Prevalence of strongyloidiasis and schistosomiasis among migrants: a systematic review and meta-analysis

BACKGROUND

Global migration from regions where strongyloidiasis and schistosomiasis are endemic to non-endemic countries has increased the potential individual and public health effect of these parasitic diseases. We aimed to estimate the prevalence of these infections among migrants to establish which groups are at highest risk and who could benefit from screening.

METHODS

We did a systematic review and meta-analysis of strongyloidiasis and schistosomiasis prevalence among migrants born in endemic countries. Original studies that included data for the prevalence of Strongyloides or Schistosoma antibodies in serum or the prevalence of larvae or eggs in stool or urine samples among migrants originating from countries endemic for these parasites and arriving or living in host countries with low endemicity-specifically the USA, Canada, Australia, New Zealand, Israel, and 23 western European countries-were eligible for inclusion. Pooled estimates of the prevalence of strongyloidiasis and schistosomiasis by stool or urine microscopy for larvae or eggs or serum antibodies were calculated with a random-effects model. Heterogeneity was explored by stratification by age, region of origin, migrant class, period of study, and type of serological antigen used.

FINDINGS

88 studies were included. Pooled strongyloidiasis seroprevalence was 12·2% (95% CI 9·0-15·9%; I² 96%) and stool-based prevalence was 1·8% (1·2-2·6%; 98%). Migrants from east Asia and the Pacific (17·3% [95% CI 4·1-37·0]), sub-Saharan Africa (14·6% [7·1-24·2]), and Latin America and the Caribbean (11·4% [7·8-15·7]) had the highest seroprevalence. Pooled schistosomiasis seroprevalence was 18·4% (95% CI 13·1-24·5; I² 97%) and stool-based prevalence was 0·9% (0·2-1·9; 99%). Sub-Saharan African migrants had the highest seroprevalence (24·1·% [95% CI 16·4-32·7]).

INTERPRETATION

Strongyloidiasis affects migrants from all global regions, whereas schistosomiasis is focused in specific regions and most common among sub-Saharan African migrants. Serological prevalence estimates were several times higher than stool estimates for both parasites. These data can be used to inform screening decisions for migrants and support the use of serological screening, which is more sensitive and easier than stool testing.

FUNDING

None.

Is Strongyloides seropositivity associated with diabetes mellitus? A retrospective case-control study in an East London NHS Trust

BACKGROUND

The association between diabetes and Strongyloides stercoralis remains controversial. We conducted a case-control study examining the association between diabetes and Strongyloides seropositivity in a large UK centre.

METHODS

Between January 2013 and October 2016, cases and controls were identified by positive and negative Strongyloides serology, respectively. Demographic, clinical and microbiological data were retrospectively collected. Multivariate logistic regression analysis was performed.

RESULTS

Over the study period, 532 samples were serologically tested for Strongyloides. After exclusion of duplicates and cases with missing data, 100 (22.3%; 95% CI 18.5-26.4%) out of 449 tested positive. Of seropositive cases, the mean age was 57 years (SD 16), 71 (71%) were male, 94 (94%) were migrants and 92 (92%) had eosinophilia.Univariate logistic regression analysis demonstrated a significant association between Strongyloides seropositivity and age (OR 1.04, 95% CI 1.02-1.05), male sex (OR 2.22, 95% CI 1.37-3.59), migration (OR 5.36, 95% CI 2.27-12.67), eosinophilia (OR 4.36, 95% CI 2.04-9.33) and diabetes (OR 3.52, 95% CI 2.19-5.66). In multivariate analysis, there remained a significant association between diabetes and Strongyloides seropositivity (OR 1.81, 95% CI 1.04-3.16).

CONCLUSIONS

We demonstrated a high rate of Strongyloides seropositivity in our East London cohort and a significant association with diabetes.

Screening of Strongyloides infection using an ELISA test in transplant candidates

OBJECTIVES

Hyperinfection or disseminated strongyloidiasis has been frequently reported after transplants and is related to high mortality. This study aimed to screen for strongyloidiasis using serological diagnoses in transplant candidates.

METHODS

An ELISA test was performed with filariform larvae of Strongyloides venezuelensis as a source of antigen.

RESULTS

In the serum from transplant candidates, anti-Strongyloides IgG antibodies were detected in 35/150 (23.3%) samples by soluble fractions in phosphate buffered saline (PBS), 31/150 (20.7%) samples by soluble fractions in Tris-HCl, 27/150 (18.0%) samples by membrane fractions in PBS and 22/150 (14.7%) samples by membrane fractions in Tris-HCl.

CONCLUSIONS

The present results suggest the ELISA test, ideally using soluble fractions of filariform larvae S. venezuelensis in PBS, as an additional strategy for the diagnosis of strongyloidiasis in transplant candidates.

High seroprevalence of Strongyloides stercoralis among individuals from endemic areas considered for solid organ transplant donation: A retrospective serum-bank based study

Background

Strongyloides stercoralis is a worldwide disseminated parasitic disease that can be transmitted from solid organ transplant (SOT) donors to recipients. We determined the serological prevalence of S. stercoralis among deceased individuals from endemic areas considered for SOT donation, using our institution’s serum bank.

Methodology

Retrospective study including all deceased potential donors from endemic areas of strongyloidiasis considered for SOT between January 2004 and December 2014 in a tertiary care hospital. The commercial serological test IVD-Elisa was used to determine the serological prevalence of S. stercoralis.

Principal findings

Among 1025 deceased individuals during the study period, 90 were from endemic areas of strongyloidiasis. There were available serum samples for 65 patients and 6 of them tested positive for S. stercoralis (9.23%). Only one of the deceased candidates was finally a donor, without transmitting the infection.

Conclusions

Among deceased individuals from endemic areas considered for SOT donation, seroprevalence of strongyloidiasis was high. This highlights the importance of adhering to current recommendations on screening for S. stercoralis among potential SOT donors at high risk of the infection, together with the need of developing a rapid diagnostic test to fully implement these screening strategies.

Strongyloidiasis is a neglected tropical disease caused by a parasite which is endemic in most parts of the world. It can cause a life-threatening disease among immunosuppressed individuals and can be transmitted from solid organ transplant donors to recipients. We retrospectively investigated the prevalence of strongyloidiasis among deceased individuals from endemic areas who were considered for solid organ transplant donation in our center, by performing a serological assay using our institution’s serum bank. We found a high prevalence of strongyloidiasis among these deceased candidates to donation, but only one of the six who tested positive was finally a donor, without transmitting the disease to recipients. Our results should encourage physicians to adhere to current guidelines which recommend active screening of strongyloidiasis in potential solid organ transplant donors from endemic areas who may be infected. There is a clear need for a rapid diagnostic test to fully implement systematic screening among these individuals.

Diagnostic performance of urinary IgG antibody detection: A novel approach for population screening of strongyloidiasis

The diagnosis of strongyloidiasis by coprological methods has a low sensitivity, underestimating the prevalence of Strongyloides stercoralis in endemic areas. Serodiagnostic tests for strongyloidiasis have shown robust diagnostic properties. However, these methods require a blood draw, an invasive and labor-intensive sample collection method, especially in the resource-limited settings where S. stercoralis is endemic. Our study examines a urine-based assay for strongyloidiasis and compares its diagnostic accuracy with coprological and serological methods. Receiver operating characteristic (ROC) curve analyses determined the diagnostic sensitivity (D-Sn) and specificity (D-Sp) of the urine ELISA, as well as estimates its positive predictive value and diagnostic risk. The likelihood ratios of obtaining a positive test result (LR+) or a negative test result (LR-) were calculated for each diagnostic positivity threshold. The urine ELISA assay correlated significantly with the serological ELISA assay for strongyloidiasis, with a D-Sn of 92.7% and a D-Sp of 40.7%, when compared to coprological methods. Moreover, the urine ELISA IgG test had a detection rate of 69%, which far exceeds the coprological method (28%). The likelihood of a positive diagnosis of strongyloidiasis by the urine ELISA IgG test increased significantly with increasing units of IgG detected in urine. The urine ELISA IgG assay for strongyloidiasis assay has a diagnostic accuracy comparable to serological assay, both of which are more sensitive than coprological methods. Since the collection of urine is easy and non-invasive, the urine ELISA IgG assay for strongyloidiasis could be used to screen populations at risk for strongyloidiasis in S. stercoralis endemic areas.

Transrenal DNA-based diagnosis of Strongyloides stercoralis (Grassi, 1879) infection: Bayesian latent class modeling of test accuracy

For epidemiological work with soil transmitted helminths the recommended diagnostic approaches are to examine fecal samples for microscopic evidence of the parasite. In addition to several logistical and processing issues, traditional diagnostic approaches have been shown to lack the sensitivity required to reliably identify patients harboring low-level infections such as those associated with effective mass drug intervention programs. In this context, there is a need to rethink the approaches used for helminth diagnostics. Serological methods are now in use, however these tests are indirect and depend on individual immune responses, exposure patterns and the nature of the antigen. However, it has been demonstrated that cell-free DNA from pathogens and cancers can be readily detected in patient’s urine which can be collected in the field, filtered in situ and processed later for analysis. In the work presented here, we employ three diagnostic procedures—stool examination, serology (NIE-ELISA) and PCR-based amplification of parasite transrenal DNA from urine–to determine their relative utility in the diagnosis of S. stercoralis infections from 359 field samples from an endemic area of Argentina. Bayesian Latent Class analysis was used to assess the relative performance of the three diagnostic procedures. The results underscore the low sensitivity of stool examination and support the idea that the use of serology combined with parasite transrenal DNA detection may be a useful strategy for sensitive and specific detection of low-level strongyloidiasis.

As international bodies focus efforts on control of the world’s neglected tropical diseases, the critical importance of accurate and sensitive diagnosis becomes a key factor. The problem arises when the infection load in a community is reduced to a level where the standard diagnostic methodologies are insufficiently sensitive to detect the residual infection in the community. There is a need to develop improved diagnostic strategies for many parasitic diseases. One of the more difficult to diagnose helminth parasites is the nematode Strongyloides stercoralis. We have introduced a new approach that detects parasite-specific cell free DNA in urine as a sensitive measure of parasite presence. In the work presented here, we compare the performance of parasitological, serological and urine/DNA-based diagnosis of S. stercoralis infection. Using a Bayesian Latent Class Analysis approach, we provide evidence for the enhanced utility of using both urine and blood for the diagnosis of this parasite.

Seroprevalence of Strongyloides stercoralis infection among HTLV-I infected blood donors in Barcelona, Spain: A cross-sectional study

Strongyloides stercoralis infection in patients with HTLV-I infection may lead to severe clinical manifestations. The aim of the present study is to determine the seroprevalence of S. stercoralis infection among blood donors who tested positive for HTLV-I infection. A cross-sectional study was performed at the Vall d'Hebron University Hospital (Barcelona, Spain) in 2016. Serum samples from HTLV-I positive patients diagnosed from 2008 to 2015 were retrieved from the Blood Bank, and S. stercoralis serology was performed. Thirty six serum samples from HTLV-I positive patients were retrieved from the Blood Bank. The blood samples came from 36 blood donors, and most of them were born in Latin America (75%), being Peru the most frequent country (11 participants). S. stercoralis serology was positive in one patient, corresponding to a prevalence of 2.8% (3.4% if we exclude donors coming from European countries, where the risk of S. stercoralis infection is highly unlikely).

Identification of antigenic proteins in Strongyloides stercoralis by proteomic analysis

Strongyloides stercoralis is an intestinal helminth that infects people worldwide. Hyperinfection or disseminated human strongyloidiasis can involve vital organs, leading to lethal outcomes. We analyzed immunoproteomics of antigenic spots, derived from S. stercoralis third-stage larvae and reacted with human strongyloidiasis sera, by two-dimensional gel electrophoresis and immunoblotting. Of 26 excised antigenic spots analyzed by liquid chromatography-electrospray ionization-tandem mass spectrometry, 20 proteins were identified. Most proteins were associated with enzymes involved in the metabolic process, energy generation, and oxidation-reduction. The proteins relate to promotion of worm development, cell division, cell signaling and transportation, and regulation of muscular contraction. Identification of antigenic proteins shows promise in helping to discover potential diagnostic protein markers or vaccine candidates for S. stercoralis infection.

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.

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.

Management of chronic strongyloidiasis in immigrants and refugees: is serologic testing useful?

We assessed the usefulness of serologic testing in monitoring strongyloidiasis in immigrants after treatment with two doses of ivermectin. An observational study was conducted in a group of Cambodian immigrants residing in Melbourne who were treated for strongyloidiasis and followed-up in a general practice setting. Two doses of ivermectin (200 microg/kg) were administered orally. Periodic serologic enzyme-linked immunosorbent assay testing was undertaken for up to 30 months after treatment. Antibody titers for Strongyloides sp. decreased in 95% (38 of 40) of the patients, 47.5% (19 of 40) had a decrease in optical density to less than 0.5, and 65% (26 of 40) reached levels consistent with a cure during the follow-up period. Serologic testing for Strongyloides sp. is a useful tool for monitoring a decrease in antibody levels after effective treatment. This testing should be carried out 6-12 months after treatment to ensure a sustained downward trend suggestive of cure.

Eosinophilic oophoritis: association with positive Strongyloides stercoralis serology and clinical response to ivermectin

BACKGROUND

Localized eosinophilic infiltration causing ovarian dysfunction is an unusual clinical problem.

CASE

We report a 16-year-old girl with abdominal pain, ovarian cysts, and biopsy-proven eosinophilic oophoritis, which resulted in right oophorectomy. Subsequently, a large cyst developed in the left ovary, causing abdominal pain that was worse at the time of her menses, and biopsy again showed numerous eosinophilic microabscesses. Unexpectedly, a parasite serology test to Strongyloides stercoralis was positive, although stool tests for ova and parasites were negative and the total IgE and total eosinophil count were normal. After treatment with ivermectin, the patient's abdominal pain resolved, the serologic antibody titers to S stercoralis returned to normal, and subsequent ultrasonographic evaluations showed involution of the large cyst in the remaining ovary.

CONCLUSION

Eosinophilic oophoritis is a new disorder of localized tissue eosinophilia.

Is there an association between positive Strongyloides stercoralis serology and diabetes mellitus?

The purpose of this study was to determine the frequency of association between positive Strongyloides stercoralis serology and diabetes mellitus. A total of 78 diabetic patients and 42 controls were evaluated. For a parasitological diagnosis, Baermann and Hoffman et al.'s methods were applied. The immunological diagnosis involved the indirect fluorescence antibody test, ELISA and Western blotting to detect IgG antibodies. The frequency of positive S. stercoralis serology in diabetics was 23% versus 7.1% in the control group (P<0.05). The odds ratio for diabetics was 3.9 (CI, 1.6-15.9, P<0.05). Diabetic patients with HbA(1c)< or =7 had a greater chance of testing negatively for S. stercoralis infection (OR: 1.5, P>0.05). Provided there are related cases of disseminated strongyloidiasis in diabetics and there is a higher frequency of asymptomaticity of the infection in this group, the immunological screening of these patients at risk could prevent severe and fatal outcomes of the disease.

Undiagnosed and potentially lethal parasite infections among immigrants and refugees in Australia

Intestinal parasite infections are a major cause of ill health in many resource-poor countries. This study compares the types and rates of these infections and their risk factors in recently arrived and long-term immigrants in Australia. Cross-sectional surveys of 127 East African and 234 Cambodian immigrants and refugees were undertaken in 2000 and 2002, respectively, to assess the burden of intestinal parasites and collect demographic information. Serum samples were assessed for eosinophilia and Strongyloides stercoralis and Schistosoma antibodies, and feces examined for ova, cysts, and parasites. Intestinal parasites were identified in 77/117 fecal samples from East African and in 25/204 samples collected from Cambodian participants. Eleven percent (14/124) of East Africans and 42% (97/230) of Cambodians had positive or equivocal serology for S stercoralis. Schistosoma serology was positive or equivocal in 15% (19/124) of East African participants. Potentially serious intestinal parasite infections are common among recent and longer term immigrants despite multiple visits to health care providers. Immigrants and refugees from high-risk countries would benefit from comprehensive health checks soon after resettlement.

Liquid chromatographic assay of ivermectin in human plasma for application to clinical pharmacokinetic studies

There is a need for an accurate, sensitive and selective high-performance liquid chromatography (HPLC) method for the quantitation of ivermectin in human plasma that separates the parent drug from metabolites. Ivermectin and the internal standard, moxidectin, were extracted from 0.2 ml of human plasma using Oasis HLB solid phase extraction cartridges. After extraction, fluorescent derivatives of ivermectin and moxidectin were made by reaction with trifluoroacetic anhydride and N-methylimidazole. Separation was achieved on a Alltech Ultrasphere C18 5mu column with a mobile phase composed of tetrahydrofuran-acetonitrile-water (40:38:22 v/v/v). Detection is by fluorescence, with an excitation of 365 nm and emission of 475 nm. The retention times of ivermectin and internal standard, moxidectin are approximately 24.5 and 12.5 min, respectively. The assay is linear over the concentration range of 0.2-200 ng/ml of ivermectin in human plasma (r = 0.9992, weighted by 1/concentration). Recoveries of ivermectin are greater than 80% at all concentrations. The analysis of quality control samples for ivermectin 0.2, 25, and 200 ng/ml demonstrated excellent precision with coefficient of variation of 6.1, 3.6 and 2.3%, respectively (n = 6). The method is accurate with all intra-day (n = 6) and interday (n = 12) mean concentration within 10% of nominal values at all quality control sample concentrations. Storage stability for 30 days at -80 degrees C and after three freeze-thaw cycles are within acceptable limits. The method separates ivermectin from multiple less and more polar unidentified metabolites. This method is robust and suitable for clinical pharmacokinetic studies. The analytical procedure has been applied to a pharmacokinetic study of ivermectin in healthy volunteers and to the analysis of plasma specimens from patients with disseminated strongyloidiasis.

Impairment of host immune response against strongyloides stercoralis by human T cell lymphotropic virus type 1 infection

A large-scale study was undertaken to clarify the prevalence rate of strongyloidiasis in Okinawa, Japan and to evaluate the relationship between strongyloidiasis and infection with human T cell lymphotropic virus type 1 (HTLV-1). The prevalence rate of Strongyloides stercoralis and HTLV-1 infection were 6.3% and 14.0%, respectively. Among 2,185 patients more than 50 years of age, the rate of S. stercoralis infection was significantly higher in patients with HTLV-1 infection compared with patients without HTLV-1 infection. In 252 patients treated with ivermectin, serum IgE levels and peripheral eosinophil counts were significantly lower in HTLV-1 co-infected patients compared with patients without HTLV-1 infection. In addition, the anthelmintic effect was significantly lower in patients with HTLV-1 infection compared with patients without HTLV-1 infection. Our prospective study demonstrated a prevalence rate for strongyloidiasis and HTLV-1 infections, and clearly demonstrated that co-infection with HTLV-1 impaired the immune response against S. stercoralis.

Seroepidemiology of strongyloidiasis in the Peruvian Amazon

A stool and serosurvey for Strongyloides stercoralis was conducted in a community in the Peruvian Amazon region. Strongyloidiasis stercoralis was identified in the stool of 69 (8.7%) of 792 participants. Six hundred nine sera were tested using by an enzyme-linked immunosorbent assay (ELISA), which had a sensitivity of 92% and a specificity of 94%; 442 (72%) were positive. In multivariable logistic regression models, having S. stercoralis in stool was associated with hookworm in the same specimen (odds ratio [OR] = 4.44, 95% confidence interval [CI] = 2.02-9.79), occasionally or never wearing shoes (OR = 1.89, 95% CI = 1.10-3.27), and increasing age (OR = 1.012 for each one-year increase, 95% CI = 1.00-1.03). Similarly, occasionally or never wearing shoes (OR = 1.54, 95% CI = 1.01-2.37) and increasing age (OR = 1.04 for each one-year increase, 95% CI = 1.02-1.06) were associated with an increased risk of a positive S. stercoralis ELISA result. The ELISA had a negative predictive value of 98% and is an excellent screening test for strongyloidiasis.

Strongyloides hyperinfection presenting as acute respiratory failure and gram-negative sepsis

STUDY OBJECTIVES

Disseminated strongyloides is a rarely reported phenomenon and occurs in immunosuppressed patients with chronic Strongyloides stercoralis infection. Typically, patients present with pulmonary symptoms but subsequently acquire Gram-negative sepsis. Several cases have been noted in Minnesota, and their presentation, diagnostic evaluation, and clinical outcomes were reviewed.

DESIGN

A retrospective chart review was conducted of complicated strongyloides infections from 1993 to 2002 in Minneapolis and St. Paul, MN. Cases were identified by reviewing hospital microbiology databases.

SETTING

Metropolitan hospitals with large immigrant populations.

RESULTS

Nine patients, all of Southeast Asian heritage, were identified. Eight patients immigrated to the United States > or = 3 years prior to acute presentation. All patients were receiving antecedent corticosteroids; in five patients, therapy was for presumed asthma. Absolute eosinophil counts > 500/microL occurred in only two patients prior to steroid initiation. Eight patients presented with respiratory distress, and Gram-negative sepsis developed in four patients. Four patients had evidence of right-heart strain on ECG or echocardiography at the time of presentation. Three patients died; all had eosinophil counts of < 400/microL.

CONCLUSIONS

Serious complications, including death, may occur in patients with chronic strongyloides infection treated with corticosteroids. Strongyloides hyperinfection usually presents as acute respiratory failure and may initially mimic an asthma exacerbation or pulmonary embolism. Southeast Asian patients presenting with new-onset "asthma," acute respiratory distress, and/or Gram-negative sepsis should undergo evaluation to exclude strongyloides infection.

Strongyloidiasis: A review of the evidence for Australian practitioners

OBJECTIVE

To summarise the available evidence concerning the prevalence, clinical manifestations, diagnosis and management of strongyloidiasis in Northern Australia.

METHODS

We searched Medline, Clinical Evidence and the Cochrane Library using MeSH terms and text words 'strongyloides OR strongyloidiasis'. For Australian studies we included text words '(parasite* OR parasitic OR helminth*) AND Australia*'. We examined references contained in retrieved studies or identified from direct contact with researchers. Studies consistent with our objective that described their methods were eligible for inclusion.

RESULTS

The prevalence in some tropical Aboriginal communities is high. Infection can be asymptomatic, cause a range of clinical syndromes or death. It may become chronic. Infected patients are at risk of developing severe disseminated disease particularly with immune compromise. There is little information about the relative frequency of different clinical outcomes. Available diagnostic tools are imperfect. Stool examination has a low sensitivity. Serology may have a low specificity in high prevalence populations and has not been evaluated in Aboriginal populations. Antihelmintic drugs are relatively safe and effective. Community programs based on treatment of stool-positive cases have been associated with a reduced prevalence of strongyloidiasis. We found no studies examining alternative public health interventions.

CONCLUSION

There is a high prevalence in many Aboriginal communities. Strongyloides infection should be excluded prior to commencing immunosuppressive therapies in patients from endemic areas. Further studies examining the public health impact of strongyloidiasis, the role of the enzyme-linked immuno-sorbent assay serological test and population-based approaches to management of the disease in endemically infected Australian populations are needed.

Disseminated strongyloidiasis successfully treated with extended duration ivermectin combined with albendazole: a case report of intractable strongyloidiasis

We describe a patient with an overlapping syndrome disseminated strongyloidiasis and gram-negative sepsis. She was previously treated with albendazole 400 mg/day 14 days before admission without success. This admission, she was treated with a combination of oral ivermectin (injectable solution form), with a dosage of 200-400 microg/kg/day, and albendazole for 14 days. Strongyloides larvae disappeared from the stool by day 4 and from the sputum by day 10. No side effects were encountered during hospitalization or at the 1-month follow-up visit.

Enhanced survival of rats concurrently infected with Trypanosoma brucei and Strongyloides ratti

The interaction between the blood protozoan parasite, Trypanosoma brucei and the gastrointestinal nematode parasite, Strongyloides ratti was studied in outbred white albino rats. Rats were grouped and given either single infection with T. brucei or S. ratti or concurrently infected with both parasites. Blood parasitaemia and packed cell volume, faecal egg/larva output, adult worm burden and survivability were monitored in order to assess the interactive effects of the infections. All trypanosome-infected rats became parasitaemic within 1 week of infection but surprisingly parasitaemia was higher in the single than concurrently infected group of rats. In addition all animals with single T. brucei infection had died by 14 days after the infection, whereas animals with concurrent infection were still alive by day 28 after the infection when the experiment was terminated. Concurrent infection resulted in significant increase in daily S. ratti egg/larval output in faeces (P < 0.01), but lesser number of adult worms were recovered from the intestine of sacrificed rats on day 8 post-infection. Taken together these results suggest that T. brucei and S. ratti interact in a manner that ameliorates their pathogenic effects resulting in a decrease in the level of parasitaemia and intestinal worm burden and in increased life span of the infected rats. These results differ from the classical immunosuppressive attributes of T. brucei and the results are discussed in the context of the possible immune responses that might have contributed to this outcome and the potential significance of the findings in alternative control method of trypanosomosis.

Localisation and distribution of Wuchereria bancrofti antigens recognised by antisera from tropical pulmonary eosinophilia and from individuals with intestinal helminths

Serological analyses of sera from patients with a typical picture of filarial tropical pulmonary eosinophilia (TPE) and sera from patients from a region non-endemic for filariasis harbouring intestinal helminths, as Ascaris lumbricoides and Strongyloids stercoralis, revealed equally high titers of IgG4, usually considered diagnostic for filariasis. Ultrathin sections of adult worms of W. bancrofti embedded in the hydrophilic resin L.R. White were incubated with sera from patients with a typical picture of filarial tropical pulmonary eosinophilia (TPE) and sera from patients of a region that was non-endemic for filarial TPE but endemic for intestinal helminths. Both groups had a similar pattern of labelling, except that the labelling intensity was higher with the sera of patients with filarial TPE. The present study indicates relevant epitopes recognised by sera from TPE-patients and also individuals with intestinal helminths in all tissues of adult and intra-uterine microfilaria of W. bancrofti, instead of being localised in a specific nematode region. These findings suggest that people from areas not endemic for filariasis, but who harbour intestinal helminths, also share antifilarial antibodies in their serum that recognise antigens of adult worms and intrauterine microfilaria of W. bancrofti.

Persistent infection with Strongyloides venezuelensis in the Mongolian gerbil (Meriones unguiculatus)

To examine the fate of Strongyloides venezuelensis. Mongolian gerbils (Meriones unguicalatus) were orally infected with 1,000 L3 larvae per animal. Altogether, 50 gerbils divided into 5 groups of 10 each were monitored for a period of 570 days to document the kinetics of faecal egg output, adults worm population, morphological development, fecundity, and hematological changes including peripheral blood eosinophilia. This study chronicled a life long parasitism of S. venezuelensis in the gerbil host, and showed that S. venezuelensis infection was quite stable throughout the course of infection and the worms maintained their normal development as evidenced by their body dimension. A progressive loss of body condition of the infected gerbils was observed as the level of infection advanced. However, no detectable pathological changes were observed in the gastrointestinal tract. The present findings indicate that an immunocompetent host, such as the Mongolian gerbil, can serve as a life long carrier model of S. venezuelensis if the worms are not expelled within 570 days after infection.

[Immunodiagnosis of Strongyloides stercoralis infections in Chile using ELISA test]

BACKGROUND

Strongyloides stercoralis is a world wide distributed small intestinal nematode parasite. In immunocompetent individuals S stercoralis can produce asymptomatic infections or a moderate clinical picture of diarrhea, some cases become chronic. In immunocompromised patients, a disseminated disease may appear, sometimes fatal. In Chile, there is little epidemiological information about S stercoralis infections and appropriate diagnostic techniques are usually not used.

AIM

To evaluate the yield of an ELISA test for the diagnosis of strongyloidiasis in Chilean patients.

MATERIAL AND METHODS

Ten serum samples from patients with S stercoralis infections confirmed by a positive stool examination, 66 samples from individuals with other infections by tissue helminthes (24 toxocariasis, 15 trichinellosis, 11 hydatidosis, 12 fascioliasis and 4 cysticercosis), 13 samples from subjects with autoimmune diseases and 49 samples from apparently healthy individuals with a normal eosinophil count, were studied. ELISA antigen was prepared using a filariform larval extract obtained from a murine species of Strongyloides, maintained in laboratory animals.

RESULTS

Using 0.33 optical density units as a cut off value, 9 of 10 sera of S stercoralis infected individuals, had a positive ELISA test. No cross reactions were observed with sera of patients with other helminthic infections, autoimmune diseases or in healthy individuals. Thus, specificity, positive and negative predictive values were 100%.

CONCLUSIONS

The results obtained are similar with those found by other investigators. ELISA test for strongyloidiasis is a useful tool for the diagnosis of clinical cases and for seroepidemiological studies of this nematode infection in Chile.

HTLV-1 decreases Th2 type of immune response in patients with strongyloidiasis

Eosinophils, immunoglobulin (Ig)E and cytokines have important roles in defence mechanisms against helminths. In this study, the influence of HTLV-1 infection, characterized by a Th1 type of immune response, was evaluated on the cytokine pattern and parasitic specific IgE response in patients with strongyloidiasis. Patients were divided into four groups: strongyloidiasis without HTLV-1 infection, strongyloidiasis with HTLV-1, HTLV-1 without strongyloidiasis and controls without either helminth infection or HTLV-1. The cytokine profile was determined in supernatants of mononuclear cells stimulated with Strongyloides stercoralis crude antigen and the parasite specific IgE was measured by ELISA. Patients coinfected with HTLV-1 had higher levels of interferon (IFN)-gamma and interleukin (IL)-10 (P < 0.05) and lower levels of IL-5 and IgE (P < 0.05) than patients with strongyloidiasis without HTLV-1. There was an inverse relationship between IFN-gamma and IL-5 (P = 0.01; rs = - 0.37) and between IFN-gamma and parasite specific IgE (P = 0.01; rs = - 0.39), and a direct relationship between IFN-gamma and IL-10 (P = 0.04; rs = 0.35). These data show that coinfection with HTLV-1 decreases IL-5 and IgE responses in patients with strongyloidiasis consistent with a relative switch from Th2 to Th1 response. Immunological responses such as these are important in the control of this helminthic infection.

Study of soluble adhesion molecules in some intestinal and tissue helminthes

Soluble adhesion molecules namely soluble intercellular adhesion molecule-1 (sICAM-1) and soluble E-selectin (sELAM-1) were assayed in hydatid patients with or without complications. It was found that sICAM-1 was significantly increased in patients with hydatid cysts as compared to the control group. In lymphoedemic filariasis cases both sICAM-1 and sELAM-1 showed highly significant increase more than the control group. However, non of both soluble adhesion molecules were significantly elevated in patients with ascariasis, hymenolepiasis, heterophyiasis and strongyloidiasis as compared to controls. The results indicated that SICAM-1 & S ELAM-1 are useful markers for hydatidosis and filariasis, but not for ascariasis, hymenolepiasis, heterophyiasis and strongyloidiasis

High circulating proviral load with oligoclonal expansion of HTLV-1 bearing T cells in HTLV-1 carriers with strongyloidiasis

Adult T cell leukemia (ATLL) develops in 3 - 5% of HTLV-1 carriers after a long period of latency during which a persistent polyclonal expansion of HTLV-1 infected lymphocytes is observed in all individuals. This incubation period is significantly shortened in HTLV-1 carrier with Strongyloides stercoralis (Ss) infection, suggesting that Ss could be a cofactor of ATLL. As an increased T cell proliferation at the asymptomatic stage of HTLV-1 infection could increase the risk of malignant transformation, the effect of Ss infection on infected T lymphocytes was assessed in vivo in HTLV-1 asymptomatic carriers. After real-time quantitative PCR, the mean circulating HTLV-1 proviral load was more than five times higher in HTLV-1 carriers with strongyloidiasis than in HTLV-1+ individuals without Ss infection (P<0.009). This increased proviral load was found to result from the extensive proliferation of a restricted number of infected clones, i.e. from oligoclonal expansion, as evidenced by the semiquantitative amplification of HTLV-1 flanking sequences. The positive effect of Ss on clonal expansion was reversible under effective treatment of strongyloidiasis in one patient with parasitological cure whereas no significant modification of the HTLV-1 replication pattern was observed in an additional case with strongyloidiasis treatment failure. Therefore, Ss stimulates the oligoclonal proliferation of HTLV-1 infected cells in HTLV-1 asymptomatic carriers in vivo. This is thought to account for the shortened period of latency observed in ATLL patients with strongyloidiasis. Oncogene (2000) 19, 4954 - 4960

Coinfection by Strongyloides stercoralis in blood donors infected with human T-cell leukemia/lymphoma virus type 1 in São Paulo City, Brazil

The frequency of coinfection with Strongyloides stercoralis and human T-cell leukemia/lymphoma virus type 1 (HTML-1) was determined in 91 blood donors examined at the blood bank of a large hospital in São Paulo city, Brazil. As control group 61 individuals, not infected by HTLV-1, were submitted to the same techniques for the diagnosis of S. stercoralis infection. In HTLV-1 infected patients the frequency of S. stercoralis infection was 12.1%; on the other hand, the control group showed a frequency significantly lower of S. stercoralis infection (1.6%), suggesting that HTLV-1 patients should be considered as a high risk group for strongyloidiasis in São Paulo city.

Hypolipemia associated with the wasting condition of rabbits infected with Strongyloides papillosus

Rabbits develop a wasting condition in the intestinal stage of Strongyloides papillosus infection. Serum inflammatory cytokine and lipid profiles were investigated in five rabbits infected with S. papillosus and five uninfected pair-fed controls to ascertain whether the disease is inflammatory cytokine-mediated cachexia. Tumor necrosis factor alpha (TNF alpha) was detected in one infected animal at Day 7 after infection. Interleukin (IL)-1 was detected in three infected, and one control, animals at Day 28. IL-6 remained unchanged in both the groups. Infected animals developed hypolipemia, including hypotriglyceridemia in the intestinal stage of infection. Control animals lost body weight in the same manner as the infected animals, but had elevated cholesterols and phospholipids with normal triglyceride concentrations. The results suggested that the wasting condition has no association with cachexia induced by TNF alpha. IL-1 or IL-6, and that hepatic function for lipid synthesis is affected during the intestinal stage of S. papillosus infection.

Parasitological and immunological diagnoses of strongyloidiasis in immunocompromised and non-immunocompromised children at Uberlândia, State of Minas Gerais, Brazil

Parasitological and immunological diagnoses were part of a study conducted among 151 children, 83 immunocompromised (IC) and 68 non-immunocompromised (non-IC) aged from zero to 12, seen at the University Hospital, Universidade Federal de Uberlândia, State of Minas Gerais, Brazil, from February, 1996, to June, 1998. Three fecal samples from each child were analyzed for the parasitological diagnosis by Baermann-Moraes and Lutz methods. The immunological diagnosis to detect IgG and IgM antibodies was carried out by the indirect immunofluorescence antibody test (IFAT) with cryo-microtome sections of Strongyloides stercoralis and Strongyloides ratti larvae as antigens and by the ELISA test with an alkaline extract of S. ratti as the antigens. Of the 151 children 5 (3.31%) were infected with larvae of S. stercoralis (2 cases IC, 2.41%, and 3 cases non-IC, 4.41%). The IFAT-IgG detected 7 (8.43%) serum samples positive among IC, and 2 (2.94%) cases among non-IC. The ELISA-IgG test detected 10 (12.05%) serum samples positive among IC, and 1 (1.47%) case among non-IC. The IFAT-IgM detected 6 (7.22%) positive cases among IC, and 3 (4.41%) cases among non-IC. ELISA-IgM test detected 10 (12.05%) positive cases among IC, and 3 (4.41%) cases among non-IC. It was concluded that the immunological tests can help in the diagnosis of strongyloidiasis in immunocompromised children.

Interferon-gamma and interleukin-4 responses in relation to serum IgE levels in persons infected with human T lymphotropic virus type I and Strongyloides stercoralis

Possible immunologic interaction between infection with human T lymphotropic virus type 1 (HTLV-1), a retrovirus, and the intestinal parasite Strongyloides stercoralis was investigated in persons infected with one or both agents. This was done by examining the cytokine responses of peripheral blood mononuclear cells (PBMC) to mitogens and Strongyloides antigen. PBMC of subjects infected with HTLV-1 spontaneously produced interferon (IFN)-gamma with levels that correlated inversely with serum IgE levels. HTLV-1-infected subjects also had poor interleukin (IL)-4 responses to mitogenic stimulation, unlike persons without HTLV-1 infection. It is postulated that the IFN-gamma produced by activated T cells in some HTLV-1-infected persons acts to down-regulate IL-4 with consequent reduction of serum IgE levels. The impaired IgE responses and other effects of IL-4 down-regulation may be contributing factors to more severe disease and impaired response to treatment of strongyloidiasis in some HTLV-1-infected persons.

[Strongyloides stercoralis infection in patients with bronchial obstructive pathology]

Strongyloides stercoralis infection was hardly seen in Spain until a few years ago but has recently been shown to be fairly common in some geographic areas. In the respiratory tract this germ can cause acute bronchospasms that make diagnosis difficult, particularly in patients with underlying bronchial disease. To determine if curing S. stercoralis infection is accompanied by clinical and functional improvement in patients with bronchial obstruction, we studied the evolution of 22 infected patients: 11 with no bronchopulmonary disease and 11 with chronic airway obstruction or asthma. The following variables were assessed in both groups at the moment of diagnosis of infection and four months after cure: levels of eosinophils and total serum IgE, respiratory symptoms, steroid doses and spirometric parameters. After four months we observed a significant decrease in eosinophil (16 versus 5%) and IgE (1,600 versus 770 IU/ml) levels in both groups. The number of bronchospasms and daily steroid doses required decreased in the group with bronchial disease. No significant differences were seen in spirometric parameters, however. The improvement in respiratory symptoms, blood parameters and need for medication leads us to believe that airway inflammation decreases after the infection has been eradicated, in spite of the lack of improvement in bronchial obstruction.

[Strongyloides infections in former prisoners of war in South-East Asia in the second World War; additional information from serological diagnosis]

OBJECTIVE

To analyse the efficacy of ELISA serology in patients with Strongyloides infection acquired during World War II and maintained through repeated autoinfection.

DESIGN

Descriptive.

SETTING

Laboratory of Parasitology, Faculty of Medicine, Leiden, the Netherlands.

METHODS

Parasitological and clinical data on 193 ex-prisoners of war (South-east Asia) were presented previously (1990) by Verburg and De Geus. ELISA using L-3 S. ratti antigen was carried out with sera of these patients and the results were compared with those of repeated stool examinations using Baermann's method.

RESULTS

All subjects harbouring larvae in repeated stool examinations (26) were positive in serology. In 21 out of 167 patients in whom no larvae could be demonstrated, specific antibodies were detected. Anamnestic information together with data on eosinophilia and IgE levels suggested that the majority of these subjects were actually infected. The serological prevalence of infection with Strongyloides stercoralis was 33% for those imprisoned in Burma and 4% for those who were prisoners of war in the former Netherlands East Indies.

CONCLUSION

In the group of subjects studied, in whom Strongyloides infection was apparently maintained through a process of autoinfection for a period of over 40 years, serology appears a sensitive and specific diagnostic tool. Larvae could be detected in no more than 26 out of 47 serologically positive subjects.

Sudden death of calves by experimental infection with Strongyloides papillosus. III. Hematological, biochemical and histological examinations

Nine calves infected percutaneously with graded doses of Strongyloides papillosus (SPL) were examined for hematological, biochemical and histological changes during the infection. Six of the calves infected with the highest larval doses died suddenly and the three calves given lower doses survived. No changes were observed in blood cell counts except for a transient eosinophilia. Parameters of the blood coagulation system and blood gas remained normal. A decrease in blood glucose was observed in four of the calves that died after the prepatent period of the parasite. However, endotoxic shock could be ruled out as a cause of death because of normal platelet counts, no intravascular coagulation and low levels of serum endotoxin. A transient increase of creatine kinase was observed in three of the calves that died; however, myocardial infarction or myocarditis were not observed. No lesions were observed except for minor inflammatory changes in the lungs and slight cellular infiltrations in the heart. In the absence of any consistent hematological, biochemical or histological changes in the calves that died, the present study failed to demonstrate mechanisms underlying sudden death due to SPL infection.

A patient with eosinophilia, hypoalbuminemia and abdominal pain

Strongyloides stercoralis infections frequently present with eosinophilia and abdominal pain. Since the gastrointestinal symptoms are non-specific, only 15 percent of these patients are correctly considered to have an infectious enteritis or intestinal parasite. In fact, the initial diagnosis is peptic ulcer disease in most patients. The clinical course may be indolent, or patients may develop a sudden catastrophic illness, particularly following the administration of corticosteroids.

Seroepidemiology of Strongyloides infection in the Southeast Asian refugee population in Canada

As part of a screening and treatment program for intestinal parasite infections offered to newly arrived Southeast Asian refugees in Canada between July 1982 and February 1983, a total of 232 sera were tested for Strongyloides infection using an enzyme-linked immunosorbent assay (immunoglobulin G). These results were compared with coprologic results and eosinophil counts. The seroprevalence was 76.6% (131 of 171) among Kampucheans, 55.6% (15 of 27) among Laotians, and 11.8% (4 of 34) among Vietnamese. A statistically significant relation (p less than 0.001) was found between Strongyloides serology and Strongyloides infection on stool examination (prevalence, 24.7%) among Kampucheans. Eosinophilia (greater than or equal to 10%) was found to be significantly associated with both infection measures. Using coprologic results as the "gold standard," the properties of the serologic test were estimated to be: sensitivity (95%), specificity (29%), positive predictive value (30%), and negative predictive value (95%). These estimates should be regarded as minimal values, as stool examination for Strongyloides infection can be an unreliable diagnostic reference. Further evaluation of the discrepancies observed between coprologic and serologic testing is required to determine the usefulness of these tests in epidemiologic studies.

A serological test for the diagnosis of Strongyloides antibodies in ex Far East Prisoners of War

This paper gives the results of an ELISA test for Strongyloides stercoralis antibodies in a group of 436 ex Far East Prisoners of War (FEPOWs). Antigen was obtained from third-stage larvae of Strongyloides cebus. Sensitivity of the test is 97%, with a specificity of 99%. The test is being investigated further as regards cross-reactions with other helminths, but initial results look promising.

Eosinophilia as a marker for chronic strongyloidiasis--use of a serum ELISA test to detect asymptomatic cases

In a previously published survey of 602 former Far East prisoners of the 2nd World War (FEPOWs), 88 (15%) were found to have Strongyloides stercoralis infections. A further 25 (4.2%) had significant blood eosinophilia for no obvious parasitological or other medical cause. We have reinvestigated this latter group several years (range nine to 19 years) later, using a recently developed serum ELISA test as well as other standard parasitological procedures. Of the 11 who were still alive and traceable five (45%) were diagnosed as having strongyloidiasis. Eosinophilia in high risk groups such as former FEPOWs is very suggestive of Strongyloides infections. The serum ELISA test appears to be a useful, sensitive and specific screening test for this diagnostically difficult infection.

[Role of prolactin in changes of parasitism induced by lactation]

In order to establish the role played by prolactin in lactation during the evolution of Strongyloides ratti in the female rat, the authors tried to reproduce the effects of this physiological state by treatment with sulpiride (substituted benzamide), of which the prolactinogenic effect is intense in the female rat. Low doses partially reproduced the effects of lactation on parasitism by diminishing its intensity and delaying the onset of rejection, although without preventing it. The pharmacological action of sulpiride, which acts by blocking the dopamine receptors, explains why only low doses are active and why their action is limited to the onset of parasitism. This experiment lends weight to the hypothesis that prolactin plays a fundamental role in modifications of the evolution of Strongyloides ratti during lactation.

[Inhibition of Plasmodium berghei in rats infested with Strongyloides ratti or Trichinella spiralis; role of high blood corticosterone in reaction to the development of helminths]

The plasma corticosterone induced in the rat by the development of Strongyloides ratti or Trichinella spiralis reaches a sufficient level of intensity to determine reticulocytopenia. The latter is linked chronologically to the inhibition of parasitemia in Plasmodium berghei, which occurs when this protozoa develops at the same time as the Nematodes, and seems to be the causal factor. This hypothesis may be verified by replacing the helminths with the corticotropic action of A.C.T.H. which causes a decrease in the number of reticulocytes.

Experimental disseminated strongyloidiasis in Erythrocebus patas. I. Pathology

Fatal disseminated disease was induced in ten patas monkeys infected with two Southeast Asian strains of Strongyloides stercoralis. While some animals died within 6 weeks after infection, others controlled their infections until placed on high doses of corticosteroids. Larvae were first noted in the stools 11-20 days after transcutaneous exposure to filariform larvae. Daily larval counts tended to increase as the infections progressed, but the number of larvae in the stool was not predictive of whether a monkey would control his infection or succumb to fatal disease. Hyperinfection was confirmed in the six monkeys in which counts were made of the adult female parasites in the duodenum at postmortem, as well as by pathologic findings in all animals. Clinical signs of disease were vague until dyspnea induced by terminal pulmonary hemorrhage occurred. Eosinophilia and/or basophilia were noted intermittently in some infections. Severe necrotizing duodenitis, colitis, and pulmonary hemorrhage were the most conspicuous postmortem findings. Hyperinfection has been predictably induced in a cercopithecoid monkey for the first time; a species which may lend itself to further investigations into the pathogenesis of disseminated strongyloidiasis .