High prevalence of Strongyloides stercoralis in school-aged children in a rural highland of north-western Ethiopia: the role of intensive diagnostic work-up

First field study using Strong-LAMP for diagnosis of strongyloidiasis in Cubal, Angola

BACKGROUND

Strongyloides stercoralis infection is a common neglected tropical disease distributed worldwide, mainly in tropical and subtropical climates. The impact of S. stercoralis infections on human health ranges from mild asymptomatic infections to chronic strongyloidiasis unnoticeable until the host is immunosuppressed. In severe strongyloidiasis, a syndrome of hyperinfection and larval dissemination to various organs can occur with high mortality rates. The diagnosis of strongyloidiasis is challenging because of the absence of a single standard reference test with high sensitivity and specificity, which also makes it difficult to estimate the accuracy of other diagnostic tests. This study aimed to evaluate, for the first time, the use of an easy-to-perform loop-mediated isothermal amplification (LAMP) colorimetric assay (named Strong-LAMP) for the molecular screening of strongyloidiasis in stool samples from patients in a low-resource endemic area in Cubal, Angola. To compare different LAMP application scenarios, the performance of the Strong-LAMP under field conditions in Angola was reassessed in a well-equipped reference laboratory in Spain and compared with a quantitative polymerase chain reaction (qPCR) method.

METHODS

A total of 192 stool samples were collected from adult population in Cubal, Angola, and examined by parasitological methods (direct saline microscopy and Baermann's technique). DNA was extracted from each stool sample using a commercial kit and tested by the colorimetric Strong-LAMP assay for the detection of Strongyloides spp. under field conditions. Furthermore, all samples were shipped to a well-equipped laboratory in Spain, reanalysed by the same procedure and compared with a qPCR method. The overall results after testing were compared.

RESULTS

Strongyloides stercoralis larvae were identified by direct saline microscopy and Baermann in a total of 10/192 (5.2%) and 18/192 (9.4%) stool samples, respectively. Other helminth and protozoan species were also identified. The Strong-LAMP-positive results were visually detected in 69/192 (35.9%) stool samples. The comparison of Strong-LAMP results in field conditions and at a reference laboratory matched in a total of 146/192 (76.0%) samples. A total of 24/192 (12.5%) stool samples tested positive by qPCR.

CONCLUSIONS

This is the first study in which colorimetric Strong-LAMP has been clinically evaluated in a resource-poor strongyloidiasis endemic area. Strong-LAMP has been shown to be more effective in screening for strongyloidiasis than parasitological methods under field conditions and qPCR in the laboratory. Our Strong-LAMP has proven to be a field-friendly and highly accurate molecular test for the diagnosis of strongyloidiasis.

Gastroduodenal strongyloidiasis infection causing protein-losing enteropathy: A case report and review of the literature

Strongyloides stercoralis is an intestinal nematode in which adult worms in the host small intestine can cause strongyloidiasis. Symptoms in immunocompromised patients might range from diarrhea and bleeding to sepsis and even death. A 56-year-old patient presented with a 2-month history of weight loss, vomiting, and diarrhea. The patient had type 2 diabetes mellitus (T2DM) and was on long-term prednisone for chronic kidney disease. The results of the gastric emptying test and head magnetic resonance (MRI) were normal. A blood test revealed increased IgE levels, eosinophilia, and hypoalbuminemia. Parasitic larvae were not discovered during stool analysis. Gastroscopy revealed chronic nonatrophic gastritis with erosions and dilation of lymphatic vessels of the duodenum. Small-bowel capsule endoscopy suggested dilation of lymphatic vessels of the small intestine. Colonoscopy revealed no abnormalities. Finally, a histopathology examination identified S. stercoralis pervasion in the gastric antrum and duodenum. The patient was treated with albendazole and discharged successfully. In conclusion, we discovered S. stercoralis as a cause of protein-losing enteropathy in a patient with a long-term oral corticosteroid therapy and T2DM. The diagnosis was made through histopathology, once parasitological examination was negative. Therefore, health professionals should stay alert to S. stercoralis infection in immunocompromised patients with vague gastrointestinal symptoms. More sensitive methods should be applied in the diagnosis.

From past to present: opportunities and trends in the molecular detection and diagnosis of Strongyloides stercoralis

Strongyloides stercoralis is a soil-transmitted helminth that is mainly found in the tropical and subtropical regions and affects approximately 600 million people globally. The medical importance of strongyloidiasis lies in its capacity to remain asymptomatic and chronically unnoticed until the host is immunocompromised. Additionally, in severe strongyloidiasis, hyperinfection syndrome and larva dissemination to various organs can occur. Parasitological techniques such as Baermann-Moraes and agar plate culture to detect larvae in stool samples are the current gold standard. However, the sensitivity might be inadequate, especially with reduced worm burden. Complementing parasitological techniques, immunological techniques including immunoblot and immunosorbent assays are employed, with higher sensitivity. However, cross-reactivity to other parasites may occur, hampering the assay's specificity. Recently, advances in molecular techniques such as polymerase chain reaction and next-generation sequencing technology have provided the opportunity to detect parasite DNA in stool, blood, and environmental samples. Molecular techniques, known for their high sensitivity and specificity, have the potential to circumvent some of the challenges associated with chronicity and intermittent larval output for increased detection. Here, as S. stercoralis was recently included by the World Health Organization as another soil-transmitted helminth targeted for control from 2021 to 2030, we aimed to present a review of the current molecular techniques for detecting and diagnosing S. stercoralis in a bid to consolidate the molecular studies that have been performed. Upcoming molecular trends, especially next-generation sequencing technologies, are also discussed to increase the awareness of its potential for diagnosis and detection. Improved and novel detection methods can aid in making accurate and informed choices, especially in this era where infectious and non-infectious diseases are increasingly commonplace.

Soil-transmitted helminth infection among school-age children in Ogoja, Nigeria: implication for control

The study aimed at assessing the prevalence and risk factors of soil-transmitted helminthiases among school-aged children in Ogoja Local Government Area, Cross River State. Fecal samples were collected from 504 participants and analyzed using the Kato-Katz technique and modified Baermann technique for identifying larvae of Strongyloides. A total of 232 (46.0%) samples were positive for soil-transmitted helminths. The overall prevalence of Ascaris lumbricoides, hookworm, Trichuris trichiura, and Strongyloides stercoralis were 14.1%, 16.5%, 2.6%, and 12.9% respectively. The prevalence of infections were higher among males (46.6%) than females (45.4%). Overall, parasitic infection was higher in the 5-7-year age group (65.6%) than in the other age groups (p = 0.000). Infection intensities of A. lumbricoides (84.00 EPG) (p = 0.044) and T. trichiura (96.00 EPG) (p = 0.041) were higher in school-age children aged 14-16 years. A. lumbricoides and hookworm co-infection (8.7%) was the most common mixed infection and was significantly higher in males than females. School-aged children who did not have prior knowledge about soil-transmitted helminth infections, the habit of drinking water without boiling, open defecation, use of pit latrine, and children who did not have toilet facilities in school were significantly associated with soil-transmitted helminthiases. There was a significant relationship between washing hands after using the toilet, the habit of putting on footwear outside the house, and soil-transmitted helminth infection. In addition to preventive chemotherapy, control measures should focus on health education, providing clean drinking water, proper disposal of human excreta and sewage, and environmental hygiene.

The epidemiology of Schistosoma mansoni in the Lake Tana Basin (Ethiopia): Review with retrospective data analyses

Schistosoma mansoni is one of the major waterborne diseases grouped underwater based Neglected Tropical Diseases in Africa. In Ethiopia, the Lake Tana Basin has favorable environment (temperature and water) for S. mansoni transmission. The prevalence of S. mansoni varies among regions based on environmental conditions and human water contact. Therefore, this review was conducted to identify hot spots districts and determine the prevailing S. mansoni prevalence in the Lake Tana Basin. Research articles published in English in the last 65 years were searched from Google scholar, PubMed, and Web of science. In addition, four-year S. mansoni data that were reported in health care facilities were extracted from health management information system in 61 districts of the Lake Tana Basin. In total, 43 research articles on S. mansoni that met the inclusion criteria and were published between 1957 and 2022. Over 98% of the articles were cross-sectional studies, while five articles addressed malacological studies. Among 61 districts, 19 (31%) were identified as hotspot districts for S. mansoni infection in the Lake Tana Basin. S. mansoni prevalence and the abundance of its host snail showed spatial and seasonal variations. On average 2000 school children/year attended health care facilities for S. mansoni infection. Swimming habits [adjusted odds ratio (AOR) = 3.2, p = 0.030], irrigation practice (AOR = 3:09, p ≤ 0.001), fishing (AOR = 2:43, p = 0.005) and being male (AOR = 1.74, p = 0.002) were risk factors for contributing to S. mansoni infection. This study showed the spatial and seasonal variations of S. mansoni prevalence and its endemicity in the hottest lowland areas of the Lake Tana Basin. The research articles on S. mansoni had poor geographical coverage. Malacological studies on water bodies, assessments on knowledge and attitude in the community towards S. mansoni transmission are areas of future studies.

An adaptive phase II/III safety and efficacy randomized controlled trial of single day or three-day fixed-dose albendazole-ivermectin co-formulation versus albendazole for the treatment of Trichuris trichiura and other STH infections. ALIVE trial protocol

Background: Soil-transmitted helminths (STH) are targeted for control through mass drug-administration campaigns to prevent morbidity affecting at-risk groups in endemic regions. Although broadly successful, the use of albendazole and mebendazole achieved variable progress, with deficiencies against Trichuris trichiura and a predictable low efficacy against Strongyloides stercoralis. Novel drug combinations offer a potential solution, providing they can be delivered safely and maintain efficacy against all STH species. Here we present the protocol of a clinical trial to evaluate a fixed-dose combination (FDC) tablet containing albendazole and ivermectin that will be compared against albendazole against STH . Methods: An adaptive phase II/III randomized controlled trial will be undertaken in STH endemic sites in Ethiopia, Kenya and Mozambique to evaluate an oral FDC of 400 mg albendazole and either 9- or 18 mg ivermectin. FDC will be administered as a single dose or single doses over three-consecutive days and assessed against a single dose of 400 mg albendazole. In the phase II trial, 126 T. trichiura-infected children weighting 15 to 45 kg will be treated in a dose-escalation manner to determine safety objectives. In the phase III trial, 1097 participants aged 5 to 18 years old infected with T. trichiura, hookworm and S. stercoralis will be recruited to determine safety and efficacy. The trial will be open-label with blinded outcome assessors. Cure rate measured 21-days after-treatment in duplicate Kato-Katz is the primary efficacy outcome. Secondary objectives include efficacy evaluation by quantitative polymerase chain reaction (PCR) as an outcome measurement, description of pharmacokinetic parameters, palatability and acceptability evaluations, and monitoring of anthelmintic resistance. Conclusions: This trial with registrational goals seeks to evaluate an innovative fixed-dose combination of albendazole and ivermectin co-formulated tablets, with the goal of providing an anthelmintic regimen with improved efficacy and spectrum of coverage against STH. ClinicalTrials.gov registration: NCT05124691 (18/11/2021).

A simple parasitological technique to increase detection of Strongyloides stercoralis in Bolivian primary health care system

BACKGROUND

Strongyloides stercoralis is widespread; however, there is limited information on its prevalence owing to laboratory underestimation and low clinical manifestations. The Baermann method and agar culture stand out among the parasitological techniques. Strongyloides stercoralis is present in Bolivia, but its prevalence in children remains unknown. The objective of this study was to estimate the applicability of simple parasitological techniques to increase the detection of this parasite in children living in the tropics.

METHODS

This cross-sectional study was conducted in a tropical village in Cochabamba, Bolivia. Participants were 304 children aged 5 - 12 years who provided stool samples for different parasitological analyses (direct examination, Ritchie, Baermann, and Dancescu techniques), and their parents provided informed consent.

RESULTS

Up to 64.8% of pathogenic parasites were detected using the modified Ritchie method. The Baermann technique identified 17.8% of Strongyloides stercoralis cases, and a high sensitivity with respect to the Baermann technique was only for the Dancescu technique (75.9%) that is also specific for Strongyloides stercoralis, followed by 66.7% for the modified Ritchie technique, which is used in second-line care.

DISCUSSION

The Baermann technique is the best parasitological option for improving Strongyloides stercoralis diagnosis in the first-line care of the Primary Health Care System. A particular cycle of reinfection, combined with the environment and some other risk factors are related with persistence. Control is difficult without a proper diagnosis, and the Baermann technique is an approach to the solution. We conclude that with a high suspicion of the presence of Strongyloides stercoralis, the use of the Baermann technique is strongly recommended as support for direct examination in primary health care systems especially in tropical areas.

Ivermectin and albendazole coadministration: opportunities for strongyloidiasis control

In 2020, WHO recognised the importance of strongyloidiasis alongside soil-transmitted helminths (STH) in their 2021-30 roadmap, which aspires to target Strongyloides stercoralis with preventive chemotherapy by use of ivermectin. Combination treatment with both albendazole, the primary drug used to treat STH, and ivermectin, would improve the efficiency of mass drug administration targeting both STH and S stercoralis. In this Personal View, we discuss the challenges and opportunities towards the development of an efficient control programme for strongyloidiasis, particularly if it is to run concurrently with STH control. We argue the need to define the prevalence threshold to implement preventive chemotherapy for S stercoralis, the target populations and optimal dosing schedules, and discuss the added benefits of a fixed-dose coformulation of ivermectin and albendazole. Implementation of an efficient control programme will require improvements to current diagnostics, and validation of new diagnostics, to target and monitor S stercoralis infections, and consideration of the challenges of multispecies diagnostics for S stercoralis and STH control. Finally, the evolution of ivermectin resistance represents a credible risk to control S stercoralis; we argue that genome-wide approaches, together with improved genome resources, are needed to characterise and prevent the emergence of resistance. Overcoming these challenges will help to reduce strongyloidiasis burden and enhance the feasibility of controlling it worldwide.

The diagnosis of human and companion animal Strongyloides stercoralis infection: Challenges and solutions. A scoping review

Strongyloidiasis is the infection caused by soil-transmitted nematodes of Strongyloides species, infecting humans and some animals. Strongyloides stercoralis is the species with most clinical and epidemiological relevance in humans and dogs, due to its high prevalence and its capacity of inducing a life-threatening hyperinfection. Diagnosis of strongyloidiasis is challenging, due to the absence of a single reference standard test with high sensitivity and specificity, which also hampers the estimation of the accuracy of other diagnostic tests. In this chapter, we review the deployment and performance of the parasitological, immunological, molecular tests for the diagnosis of strongyloidiasis in humans and in dogs. Further, we comment the available evidence from genotyping studies that have addressed the zoonotic potential of S. stercoralis. Finally, we discuss the use of different diagnostic methods in relation to the purpose (i.e., screening, individual diagnosis, inclusion in a clinical trial) and the setting (endemic/non-endemic areas) and report the accuracy figures reported by systematic reviews on either parasitological, serological or molecular techniques published in literature.

Prevalence of Strongyloides stercoralis infection and associated clinical symptoms among schoolchildren living in different altitudes of Amhara National Regional State, northwest Ethiopia

Background

Strongyloides stercoralis is a parasite that causes strongyloidiasis in humans. It is prevalent in the tropics and sub-tropics where poor sanitation is a common problem. The true prevalence of S. stercoralis in Ethiopia is underestimated due to the lack of a “Gold” standard diagnostic method. Moreover, its prevalence across altitudinal gradient in Amhara Region has not been studied.

Methods

A cross-sectional study was conducted among 844 schoolchildren in Amhara Region from April to December 2019. A stool sample was collected from each study participant and processed using formol ether concentration technique (FECT), spontaneous tube sedimentation technique (STST), Baermann concentration technique (BCT), agar plate culture (APC) and real-time polymerase chain reaction (RT-PCR). Data were entered using EpiData and analyzed by SPSS version 23 statistical software. Prevalence of S. stercoralis infection was determined using a single diagnostic technique and combination of techniques. Association of clinical variables with S. stercoralis infection was assessed by logistic regression and independent variables with p<0.05 were considered statistically significant.

Results

Prevalence of soil-transmitted helminths (STHs) and S. mansoni infections was 38.0% and 20.4%, respectively. Among STHs, the prevalence of hookworm infection was 32.8%. Prevalence of S. stercoralis infection was 39.0%, 28.8%, 10.9%, 10.3%, 4.0% and 2.0% by the respective, combinations of the five methods, RT-PCR, APC, BCT, STST and FECT. The highest prevalence rates, 48.2%, 45.0% and 41.1% of S. stercoralis were recorded in the age group of 12–14 years, males and rural dwellers, respectively. Prevalence rates of S. stercoralis infection in highland, semi-highland and lowland areas were 40.4%, 41.8% and 25.9%, respectively. Having abdominal pain (AOR = 2.48; 95% CI:1.65–3.72), cough (AOR = 1.63;95%CI:1.09–2.42), urticaria (AOR = 2.49;95%CI:1.50–4.01) and being malnourished (AOR = 1.44;95%:1.10–2.01) were significantly associated with strongyloidiasis.

Conclusion

Prevalence of S. stercoralis infection was high and varied across different altitudes in Amhara Region. Some clinical syndromes were found to be significantly associated with S. stercoralis infection. Therefore, proper diagnosis and preventive strategies against S. stercoralis infection are highly recommended to be devised and implemented in Amhara Region.

Prevalence of S. stercoralis is under-reported in many resource-poor countries including Ethiopia. We carried out a school-based cross-sectional study among 844 schoolchildren across highlands, semi-highlands and lowland areas of Amhara Region. We used an approach made of five diagnostic methods, namely, FECT, STST, BCT, APC, and RT-PCR. The total prevalence of S. stercoralis was 39.0%. The highest S. stercoralis prevalence (41.8%) was observed in the semi-highland areas of the region. Strongyloidiasis was significantly higher among 12–14 years age groups, males, and rural dweller children. Clinical symptoms such as presence of abdominal pain, cough, skin rash and malnourishment were significantly associated with strongyloidiasis. We recommend that preventive strategies against strongyloidiasis in Amhara Region should be implemented.

Evaluation of five diagnostic methods for Strongyloides stercoralis infection in Amhara National Regional State, northwest Ethiopia

Background

Strongyloides stercoralis is an intestinal parasite that can cause chronic infection, hyperinfection and/or a dissemination syndrome in humans. The use of techniques targeting ova fails to detect S. stercoralis, as only larvae of the parasite are excreted in faeces. Due to the absence of “Gold” standard diagnostic method for S. stercoralis, there is a paucity of reported data worldwide.

Objective

This study aimed to evaluate the performance of diagnostic methods of S. stercoralis infection by taking the composite reference as a “Gold” standard.

Methods

A cross-sectional study was conducted among 844 schoolchildren in Amhara Region, Ethiopia, from April to December 2019. Stool samples were collected and processed with formol-ether concentration technique (FECT), spontaneous tube sedimentation technique (STST), Baermann concentration technique (BCT), agar plate culture (APC) and real-time polymerase chain reaction (RT-PCR). Sensitivity, specificity, positive predictive value, and negative predictive value of each diagnostic method were computed against the composite reference. The agreements of diagnostic methods were evaluated by Kappa value at 95% CI.

Results

The composite detection rate of S. stercoralis by the five diagnostic methods was 39.0% (329/844). The detection rate of the parasite from stool samples by FECT, STST, BCT, APC and RT-PCR was 2.0% (17/844), 4.0% (34/844), 10.2% (86/844), 10.9% (92/844) and 28.8% (243/844), respectively. The highest detection rate (37.8%; 319/844) of S. stercoralis was recorded by a combination of BCT, APC, and RT-PCR followed by a combination of STST, BCT, APC and RT-PCR (37.3%; 315/844). The sensitivity of FECT, STST, BCT, APC and RT-PCR against the composite reference was 5.2%, 10.3%, 26.4%, 28.0% and 73.9%, respectively. The diagnostic agreements of RT-PCR, APC, BCT, STST and FECT with the composite reference in detection of S. stercoralis were substantial (0.775), fair (0.321), fair (0.305), slight (0.123), and slight (0.062), respectively.

Conclusion

RT-PCR detected the highest number of S. stercoralis infections. A combination of RT-PCR with APC and/or BCT better detected S. stercoralis from stool samples compared to other combinations or single diagnostic methods. Therefore, RT-PCR and combination of RT-PCR with APC and/or BCT diagnostic methods should be advocated for detection of S. stercoralis infection.

Prevalence of soil-transmitted helminths infections among preschool and school-age children in Ethiopia: a systematic review and meta-analysis

BACKGROUND

There is a lack of comprehensive national data on prevalence, geographical distribution of different species, and temporal trends in soil-helminthiasis (STHs). Therefore, this study aimed to provide a summary and location of the available data on STHs infection among preschool and school-age children in Ethiopia.

METHODS

The search was carried out in Medline via PubMed, Scopus, Science Direct, Web of Science, and Google Scholar on data published between 1997 to February 2020 for studies describing the rate of STHs infection among preschool and school-age in Ethiopian. We followed the Patient, Intervention, Comparison, and Outcome (PICO) approach to identify the studies. Meta-regression was performed to understand the trends and to summarize the prevalence using the "metaprop" command using STATA software version 14.0 RESULTS: A total of 29,311 of the 61,690 children examined during the period under review were infected with one or more species of intestinal parasites yielding an overall prevalence of 48% (95% CI: 43-53%). The overall pooled estimate of STHs was 33% (95% CI: 28-38%). The prevalence was 44% (95% CI: 31-58%) in SNNPR, 34% (95% CI: 28-41%) in Amhara region, 31% (95% CI: 19-43%) in Oromia region and 10% (95% CI: 7-12%) in Tigray region. Soil-transmitted helminths infection rate has been decreasing from 44% (95% CI: 30-57%) pre-Mass Drug Administration (MDA) era (1997-2012) to 30% (95% CI: 25-34%) post-MDA (2013-2020), although statistically not significant (p = 0.45). A lumbricoides was the predominant species with a prevalence of 17%.

CONCLUSION

Southern Nations Nationalities and Peoples Region, Amhara, and Oromia regions carry the highest-burden and are categorized to Moderate Risk Zones (MRZ) and therefore, requiring MDA once annually with Albendazole or Mebendazole. The prevalence of STHs decreased after MDA compared to before MDA, but the decline was not statistically significant. A. lumbricoides was the predominant species of STHs among preschool and school-age children in Ethiopia. The high prevalence of STHs observed in this review, underscores the need for better control and prevention strategies in Ethiopia.

Determinant factors of chronic Strongyloides stercoralis infection among schoolchildren in Amhara National Regional State, northwest Ethiopia

BACKGROUND

Strongyloides stercoralis is one of the most neglected parasites that is commonly found in tropical and sub-tropical countries. The majority of chronic S. stercoralis infections are characterized by minor clinical signs and symptoms. The extent to which socio-demographic, personal and environmental risk factors associated with S. stercoralis infection is not well known in Amhara Regional, Ethiopia.

OBJECTIVE

This study aimed to assess socio-demographic, personal and environmental risk factors associated with S. stercoralis infection among schoolchildren in Amhara Region.

METHODS

A total of 844 schoolchildren were randomly selected and participated in the study. Stool samples were collected and checked for S. stercoralis infection using five diagnostic methods. A structured questionnaire was also used to obtain socio-demographic, personal and environmental data from parents of the children. The degree of association between socio-demographic, personal and environmental factors with S. stercoralis infection was first assessed by univariate logistic regression and then analyzed by multivariate logistic regression. Variables with p<0.05 were considered as statistically significant.

RESULTS

Among 844 participants, 329 (39.0%) were infected with S. stercoralis. Prevalences of S. stercoralis among 12-14 years old, males, and rural dwellers were 48.2% (109/226), 45.0% (196/436) and 41.1% (306/745), respectively. Being in the age group of 10-11years (AOR=1.56;95%CI:1.10-2.24), and 12-14 years (AOR=1.96;95%CI:1.32-2.90), male (AOR=1.55;95%CI:1.16-2.06), and rural dweller (AOR=1.86;95%CI:1.12-3.10); having family income of < 1000 Birr per month (AOR=2.03;95%CI:1.48-2.77), and family size of 5-9 members (AOR=2.36; 95%CI:1.57-3.54) were significantly associated with S. stercoralis infection. The habit of not wearing shoes (AOR=1.41; 95%CI:1.05-1.90), close contacting with pets (AOR=1.49;95%:1.09-2.04), participating in irrigation (AOR=1.49; 95%CI:1.10-2.00) and playing with soil (AOR=1.62;95%CI:1.20-2.18) were risk factors of S. stercoralis infection. Besides, presence of wet environment (AOR=1.62;95%CI:1.19-2.22), living around sandy soil (AOR=2.75; 95%CI: 1.81-4.19) and red clay soil (AOR=2.24;95%CI:1.58-3.17), living in semi-highland folds (AOR=2.47;95%CI:1.48-4.14) and highland areas (AOR=1.65;95%CI:1.06-2.57) were determinant factors for S. stercoralis.

CONCLUSION

S. stercoralis infection among schoolchildren was highly prevalent in Amhara Region. Several determinant factors were also identified. Therefore, proper implementation of sanitation and hygiene programs and health care of pets should be advocated to break the transmission cycle of S. stercoralis.

Prevalence and risk factors of strongyloidiasis among schoolchildren in Sabach Sanjal and Upper Badibou districts in the North Bank East Region of The Gambia

Background

Strongyloidiasis is a parasitic disease that mainly affects humans and is caused by a roundworm called Strongyloides stercoralis. It is endemic in humid tropical regions that include Africa, Latin America and Southern Asia. Among the public health important soil-transmitted helminths (STHs) classified as neglected tropical diseases, S. stercoralis is the most neglected. A study of schistosomiasis and STHs mapping was conducted and S. stercoralis larvae were detected using the utilized diagnostic method; thus, this current study described the prevalence and risk factors of S. stercoralis infection in districts of Sabach Sanjal and Upper Badibou in The Gambia.

Methods

The cross-sectional study enrolled 851 schoolchildren, ages 7 to 14 years old. The participants were enrolled from 17 schools in Sabach Sanjal and Upper Badibou Districts. The WHO random sampling technique n/50 (25 boys and 25 girls) was used. Stool samples were collected from each participant and Kato-Katz smear method was used to screen for S. stercoralis infection.

Results

Out of the total 851 pupils, 76 pupils (8.9%) were positive for S. stercoralis infection. The mean age of infected persons was 10.1 years (±2.2). The prevalence of infection was higher among females (9.2%) than males (8.7%). Rates of infection for age categories 7–10 years and 11–14 years were 12.4% and 4.2%, respectively. Rates of infection by districts were 12.3% for Sabach Sanjal and 7.1% for Upper Badibou. Schoolchildren from Sabach Sanjal were 1.6 times more likely to have strongyloidiasis compared to those from Upper Badibou (aOR = 1.64, p-value = 0.058). Schoolchildren aged 7–10 years were 3.2 times more likely to have strongyloidiasis infection compared to the 11–14-year-olds (aOR = 3.20, p-value <0.001). Schoolchildren who ‘sometimes’ have water or tissue after defaecation have more infection rate compared to those who ‘always’ have water or tissue after defaecation. However, this difference was not statistically significant (aOR = 1.36, p-value = 0.308).

Conclusion

The study revealed the prevalence of strongyloidiasis in Sabach Sanjal and Upper Badibou districts of The Gambia. Kato-Katz technique might be inadequate for detecting S. stercoralis; thus, more studies are needed to determine the true prevalence of the disease in these two districts through the combined use of highly sensitive techniques such as Baermann, Koga Agar Culture and polymerase chain reaction.

Prevalence and associated factors of soil transmitted helminthiasis among school-age children in wetland and non-wetland areas of Blue Nile Basins, northwest Ethiopia: A community-based comparative study

INTRODUCTION

Different interventions have been done to reduce the burden of soil-transmitted helminths (STH). The available evidences in Ethiopia in either school or community-based school-aged children (SAC) have limitation in wetland areas. This study assessed the prevalence and associated factors of STH infection among SAC in wetland and non-wetland areas of Blue Nile Basins, Amhara Region, Northwest Ethiopia.

METHOD

A community-based comparative study was conducted from October to November, 2019. Multistage stratified random sampling technique used to select 716 SAC. Data were collected using structured questionnaire and observational checklist. Stool samples were collected from children using tight-fitting plastic cups following the standard procedures. Data were coded and entered into Epi data version 4.6 and exported to SPSS version 20 software. Bivariate and multivariable logistic regression analysis was employed to identify factors associated with STH.

RESULTS

The overall prevalence of STH was 30.30% (95% CI: 26.90, 33.90) and did not show significant variation between wetland (33.60% (95% CI: 28.80, 39.60%)) and non-wetland (27.0% (95% CI: (21.90, 31.60)) areas. Presence of human feces near the house and certain habits such as nail trimming and playing with mud/soil was not different between wetland and non-wetlands. Nonetheless, the presence of human feces near the house of respondents was found to be significantly associated with STH infection (p value < 0.001). Moreover, other factors significantly associated with STH infection were lack of nail trimming (p value < 0.001) and playing with mud/soil (p value < 0.01).

CONCLUSIONS

The prevalence of STH was high and did not show significant variation between the two areas. Emphasis needs to be given for hygiene and lifestyle-related factors.

Prevalence and Risk Factors Associated with Intestinal Parasitic Infection among Primary School Children in Dera District, Northwest Ethiopia

BACKGROUND

Globally, over 600 million school children are living with intestinal parasites. The prevalence of intestinal parasitic infections (IPIs) among school children in Ethiopia and the Amhara region is 52% and 51%, respectively. The present study aimed to determine the prevalence and associated risk factors of IPIs among primary school children in Dera district, Northwest Ethiopia.

METHODS

A school-based cross-sectional study was conducted from December 2019 to February 2020. The study used a structured pretested questionnaire and stool tests to obtain epidemiological and disease data. Data were analyzed using appropriate univariate and multivariable logistic regression methods by statistical package for social science (SPSS) version 25.0.

RESULTS

Of the 382 students who were examined for IPIs, 238 (62.3%) (61.8% males, 62.8% females) were positive for one or more IPIs. One hundred thirty-six (35.6%), 98 (25.7%), and 4 (1.05%) were single, double, and triple infections, respectively. Out of the nine species of IPIs detected, Entamoeba sp. was the predominant species (29.6%) followed by hookworm (21.7%), Schistosoma mansoni (11.3%), Taenia sp. (9.2%), Giardia lamblia (5.2%), and Ascaris lumbricoides, Hymenolepis nana, and Enterobius vermicularis (4.2%) each, and Trichuris trichiura (0.5%). Family size greater than five (AOR = 1.8; 95% CI: 1.004, 3.13), open field school waste disposal (AOR = 15.88; 95% CI: 1.91, 132.1), and lack of knowledge about intestinal parasitic infection (AOR = 1.8; 95% CI: 1.1, 3.2) were the independent risk factors associated with the overall prevalence of IPIs.

CONCLUSIONS

The prevalence of intestinal parasitic infection was high in the Dera district. Health education, extending school-based deworming, and mass treatments are recommended.

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.

Environmental characteristics around the household and their association with hookworm infection in rural communities from Bahir Dar, Amhara Region, Ethiopia

Soil-Transmitted Helminths (STH) are highly prevalent Neglected Tropical Disease in Ethiopia, an estimated 26 million are infected. Geographic Information Systems and Remote Sensing (RS) technologies assist data mapping and analysis, and the prediction of the spatial distribution of infection in relation to environmental variables. The influence of socioeconomic, environmental and soil characteristics on hookworm infection at the individual and household level is explored in order to identify spatial patterns of infection in rural villages from Zenzelema (Amhara region). Inhabitants greater than 5 years old were recruited in order to assess the presence of STH. Socioeconomic and hookworm infection variables at the household level and environmental variables and soil characteristics using RS were obtained. The dominant STH found was hookworm. Individuals which practiced open defecation and those without electricity had a significant higher number of hookworm eggs in their stool. Additionally, adults showed statistically higher hookworm egg counts than children. Nonetheless, the probability of hookworm infection was not determined by socioeconomic conditions but by environmental characteristics surrounding the households, including a combination of vigorous vegetation and bare soil, high temperatures, and compacted soils (high bulk density) with more acidic pH, given a pH of 6.0 is optimal for hatching of hookworm eggs. The identification of high-risk environmental areas provides a useful tool for planning, targeting and monitoring of control measures, including not only children but also adults when hookworm is concerned.

Soil transmitted helminth infection in primary school children varies with ecozone in the Ngorongoro Conservation Area, Tanzania

BACKGROUND

Soil-transmitted helminthiasis is a neglected tropical disease, thriving in environments of poverty and disadvantage. Our objective was to determine the prevalence and intensity of four soil transmitted helminths (STH) among primary school children in the Ngorongoro Conservation Area (NCA), Tanzania.

METHODS

A cross-sectional study was performed between May 15^th and June 2^nd, 2014. Six of 20 primary schools were chosen, based on elevation, designated low elevation ecozone (LEE) or high elevation ecozone (HEE). A total of 340 children from standards one to four were recruited. Height and weight of each child was determined and body mass index (BMI) was calculated. Stool samples were analyzed using the Kato-Katz, Wisconsin, and Baermann techniques to detect STH eggs and larvae. An interviewer-administered questionnaire on socio-demographic variables was used to capture information from the school's headmaster and a checklist was used to assess sanitation facilities.

RESULTS

STHs identified included Ascaris (presumably lumbricoides), Trichuris (presumably trichiura), hookworms (presumably Ancylostoma duodenale and/or Necator americanus), and Strongyloides (presumably stercoralis). The overall prevalence of STH infection was 29.0% in LEE and 34.0% in HEE. Prevalence was 34.3% and 28.2% in males versus females, respectively. Ascaris sp. were only identified in HEE, prevalence of Trichuris sp. and hookworms were significantly higher in HEE compared to LEE, and Strongyloides spp. prevalence was lower in HEE. Intensity of Trichuris sp. was significantly higher in HEE and lower for hookworms. We did not detect a significant relationship between BMI and helminth intensity; however, BMI was lower in lower elevations and in males vs. females. Sanitation practices are taught at the schools, but challenges were identified when implementing. Latrine facilities were available and latrine-cleaning routines were practiced; however, hand washing practices were challenging due to restricted water availability.

CONCLUSIONS

Significant differences in prevalence in HEE and LEE exist, and STH infections are still very common among school children suggesting that anthelminthic intervention and education may be necessary in this region. Based on this outcome, the study area in the NCA would be classified as a medium risk area, where periodic treatment recommendations should be based on prevalence estimations in the different ecozones.

TRIAL REGISTRATION

Ethics approval was obtained from the Catholic University of Health and Allied Sciences (CUHAS; Lake Zone Institutional Review Board MR/53/100/307)); the Conjoint Health Research Ethics Board (CHREB) at the University of Calgary in Canada (Study ID REB14-0127); the National Institute of Medical Research (NIMR) of Tanzania; and the Tanzania Commission for Science and Technology (COSTEC).

Agar Plate Culture: An Alternative Sensitive Routine Laboratory Detection Method for Strongyloides stercoralis and Hookworm Parasites

Background:

Human infection with Strongyloides stercoralis and hookworm parasites is usually under reported due to less sensitive diagnostic methods. Agar plate culture (APC) is the most sensitive technique for parasites having larval stage. However, using APC in routine diagnosis is uncommon. This study aimed to determine the detection rate and sensitivity of APC in comparison with formal ether concentration technique (FECT) and spontaneous tube sedimentation techniques (STSTs) for S. stercoralis and hookworm larvae.

Methods:

Stool samples collected from 844 schoolchildren in Amhara Regional State, northwestern Ethiopia in 2019, transported to nearby health institutions and processed by APC, FECT and STSTs. The prevalence of S. stercoralis and hookworm was computed by descriptive statistics and Chi-square. The diagnostic agreement among the three techniques was evaluated using Kappa value.

Results:

The overall prevalence of S. stercoralis and hookworm infections by combining the three methods was 13.2% (111/844) and 33.8% (277/844), respectively. Using APC alone, the prevalence of S. stercoralis and hookworm were found to be 10.9% (92/844) and 24.5% (207/844), respectively. Agar plate culture was 5.4 and 2.7 times respectively more sensitive than FECT and STST, with slight and fair agreement in the detection of S. stercoralis. Hookworm diagnostic agreement was moderate between APC and FECT, and APC and STST. The Kappa value between STST and FECT diagnostic methods was substantial.

Conclusion:

APC has a better detection rate of S stercoralis and hookworm larvae. Therefore, APC can be used as an alternative routine diagnostic method to S. stercoralis and hookworm co-endemic countries.

Prevalence of Strongyloidiasis in a Cohort of Migrants in Italy and Accuracy of a Novel ELISA Assay for S. stercoralis Infection, a Cross-Sectional Study

Strongyloides stercoralis infection is a life-threatening neglected tropical disease. Diagnostic issues have caused an underestimation of its global burden. The choice of appropriate diagnostic tests for the screening of populations at risk of the infection, such as migrants from endemic countries, is of paramount importance. From November 2017 to July 2018, all migrants presenting to the National Institute for Health Migration and Poverty (INMP) in Rome, Italy were offered screening tests for S. stercoralis infection. The study objective was to estimate the prevalence of strongyloidiasis in the study population and the accuracy of a novel ELISA assay. The following tests were carried out at the IRCCS Sacro Cuore Don Calabria hospital in Negrar, Verona: stool microscopy, real-time PCR for S. stercoralis, in-house immunofluorescence test (IFAT), a commercial ELISA assay (Bordier ELISA), and a novel ELISA assay (Euroimmun ELISA). A latent class analysis (LCA) model set up with test results, clinical variables, and eosinophilia indicated a prevalence around 7.5%, in line with previous findings. The sensitivity and the specificity of Euroimmun ELISA were 90.6% (95% CI 80.5–100) and 87.7% (95CI 84.5–91.0); these results indicate that the novel ELISA assay would be suitable for screening of migrants from endemic countries.

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.

Soil-transmitted helminths and schistosome infections in Ethiopia: a systematic review of progress in their control over the past 20 years

Background

Ethiopia has set the ambitious national targets of eliminating soil-transmitted helminths (STH) and schistosomiasis (SCH) as public health problems by 2020, and breaking their transmission by 2025. This systematic review was performed to provide insight into the progress made by the national STH and SCH control programme purposed with reaching these targets.

Methods

Studies published on STH and SCH in Ethiopia were searched for using Web of Science, PubMed, Scopus, and the resulting references of selected studies. Prevalence and intensity were analysed, stratified by region, age, and diagnostics.

Results

A total of 231 papers published between 2000 and 2020 were included. Over the past two decades, Trichuris trichiura (TT) infection has shown the most statistically significant decrease (93%, p < 0.0001), followed by Schistosoma mansoni (SM) (69%, p < 0.0001), Ascaris lumbricoides (AL) (67%, p < 0.0001) and Schistosoma haematobium (83%, p = 0.038) infections. Geographically, parasite burden has only consistently shown a significant reduction in the Southern Nations, Nationalities and Peoples’ Region of Ethiopia, where AL, TT, hookworm and SM significantly decreased by 80% (p = 0.006), 95% (p = 0.005), 98% (p = 0.009) and 87% (p = 0.031), respectively. Prevalence of STH was highest among adults across all species, contrary to typical age-infection profiles for TT and AL that peak among school-aged children. Expanding treatment to the whole community would target reservoirs of adult and preschool-aged infection within the community, assisting Ethiopia in reaching their national transmission break targets. There was substantial heterogeneity in diagnostic methods used across studies, the majority of which predominantly used single-slide Kato–Katz. This low slide frequency provides poor diagnostic sensitivity, particularly in low endemic settings.

Conclusion

The prevalence of STH and SCH in Ethiopia has decreased over time due to the strategic use of anthelmintics. Both standardising and increasing the sensitivity of the diagnostics used, alongside the ubiquitous use of parasite intensity with prevalence, would enable a more accurate and comparable understanding of Ethiopia’s epidemiological progress. Further work is needed on community-wide surveillance in order to understand the burden and subsequent need for treatment among those outside of the standard school-based control program.

Prevalence of Schistosoma mansoni infection in Ethiopia: a systematic review and meta-analysis

Background

Schistosomiasis is a common helminthic infection in the tropics and subtropics, particularly in sub-Saharan African countries including Ethiopia. In these counties, Schistosoma mansoni infection is a significant public health problem due to the risk of reinfection and recurrent disease despite implementing several rounds preventive chemotherapy. This systematic review and meta-analysis aimed at assessing the pooled prevalence of schistosomiasis in Ethiopia.

Methods

The PRISMA guidelines were followed to perform the systematic review and meta-analysis. Published studies from January 1999 to June 2020 were searched in Medline, PubMed, Google Scholar, EMBASE, HINARI, and Cochrane Library using key words including: “prevalence”, “incidence”, “schistosomiasis” “Bilharziasis”, “Bilharzia”, “S. mansoni “, “Ethiopia”. Heterogeneity of included studies was assessed using Cochran’s Q test and I² test statistics while publication bias was assessed using Egger’s test.

Results

Ninety-four studies were included in the systematic review and meta-analysis. The pooled prevalence of S. mansoni in Ethiopia was 18.0% (95%CI: 14.0–23.0). The southern region of Ethiopia had a higher S. mansoni prevalence of 25.9% (995% CI, 14.9–41.1) than the national prevalence. The burden of S. mansoni infection was also higher than the national average in rural areas and among men with pooled prevalence of 20.2% (95% CI, 13.2–28.5) and 28.5% (95%CI, 22.7,35.1), respectively. The trend analysis showed that the prevalence of S. mansoni infection in Ethiopia decreased over the past 15 years, potentially because of the repeated preventive chemotherapy.

Conclusion

The review unveiled a moderate prevalence of S. mansoni infection in Ethiopia. Targeted treatment of at-risk population groups ad high burden areas coupled with implementation of integrated vector control strategies are critical to address the burden of Schistosomiasis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40794-020-00127-x.

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.

Assessment of the prevalence of intestinal parasitic infections and associated habit and culture-related risk factors among primary schoolchildren in Debre Berhan town, Northeast Ethiopia

Background

Intestinal parasitic infections (IPIs) are still among the major public health issues in developing countries. Assessing the prevalence of IPIs and potential risk factors in different localities is essential to enhance control strategies. To date, no prevalence assessment study was conducted in Debre Berhan town. Therefore, the aim of this study was to assess the prevalence of IPIs and associated habit and culture-related risk factors among primary schoolchildren in Debre Berhan town, Northeast Ethiopia.

Method

School based cross-sectional study was conducted from April to June 2017. A total of 645 children aged 6–15 years were selected from six primary schools in Debre Berhan town via a multistage random sampling technique. A structured questionnaire was used to collect data about sociodemographic and potential risk factor variables. Fresh stool samples were collected from each child and examined using direct smear and formal-ether concentration technique.

Result

Among the 645 children participated in the study, 341 (52.9%) were infected by one or more intestinal parasites. Helminths (33.8%) were more prevalent than protozoa (20%). Double parasitic infection rate was 0.9%. The predominant parasites were Ascaris lumbricoides (22.6%), Entamoeba histolytica/dispar/moshkovskii (18.1%) and Hymenolepis nana (5.7%). Multivariable logistic regression analysis showed that age of child (6–9 years), family size (above 5), mother’s illiteracy and primary education, father’s illiteracy, urban-farmer father, manual-worker father, not washing hands before eating, unclean fingers, open defecation site (ODS) near residence, latrine type, cultural response to dropped food (cleaning and eating; ‘kiss and replace’), habit of playing with waste water, habit of playing with soil, habit of sucking fingers and habit of eating when playing were significantly associated with IPIs (p< 0.05). Likewise, age (6–9 years), mother’s illiteracy, urban-farmer father, not washing hands before eating, ODS near residence, tradition of cleaning and eating dropped food, habit of playing with soil, sucking fingers and eating when playing were identified as significant risk factors of A. lumbricoides infection.

Conclusion

High prevalence of IPIs among the study participants demands improvement of environmental sanitation, personal hygiene, and health education regarding the potential habit and culture-related risk factors.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-020-10148-y.

How a discerning cytological examination can aid in the diagnosis of infectious diseases: case reports

Infections caused by uncommon and resistant pathogens in unusual sites have been increasingly reported in medical literature. We describe four cases of rare cytological findings and clinical impact for patients. In the first case, Aspergillus sp and Pneumocystis jirovecii were observed in the bronchoalveolar lavage of a patient with severe systemic lupus. In the second and third cases, we describe the presence of Trichomonas sp and Strongyloides sp larvae in samples of pleural and peritoneal fluid, respectively. The fourth report is about a patient with a wrist subcutaneous nodule whose synovial aspiration and cytology revealed the presence of brown septate hyphae. The early identification of the infectious agent in the cytological examination was essential for the introduction and/or re-adaptation of therapy in the four cases described. Patients in this report were immunocompromised with severe comorbidities, conditions often associated with unfavorable clinical outcomes.

Strongyloidiasis in Africa: Systematic Review and Meta-Analysis on Prevalence, Diagnostic Methods, and Study Settings

BACKGROUND

Strongyloidiasis is an intestinal parasitic infection mainly caused by Strongyloides stercoralis. Although it is a predominant parasite in tropics and subtropics where sanitation and hygiene are poorly practiced, the true prevalence of strongyloidiasis is not known due to low-sensitivity diagnostic methods.

OBJECTIVE

This systematic review and meta-analysis is aimed at determining the pooled prevalence of strongyloidiasis in African countries, stratified by diagnostic methods, study settings, and patients.

METHODS

Cross-sectional studies on strongyloidiasis published in African countries from the year 2008 up to 2018 in PubMed and Google Scholar databases and which reported at least one Strongyloides spp. infection were included. Identification and screening of eligible articles were also done. Articles whose focus was on strongyloidiasis in animals, soil, and foreigners infected by Strongyloides spp. in Africa were excluded. The random effects model was used to calculate the pooled prevalence of strongyloidiasis across African countries as well as by diagnostic methods and study settings. The heterogeneity between studies was also computed.

RESULT

A total of 82 studies were included. The overall pooled prevalence of strongyloidiasis was 2.7%. By individual techniques, the pooled prevalence of strongyloidiasis was 0.4%, 1.0%, 3.4%, 9.3%, 9.6%, and 19.4% by the respective direct saline microscopy, Kato-Katz, formol ether concentration, polymerase chain reaction, Baermann concentration, and culture diagnostic techniques. The prevalence rates of strongyloidiasis among rural community, school, and health institution studies were 6.8%, 6.4%, and 0.9%, respectively. The variation on the effect size comparing African countries, diagnostic methods, study settings, and patients was significant (P ≤ 0.001).

CONCLUSIONS

This review shows that strongyloidiasis is overlooked and its prevalence is estimated to be low in Africa due to the use of diagnostic methods with low sensitivity. Therefore, there is a need for using a combination of appropriate diagnostic methods to approach the actual strongyloidiasis rates in Africa.

Molecular evidence of hybridization between pig and human Ascaris indicates an interbred species complex infecting humans

Human ascariasis is a major neglected tropical disease caused by the nematode Ascaris lumbricoides. We report a 296 megabase (Mb) reference-quality genome comprised of 17,902 protein-coding genes derived from a single, representative Ascaris worm. An additional 68 worms were collected from 60 human hosts in Kenyan villages where pig husbandry is rare. Notably, the majority of these worms (63/68) possessed mitochondrial genomes that clustered closer to the pig parasite Ascaris suum than to A. lumbricoides. Comparative phylogenomic analyses identified over 11 million nuclear-encoded SNPs but just two distinct genetic types that had recombined across the genomes analyzed. The nuclear genomes had extensive heterozygosity, and all samples existed as genetic mosaics with either A. suum-like or A. lumbricoides-like inheritance patterns supporting a highly interbred Ascaris species genetic complex. As no barriers appear to exist for anthroponotic transmission of these 'hybrid' worms, a one-health approach to control the spread of human ascariasis will be necessary.

The burden and epidemiology of polyparasitism among rural communities in Kano State, Nigeria

BACKGROUND

Parasitic infections constitute a major public health problem worldwide, particularly among underprivileged communities in developing countries including Nigeria. The present study aimed to determine the epidemiology of polyparasitism (multiple parasitic infections) among rural communities in Kano State, North Central Nigeria.

METHODS

A total of 551 individuals were screened for the presence of intestinal, urogenital and blood parasites by using different diagnostic techniques. Demographic, socioeconomic, household and behavioural characteristics were collected using a pre-tested questionnaire.

RESULTS

Overall, 84.0% (463/551) of the participants were found to be infected with at least one parasite species, with 51.2% (282/551) of them having polyparasitism. The most prevalent parasites were Plasmodium falciparum (60.6%) followed by Blastocystis sp. (29.2%) and hookworm (15.4%). No significant association was found between malaria and helminth infections (p>0.05). Univariate and multivariate analyses showed that the presence of other family members who had intestinal polyparasitism (adjusted odds ratio [AOR]=4.12; 95% CI=2.72, 6.24), walking barefoot outside (AOR=1.70; 95% CI=1.09, 2.63) and being male (AOR=1.74; 95% CI=1.14, 2.66) were the significant risk factors of intestinal polyparasitism among the population studied.

CONCLUSION

Polyparasitism is highly prevalent among rural communities in Kano State. Therefore, effective, sustainable and integrated control measures should be identified and implemented to significantly reduce the burden and consequences of these infections in rural Nigeria.

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

Background

Ivermectin has been proven to be highly effective against Strongyloides stercoralis in some countries. However, its single dose (200 μg/kg) efficacy has not been proven up until now in Ethiopia.

Objective

This study aimed to evaluate the efficacy of single dose ivermectin against S. stercoralis infection among school children.

Methods

Stool sample was collected from April 2019 to December 2019 among 844 school children and screened by formol ether concentration, spontaneous tube sedimentation, Baermann concentration, and agar plate techniques. Single oral dose (200 μg/kg) ivermectin was given to 101 S. stercoralis-infected student and posttreatment diagnosis was done for 92 students after 2 weeks.

Results

Of the total 92 S. stercoralis-infected students who took ivermectin treatment, 87 were negative with cure rate of 94.6%. No side effect of ivermectin was observed.

Conclusion

Single dose ivermectin is an effective dose in uncomplicated chronic strongyloidiasis.

Epidemiology of intestinal helminthiases in a rural community of Ethiopia: Is it time to expand control programs to include Strongyloides stercoralis and the entire community?

BACKGROUND

Soil transmitted helminths are highly prevalent worldwide. Globally, approximately 1.5 billion people are infected with Ascaris lumbricoides, Trichuris trichiura or hookworm. Endemic countries carry out periodic mass treatment of at-risk populations with albendazole or mebendazole as a control measure. Most prevalence studies have focused on school aged children and therefore control programs are implemented at school level, not at community level. In this study, the prevalence of intestinal helminths, including Strongyloides stercoralis, was examined using a comprehensive laboratory approach in a community in north-western Ethiopia.

METHODS

A cross-sectional survey was conducted on 792 individuals ≥5 years old in randomly selected houses in a rural district. Stools were examined using three techniques: a formol-ether concentration, the Baermann technique and a real time polymerase chain reaction test (these last two specific for S. stercoralis). Statistical analyses were performed between two large age groups, children (≤14 years old) and adults (≥15 years old).

RESULTS

The prevalence of helminths was 91.3%; (95% CI: 89.3-93.3%). Hookworm was the most prevalent, 78.7% (95% CI 75.6-81.4%), followed by S. stercoralis 55.7% (95% CI 52.2-59.1%). Co-infection with both was detected in 45.4% (95% CI 42.0-49.0%) of the participants. The mean age of hookworm-infected individuals was significantly higher than non-infected ones (p = 0.003). Also, S. stercoralis infection was significantly associated with age, being more prevalent in adults (p = 0.002).

CONCLUSIONS

This is the highest prevalence of S. stercoralis detected in Ethiopia so far. Our results highlight the need of searching specifically for infection by this parasite since it usually goes unnoticed if helminth studies rely only on conventional diagnostic techniques, i.e. Kato-Katz. Moreover, the focus of these programs on children undermines the actual prevalence of hookworm. The adult population acts as a reservoir for both hookworm and S. stercoralis and this fact may negatively impact the current control programs in Ethiopia which only target treatment of school aged children. This reservoir, together with a lack of adequate water, sanitation and hygiene, increases the probability of re-infection in children. Finally, the high prevalence of S. stercoralis found calls for a comprehensive diagnostic approach in endemic areas in addition to a revision of control measures that is, adding ivermectin to current albendazole/mebendazole, since it is the drug of choice for S. stercoralis.

Prevalence and Associated Factors of Soil-Transmitted Helminth Infections among Children Living with and without Open Defecation Practices in Northwest Ethiopia: A Comparative Cross-Sectional Study

Soil-transmitted helminth (STH) infections cause devastating effect in human health. School-age children (SAC) account for the highest prevalence of STH infections in sub-Sahara. Open defecation practicing might be the major contributing factor, and creating an open defecation-free (ODF) declared community is also a big challenge. This study aimed to assess the prevalence of STH infections and associated factors among SAC in ODF declared and open defecation-practicing kebeles. A comparative cross-sectional study was conducted among 806 SAC from January 2019 to April 2019. Questionnaire-based data were collected using a structured questionnaire. Stool samples were collected and processed via the Kato-Katz technique. Prevalence and associated factors were computed with descriptive statistics and regression, respectively. Variables with a P-value < 0.05 were considered as significantly associated. This study revealed that the prevalence of STH infections in open defecation-practicing and ODF declared kebeles were 39.0% and 30.0%, respectively. Wearing open shoes, wearing shoes sometimes, and playing with soil were significantly associated (P < 0.01) with STH infections in ODF declared kebeles. Similarly, wearing shoes sometimes, not using latrine, and playing with soil were also significantly associated (P < 0.01) with STH infections in open defection-practicing kebeles. In conclusion, lower prevalence of STH infections was recorded in ODF declared than in open defection-practicing kebeles. Wearing shoes sometimes, playing with soil, and not using latrine were associated with STH infections. Therefore, creating an ODF environment and community awareness should be strengthened.

Epidemiology of intestinal parasitic infections in preschool and school-aged Ethiopian children: a systematic review and meta-analysis

BACKGROUND

Numerous studies have been carried out on assessing the prevalence of intestinal parasites infections (IPIs) amongpreschool and school-age children in Ethiopia, but there is lack of study systematically gathered and analyzedinformation for policymakers. Therefore, the aim of this systematic review and meta-analysis was to provide a summary on prevalence, geographical distribution and trends of IPIs among preschool and school-age childrenin Ethiopia.

METHODS

The search were carried out in Medline via PubMed, Scopus, Science Direct, Web of Science, and Google Scholar from 1996to July2019 for studies describing prevalence of IPIs among preschooland school-age children. We conducted meta-regression to understand the trends and the source of heterogeneity and pooled the prevalence using 'metaprop' command using STATA software version 14.

RESULTS

Eighty-three(83) studies examining 56,786 fecal specimens were included. The prevalence of IPIs was 48%(95%CI: 42 to 53%) and showedsignificantly decreasing trends 17% (95% CI: 2.5 to 32%) for each consecutive 6 years) and was similar in males and females. The pooled prevalence in years 1997-2002, 2003-2008, 2009-2014 and > 2014 was 71% (95% CI: 57 to 86%), 42% (95% CI: 27 to 56%), 48% (95% CI: 40 to 56%) and 42% (95% CI: 34 to 49%), respectively. Poly-parasitism was observed in 16% (95% CI: 13 to 19%,) of the cases.

CONCLUSION

Intestinal parasite infections are highly prevalent among preschool and school-age children and well distributed across the regional states of Ethiopia. Southern and Amhara regional states carry the highest burden. We observed significant decreasing trends in prevalence of IPIs among preschool and school-ageEthiopian children over the last two decades. Therefore, this study is important to locate the geographical distribution and identified high risk areas that should be prioritized further interventions, which complement global efforts towards elimination of IPIs infections by 2020.

Prevalence and determinant factors of hookworm infection among school age children in Jawe district, NorthWest Ethiopia

Background

Hookworm infection is a common parasitic infection in sub-Saharan Africa. The prevalence of hookworm infection is influenced by different determinant factors. This study aimed to determine the prevalence of hookworm infection and determinant factors among school age children in North West Ethiopia.

Methods

A cross-sectional study was conducted from April 2016 to August 2016. Children were selected by systematic random sampling and Formoleether concentration technique was used to identify hookworm infection. We conducted descriptive and logistic regression analysis for categorical variables. The adjusted odds ratio was calculated at 95% confidence interval.

Results

Among 333 children, 49 (14.7%) were infected with hookworm parasites. Eating raw vegetables, not wearing shoes, absence of regular wearing of shoes and hand washing habit, absence of proper utilization of latrines, absence of deworming were significantly associated (p<0.05) with hookworm infection.

Conclusion

The prevalence of hookworm infection was high among school age children. Walking with bare foot, hand washing habit, and absence of proper latrine utilization are the major determinant factors for the high prevalence of hookworm infection. Therefore, community mobilization and health education should be done to decrease hookworm infection among school age children in Jawe district.

Prevalence and risk factors of Strongyloides stercoralis infection among Orang Asli schoolchildren: new insights into the epidemiology, transmission and diagnosis of strongyloidiasis in Malaysia

This cross-sectional study aimed to determine the prevalence and risk factors of S. stercoralis infection among 1142 Orang Asli primary schoolchildren in six different states of Peninsular Malaysia. Fecal samples were examined using direct smear, formalin-ether sedimentation (FES), agar plate culture (APC) and PCR techniques. Overall, 15.8% of the children were found to be infected with S. stercoralis. The prevalence was 0.2, 1.3, 15.2 and 13.7% by direct smear, FES, APC and PCR, respectively. Multivariate analysis showed that an age of >10 years, being male, belonging to a Proto-Malay tribe, belonging to the Senoi tribe, indiscriminate defecation, using an unimproved water source for drinking water and not wearing shoes when outside were the significant risk factors of infection among these children. In conclusion, we provide new evidence on the occurrence of S. stercoralis in Malaysia to show that there is a relatively high prevalence of infection among Orang Asli schoolchildren. Therefore, the use of specific methods for detecting S. stercoralis should be considered when screening these children for intestinal parasites. Moreover, prevention and control measures specific to S. stercoralis should be integrated into the intestinal parasitic infections control programme in Malaysia.

Strongyloidiasis in Ethiopia: systematic review on risk factors, diagnosis, prevalence and clinical outcomes

BACKGROUND

Strongyloidiasis is a gastrointestinal infection caused by the parasitic nematode Strongyloides stercoralis. It is estimated to infect up to 370 million people globally and is predominately found in tropical and subtropical areas of socioeconomic disadvantage.

MAIN BODY

This systematic literature review identified studies published in the last ten years on the risk factors, diagnosis, prevalence and/or clinical outcomes of strongyloidiasis in Ethiopia. The prevalence of S. stercoralis ranged from 0.2 to 11.1% in adults, 0.3% to 20.7% in children, 1.5% to 17.3% in HIV positive adults and 5% in HIV positive children. The identified studies primarily used microscopy based techniques that potentially underestimated the prevalence four fold compared with serology and PCR. Strongyloidiasis in children presents a particularly significant issue in Ethiopia as children often presented with anemia, which is associated with impaired mental and cognitive development. The most significant risk factor for strongyloidiasis was HIV status and although other risk factors were identified for helminth infections, none were statistically significant for S. stercoralis specifically. Several studies detected S. stercoralis in dogs and non-biting cyclorrhaphan flies. However, future research is needed to explore the role of these reservoirs in disease transmission.

CONCLUSIONS

This review demonstrated that strongyloidiasis is an overlooked and neglected disease in Ethiopia. There is a need for a systematic approach using a combination of molecular and serology based diagnostic methods to ascertain the true incidence and burden of strongyloidiasis in Ethiopia. Further research is also needed to break the cycle of transmission by identifying environmental reservoirs, risk factors and exploring the potential for zoonotic transfer.

Strongyloides stercoralis in Patients on Corticosteroids Therapy Using Enzyme-Linked Immunosorbent Assay and Gelatin Particles Indirect Agglutination Tests: A Diagnostic Approach

INTRODUCTION

Patients on corticosteroids therapy (POCT) are more likely to flare up concealed Strongyloides infection and develop Strongyloides hyperinfection syndrome and/or dissemination. Such critical complications can lead to high mortality rates. Rapid detection methods are, therefore, necessary to detect Strongyloides infection in POCT with the advantage of being applicable in a developing country.

METHODS

Two hundred POCT have been enrolled in this study to determine the rate of infection with Strongyloides. Three different groups of POCT (Strongyloides infected, non-infected, infected with other parasites) were used to evaluate the antibodies detection capability of two serological techniques (enzyme-linked immunosorbent assay (ELISA) and gelatin particles indirect agglutination (GPIAT) against the results of the gold standard agar plate culture (APC).

RESULTS

With APC, the infection rate of Strongyloides stercoralis in POCT was 9.5% (19/200). POCT with Strongyloides infection displayed related risk factors (job, rural settlements, and soil contact) for infection combined with the subtropical nature of Ismailia Governorate. With regard to serology, ELISA detection results were poor compared to APC with sensitivity and specificity of 42.1% and 82.6%, respectively, and positive and negative predictive values of 72% and 30%. GPIAT appeared to be closely related to APC with sensitivity and specificity of 89.4% and 81.8%, respectively, and positive and negative predictive values of 80.9% and 96.7%. Statistical moderate correlation was detected between GPIAT and ELISA.

CONCLUSION

The GPIAT technique is more convenient, easier, cheaper and faster to rule out the infection of Strongyloides in POCT. It might be the test of choice for routine immunodiagnosis of human strongyloidiasis.

Diagnostic comparison of Baermann funnel, Koga agar plate culture and polymerase chain reaction for detection of human Strongyloides stercoralis infection in Maluku, Indonesia

Human infection with the nematode Strongyloides stercoralis, which may have a life-threatening course, primarily occurs in tropical settings. Epidemiological data on the occurrence of strongyloidiasis are scarce, and microscopic stool-based detection methods are insensitive. Polymerase chain reaction (PCR) assays have been developed, yet conflicting results have been reported. Our goal was to determine whether there was diagnostic agreement between an in-house PCR and two microscopic techniques, the Baermann funnel (BM) and the Koga agar plate culture (KAP) for the detection of S. stercoralis in stool samples. Eighty ethanol-fixed stool samples stemming from a cross-sectional survey in Maluku, Indonesia, were purposefully selected for PCR analysis. The final sample size comprised four groups, each with 20 samples: group 1, positive for S. stercoralis on both BM and KAP; group 2, positive only by BM; group 3, positive only by KAP; and group 4, negative on both BM and KAP. A Strongyloides-specific PCR targeting the internal transcribed spacer 2 (ITS2) region was carried out in an Indonesian reference laboratory. The overall agreement between PCR and microscopy was 61% (49/80 samples), being highest in group 1 (15/20, 75%) and lowest in group 3 (9/20, 45%). PCR revealed eight additional S. stercoralis infections in group 4. Future studies should elucidate the 'true' infection status of samples that are negative by PCR, but positive upon microscopy. Taken together, there is a lack of agreement between microscopy and PCR results for the diagnosis of human S. stercoralis infection in Indonesia. ClinicalTrials.gov (identifier: NCT02105714).

The Unique Life Cycle of Strongyloides stercoralis and Implications for Public Health Action

Strongyloides stercoralis has one of the most complex life cycles of the human-infecting nematodes. A common misconception in medical and public health professions is that S. stercoralis in its biology is akin to other intestinal nematodes, such as the hookworms. Despite original evidence provided by medical and veterinary research about this unique helminth, many assumptions have entered the scientific literature. This helminth is set apart from others that commonly affect humans by (a) the internal autoinfective cycle with autoinfective larvae randomly migrating through tissue, parthenogenesis, and the potential for lifelong infection in the host, the profound pathology occurring in hyperinfection and systemic manifestations of strongyloidiasis, and (b) a limited external cycle with a single generation of free-living adults. This paper aims to review and discuss original research on the unique life cycle of S. stercoralis that distinguishes it from other helminths and highlight areas where increased understanding of the parasite's biology might lead to improved public health prevention and control strategies.

Evaluation of Two DNA Extraction Methods for Detection of Strongyloides stercoralis Infection

Strongyloides stercoralis is present worldwide, but its prevalence is still uncertain, mainly due to the lack of sensitivity of diagnostic methods. Molecular techniques are under development, but a standardized protocol is still unavailable. We compared the sensitivity of real-time PCR, using two extraction protocols, with that of the Baermann technique. Samples were collected in the framework of the baseline screening of a randomized clinical trial evaluating moxidectin against S. stercoralis in Lao People's Democratic Republic. Two stool samples from each participant were processed by the Baermann method, and one subsample was processed by PCR. DNA was extracted using the QIAamp DNA stool minikit based on the standard protocol for the QIAamp DNA minikit (QIA) and using a modification of the QIA procedure (POL). Subsequently, all extracted samples were analyzed by real-time PCR. Overall, 95 samples were analyzed by the three diagnostic methods. Sixty-nine (72.6%) samples were positive according to the Baermann method, 25 (26.3%) by the QIA method, and 62 (65.3%) by the POL method. The sensitivities were 86% (95% confidence interval [CI], 76.7 to 92.9), 31.0% (95% CI, 21.3 to 42.6), and 78.0% (95% CI, 66.8 to 86.1) for the Baermann, QIA, and POL methods, respectively. The sensitivities calculated for each day of the Baermann method separately were 60% (48.4 to 70.8%) and 64% (52.2 to 74.2%) for days 1 and 2, respectively. In conclusion, the POL method revealed a good performance and was comparable to the Baermann test performed on two stool samples and superior to the Baermann method performed on one stool sample. Additional studies are needed to standardize a PCR protocol for S. stercoralis diagnosis.

Accuracy of molecular biology techniques for the diagnosis of Strongyloides stercoralis infection-A systematic review and meta-analysis

Background

Strongyloides stercoralis infection is a neglected tropical disease which can lead to severe symptoms and even death in immunosuppressed people. Unfortunately, its diagnosis is hampered by the lack of a gold standard, as the sensitivity of traditional parasitological tests (including microscopic examination of stool samples and coproculture) is low. Hence, alternative diagnostic methods, such as molecular biology techniques (mostly polymerase chain reaction, PCR) have been implemented. However, there are discrepancies in the reported accuracy of PCR.

Methodology

A systematic review with meta-analysis was conducted in order to evaluate the accuracy of PCR for the diagnosis of S. stercoralis infection. The protocol was registered with PROSPERO International Prospective Register of Systematic Reviews (record: CRD42016054298). Fourteen studies, 12 of which evaluating real-time PCR, were included in the analysis. The specificity of the techniques resulted high (ranging from 93 to 95%, according to the reference test(s) used). When all molecular techniques were compared to parasitological methods, the sensitivity of PCR was assessed at 71.8% (95% CI 52.2–85.5), that decreased to 61.8% (95% CI 42.0–78.4) when serology was added among the reference tests. Similarly, sensitivity of real-time PCR resulted 64.4% (95% CI 46.2–77.7) when compared to parasitological methods only, 56.5% (95% CI 39.2–72.4) including serology.

Conclusions

PCR might not be suitable for screening purpose, whereas it might have a role as a confirmatory test.

Strongyloides stercoralis is a worm that can potentially kill affected immunosuppressed individuals. The parasite is not easily detected with stool microscopy, hence novel tests have been implemented, such as polymerase chain reaction (PCR), that can detect the DNA of the parasite. This work aims at evaluating the performance of PCR for the diagnosis of S. stercoralis through a revision of diagnostic studies available in literature. According to the results of this work, PCR for S. stercoralis still misses a relevant proportion of infected people, while a positive result confirms the presence of the infection.

Prevalence and molecular characterization of Strongyloides stercoralis, Giardia duodenalis, Cryptosporidium spp., and Blastocystis spp. isolates in school children in Cubal, Western Angola

BACKGROUND

Human infections by the gastrointestinal helminth Strongyloides stercoralis and the enteric protozoans Giardia duodenalis, Cryptosporidium spp. and Blastocystis spp. are not formally included in the list of 20 neglected tropical diseases prioritised by the World Health Organization. Although largely underdiagnosed and considered of lower public health relevance, these infections have been increasingly demonstrated to cause significant morbidity and even mortality globally, particularly among children living in resource-poor settings.

METHODS

In this cross-sectional survey the prevalence, frequency and molecular diversity of S. stercoralis, G. duodenalis, Cryptosporidium spp. and Blastocystis spp. were investigated in a school children population in the province of Benguela (Angola). A total of 351 stool samples were collected during January to June 2015. The presence of S. stercoralis and G. duodenalis was confirmed by qPCR methods. Giardia duodenalis assemblages and sub-assemblages were determined by multilocus sequence-based genotyping of the glutamate dehydrogenase and β-giardin genes of the parasite. Detection and identification of Cryptosporidium and Blastocystis species and subtypes was carried out by amplification and sequencing of a partial fragment of the small-subunit ribosomal RNA gene of both protozoan. Analyses of risk factors potentially associated with the transmission of these pathogens were also conducted.

RESULTS

Prevalences of S. stercoralis, G. duodenalis, Cryptosporidium spp., and Blastocystis spp. were estimated at 21.4% (95% CI: 17.1-25.7%), 37.9% (95% CI: 32.8-43.0%), 2.9% (95% CI: 1.1-4.5%) and 25.6% (95% CI: 21.18-30.2%), respectively. Overall, 64.1% (225/351) of the children were infected by at least one of the pathogens investigated. Sequence analyses of the 28 G. duodenalis isolates that were successfully genotyped allowed the identification of sub-assemblages AI (14.3%), AII (14.3%), BIII (7.1%) and BIV (25.0%). Discordant typing results AII/AIII and BIII/BIV were identified in 7.1% and 14.3% of the isolates, respectively. A total of five additional isolates (17.9%) were identified as assemblage B. Three Cryptosporidium species including C. hominis (70%), C. parvum (20%) and C. canis (10%) were found circulating in the children population under study. A total of 75 Blastocystis isolates were assigned to the subtypes ST1 (30.7%), ST2 (30.7%), ST3 (36.0%), ST5 (1.3%) and ST7 (1.3%), respectively. Children younger than seven years of age had significantly higher risk of infections by protozoan enteropathogens (PRR: 1.35, P < 0.01), whereas being underweight seemed to have a protective effect against these infections (PRR: 0.74, P = 0.005).

CONCLUSIONS

The burden of disease attributable to human strongyloidiasis, giardiosis, cryptosporidiosis and blastocystosis in Angola is considerably higher than initially estimated in previous surveys. Surveillance and control of these infections should be jointly tackled with formally considered neglected tropical diseases in order to maximize effort and available resources. Our data also demonstrate the added value of using molecular diagnostic methods in high transmission areas.