The Unique Life Cycle of Strongyloides stercoralis and Implications for Public Health Action

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.

Factors associated with the sexual transmission of Strongyloides stercoralis in men who have sex with men: A systematic review

Strongyloides stercoralis is a parasitic worm with a complex life cycle and can cause significant morbidity, including a proctocolitis and life-threatening hyperinfection syndrome. Limited reports from non-endemic areas, including in men who have sex with men (MSM), suggest sexual transmission of S. stercoralis. In this systematic review of the published literature, we aimed to explore the associated factors of S. stercoralis in MSM. We systematically searched three bibliographical databases (MEDLINE, CINAHL and EMBASE) up to November 2022. We used a two-stage process to assess eligibility: the primary author conducted an initial screen of abstracts, and then three authors conducted independent full manuscripts to determine the final eligible manuscripts. We only included manuscripts written in English that contained data on specific factors associated with sexual transmission in MSM. We used the STROBE checklist to assess the risk of bias and synthesized the narrative data using the SWiM method. Seven manuscripts were eligible for this review (four case reports, one case series, one cross-sectional study and one experimental study), which included 22 individuals from Europe and the Americas. From these studies, S. stercoralis in MSM was associated with living with HIV (including having a low CD4 count and not using antiretrovirals), having a concomitant sexually transmitted infection (Chlamydia trachomatis, Neisseria gonorrhoeae, Treponema pallidum and hepatitis C) and a concomitant (sexually transmitted) protozoal infection (Entamoeba histolytica, Giardia lamblia), travel to the S. stercoralis endemic area, multiple sexual partners from endemic areas, oro-anal sexual contact and chemsex. Although limited by the number of cases in the literature, we have highlighted some possible biological and behavioural risk factors associated with the sexual transmission of S. stercoralis in MSM that could be used to both target future research and S. stercoralis public health control interventions.

Effect of Soil Temperature on Canine Soil-Transmitted Nematodes in Kandy District with the First Record of Hookworm, Ancylostoma tubaeforme from Sri Lanka

PURPOSE

Soil-transmitted nematodes (STNs) are widespread in tropical and subtropical regions, particularly where the communities are socio-economically challenged. We investigated the effect of soil temperature on the prevalence and intensity of STN infection in free-roaming dogs.

METHODS

Fresh faecal samples collected from free-roaming dogs in Digana and Pussellawa town areas in the Kandy District, Sri Lanka, were microscopically analysed for canine STNs. Soil temperature was measured at each sampling site. Highly prevalent canine hookworm Ancylostoma, was further studied using PCR and sequencing, followed by phylogenetic analysis.

RESULTS

The soil temperature ranged between 28 and 31 °C (mean = 29.79 °C) and 18-21 °C (mean = 19.52 °C) in Digana and Pussellawa, respectively, showing a significant difference in the two sites (Students t-test t = 1.68, p < 0.0001). Of the total 44 dogs sampled, 41 (93.2%) were positive for STNs. During microscopic analysis, five nematodes: Ancylostoma spp., Capillaria sp., Strongyloides sp., Toxocara canis, and Trichuris sp., were identified. Ancylostoma species (93.2%) were the most prevalent, followed by Strongyloides sp. (22.7%) and Toxocara canis (15.9%). Infection prevalence of Strongyloides sp. was higher in Digana (40.9%) compared to that in Pussellawa (4.5%; Chi-square test, χ2 = 8.28, p = 0.004) and also the infection intensity from Digana (EPG = 8.02 ± 20.2) compared to that from Pussellawa (0.45 ± 2.1; Mann Whitney U test, p = 0.006). Amplicons (ITS1-5.8S-ITS2) of the expected size for A. caninum, and A. tubaeforme were produced. An A. caninum sequence reported here (OQ101719) illustrated the highest similarity of 99.2% to one of the local sequences (MZ707153) upon pairwise comparison.

CONCLUSION

Digana, with a higher soil temperature than Pussellawa, had a significantly higher prevalence and infection intensity, particularly Strongyloides sp. This study also signifies the first molecular identification of hookworm species A. tubaeforme in Sri Lanka.

Strongyloides stercoralis in two dogs from a household in temperate Australia

Strongyloides stercoralis is parasite affecting both humans and dogs and is most prevalent in tropical and subtropical areas of Australia. This case report describes two dogs from a household in Sydney, New South Wales, one with chronic gastrointestinal signs and the other who was asymptomatic who were subsequently diagnosed with S. stercoralis. Diagnosis can be challenging in humans and dogs due to intermittent shedding and low worm burdens and in this case the symptomatic dog had Strongyloides spp. rhabitiform larvae detected on a direct faecal smear and PCR, the asymptomatic dog on PCR only. Obtained sequences from the symptomatic dog confirmed the presence of the S. stercoralis clade affecting both dogs and humans. Infection does not respond to commonly used deworming drugs for dogs. Treatment in both cases was undertaken using off-label doses of ivermectin and follow-up PCR testing was negative. This case report should increase practitioner awareness of this parasite as present and transmissible in temperate areas of Australia.

Strongyloidiasis in Auckland: A ten-year retrospective study of diagnosis, treatment and outcomes of a predominantly Polynesian and Fijian migrant cohort

BACKGROUND

Strongyloides stercoralis is not endemic in Aotearoa New Zealand (AoNZ). However, approximately one third of Auckland residents are born in endemic countries. This study aimed to describe the epidemiology and management of strongyloidiasis in Auckland, with a focus on migrants from Pacific Island Countries and Territories.

METHODS

This study retrospectively reviewed clinical, laboratory and pharmacy records data for all people diagnosed with strongyloidiasis in the Auckland region between July 2012 and June 2022. People with negative Strongyloides serology were included to estimate seropositivity rate by country of birth.

FINDINGS

Over ten years, 691 people were diagnosed with strongyloidiasis. Most diagnoses were made by serology alone (622, 90%). The median age was 63 years (range 15-92), 500 (72%) were male, and the majority were born in Polynesia (350, 51%), Fiji (130, 19%) or were of Pasifika ethnicity (an additional 7%). Twelve participants (1.7%) had severe strongyloidiasis at diagnosis. The total proportion treated with ivermectin was only 70% (484/691), with no differences between immunocompromised and immunocompetent participants, nor by ethnicity. The outcome of treatment (based on a combination of serology and/or eosinophilia and/or stool microscopy) could only be determined in 50% of the treated cohort. One participant failed treatment with ivermectin, experiencing recurrent strongyloidiasis, and another participant died in association with severe strongyloidiasis. The rate of 'positive' Strongyloides serology was highest among participants born in Samoa (48%), Fiji (39%), and Southeast Asian countries (34%).

INTERPRETATION

Strongyloidiasis was common and under-treated in Auckland during the study period. Clinicians should have a low threshold for considering strongyloidiasis in migrants from endemic countries, including Polynesia and Fiji.

Parasitic nematodes: dietary habits and their implications

Nematodes, a diverse group of roundworms, exhibit a wide range of dietary habits, including parasitism of animals and plants. These parasites cause substantial economic losses in agriculture and pose significant health challenges to humans and animals. This review explores the unique adaptations of parasitic nematodes, emphasizing their nutritional requirements and metabolic dependencies. Recent research has identified cross-kingdom compartmentalization of vitamin B5 biosynthesis in some parasitic nematodes, shedding light on coevolutionary dynamics and potential targets for control strategies. Several open questions remain regarding the complexity of nematode nutrition, host manipulation, evolutionary adaptations, and the influence of environmental factors on their metabolic processes. Understanding these aspects offers promising avenues for targeted interventions to manage and control these economically and medically important parasites.

Protocol for spatial prediction of soil transmitted helminth prevalence in the Western Pacific region using a meta-analytical approach

BACKGROUND

Soil transmitted helminth (STH) infections are estimated to impact 24% of the world's population and are responsible for chronic and debilitating morbidity. Disadvantaged communities are among the worst affected and are further marginalized as infection prevalence fuels the poverty cycle. Ambitious targets have been set to eliminate STH infections, but accurate epidemiological data will be required to inform appropriate interventions. This paper details the protocol for an analysis that aims to produce spatial prediction mapping of STH prevalence in the Western Pacific Region (WPR).

METHODS

The protocol follows the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocol (PRISMA-P) guidelines. The study design will combine the principles of systematic review, meta-analysis, and geospatial analysis. Systematic searches will be undertaken in PubMed, Scopus, ProQuest, Embase, and Web of Science for studies undertaken post 2000, to identify surveys that enable the prevalence of human STH infection within the WPR to be calculated. Covariate data for multivariable analysis will be obtained from publicly accessible sources. Survey data will be geolocated, and STH prevalence and covariates will be linked to produce a spatially referenced dataset for analysis. Bayesian model-based geostatistics will be used to generate spatially continuous estimates of STH prevalence mapped to a resolution of 1 km2. A separate geospatial model will be constructed for each STH species. Predictions of prevalence will be made for unsampled locations and maps will be overlaid for each STH species to obtain co-endemicity maps.

DISCUSSION

This protocol facilitates study replication and may be applied to other infectious diseases or alternate geographies. Results of the subsequent analysis will identify geographies with high STH prevalence's and can be used to inform resource allocation in combating this neglected tropical disease.

TRIAL REGISTRATION

Open Science Framework: osf.io/qmxcj.

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.

Syntenic relationship of chromosomes in Strongyloides species and Rhabditophanes diutinus based on the chromosome-level genome assemblies

The Strongyloides clade, to which the parasitic nematode genus Strongyloides belongs, contains taxa with diverse lifestyles, ranging from free-living to obligate vertebrate parasites. Reproductive strategies are also diverse in this group of nematodes, employing not only sexual reproduction but also parthenogenesis, making it an attractive group to study genome adaptation to specific conditions. An in-depth understanding of genome evolution, however, has been hampered by fragmented genome assemblies. In this study, we generated chromosome-level genome assemblies for two Strongyloides species and the outgroup species Rhabditophanes diutinus using long-read sequencing and high-throughput chromosome conformation capture (Hi-C). Our synteny analyses revealed a clearer picture of chromosome evolution in this group, suggesting that a functional sex chromosome has been maintained throughout the group. We further investigated sex chromosome dynamics in the lifecycle of Strongyloides ratti and found that bivalent formation in oocytes appears to be important for male production in the mitotic parthenogenesis. This article is part of the Theo Murphy meeting issue 'Strongyloides: omics to worm-free populations'.

The transmission dynamics of Strongyloides stercoralis and the impact of mass drug administration

The epidemiology of Strongyloides stercoralis is briefly reviewed with an emphasis on cross section and longitudinal studies of infection prevalence stratified by age, performance of different diagnostic tools, mass drug administration (MDA) impact and estimates of key population parameters within the complex life cycle of the parasite that determine transmission intensity and response to control measures. The paucity of studies is highlighted, and gaps in current knowledge identified about the population biology of this very prevalent infection in tropical and sub-tropical regions around the world. A stochastic individual based stochastic model is described in part to highlight gaps in knowledge. The impact of repeated MDA is simulated to illustrate some aspects of transmission dynamics of this helminth infection. Specifically, the impact and bounce back times in either the intervals between treatment rounds, or post the cessation of treatment, depend critically on the magnitude of two distinct components of the basic reproductive number R0. The absence of data on these key components is highlighted, as is the value of studies of longitudinal cohorts of people in regions of endemic infection post rounds of MDA to record how infection levels bounce back post treatment at individual and population levels of study. This article is part of the Theo Murphy meeting issue 'Strongyloides: omics to worm-free populations'.

Is strongyloidiasis a zoonosis from dogs?

Strongyloides stercoralis infection remains a major veterinary and public health challenge globally. This chronic and potentially lifelong disease has fatal outcomes in immunosuppressed people and dogs. Currently, the role of dogs in the transmission cycle of human strongyloidiasis remains enigmatic. While zoonotic transmission to humans from companion animals has been proposed, this has not been confirmed. Modern molecular methods have allowed greater opportunity to explore the genotypes of S. stercoralis in dogs and humans. Work thus far has demonstrated that at least two distinct lineages exist, one apparently confined to canine hosts and one found in canine, feline, human and non-human primate hosts. Although genotyping of dog and human isolates from the same village has demonstrated identical genotypes in both species, coprophagia of human waste by dogs confounds interpretation. It remains unclear if dogs act as a zoonotic reservoir for human infection, or vice versa, or if this occurs only in some regions of the world and not in others. These questions must be answered before effective control strategies for strongyloidiasis can be instituted. This review explores the evidence for and against cross-species transmission of S. stercoralis between dogs and humans and summarizes future directions for research in this area. This article is part of the Theo Murphy meeting Issue 'Strongyloides: omics to worm-free populations'.

Human strongyloidiasis: complexities and pathways forward

Strongyloidiasis is a World Health Organization neglected tropical disease usually caused by Strongyloides stercoralis, a parasitic worm with a complex life cycle. Globally, 300-600 million people are infected through contact with fecally contaminated soil. An autoinfective component of the life cycle can lead to chronic infection that may be asymptomatic or cause long-term symptoms, including malnourishment in children. Low larval output can limit the sensitivity of detection in stool, with serology being effective but less sensitive in immunocompromise. Host immunosuppression can trigger catastrophic, fatal hyperinfection/dissemination, where large numbers of larvae pierce the bowel wall and disseminate throughout the organs. Stable disease is effectively treated by single-dose ivermectin, with disease in immunocompromised patients treated with multiple doses. Strategies for management include raising awareness, clarifying zoonotic potential, the development and use of effective diagnostic tests for epidemiological studies and individual diagnosis, and the implementation of treatment programs with research into therapeutic alternatives and medication safety.

First field study using Strong-LAMP for diagnosis of strongyloidiasis in Cubal, Angola

BACKGROUND

Strongyloides stercoralis infection is a common neglected tropical disease distributed worldwide, mainly in tropical and subtropical climates. The impact of S. stercoralis infections on human health ranges from mild asymptomatic infections to chronic strongyloidiasis unnoticeable until the host is immunosuppressed. In severe strongyloidiasis, a syndrome of hyperinfection and larval dissemination to various organs can occur with high mortality rates. The diagnosis of strongyloidiasis is challenging because of the absence of a single standard reference test with high sensitivity and specificity, which also makes it difficult to estimate the accuracy of other diagnostic tests. This study aimed to evaluate, for the first time, the use of an easy-to-perform loop-mediated isothermal amplification (LAMP) colorimetric assay (named Strong-LAMP) for the molecular screening of strongyloidiasis in stool samples from patients in a low-resource endemic area in Cubal, Angola. To compare different LAMP application scenarios, the performance of the Strong-LAMP under field conditions in Angola was reassessed in a well-equipped reference laboratory in Spain and compared with a quantitative polymerase chain reaction (qPCR) method.

METHODS

A total of 192 stool samples were collected from adult population in Cubal, Angola, and examined by parasitological methods (direct saline microscopy and Baermann's technique). DNA was extracted from each stool sample using a commercial kit and tested by the colorimetric Strong-LAMP assay for the detection of Strongyloides spp. under field conditions. Furthermore, all samples were shipped to a well-equipped laboratory in Spain, reanalysed by the same procedure and compared with a qPCR method. The overall results after testing were compared.

RESULTS

Strongyloides stercoralis larvae were identified by direct saline microscopy and Baermann in a total of 10/192 (5.2%) and 18/192 (9.4%) stool samples, respectively. Other helminth and protozoan species were also identified. The Strong-LAMP-positive results were visually detected in 69/192 (35.9%) stool samples. The comparison of Strong-LAMP results in field conditions and at a reference laboratory matched in a total of 146/192 (76.0%) samples. A total of 24/192 (12.5%) stool samples tested positive by qPCR.

CONCLUSIONS

This is the first study in which colorimetric Strong-LAMP has been clinically evaluated in a resource-poor strongyloidiasis endemic area. Strong-LAMP has been shown to be more effective in screening for strongyloidiasis than parasitological methods under field conditions and qPCR in the laboratory. Our Strong-LAMP has proven to be a field-friendly and highly accurate molecular test for the diagnosis of strongyloidiasis.

A Unique Patient Presentation of Disseminated Strongyloidiasis: Unraveling the Clinical Complexity of an Immunocompromised Patient

Strongyloidiasis is a rare parasitic disease that can remain dormant and asymptomatic in many individuals. However, in cases of immunosuppression, the motility rate of the Strongyloides parasite increases significantly. This case study presents a unique clinical scenario involving an 88-year-old Hispanic male with a disseminated Strongyloidesinfection. The patient's medical history includes coronary artery disease, a history of percutaneous coronary intervention, heart failure with reduced ejection fraction and subsequent recovery of left ventricular function, hypertension, dyslipidemia, mantle cell lymphoma being treated with rituximab every two months since 2019, and chronic anemia. This case emphasizes the importance for physicians to consider strongyloidiasis when faced with a diverse range of symptoms, including syndrome of inappropriate antidiuretic hormone secretion (SIADH), rash, gastrointestinal upset, urinary retention, chronic anemia, and chronic eosinophilia, as these manifestations may share a common origin.

Strongyloides stercoralis infection reduces Fusicatenibacter and Anaerostipes in the gut and increases bacterial amino-acid metabolism in early-stage chronic kidney disease

Understanding gut bacterial composition and proteome changes in patients with early-stage chronic kidney disease (CKD) could lead to better methods of controlling the disease progression. Here, we investigated the gut microbiome and microbial functions in patients with S. stercoralis infection (strongyloidiasis) and early-stage CKD. Thirty-five patients with early stages (1-3) of CKD were placed in two groups matched for population characteristics and biochemical parameters, 12 patients with strongyloidiasis in one group and 23 uninfected patients in the other. From every individual, a sample of their feces was obtained and processed for 16S rRNA sequencing and metaproteomic analysis using tandem liquid chromatography-mass spectrometry (LC-MS/MS). Strongyloides stercoralis infection per se did not significantly alter gut microbial diversity. However, certain genera (Bacteroides, Faecalibacterium, Fusicatenibacter, Sarcina, and Anaerostipes) were significantly more abundant in infection-free CKD patients than in infected individuals. The genera Peptoclostridium and Catenibacterium were enriched in infected patients. Among the significantly altered genera, Fusicatenibacter and Anaerostipes were the most correlated with renal parameters. The relative abundance of members of the genus Fusicatenibacter was moderately positively correlated with estimated glomerular filtration rate (eGFR) (r = 0.335, p = 0.049) and negatively with serum creatinine (r = -0.35, p = 0.039). Anaerostipes, on the other hand, showed a near-significant positive correlation with eGFR (r = 0.296, p = 0.084). Individuals with S. stercoralis infection had higher levels of bacterial proteins involved in amino-acid metabolism. Analysis using STITCH predicted that bacterial amino-acid metabolism may also be involved in the production of colon-derived uremic toxin (indole), a toxic substance known to promote CKD. Strongyloides stercoralis infection is, therefore, associated with reduced abundance of Fusicatenibacter and Anaerostipes (two genera possibly beneficial for kidney function) and with increased bacterial amino-acid metabolism in the early-stages of CKD, potentially producing uremic toxin. This study provides useful information for prevention of progression of CKD beyond the early stages.

Strongyloides coinfection in COVID-19 patients treated with corticosteroids: A systematic review

The COVID-19 pandemic linked to the virus SARS-CoV-2, which began in China, affected ∼765 million people as of 30 April 2023. The widespread use of corticosteroids for the symptomatic treatment of COVID-19 could lead to the reactivation of infections of opportunistic pathogens, including Strongyloides. We sought to determine the clinical symptoms and demographic characteristics of SARS-CoV-2-Strongyloides co-infection, particularly in patients with severe disease and being treated with immunosuppressive drugs. To do this, we undertook a systematic review of the literature, and searched public accessible scientific databases-the Web of Science, Scopus, PubMed/Medline and Embase -for eligible studies (1 December 2019 to 30 August 2022). The review protocol is registered in PROSPERO (CRD42022377062). Descriptive statistical analyses were used to present the clinical and laboratory parameters of the co-infection; for this, we calculated prevalence using the following formula: positive cases/total number of cases × 100. Of a total of 593 studies identified, 17 studies reporting 26 co-infected patients met the criteria for inclusion in this review. The median age of these patients was 55.14 years. Most of cases (53.8%) were treated with dexamethasone, followed by methylprednisolone (26.9%). Eighteen of 26 patients were immigrants living in European countries or the USA; most of these immigrants originated from Latin America (58%) and South-East Asia (11%). The commonest symptoms of co-infection were abdominal pain (50%), fever (46.1%), dyspnoea (30.7%) and cough (30.7%), and frequently reported laboratory findings were high absolute eosinophil count (38.4%), high white blood cell count (30.7%), high C-reactive protein (23.0%) and high neutrophil count (19.2%). Two of the 26 patients (7.7%) had fatal outcomes. Most of the SARS-CoV-2-Strongyloides coinfected cases were immigrants living in developed countries, emphasising the need for clinicians in these countries to be aware of clinical and laboratory parameters associated with such co-infections, as well as the key importance of rapid and accurate diagnostic tests for timely and effective diagnosis and patient management.

Case Report: Duodenal Papillary Stenosis Secondary to Strongyloides stercoralis Infection in a Non-Immunocompromised Host

Strongyloides stercoralis infection is a common infection in tropical and subtropical regions and is considered one of the "neglected tropical diseases." Owing to its life cycle, this infection can remain undetectable for years, preventing an early diagnosis and prompt treatment. We report the case of a 65-year-old woman who presented to us with a history of nausea, abdominal pain, bloating, and weight loss and, after initial radiologic and laboratory workup, was diagnosed with a periampullary mass with no secondary spread. She underwent an uneventful pylorus-preserving pancreatoduodenectomy, and on histopathological study of the lesion, a diagnosis of S. stercoralis infection was confirmed. This case stands out because of the importance of keeping S. stercoralis infections as a differential diagnosis of periampullary masses, particularly when the patient comes from regions where S. stercoralis is prevalent.

Enhancing screening adherence for strongyloides infection in latinx inpatients with COVID-19: a local protocol implementation study

Strongyloides stercoralis hyperinfection syndrome has been observed in immunosuppressed coronavirus disease 2019 (COVID-19) patients. Detecting and treating asymptomatic Strongyloides infection in individuals from endemic areas can effectively prevent hyperinfection. Unfortunately, many clinicians are unaware of this neglected infection. Therefore, we aimed to evaluate whether including Strongyloides screening in COVID-19 management protocols would encourage this practice. To accomplish this, we conducted a retrospective single-center study at 'Hospital Universitario 12 de Octubre' in Madrid, Spain, comparing two consecutive cohorts. The first cohort comprised all Latinx patients over 18 years old who were admitted for COVID-19 between March 1st and April 30th, 2020. The second cohort consisted of Latinx patients admitted between July 1st and December 31st, 2020, following an amendment to the COVID-19 management protocol that recommended screening for strongyloidiasis in at-risk patients. We identified 559 and 795 patients in the first and second periods, respectively. The percentage of individuals screened increased significantly from 8.8% to 51.6% after the screening recommendation was included in the protocol (odds ratio [OR] 11.08, 95% confidence interval [CI] 8.01-15.33). In both periods, the screening rate was significantly higher among those receiving immunosuppression than those who did not receive steroids and/or tocilizumab. No other factors influenced the screening rate. In conclusion, including strongyloidiasis screening recommendations in COVID-19 management protocols led to its increased implementation. However, the overall screening rate remained low, emphasizing the need for further efforts to enhance screening practices.

Strongyloides stercoralis Dissemination and Hyperinfection Associated with Long-Term Steroid Treatment in a Neurosurgical Population

Strongyloidiasis develops from the infection with Strongyloides stercoralis (Family: Strongylidae) and was recently considered a neglected tropical disease by the World Health Organization due to its global distribution and high burden of infection. Here, we present the cases of two patients under corticosteroid therapy after neurosurgical surgery who developed septic shock-like hyperinfection syndrome due to disseminated strongyloidiasis. The first case is a 77-year-old man from Cape Verde who was diagnosed with an extra-axial right parietal brain mass. He was given dexamethasone and was submitted to a biparietal craniotomy. His condition deteriorated and he was admitted to the intensive care unit (ICU), where he was diagnosed with disseminated strongyloidiasis with hyperinfection. Anthelmintic treatment and corticosteroid therapy were rapidly tapered and stopped. Neurological dysfunction persisted and the patient was transferred to the ward. The patient had died after complications of hospital-acquired pneumonia. The second case is a 47-year-old man from Guinea-Bissau who was diagnosed with a space-occupying lesion in the right temporal region and started treatment with dexamethasone. He underwent a craniectomy with partial excision of the lesion (high-grade glioma). Later his neurologic state worsened, and he was diagnosed with septic shock and hospital-acquired pneumonia. He was admitted to the ICU, the diagnosis of disseminated strongyloidiasis and hyperinfection syndrome was made and he initiated treatment with ivermectin and albendazole. Corticosteroid therapy was tapered. The patient's clinical status deteriorated, and multiple opportunistic infections were diagnosed during the ICU stay, which lead him to die. Clinicians should have a high index of suspicion when in the presence of corticosteroid-treated patients with sepsis. Preventive strategies and subsequent treatment should be considered in patients with a risk of acquisition or dissemination. Treating severe strongyloidiasis is still a clinical challenge and a delayed diagnosis can significantly worsen the outcomes of the patients affected, as seen in the presented cases.

Ameliorating the antiparasitic activity of the multifaceted drug ivermectin through a polymer nanocapsule formulation

Ivermectin (IVM) is a potent antiparasitic widely used in human and veterinary medicine. However, the low oral bioavailability of IVM restricts its therapeutic potential in many parasitic infections, highlighting the need for novel formulation approaches. In this study, poly(ε-caprolactone) (PCL) nanocapsules containing IVM were successfully developed using the nanoprecipitation method. Pumpkin seed oil (PSO) was used as an oily core in the developed nanocapsules. Previously, PSO was chemically analyzed by headspace solid-phase microextraction coupled to gas chromatography/mass spectrometry (HS-SPME/GC-MS). The solubility of IVM in PSO was found to be 4,266.5 ± 38.6 μg/mL. In addition, the partition coefficient of IVM in PSO/water presented a logP of 2.44. A number of nanocapsule batches were produced by factorial design resulting in an optimized formulation. Negatively charged nanocapsules measuring around 400 nm demonstrated unimodal size distribution, and presented regular spherical morphology under transmission electron microscopy. High encapsulation efficiency (98-100%) was determined by HPLC. IVM-loaded capsules were found to be stable in nanosuspensions at 4°C and 25°C, with no significant variations in particle size observed over a period of 150 days. Nanoencapsulated IVM (0.3 mM) presented reduced toxicity to J774 macrophages and L929 fibroblasts compared to free IVM. Moreover, IVM-loaded nanocapsules also demonstrated enhanced in vitro anthelmintic activity against Strongyloides venezuelensis in comparison to free IVM. Collectively, the present findings demonstrate the promising potential of PCL-PSO nanocapsules to improve the antiparasitic effects exerted by IVM.

A Rare Case of Strongyloides stercoralis Hyperinfection in a Diabetic Patient from Romania—Case Report and Review of the Literature

Severe cases of strongyloidiasis are most often associated with multiple causes of immune suppression, such as corticoid treatment and HTLV (human T-lymphotropic virus) coinfection. Diabetes is not traditionally considered a risk factor for the development of severe strongyloidiasis. We report a rare case of autochthonous severe strongyloidiasis in Romania, a European country with a temperate climate. A 71-year-old patient with no prior travel history was admitted with multiple gastrointestinal complaints and recent weight loss. CT (computed tomography) scans indicated duodenal wall thickening, and duodenal endoscopy evidenced mucosal inflammation, ulcerations and partial duodenal obstruction at D4. Microscopic examination of stool samples and biopsy specimens from the gastric and duodenal mucosa revealed an increased larval burden characteristic of Strongyloides stercoralis hyperinfection. Sequential treatment with albendazole and ivermectin achieved parasitological cure and complete recovery. The novelty of our case stems from the scarcity of severe strongyloidiasis cases reported in Europe and especially in Romania, the absence of other risk factors in our patient aside from diabetes, the involvement of the gastric mucosa and the rare presentation as partial duodenal obstruction. This case highlights the importance of considering strongyloidiasis as a differential diagnosis, even in temperate climates where cases are sporadic, in cases in which immune suppression is not evident and in the absence of eosinophilia. The case is presented in the context of the first literature review examining the relationship between severe strongyloidiasis and diabetes, emphasizing diabetes as a possible risk factor for severe strongyloidiasis.

Larva Currens: Report of Seven Cases and Literature Review

Strongyloidiasis is a frequent and often unrecognized parasitic disease because of the frequently asymptomatic nature and lack of sensitivity of diagnostic tests. Under conditions of immunosuppression (particularly systemic corticosteroid treatment), potentially fatal dissemination may occur. Thus, prevention and early diagnosis are important. Larva currens is a rare and pathognomonic cutaneous sign of strongyloidiasis, but is poorly described because of its unpredictable and fleeting occurrence. We report seven imported cases of larva currens seen in Paris between 1990 and 2020. We illustrate the clinical and biological features of this specific but uncommon sign of strongyloidiasis with clinical pictures. There were three males and four females, aged between 29 and 58 years. There were five migrants from endemic countries, one tourist and one expatriate. Digestive disorders were the main extracutaneous signs. All patients had eosinophilia above 0.5 G/L. All cases were confirmed by stool tests. All were cured with ivermectin. The rapidity and the short duration of the creeping eruption distinguish it from other parasitoses. Ivermectin is a treatment of choice. The key point is to think about preventing disseminated strongyloidiasis before giving corticosteroids not only among migrants but also among expatriates and tourists in endemic countries.

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.

Prevalence and Associated Risk Factors of Intestinal Parasitic Infections: A Population-Based Study in Phra Lap Sub-District, Mueang Khon Kaen District, Khon Kaen Province, Northeastern Thailand

Intestinal parasitic infections are still a crucial problem among communities in Northeast Thailand. Misuse of antiparasitic drugs and unhealthy food behaviors are known. This study aimed to explore the prevalence, behavioral health factors, and motivation for self-treatment of anti-parasitic drugs in this area. A community-based cross-sectional study was conducted in Phra Lap sub-district, Mu Khon Kaen district, Khon Kaen province, Northeast Thailand, in 2016. A total of 419 participants were recruited to complete a self-administered questionnaire and stool examination. Binary logistic regression was used to assess the association between the risk factor and parasitic infection. Forty-two participants (10%; 95%CI 7.5-13.3) were positive for at least one parasite species. In this community, the most detected intestinal parasite was Opisthorchis viverrini (5.3%), followed by Strongyloides stercoralis (3.1%). A total of 67.5% of the participants had the experience of anti-parasitic drug treatment within previous 1 year, and "Often eat raw food" was the most common reason for the use of anti-parasitic drugs. On multivariate analysis, parasitic infections were significantly associated with male gender (ORadj. 2.42; 95%CI 1.00-5.85), age ≥ 60 years (ORadj. 7.55; 95%CI 1.60-35.76), and often consuming raw food of at least one type (ORadj. 2.37; 95%CI 1.03-5.44). Given these findings, correction of the dietary habit of eating raw fish/meat, which is the most important measure, and limitation of the use of anthelmintic treatment for individuals with stools positive for ova as well as emphasis on sanitary toilets will be implemented for the prevention and control of parasitic infection in endemic communities.

Prevalence and Subtype Distribution of Blastocystis Isolated from School-Aged Children in the Thai-Myanmar Border, Ratchaburi Province, Thailand

Blastocystis is one of the most common enteric protozoa that inhabits the intestinal tract of humans and different animals. Moreover, it has a worldwide geographic distribution. Its main mode of transmission is via the fecal-oral route. At present, 26 subtypes are widely distributed across both humans and animals. The current study aimed to determine the prevalence and subtype distribution of Blastocystis among school-aged children living on the Thai-Myanmar border, Ratchaburi province, Thailand. In total, 508 samples were collected from children at six schools. The prevalence of Blastocystis infection was amplified and sequenced in the 600 bp barcode region of the small-subunit ribosomal RNA (SSU rRNA). The overall prevalence of Blastocystis infection was 3.35% (17/508). ST3 (11/17) was the most predominant subtype, followed by ST1 (5/17) and ST2 (1/17). A phylogenetic tree was constructed based on the Tamura92+G+I model using the maximum-likelihood algorithm. Surprisingly, all sequences of the ST3-positive samples were closely correlated with the cattle-derived sequence. Meanwhile, all sequences of the Blastocystis ST1-positive samples were closely correlated with the human-derived sequence. Nevertheless, further studies should be conducted to validate the zoonotic transmission of Blastocystis. Based on our findings, personal hygiene and sanitation should be improved to promote better health in children in this area.

A simple parasitological technique to increase detection of Strongyloides stercoralis in Bolivian primary health care system

BACKGROUND

Strongyloides stercoralis is widespread; however, there is limited information on its prevalence owing to laboratory underestimation and low clinical manifestations. The Baermann method and agar culture stand out among the parasitological techniques. Strongyloides stercoralis is present in Bolivia, but its prevalence in children remains unknown. The objective of this study was to estimate the applicability of simple parasitological techniques to increase the detection of this parasite in children living in the tropics.

METHODS

This cross-sectional study was conducted in a tropical village in Cochabamba, Bolivia. Participants were 304 children aged 5 - 12 years who provided stool samples for different parasitological analyses (direct examination, Ritchie, Baermann, and Dancescu techniques), and their parents provided informed consent.

RESULTS

Up to 64.8% of pathogenic parasites were detected using the modified Ritchie method. The Baermann technique identified 17.8% of Strongyloides stercoralis cases, and a high sensitivity with respect to the Baermann technique was only for the Dancescu technique (75.9%) that is also specific for Strongyloides stercoralis, followed by 66.7% for the modified Ritchie technique, which is used in second-line care.

DISCUSSION

The Baermann technique is the best parasitological option for improving Strongyloides stercoralis diagnosis in the first-line care of the Primary Health Care System. A particular cycle of reinfection, combined with the environment and some other risk factors are related with persistence. Control is difficult without a proper diagnosis, and the Baermann technique is an approach to the solution. We conclude that with a high suspicion of the presence of Strongyloides stercoralis, the use of the Baermann technique is strongly recommended as support for direct examination in primary health care systems especially in tropical areas.

The Strongyloides bioassay toolbox: A unique opportunity to accelerate functional biology for nematode parasites

Caenorhabditis elegans is a uniquely powerful tool to aid understanding of fundamental nematode biology. While C. elegans boasts an unrivalled array of functional genomics tools and phenotype bioassays the inherent differences between free-living and parasitic nematodes underscores the need to develop these approaches in tractable parasite models. Advances in functional genomics approaches, including RNA interference and CRISPR/Cas9 gene editing, in the parasitic nematodes Strongyloides ratti and Strongyloides stercoralis provide a unique and timely opportunity to probe basic parasite biology and reveal novel anthelmintic targets in species that are both experimentally and therapeutically relevant pathogens. While Strongyloides functional genomics tools have progressed rapidly, the complementary range of bioassays required to elucidate phenotypic outcomes post-functional genomics remain more limited in scope. To adequately support the exploitation of functional genomic pipelines for studies of gene function in Strongyloides a comprehensive set of species- and parasite-specific quantitative bioassays are required to assess nematode behaviours post-genetic manipulation. Here we review the scope of the current Strongyloides bioassay toolbox, how established Strongyloides bioassays have advanced knowledge of parasite biology, opportunities for Strongyloides bioassay development and, the need for investment in tractable model parasite platforms such as Strongyloides to drive the discovery of novel targets for parasite control.

Current pharmacotherapeutic strategies for Strongyloidiasis and the complications in its treatment

INTRODUCTION

Strongyloidiasis, an infection caused by the soil-transmitted helminth Strongyloides stercoralis, can lead immunocompromised people to a life-threatening syndrome. We highlight here current and emerging pharmacotherapeutic strategies for strongyloidiasis and discuss treatment protocols according to patient cohort. We searched PubMed and Embase for papers published on this topic between 1990 and May 2022.

AREAS COVERED

Ivermectin is the first-line drug, with an estimated efficacy of about 86% and excellent tolerability. Albendazole has a lower efficacy, with usage advised when ivermectin is not available or not recommended. Moxidectin might be a valid alternative to ivermectin, with the advantage of being a dose-independent formulation.

EXPERT OPINION

The standard dose of ivermectin is 200 µg/kg single dose orally, but multiple doses might be needed in immunosuppressed patients. In the case of hyperinfection, repeated doses are recommended up to 2 weeks after clearance of larvae from biological fluids, with close monitoring and further dosing based on review. Subcutaneous ivermectin is used where there is impaired intestinal absorption/paralytic ileus. In pregnant or lactating women, studies have not identified increased risk with ivermectin use. However, with limited available data, a risk-benefit assessment should be considered for each case.

Mapping the global distribution of Strongyloides stercoralis and hookworms by ecological niche modeling

Background

The WHO has established a control strategy for Strongyloides stercoralis in school-aged children as well as targets and to maintain control programs for Ascaris lumbricoides, Trichuris trichiura and hookworms. For an efficient development of control programs, it is necessary to know the target countries around the world, as well as the areas within each country where efforts should be focused. Therefore, maps that provide information on the areas at risk for soil-transmitted helminth (STH) infections on a national and sub-national scale would allow for a better allocation of resources.

Methods

We used the ecological niche models MaxEnt and Kuenm R library to estimate the global distribution of S. stercoralis and hookworms. We used occurrence points of both species extracted from surveys of two literature reviews and from the Global Atlas of Helminth Infection database, together with 14 raster maps of environmental variables.

Results

We obtained two raster maps with the presence probability of S. stercoralis and hookworm infections at a global level and then estimated the global population at risk to be 2.6 and 3.4 billion, respectively. The population at risk was also estimated at the country level using estimations for areas as small as 25 km². A relationship was found between the probability of the presence of S. stercoralis and its prevalence, and a raster map was generated. Annual precipitation, annual temperature, soil carbon content and land cover were the main associated environmental variables. The ecological niches of Strongyloides stercoralis and hookworms had an overlap of 68%.

Conclusions

Here we provide information that can be used for developing more efficient and integrated control strategies for S. stercoralis and hookworm infections. This information can be annexed to the study of other risk factors or even other diseases to assess the health status of a community.

Graphical Abstarct

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05284-w.

Pulmonary Infection Caused by Strongyloides stercoralis

PURPOSE

Strongyloidiasis is mainly prevalent in developing countries with poor economic and sanitary conditions. The clinical manifestations of Strongyloides stercoralis infection are complex and diverse, lacking specificity, which can easily lead to misdiagnosis and delayed treatment.

METHODS

An elderly male patient, repeated cough and expectoration for 4 years, with exacerbation and dyspnea for 10 days, was admitted to hospital. Sputum culture and smear were taken for examination. Nematode larvae were found under the microscope. Nematodes were also found in feces.

RESULTS

Upon confirmation, the patient was diagnosed with a pulmonary infection caused by Strongyloides stercoralis. After treatment with albendazole, the symptoms improved, and the patient was discharged.

CONCLUSION

In this case report, combination of microscopic examination of sputum and alveolar lavage fluid and CT scan were used to quickly identify the cause of the patient, it provides a diagnostic basis and method for clinical treatment.

Strongyloides hyper-infection in a lung transplant recipient: Case report and review of the literature

CASE PRESENTATION

A 63-year-old man with a left single lung transplant for end-stage combined restrictive and obstructive lung disease developed persistent pulmonary infiltrates and recurrent gram-negative bacteremia post-transplant. Bronchoalveolar lavage fluid revealed a nematode on Papanicolau staining compatible with Strongyloides stercoralis larvae on day 50 post-transplant. Although Strongyloides serology performed post-transplant was negative, a retrospective review of the medical record revealed marked peripheral blood eosinophilia on several occasions before transplantation. Despite reduction in immunosuppression and treatment with albendazole and ivermectin, the patient developed another episode of Escherichia coli bacteremia. He died 3 months post-transplant from pulmonary and neurological complications.

DIAGNOSIS

Strongyloides hyper-infection.

DISCUSSION

Strongyloides hyper-infection syndrome is known to occur in immunocompromised patients, but it has only been reported once in a lung transplant recipient. This case illustrates the importance of screening for parasitic infections before transplantation in patients with marked eosinophilia, especially among immigrants from countries in which Strongyloides is endemic. Hyper-infection syndrome may appear years after infection in the context of immunosuppression or immunodeficiency. This case also highlights the association between Strongyloides hyper-infection and bacteremia with enteric organisms.

Soil-Transmitted Helminths and Anaemia: A Neglected Association Outside the Tropics

Anaemia is an important cause of morbidity and mortality globally. Among infectious agents responsible for anaemia, helminthic infections are often neglected, particularly in non-endemic countries. However, they should not be neglected in this setting, as international travel and migration are on the rise. In this narrative review, we aimed to describe soil-transmitted helminths as a cause of or contributing factor to anaemia, focusing on hookworms (Necator americanus and Ancylostoma duodenale), the whipworm (Trichuris trichiura), the roundworm (Ascaris lumbricoides), and the threadworm (Strongyloides stercoralis). A general review on the epidemiology, lifecycle, and clinical spectrum of anaemia is proposed, with a special focus on helminthic infections’ association with anaemia as well as the diagnostic approach, which are both particularly important in non-endemic settings.

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.

Strongyloides stercoralis and Trypanosoma cruzi coinfections in a highly endemic area in Argentina

Background

Strongyloidiasis and Chagas disease are endemic in northern Argentina. In this study we evaluate the association between S. stercoralis and T. cruzi infections in villages with diverse prevalence levels for these parasites. Further understanding in the relationship between these Neglected Tropical Diseases of South America is relevant for the design of integrated control measures as well as exploring potential biologic interactions.

Methodology

Community based cross-sectional studies were carried in different villages of the Chaco and Yungas regions in Argentina. Individuals were diagnosed by serology for S. stercoralis and T. cruzi. The association between S. stercoralis and T. cruzi, and between anemia and the two parasites was evaluated using two approaches: marginal (Ma) and multilevel regression (Mu).

Results

A total of 706 individuals from six villages of northern Argentina were included. A total of 37% were positive for S. stercoralis, 14% were positive for T. cruzi and 5% were positive for both. No association was found between infection with S. stercoralis and T. cruzi in any of the models, but we found a negative correlation between the prevalence of these species in the different villages (r = -0.91). Adults (> 15 years) presented association with S. stercoralis (Ma OR = 2.72; Mu OR = 2.84) and T. cruzi (Ma OR = 5.12; Mu OR = 5.48). Also, 12% and 2% of the variance of infection with S. stercoralis and T. cruzi, respectively, could be explained by differences among villages. On the other hand, anemia was associated with infection with S. stercoralis (Ma OR = 1.73; Mu OR = 1.78) and was more prevalent in adults (Ma OR = 2.59; Mu OR = 2.69).

Conclusion

We found that coinfection between S. stercoralis and T. cruzi is not more frequent than chance in endemic areas. However, the high prevalence for both parasites, raises the need for an integrated strategy for the control of STH and Chagas disease.

Infections with S. stercoralis and T. cruzi belong to the group of neglected tropical diseases (NTDs). NTDs are influenced by climate and the presence of their vectors and host reservoirs in areas with structural poverty. S. stercoralis and T. cruzi have high prevalence in northern Argentina. Due to the high prevalence and chronicity of infections by these parasites, coinfection with both is possible. We conducted a cross sectional study in six villages in the north of Argentina. These villages have different prevalence for the two parasites and are located in different ecoregions (Chaco, Yungas and the border between these two). We found that coinfection between S. stercoralis and T. cruzi occurs only by chance; and the most affected groups for S. stercoralis and T. cruzi infection are adults. We also found that adults or individual with infection with S. stercoralis were more likely to have anemia. In addition, each village represents a different setting for infection with S. stercoralis and T. cruzi, and individuals in different villages presented differences in the probability of infection.

Determinant factors of chronic Strongyloides stercoralis infection among schoolchildren in Amhara National Regional State, northwest Ethiopia

BACKGROUND

Strongyloides stercoralis is one of the most neglected parasites that is commonly found in tropical and sub-tropical countries. The majority of chronic S. stercoralis infections are characterized by minor clinical signs and symptoms. The extent to which socio-demographic, personal and environmental risk factors associated with S. stercoralis infection is not well known in Amhara Regional, Ethiopia.

OBJECTIVE

This study aimed to assess socio-demographic, personal and environmental risk factors associated with S. stercoralis infection among schoolchildren in Amhara Region.

METHODS

A total of 844 schoolchildren were randomly selected and participated in the study. Stool samples were collected and checked for S. stercoralis infection using five diagnostic methods. A structured questionnaire was also used to obtain socio-demographic, personal and environmental data from parents of the children. The degree of association between socio-demographic, personal and environmental factors with S. stercoralis infection was first assessed by univariate logistic regression and then analyzed by multivariate logistic regression. Variables with p<0.05 were considered as statistically significant.

RESULTS

Among 844 participants, 329 (39.0%) were infected with S. stercoralis. Prevalences of S. stercoralis among 12-14 years old, males, and rural dwellers were 48.2% (109/226), 45.0% (196/436) and 41.1% (306/745), respectively. Being in the age group of 10-11years (AOR=1.56;95%CI:1.10-2.24), and 12-14 years (AOR=1.96;95%CI:1.32-2.90), male (AOR=1.55;95%CI:1.16-2.06), and rural dweller (AOR=1.86;95%CI:1.12-3.10); having family income of < 1000 Birr per month (AOR=2.03;95%CI:1.48-2.77), and family size of 5-9 members (AOR=2.36; 95%CI:1.57-3.54) were significantly associated with S. stercoralis infection. The habit of not wearing shoes (AOR=1.41; 95%CI:1.05-1.90), close contacting with pets (AOR=1.49;95%:1.09-2.04), participating in irrigation (AOR=1.49; 95%CI:1.10-2.00) and playing with soil (AOR=1.62;95%CI:1.20-2.18) were risk factors of S. stercoralis infection. Besides, presence of wet environment (AOR=1.62;95%CI:1.19-2.22), living around sandy soil (AOR=2.75; 95%CI: 1.81-4.19) and red clay soil (AOR=2.24;95%CI:1.58-3.17), living in semi-highland folds (AOR=2.47;95%CI:1.48-4.14) and highland areas (AOR=1.65;95%CI:1.06-2.57) were determinant factors for S. stercoralis.

CONCLUSION

S. stercoralis infection among schoolchildren was highly prevalent in Amhara Region. Several determinant factors were also identified. Therefore, proper implementation of sanitation and hygiene programs and health care of pets should be advocated to break the transmission cycle of S. stercoralis.

Characterization of the endogenous DAF-12 ligand and its use as an anthelmintic agent in Strongyloides stercoralis

A prevalent feature of Strongyloides stercoralis is a life-long and potentially lethal infection that is due to the nematode parasite's ability to autoinfect and, thereby, self-replicate within its host. Here, we investigated the role of the parasite's nuclear receptor, Ss-DAF-12, in governing infection. We identified Δ7-DA as the endogenous Ss-DAF-12 ligand and elucidated the hormone's biosynthetic pathway. Genetic loss of function of the ligand's rate-limiting enzyme demonstrated that Δ7-DA synthesis is necessary for parasite reproduction, whereas its absence is required for the development of infectious larvae. Availability of the ligand permits Ss-DAF-12 to function as an on/off switch governing autoinfection, making it vulnerable to therapeutic intervention. In a preclinical model of hyperinfection, pharmacologic activation of DAF-12 suppressed autoinfection and markedly reduced lethality. Moreover, when Δ7-DA was administered with ivermectin, the current but limited drug of choice for treating strongyloidiasis, the combinatorial effects of the two drugs resulted in a near cure of the disease.

An annotated checklist of the eukaryotic parasites of humans, exclusive of fungi and algae

The classification of "parasites" in the medical field is a challenging notion, a group which historically has included all eukaryotes exclusive of fungi that invade and derive resources from the human host. Since antiquity, humans have been identifying and documenting parasitic infections, and this collective catalog of parasitic agents has expanded considerably with technology. As our understanding of species boundaries and the use of molecular tools has evolved, so has our concept of the taxonomy of human parasites. Consequently, new species have been recognized while others have been relegated to synonyms. On the other hand, the decline of expertise in classical parasitology and limited curricula have led to a loss of awareness of many rarely encountered species. Here, we provide a comprehensive checklist of all reported eukaryotic organisms (excluding fungi and allied taxa) parasitizing humans resulting in 274 genus-group taxa and 848 species-group taxa. For each species, or genus where indicated, a concise summary of geographic distribution, natural hosts, route of transmission and site within human host, and vectored pathogens are presented. Ubiquitous, human-adapted species as well as very rare, incidental zoonotic organisms are discussed in this annotated checklist. We also provide a list of 79 excluded genera and species that have been previously reported as human parasites but are not believed to be true human parasites or represent misidentifications or taxonomic changes.

The prevalence of soil transmitted helminth infections in minority indigenous populations of South-East Asia and the Western Pacific Region: A systematic review and meta-analysis

INTRODUCTION

Soil transmitted helminth (STH) infections cause one of the most prevalent diseases in man. STHs disproportionately impact socio-economically disadvantaged communities including minority indigenous populations. This systematic review aimed to quantify the prevalence of STH infection within minority indigenous populations of the South-East Asia and Western Pacific Regions.

METHODS

The systematic review was conducted in accordance with The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines following a published protocol. A random effects meta-analysis was used to estimate the pooled prevalence of STH infection, and meta-regression analysis was used to quantify associations with study characteristics. Where comparative data were available, sub-group analysis was conducted to evaluate the risk of STH infection in minority indigenous people relative to other population groups. The heterogeneity between studies was evaluated visually using Forest plots and was assessed quantitatively by the index of heterogeneity (I2) and Cochran Q-statistics.

RESULTS

From 1,366 unique studies that were identified, 81 were included in the final analysis. The pooled prevalence of infection within minority indigenous populations was 61.4% (95% CI 50.8, 71.4) for overall STH infection; 32.3% (95% CI 25.7, 39.3) for Ascaris.lumbricoides; 43.6% (95% CI 32.6, 54.8) for Trichuris.trichiura; 19.9% (95% CI 15.7, 24.5) for hookworm and 6.3% (95% CI 3.2, 10.2) for Strongyloides.stercoralis. A significant increase in T. trichiura prevalence was observed over time. The stratified analysis showed that the prevalence of infection for STH overall and for each STH species were not significantly different in minority indigenous participants compared to other populations groups.

CONCLUSION

The prevalence of STH infection is high within minority indigenous populations across countries at very different levels of socio-economic development. The increasing prevalence of T. trichiura calls for the implementation of more effective therapies and control strategies.

Strongyloides genotyping: a review of methods and application in public health and population genetics

Strongyloidiasis represents a major medical and veterinary helminthic disease. Human infection is caused by Strongyloides stercoralis, Strongyloides fuelleborni fuelleborni and Strongyloides fuelleborni kellyi, with S.stercoralis accounting for the majority of cases. Strongyloides f. fuelleborni likely represents a zoonosis acquired from non-human primates (NHPs), while no animal reservoir for S. f. kellyi infection has been found. Whether S. stercoralis represents a zoonosis acquired from dogs and cats remains unanswered. Over the past two decades various tools have been applied to genotype Strongyloides spp. The most commonly sequenced markers have been the hyper-variable regions I and IV of the 18S rRNA gene and selected portions of the cytochrome c oxidase subunit I gene. These markers have been sequenced and compared in Strongyloides from multiple hosts and geographical regions. More recently, a machine learning algorithm multi-locus sequence typing approach has been applied using these markers, while others have applied whole genome sequencing. Genotyping of Strongyloides from dogs, cats, NHPs and humans has identified that S. stercoralis likely originated in dogs and adapted to human hosts. It has also been demonstrated that S. stercoralis is distinct from S. f. fuelleborni and S. f. kellyi. Two distinct genetic clades of S. stercoralis exist, one restricted to dogs and another infecting humans, NHPs, dogs and cats. Genotyping of S. f. fuelleborni has identified two separate clades, one associated with African isolates and another Indochinese peninsular clade. This review summarises the history and development of genotyping tools for Strongyloides spp. It describes the findings of major studies to date in the context of the epidemiology and evolutionary biology of these helminths, with a specific focus on human-infecting species.

Skin-penetrating nematodes exhibit life-stage-specific interactions with host-associated and environmental bacteria

Background

Skin-penetrating nematodes of the genus Strongyloides infect over 600 million people, posing a major global health burden. Their life cycle includes both a parasitic and free-living generation. During the parasitic generation, infective third-stage larvae (iL3s) actively engage in host seeking. During the free-living generation, the nematodes develop and reproduce on host feces. At different points during their life cycle, Strongyloides species encounter a wide variety of host-associated and environmental bacteria. However, the microbiome associated with Strongyloides species, and the behavioral and physiological interactions between Strongyloides species and bacteria, remain unclear.

Results

We first investigated the microbiome of the human parasite Strongyloides stercoralis using 16S-based amplicon sequencing. We found that S. stercoralis free-living adults have an associated microbiome consisting of specific fecal bacteria. We then investigated the behavioral responses of S. stercoralis and the closely related rat parasite Strongyloides ratti to an ecologically diverse panel of bacteria. We found that S. stercoralis and S. ratti showed similar responses to bacteria. The responses of both nematodes to bacteria varied dramatically across life stages: free-living adults were strongly attracted to most of the bacteria tested, while iL3s were attracted specifically to a narrow range of environmental bacteria. The behavioral responses to bacteria were dynamic, consisting of distinct short- and long-term behaviors. Finally, a comparison of the growth and reproduction of S. stercoralis free-living adults on different bacteria revealed that the bacterium Proteus mirabilis inhibits S. stercoralis egg hatching, and thereby greatly decreases parasite viability.

Conclusions

Skin-penetrating nematodes encounter bacteria from various ecological niches throughout their life cycle. Our results demonstrate that bacteria function as key chemosensory cues for directing parasite movement in a life-stage-specific manner. Some bacterial genera may form essential associations with the nematodes, while others are detrimental and serve as a potential source of novel nematicides.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01153-7.

Endemic parasitic infections in donors and recipients of stem cell and solid organ transplants: focus on strongyloidiasis and Chagas disease

PURPOSE OF REVIEW

The aim of the article is to review recent recommendations on the management of Strongyloidiasis and Chagas disease (ChD) in the context of stem-cell or solid-organ transplantation.

RECENT FINDINGS

An update on laboratory screening, detection of acute disease or reactivation and recommended preventive or therapeutic options in the transplant recipients and donors is presented. Recent epidemiological data showing new estimates on the worldwide burden of both diseases and changes in the classical distribution around the globe should increase awareness and will impact the evaluation and management of transplant recipients and donors in endemic and nonendemic regions.

SUMMARY

Strongyloidiasis and ChD are potentially life threatening if unnoticed in the context of stem-cell or solid-organ transplantation and should be considered in endemic and nonendemic areas. Effective strategies for detection, monitoring, prevention and management are available for both diseases.

Intestinal parasites among intellectually disabled individuals in Iran: a systematic review and meta-analysis

BACKGROUND

Poor self-care skills and personal hygiene resulted from limitations in learning and understanding, put intellectually disabled individuals at greater risk for intestinal parasitic infections (IPIs). Despite several regional reports in Iran, the overall burden on IPIs among intellectually disabled individuals is poorly understood. Hence, the present study aimed to estimate the pooled prevalence of IPIs among intellectually disabled individuals in Iran.

METHODS

Using the PRISMA guidelines, we conducted a systematic review and meta-analysis of data retrieved from seven electronic databases (PubMed, Web of Science, Scopus, Embase, and ProQuest for English articles, as well as SID and Magiran for Persian) from their inception up to December 2020. Pooled prevalence was estimated using a random-effects model with a 95% confidence interval (CI) and depicted as a forest plot, while heterogeneity was evaluated using Cochran's Q-test.

RESULTS

Exactly 1263 of the 3004 intellectually disabled individuals examined by 14 studies across 10 provinces of Iran were positive for IPIs. Overall pooled prevalence estimate was 41% (95% CI 29-53%) with a range of 21% (95% CI 10-32%) to 68% (95% CI 55-80%) across sub-groups. Entamoeba coli (16.2%; 95% CI 10.3-22%), Blastocystis spp. (12.2%; 95% CI 7.2-17.2%), and Giardia duodenalis (11.9%; 95% CI 7.4-16.3%) were the most prevalent protozoan species. In terms of helminthic agents, the most prevalent species were Enterobius vermicularis (11.3%; 95% CI 6.3-16.3%) followed by Strongyloides stercoralis (10.9%; 95% CI 5.0-16.9%) and Hymenolepis nana (2.8%; 95% CI 0.4-5.2%) CONCLUSION: IPIs are highly prevalent among intellectually disabled individuals in Iran. Improving the health status and implementing infectious disease prevention strategies in rehabilitation centers, health promotion interventions to improve personal hygiene of intellectually disabled individuals, as well as utilize sensitive diagnostic methods besides routine stool examination techniques, and treatment of infected individuals will help in the control of these infections among intellectually disabled individuals.

Soil-Transmitted Helminths in the USA: a Review of Five Common Parasites and Future Directions for Avenues of Enhanced Epidemiologic Inquiry

Purpose of Review

The aim of this review is to present a comprehensive look at five intestinal soil-transmitted helminths (STHs) of global health importance that may continue to plague low-income and rural areas of the USA and argue the need for enhanced surveillance of these infections, which primarily affect the nation’s most vulnerable groups.

Recent Findings

Human STH infections in middle- and high-income countries are at particular risk for being undiagnosed; as common symptoms are non-specific, differentials require a high index of clinical suspicion, and cases are concentrated in areas of poverty where access to care is limited. Although autochthonous STHs are thought to be rare in the USA, infections were once common in the American South and Appalachia and robust epidemiologic surveillance is limited post 1980s. However, recent community studies and case reports from small-scale farms and areas of high rural or inner-city poverty reveal the potential for persisting helminth infections in distinct populations of the country.

Summary

STHs are among the most common neglected tropical diseases globally causing significant morbidity in underserved communities and contributing to the continuation of cycles of poverty within vulnerable populations. Due to possible severe disease sequalae and their ability to perpetuate poverty and poverty-associated health outcomes within already vulnerable groups, it is vital that surveillance for these infections is enhanced to bolster health equity in the USA.

Assessment of the prevalence of intestinal parasitic infections and associated habit and culture-related risk factors among primary schoolchildren in Debre Berhan town, Northeast Ethiopia

Background

Intestinal parasitic infections (IPIs) are still among the major public health issues in developing countries. Assessing the prevalence of IPIs and potential risk factors in different localities is essential to enhance control strategies. To date, no prevalence assessment study was conducted in Debre Berhan town. Therefore, the aim of this study was to assess the prevalence of IPIs and associated habit and culture-related risk factors among primary schoolchildren in Debre Berhan town, Northeast Ethiopia.

Method

School based cross-sectional study was conducted from April to June 2017. A total of 645 children aged 6–15 years were selected from six primary schools in Debre Berhan town via a multistage random sampling technique. A structured questionnaire was used to collect data about sociodemographic and potential risk factor variables. Fresh stool samples were collected from each child and examined using direct smear and formal-ether concentration technique.

Result

Among the 645 children participated in the study, 341 (52.9%) were infected by one or more intestinal parasites. Helminths (33.8%) were more prevalent than protozoa (20%). Double parasitic infection rate was 0.9%. The predominant parasites were Ascaris lumbricoides (22.6%), Entamoeba histolytica/dispar/moshkovskii (18.1%) and Hymenolepis nana (5.7%). Multivariable logistic regression analysis showed that age of child (6–9 years), family size (above 5), mother’s illiteracy and primary education, father’s illiteracy, urban-farmer father, manual-worker father, not washing hands before eating, unclean fingers, open defecation site (ODS) near residence, latrine type, cultural response to dropped food (cleaning and eating; ‘kiss and replace’), habit of playing with waste water, habit of playing with soil, habit of sucking fingers and habit of eating when playing were significantly associated with IPIs (p< 0.05). Likewise, age (6–9 years), mother’s illiteracy, urban-farmer father, not washing hands before eating, ODS near residence, tradition of cleaning and eating dropped food, habit of playing with soil, sucking fingers and eating when playing were identified as significant risk factors of A. lumbricoides infection.

Conclusion

High prevalence of IPIs among the study participants demands improvement of environmental sanitation, personal hygiene, and health education regarding the potential habit and culture-related risk factors.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-020-10148-y.

HTLV-I and Strongyloides in Australia: The worm lurking beneath

Strongyloidiasis and HTLV-I (human T-lymphotropic virus-1) are important infections that are endemic in many countries around the world with an estimated 370 million infected with Strongyloides stercoralis alone, and 5-10 million with HTVL-I. Co-infections with these pathogens are associated with significant morbidity and can be fatal. HTLV-I infects T-cells thus causing dysregulation of the immune system which has been linked to dissemination and hyperinfection of S. stercoralis leading to bacterial sepsis which can result in death. Both of these pathogens are endemic in Australia primarily in remote communities in Queensland, the Northern Territory, and Western Australia. Other cases in Australia have occurred in immigrants and refugees, returned travellers, and Australian Defence Force personnel. HTLV-I infection is lifelong with no known cure. Strongyloidiasis is a long-term chronic disease that can remain latent for decades, as shown by infections diagnosed in prisoners of war from World War II and the Vietnam War testing positive decades after they returned from these conflicts. This review aims to shed light on concomitant infections of HTLV-I with S. stercoralis primarily in Australia but in the global context as well.

Prevalence, risk factors and health consequences of soil-transmitted helminth infection on the Bijagos Islands, Guinea Bissau: A community-wide cross-sectional study

Soil-transmitted helminths (STH) are endemic and widespread across Sub-Saharan Africa. A community wide soil-transmitted helminth (STH) prevalence survey was performed on the island of Bubaque in Guinea-Bissau using both Kato-katz microscopy and qPCR methodology. Predictors of infection and morbidity indicators were identified using multivariable logistic regression, and diagnostic methods were compared using k statistics. Among 396 participants, prevalence of STH by microscopy was 23.2%, hookworm was the only species identified by this method and the mean infection intensity was 312 eggs per gram. qPCR analysis revealed an overall prevalence of any STH infection of 47.3%, with the majority A. duodenale (32.3%), followed by N. americanus (15.01%) and S. stercoralis (13.2%). A. lumbricoides, and T. trichiura infections were negligible, with a prevalence of 0.25% each. Agreement between diagnostic tests was k = 0.22, interpreted as fair agreement, and infection intensity measured by both methods was only minimally correlated (Rs = -0.03). STH infection overall was more common in females and adults aged 31-40. STH infection was associated with open defaecation, low socio-economic status and further distance to a water-source. The prevalence of anaemia (defined as a binary outcome by the WHO standards for age and sex) was 69.1%, and 44.2% of children were malnourished according to WHO child growth standards. Hookworm infection intensity by faecal egg count showed no statistically significant association with age (Rs 0.06) but S. Stercoralis infection intensity by qPCR cycle threshold was higher in pre-school aged children (Rs = 0.30, p-value 0.03) There was no statistically significant association between STH infection and anaemia (OR 1.0 p = 0.8), stunting (OR 1.9, p-value 0.5) and wasting (OR 2.0, p-value 0.2) in children. This study reveals a persistent reservoir of STH infection across the community, with high rates of anaemia and malnutrition, despite high-coverage of mebendazole mass-drug administration in pre-school children. This reflects the need for a new strategy to soil-transmitted helminth control, to reduce infections and ultimately eliminate transmission.