Efficacy of Single Dose Ivermectin Against Strongyloides stercoralis Infection Among Primary School Children in Amhara National Regional State

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.

Strongyloidiasis in Children Outside the Tropics: Do We Need to Increase Awareness?

Strongyloidiasis belongs to the group of neglected tropical diseases, due to diagnostic difficulties and the lack of systematic screening. Studies on strongyloidiasis prevalence are often heterogenous and mainly performed in adults in endemic countries. We retrospectively enrolled 2633 children referred to a tertiary care hospital in Italy between 2009 and 2020 and tested for S. stercoralis infection. Sixty-one (2.3%) had a positive serology and for 55 of them, clinical and epidemiological information were available. Thirteen cases (24%) were diagnosed in Italian children without history residency or travel to foreign countries, while the remaining were internationally adopted or migrant children. Seropositive patients were mostly asymptomatic, and often eosinophilia was the only sign of strongyloidiasis. Sero-reactivity to Toxocara canis was found in 1/3 of patients. Ivermectin was used in 37 (75.5%) treated patients. A significant reduction of eosinophil levels and IgG titer was seen after treatment. Our study confirms that strongyloidiasis is usually asymptomatic in children. However, due to the ability of the parasite to cause a life-long infection together with the risk of a severe form in case of immunosuppression, it is important to identify and treat infected children. Special consideration should be reserved to high-risk groups, such as immigrants and international adoptees, where screening for S. stercoralis is indicated. However, the study highlights that sporadic cases of autochthonous strongyloidiasis in Italy may occur. Therefore, pediatricians should be aware of this condition, which is often under-recognized.

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.

Strongyloides Stercoralis Infection in Ethiopia: Systematic Review and Meta-analysis on Prevalence and Diagnostic Methods

Strongyloides stercoralis is a helminthic intestinal parasite that causes the disease strongyloidiasis. Its prevalence is high in tropics and sub-tropics due to poor sanitation and hygiene. However, its true prevalence is not well known in Ethiopia as most health institutions use low sensitive diagnostic methods. This review aimed to determine the pooled prevalence of S. stercoralis at country, and regional state levels. Papers published on S. stercoralis in Ethiopia from 2010 to 2020 were collected from PubMed, Google Scholar and Science direct databases and Addis Ababa repository. Identification, screening, checking the eligibility, and inclusion of the relevant literatures were done. Articles with S. stercoralis positive results from Ethiopian populations were included. Articles which focused on Strongyloides infection in foreigners, and other than stool samples were excluded. The pooled prevalence of S. stercoralis and heterogeneity between studies and across regions were computed. From the 43 articles, the overall prevalence of S. stercoralis in Ethiopia was 1.82 %. Across regions, relatively high prevalence of S. stercoralis (8.78 %) was recorded in Addis Ababa city. High prevalence of S. stercoralis was found to be 44.02 % with a combination of formol ether concentration, Baermann concentration, and molecular methods. Low prevalence of 0.26 %, 0.31 %, and 1.20 % was evidenced respectively with Kato-Katz, direct saline microscopy, and formol ether concentration methods. Using random effect analysis, the pooled prevalence of S. stercoralis in Ethiopia, across regions and across diagnostic methods was 2.1 % (95 %CI: 1.20 – 3.60), 2.6 % (95 %CI: 0.80 – 8.20) and 3.7 % (95 %CI: 1.10 – 11.70), respectively. The heterogeneity was high (P<0.001). This review revealed that Strongyloides infection is probably underreported and its prevalence could be higher than the reported in Ethiopia. Therefore, a revision of the best combination of diagnostic methods could be advisable as it gives better diagnostic results in routine diagnosis of Strongyloides infection in Ethiopia.

Performance evaluation of Baermann techniques: The quest for developing a microscopy reference standard for the diagnosis of Strongyloides stercoralis

BACKGROUND

Soil-transmitted helminths (STH) are common in low and middle income countries where there is lack of access to clean water and sanitation. Effective diagnosis and treatment are essential for the control of STH infections. However, among STH parasites, Strongyloides stercoralis is the most neglected species, both in diagnostics and control strategies. Diagnostic methods cover different approaches, each with different sensitivities and specificities, such as serology, molecular techniques and microscopy based techniques. Of the later, the Baermann technique is the most commonly used procedure. In the literature, several ways have been described to perform the Baermann method, which illustrates the overall lack of a '(gold) reference standard' method for the diagnosis of S. stercoralis infection. In this study we have evaluated the performance of three Baermann techniques in order to improve the reference standard for the microscopic diagnosis of S. stercoralis infection thereby facilitating individual case detection, mapping of the disease and proper evaluation of treatment responses.

METHODS/PRINCIPAL FINDINGS

A community based cross sectional study was conducted at Zenzelima, Bahir Dar Zuria Ethiopia. A total of 437 stool samples were collected and analyzed by the following procedures: conventional Baermann (CB), modified Baermann (MB), and modified Baermann with charcoal pre-incubation (MBCI). The diagnostic sensitivity and Negative Predictive Value (NPV) of each technique was calculated using the combination of all the three techniques as a composite reference standard. Our result indicated that larvae of S. stercoralis were detected in 151 (34.6%) stool samples. The prevalence of S. stercoralis infection based on the three diagnostic methods was 9.6%, 8.0%, and 31.3% by CB, MB, and MBCI respectively. The sensitivity and NPV for CB, MB, and MBCI were 26.7% and 70.8%, 22.1% and 69.6%, and 87.0% and 93.2%, respectively. The MBCI showed significant difference (P- value = <0.001) in the sensitivity and NPV values when compared with CB and MB values. The agreement between CB, MB, and MBCI with the composite reference standard was 31.8%, 26.7%, 89.6%, respectively.

CONCLUSION/SIGNIFICANCE

Our results suggest the superior performance of MBCI. It is relatively easy to implement, simple to perform and comparatively cheaper. The CB is by far the commonly used method in routine diagnostic although this technique significantly underestimates the true burden of the disease and thereby contributing to the exclusion of S. stercoralis from the control strategies. Therefore, MBCI is recommended as a routine microscopy-based diagnostic test for S. stercoralis infection, particularly in settings where molecular procedures are not available.