Strongyloides Hyperinfection: A Treatment Dilemma

Human Strongyloides stercoralis infection

Strongyloides stercoralis is an important soil-transmitted helminth occurring world-wide and affecting 30-100 million people. Because many cases are asymptomatic and sensitive diagnostic methods are lacking, S. stercoralis infection is frequently underdiagnosed. The increasing incidence of autoimmune and wasting diseases and increased use of immunosuppressive agents, as well as the increased use of immunosuppressants and cytotoxic drugs, have increased S. stercoralis infection and their mortality. This review provides information about S. stercoralis epidemiology, life cycle, aetiology, pathology, comorbidities, immunology, vaccines, diagnosis, treatment, prevention, control and makes some recommendations for future prevention and control of this important parasite.

Severe strongyloidiasis: a systematic review and meta-analysis of 339 cases

Strongyloidiasis is a parasitosis representing a significant public health problem in tropical countries. It is often asymptomatic in immunocompetent individuals but its mortality rate increases to approximately 87% in severe forms of the disease. We conducted a systematic review, including case reports and case series, of Strongyloides hyperinfection and dissemination from 1998 to 2020 searching PubMed, EBSCO and SciELO. Cases that met the inclusion criteria of the Preferred Reported Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist were analysed. Statistical analysis was performed using Fisher's exact test and Student's t-test and a Bonferroni correction for all the significant values. A total of 339 cases were included in this review. The mortality rate was 44.83%. The presence of infectious complications, septic shock and a lack of treatment were risk factors for a fatal outcome. Eosinophilia and ivermectin treatment were associated with an improved outcome.

Severe Strongyloides stercoralis infection in kidney transplant recipients: A multicenter case-control study

BACKGROUND

Severe Strongyloides stercoralis infection in kidney transplant recipients is associated with considerable morbidity and mortality, although little is known about the risk factors for such infection.

METHODOLOGY/PRINCIPAL FINDINGS

This was a retrospective, multicenter, case-control study in which we assessed the risk factors for and clinical outcomes of severe S. stercoralis infections in kidney transplant recipients in Brazil. We included 138 kidney transplant recipients: 46 cases and 92 controls. Among the cases, the median number of days from transplantation to diagnosis was 117 (interquartile range [IQR], 73.5-965) and the most common clinical findings were gastrointestinal symptoms (in 78.3%) and respiratory symptoms (in 39.1%), whereas fever and eosinophilia were seen in only 32.6% and 43.5%, respectively. The 30-day all-cause mortality among the cases was 28.3% overall and was significantly higher among the cases of infection occurring within the first three months after transplantation (47% vs. 17.2%, P = 0.04). The independent risk factors were receiving a transplant from a deceased donor (odds ratio [OR] = 6.16, 95% confidence interval [CI] = 2.05-18.5), a history of bacterial infection (OR = 3.04, 95% CI = 1.2-7.5), and a cumulative corticosteroid dose (OR = 1.005, 95% CI = 1.001-1.009). The independent predictors of mortality were respiratory failure (OR = 98.33, 95% CI = 4.46-2169.77) and concomitant bacteremia (OR = 413.00, 95% CI = 4.83-35316.61).

CONCLUSIONS/SIGNIFICANCE

Severe S. stercoralis infections are associated with considerable morbidity and mortality after kidney transplantation. In endemic areas, such infection may occur late after transplantation, although it seems to be more severe when it occurs earlier after transplantation. Specific risk factors and clinical manifestations can identify patients at risk, who should receive prophylaxis or early treatment.

Ivermectin versus albendazole or thiabendazole for Strongyloides stercoralis infection

BACKGROUND

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

OBJECTIVES

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

SEARCH METHODS

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

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

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

MAIN RESULTS

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

AUTHORS' CONCLUSIONS

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

Strongyloides stercoralis Infection in Alcoholic Patients

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

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.

Strongyloidiasis with emphasis on human infections and its different clinical forms

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

Severe strongyloidiasis: a systematic review of case reports

BACKGROUND

Strongyloidiasis is commonly a clinically unapparent, chronic infection, but immuno suppressed subjects can develop fatal disease. We carried out a review of literature on hyperinfection syndrome (HS) and disseminated strongyloidiasis (DS), in order to describe the most challenging aspects of severe strongyloidiasis.

METHODS

We conducted a structured search using PubMed to collect case reports and short case series on HS/DS published from 1991 to 2011. We restricted search to papers in English, Spanish, Italian and French. Case reports were classified as HS/DS according to given definitions.

RESULTS

Records screened were 821, and 311 were excluded through titles and abstract evaluation. Of 510 full-text articles assessed for eligibility, 213 were included in qualitative analysis. As some of them were short case series, eventually the number of cases analyzed was 244.Steroids represented the main trigger predisposing to HS and DS (67% cases): they were mostly administered to treat underlying conditions (e.g. lymphomas, rheumatic diseases). However, sometimes steroids were empirically prescribed to treat signs and symptoms caused by unsuspected/unrecognized strongyloidiasis. Diagnosis was obtained by microscopy examination in 100% cases, while serology was done in a few cases (6.5%). Only in 3/29 cases of solid organ/bone marrow transplantation there is mention of pre-transplant serological screening. Therapeutic regimens were different in terms of drugs selection and combination, administration route and duration. Similar fatality rate was observed between patients with DS (68.5%) and HS (60%).

CONCLUSIONS

Proper screening (which must include serology) is mandatory in high - risk patients, for instance candidates to immunosuppressive medications, currently or previously living in endemic countries. In some cases, presumptive treatment might be justified. Ivermectin is the gold standard for treatment, although the optimal dosage is not clearly defined in case of HS/DS.

Imported strongyloidiasis: epidemiology, presentations, and treatment

Strongyloidiasis is extremely more frequent in immigrants than in travellers. Clinical presentations do not differ significantly between the two groups, and the most frequent picture is a chronic infection characterized by intermittent, mild, non-specific symptoms. Acute presentation is rare but it has been reported in travellers. Screening of asymptomatic subjects is not generally recommended, while a presumptive treatment with ivermectin might be justified for all travellers and immigrant patients presenting unexplained eosinophilia and/or compatible symptoms, even in case of negative test results. In fact, delayed diagnosis and treatment has life-threatening consequences in patients with conditions predisposing to development of hyperinfection and dissemination.

Successful treatment of Strongyloides stercoralis hyperinfection in a case of systemic lupus erythematosus - review of the literature regarding various treatment schedules

Strongyloides stercoralis hyperinfection poses a great challenge to physicians in the tropics due to their non-specific symptoms and signs. Early identification and initiation of treatment improves mortality rates. Reports of Strongyloides infection in Hansens disease, systemic lupus erythematosus (SLE), organ transplant recipients and malnourished individuals have been reported in the published literature. The outcomes were variable, which may be attributed to a lack of treatment protocol. Treatment has been individualized and reports available are based on individual case reports and small case series. We report a successfully treated case of hyperinfection in SLE and discuss the various treatment options available.

Update on strongyloidiasis in the immunocompromised host

Immunocompromised persons are the most vulnerable population at risk for developing life-threatening clinical syndromes associated with strongyloidiasis, such as hyperinfection syndrome (HS) or dissemination. This review focuses on describing Strongyloides infection in the immunocompromised host, including immune response against this infection, analyzing the cases with HS published during the past 4 years in the United States, and describing the most sensitive diagnostic tools and the most effective treatment for each clinical syndrome. Strongyloidiasis is becoming an important parasitic disease in the United States, especially in the immunocompromised immigrant population. Because the transplant population is particularly at risk for developing HS, both recipients and donors should be screened for Strongyloides. Clinicians should also be aware that the development of HS can follow unexpectedly a few days after appropriate anthelminthic therapy. Highly sensitive screening tests are still not available in the major tertiary medical centers. Parenteral ivermectin has been used in some severe cases. Further therapy developments and improving diagnostic tools are warranted.

Strongyloides stercoralis: there but not seen

PURPOSE OF REVIEW

Diagnosis of Strongyloides stercoralis is often delayed owing to patients presenting with nonspecific gastrointestinal complaints, a low parasite load and irregular larval output. Although several diagnostic methods exist to detect the presence of S. stercoralis there is no gold standard. In immunocompromised hosts (patients with malignancy, organ transplantation or concurrent human T-cell-lymphocytic virus 1 infection or those on corticosteroid therapy), autoinfection can go unchecked with large numbers of invasive Strongyloides larvae disseminating widely and causing hyperinfection with dissemination, which can be fatal. This review will highlight current published research on improved diagnostic methods for S. stercoralis and the immune mechanisms thought to be responsible for hyperinfection syndrome.

RECENT FINDINGS

Recent advances in diagnosis of S. stercoralis include a luciferase immunoprecipitation system that shows increased sensitivity and specificity to detect S. stercoralis-specific antibodies and a real-time quantitative PCR method to detect S. stercoralis in fecal samples. The severe clinical manifestations of S. stercoralis observed in human T-cell-lymphocytic virus 1 coinfected patients has been associated with an increased proportion of regulatory T cells that may be responsible for blunting otherwise effective granulocyte responses.

SUMMARY

Strongyloidiasis is a major global health challenge that is underestimated in many countries. Novel diagnostic methods are expected to improve epidemiological studies and control efforts for prevention and treatment of strongyloidiasis. More studies are needed to unveil the mechanisms of severe clinical manifestations of human strongyloidiasis.

Non-oral treatment with ivermectin for disseminated strongyloidiasis

Critically ill patients with disseminated strongyloidiasis may not be candidates for oral treatment. We report four patients with disseminated strongyloidiasis, believed to be unable to absorb oral therapy, who were treated with ivermectin by rectal and/or subcutaneous administration. Obtaining subcutaneous ivermectin and dosing it appropriately is a challenge. These cases underscore the need for improved access to subcutaneous ivermectin and more pharmacological data to guide use of this treatment approach.

Strongyloides stercoralis and the immune response

The immune system is a highly evolved network of cells and molecules that can distinguish between invading pathogens and the body's own cells. But helminths, in their complex forms, are capable of down-regulating host immunity, protecting them from being eliminated and also minimizing severe pathology in the host. This review focuses on Strongyloides stercoralis and the immune responses in immunocompetent and/or immunocompromised individuals. It also highlights the implications for diagnosis/treatment and draws attention to an emerging public health disease. The solution to reducing the prevalence of strongyloidiasis remains on the effectiveness of pre-emptive measures in endemic communities, increased awareness, prompt early diagnosis as well as timely treatment.