Strongyloidiasis with emphasis on human infections and its different clinical forms

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 infection screening in transplant candidates: What is the best strategy?

BACKGROUND

The potential that Strongyloides stercoralis infection has to cause major morbidity and high mortality when the disseminated form occurs in transplant patients is of particular concern.

METHODS

In this study, the objective was to observe S. stercoralis infection in patients who are candidates for transplantation by using parasitological, serological, and molecular techniques and to propose an algorithm for the detection of that infection in transplant candidates.

RESULTS

By parasitological techniques, 10% of fecal samples were positive. Anti-Strongyloides antibodies immunoglobulin G were detected in 19.3% and 20.7% of patients by immunofluorescence assay and enzyme-linked immunosorbent assay, respectively. S. stercoralis DNA was observed in 17.3% of samples by conventional polymerase chain reaction and 32.7% of samples by quantitative polymerase chain reaction (qPCR).

CONCLUSION

The set of results allows us to reinforce that a positive result by parasitological techniques and/or qPCR indicates that the specific treatment should be applied. However, the improvement of diagnostic techniques may suggest changes in the screening for strongyloidiasis in these patients.

The Th2 Response and Alternative Activation of Macrophages Triggered by Strongyloides venezuelensis Is Linked to Increased Morbidity and Mortality Due to Cryptococcosis in Mice

Cryptococcosis is a systemic mycosis that causes pneumonia and meningoencephalitis. Strongyloidiasis is a chronic gastrointestinal infection caused by parasites of the genus Strongyloides. Cryptococcosis and strongyloidiasis affect the lungs and are more prevalent in the same world regions, i.e., Africa and tropical countries such as Brazil. It is undeniable that those coincidences may lead to the occurrence of coinfections. However, there are no studies focused on the interaction between Cryptococcus spp. and Strongyloides spp. In this work, we aimed to investigate the interaction between Strongyloides venezuelensis (Sv) and Cryptococcus gattii (Cg) in a murine coinfection model. Murine macrophage exposure to Sv antigens reduced their ability to engulf Cg and produce reactive oxygen species, increasing the ability of fungal growth intracellularly. We then infected mice with both pathogens. Sv infection skewed the host's response to fungal infection, increasing lethality in a murine coinfection model. In addition to increased NO levels and arginase activity, coinfected mice presented a classic Th2 anti-Sv response: eosinophilia, higher levels of alternate activated macrophages (M2), increased concentrations of CCL24 and IL-4, and lower levels of IL-1β. This milieu favored fungal growth in the lungs with prominent translocation to the brain, increasing the host's tissue damage. In conclusion, our data shows that primary Sv infection promotes Th2 bias of the pulmonary response to Cg-infection and worsens its pathological outcomes.

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.

A case of strongyloidiasis with aplastic anaemia: A common disease with an uncommon presentation

Strongyloidiasis is an opportunistic infection caused by the nematode helminth Strongyloides stercoralis and transmitted mostly via soil. The disease is usually asymptomatic, limited, and long-standing. Herein, we report a case of strongyloidiasis in a patient who seemed to be immunocompetent despite his malnourished appearance. He was presented with pancytopenia and aplastic anaemia and well responded to albendazole therapy with complete resolution of symptoms within three months. We recommend, prior to beginning of immunosuppressive regimens, it may be prudent to examine all patients presenting with abdominal discomfort along with pancytopenia for a possible worm infestation. Bone marrow suppression induced by worm infestation is an extremely rare but potentially comorbid condition that can lead to pancytopenia and severe aplastic anaemia.

Intestinal parasite infections associated with sociodemographic and seasonal factors in the Western Amazon

Intestinal parasites are a constant public health problem in the Amazon region, with a high prevalence of cases related to poor sanitary conditions. We investigated the sociodemographic and seasonal factors associated with human intestinal parasite infections in an area of the Western Amazon, Brazil, from September 2017 to August 2019. Data were collected using a database available at the Diagnostic Support Centre (Centro de Apoio ao Diagnóstico, CAD) of the Municipality of Rio Branco, on positive diagnoses for intestinal parasites. Among the 53,200 samples analysed, 18.3% (n = 9712) were positive. Of these, 96.4% (n = 9363) and 3.6% (n = 349) were protozoan and helminthic infections, respectively. Males showed higher odds ratio (OR) for Enterobius vermicularis infection (OR: 2.3) and giardiasis (OR: 1.9) and lower OR for Endolimax nana (OR: 0.9) and Entamoeba coli (OR: 0.9) infections. Individuals aged ≥ 15 presented higher OR for Strongyloides stercoralis (OR: 3.4), hookworms (OR: 2.3), and almost all protozoan infections than younger individuals. In the dry season, the OR for hookworms (OR: 1.5), Iodamoeba butschlii (OR: 1.4), and Endolimax nana (OR: 1.3) infections was higher than that in the rainy season, including a high chance of polyparasitism (OR: 1.6). We concluded that there was a significant difference between the different types of intestinal parasites, particularly protozoa, with high OR in the dry season and for certain groups.

Fatal Case of Autochthonous Strongyloides stercoralis Hyperinfection in an Immunosuppressed Calabrian Patient

Strongyloides stercoralis is an intestinal nematode that can induce disseminated infection in immunocompromised patients. It is most commonly acquired in tropical and subtropical countries; however, foci of the infection have also been reported in temperate geographic areas. In non-endemic areas, the diagnosis of an S. stercoralis infection is challenging due to the variety of clinical symptoms. Herein, we report the case of a patient, born and raised in the Calabria region of Southern Italy, who presented with melanoma and S. stercoralis hyperinfection, which is characterized by dyspnea, productive cough, inappetence, marked asthenia, weight loss, and Klebsiella pneumoniae bacteremia. He worked as a farmer and never traveled to another country known to be endemic for S. stercoralis. Despite the prompt identification of the parasite with sputum microscopy and the initiation of therapy with ivermectin and piperacillin–tazobactam, the patient later died. This case underscores the continued risk for S. stercoralis infection even in geographic areas that were previously considered non-endemic for the nematode and indicates that the geographic distribution of S. stercoralis may be expanding in Italy.

A Rare Presentation of Strongyloides stercoralis Infection from an Immunocompetent Individual in a Tertiary Care Center in South India

Strongyloidiasis is a neglected parasitic disease caused by the intestinal parasite, Strongyloides stercoralis. Most patients with strongyloidiasis are asymptomatic, but few present with varied clinical manifestations such as cutaneous, gastrointestinal, pulmonary, and disseminated disease. It creates a diagnostic dilemma and undue delay in the diagnosis of patients. We report the case of a 79-year-old male who presented with fever and abdominal pain due to strongyloidiasis with no history of immunosuppression. The infection resolved entirely on treatment with ivermectin.

Is Strongyloides stercoralis hyperinfection induced by glucocorticoids a result of both suppressed host immunity and altered parasite genetics?

The gastrointestinal (GI) nematode Strongyloides stercoralis (S.s.) causes human strongyloidiasis, a potentially life-threatening disease that currently affects over 600 million people globally. The uniquely pernicious aspect of S.s. infection, as compared to all other GI nematodes, is its autoinfective larval stage (L3a) that maintains a low-grade chronic infection, allowing undetectable persistence for decades. Infected individuals who are administered glucocorticoid therapy can develop a rapid and often lethal hyperinfection syndrome within days. Hyperinfection patients often present with dramatic increases in first- and second-stage larvae and L3a in their GI tract, with L3a widely disseminating throughout host organs leading to sepsis. How glucocorticoid administration drives hyperinfection remains a critical unanswered question; specifically, it is unknown whether these steroids promote hyperinfection through eliminating essential host protective mechanisms and/or through dysregulating parasite development. This current deficiency in understanding is largely due to the previous absence of a genetically defined mouse model that would support all S.s. life-cycle stages and the lack of successful approaches for S.s. genetic manipulation. However, there are currently new possibilities through the recent demonstration that immunodeficient NOD.Cg-Prkdc^scidIl2rg^tm1Wjl/SzJ (NSG) mice support sub-clinical infections that can be transformed to lethal hyperinfection syndrome following glucocorticoid administration. This is coupled with advances in transcriptomics, transgenesis, and gene inactivation strategies that now allow rigorous scientific inquiry into S.s. biology. We propose that combining in vivo manipulation of host immunity and deep immunoprofiling strategies with the latest advances in S.s. transcriptomics, piggyBac transposon-mediated transgene insertion, and CRISPR/Cas-9-mediated gene inactivation will facilitate new insights into the mechanisms that could be targeted to block lethality in humans with S.s. hyperinfection.

Seroprevalence of Strongyloides stercoralis infection in a South Indian adult population

Background

The prevalence of Strongyloides stercoralis infection is estimated to be 30–100 million worldwide, although this an underestimate. Most cases remain undiagnosed due to the asymptomatic nature of the infection. We wanted to estimate the seroprevalence of S. stercoralis infection in a South Indian adult population.

Methods

To this end, we performed community-based screening of 2351 individuals (aged 18–65) in Kanchipuram District of Tamil Nadu between 2013 and 2020. Serological testing for S. stercoralis was performed using the NIE ELISA.

Results

Our data shows a seroprevalence of 33% (768/2351) for S. stercoralis infection which had a higher prevalence among males 36% (386/1069) than among females 29.8% (382/1282). Adults aged ≥55 (aOR = 1.65, 95% CI: 1.25–2.18) showed higher adjusted odds of association compared with other age groups. Eosinophil levels (39%) (aOR = 1.43, 95% CI: 1.19–1.74) and hemoglobin levels (24%) (aOR = 1.25, 95% CI: 1.11–1.53) were significantly associated with S. stercoralis infection. In contrast, low BMI (aOR = 1.15, 95% CI: 0.82–1.61) or the presence of diabetes mellitus (OR = 1.18, 95% CI: 0.83–1.69) was not associated with S. stercoralis seropositivity.

Conclusions

Our study provides evidence for a very high baseline prevalence of S. stercoralis infection in South Indian communities and this information could provide realistic and concrete planning of control measures.

Strongyloides stercoralis in a dog litter: Evidence suggesting a transmammary transmission

Strongyloides stercoralis is a soil-transmitted helminth with an unusual life cycle, causing canine and human strongyloidiasis, mainly endemic in tropical and subtropical areas. Following percutaneous or oral transmission of infective third-stage larvae in the vertebrate host, the parasite can cause autoinfection, leading to life-long infection. At present, the transmammary transmission was only assessed in experimentally infested dogs. Here, we provide observational evidence of S. stercoralis transmammary transmission in puppies suckling from a truffle dog from Central Italy, from where its presence was neglected.

Strongyloides hyperinfection in a patient from Venezuela with lower gastrointestinal bleeding

We herein present a case of unsuspected Strongyloides stercoralis (Ss) hyperinfection diagnosis. No screening due to origin or immunosuppressed condition had been done and treatment was presumably prescribed lately, with subsequent vital risk for the patient.

Importance of detection of Strongyloides stercoralis DNA in fecal samples from patients with type 2 diabetes mellitus

OBJECTIVE

The association between diabetes and Strongyloides infection remains controversial. This study aimed to detect Strongyloides stercoralis DNA in the feces of patients with Diabetes Mellitus type 2 (DM2).

METHODS

Fecal samples were analyzed via the Lutz, Rugai, and agar plate culture methods. PCR amplification was performed using two targets (PCR-genus and PCR-species) located on the S. stercoralis 18S ribosomal.

RESULTS

The positivity for S. stercoralis using parasitological methods was 1.1%. PCR-genus (14.13%) demonstrated a higher positivity than PCR-species (9.78%).

CONCLUSION

The results confirm the greater positivity of the molecular diagnosis in relation to parasitological methods, reinforcing its use as an additional tool for the diagnosis of S. stercoralis infection in patients with DM2 living in endemic areas for this helminthiasis.

Potentially zoonotic parasites in the soil of public squares in the city of Aracaju (Sergipe, Northeastern Brazil)

This study evaluated the soil contamination of public squares in the city of Aracaju, Sergipe, by potentially zoonotic parasites and correlated their occurrence with climatic variables (temperature, humidity and precipitation). Samples were collected over a 18-month period, from 20 different public squares, and submitted to three different parasitological techniques: Faust's, Hoffman's and Rugai's methods, adapted to soil samples. Results indicated the presence of several potentially zoonotic parasitic species in eighteen of the 20 squares analyzed (90%). The parasites identified included Ancylostoma spp., Strongyloides stercoralis, Toxocara spp., Dipylidium caninum, Trichuris sp., Capillaria sp. and Giardia sp. They were identified during all months of the year and no influence of temperature, humidity or precipitation on the occurrence of those parasites was observed. Such results demonstrate that public squares in the city of Aracaju pose a parasitic contamination risk for people and pets that visit those places as a leisure activity.

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.

Evaluation of targets for Strongyloides genus specific molecular diagnosis in experimental strongyloidiasis

Strongyloides venezuelensis has been used in different experimental studies, such as those aimed at the evaluation of diagnostic techniques for human strongyloidiasis, mainly the molecular diagnosis. In this study, three regions (genus, 18S and 28S targets) of Strongyloides ribosomal DNA were evaluated for the molecular diagnosis of experimental strongyloidiasis. Rats were infected subcutaneously with 400 or 4000 S. venezuelensis infective larvae (400iL3 and 4000iL3), and kept for 35 days. Fecal samples were collected daily to count eggs per gram of feces (EPG) and to perform the polymerase chain reaction (PCR). Egg count started on the 5th day post-infection (pi) and ended on days 33 and 34 pi, in 400iL3 and 4000iL3 groups, respectively. Based in EPG, fecal samples were selected from days 2, 5, 8, 11, 15, 23 and 35 pi for DNA extraction; PCR (genus, 18S and 28S); and sequencing. The PCR-28S products showed higher values of identity (95-100%) in the database with the Strongyloides sequences. Therefore, it is possible to reinforce the application of PCR-28S in the diagnosis of experimental and human strongyloidiasis.

Helminth Coinfection Is Associated With Enhanced Plasma Levels of Matrix Metalloproteinases and Tissue Inhibitor of Metalloproteinases in Tuberculous Lymphadenitis

Matrix metalloproteinases (MMPs) are crucial for tissue remodeling and repair and are expressed in diverse infections, whereas tissue inhibitors of metalloproteinases (TIMPs) are endogenous inhibitors of MMPs. However, the interaction of MMPs and TIMPs in tuberculous lymphadenitis (TBL), an extra-pulmonary form of tuberculosis (EPTB) and helminth (Hel+) coinfection is not known. Therefore, this present study investigates the levels of circulating MMPs (1, 2, 3, 7, 8, 9, 12, 13) and TIMPs (1, 2, 3, 4) in TBL individuals with helminth (Strongyloides stercoralis [Ss], hereafter Hel+) coinfection and without helminth coinfection (hereafter, Hel-). In addition, we have also carried out the regression analysis and calculated the MMP/TIMP ratios between the two study groups. We describe that the circulating levels of MMPs (except MMP-8 and MMP-12) were elevated in TBL-Hel+ coinfected individuals compared to TBL-Hel- individuals. Similarly, the systemic levels of TIMPs (1, 2, 3, 4) were increased in TBL-Hel+ compared to TBL-Hel- groups indicating that it is a feature of helminth coinfection per se. Finally, our multivariate analysis data also revealed that the changes in MMPs and TIMPs were independent of age, sex, and culture status between TBL-Hel+ and TBL-Hel- individuals. We show that the MMP-2 ratio with all TIMPs were significantly associated with TBL-helminth coinfection. Thus, our results describe how helminth infection has a profound effect on the pathogenesis of TBL and that both MMPs and TIMPs could dampen the immunity against the TBL-Hel+ coinfected individuals.

Analysis of Daily Variation for 3 and for 30 Days of Parasite-Specific IgG in Urine for Diagnosis of Strongyloidiasis by Enzyme-Linked Immunosorbent Assay

Recent work has found urine analysis to be as sensitive as serology for diagnosis of strongyloidiasis. Here, we examined the daily variation of Strongyloides-specific IgG in urine by qualitative and quantitative ELISA and its effects on diagnostic accuracy and reliability. In the first part of the study, matched urine and fecal samples were collected from project participants in northeast Thailand for three consecutive days. Urine samples were analyzed for Strongyloides-specific IgG by ELISA using Strongyloides ratti as the antigen source. Performance of urine ELISA was compared with parasitological diagnosis by agar plate culture technique (APCT) and formalin-ethyl acetate concentration technique (FECT). In the second part of the study, urine IgG levels were compared daily for thirty consecutive days. The prevalence of Strongyloides infection, as measured by urine ELISA for three consecutive days, was significantly higher than that found using parasitological methods (63.1% vs. 22%). There was slight daily variation in prevalence estimates according to urine ELISA while there were significant variations according to parasitological examination methods over three consecutive days. For the 3-day experiment, urine ELISA had 83-86% diagnostic sensitivity when compared with the fecal examination method or with a composite standard (combined results from fecal examination methods (APCT or FECT) and/or urine ELISA). The levels of parasite-specific IgG in urine were stable throughout both the 3-day and the 30-day studies. In conclusion, diagnosis of strongyloidiasis by urine ELISA is more sensitive than by fecal methods, with minimal daily variation for qualitative and quantitative diagnosis. Urine ELISA has potential for clinical diagnosis and population screening of strongyloidiasis.

Eosinophilic appendicitis due to Strongyloides stercoralis: a challenging differential diagnosis for clinicians

A 45-year-old man presents with 48-hour status of high temperature, cough and dyspnoea. In the context of pandemic, the patient is initially diagnosed with COVID-19 syndrome. Later, the laboratory and ultrasound study supported acute appendicitis diagnosis. Appendicectomy was performed. The histopathology study confirmed eosinophilic appendicitis and that a parasitic infection was suspected. The stool sample was positive for Strongyloides stercoralis The diagnosis of a S stercoralis is a rare finding in Spain. S. stercoralis simulates clinical findings of inflammatory bowel disease or eosinophilic gastroenteritis, which may lead to the wrong therapeutic choice. Since in inflammatory diseases corticosteroid treatments are considered the initial choice in many cases, in the case of S. stercoralis infection, the administration of this therapy can be fatal. In Spain, the number of diagnoses is much lower than in the past decade, although it is highly probable that the infection has been underdiagnosed due to low clinical awareness among Spanish population.

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.

Design, Expression and Purification of Strongyloides stercoralis IgG4 Immunoreactive Protein (NIE) in Escherichia coli

Background

Strongyloidiasis is a public health concern in northern regions of Iran, caused by Strongyloides stercoralis. Auto-infection cycle can be resulted in high parasitic load, especially in immunocompromised hosts. Because of low sensitivity of stool culture and stool-based microscopy techniques, detection of antibodies in patient's sera can be an alternative diagnostic technique for detection of the nematode. In the present study, as the first step of the development of an ELISA kit for the detection of antibodies against the nematode, IgG4 immunoreactive protein (NIE) was expressed in Escherichia coli expression system, purified and verified.

Methods

The NIE gene sequence was retrieved from the GenBank. This sequence was codon-optimized for the expression in E. coli BL21 (DE3). The sequence was inserted into the expression vector pET-30b (+). The recombinant vector was then transferred into competent E. coli BL21 (DE3). Transformed colonies were selected and verified by colony PCR. NIE gene expression was induced with IPTG induction. The protein production was evaluated by SDS-PAGE and verified using Western blotting.

Results

The codon-optimized NIE gene had required parameters for expression in E. coli. NIE protein was proved and verified by SDS-PAGE and Western blotting.

Conclusion

NIE recombinant protein was successfully expressed in E. coli expression system in appropriate amounts. The recombinant protein can be used for developing ELISA kit in diagnosis of S. stercoralis.

Regulatory T cell expansion resolves after effective strongyloidiasis treatment in subjects with HTLV-1 co-infection

BACKGROUND

Regulatory T-cells (Tregs) are increased in patients with HTLV-1/Strongyloides stercoralis co-infection, and they may modify otherwise protective antigen-specific cytokine production. We hypothesized that effective anti-helminthic treatment would decrease Tregs and restore antigen-specific cytokine responses.

METHODS/RESULTS

We enrolled 19 patients with Strongyloides larvae in their stool by Baerman's test. Six were positive and 13 negative for antibody to HTLV-1 by ELISA, with positive tests confirmed by immunoblot. Before treatment, co-infected subjects had higher Tregs percentages and lower antigen-stimulated IL-5 levels compared to subjects with Strongyloides without HTLV-1. All patients were treated with ivermectin. After effective treatment, Tregs percentages decreased in patients with HTLV-1; however, antigen-specific IL-5 production remained blunted in co-infected subjects.

CONCLUSION

These results suggest that treating strongyloidiasis infection decreases circulating Tregs, but antigen-specific cytokine remains altered. This may reflect blunting of sensitization by Tregs.

Strong-LAMP Assay Based on a Strongyloides spp.-Derived Partial Sequence in the 18S rRNA as Potential Biomarker for Strongyloidiasis Diagnosis in Human Urine Samples

Human strongyloidiasis a soil-transmitted infection caused by Strongyloides stercoralis is one of the most neglected amongst the so-called Neglected Tropical Diseases (NTDs). S. stercoralis is a nematode, which is distributed worldwide; it has been estimated that it could affect millions of people, mainly in tropical and subtropical endemic regions. The difficulties of diagnosis lead to infection rates being underreported. Asymptomatic patients have chronic infections that can lead to severe hyperinfection syndrome or disseminated strongyloidiasis in immunocompromised patients. Strongyloidiasis can easily be misdiagnosed because conventional faecal-based techniques lack of sensitivity for the morphological identification of infective larvae in faeces. None of the currently used molecular methods have used urine samples as an alternative to faecal samples for diagnosing strongyloidiasis. This study was thus aimed at comparing, for the first time, the use of a new loop-mediated isothermal amplification (LAMP) molecular assay (Strong-LAMP) to traditional methods on patients' urine samples. Twenty-four urine samples were taken from patients included in a study involving two Spanish hospitals for strongyloidiasis screening using parasitological and serological tests. Strongyloides larvae were found in 11 patients' faecal samples, thereby ascertaining that they had the disease. Other patients had high antibody titres but no larvae were found in their faeces. All urine samples were analysed by PCR and Strong-LAMP assay. No amplification occurred when using PCR. Strong-LAMP led to detecting S. stercoralis DNA in urine samples from patients having previously confirmed strongyloidiasis by parasitological tests and/or a suspicion of being infected by serological ones. The Strong-LAMP assay is a useful molecular tool for research regarding strongyloidiasis in human urine samples. After further validation, the Strong-LAMP assay could also be used for complementary and effective diagnosis of strongyloidiasis in a clinical setting.

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.

Strongyloides stercoralis Hyper infection Syndrome

Strongyloides stercoralis is a helminth, widely distributed in tropical and subtropical countries. Its infestation in humans usually does not produce symptoms. However, in some patients, severe and life-threatening forms of this infection can occur, especially in immunocompromised individuals. Severe parasitic infection is triggered by any imbalance in the host’s immunity favouring the auto-infective cycle. This results in an increase in the intraluminal parasitic burden. In addition, tissue infestation is also very common. Clinical presentation is variable, and it is very difficult to diagnose clinically. Diagnosis requires a high index of suspicion. In some cases, the diagnosis is established only on histopathological examination of the excised tissue by the pathologist. Here, the authors report a case of an elderly male diabetic patient, who presented to the emergency department with the features of acute abdomen. On exploratory laparotomy, he was found to have the features suggestive of gangrene of small bowel. Resection of the gangrenous bowel was done, and end-to-end anastomosis was done as the rest of the bowel appeared to be normal. However, the patient died of multi-organ failure and septicaemia on the second postoperative day. The resected intestine showed tissue infestation of Strongyloides stercoralis on histopathological examination. In this review article, the authors summarize a case of hyper infection syndrome of strongyloidiasis and discuss the various aspects of Strongyloides stercoralis infection with emphasis on life cycle of the parasite and different clinical features of the disease.

Parasitological and immunological aspects of oral and subcutaneous prednisolone treatment in rats experimentally infected with Strongyloides venezuelensis

Strongyloides venezuelensis is a model to study human strongyloidiasis, which infects wild rodents and shares common antigenic epitopes with Strongyloides stercoralis. This study aimed to evaluate parasitological and immunological parameters of prednisolone immunosuppression protocols in rats (Rattus novergicus) infected with S. venezuelensis. Rats were divided into six groups (n = 36): untreated and uninfected (-) or infected (+); oral treatment and uninfected (o-) or infected (o+); subcutaneous treatment and uninfected (sc-) or infected (sc+). For oral immunosuppression, 5 mg/mL of water diluted prednisolone were given five days before infection, and in the days 8 and 21 (for 5 days). For subcutaneous immunosuppression, 10 mg/kg of prednisolone were given daily. The infection was established by the subcutaneous injection of approximately 3,000 S. venezuelensis filarioid larvae per animal. All animals from the (+) and (o+) groups survived, while four rats from the (sc+) died prior to necropsy date. Parasitological analysis showed higher egg elimination in (o+) in comparison to (+) and (sc+) on 7, 13 and 26 days post infection (d.p.i.).The recovery of parasitic females at day 30 was significantly higher in (o+), compared to (+). The (+) and (o+) groups showed a clear increase in anti-S. venezuelensis IgG, IgG1 and IgG2 from 13th d.p.i. Oral immunosuppression led to a higher number of adult females and increased egg output while maintaining IgG and subclasses antibody levels comparable to the positive control.

Safety of high-dose ivermectin: a systematic review and meta-analysis

BACKGROUND

Ivermectin is a key anthelmintic for the control of neglected tropical diseases. The main indications for population-level control with ivermectin through mass drug administration are onchocerciasis and lymphatic filariasis; however, there is interest in using higher, fixed-dose regimens for the control of scabies, soil-transmitted helminths and malaria. Safety data for these higher-dose regimens are needed.

METHODS

A systematic literature review and meta-analysis on the safety and doses of ivermectin was conducted. Eligible studies reported patient-level data and, for the meta-analysis, clinical trials reporting data on doses ≥200 and ≥400 μg/kg were included. Incidence ratios were used to compare adverse events by severity and organ system affected.

RESULTS

The systematic search identified six studies for inclusion, revealing no differences in the number of individuals experiencing adverse events. A descriptive analysis of these clinical trials for a variety of indications showed no difference in the severity of the adverse events between standard (up to 400 μg/kg) and higher doses of ivermectin. Organ system involvement only showed an increase in ocular events in the higher-dose group in one trial for the treatment of onchocerciasis, all of them transient and mild to moderate in intensity.

CONCLUSIONS

Although within this review the safety of high-dose ivermectin appears to be comparable to standard doses, there are not enough data to support a recommendation for its use in higher-than-approved doses. Ocular adverse events, despite being transient, are of concern in onchocerciasis patients. These data can inform programme managers and guide operational research activities as new approaches for the use of ivermectin are evaluated.

Shotgun proteomics of Strongyloides venezuelensis infective third stage larvae: Insights into host-parasite interaction and novel targets for diagnostics

Strongyloides venezuelensis is an important alternative source of antigen for the serologic diagnosis of human strongyloidiasis. Proteomics techniques applied to the analysis of the protein content of infective third stage larvae (iL3) of S. venezuelensis provide a powerful tool for the discovery of new candidates for immunodiagnosis. This study presents an overview of the protein iL3 S. venezuelensis focusing on the diagnosis of strongyloidiasis. A total of 877 proteins were identified by shotgun proteomics. Many of these proteins are involved in different cellular processes, metabolic as well as structural maintenance. Our results point to a catalog of possible diagnostic targets for human strongyloidiasis and highlight the need for evaluation of uncharacterized proteins, especially the proteins within the CAP domain, transthyretin, and BTPI inhibitor domains, as a repertoire as yet unexplored in the context of strongyloidiasis diagnostic markers. We believe that the protein profile presented in this shotgun analysis extends our understanding of the protein composition within the Strongyloides genus, opening up new perspectives for research on biomarkers that may help with the diagnosis of human strongyloidiasis. Data are available via ProteomeXchange with identifier PXD013703.

Strongyloidiasis: A Neglected Tropical Disease

Most of the 30 to 100 million people infected with Strongyloides stercoralis have subclinical (or asymptomatic) infections. These infections are commonly chronic and longstanding. A change in immune status can increase parasite numbers, leading to hyperinfection syndrome, dissemination, and death if unrecognized. The use of corticosteroids and HTLV-1 infection are most commonly associated with the hyperinfection syndrome. Strongyloides adult parasites reside in the small intestine and induce immune responses that are like other nematodes. Definitive diagnosis of S stercoralis infection is based on stool examinations for larvae. S stercoralis remains largely neglected.

The Anthelmintic Effect on Strongyloides venezuelensis Induced by BnSP- 6, a Lys49-phospholipase A2 Homologue from Bothrops pauloensis Venom

Background:

Phospholipases A2 (PLA2) from snake venoms have a broad potential as pharmacological tools on medicine. In this context, strongyloidiasis is a neglected parasitic disease caused by helminths of the genus Strongyloides. Currently, ivermectin is the drug of choice for treatment, however, besides its notable toxicity, therapeutic failures and cases of drug resistance have been reported. BnSP-6, from Bothorps pauloensis snake venom, is a PLA2 with depth biochemical characterization, reporting effects against tumor cells and bacteria.

Objective:

The aim of this study is to demonstrate for the first time the action of the PLA2 on Strongyloides venezuelensis.

Methods:

After 72 hours of treatment with BnSP-6 mortality of the infective larvae was assessed by motility assay. Cell and parasite viability was evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Furthermore, autophagic vacuoles were labeled with Monodansylcadaverine (MDC) and nuclei of apoptotic cells were labeled with Propidium Iodide (PI). Tissue degeneration of the parasite was highlighted by Transmission Electron Microscopy (TEM).

Results:

The mortality index demonstrated that BnSP-6 abolishes the motility of the parasite. In addition, the MTT assay attested the cytotoxicity of BnSP-6 at lower concentrations when compared with ivermectin, while autophagic and apoptosis processes were confirmed. Moreover, the anthelmintic effect was demonstrated by tissue degeneration observed by TEM. Furthermore, we report that BnSP-6 showed low cytotoxicity on human intestinal cells (Caco-2).

Conclusion:

Altogether, our results shed light on the potential of BNSP-6 as an anthelmintic agent, which can lead to further investigations as a tool for pharmaceutical discoveries.

Strongyloides stercoralis larvae or egg: Which came first?

Strongyloides stercoralis (SS) hyperinfection is a well-documented condition. However, SS eggs in stool samples are not commonly observed during routine analysis. Here, we report a case on SS hyperinfection where both larvae and eggs were observed in the stool sample of an immunossupressed liver allograft transplanted patient.

Regulatory T cells and IgE expression in duodenal mucosa of Strongyloides stercoralis and human T lymphotropic virus type 1 co-infected patients

Background

Strongyloides stercoralis is an intestinal nematode unique in its ability to replicate in the human host, allowing ongoing cycles of autoinfection, persisting for decades within the same host. Although usually asymptomatic, overwhelming infections can occur in Strongyloides and HTLV-1 co-infected individuals (SS/HTLV-1). Regulatory T cells (Tregs) are able to blunt specific Th2 responses necessary to control the parasite. We previously reported that peripheral blood Tregs are increased in SS/HTLV-1 and correlate with low Th2 responses. We hypothesized that Tregs are also increased at the site of infection in duodenal mucosa.

Methods

Paraffin embedded duodenal biopsies were obtained from 10 SS/HTLV-1 patients, 3 controls with non-parasitic chronic duodenitis, and 2 healthy controls. Immunohistochemistry was performed using monoclonal antibodies against human CD3, CD8, IgE and FoxP3. The number of cells were counted using a conventional light microscope. The number of CD3+, CD8+, FoxP3+ and IgE positive cells per 0.35 mm² was measured using ImagePro Plus software comparing areas adjacent or distant from parasite material.

Results

In patients with SS/HTLV-1, T lymphocyte counts and CD8+ cells were lower in areas adjacent to the parasite compared to non-adjacent areas (CD3+: adjacent: 6.5 [Interquartile range (IQR: 2.8–12.3)]; non-adjacent: 24.5 [IQR: 20.9–34.4]; Mann-Whitney p = 0.0003; CD8+: adjacent: 4.5 [IQR: 2.3–11.8]; non-adjacent: 21 [IQR: 15.3–42.9]; Mann-Whitney p = 0.0011). Tregs cells in the intestines (FoxP3+ expressing cells) were increased in patients with SS/HTLV-1 compared with patients with chronic duodenitis (SS/HTLV-1: 1.5 [IQR: 0.7–2.3]; duodenitis controls: 0 [range 0–0.7]; healthy controls: 0; Mann-Whitney p = 0.034). There was also a trend towards fewer eosinophils adjacent to the parasites. Among SS/HTLV-1 patients the number of IgE expressing cells was increased for in areas not adjacent to the parasite compared to non-adjacent areas (ANOVA, p = 0.001).

Conclusions

Our data shows increased Treg cell numbers localized adjacent to the parasites in the duodenum SS/HTLV-1 patients. In addition, other T lymphocytes and IgE expressing cells were decreased adjacent to the parasites, suggesting an important role for Tregs in down-regulating local parasite effector responses.

Strongyloidiasis is a parasitic infection found worldwide in warm, moist climates. In most people, Strongyloides causes a mild and chronic infection with few symptoms. However, some patients, including those infected with the Human T Lymphotrophic Virus 1 (HTLV-1), can get uncontrolled disease called hyperinfection, which can be fatal. To help determine why this infection is so serious in co-infected patients, we studied biopsies obtained from the small intestine from patients with both infections and compared them to control biopsies. The biopsies from patients with both Strongyloides and HTLV-1 had increased numbers of white blood cells in their biopsies. In particular they displayed a type of lymphocyte that downregulates immune responses. Some of them had increased numbers of cells called eosinophils in the intestines. These cells can help eliminate Strongyloides. However, they were not found near the parasite, suggesting that something near the parasite was suppressing the host response that would control infection. These studies provide more evidence that HTLV-1 suppresses the host response that controls Strongyloides and that the suppression occurs at the site of infection in the small intestines.

Diagnosis of soil-transmitted helminth infections. An unsolved problemin the omics era

Infections caused by Strongyloides stercoralis and other soil-transmitted worms such as hookworms (Necator americanus and Ancylostoma duodenale) represent a major problem worldwide, especially in developing areas. They are difficult to suspect clinically since they produce non-specific and often overlapping signs and symptoms. Likewise, their long prepatent periods hamper the detection of parasitic structures. Microscopic diagnosis is still the most commonly used tool in healthcare laboratories but it is still far from being the ideal technique to detect these infections due to its low sensitivity. In addition, these nematodes have strong morphologic similarities and consequently microbiological diagnosis remains a challenge. Serology has made progress in the diagnosis of S. stercoralis infection but this option is not yet available for hookworms. Molecular biology techniques have been shown to slightly increase this lack of sensitivity, but as with other parasitic infections, they are not currently available for use in clinical microbiology laboratories. Supplement information: This article is part of a supplement entitled «SEIMC External Quality Control Programme. Year 2016», which is sponsored by Roche, Vircell Microbiologists, Abbott Molecular and Francisco Soria Melguizo, S.A. © 2019 Elsevier España, S.L.U. and Sociedad Española de Enfermedades Infecciosasy Microbiología Clínica. All rights reserved.

Strongyloides stercoralis infection: A systematic review of endemic cases in Spain

Background

Strongyloides stercoralis infection, a neglected tropical disease, is widely distributed. Autochthonous cases have been described in Spain, probably infected long time ago. In recent years the number of diagnosed cases has increased due to the growing number of immigrants, travelers and refugees, but endemically acquired cases in Spain remains undetermined.

Methodology

We systematically searched the literature for references on endemic strongyloidiasis cases in Spain. The articles were required to describe Strongyloides stercoralis infection in at least one Spanish-born person without a history of travel to endemic areas and be published before 31st May 2018. Epidemiological data from patients was collected and described individually as well as risk factors to acquisition of the infection, diagnostic technique that lead to the diagnosis, presence of eosinophilia and clinical symptoms at diagnosis.

Findings

Thirty-six studies were included, describing a total of 1083 patients with an average age of 68.3 years diagnosed with endemic strongyloidiasis in Spain. The vast majority of the cases were described in the province of Valencia (n = 1049). Two hundred and eight of the 251 (82.9%) patients in whom gender was reported were male, and most of them had current or past dedication to agriculture. Seventy percent had some kind of comorbidity. A decreasing trend in the diagnosed cases per year is observed from the end of last decade. However, there are still nefigw diagnoses of autochthonous cases of strongyloidiasis in Spain every year.

Conclusions

With the data provided by this review it is likely that in Spain strongyloidiasis might have been underestimated. It is highly probable that the infection remains undiagnosed in many cases due to low clinical suspicion among Spanish population without recent travel history in which the contagion probably took place decades ago.

S. stercoralis is a soil transmitted helminth that is common in many subtropical and tropical countries, but is also found in other regions of the world. In this study we reviewed all published material on endemic infection of S. stercoralis acquired in Spain issued before 31st May 2018. We collected data from these articles and reported clinical and epidemiological characteristics of patients. Our systematic review of the articles showed a clear geographical pattern; nearly 97% of the cases described had been acquired in the Valencia province. Most of them (82.9%) were male, and most had current or past dedication to agriculture. Our results showed that 70.3% had at least one condition or treatment that could have made them more vulnerable to suffer a severe form of this helminthic disease. Our data suggests that S. stercoralis infection probably remains underdiagnosed in Spanish population. Due to the scarce information available about endemic strongyloidiasis in Spain until now, we believe that the present work will be relevant and the conclusions derived from it might raise awareness about underdiagnosis. Transmission risk factors described in the people diagnosed may be key for prevention and control strategies implementation.

Strongyloides stercoralis hyperinfection syndrome: a deeper understanding of a neglected disease

Strongyloides stercoralis hyperinfection syndrome (SHS) is a life-threatening condition that warrants early detection and management. We describe the pathogenesis, organ-specific clinical manifestations, and risk factors associated to this condition. A comprehensive review of the literature was conducted in PubMed, LILACS, EBSCO and SciELO by using the keywords: "hyperinfection syndrome"; "Strongyloides stercoralis"; "disseminated strongyloidiasis"; "systemic strongyloidiasis", "pathogenesis" and "pathophysiology". Relevant articles on this topic were evaluated and included by consensus. Also, a secondary search of the literature was performed. Articles in English and Spanish language were included. SHS has been described in tropical and sub-tropical regions. However, there is growing evidence of cases detected in developed countries favored by increasing migration and the advance in immunosuppressive therapies for oncologic and inflammatory diseases. SHS is characterized by massive multiplication of larvae, typically in immunocompromised hosts. Clinical manifestations vary according to the organ involved and include diarrhea, intestinal bleeding, alveolar hemorrhages, heart failure, jaundice, bacteremia among others. Despite advances in the understanding of this condition, fatality rates are near 90%. Clinicians should consider SHS in the differential diagnosis of acutely ill patients with multiple organ damage and epidemiological risk factors. Adverse outcomes are common, especially with delayed anti-parasitic treatment.

IgG reactivity with 40-35 kDa soluble and membrane antigen of Strongyloides venezuelensis in immunocompromised patients

Immunocompromised patients constitute a risk group for the development of severe clinical forms of human strongyloidiasis. The diagnosis of this infection is primarily performed by parasitological techniques, but with low sensitivity. Serological techniques appear as an alternative, especially with heterologous antigens use. The aim of this study was to perform the Western blot technique by using S. venezuelensis infective third stage larva (iL3) soluble (TS) and membrane (TM) saline antigens to reveal immunoreactive bands in immunocompromised patients with strongyloidiasis. Serum samples from 117 parasitologically well-characterized patients were divided into four groups: S. stercoralis positive and immunocompetent (S + IC); S. stercoralis positive and immunocompromised (S + IP); negative and immunocompetent (S-IC); negative and immunocompromised (S-IP). A 40-35 kDa band was recognized by 100% of patients in the S + IC group in both antigenic fractions, and by 62.5% and 50% in the S + IP group using the TS and TM fractions, respectively. A 29 kDa band was recognized by 86.3% and 72.7% (for TS and TM, respectively) of patients in the S + IC group, and only by 12.5% of patients in the S + IP group on the TM antigen. Regardless of the patients' immunological condition, the 40-35 kDa band from S. venezuelensis was detected more frequently and can be used as an important marker to the immunodiagnosis of human strongyloidiasis.

Impact of the health education and preventive equipment package (HEPEP) on prevention of Strongyloides stercoralis infection among rural communities in Northeast Thailand: a cluster randomized controlled trial

Background

Strongyloidiasis is prevalent in northeast Thailand. This study aimed to evaluate the impact of the Health Education and Preventive Equipment Package (HEPEP), a package we developed to improve awareness and aid in the prevention of Strongyloides stercoralis infection among rural communities in northeast Thailand.

Methods

This was an intervention trial conducted in 12 villages (six interventions and six controls) in rural areas of northeast Thailand from March 2016 to September 2017. Single stool sample was collected from each participant and examined using agar plate culture (APC) technique. Each participant was interviewed using a pre-tested questionnaire, treated with single dose of ivermectin (200 μg/Kg), and allocated to either the intervention or control group. Members of the intervention group were given “Practices to Prevent Strongyloidiasis” poster and vinyl boards containing information aimed at raising awareness of S. stercoralis and strongyloidiasis. In addition, they were given a poster lecture regarding the lifecycle of S. stercoralis before being treated with ivermectin. Aside from that, they were also given a protective equipment package. Monthly refresher courses were provided by village health volunteers (VHVs) regarding the health information they had received and proper equipment usage. The control group, on the other hand, was only provided with a five-minute lecture regarding strongyloidiasis. Assessment of new infection was conducted 3 months later in 327 and 318 participants in the intervention group and control group, respectively.

Results

The HEPEP had 41% greater efficacy in preventing S. stercoralis infection in the intervention group than the measures taken in the control group (adjusted Odds Ratio (aOR) = 0.59; 95%CI: 0.41 to 0.85, P-value = 0.005). The intervention group also scored significantly higher on all aspects of a test of S. stercoralis knowledge compared with the control group (mean difference (mean dif.) = 2.89, P-value = < 0.05).

Conclusions

The HEPEP was the first model that has been found to be effective in controlling of S. stercoralis in rural communities in the northeast Thailand. The results should encourage policy makers and public health personnel to improve control programs, as well as health promotion, with regard to parasites.

Trial registration

Thai Clinical Trials Registry (TCTR), Medical Research Foundation of Thailand, Medical Research Network of the Consortium of Thai Medical Schools: MedResNet (Thailand) (identification number: TCTR20180404002) Registered 4 April 2018 (retrospectively registered).

Electronic supplementary material

The online version of this article (10.1186/s12889-018-6081-6) contains supplementary material, which is available to authorized users.

OCCASIONAL DIGESTIVE HEMORRHAGE IN CHILDREN DUE TO STRONGYLOIDIASIS: IMPORTANCE OF PARASITOLOGIC TESTING

Objective:

To describe an uncommon case of infection by Strongyloides stercoralis (S. stercoralis) in a 4-month-old child and to highlight the importance of early diagnosis.

Case description:

The patient was a male child from the city of Videira, State of Santa Catarina, Southern Brazil, who was born preterm by Cesarean-section, weighing 1,655 g, and stayed in the neonatal intensive care unit for 20 days. At four months of age, the child started presenting blood in stools and the possibility of cow’s milk protein allergy was considered, given the symptoms and the use of infant formula in his 1^st semester of life, which was then replaced by infant formula with hydrolyzed protein. White blood cell count and a parasitological stool sample were requested. Both tested positive and the stool ova and parasite examination showed a rhabditoid larva of S. stercoralis. The clinician maintained the initial hypothesis and diet, but requested three new stool samples, which tested positive for rhabditoid larvae of S. stercoralis. Since the child presented abdominal pain and vomiting, and there was still blood in stools, treatment with thiabendazole was initiated twice a day for two days. Treatment was repeated after seven days along with a new parasitological examination, which was then negative.

Comments:

Although strongyloidiasis is usually a mild parasitic infection, it may be severe and disseminated in immunocompromised patients. This agent must be considered in patients who live in endemic areas, and the diagnosis should be established by searching S. stercoralis larvae in tracheal secretions and in stools.

Pathologic Features of Infectious Gastritis

This manuscript presents a review of infectious causes of gastritis aimed at the practicing anatomic pathologist. We shall highlight unique histologic findings and clinical attributes that will assist those analyzing endoscopically obtained mucosal biopsies of the stomach or resection specimens.

Strongyloidiasis Outside Endemic Areas: Long-term Parasitological and Clinical Follow-up After Ivermectin Treatment

BACKGROUND

Strongyloides stercoralis affects 30-100 million people worldwide. The first-line therapy is ivermectin. Cure is defined as the absence of larvae by parasitological methods 1 year after treatment. To date, no longitudinal parasitological studies for longer periods of time have been conducted to confirm its cure. Here, we evaluated treatment response in long-term follow-up patients with chronic infection using parasitological and molecular methods for larvae or DNA detection.

METHODS

A prospective, descriptive, observational study was conducted between January 2009 and September 2015 in Buenos Aires, Argentina. Twenty-one patients with S. stercoralis diagnosis were evaluated 30, 60, and 90 days as well as 1, 2, 3, and/or 4 years after treatment by conventional methods (fresh stool, Ritchie method, agar plate culture), S. stercoralis-specific polymerase chain reaction (PCR) in stool DNA, and eosinophil values.

RESULTS

During follow-up, larvae were detected by conventional methods in 14 of 21 patients. This parasitological reactivation was observed starting 30 days posttreatment (dpt) and then at different times since 90 dpt. Eosinophil values decreased (P = .001) 30 days after treatment, but their levels were neither associated with nor predicted these reactivations. However, S. stercoralis DNA was detected by PCR in all patients, both in their first and subsequent stool samples, thus reflecting the poor efficacy of ivermectin at eradicating parasite from host tissues. Asymptomatic eosinophilia was the most frequent clinical form among chronically infected patients.

CONCLUSIONS

These results suggest that the parasitological cure is unlikely. Strongyloidiasis must be considered a chronic infection and ivermectin administration schedules should be reevaluated.

Soil-transmitted helminth infections

More than a quarter of the world's population is at risk of infection with the soil-transmitted helminths Ascaris lumbricoides, hookworm (Ancylostoma duodenale and Necator americanus), Trichuris trichiura, and Strongyloides stercoralis. Infected children and adults present with a range of medical and surgical conditions, and clinicians should consider the possibility of infection in individuals living in, or returning from, endemic regions. Although safe and effective drugs are donated free to endemic countries, only half of at-risk children received treatment in 2016. This Seminar describes the epidemiology, lifecycles, pathophysiology, clinical diagnosis, management, and public health control of soil-transmitted helminths. Previous work has questioned the effect of population-level deworming; however, it remains beyond doubt that treatment reduces the severe consequences of soil-transmitted helminthiasis. We highlight the need for refined diagnostic tools and effective control options to scale up public health interventions and improve clinical detection and management of these infections.

Methylprednisolone acetate induces, and Δ7-dafachronic acid suppresses, Strongyloides stercoralis hyperinfection in NSG mice

Strongyloides stercoralis hyperinfection causes high mortality rates in humans, and, while hyperinfection can be induced by immunosuppressive glucocorticoids, the pathogenesis remains unknown. Since immunocompetent mice are resistant to infection with S. stercoralis, we hypothesized that NSG mice, which have a reduced innate immune response and lack adaptive immunity, would be susceptible to the infection and develop hyperinfection. Interestingly, despite the presence of large numbers of adult and first-stage larvae in S. stercoralis-infected NSG mice, no hyperinfection was observed even when the mice were treated with a monoclonal antibody to eliminate residual granulocyte activity. NSG mice were then infected with third-stage larvae and treated for 6 wk with methylprednisolone acetate (MPA), a synthetic glucocorticoid. MPA treatment of infected mice resulted in 50% mortality and caused a significant >10-fold increase in the number of parasitic female worms compared with infected untreated mice. In addition, autoinfective third-stage larvae, which initiate hyperinfection, were found in high numbers in MPA-treated, but not untreated, mice. Remarkably, treatment with Δ7-dafachronic acid, an agonist of the parasite nuclear receptor Ss-DAF-12, significantly reduced the worm burden in MPA-treated mice undergoing hyperinfection with S. stercoralis Overall, this study provides a useful mouse model for S. stercoralis autoinfection and suggests a therapeutic strategy for treating lethal hyperinfection.

Strongyloides stercoralis is associated with significant morbidity in rural Cambodia, including stunting in children

Background

Strongyloides stercoralis is a soil-transmitted nematode that can replicate within its host, leading to long-lasting and potentially fatal infections. It is ubiquitous and highly prevalent in Cambodia. The extent of morbidity associated with S. stercoralis infection is difficult to assess due to the broad spectrum of symptoms and, thus, remains uncertain.

Methodology/Principal findings

Clinical signs were compared among S. stercoralis infected vs. non-infected participants in a cross-sectional survey conducted in 2012 in eight villages of Northern Cambodia, and before and after treatment with a single oral dose of ivermectin (200μg/kg BW) among participants harboring S. stercoralis. Growth retardation among schoolchildren and adolescents was assessed using height-for-age and thinness using body mass index-for-age. S. stercoralis prevalence was 31.1% among 2,744 participants. Urticaria (55% vs. 47%, OR: 1.4, 95% CI: 1.1–1.6) and itching (52% vs. 48%, OR: 1.2, 95% CI: 1.0–1.4) were more frequently reported by infected participants. Gastrointestinal, dermatological, and respiratory symptoms were less prevalent in 103 mono-infected participants after treatment. Urticaria (66% vs. 11%, OR: 0.03, 95% CI: 0.01–0.1) and abdominal pain (81 vs. 27%, OR: 0.07, 95% CI: 0.02–0.2) mostly resolved by treatment. S. stercoralis infection was associated with stunting, with 2.5-fold higher odds in case of heavy infection.

Conclusions/Significance

The morbidity associated with S. stercoralis confirmed the importance of gastrointestinal and dermatological symptoms unrelated to parasite load, and long-term chronic effects when associated with malnutrition. The combination of high prevalence and morbidity calls for the integration of S. stercoralis into ongoing STH control measures in Cambodia.

Strongyloides stercoralis is an intestinal parasite that infects humans by penetrating intact skin. It thrives particularly in tropical countries with poor sanitation. Because it can replicate within its host, it causes long-lasting infections and is potentially fatal in patients with a disseminated infection. S. stercoralis is largely neglected due to the difficulty in detecting it with standard field diagnostic techniques but has recently been found to be very common in Cambodia, with prevalence rates exceeding 40%. It is difficult to identify symptoms associated with infection in endemic areas because co-infections with other helminths or protozoan parasites, which cause similar health problems, are common. We compared clinical signs in infected vs. non-infected participants living in eight villages in Northern Cambodia, and before and after treatment with ivermectin, the drug of choice against S. stercoralis, among 103 patients infected with S. stercoralis only. We also assessed the association between infection and growth retardation among children and adolescents. Of the participants, 31.1% were infected with S. stercoralis. Infected participants were more likely to report itching and urticaria. After treatment, fewer participants reported urticaria, abdominal pain, vomiting and, to a lesser extent, nausea, diarrhea, cough, and tiredness. S. stercoralis infection was associated with growth retardation as expressed by stunting.

Cerebrospinal fluid cytology in nonmalignant aseptic meningeal disorders

Cerebrospinal fluid cytology examination is a common and reliable primary and/or complementary procedure for the diagnosis of central nervous system (CNS) disorders. This review provides an update of aseptic meningeal disorders that may be encountered in cytopathology practice. The article covers the cytological findings and helpful ancillary studies needed of nonmalignant aseptic CNS disorders such as viral, bacterial, fungal and parasitic infections, and other noninfectious diseases, such as Mollaret's meningitis (recurrent benign lymphocytic meningitis), Guillain-Barré syndrome, multiple Sclerosis, subarachnoid haemorrhage, and drug-induced disorders.