Impact of preventive chemotherapy on Strongyloides stercoralis: A systematic review and meta-analysis

Dynamics of anti-Strongyloides IgG antibody responses and implications for strongyloidiasis surveillance in rural Amazonians: A population-based panel data analysis

BACKGROUND

Human strongyloidiasis was recently incorporated into the World Health Organization roadmap for neglected tropical diseases targeted for control in 2021-2030. However, the prevalence, incidence, and clinical burden of Strongyloides stercoralis infection remain understudied in remote communities across the Amazon due to its chronic nature, usually with absent or unspecific clinical manifestations, and the lack of practical and sensitive diagnostics for large-scale use. Here, we apply repeated antibody testing to estimate the prevalence of anti-Strongyloides IgG responses and identify incident infections in five farming settlements in the Amazonas State of Brazil.

METHODOLOGY/PRINCIPAL FINDINGS

We used an in-house enzyme immunoassay, with a S. venezuelensis larval extract as the solid-phase antigen, to detect specific IgG antibodies in 898 plasma samples collected during consecutive cross-sectional surveys over 4 years from 426 study participants aged >3 months, with an average of 35.9 years. Overall, 465 (51.8%) samples tested positive. However, only two infections that had been detected by fecal microscopy at survey 1 (March-May 2010) were treated with ivermectin. Antibody prevalence rose from 45.9% in 2010 to 61.1% in 2013, consistent with an increased (re)exposure to infective larvae over time. On average, there were 24.5 seroconversion events (a proxy of recent exposure to infection) per 100 person-years of follow-up, with 18.1 seroreversion events per 100 person-years. Nearly all participants with high antibody levels (i.e., above the median absorbance of seropositive tests) remained seropositive over the next years, with a single instance of high-to-nil antibody transition. Long-lasting high-level IgG responses were most likely due to frequent re-exposure to infective S. stercoralis larvae, chronic carriage of adult worms in the absence of treatment, or both. Conversely, over one-third of participants with low anti-Strongyloides antibody levels had transient IgG responses and seroreversed within 12 months.

CONCLUSIONS/SIGNIFICANCE

The results support the use of repeated antibody testing for monitoring temporal changes in S. stercoralis transmission in remote populations.

Review of the WHO guideline on preventive chemotherapy for public health control of strongyloidiasis

Strongyloidiasis is a soil-transmitted helminthiasis that is estimated to affect 300-600 million people across Asia, Africa, South and central America, and the Pacific. This neglected parasitic disease is most known for its ability to persist as a lifelong infection due to autoinfection and its risk of hyperinfection and disseminated disease during immunosuppression, which has a more than 60% case fatality. Despite the large global burden of strongyloidiasis, there have been no large-scale public health programmes or WHO guidelines directed towards its control and elimination. However, over the past decade, key scientific and policy changes along with requests from endemic countries have led to WHO incorporating strongyloidiasis into its 2021-30 roadmap and public health targets for control and elimination of neglected tropical diseases. In 2024, WHO published its first guideline on public health control of strongyloidiasis with a single recommendation: in endemic settings with a Strongyloides stercoralis infection prevalence of 5% or higher (measured either with Baermann or agar plate culture from stool specimens), WHO conditionally recommends mass drug administration with single-dose ivermectin (200 μg/kg; oral therapy) in all age groups from 5 years and older to reduce strongyloidiasis. This Review, written by the 2023-24 strongyloidiasis guidelines development group along with WHO colleagues and international experts, presents a summary of the recently published WHO guideline recommendation for strongyloidiasis, and the supporting evidence, considerations for public health implementation, and future research needs.

Molecular detection of Strongyloides stercoralis: Emerging factors and diagnostic utility

Strongyloides stercoralis infection, a neglected tropical disease, poses a significant public health threat, especially in immunocompromised individuals. This parasitic nematode can establish chronic infections, potentially progressing to life-threatening conditions such as hyperinfection syndrome and disseminated disease. Timely and accurate diagnosis is critical for effective treatment and the prevention of severe complications. Traditional diagnostic methods, such as stool microscopy, are limited by low sensitivity, particularly for detecting low-intensity infections. Advances in molecular diagnostics, particularly Polymerase Chain Reaction (PCR), have significantly improved sensitivity and specificity, marking a pivotal shift in detection capabilities. However, critical barriers persist, including inconsistencies in sample collection and handling, geographic variations in parasite strains, and the impact of genetic diversity on assay performance. Emerging molecular technologies, such as real-time PCR, loop-mediated isothermal amplification (LAMP), and droplet digital PCR (ddPCR) hold significant promise for further enhancing diagnostic precision. These advanced methods provide opportunities for more robust and accessible diagnostics, particularly in resource-limited settings. To maximize their potential, it is imperative to address existing challenges through the standardization of protocols, optimization of sample handling procedures, and the development of high-quality, reliable reagents. By overcoming these obstacles, molecular diagnostics can be more effectively integrated into clinical and public health frameworks, facilitating improved management and control of S. stercoralis infection, ultimately reducing the morbidity and mitigating the global burden of this neglected tropical disease.

Ivermectin vs moxidectin for treating Strongyloides stercoralis infection: a systematic review

The aim was to assess the efficacy of ivermectin vs moxidectin for treating Strongyloides stercoralis infection. Ovid MEDLINE, Embase and Web of Science databases were searched for studies comparing ivermectin and moxidectin from inception to February 2024. The outcomes: elimination of infection or parasitological cure, mortality and serious adverse events. We calculated odds ratios (ORs) with 95% confidence intervals (CIs) for dichotomous data. Heterogeneity was assessed using Chi2 test for statistical heterogeneity and results of the I2 statistic. Two trials met the inclusion criteria that included 821 adult participants. Both studies were conducted in southeast Asia (Cambodia and Laos). Neither trial included immunocompromised patients. The mean age of the participants ranged from 40 to 45 years old, with a similar distribution of males and females. For all participants, S. stercoralis infection was confirmed by Baermann method. The evidence was moderate for parasitological cure rate. Certainty was downgraded by 1 level because of imprecision. Moxidectin was not inferior to ivermectin: OR 0.67, 95% CI 0.36–1.25 (P = 0.21), I2 = 0%, 821 participants. No deaths were reported in either trial. One trial reported mild adverse events. In total, 153/726 (21%) participants had an adverse event. The most reported symptoms were abdominal pain and headache. There is evidence for moderate quality that moxidectin is non-inferior to, and as safe as ivermectin; however, more high-quality and well-designed trials are needed. For patients with some underlying immunosuppressive disorder, or in patients who are very young or very old, current data are insufficient to be recommended.

Prevalence of Strongyloides stercoralis and other helminths in four districts of Madagascar

BACKGROUND

Estimation of prevalence of Strongyloides stercoralis infection is required in endemic areas, in order to identify areas in need of control programmes. Data on prevalence of strongyloidiasis in Madagascar are scant. Aim of this work was to estimate prevalence of S. stercoralis in four districts of Madagascar.

METHODS

Fecal and serum samples collected in the context of a previous study on schistosomiasis were tested with S. stercoralis real-time PCR and serology, respectively. A multiplex real-time PCR for Ascaris lumbricoides, Ancylostoma duodenalis, Necator americanus, and Trichuris trichiura was done on fecal samples collected in the areas demonstrating higher prevalence of strongyloidiasis. Comparisons between proportions were made using Fisher exact test, with false discovery rate correction used for post-hoc comparisons. A multivariable Firth logistic regression model was used to assess potential risk factors for S. stercoralis infection.

RESULTS

Overall, 1775 serum samples were tested, of which 102 of 487 (20.9%) and 104 of 296 (35.2%) were serological-positive in Marovoay and in Vatomandry districts (both coastal areas), respectively, compared to 28 of 496 (5.6%) and 30 of 496 (6.1%) in Tsiroanomandidy and in Ambositra districts (both highlands), respectively (adj. p < 0.001). PCR for S. stercoralis was positive in 15 of 210 (7.1%) and in 11 of 296 (3.7%) samples from Marovoay from Vatomandry, respectively, while was negative for all samples tested in the other two districts. High prevalence of A. lumbricoides (45.9%), hookworm (44.6%) and T. trichiura (32.1%) was found in Vatomandry. In the multivariable analysis, strongyloidiasis was associated with hookworm infection. Hookworm infection was also associated with male sex and lower education level.

CONCLUSIONS

S. stercoralis prevalence proved higher in coastal areas compared to highlands. Different climatic conditions may explain this distribution, along with previous rounds of anthelminthics distributed in the country, which may have reduced the parasite load in the population. The high prevalence of the other soil-transmitted helminths (STH) in Vatomandry was unexpected, given the good coverage with benzimidazole in control campaigns. Further studies are needed to explore the risk factors for STH and S. stercoralis infections in Madagascar, in order to align with the WHO recommendations.

Skin and soft tissue infections in solid organ transplants

PURPOSE OF REVIEW

Skin and soft tissue infections (SSTI) in solid organ transplant (SOT) recipients may be a great challenge for clinicians caring for SOT due to the involvement of both common and opportunistic pathogens associated with a blunted immune response. The purpose of this review is to outline current literature and describe open issues on the management of SSTI in this special population.

RECENT FINDINGS

Clinical presentation in SOT recipients can manifest as isolated skin lesions after primary inoculation or be the sign of a disseminated infection. Tissue samples for microscopy and histopathology are crucial to making an accurate diagnosis given the nonspecific and heterogeneous appearance of skin lesions. Multidisciplinary teams are required for a comprehensive diagnosis and management.

SUMMARY

SSTI are frequent contributors to morbidity and mortality in SOT. Specific research focused on the clinical presentation, risk factors and management in this special population is needed.

Effectiveness of ivermectin mass drug administration in the control of soil-transmitted helminth infections in endemic populations: a systematic review and meta-analysis

BACKGROUND

Current soil-transmitted helminth (STH) control guidelines endorse the use of albendazole or mebendazole for school-based targeted preventive chemotherapy (PC), yet their reduced efficacy against Strongyloides stercoralis and Trichuris trichiura presents significant limitations. Emerging evidence indicates that community-wide PC [or mass drug administration (MDA)] using ivermectin, commonly used in other neglected tropical disease (NTD) control programs, may play an important role in controlling these parasites. We conducted a systematic review and meta-analysis to evaluate the effectiveness of ivermectin PC in reducing STH prevalence in endemic populations.

METHODS

We searched Pubmed, EMBASE, and Web of Science on February 14, 2023, for studies that investigated the effectiveness of ivermectin PC, either alone or in combination with other anthelmintic drugs, on STH infections, and provided a measure of STH prevalence before and after PC. We calculated pooled prevalence reductions for each STH using random-effects meta-analyses. Our protocol is available on PROSPERO (registration number CRD42023401219).

RESULTS

A total of 21 were eligible for the systematic review, of which 15 were eligible for meta-analysis. All studies delivered ivermectin through MDA. The pooled prevalence reduction of S. stercoralis following MDA with ivermectin alone was 84.49% (95% CI 54.96-94.66) across five studies and 81.37% (95% CI 61.62-90.96) across seven studies with or without albendazole. The prevalence reduction of T. trichiura was 49.93% (95% CI 18.23-69.34) across five studies with ivermectin alone, and 89.40% (95% CI 73.66-95.73) across three studies with the addition of albendazole. There was high heterogeneity for all syntheses (I2 > 65%).

CONCLUSIONS

This study underscores the key role of ivermectin-based MDA in addressing limitations in current global STH guidelines in terms of limited efficacy against S. stercoralis and T. trichiura. Based on these findings, revising international STH guidelines to include ivermectin is a promising option to progress the control and eventual elimination of STHs and other NTDs.