High Efficacy of Ivermectin for Strongyloidiasis Treatment

Infection with Strongyloides stercoralis is often asymptomatic but can be life-threatening in immunocompromised patients, which can be prevented by ivermectin (IVM) treatment. The efficacy of IVM has been reported to have lessened over time in some regions as a consequence of prolonged use and mass treatment campaigns. Ivermectin has been used in Thailand for more than a decade; therefore, we investigated the efficacy of a single dose (200 µg/kg) of IVM against in asymptomatic strongyloidiasis in northeastern Thailand. Fecal samples were collected before and 2 weeks after treatment and were analyzed for the presence of Strongyloides using a modified agar plate culture and the formalin-ethyl acetate concentration technique. Our results showed that single-dose IVM treatment successfully eliminated S. stercoralis infection in asymptomatic individuals in the endemic area with a 100% cure rate, indicating the high efficacy of IVM treatment in strongyloidiasis in northeast Thailand.

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

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

Preventive chemotherapy for the control of strongyloidiasis in school-age children: Estimating the ivermectin need

BACKGROUND

Strongyloides stercoralis is a soil-transmitted helminth (STH) that affects approximately 600 million people worldwide. Interventions targeting S. stercoralis have not been implemented yet. Specific treatment (ivermectin) could be included in already ongoing preventive chemotherapy (PC) campaigns targeting other STHs. The aim of this study was to estimate the quantity of ivermectin needed for an integrated STH/S. stercoralis control program.

METHODODOLOGY/PRINCIPAL FINDINGS

Our study estimates the number of school- age children (SAC) (the main focus of STH deworming campaigns) in need of PC with ivermectin. The normal approximation of the binomial distribution was adopted to calculate the hypothetical prevalence distribution in each endemic country. Considering prevalence thresholds for PC equal to 10%, 15%, and 20%, we estimated the number of SAC in need of treatment. We adjusted the estimates accounting for ivermectin distributed in lymphatic filariasis and onchocerciasis elimination programs and excluded from our calculation areas where Loa loa is endemic. The global number of SAC that should be targeted in PC campaigns was estimated at 283.9 M (95% CI: 163.4-368.8), 207.2 M (95% CI: 160.9-380.7), and 160.7 M (95% CI: 86.6-225.7) when the threshold for intervention was set to 10%, 15%, and 20%, respectively. India, China, Indonesia, Bangladesh, and Nigeria accounted for about 50% of the global SAC would have to be covered by PC intervention.

CONCLUSIONS/SIGNIFICANCE

Our analysis may support endemic countries to evaluate the ivermectin quantity needed for integrating strongyloidiasis in the existing STH programs. These estimates might also show to generic drug manufacturers the size of the potential market for ivermectin and encourage its production.

Efficacy and safety of ascending doses of moxidectin against Strongyloides stercoralis infections in adults: a randomised, parallel-group, single-blinded, placebo-controlled, dose-ranging, phase 2a trial

BACKGROUND

Strongyloidiasis represents a major public health issue, particularly in resource-limited countries. Preliminary studies suggest that moxidectin might serve as an alternative to the only available treatment option, ivermectin. We aimed to evaluate the efficacy and safety of ascending doses of moxidectin in Strongyloides stercoralis-infected patients.

METHODS

We did a randomised, parallel-group, single-blinded, placebo-controlled, dose-ranging, phase 2a trial in four villages in northern Laos. Eligible adults (aged 18-65 years) with S stercoralis infection intensities of at least 0·4 larvae per g of stool in at least two stool samples were randomly assigned (1:1:1:1:1:1:1) by use of computerised, stratified, block randomisation into seven treatment groups: 2 mg of moxidectin, 4 mg of moxidectin, 6 mg of moxidectin, 8 mg of moxidectin, 10 mg of moxidectin, 12 mg of moxidectin, or placebo. Participants and primary outcome assessors were masked to treatment allocation, but study site investigators were not. Participants received a single oral dose of their allocated dose of moxidectin in 2 mg tablets, or four placebo tablets. Three stool samples were collected at baseline and two stool samples were collected 28 days after treatment from each participant. A Baermann assay was used to quantify S stercoralis infection and Kato-Katz thick smears were used to qualitatively identify coinfections with additional helminths species. The primary endpoint was cure rate against S stercoralis and was analysed in an available case analysis set, defined as all randomly assigned participants with primary endpoint data. Predicted cure rates and associated CIs were estimated with hyperbolic E_max models. Safety was evaluated in the intention-to-treat population. This trial is registered at ClinicalTrials.gov, NCT04056325, and is complete.

FINDINGS

Between Nov 27, 2019, and March 15, 2020, 785 adults were screened for trial eligibility. Of these, 223 participants were randomly assigned to treatment groups and 209 completed the study and were analysed for the primary outcome. 2 mg of moxidectin had a predicted cure rate of 75% (95% CI 59-87; 22 [73%] of 30 cured) against S stercoralis compared with a predicted cure rate of 14% (5-31; four [14%] of 29 cured) for placebo. With escalating doses, the probability of cure increased from 83% (95% CI 76-88; 26 [90%] of 29 cured) at 4 mg to 86% (79-90; 27 [84%] of 32 cured) at 6 mg, and to 87% (80-92; 24 [83%] of 29 cured) at 8 mg, levelling off at 88% (80-93; 29 [97%] of 30 cured) at 10 mg and 88% (80-93; 26 [87%] of 30 cured) at 12 mg. Moxidectin was well tolerated across all treatment groups, with no serious adverse events being recorded and all reported symptoms being classified as mild.

INTERPRETATION

4-12 mg of moxidectin showed promising tolerability and efficacy profiles in the treatment of S stercoralis infections in adults. Because 8 mg of moxidectin is used for the treatment of onchocerciasis and has been evaluated for other helminth infections, we recommend this dose for phase 2b and phase 3 trials of strongyloidiasis therapy.

FUNDING

Fondazione Adiuvare.

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

BACKGROUND

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

METHODS/RESULTS

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

CONCLUSION

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

Ivermectin concentration in breastmilk of a woman with Strongyloides stercoralis and human T-lymphotropic virus-I co-infection

Ivermectin is a widely used drug for the treatment of various neglected tropical diseases, such as lymphatic filariasis, onchocerciasis, and strongyloidiasis among others. Despite its excellent safety profile, there are few published studies of the use of ivermectin in children, pregnant and nursing women. In the present study, we report clinical data on ivermectin concentrations in breastmilk of a woman with Strongyloides stercoralis and HTLV-I coinfection. Ivermectin levels in breastmilk ranged from 1.4 to 20.8 ng/ml, with a mean of 9.26 ng/ml after a single dose of 200 µg/kg. We estimated the possible ivermectin exposure of the infant to be 1.1 µg/kg, 0.55% of the weight-adjusted percentage of the maternal dose. This value is largely under the threshold established by the World Health Organization for safe breastfeeding. Our results bolster previous findings on the secretion of ivermectin into breastmilk in healthy volunteers. The findings from this case study do not support exclusion of lactating women or interrupting lactation to accommodate it.

Multiple-dose versus single-dose ivermectin for Strongyloides stercoralis infection (Strong Treat 1 to 4): a multicentre, open-label, phase 3, randomised controlled superiority trial

BACKGROUND

Strongyloides stercoralis infection is a neglected condition that places people who are immunocompromised at risk of hyperinfection and death. Ivermectin is the drug of choice for the treatment of S stercoralis infection, but there is no definitive evidence on the optimal dose. This trial aimed to assess whether multiple doses of ivermectin were superior to a single dose for the treatment of non-disseminated strongyloidiasis.

METHODS

Our study was designed as a multicentre, open-label, phase 3, randomised controlled superiority trial. Participants were enrolled in four centres in Italy, three in Spain, and two in the UK, and recruiting sites were predominantly hospitals. Eligible patients were older than 5 years, weighed more than 15 kg, were residents in an area not endemic for S stercoralis, and either were positive for S stercoralis in faecal tests and on serology (any titre) or had a positive serological test with high titres, irrespective of the result of faecal tests. Patients were randomly assigned (1:1) using a computer-generated, blinded allocation sequence (with randomly mixed block sizes of six, eight, and ten participants) to receive either one dose of ivermectin 200 μg/kg or four doses of ivermectin 200 μg/kg (given on days 1, 2, 15, and 16). The primary endpoint was the proportion of participants with clearance of S stercoralis infection at 12 months, which was assessed in all randomly assigned participants who were not lost to follow-up (modified full-analysis set) and in participants in the modified full-analysis set who did not deviate from the assigned treatment regimen (per-protocol set). All participants were included in the safety analysis. The trial was registered with ClinicalTrials.gov, NCT01570504, and is now closed for recruitment.

FINDINGS

Of the 351 patients assessed for eligibility, 309 recruited between March 26, 2013, and May 3, 2017, were randomly assigned to one dose (n=155) or four doses (n=154) of ivermectin. At 12 months in the modified full-analysis set, 86% (95% CI 79 to 91; 102 of 118 participants) had responded to treatment in the single-dose group compared with 85% (77 to 90; 96 of 113 participants) in the four-dose group (risk difference 1·48%, 95% CI -7·55 to 10·52; p=0·75); similar results were observed in the per-protocol set. Adverse events were generally of mild intensity and more frequent in the multiple-dose than in the single-dose group. The trial was terminated early due to futility.

INTERPRETATION

Multiple doses of ivermectin did not show higher efficacy and was tolerated less than a single dose. A single dose should therefore be preferred for the treatment of non-disseminated strongyloidiasis.

FUNDING

There was no funding source for this study.

Imported strongyloidiasis: Data from 1245 cases registered in the +REDIVI Spanish Collaborative Network (2009-2017)

BACKGROUND

Imported strongyloidiasis is increasingly being diagnosed in non-endemic areas. The aim of this study was to describe the epidemiological, clinical and microbiological characteristics of patients with imported strongyloidiasis in Spain.

METHODOLOGY

This is an observational retrospective study that included all patients diagnosed of strongyloidiasis registered in the +REDIVI Collaborative Network from 2009 to 2017. Demographic, epidemiological and clinical information was collected from the +REDIVI database, and extra information regarding microbiological techniques, treatment and follow-up was requested to participant centers.

FINDINGS

Overall, 1245 cases were included. Most of them were immigrants (66.9%), and South America was the most frequent area of origin. Detection of larvae in stool samples was observed in 21.9% of the patients, and serological tests allowed making the diagnosis in the rest of the cases. Eosinophilia was present in 82.2% of cases. Treatment with ivermectin (compared with albendazole) was the most strongly associated factor to achieve the cure (OR 2.34).

CONCLUSIONS

Given the long latency of the infection and the risk of developing a severe presentation, screening of S. stercoralis infection should be mandatory in patients coming from or had traveling to endemic areas, especially in those with immunosuppressant conditions.

Management of severe strongyloidiasis attended at reference centers in Spain

INTRODUCTION

Strongyloides stercoralis is a globally distributed nematode that causes diverse clinical symptoms in humans. Spain, once considered an endemic country, has experienced a recent increase in imported cases. The introduction of serology helps diagnosis and is currently replacing microbiological techniques in some settings, but its sensitivity is variable and can be low in immunocompromised patients. Diagnosis can only be confirmed by identification of larvae. Often, this "gold standard" can only be achieved in severe cases, such as disseminated S.stercoralis infection, or S.stercoralis hyperinfection syndrome, where parasite load is high. In addition, these clinical presentations are not well-defined. Our aim is to describe severe cases of S.stercoralis, their epidemiological profile, and their clinical details.

METHODS

An observational retrospective study of disseminated S.stercoralis infection, or hyperinfection syndrome. Inclusion criteria: aged over 18, with a diagnosis of disseminated S.stercoralis infection, or hyperinfection syndrome, confirmed by visualization of larvae. Patients were identified through revision of clinical records for the period 2000-2015, in collaboration with eight reference centers throughout Spain.

RESULTS

From the period 2000-2015, eighteen cases were identified, 66.7% of which were male, with a median age of 40 (range 21-70). Most of them were foreigners (94.4%), mainly from Latin America (82.3%) or Western Africa (17.6%). Only one autochthonous case was identified, from 2006. Immunosuppressive conditions were present in fourteen (77%) patients, mainly due steroids use and to retroviral coinfections (four HIV, two HTLV). Transplant preceded the clinical presentation in four of them. Other comorbidities were coinfection with HBV, Trypanosoma cruzi, Mycobacterium leprae or Aspergillus spp. All presented with digestive disorders, with 55.6% also presenting malaise. 44.4% of cases had fever, 27.8% skin complaints, and 16.7% respiratory or neurological disorders. One patient presented anemia, and one other nephrotic syndrome. Diagnosis was confirmed by identification of larvae in fresh stool samples (n = 16; 88.9%), concentration techniques (n = 6; 33.3%), larval culture (n = 5; 29.4%), or digestive biopsies (n = 8; 44%). S.stercoralis forms were identified during necropsy in one case. In addition, ten (55%) had a positive serology. All the cases were treated with ivermectin, six (33%) also received albendazole and one case received thiabendazole followed by ivermectin. All needed inpatient management, involving a mean hospitalization stay of 25 days (range 1-164). Two cases received intensive care and eventually died.

CONCLUSIONS

Only eighteen cases of disseminated S.stercoralis infection/hyperinfection syndrome were identified from the 15-year period, most of which were considered to have been imported cases. Among those, immunosuppression was frequent, and mortality due to S.stercoralis was lower than previously described.

Ivermectin Treatment and Sanitation Effectively Reduce Strongyloides stercoralis Infection Risk in Rural Communities in Cambodia

BACKGROUND

Strongyloides stercoralis is the only soil-transmitted helminth with the ability to replicate within its host, leading to long-lasting and potentially fatal infections. It is ubiquitous and its worldwide prevalence has recently been estimated to be at least half that of hookworm. Information on the epidemiology of S. stercoralis remains scarce and modalities for its large-scale control are yet to be determined.

METHODOLOGY/PRINCIPAL FINDINGS

A community-based two-year cohort study was conducted among the general population in a rural province in North Cambodia. At each survey, participants infected with S. stercoralis were treated with a single oral dose of ivermectin (200μg/kg BW). Diagnosis was performed using a combination of the Baermann method and Koga agar plate culture on two stool samples. The cohort included participants from eight villages who were either positive or negative for S. stercoralis at baseline. Mixed logistic regression models were employed to assess risk factors for S. stercoralis infection at baseline and re-infection at follow-up. A total of 3,096 participants were examined at baseline, revealing a S. stercoralis prevalence of 33.1%. Of these participants, 1,269 were followed-up over two years. Re-infection and infection rates among positive and negative participants at baseline were 14.4% and 9.6% at the first and 11.0% and 11.5% at the second follow-up, respectively. At follow-up, all age groups were at similar risk of acquiring an infection, while infection risk significantly decreased with increasing village sanitation coverage.

CONCLUSIONS/SIGNIFICANCE

Chemotherapy-based control of S. stercoralis is feasible and highly beneficial, particularly in combination with improved sanitation. The impact of community-based ivermectin treatment on S. stercoralis was high, with over 85% of villagers remaining negative one year after treatment. The integration of S. stercoralis into existing STH control programs should be considered without further delay.

Comparison of albendazole regimen for prophylaxis of strongyloides hyperinfection in nephrotic syndrome patients on long-term steroids in Cambodia

Nephrotic syndrome patients on long-term steroids face the risk of having heavy uncomplicated strongyloidiasis or death from its extreme form, the strongyloides hyperinfection. The risk can be minimized if we eradicate the parasite first. We compare a once daily and twice daily albendazole regimen in preventing this potentially fatal complication in 122 patients with nephrotic syndrome.

Subcutaneous ivermectin use in the treatment of severe Strongyloides stercoralis infection: two case reports and a discussion of the literature

BACKGROUND

Strongyloides stercoralis infection presents with varying degrees of severity, but it often primarily involves the small bowel. In severe infection and cases of hyperinfection, ileus and small-bowel obstruction may prevent enteral absorption of anthelminthics such as ivermectin. At present there are no parenteral anthelminthics licensed for use in humans.

METHODS

Here, we describe two cases of severe S. stercoralis infection treated with an unlicensed veterinary preparation of subcutaneous ivermectin, and we discuss the published reports of the use of this treatment elsewhere.

RESULTS

Both patients were successfully treated with subcutaneous ivermectin, and both recovered completely.

CONCLUSIONS

Despite the limited published experience of parenteral ivermectin use, there is evidence that it may be a safe and effective treatment for severe strongyloidiasis. However, more data are needed to guide dosing schedules and monitoring for toxicity.

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.

Acute respiratory distress syndrome due to Strongyloides stercoralis infection in a patient with cervical cancer

A 62-year-old woman complained of diarrhea and vomiting after receiving chemotherapy for cervical cancer in association with high doses of corticosteroids. Two months later, the patient developed acute respiratory distress syndrome, and numerous Strongyloides stercoralis parasites were found in the intrabronchial discharge. Ivermectin was administered daily until nematodes were no longer detected in the sputum, and the patient's condition was successfully rescued. Antibodies for human T-cell lymphotropic virus-1 (HTLV-1) were positive. HTLV-1 infection and the administration of corticosteroids are known risk factors for strongyloides hyperinfection syndrome. Therefore, physicians should consider this disease in the differential diagnosis of patients from endemic areas who present with gastrointestinal symptoms under these risk factors.

Recurrence of strongyloides stercoralis infection in a patient with Hansen's disease: a case report

In patients with immunosuppressive disorders, S. stercoralis infection may develop into a hyperinfection syndrome which, on rare occasions, may be a life-threatening condition. Therapy of S. stercoralis infection with thiabendazole has been limited, due to its numerous side effects, and has been replaced by albendazole and ivermectin. The present case report describes a case of Strongyloides Hyperinfection Syndrome (SHS) in a patient with Hansen's disease and lack of response to first-line anthelmintic treatment. A 38 year-old man was diagnosed as having borderline lepromatous leprosy. He developed Erythema Nodosum Leprosum and was treated with thalidomide and prednisone. In May 2010 he was diagnosed with S. stercoralis infection and was treated with albendazole. One year later, the stool examination showed continued presence of S. stercoralis larvae. He was treated with ivermectin (6 mg) in a double dose (given 1 month apart) which resulted in larvae excretion clearance. The absence of infection was confirmed three times during a 1 year followup period by stool examination and non-detection of anti-S. stercoralis IgG levels.

Strongyloides stercoralis: a case study

This article illustrates a case of S stercoralis. This organism causes the disease strongyloidasis. Strongyloidasis is defined by acute manifestation, autoreinfection, or hyperinfection. It is contracted by skin penetration of the filariform larvae in the soil. Diagnosis and effective treatment is dependent on identification through special techniques with stool samples in the clinical laboratory.

[An overview of Strongyloides stercoralis and its infections]

Strongyloidiasis which is an infection caused by Strongyloides stercoralis, has a cosmopolitan distribution in tropical and subtropical regions; whereas, it is sporadic in Turkey. It is estimated that 30-100 million people are infected with this agent worldwide. The infection is usually asymptomatic, however, eosinophilia may be the only sign. S. stercoralis have the ability to persist and replicate within the host for decades and it may lead to infections with high mortality especially in immunocompromised host. Humans are generally infected transcutaneously with filariform larvae. Infections with S. stercoralis usually lead to cutaneous, gastrointestinal, or pulmonary symptoms. Definitive diagnosis of strongyloidiasis is made on the basis of detection of larvae in the stool, sputum or duodenal fluid. Hovewer, strongyloidiasis is difficult to diagnose since the parasite load is low and the larval output is irregular in majority of the patients. This situation necessitates the collection of consecutive samples and the use of concentration techniques. The burden of Strongyloides may be overlooked in especially non-endemic regions. Strongyloidiasis should be considered before the application of immunosuppressive therapy in patients with unexplained eosinophilia, serpiginous skin lesions, or pulmonary or gastrointestinal symptoms. The goal of treatment is to eliminate the parasites and ivermectin is the drug of choice. Besides, albendazole or thiabendazole may used as alternative agents in the treatment. Improved human waste disposal services are considered to be the main requirement to reduce the high prevalence of this disease. In this review, it was aimed to withdraw attention to strongyloidiasis and to overview its prevalence, clinical manifestations, diagnosis, management and prevention strategies.

Tribendimidine and albendazole for treating soil-transmitted helminths, Strongyloides stercoralis and Taenia spp.: open-label randomized trial

Background

Tribendimidine is an anthelminthic drug with a broad spectrum of activity. In 2004 the drug was approved by Chinese authorities for human use. The efficacy of tribendimidine against soil-transmitted helminths (Ascaris lumbricoides, hookworm, and Trichuris trichiura) has been established, and new laboratory investigations point to activity against cestodes and Strongyloides ratti.

Methodology/Principal Findings

In an open-label randomized trial, the safety and efficacy of a single oral dose of albendazole or tribendimidine (both drugs administered at 200 mg for 5- to 14-year-old children, and 400 mg for individuals ≥15 years) against soil-transmitted helminths, Strongyloides stercoralis, and Taenia spp. were assessed in a village in Yunnan province, People's Republic of China. The analysis was on a per-protocol basis and the trial is registered with controlled-trials.com (number ISRCTN01779485). Both albendazole and tribendimidine were highly efficacious against A. lumbricoides and, moderately, against hookworm. The efficacy against T. trichiura was low. Among 57 individuals who received tribendimidine, the prevalence of S. stercoralis was reduced from 19.3% to 8.8% (observed cure rate 54.5%, p = 0.107), and that of Taenia spp. from 26.3% to 8.8% (observed cure rate 66.7%, p = 0.014). Similar prevalence reductions were noted among the 66 albendazole recipients. Taking into account “new” infections discovered at treatment evaluation, which were most likely missed pre-treatment due to the lack of sensitivity of available diagnostic approaches, the difference between the drug-specific net Taenia spp. cure rates was highly significant in favor of tribendimidine (p = 0.001). No significant adverse events of either drug were observed.

Conclusions/Significance

Our results suggest that single-dose oral tribendimidine can be employed in settings with extensive intestinal polyparasitism, and its efficacy against A. lumbricoides and hookworm was confirmed. The promising results obtained with tribendimidine against S. stercoralis and Taenia spp. warrant further investigations. In a next step, multiple-dose schedules should be evaluated.

More than a billion people are infected with intestinal worms and, in the developing world, many individuals harbor several kinds of worms concurrently. There are only a handful of drugs available for treatment, and drug efficacy varies according to the worm species. We compared the efficacy of a single oral dose of tribendimidine, a new broad-spectrum worm drug from China, with the standard drug albendazole for the treatment of hookworm, large roundworm (Ascaris lumbricoides), whipworm (Trichuris trichiura) and, for the first time, Strongyloides stercoralis and tapeworm (Taenia spp.). Our single-blind randomized trial was conducted in a village in Yunnan province, southwest China. Both drugs showed high efficacy against A. lumbricoides and a moderate efficacy against hookworm. Among 57 tribendimidine recipients, the prevalence of S. stercoralis was reduced from 19.3% to 8.8%, and that of Taenia spp. from 26.3% to 8.8%. Similar prevalence reductions were noted among the 66 albendazole recipients. Taking into account additional infections only discovered at treatment evaluation, the difference between the drug-specific Taenia spp. net cure rates was highly significant in favor of tribendimidine. In view of our promising results, multiple-dose schedules with tribendimidine against S. stercoralis and Taenia spp. should be evaluated next.

Optimum methods of inactivation of Strongyloides stercoralis larvae from reclaimed wastewater

Strongyloidiasis presents a major health hazard when reusing wastewater. Albendazol with a concentration of 4 mg/l, a contact time of 45 min, pH 1.2 and pH 10.2, killed the larva. The larva was also killed with a 0.03% concentration of iodine and a detention time of 30 min or a 0.04% concentration of iodine and a contact time of 10 min. The required detention time to inactivate larva in water was found to be 17 days. The minimum revealed residual chlorine to kill the larvae was 4 mg/l with 120 min of detention time, and a minimum contact time was found to be 80 min with a residual of 23 mg/l. Many methods are available to inactivate the Strongyloides stercoralis, which could be acids, alkaline chemicals, larvicidal chemicals, super chlorination, or just detention time. The best method must be determined according to the prevailing specific environmental site and the feasibility of the selected method(s).

New trends in diagnosis and treatment of chronic intestinal strongyloidiasis stercoralis in Egyptian patients

Strongyloidiasis, caused by Strongyloides stercoralis, is diagnosis considered as a challenge to clinician and laboratory technician. Because the auto-infective larvae are difficult to eradicate, one regimen dose may be in-sufficient and re-treatment of patients on two occasions, at 1 and 2 months after the initial treatment dose was recommended. This re-treatment regimen has yet to be proven in clinical trials. This study was performed on 24 patients who completed the study and having Strongyloides larvae in their stool obtained from Mansoura University Hospitals. Each stool sample was examined by direct saline smear, the formalin-ether sedimentation technique and agar plate culture. Patients were treated with Mirazid double course for a month to be followed up by stool examination by traditional method and agar plate culture for three consecutive months. In this study five cases out of 24 were asymptomatic (20.8%). Symptoms include abdominal manifestations as nausea and vomiting (16.7%), epi-gastric pain and nausea (12.5%), generalized abdominal pain (12.5%), chronic diarrhea (16.7%), irregular bowel habit (8.3%), and urticaria with abdominal pain (4.2%). Agar plate culture gave 100% positivity, even in cases were negative by coprological methods either direct smear and/or sedimenttation technique. All cases were cured by Mirazid given for one month except three resistant cases. Only one case responded to repeated course of Mirazid, while the other two cases still had larvae in their stool by agar culture plate. On combined therapy of both Mirazid and Mebendazole, larvae could be eliminated from their stool as approved by agar plate culture.

Strongyloides stercoralis: risks posed to immigrant patients in an Australian tertiary referral centre

BACKGROUND

Strongyloides stercoralis is a nematode human parasite with a global prevalence that is able to maintain a prolonged infestation by means of its autoinfective life cycle. Immunosuppression may result in a life-threatening hyperinfection syndrome. Recent changes in migration have resulted in the arrival of many immigrants from endemic areas. As to whether physicians are alert to the risks of strongyloidiasis in these patient groups is unclear. The aim of the study was to assess the risks posed by chronic strongyloidiasis in patients presenting to a tertiary referral centre and the need for screening of immigrant patients before immunosuppression.

METHODS

The study comprised a retrospective review of cases of strongyloidiasis presenting to the Alfred Hospital, Melbourne. Thirty-three cases were diagnosed by either positive serology or faecal microscopy between January 1998 and January 2005. The medical records for 29 cases were examined with regard to demographics, clinical features and complications.

RESULTS

Two major groups were identified: immigrants (17) and returned travellers (11). Six immigrants, but no returned traveller, developed a hyperinfective syndrome. Five immigrants received immunosuppressive therapies before developing symptoms of hyperinfection and this was complicated by life-threatening sepsis in two patients. Diagnosis was frequently delayed in the immigrant group who were significantly more likely to present with respiratory symptoms. Four immigrants and two returned travellers were treated with corticosteroids for symptoms that were probably related to larval migration.

CONCLUSION

Before giving immunosuppressive therapies, patients with a history of potential exposure must be investigated for strongyloidiasis and consideration given to empirical treatment.

A modified filter paper culture technique for screening of Strongyloides stercoralis ivermectin sensitivity in clinical specimens

An in vitro test for the detection of ivermectin sensitivity of Strongyloides stercoralis in human clinical specimens was developed. The test has a simple procedure that combines parasite culture with a drug assay. It is based on the principle of the drug effect on larval development test, combined with a modified coproculture using the filter paper culture technique. This does not require parasite isolation, and drug sensitivity can be shown in relationship to the dose. This test can be applied in field surveys for anthelmintic sensitivity and for appropriate drug rotation strategies when drug resistance occurs.

Efficacy and safety of ivermectin and thiabendazole in the treatment of strongyloidiasis

Treatment of strongyloidiasis has been traditionally based on thiabendazole, despite its frequent gastrointestinal side effects and failure to achieve eradication of the parasite from faeces in approximately 30% of cases. Ivermectin has been shown to be more effective for treating chronic uncomplicated strongyloidiasis. The efficacy and tolerability of these drugs in a series of patients treated from 1999 to 2002 at the Oliva Health Centre, Valencia, Spain, are reported. A total of 88 patients diagnosed of strongyloidiasis were treated using the following regimens: thiabendazole 25 mg/kg/12 h for 3 consecutive days in 31 patients; ivermectin 200 mug/kg as a single dose in 22 patients; and ivermectin 200 mug/kg for 2 consecutive days in 35 patients. The efficacy and side effects were recorded. A total of 65 patients were male, and 23 female. The mean age was 64 +/- 12 years. Of the patients, 44 had worked barefoot in rice fields. Among the 31 patients treated with thiabendazole, 25 (78%) met the criteria for cure (the absence of parasite in faeces after examination of three samples collected on alternate days), and 5 (16%) experienced side effects (asthenia, epigastralgia and disorientation). Of the 22 patients treated with ivermectin on a single day, 17 (77%) met the criteria for cure, and 2 (9%) reported side effects (dizziness, dyspepsia). Among the 35 patients treated with ivermectin on 2 consecutive days, 100% met the criteria for cure, and 0% experienced side effects. In chronic uncomplicated strongyloidiasis, a treatment regimen consisting of ivermectin 200 mug/kg for 2 consecutive days provided the best results with regard to efficacy and tolerability. When the eosinophilia continued after treatment, we observed a high percentage of not-cure rate (7 of 9 patients, 77%).

[Strongyloides stercoralis in a patient complaining of chronic diarrhea]

In this study, a case of Strongyloides stercoralis infection in a 38-year-old patient with complaints of chronic diarrhea and stomach ache is presented. His history showed that the patient who has been a mechanic for 25 years is a farmer as well. S. stercoralis larvae were found during the parasitological examination of the patient's stool samples taken 3 times. The patient was given Albendazol (400 mg a day) for fifteen days. After the patient started to take Albendazol, there was a reduction in the number of parasites in the stool examined on the fifth day. In the stool examinations made on the tenth day, fifteenth day and after the treatment ended, no parasites were seen. When the treatment was completed, all the complaints of the patient disappeared. It was found that no investigation of parasitic infection had been made previously and he had been given different treatments. For this reason, it is important to investigate the possibility of parasitic infection in patients with chronic diarrhea.

The beta-tubulin genes of two Strongyloides species

The World Health Organization is sponsoring major treatment programs with the aim of controlling helminth infection throughout the tropical world. Prominent among the anthelmintics recommended for use in these programs are drugs in the benzimidazole (BZ) class. Resistance to these drugs has been associated with polymorphisms in the beta-tubulin gene. We have cloned and sequenced the beta-tubulin genes of Strongyloides stercoralis and Strongyloides ratti and have proceeded to develop a protocol for genotyping single worms for polymorphisms in beta-tubulin. Our findings indicate that S. ratti has a single beta-tubulin gene, making DNA sequence analysis of a single larva PCR product a feasible means of studying BZ resistance in these species. Our genotyping test allows the identification of polymorphisms at codons 167, 198, and 200 in the Strongyloides beta-tubulin gene, thus enabling survey for BZ resistant genotypes.

In vitro antiparasitic activity of extracts of Cardiospermum halicacabum against third-stage larvae of Strongyloides stercoralis

Extracts of Cardiospermum halicacabum, medicinal plant, were tested in vitro for their effectiveness against third-stage larvae of Strongyloidesstercoralis. Third-stage larvae of S. stercoralis were isolated from cultures of dog's feces using agar plate culture method. The larvae (1,000 larvae/ml), suspended in phosphate buffer saline solution, pH 7.4, were exposed to aqueous and alcohol extracts (2,000 microg/ml) of C. halicacabum at 37 degrees C with 5% CO2. Ivermectin (250 microg/ml) and piperazine (2,000 microg/ml) were also used as the reference drugs. The survival of Strongyloides larvae based on its motility was determined daily for 7 days. Strongyloides larvae were viable after contact with ivermectin, piperazine and C. halicacabum (aqueous and alcohol) solutions, but most of them were immobilized, after exposure to aqueous and alcohol extracts of C. halicacabum within 72 and 48 h, respectively, while ivermectin took from 72 to 144 h, and piperazine more than 7 days, to achieve the same rate of nonmotility. Clearly, the viability of S. stercoralis larvae was significantly reduced when exposed to extracts of C. halicacabum. Further study is needed on the antiparasitic activity of aqueous and alcohol extracts of C. halicacabum against S. stercoralis.

Treatment of Human Disseminated Strongyloidiasis with a Parenteral Veterinary Formulation of Ivermectin

There are no parenteral antihelminthic drugs licensed for use in humans. We report the successful treatment of disseminated strongyloidiasis with a parenteral veterinary formulation of ivermectin in a patient presenting with severe malabsorption and paralytic ileus. To our knowledge, ivermectin levels are reported for the first time in this situation.

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.

Association of a sex-related difference of Strongyloides stercoralis-specific IgG4 antibody titer with the efficacy of treatment of strongyloidiasis

It is difficult to completely eradicate strongyloidiasis, a human intestinal nematode infection with Strongyloides stercoralis with drugs, especially in males. To find host factors involved in the response to treatment, patients infected with S. stercoralis were examined for S. stercoralis-specific antibody titers and the effect of treatment with albendazole on these titers were determined. The cure rate was slightly but not significantly lower in males than in females (P = 0.108). However, a significantly higher titer of S. stercoralis-specific IgG4 antibody was observed in males than in females (P = 0.0097), and the S. stercoralis-specific IgG4 antibody titer was significantly higher in the male non-cured group than in the cured group (P = 0.035). These results suggest that elevation of the S. stercoralis-specific IgG4 antibody titer is associated with resistance to treatment of S. stercoralis infection, especially in males.

Chemotactic behaviour of Strongyloides stercoralis infective larvae on a sodium chloride gradient

Chemotactic responses of Strongyloides stercoralis infective larvae (L3) to sodium chloride (NaCl) were investigated by recording larval tracks on a saline gradient in agarose. On agarose, larvae migrated randomly, whereas when placed at 0.01 m NaCl larvae moved to approximately 1.1 m NaCl where they turned, headed down the gradient and eventually remained circling at a favoured salinity (0.03-0.07 m). Conversely, when placed at 2.85 m NaCl, the L3 larvae moved unidirectionally to lower, more favoured salt concentrations. Here they circled, changing directions frequently while making 'loop-like' tracks. Larvae were immobilized within 5 min at salt concentrations exceeding 3 m NaCl. When placed at 0.01 m NaCl, 51.1% +/- 26.9 migrated to 1.1 m NaCl after 2 min, and 80% +/- 18.7 did so after 8 min, at an average velocity of 4.1 +/- 1.4 mm/min. Larvae (53.6% +/- 21.6) were repelled from 2.85 m NaCl to lower concentrations after 2 min. After 8 min, 95% +/- 11.1 were repelled, moving at an average velocity of 6.2 +/- 1.1 mm/min. Using this bioassay, the influence of neuronal control over chemotactic behaviour of S. stercoralis and other parasitic nematodes can be elucidated.

Response to carbon dioxide by the infective larvae of three species of parasitic nematodes

The response of infective third-stage larvae (L3) of three species of parasitic nematodes, Ancylostoma caninum, Strongyloides stercoralis, and Haemonchus contortus to carbon dioxide (CO(2)) at physiological concentrations was investigated. L3 of the skin-penetrating species, A. caninum and S. stercoralis, were stimulated by CO(2) at the concentration found in human breath (3.3-4%); these larvae responded by crawling actively, but not directionally. Crawling was not stimulated by breath passed through a CO(2)-removing "scrubber" or by "bench air". Both A. caninum and S. stercoralis L3 stopped crawling when exposed to 5% CO(2) for 1 min. L3 of A. caninum became active 9-14 min after exposure to 5% CO(2) ended, but activity resumed more rapidly (10-15 s) if larvae were subsequently exposed to breath or breath through the scrubber. L3 of S. stercoralis resumed crawling 30-35 s after exposure to 5% CO(2), but resumed crawling within a very few seconds when exposed to breath or breath through the scrubber. Thus, while 5% CO(2) was inhibitory, lower concentrations of this gas stimulated L3 of both species. Apparently, exposing immobilized larvae to breath or breath through the scrubber causes the environmental CO(2) concentration to drop to a level that is stimulatory. The L3 of H. contortus ceased crawling and coiled when exposed to human breath or to 1% CO(2), but continued to move within the coil in both cases. The crawling response of the L3 of the two skin-penetrating species, A. caninum and S. stercoralis, to stimulation by CO(2) probably relates to their active host-finding behavior, while the cessation response elicited by CO(2) in H. contortus larvae may relate to the fact that they rely on passive ingestion by a ruminant host.

Assay of nematocidal activity of isoquinoline alkaloids using third-stage larvae of Strongyloides ratti and S. venezuelensis

We examined the effects of isoquinoline alkaloids in vitro in an effort to identify a treatment for Strongyloides stercoralis larva migrans in humans. Infective third-stage larvae of S. ratti and S. venezuelensis were used as model nematodes for S. stercoralis. Nematocidal activity was evaluated by the 50% paralysis concentration (PC(50)). Most of the tested isoquinoline alkaloids had activity for S. ratti and S. venezuelensis. We then evaluated in vitro cytotoxicity, which was the 50% inhibition concentration (IC(50)) of the compounds using HL60 tissue-culture cells. Three of the compounds (protopine, D-corydaline, and L-stylopine) which exhibited strong nematocidal activity, showed little cytotoxicity. In addition, we examined the relationship between nematocidal activity and cytotoxicity using the PC(50)/IC(50) ratio. A ratio equivalent to or lower than that calculated for the currently prescribed strongyloidosis treatments, ivermectin, albendazole and thiabendazole, was observed for allocryptopine, protopine, dehydrocorydaline, D-corydaline, L-stylopine, and papaverine. In contrast, the PC(50)/IC(50) ratios for protopine, D-corydaline, and L-stylopine were substantially more favorable. Therefore, protopine, D-corydaline, and L-stylopine were identified as potential effective treatments for strongyloidosis.

[Strongyloidosis. Part IX. Treatment]

The treatment of chronic and massive (uncomplicated) and severe (complicated) disseminated strongyloidosis, was presented from the historical point of view. The sequence of achievements in regard of treatment of the gentian violet, dithiazine iodide, benzimidazoles (thiabendazole, mebendazole, albendazole, cambendazole), ivermectin and cyclosporin A, was described. The recommendations for treatment of strongyloidosis are also given.

Effect of chronic ethanol consumption on protective T-helper 1 and T-helper 2 immune responses against the parasites Leishmania major and Strongyloides stercoralis in mice

BACKGROUND

Chronic alcohol consumption has been associated with significant increases in the prevalence of infectious diseases, and it has been suggested that these increases are caused by a direct effect of ethanol on the immune response. The objective of this study was to determine whether chronic ethanol consumption would affect the development of protective immunity to Leishmania major, which is controlled by the T-helper 1 (Th1) subset of CD4 cells, and Strongyloides stercoralis, which is controlled by the Th2 subset.

METHODS

Mice were fed ethanol-containing liquid diet (25% ethanol-derived calories), liquid isocaloric diet without ethanol, or solid chow and then exposed to either of the two parasites. The ability of the mice chronically consuming alcohol to eliminate the infections was determined, as were the levels of parasite-specific humoral and cellular immune responses.

RESULTS

Mice chronically consuming alcohol were capable of eliminating both of these infections in a manner identical to the control mice. In addition, splenocytes from mice chronically consuming alcohol infected with L. major produced nitric oxide at the same levels as in control mice. Antibody responses were altered in a manner suggesting an increase in Th2 immunity and a decrease in Th1 immunity in the mice chronically consuming alcohol. In mice chronically consuming alcohol that were infected with S. stercoralis, eosinophils migrated to the parasite's microenvironment, and antibodies were produced at levels equivalent to those seen in control mice.

CONCLUSIONS

Mice maintained on an ethanol-containing liquid diet had some alteration in their ability to produce Th1 and Th2 immune responses yet were capable of generating unimpaired protective Th1 and Th2 responses.

[A rare cause of asthma exacerbation: systemic anguilluliasis]

Strongyloides is an helminthic infection that may induce bronchospasm during systemic migration of larvae. We report a case of a 60 years old man originating from Caribbean who had corti-codependent asthma since 30 years. He was hospitalized for severe exacerbation that worsen when steroid dosage was increase. Sputum examination revealed the presence in great number of Larvae of Strongyloides stercoralis. A good clinical evolution was achieved after specific anti-helminthic treatment. Later on, it was even possible to stop completely steroid treatment. This clinical case demonstrates the interest to look for Strongyloides superinfection in asthmatic patients that worsen when receiving increasing dose of steroids. This is particularly important for patients who have resided, even many years earlier, in areas where intestinal helminthic infection are endemic.

Production of a high level of specific IgG4 antibody associated with resistance to albendazole treatment in HLA-DRB1*0901-positive patients with strongyloidiasis

Strongyloidiasis, a human intestinal infection with Strongyloides stercoralis, is difficult to treat with drugs. The factors influencing this phenomenon remain unclear. To determine the host factors involved in response to treatment, 46 patients with strongyloidiasis were treated with albendazole, followed-up for 1 year, and separated into two groups: cured and non-cured. Serum levels of specific IgA, IgE, IgG, IgG1, and IgG4 antibodies were estimated using S. stercoralis antigen. Significantly higher titers of IgG4 antibody were observed in the non-cured group than in the cured group (P = 0.016). A total of 88 patients were typed for HLA-DRB1 alleles and analyzed for serum levels of antibody. The S. stercoralis-specific IgG4 antibody titers were significantly higher in the HLA-DRB1*0901-positive group than in the negative group (corrected P = 0.044). These results suggest that HLA-DRB1*0901 is a possible genetic marker for resistance to treatment of S. stercoralis that is associated with elevation of S. stercoralis-specific IgG4 antibody titer.

First-glance diagnosis of Strongyloides stercoralis autoinfection by stool microscopy

We report a case of autoinfection due to Strongyloides stercoralis in a 27-year-old Ethiopian AIDS patient living in Germany for nearly 3 years. This case was diagnosed on the basis of a single-view field in microscopy of a freshly obtained formalin-fixed stool specimen showing both rhabditiform and filariform larvae. The diagnosis of autoinfection by microscopy is discussed in detail.

Disseminated strongyloidiasis arising from a single dose of dexamethasone before stereotactic radiosurgery

A fatal case of disseminated strongyloidiasis is described, abruptly following a single high dose of dexamethasone before stereotactic radiosurgery. The mechanism of steroid-induced dysregulation of Strongyloides infection is unclear. Treatment failure and the use of rectal thiabendazole in the presence of bowel obstruction is discussed. This case reinforces the need to screen selected patients for strongyloidiasis before any high-dose steroid therapy, particularly in the presence of persistent eosinophilia.

Efficacy of ivermectin against Strongyloides stercoralis infection in jirds (Meriones unguiculatus)

The activity and distribution of ivermectin (IVM), a broad spectrum anthelmintic for various nematodes and arthropods, was tested against Strongyloides stercoralis infection in the jird (Meriones unguiculatus.) The pattern of IVM concentration in the serum of jirds after either low- (200 microg/kg) or high-dose (1000 microg/kg) treatment by intraperitoneal injection showed a typical single-peak profile with the maximum drug levels detected at 1 h followed by a rapid decline to undetectable values by 48 h posttreatment. With equivalent IVM doses, the serum levels in male jirds were significantly higher than those observed in female jirds at 1 and 12 h posttreatment (P < 0.05). Low-dose IVM treatment of either male or female jirds, in comparison with that of the respective control groups, produced no observable effect on the adult worm burden or the parasite fecundity. The curative dose for S. stercoralis in both sexes of animals was achieved when using the high dose of 1000 microg/kg of IVM. The area under the curve calculated from the serum-concentration profiles in males was significantly higher than that for females after the high-dose treatment of IVM (P < 0.05). By low-dose treatment, a significantly lower adult worm burden was observed in males compared with that in females (P < 0.05), and this difference correlated with the higher serum levels of IVM in male animals. The distribution of IVM in the jird after high-dose treatment was characterized by initial appearances at 1 h of maximum levels of the drug in the serum and intestinal content. The maximum level in the feces was reached at 12 h posttreatment and rapidly declined thereafter. The level in the intestinal tissue was comparatively much lower than that in the intestinal content and the feces. The half-life of IVM in the intestinal content (49.5 h) was longer than those in the serum, feces, and intestinal tissue (6.53-13.07 h). Analyses of the relationship between the peak serum IVM occurring at 1 h posttreatment and the adult worm recovery revealed that the minimal serum concentration associated with clearance of the adult worm from the jird was approximately 0.65 microg/ml. The jird-S. stercoralis model has not only made studies on various aspects of parasite biology possible, but also provided an in vivo system to examine the efficacy as well as the mode of action of IVM against this intestinal nematode.

Strongyloides hyperinfection in a renal transplant recipient receiving cyclosporine: possible Strongyloides stercoralis transmission by kidney transplant

Strongyloides hyperinfection and dissemination are recognized complications in kidney allograft recipients; however, the development of strongyloidiasis in renal transplant recipients receiving cyclosporine A (CyA) has not been described, nor has the development of strongyloidiasis in other organ transplant recipients. The former observation has been attributed to the antiparasitic activity of CyA seen in animal studies; the latter has no explanation yet. We report the first case of Strongyloides hyperinfection in a renal transplant patient occurring immediately after CyA was discontinued. From the unique characteristics of this case, it appears that the anti-Strongyloides activity of CyA in animals may also be found in humans.

Short report: long-term serum antibody isotype responses to Strongyloides stercoralis filariform antigens in eight patients treated with ivermectin

The enzyme-linked immunosorbant assay was used to investigate long-term changes in serum immunoglobulin G1 (IgG1), IgG4, IgE, and IgA against Strongyloides stercoralis phosphate-buffered saline-soluble filariform larval antigens in eight Jamaican patients treated with ivermectin. Patients were followed for periods of between 170 and 542 days. Based on repeated formalin-ether concentration and agar plate culture, all patients were found to be uninfected up to 18 months following chemotherapy. Generally, all antibody isotype levels decreased following treatment, although there was considerable heterogeneity among patients. In a single patient with hyperinfection, the decrease in IgG4 was marginal and may represent a treatment failure. Reduction in serum antibody isotype responses to S. stercoralis following treatment may be used to assess the effectiveness of ivermectin in treating endemic strongyloidiasis.

A comparative trial of a single-dose ivermectin versus three days of albendazole for treatment of Strongyloides stercoralis and other soil-transmitted helminth infections in children

A randomized trial carried out in rural Zanzibar comparing a single dose of 200 micrograms/kg of ivermectin and 400 mg/day for three days of albendazole for treatment of strongyloidiasis and other intestinal nematodes is described. In 301 children with Strongyloides stercoralis infection, treatment with ivermectin or albendazole resulted in cure rates of 83% and 45%, respectively. While both drugs were very effective against Ascaris lumbricoides, Trichuris trichiura was cured only in 11% (ivermectin) and 43% (albendazole) of the subjects, although the mean eggload was reduced by 59% and 92%, respectively. Ivermectin was ineffective against hookworms, while albendazole resulted in a cure rate of 98%. No severe side effects were recorded and mild side effects were of transient nature for both treatments. Therefore, ivermectin provides a safe and a highly effective single dose treatment for S. stercoralis and A. lumbricoides, while it is not an alternative for the treatment of T. trichiura and hookworm infections.

Strongyloides stercoralis: histopathology of uncomplicated and hyperinfective strongyloidiasis in the Mongolian gerbil, a rodent model for human strongyloidiasis [corrected]

Tissues from corticosteroid-treated gerbils hyperinfected with Strongyloides stercoralis were compared grossly and microscopically to similar tissues from animals with uncomplicated strongyloidiasis. Gerbils with hyperinfection developed severe pulmonary alveolar haemorrhage with a variable degree of subacute eosinophilic interstitial pneumonia associated with numerous alveolar, vascular and interstitial larvae. Hyperinfection induced by corticosteroids, given either before inoculation of S. stercoralis larvae or after a chronic Strongyloides infection was established, produced similar lesions. In contrast, lungs from gerbils with uncomplicated Strongyloides infection had severe eosinophilic perivasculitis and vasculitis with very little haemorrhage, no pneumonia and no larvae. Sections of adult worms were present in the proximal part of the intestinal tract, lodged in spaces between mucosal epithelial cells. Adult worms were not associated with inflammation and were more common in the corticosteroid-treated gerbils. In corticosteroid-treated gerbils only, there were numerous larvae in the distal intestinal tract, throughout the intestinal wall and adjacent mesentery, within interstitial tissues and in lymphatic vessels. Significant inflammation with associated larvae was only present in the caecum and mesenteric lymph nodes, suggesting that the caecum was the main site for initiation of parenteral migration with subsequent invasion of the lymphatic system and lungs. The lesions in these gerbils were similar to those found in humans. Infection of gerbils with S. stercoralis is the best rodent model of human strongyloidiasis.

[Clinical study on ivermectin against 125 strongyloidiasis patients]

We treated 125 patients with strongyloidiasis (78 males and 47 females) by 2 oral doses of ivermectin (6 mg) at 2-week interval, and obtained the following results: 1. Eradication rate after treatment was 86.4% (108 of 125 patients), responsively. Out of the total 17 patients were resistant (non-responsive) to treatment, 8 patients received a further course of ivermectin and all Strongyloides stercoralis in their feces were eradicated. 2. Side effects were observed in 7.2% of the patients after the first dose treatment and in 3.2% after the second dose. But all symptoms were mild and self-limited. Although liver disfunction developed in 13.6% of the patients, no symptoms occurred and no special treatment was required. 3. Positive rate of anti-HTLV-I antibody in the resistant group was significantly higher (80.0%) than in the eradicated group (29.2%) and in the stool-negative group (0%). 4. Although eosinophils before treatment in the eradicated group was significantly higher than that of controls, there was no significant difference between the resistant group and controls. IgE levels in the resistant group was significantly lower than in the eradicated group. We would like to conclude that IVM is the best drug for treatment of the patient with Strongyloides stercoralis not only from this results but also our previous reports which had investigated the clinical efficacy on thiabendazole, mebendazole and albendazole.