The laboratory diagnosis and follow up of strongyloidiasis: a systematic review

Comparative Diagnosis of Strongyloidiasis in Immunocompromised Patients

Strongyloides hyperinfection syndrome and disseminated strongyloidiasis frequently occur in immunocompromised persons and can lead to high complication and mortality rates. Thus, detection of Strongyloides stercolaris in those patients is crucial. The present study aimed to determine the prevalence of strongyloidiasis and compare the detection rates of different strongyloidiasis detection methods. We conducted a cross-sectional study of 135 adults with various immunocompromising conditions (corticosteroid usage, chemotherapy, hematologic malignancies, organ transplants, use of immunosuppressive agents, and symptomatic human immunodeficiency virus infection) in Phramongkutklao Hospital, Bangkok, Thailand. All patients were asked to undergo serology testing for Strongyloides IgG by indirect enzyme-linked immunosorbent assay (ELISA), and 3 days of stool collection for use in a simple smear along with formalin-ether concentration and agar plate techniques. Prevalence rates of strongyloidiasis were 5% by stool concentration technique, 5.4% by IgG-ELISA, and 6.7% by agar plate culture. Three of the eight strongyloidiasis cases in this study had hyperinfection syndrome. The tested risk factors of age, sex, occupation, and immunocompromising condition were not associated with Strongyloides infestation. Serology was only 42.9% sensitive (positive predictive value), but it was 96.3% specific (negative predictive value). In conclusion, prevalence rates of strongyloidiasis in this study were 5-7%. Although agar plate culture was the most sensitive technique, the other diagnostic methods might be alternatively used.

Laboratory Diagnosis of Infections in Cancer Patients: Challenges and Opportunities

Infections remain a significant cause of morbidity and mortality in cancer patients. The differential diagnosis for these patients is often wide, and the timely selection of the right clinical tests can have a significant impact on their survival. However, laboratory findings with current methodologies are often negative, challenging clinicians and laboratorians to continue the search for the responsible pathogen. Novel methodologies are providing increased sensitivity and rapid turnaround time to results but also challenging our interpretation of what is a clinically significant pathogen in cancer patients. This minireview provides an overview of the most common infections in cancer patients and discusses some of the challenges and opportunities for the clinical microbiologist supporting the care of cancer patients.

Molecular testing for clinical diagnosis and epidemiological investigations of intestinal parasitic infections

Over the past few decades, nucleic acid-based methods have been developed for the diagnosis of intestinal parasitic infections. Advantages of nucleic acid-based methods are numerous; typically, these include increased sensitivity and specificity and simpler standardization of diagnostic procedures. DNA samples can also be stored and used for genetic characterization and molecular typing, providing a valuable tool for surveys and surveillance studies. A variety of technologies have been applied, and some specific and general pitfalls and limitations have been identified. This review provides an overview of the multitude of methods that have been reported for the detection of intestinal parasites and offers some guidance in applying these methods in the clinical laboratory and in epidemiological studies.

Eosinophilia prevalence and related factors in travel and immigrants of the network +REDIVI

The population movements during the last decades have resulted in a progressively increasing interest in certain infectious diseases. Eosinophilia is a common finding in immigrants and travellers. One of the most common causes of eosinophilia is helminth infection, and some intestinal protozoa. The aim of this paper is to describe the epidemiological characteristics of cases with eosinophilia and its association with the presence of parasites in the REDIVI data network. This is a multicentre prospective observational study that includes patients diagnosed with eosinophilia registered in the cooperative network for the study of infectious diseases in travellers and immigrants (+REDIVI) from January 2009 to December 2012. A total of 5,255 episodes were recorded in the network during the study period, and eosinophilia was observed in 8.1-31.3% of cases (depending on the immigration group). There were 60.2% men, with a median age of 31years. There were 72.4% immigrants, and 81.2% were asymptomatic. The most commonly identified parasites were S.stercoralis (34.4%), Schistosoma sp. (11.0%), and hookworm (8.6%). The relationship between eosinophilia and parasite infection was significant for all helminths (except for cutaneous larva migrans). The symptoms and duration of the journey did not significantly determine the presence of eosinophilia. In the case of eosinophilia in a person who has lived in helminth endemic areas, it is advisable to carry out targeted studies to diagnose the infection, regardless of immigration type, length of stay, or the presence of symptoms.

Discordances Between Serology and Culture for Strongyloides in an Ethiopian Adopted Child With Multiple Parasitic Infections: A Case Report

RATIONALE

infectious diseases screening of international adoptees is complex because of the concurrence of different pathogens in a child at same time. We describe an international adopted child born at Ethiopia infected by 5 different pathogens (Hymenolepis nana, Giardia intestinalis, Entamoeba histolytica, Strongyloides stercoralis, and Trichuris trichiura), 2 of them S. stercoralis and E. histolytica with a capacity to develop severe clinical complications if not detected promptly with appropriate diagnosis tests.Concerns of the patient: according to the screening protocol a stool sample is always processed for culture addressed to find out protozoan and helminthic pathogens but not specifically for S. stercoralis. Only, when eosinophilia is detected 3 serial stool samples are collected to rule out intestinal parasitic infection including S. stercoralis.

INTERVENTIONS

in our case, S. stercoralis would not have been detected if we had followed the protocol because eosinophilia was absent and its specific serology was negative. Fortunately, the initial inclusion of the feces charcoal culture for S. stercoralis allowed us to detect this infection.

OUTCOMES

discordances between direct methods such as culture and indirect as serology or antigen test forces us to be very cautious before ruling out S. stercoralis or E. histolytica infection, respectively. Also, if a child from tropical areas has persistent symptoms (such as diarrhea or fever) that have not been treated we have to rule out other infections that have not been detected yet.Main lessons: The introduction of different sequencing tests and the insistence to find out pathogens such as S. stercoralis or E. histolytica was determinant to be able to cure this symptomatic child and to prevent potential severe clinical forms in case of immunosuppression.

Infectious Diseases in Sub-Saharan Immigrants to Spain

Immigrants may be carriers of infectious diseases because of the prevalence of these diseases in their country of origin, exposure during migration, or conditions during resettlement, with this prevalence being particularly high in sub-Saharan Africans. We performed a retrospective review of 180 sub-Saharan immigrants screened for infectious diseases at an International Health Center from January 2009 to December 2012. At least one pathogenic infectious disease was diagnosed in 72.8% patients: 60.6% latent tuberculosis infection, 36.8% intestinal parasites (intestinal protozoa or helminths), 28.1% helminths, 14.8% hepatitis B surface antigen positive, 1.2% anti-hepatitis C virus positive, 1.2% human immunodeficiency virus-positive, and 1.2% malaria. Coinfections were present in 28.4%. There was significant association between eosinophilia (absolute count or percentage) or hyper-IgE and the presence of helminths (P< 0.001). Relative eosinophilia and hyper-IgE were better indicators of helminth infection than absolute eosinophilia, particularly for schistosomiasis and strongyloidiasis. We found a high prevalence of infectious diseases in sub-Saharan immigrants, which could lead to severe health problems (in the absence of prompt treatment), representing a high cost to the public health system and possible transmission in the host country. Accurate screening and tailored protocols for infectious diseases are recommended in sub-Saharan immigrants.

Real-Time Polymerase Chain Reaction in Stool Detects Transmission of Strongyloides stercoralis from an Infected Donor to Solid Organ Transplant Recipients

Solid organ transplant recipients can acquire Strongyloides stercoralis from an infected donor. The diagnosis of S. stercoralis in immunocompromised individuals may be challenging due to a lower sensitivity of available parasitological and serological methods, compared with immunocompetent individuals. Recently, a real-time polymerase chain reaction (RT-PCR) in stool has been developed for S. stercoralis diagnosis. We report two cases of S. stercoralis infection transmitted by a donor to two solid organ transplant recipients, who were diagnosed with RT-PCR in stool. This test could play an important role inS. stercoralis diagnosis in immunosuppressed patients, facilitating rapid treatment initiation and reducing the risk of severe strongyloidiasis. Adherence to current recommendations of screening among donors and recipients from endemic areas is also urgently needed.

Strongyloides stercoralis, Eosinophilia, and Type 2 Diabetes Mellitus: The Predictive Value of Eosinophilia in the Diagnosis of S stercoralis Infection in an Endemic Community

Background.  This study examines the predictive value of eosinophilia for Strongyloides stercoralis infection, as measured by enzyme-linked immunosorbent assay (ELISA) testing, in an endemic community. In remote communities, eosinophilia is frequently used as a proxy test for the presence of helminth infections. Past studies of eosinophilia and Strongyloides infection have been conducted in specific groups such as immigrants and refugees, or in subpopulations of nonendemic communities, rather than in endemic communities. Methods.  We conducted a cross-sectional study of the relationship between eosinophilia and Strongyloides ELISA serology, as part of a study into the relationship between S stercoralis infection and type 2 diabetes mellitus (T2DM) in an Indigenous community in northern Australia. Results.  Two hundred thirty-nine adults had their eosinophil count and S stercoralis ELISA serology measured in 2012 and 2013, along with other biometric and metabolic data. Eosinophilia was found to have a relatively poor sensitivity (60.9%), specificity (71.1%), positive predictive value (54.6%), and negative predictive value (76.1%) for S stercoralis ELISA positivity in this group. However, there was a more constant relationship between eosinophilia and S Stercoralis ELISA positivity in patients with T2DM (negative predictive value 87.5%). Conclusion.  This study suggests that the presence or absence of eosinophilia is not an adequate proxy test for S stercoralis infection in a community where the infection is prevalent, and that the association between eosinophilia and S stercoralis ELISA positivity is more constant in patients with T2DM.

Association between Strongyloides stercoralis infection and cortisol secretion in alcoholic patients

A higher prevalence of Strongyloides stercoralis infections has been reported in alcoholic patients compared to nonalcoholic patients living in the same area. Excessive alcohol consumption increases the levels of endogenous corticosteroids that subsequently enhance the fecundity of S. stercoralis parthenogenetic females. These corticosteroids also enhance the transformation of rhabditiform larvae into infective filariform larvae by mimicking the effect of the ecdysteroid hormones produced by the parasite, thus leading to autoinfection. In addition, alterations in the intestinal barrier and host immune response contribute to the development of hyperinfection and severe strongyloidiasis in alcoholic patients. The aim of this study was to evaluate the frequency of S. stercoralis infections in alcoholic patients and to determine the association between S. stercoralis infection and endogenous cortisol levels. The frequency of infection was evaluated in 332 alcoholic and 92 nonalcoholic patients. The parasitological diagnosis was carried out by agar plate culture, the modified Baermann-Moraes method and spontaneous sedimentation. The immunological diagnosis was performed using an ELISA with anti-S. stercoralis IgG. The cortisol levels were measured in serum samples by ELISA. The frequency of S. stercoralis infection in alcoholic patients was 23.5% (78/332), while in nonalcoholic patients, it was 5.4% (5/92) (p<0.05). The cortisol levels were higher in alcoholic than in nonalcoholic patients (p<0.05). However, among the alcoholic patients, the cortisol levels did not differ between S. stercoralis-infected and uninfected patients (p>0.05). As demonstrated in this work, 81.3% (26/32) of patients with a high parasite load, considered as more than 11 larvae per gram of feces, presented serum cortisol levels above the normal reference value (24 mg/dL). High endogenous cortisol levels in alcoholic patients were not associated to susceptibility to S. stercoralis infection, however once infected, this may lead to a high parasite load.

Ivermectin versus albendazole or thiabendazole for Strongyloides stercoralis infection

BACKGROUND

Strongyloidiasis is a gut infection with Strongyloides stercoralis which is common world wide. Chronic infection usually causes a skin rash, vomiting, diarrhoea or constipation, and respiratory problems, and it can be fatal in people with immune deficiency. It may be treated with ivermectin or albendazole or thiabendazole.

OBJECTIVES

To assess the effects of ivermectin versus benzimidazoles (albendazole and thiabendazole) for treating chronic strongyloides infection.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register (24 August 2015); the Cochrane Central Register of Controlled Trials (CENTRAL), published in the Cochrane Library; MEDLINE (January 1966 to August 2015); EMBASE (January 1980 to August 2015); LILACS (August 2015); and reference lists of articles. We also searched the metaRegister of Controlled Trials (mRCT) using 'strongyloid*' as a search term, reference lists, and conference abstracts.

SELECTION CRITERIA

Randomized controlled trials of ivermectin versus albendazole or thiabendazole for treating chronic strongyloides infection.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed risk of bias in the included trials. We used risk ratios (RRs) with 95% confidence intervals (CIs) and fixed- or random-effects models. We pooled adverse event data if the trials were sufficiently similar in their adverse event definitions.

MAIN RESULTS

We included seven trials, enrolling 1147 participants, conducted between 1994 and 2011 in different locations (Africa, Southeast Asia, America and Europe).In trials comparing ivermectin with albendazole, parasitological cure was higher with ivermectin (RR 1.79, 95% CI 1.55 to 2.08; 478 participants, four trials, moderate quality evidence). There were no statistically significant differences in adverse events (RR 0.80, 95% CI 0.59 to 1.09; 518 participants, four trials, low quality evidence).In trials comparing ivermectin with thiabendazole, there was little or no difference in parasitological cure (RR 1.07, 95% CI 0.96 to 1.20; 467 participants, three trials, low quality evidence). However, adverse events were less common with ivermectin (RR 0.31, 95% CI 0.20 to 0.50; 507 participants; three trials, moderate quality evidence).In trials comparing different dosages of ivermectin, taking a second dose of 200 μg/kg of ivermectin was not associated with higher cure in a small subgroup of participants (RR 1.02, 95% CI 0.94 to 1.11; 94 participants, two trials).Dizziness, nausea, and disorientation were commonly reported in all drug groups. There were no reports of serious adverse events or death.

AUTHORS' CONCLUSIONS

Ivermectin results in more people cured than albendazole, and is at least as well tolerated. In trials of ivermectin with thiabendazole, parasitological cure is similar but there are more adverse events with thiabendazole.

Strongyloides stercoralis Infection in Alcoholic Patients

The course of Strongyloides stercoralis infection is usually asymptomatic with a low discharge of rhabditoid larva in feces. However, the deleterious effects of alcohol consumption seem to enhance the susceptibility to infection, as shown by a fivefold higher strongyloidiasis frequency in alcoholics than in nonalcoholics. Moreover, the association between S. stercoralis infection and alcoholism presents a risk for hyperinfection and severe strongyloidiasis. There are several possible mechanisms for the disruption of the host-parasite equilibrium in ethanol-addicted patients with chronic strongyloidiasis. One explanation is that chronic ethanol intake stimulates the hypothalamic-pituitary-adrenal (HPA) axis to produce excessive levels of endogenous cortisol, which in turn can lead to a deficiency in type 2 T helper cells (Th2) protective response, and also to mimic the parasite hormone ecdysone, which promotes the transformation of rhabditiform larvae to filariform larvae, leading to autoinfection. Therefore, when untreated, alcoholic patients are continuously infected by this autoinfection mechanism. Thus, the early diagnosis of strongyloidiasis and treatment can prevent serious forms of hyperinfection in ethanol abusers.

The laboratory diagnosis of Strongyloides stercoralis

It is estimated that over 30million people worldwide are infected by the nematode, Strongyloides stercoralis1. It is endemic in sub-tropical and tropical parts of Australia, with high rates of infection documented in some indigenous communities2. Due to the potential for chronic autoinfection, that may persist for decades, migration leads to the presence of the infection in non-endemic areas1. Transmission to humans is generally through the penetration of larvae through the skin, following contact with faecally contaminated soil1. Disease severity ranges from asymptomatic chronic carriage to an overwhelming illness, where large numbers spread throughout the body, usually triggered by immunosuppression1.

Mass Administration of Ivermectin for the Elimination of Onchocerciasis Significantly Reduced and Maintained Low the Prevalence of Strongyloides stercoralis in Esmeraldas, Ecuador

Objectives

To evaluate the effect of ivermectin mass drug administration on strongyloidiasis and other soil transmitted helminthiases.

Methods

We conducted a retrospective analysis of data collected in Esmeraldas (Ecuador) during surveys conducted in areas where ivermectin was annually administered to the entire population for the control of onchocerciasis.

Data from 5 surveys, conducted between 1990 (before the start of the distribution of ivermectin) and 2013 (six years after the interruption of the intervention) were analyzed. The surveys also comprised areas where ivermectin was not distributed because onchocerciasis was not endemic.

Different laboratory techniques were used in the different surveys (direct fecal smear, formol-ether concentration, IFAT and IVD ELISA for Strongyloides stercoralis).

Results

In the areas where ivermectin was distributed the strongyloidiasis prevalence fell from 6.8% in 1990 to zero in 1996 and 1999. In 2013 prevalence in children was zero with stool examination and 1.3% with serology, in adult 0.7% and 2.7%.

In areas not covered by ivermectin distribution the prevalence was 23.5% and 16.1% in 1996 and 1999, respectively. In 2013 the prevalence was 0.6% with fecal exam and 9.3% with serology in children and 2.3% and 17.9% in adults.

Regarding other soil transmitted helminthiases: in areas where ivermectin was distributed the prevalence of T. trichiura was significantly reduced, while A. lumbricoides and hookworms were seemingly unaffected.

Conclusions

Periodic mass distribution of ivermectin had a significant impact on the prevalence of strongyloidiasis, less on trichuriasis and apparently no effect on ascariasis and hookworm infections.

Strongyloides stercoralis (Ss) is a soil-transmitted helminth (STH) that is not yet targeted by control programs, although it is highly prevalent in many areas of the world and may cause severe consequences, in particular to immunosuppressed patients, with a high fatality rate. Unfortunately, albendazole, the drug most commonly used for the control of the other STH (hookworm, Ascaris lumbricoides and Trichuris trichiura) has little effect on Ss. The drug of choice, ivermectin, has been extensively used in mass drug administration (MDA) for the filarial worms Onchocerca volvulus and Wuchereria bancrofti. In the province of Esmeraldas, in Ecuador, we studied Ss (and other STH) prevalence from 1990 (prior to MDA initiation) to 2013 (6 years after MDA cessation) in rural communities where MDA was regularly executed for onchocerciasis compared with neighboring communities where ivermectin was not distributed because onchocerciasis was not present. Ss prevalence remained high over the years in the areas with no MDA, while in those with MDA prevalence fell to zero, and remained very low 6 years after MDA cessation. A less important effect was observed for T. trichiura. Adding ivermectin to MDA programs for STH would importantly contribute to the control of Ss infection.

Type 2 Diabetes Mellitus Is Associated with Strongyloides stercoralis Treatment Failure in Australian Aboriginals

Objective

To explore the efficacy of ivermectin in the treatment of serologically diagnosed cases of Strongyloides stercoralis (S. stercoralis) infection in an Aboriginal community and to describe factors that may influence the outcome of treatment.

Methods

Longitudinal study of a group of 92 individuals with serologically diagnosed S. stercoralis treated with ivermectin and followed up over a period of approximately 6 months. Main outcomes were serological titers pre and post treatment, diabetic status, and duration of follow up.

Findings

Treatment success was achieved in 62% to 79% of cases dependent on the methods employed for the diagnosis of infection and assessment of treatment outcome. Type 2 Diabetes Mellitus (T2DM) was found to be significantly associated with treatment failure in this group for two of the three methods employed.

Interpretation

Ivermectin has been confirmed as an effective treatment for S stercoralis infection in this setting. T2DM appears to be an independent risk factor for treatment failure in this population, and plausible mechanisms to explain this observation are presented.

In this study we examine the treatment of the intestinal worm infection Strongyloides stercoralis, a soil transmitted helminth that is common in the developing world and in the Aboriginal communities of northern Australia. Oral ivermectin is generally accepted as the treatment of choice for this condition. We screened an Aboriginal community for Strongyloides infection over the course of 2 years and measured the outcome of treatment in the 92 cases we found. This study measures the success or otherwise of treatment, and looks at whether there are any factors that could influence the rate of treatment failure. The results suggest that ivermectin is an effective treatment for Strongyloides in this setting, and that pre-existing Type 2 Diabetes Mellitus is a risk factor for treatment failure, an observation of great interest in Aboriginal communities where the prevalence of both conditions is very high. We discuss some possible mechanisms to help explain this previously unknown relationship.

Membrane fractions from Strongyloides venezuelensis in the immunodiagnosis of human strongyloidiasis

Strongyloides venezuelensis is a parasitic nematode of rodents frequently used to obtain heterologous antigens for the immunological diagnosis of human strongyloidiasis. The aim of this study was to evaluate membrane fractions from S. venezuelensis for human strongyloidiasis immunodiagnosis. Soluble and membrane fractions were obtained in phosphate saline (SS and SM) and Tris-HCl (TS and TM) from filariform larvae of S. venezuelensis. Ninety-two serum samples (n = 92) were obtained from 20 strongyloidiasis patients (Group I), 32 from patients with other parasitic diseases (Group II), and 40 from healthy individuals (Group III), and were analyzed by enzyme-linked immunosorbent assay (ELISA). Soluble fractions (SS and TS) showed 90.0% sensitivity and 88.9% specificity, whereas the membrane fractions (SM and TM) showed 95.0% sensitivity and 94.4% specificity. The present results suggest the possible use of membrane fractions of S. venezuelensis as an alternative antigen for human strongyloidiasis immunodiagnosis.

Eosinophils in Gastrointestinal Disorders: Eosinophilic Gastrointestinal Diseases, Celiac Disease, Inflammatory Bowel Diseases, and Parasitic Infections

The gastrointestinal (GI) tract provides an intriguing organ for considering the eosinophil's role in health and disease. The normal GI tract, except for the esophagus, is populated by eosinophils that are present throughout the mucosa, raising the possibility that eosinophils participate in innate mechanisms of defense. However, data from clinical studies associates increased numbers of eosinophils with inflammatory GI diseases, prompting concerns that eosinophils may have a deleterious effect on the gut. We present clinical features of 4 disease processes that have been associated with eosinophilia and suggest areas requiring investigation as to their clinical significance and scientific relevance.

Novel approaches to the diagnosis of Strongyloides stercoralis infection

Strongyloides stercoralis differs from the other soil-transmitted helminths because it puts infected subjects at risk of a fatal syndrome (in cases of immunosuppression for medical conditions, immunosuppressant therapies, or both). Chronic strongyloidiasis is often a non-severe condition, or is sometimes even asymptomatic, but diagnosis and effective therapy are essential in order to eradicate the infection and the life-long risk involved. Therefore, diagnostic methods need to be highly sensitive. Stool microscopy and the Kato-Katz technique are commonly used in prevalence studies, but they are inadequate for S. stercoralis detection. This is probably the main reason why the global prevalence has long been underestimated. Concentration methods, the Baermann technique and Koga agar plate culture have better, but still unsatisfactory, sensitivity. Serological tests have demonstrated higher sensitivity; although some authors have concerns about their specificity, it is possible to define cut-off values over which infection is almost certain. In particular, the luciferase immunoprecipitation system technique combined with a recombinant antigen (NIE) demonstrated a specificity of almost 100%. ELISA coproantigen detection has also shown promising results, but still needs full evaluation. Molecular diagnostic methods are currently available in a few referral centres as in-house techniques. In this review, on the basis of the performance of the different diagnostic methods, we outline diagnostic strategies that could be proposed for different purposes, such as: prevalence studies in endemic areas; individual diagnosis and screening; and monitoring of cure in clinical care and clinical trials.

Evaluation of eosinophilia in immigrants in Southern Spain using tailored screening and treatment protocols: A prospective study

OBJECTIVE

To determine the etiology of eosinophilia in immigrant patients in Southern Spain.

METHODS

Prospective study of immigrant patients with eosinophilia (> 500 Eo/μL) attended in a reference Tropical Medicine Unit and evaluated through the implementation of a specific protocol structured in different levels meant to be accomplished depending on the findings of each previous level.

RESULTS

Out of the 549 patients included in the study (89.6% from sub-Saharan countries), a diagnosis of helminthiasis was reached in 417 (75.9%), mainly by Strongyloides stercoralis (n = 190), Schistosoma (n = 33) and Hookworms (n = 126). 30 patients (5.5%) had a non-parasitic disorder (asthma, allergic rhinoconjunctivitis, skin conditions and drug-related eosinophilia). Multiple helminthic infections were very common: in 107 patients (19.5%) 2 helminth species were identified, three in 21 patients (3.8%), and four or more in 6 patients (1.1%). Eosinophilia was resolved in 31 of the 33 patients (93.9%) who received empirical treatment with ivermectin, albendazole and praziquantel as an etiological diagnosis was not reached after applying the whole protocol.

CONCLUSIONS

Diagnosis of helminthic infections in immigrant patients with eosinophilia can be improved by using tailored protocols based on geographical exposure. The implementation of these protocols may also save costs by systematizing diagnostic explorations. Empirical treatment with ivermectin, albendazol and praziquantel in sub-Saharan population when an etiologic diagnosis of eosinophilia has not been attained is an effective measure.

Strongyloidiasis in a diabetic patient accompanied by gastrointestinal stromal tumor: cause of eosinophilia unresponsive to steroid therapy

We report here a case of strongyloidiasis in a 72-year-old diabetic patient (woman) accompanied by gastrointestinal stromal tumor receiving imatinib therapy, first diagnosed as hypereosinophilic syndrome and treated with steroids for uncontrolled eosinophilia. She suffered from lower back pain and intermittent abdominal discomfort with nausea and diagnosed with gastrointestinal stromal tumor. After post-operative imatinib treatment eosinophilia persisted, so that steroid therapy was started under an impression of hypereosinophilic syndrome. In spite of 6 months steroid therapy, eosinophilia persisted. Stool examination was performed to rule out intestinal helminth infections. Rhabditoid larvae of Strongyloides stercoralis were detected and the patient was diagnosed as strongyloidiasis. This diagnosis was confirmed again by PCR. The patient was treated with albendazole for 14 days and her abdominal pain and diarrhea improved. This case highlights the need for thorough investigation, including molecular approaches, to test for strongyloidiasis before and during steroid therapies.

Persistent strongyloidiasis complicated by recurrent meningitis in an HTLV seropositive Peruvian migrant resettled in Italy

We describe a case of persistent strongyloidiasis complicated by recurrent meningitis, in a human T cell lymphotropic virus type 1 (HTLV-1) seropositive Peruvian migrant adult resettled in Italy. He was admitted with signs and symptoms of acute bacterial meningitis, reporting four other meningitis episodes in the past 6 years, with an etiological diagnosis of Escherichia coli and Enterococcus faecium in two cases. He had been previously treated with several antihelmintic regimens not including ivermectin, without eradication of strongyloidiasis, and he had never been tested for HTLV before. During the described episode, the patient was treated for meningitis with broad-spectrum antibiotic therapy and 200 μg/kg/dose oral ivermectin once daily on day 1, 2, 15 and 16 with full recovery and no further episodes of meningitis. The presented case underlines several critical points concerning the management of poorly known neglected diseases such as strongyloidiasis and HTLV infection in low-endemic areas. Despite several admissions for meningitis and strongyloidiasis, the parasitic infection was not adequately treated and the patient was not previously tested for HTLV. The supply of ivermectin and the choice of treatment scheme was challenging since ivermectin is not approved in Italy and there are no standardized guidelines for the treatment of severe strongyloidiasis in HTLV seropositive subjects.

Clinical consequences of new diagnostic tools for intestinal parasites

Following the success of nucleic acid-based detection in virology and bacteriology, multiplex real-time PCRs are increasingly used as first-line diagnostics in clinical parasitology, replacing microscopy. The detection and quantification of parasite-specific DNA in faeces is highly sensitive and specific and allows for cost-effective high-throughput screening. In this paper we discuss the clinical consequences of this radical change in diagnostic approach, as well as its potential drawbacks. In the Netherlands, routine diagnostic laboratories have been pioneering the implementation of multiplex real-time PCR for the detection of pathogenic intestinal protozoa and this has resulted in increased detection rates of Giardia lamblia and Cryptosporidium spp. As a consequence of this new diagnostic approach, expertise in the field of parasite morphology by conventional light microscopy seems to be disappearing in most of the high-throughput microbiological laboratories. As a result, to maintain a high standard of care, a formalized exchange of critical information between clinicians and laboratory staff is necessary to determine the most appropriate testing either in local laboratories or in reference centres, based on clinical signs and symptoms, exposure and immune status. If such a diagnostic algorithm is lacking, important infections in travellers, immigrants and immunocompromised patients may be missed.

Strongyloidiasis with emphasis on human infections and its different clinical forms

Strongyloidiasis (caused by Strongyloides stercoralis, and to a lesser extent by Strongyloides fuelleborni) is one of the most neglected tropical diseases with endemic areas and affecting more than 100 million people worldwide. Chronic infections in endemic areas can be maintained for decades through the autoinfective cycle with the L3 filariform larvae. In these endemic areas, misdiagnosis, inadequate treatment and the facilitation of the hyperinfection syndrome by immunosuppression are frequent and contribute to a high mortality rate. Despite the serious health impact of strongyloidiasis, it is a neglected disease and very little is known about this parasite and the disease when compared to other helminth infections. Control of the disease is difficult because of the many gaps in our knowledge of strongyloidiasis. We examine the recent literature on different aspects of strongyloidiasis with emphasis in those aspects that need further research.

Strongyloidiasis: A case with acute pancreatitis and a literature review

Strongyloides stercoralis, a soil transmitted helminth infection, affects millions with varying prevalence worldwide. A large number of affected hosts are asymptomatic. Symptoms pertaining to pulmonary and gastrointestinal involvement may be present. Manifestations of involvement beyond lung and intestine can be seen with dissemination of infection and lethal hyperinfection. Immunosuppression secondary to use of steroids or other immunosuppressants and coexistence of human T-lymphotropic virus type-1 are the known risk factors for dissemination and hyperinfection. Diagnostic modalities comprise stool examination, serology and molecular testing. Stool tests are inexpensive but are limited by low sensitivity, whereas serologic and molecular tests are more precise but at the expense of higher cost. Treatment with Ivermectin or Albendazole as an alternative is safe and efficacious. We present a rare case of acute pancreatitis secondary to Strongyloides. High index of suspicion in patients specifically from endemic countries of origin and lack of other common etiologies of acute pancreatitis may help in early diagnosis and prompt treatment of this potentially fatal infection.

Does Strongyloides stercoralis infection protect against type 2 diabetes in humans? Evidence from Australian Aboriginal adults

OBJECTIVE

To explore the relationship between infection with Strongyloides stercoralis and the likelihood of having type 2 diabetes mellitus (T2DM).

METHODS

Cross-sectional survey of 259 Aboriginal adults living in a remote community in northern Australia during 2013. Prior infection with S. stercoralis was determined by ELISA testing on serum. Main outcomes were eosinophil count, T2DM diagnosis, HbA1c, BMI, fasting lipids, Hb, blood pressure.

FINDINGS

Ninety two participants (36%) had prior infection with S. stercoralis and 131 (51%) had T2DM. Those with previous S. stercoralis infection (ELISA titre ≥0.3) were 61% less likely to have a diagnosis of T2DM than those uninfected, adjusted for age, triglycerides, blood pressure and BMI using propensity score (adjusted OR=0.39, 0.23-0.67, P=0.001).

INTERPRETATION

In this remote community where prevalence of both S. stercoralis and T2DM is very high, infection with S. stercoralis appears to be associated with a significantly reduced risk of T2DM in adults. A plausible immunological mechanism has been identified in animal models. If confirmed, this result may have practical implications for the prevention of T2DM and associated metabolic disorders in humans. This finding should be explored further with larger longitudinal studies in transitional populations where the risk of both conditions is high.

FUNDING

No external funding was required for this study.

Accuracy of five serologic tests for the follow up of Strongyloides stercoralis infection

Background

Traditional faecal-based methods have poor sensitivity for the detection of S. stercoralis, therefore are inadequate for post-treatment evaluation of infected patients who should be carefully monitored to exclude the persistence of the infection. In a previous study, we demonstrated high accuracy of five serology tests for the screening and diagnosis of strongyloidiasis. Aim of this study is to evaluate the performance of the same five tests for the follow up of patients infected with S. stercoralis.

Methods

Retrospective study on anonymized, cryo-preserved samples available at the Centre for Tropical Diseases (Negrar, Verona, Italy). Samples were collected before and from 3 to 12 months after treatment. The samples were tested with two commercially-available ELISA tests (IVD, Bordier), two techniques based on a recombinant antigen (NIE-ELISA and NIE-LIPS) and one in-house IFAT. The results of each test were evaluated both in relation to the results of fecal examination and to those of a composite reference standard (classifying as positive a sample with positive stools and/or at least three positive serology tests). The associations between the independent variables age and time and the dependent variable value of serological test (for all five tests), were analyzed by linear mixed-effects regression model.

Results

A high proportion of samples demonstrated for each test a seroreversion or a relevant decline (optical density/relative light units halved or decrease of at least two titers for IFAT) at follow up, results confirmed by the linear mixed effects model that showed a trend to seroreversion over time for all tests. In particular, IVD-ELISA (almost 90% samples demonstrated relevant decline) and IFAT (almost 87%) had the best performance. Considering only samples with a complete negativization, NIE-ELISA showed the best performance (72.5% seroreversion).

Conclusions

Serology is useful for the follow up of patients infected with S. stercoralis and determining test of cure.

Patients infected by S. stercoralis are at risk of fatal complications. It is therefore mandatory to demonstrate complete response to therapy. Post treatment evaluation should be done with highly sensitive diagnostic methods, which can exclude the persistence of the infection. Serology is more sensitive than fecal examination and coproculture. In this study, we compare the post-treatment performance of five serology tests, and suggest that they can be useful for the follow up of patients with S. stercoralis infection, especially in non-endemic areas, where there is no risk of reinfection. In fact, the results of the tests show a progressive decrease, towards negativization, of the values (expressed in different units, depending on the specific test) through time.

Prevalence of strongyloidiasis in Latin America: a systematic review of the literature

Strongyloides stercoralis is rarely recognized as a major public health issue, probably because its burden is largely underestimated. We reviewed the literature (both PubMed and 'grey' literature) about the prevalence of strongyloidiasis in Latin America, an area of presumable high endemicity. There were finally 88 papers involved in the analysis, covering the period between 1981 and 2011. Studies were heterogeneous in several aspects, such as the populations screened and the diagnostic methods used. Most of the studies relied on direct coproparasitological examination, which has low sensitivity for the detection of S. stercoralis larvae. The following countries presented areas of high prevalence (>20%): Argentina, Ecuador, Venezuela, Peru and Brazil. Globally, for most of the included countries it was not possible to define reliable data because of paucity and/or inadequacy of studies. S. stercoralis requires specific diagnostic methods for its detection; therefore, surveys should be specifically designed in order to avoid underestimation of the infection.

Epidemiology of Strongyloides stercoralis on Mekong islands in southern Laos

Strongyloides stercoralis is a neglected helminth infection potentially that can lead to systemic infection in immunocompromised individuals. In Lao People's Democratic Republic (Lao PDR, Laos), information on S. stercoralis infection is scarce. We assessed S. stercoralis infection and associated risk factors and symptoms on the Mekong islands in Southern Laos. Baermann and Kato-Katz techniques were performed on two stool samples from each individual to detect S. stercoralis larvae and concomitant helminth infections. Among 729 individuals, 41.0% were infected with S. stercoralis. Men were at higher risk than women (OR 1.97, 95% CI 1.45-2.67). Urticaria and body itching was associated with S. stercoralis infection (OR 2.4, 95% CI 1.42-4.05). Infection with Opisthorchis viverrini (72.2%), Schistosoma mekongi (12.8%), and hookworm (56.1%) were very common. Few infections with Trichuris trichiura (3.3%), Ascaris lumbricoides (0.3%) and Taenia spp. (0.3%) were detected. The majority of helminth infections were of light intensity, with prevalences of 80.4%, 92.9%, 64.5%, 100% and 100%, for O. viverrini, hookworm, S. mekongi, T. trichiura and A. lumbricoides, respectively. Nevertheless, heavy infection intensities were observed for O. viverrini (1.0%), S. mekongi (14.0%) and hookworm (2.9%). S. stercoralis is highly endemic on the islands of Khong district, Champasack province, Southern Laos. The national helminth control programme should take action to control this helminth infection.

Five cases of recurrent meningitis associated with chronic strongyloidiasis

Although meningitis secondary to chronic strongyloidiasis is a rare complication, it is associated with a high mortality rate. Recurrent meningitis can occur if the underlying parasitic infection is left untreated. We report five cases of recurrent meningitis related to chronic strongyloidiasis that were associated with human T-lymphotropic virus type 1 (HTLV-1) infection. Common causative organisms are Escherichia coli, Streptococcus bovis, and Klebsiella pneumonia. One patient died during the second episode of meningitis. Three patients showed significant gastrointestinal and respiratory symptoms before developing headache and fever. In four cases, patients developed multiple recurrences even with the treatment of thiabendazol. Ivermectin seems to be a better agent compared with thiabendazol to achieve eradication of strongyloidiasis.

Prevalence and risk factors of acquiring Strongyloides stercoralis infection among patients attending a tertiary hospital in Thailand

OBJECTIVES

We aimed to determine the prevalence and risk factors for Strongyloides stercoralis infection in adult patients attending Siriraj Hospital, a tertiary hospital in Thailand.

METHODS

A case-control study was carried out between July 2008 and April 2010. Case and control were identified from 6022 patients for whom results of faecal examination were available. A case was a patient who had S. stercoralis larva detected from faecal examination. Control was randomly selected from patients without S. stercoralis larvae detected in three consecutive faecal examinations. The proportion of control to case was 2 : 1. Demographic and clinical data for the day of diagnosis and retrospectively up to 15 days preceding the date of faecal examination were reviewed from their medical records.

RESULTS

Overall, 149 (2.47%) patients had S. stercoralis larvae positive. There were 105 males (70.5%), with the mean (SD) age of 53.9 (17.2) years. A total of 300 controls were selected. Male gender (odds ratio (OR)  =  2.79, 95% confidence interval (CI) 1.78-4.27)), human immunodeficiency virus (HIV) infection (OR  =  3.23, 95% CI 1.43-7.29), and eosinophilia (OR  =  1.81, 95% CI 1.33-2.47) were found to be independent risk factors associated with S. stercoralis infection in this setting. Corticosteroid or other immunosuppressive treatment, and other concomitant illnesses were not associated with increased risk of S. stercoralis infection.

CONCLUSION

In this setting, strongyloidiasis was seen more often in male patients with eosinophilia and with HIV infection. Prevention of fatal complication caused by S. stercoralis by regular faecal examination, or serology for early detection and treatment of undiagnosed S. stercoralis infection, is warranted in these high-risk patients.

Use of dried blood spots to define antibody response to the Strongyloides stercoralis recombinant antigen NIE

An approach to improve the diagnosis of Strongyloides stercoralis infection is the use of serologic assays utilising the NIE antigen from S. stercoralis, with good diagnostic sensitivity and excellent specificity reported. Detection of antibody eluted from dried blood spots (DBS) has shown utility in large-scale seroepidemiological studies for a range of conditions and is appealing for use with children where sample collection is difficult. We adapted an existing NIE-enzyme linked immunosorbent assay (ELISA) for the testing of strongyloides antibody response on DBS, and evaluated it in a population screening and mass drug administration programme (MDA) for strongyloidiasis conducted in an Australian indigenous community. Study participants were treated with 200 μg/kg ivermectin (>15 kg) or 3× 400 mg albendazole (<15kg). The sensitivity of the NIE DBS-ELISA was determined by receiver operator characteristic (ROC) analysis to be 85.7%. A total of 214 DBS were collected from 184 participants across two screening and MDA encounters. A total of 27 of 164 participants (16.5%) tested positive for S. stercoralis NIE-DBS prior to MDA treatment, and 6 of 50 participants (12.0%) tested positive after treatment. These prevalence values are similar to those documented by standard serology in the same community. For 30 participants where a DBS was collected at both MDA 1 and 2, a significant decline in ELISA values was evident post treatment (0.12-0.02, p=0.0012). These results are in agreement with previous studies documenting the high seroprevalence of S. stercoralis in remote Australian Indigenous communities, and suggest that collection of dried blood spots may be a useful approach for field diagnosis of S. stercoralis seroprevalence.

Strongyloidiasis in immigrants in Southern Spain

OBJECTIVE

To analyse clinical and epidemiological characteristics of immigrant patients diagnosed with strongyloidiasis in our area.

METHODS

An analyse was performed on patients with strongyloidiasis seen in the Tropical Medicine Unit of the "Hospital de Poniente" in Almeria (Spain), from April 2004 to May 2012.

RESULTS

A total of 320 patients were diagnosed with Strongyloides stercoralis infection, and 284 out of 314 patients (90.4%) had a positive specific serology. Forty-two percent of the patients reported symptoms and 45% had eosinophilia. The serological results were monitored in some of the patients, confirming a loss of antibodies in all 20 patients studied.

CONCLUSIONS

Strongyloidiasis is a parasitic disease increasingly diagnosed in developed countries due to increased migratory flows from endemic areas. Often being asymptomatic, its diagnosis and treatment may prevent fatal outcomes, especially in immunocompromised patients.

Development of a rapid serological assay for the diagnosis of strongyloidiasis using a novel diffraction-based biosensor technology

BACKGROUND

Strongyloidiasis is a persistent human parasitic infection caused by the intestinal nematode, Strongyloides stercoralis. The parasite has a world-wide distribution, particularly in tropical and subtropical regions with poor sanitary conditions. Since individuals with strongyloidiasis are typically asymptomatic, the infection can persist for decades without detection. Problems arise when individuals with unrecognized S. stercoralis infection are immunosuppressed, which can lead to hyper-infection syndrome and disseminated disease with an associated high mortality if untreated. Therefore a rapid, sensitive and easy to use method of diagnosing Strongyloides infection may improve the clinical management of this disease.

METHODOLOGY/PRINCIPAL FINDINGS

An immunological assay for diagnosing strongyloidiasis was developed on a novel diffraction-based optical bionsensor technology. The test employs a 31-kDa recombinant antigen called NIE derived from Strongyloides stercoralis L3-stage larvae. Assay performance was tested using retrospectively collected sera from patients with parasitologically confirmed strongyloidiasis and control sera from healthy individuals or those with other parasitoses including schistosomiasis, trichinosis, echinococcosis or amebiasis who were seronegative using the NIE ELISA assay. If we consider the control group as the true negative group, the assay readily differentiated S. stercoralis-infected patients from controls detecting 96.3% of the positive cases, and with no cross reactivity observed in the control group These results were in excellent agreement (κ = 0.98) with results obtained by an NIE-based enzyme-linked immunosorbent assay (ELISA). A further 44 sera from patients with suspected S. stercoralis infection were analyzed and showed 91% agreement with the NIE ELISA.

CONCLUSIONS/SIGNIFICANCE

In summary, this test provides high sensitivity detection of serum IgG against the NIE Strongyloides antigen. The assay is easy to perform and provides results in less than 30 minutes, making this platform amenable to rapid near-patient screening with minimal technical expertise.

Update on immunologic and molecular diagnosis of human strongyloidiasis

Human strongyloidiasis is an intestinal parasitosis that may affect 100 million individuals. However, the prevalence rates of this infection may represent smaller values than the actual data, mainly due to difficulties in its diagnosis. The aim of this study was to update the immunological and molecular methods applied to the diagnosis of human strongyloidiasis. There is a great diversity of techniques used in the diagnosis of this parasitosis, such as immunofluorescence antibody test (IFAT), enzyme-linked immunosorbent assay (ELISA), immunoblotting, luciferase immunoprecipitation system (LIPS), dispstick and polymerase chain reaction (PCR), all with advantages and disadvantages, and with unique features for specific purposes. Considering the magnitude of strongyloidiasis and the importance of early diagnosis, due to the possibility of chronicity and hyperinfection, this study analyzes the different methods currently employed, and demonstrates the necessity of developing innovative methodologies, which also maintain diagnostic accuracy, particularly for regions with limited technological resources.

High prevalence and spatial distribution of Strongyloides stercoralis in rural Cambodia

Background

The threadworm, Strongyloides stercoralis, endemic in tropical and temperate climates, is a neglected tropical disease. Its diagnosis requires specific methods, and accurate information on its geographic distribution and global burden are lacking. We predicted prevalence, using Bayesian geostatistical modeling, and determined risk factors in northern Cambodia.

Methods

From February to June 2010, we performed a cross-sectional study among 2,396 participants from 60 villages in Preah Vihear Province, northern Cambodia. Two stool specimens per participant were examined using Koga agar plate culture and the Baermann method for detecting S. stercoralis infection. Environmental data was linked to parasitological and questionnaire data by location. Bayesian mixed logistic models were used to explore the spatial correlation of S. stercoralis infection risk. Bayesian Kriging was employed to predict risk at non-surveyed locations.

Principal Findings

Of the 2,396 participants, 44.7% were infected with S. stercoralis. Of 1,071 strongyloidiasis cases, 339 (31.6%) were among schoolchildren and 425 (39.7%) were found in individuals under 16 years. The incidence of S. stercoralis infection statistically increased with age. Infection among male participants was significantly higher than among females (OR: 1.7; 95% CI: 1.4–2.0; P<0.001). Participants who defecated in latrines were infected significantly less than those who did not (OR: 0.6; 95% CI: 0.4–0.8; P = 0.001). Strongyloidiasis cases would be reduced by 39% if all participants defecated in latrines. Incidence of S. stercoralis infections did not show a strong tendency toward spatial clustering in this province. The risk of infection significantly decreased with increasing rainfall and soil organic carbon content, and increased in areas with rice fields.

Conclusions/Significance

Prevalence of S. stercoralis in rural Cambodia is very high and school-aged children and adults over 45 years were the most at risk for infection. Lack of access to adequate treatment for chronic uncomplicated strongyloidiasis is an urgent issue in Cambodia. We would expect to see similar prevalence rates elsewhere in Southeast Asia and other tropical resource poor countries.

Data on the prevalence and distribution of Strongyloides stercoralis (threadworm) is scarce in many resource-poor countries. We carried out a cross-sectional study during the dry season among 2,396 rural Cambodians of all ages. We used a rigorous diagnostic approach, involving two stool samples per person and two examination techniques, namely, Koga agar plate culture and the Baermann method. We predicted the spatial distribution of S. stercoralis using Bayesian Kriging analysis. Almost half of the participants (44.7%) were infected with S. stercoralis. Of the S. stercoralis cases, 39.7% involved participants under 16 years old. S. stercoralis infection prevalence was significantly higher in males than in females. Participants younger than 10 years old had a lower risk of infection than did older participants. Furthermore, our study showed that toilet use could prevent threadworm infections by 39%. Infection prevalence in the province was negatively associated with rainfall and soil organic content and positively associated with land covered by rice fields. We conclude that access to adequate treatment for S. stercoralis must be addressed in Cambodia. Infection prevalence is likely to be similar in other countries of the region and the developing world.

Bacteriophage-fused peptides for serodiagnosis of human strongyloidiasis

Background

Strongyloidiasis, a human intestinal infection caused by the nematode Strongyloides stercoralis, is frequently underdiagnosed and although its high prevalence is still a neglected parasitic disease because conventional diagnostic tests based on parasitological examination (presence of Strongyloides larvae in stool) are not sufficiently sensitive due to the low parasitic load and to the irregular larval output. There is an urgent need to improve diagnostic assays, especially for immunocompromised patients with high parasitic load as consequence of self-infection cycle, which can disseminate throughout the body, resulting in a potentially fatal hyperinfection syndrome often accompanied by sepsis or meningitis.

Methods/Principal Findings

We have performed Phage Display technology to select peptides that mimic S. stercoralis antigens, capable of detecting a humoral response in patients with strongyloidiasis. The peptides reactivity was investigated by Phage-ELISA through different panels of serum samples. We have successfully selected five peptides with significant immunoreactivity to circulating IgG from patients' sera with strongyloidiasis. The phage displayed peptides C9 and C10 presented the highest diagnostic potential (AUC>0.87) with excellent sensitivity (>85%) and good specificity (>77.5%), suggesting that some S. stercoralis antigens trigger systemic immune response.

Conclusions/Significance

These novel antigens are interesting serum biomarkers for routine strongyloidiasis screenings due to the easy production and simple assay using Phage-ELISA. Such markers may also present a promising application for therapeutic monitoring.

Strongyloidiasis is one of the most neglected helminthic infections and can cause disseminated disease in immunocompromised hosts, which can be fatal. Given the unsatisfactory results of current parasitological and serological tests, there is a need for more efficient diagnostic tools. Therefore we have used phage display technology and bioppaning procedure to select sensitive and specific mimotopes ready to be used in immunodiagnostic tests. These mimotopes allows a cheap and fast clear-cut diagnosis of Strongyloides stercoralis infections. The field applicability of the assay using the phage clones obtained is really promising. The main advantage is that phage-based ELISA is the reproducible, simple, rapid and low-cost for production of recombinant antigens, and such tests may be of interest for massive screening in developing countries. Our results indicate that the mimotopes selected and tested here are potential biomarkers for the diagnosis of human strongyloidiasis.

Prevalence and risk factors of Strongyloides stercoralis in Takeo Province, Cambodia

Background

The threadworm Strongyloides stercoralis, the most neglected helminth, affects an estimated 30-100 million people worldwide. Information on S. stercoralis infection is scarce in tropical and sub-tropical resource poor countries, including Cambodia. We determined S. stercoralis infection prevalence and risk factors for infection in the general population in Southern Cambodia.

Methods

A cross-sectional study was carried out between January and April 2011 among 2,861 participants living in 60 villages of Takeo province, using Koga-agar plate culture, the Baermann technique and the Kato-Katz technique on a single stool sample.

Results

Eight intestinal helminth species were diagnosed. Hookworm (31.4%) and S. stercoralis (21.0%) occurred most frequently. Prevalence of S. stercoralis infection increased with age. In all age groups a higher prevalence was found among males than among females (OR: 1.7; 95% CI: 1.4 – 2.0; P < 0.001). Participants who had a latrine at home were significantly less frequently infected with S. stercoralis than those who did not (OR: 0.7; 95% CI: 0.4 – 0.8; P = 0.003). Muscle pain (OR: 1.3; 95% CI: 1.0 – 1.6; P = 0.028) and urticaria (OR: 1.4; 95% CI: 1.1 – 1.8; P = 0.001) were significantly associated with S. stercoralis infection.

Conclusions

S. stercoralis is highly prevalent among the general Cambodian population and should no longer be neglected. Access to adequate diagnosis and treatment is urgently needed.

Comparison of three immunoassays for detection of antibodies to Strongyloides stercoralis

Due to the limited sensitivities of stool-based microscopy and/or culture techniques for Strongyloides stercoralis, the detection of antibodies to this intestinal nematode is relied upon as a surrogate for determining exposure status or making a diagnosis of S. stercoralis infection. Here, we evaluated three immunoassays, including the recently released InBios Strongy Detect IgG enzyme-linked immunosorbent assay (ELISA) (InBios International, Inc., Seattle, WA), the SciMedx Strongyloides serology microwell ELISA (SciMedx Corporation, Denville, NJ), and the luciferase immunoprecipitation system (LIPS) assay performed at the National Institutes of Health (NIH), for their detection of IgG antibodies to S. stercoralis. A total of 101 retrospective serum samples, previously submitted for routine S. stercoralis antibody detection using the SciMedx assay, were also evaluated by the InBios and LIPS assays. The qualitative results from each assay were compared using a Venn diagram analysis, to the consensus result among the three assays, and each ELISA was also evaluated using the LIPS assay as the reference standard. By Venn diagram analysis, 65% (66/101) of the samples demonstrated perfect agreement by all three assays. Also, the numbers of samples considered positive or negative by a single method were similar. Compared to the consensus result, the overall percent agreement of the InBios, SciMedx, and LIPS assays were comparable at 87.1%, 84.2%, and 89.1%, respectively. Finally, the two ELISAs performed analogously but demonstrated only moderate agreement (kappa coefficient for the two assays, 0.53) with the LIPS assay. Collectively, while the two commercially available ELISAs perform equivalently, neither should be used independently of clinical evaluation to diagnose strongyloidiasis.

Usefulness of Strongyloides stercoralis serology in the management of patients with eosinophilia

Strongyloides stercoralis infection is being increasingly diagnosed out of endemic areas. The aim of this study is to evaluate the usefulness of S. stercoralis serology for the management of probable strongyloidiasis in patients presenting with eosinophilia. Overall, 147 patients were included, 89 (60.5%) patients had a positive S. stercoralis serology. Strongyloides stercoralis larvae were detected only in 15 (10.2%) patients. Twenty-eight patients had human immunodeficiency virus infection. Eighty patients received ivermectin 200 mcg/Kg/day for 2 days, and follow-up 6 months after treatment could be performed in 32 patients: 26 (81.3%) patients reached the response to treatment criteria (negative serology 6 months after treatment or when by enzyme-linked immunosorbent assay the optical density ratio of post-treatment to pre-treatment decreased to 0.6), and 11 (34.4%) patients fulfilled the cure criteria (negative serology 6 months after treatment). Strongyloides stercoralis serology is a useful diagnostic tool both in the diagnosis of probable strongyloidiasis and follow-up after treatment.

Strongyloides stercoralislarvae excretion patterns before and after treatment

The variability of larval excretion impedes the parasitological diagnosis ofStrongyloides stercoralisin infected individuals. We assessed the number of larvae excreted per gram (LPG) stool in 219 samples from 38 infected individuals over 7 consecutive days before and in 470 samples from 44 persons for 21 consecutive days after ivermectin treatment (200 μg kg−1BW). The diagnostic sensitivity of a single stool sample was about 75% for individuals with low-intensity infections (⩽1 LPG) and increased to 95% for those with high-intensity infections (⩾10 LPG). Doubling the number of samples examined per person increased sensitivity to more than 95%, even for low-intensity infections. There was no indication of a cyclic excretion of larvae. After treatment, all individuals stopped excreting larvae within 3 days. Larvae were not detected during any of the following 18 days (total 388 Baermann and 388 Koga Agar tests). Two stool samples, collected on consecutive days, are recommended in settings where low or heterogeneous infection intensities are likely. In this way, taking into account the possible biological variability in excretion, the efficacy of ivermectin treatment can be assessed as soon as 4 days after treatment.

Diagnostic accuracy of five serologic tests for Strongyloides stercoralis infection

Background

The diagnosis of Strongyloides stercoralis (S. stercoralis) infection is hampered by the suboptimal sensitivity of fecal-based tests. Serological methods are believed to be more sensitive, although assessing their accuracy is difficult because of the lack of sensitivity of a fecal-based reference (“gold”) standard.

Methods

The sensitivity and specificity of 5 serologic tests for S. stercoralis (in-house IFAT, NIE-ELISA and NIE-LIPS and the commercially available Bordier-ELISA and IVD-ELISA) were assessed on 399 cryopreserved serum samples. Accuracy was measured using fecal results as the primary reference standard, but also using a composite reference standard (based on a combination of tests).

Results

According to the latter standard, the most sensitive test was IFAT, with 94.6% sensitivity (91.2–96.9), followed by IVD-ELISA (92.3%, 87.7–96.9). The most specific test was NIE-LIPS, with specificity 99.6% (98.9–100), followed by IVD-ELISA (97.4%, 95.5–99.3). NIE-LIPS did not cross-react with any of the specimens from subjects with other parasitic infections. NIE-LIPS and the two commercial ELISAs approach 100% specificity at a cut off level that maintains ≥70% sensitivity.

Conclusions

NIE-LIPS is the most accurate serologic test for the diagnosis of S. stercoralis infection. IFAT and each of the ELISA tests are sufficiently accurate, above a given cut off, for diagnosis, prevalence studies and inclusion in clinical trials.

The diagnosis of Strongyloides stercoralis infection is usually made by finding larvae of the parasite in the feces. The larval output is orders of magnitude lower than, say, the egg output of Ancylostoma duodenale, therefore the sensitivity of conventional techniques is poor. Sensitivity is enhanced by specific techniques, but the infection can still be missed. Several serologic methods (Strongyloides antibody detection in blood) are considered more sensitive, but they have been assessed so far with fecal tests as the gold standard, which is obviously unsatisfactory considering, precisely, their suboptimal sensitivity. Using a bank of sera from patients surely infected, not infected or doubtful, we assessed the accuracy of five different serologic tests also using a composite reference standard, obtained by combining the results of different tests. The recently developed NIE-LIPS resulted virtually 100% specific, with sensitivity >80%. Two commercially available ELISA tests were also highly specific above a given cut-off. Cross reactions with other parasitic infections were rarer than in previous studies. In conclusion, serologic tests are accurate tools, both for diagnostic purposes and for prevalence studies. Whether or not they can also be reliable markers of cure is currently under study.

Diagnosis of human nematode infections

Many hundreds of millions of people throughout the world are infected by nematodes found in the intestine or tissues with a high prevalence in developing countries. Despite their frequency and morbidity, these infections, which may affect migrants and travelers, remain difficult to diagnosis even in developed countries. This is primarily due to the variety of clinical signs often associated with a lack of highly sensitive and specific diagnostic tools. Parasitological diagnosis is often difficult to achieve and can neither be applied during the pre-patent period nor for parasitic impasses. Serological diagnosis is frequently hampered by a lack of specificity due to cross-reaction with others helminthes. Molecular biology methods still require optimization. The diagnostic approach applied by a clinician of a suspected nematode infection is based on a vast set of data including patient history and way of life, clinical examination, non-specific biological tests and, when available, specific diagnostic tests.