypanosoma cruzi and to assess eosinophilia as a screening test for the detection of S. stercoralis infection in patients with Chagas disease (CD).

METHODS

A retrospective diagnostic validation study was performed on serum samples from primary care patients diagnosed with CD in the southern Barcelona metropolitan area. All samples with eosinophilia (n = 87) and a random sample of non-eosinophilic sera (n = 180) were selected. Diagnosis of CD was based on positive serology by means of two tests: ORTHO® T. cruzi ELISA test, and BIO-FLASH® Chagas or Bioelisa CHAGAS. SCIMEDX ELISA STRONGY-96 was used to diagnose strongyloidiasis.

RESULTS

Strongyloides stercoralis serology was positive in 15% of patients of whom 95% showed eosinophilia, vs. 21% of those with negative serology (P < 0.001), with differences in the mean eosinophil count (0.49 vs. 0.27 × 10⁹ /l). Only 1.1% of patients with CD but without eosinophilia presented positive serology for S. stercoralis, whereas 44% of patients with CD and eosinophilia did (P < 0.001). Sensitivity and specificity values for eosinophilia were thus 95% and 79%, respectively. PPV was 42.5% and NPV, 98.9%.

CONCLUSIONS

The prevalence of co-infection by T. cruzi and S. stercoralis is not negligible and has probably been underestimated for years in many areas, due to frequently subclinical infections. Therefore, serology seems mandatory for these patients and the use of eosinophilia as initial screening could facilitate the task, decreasing the number of analyses to be performed.