Prevalence and genotypic characterization of Giardia duodenalis isolates from asymptomatic school-going children in Lusaka, Zambia

Assemblages and Subassemblages of Giardia duodenalis in Rural Western, Kenya: Association with Sources, Signs, and Symptoms

Background

Giardia duodenalis causes sporadic or epidemic infections in humans. The parasite comprises assemblages A-H with A and B subdivided further into AI-IV and BI-IV subassemblages. Attempts aimed at linking these genotypes with sources and gastrointestinal manifestations of the infection are largely unexplored in rural communities.

Methods

In this cross-sectional study, G. duodenalis infection was genotyped and associated with sources, and gastrointestinal signs and symptoms of the disease among residents of Busia County, a rural setting in western Kenya. Demographic and clinical information were captured using standardized forms. Stool specimens were obtained from the patients and used for genotyping at glutamate dehydrogenase and triose-phosphate isomerase loci using the polymerase chain reaction and restriction fragment length polymorphism.

Results

Assemblage B (63.6%) was the most prevalent G. duodenalis infection, while A (20.5%) and mixed A/B (15.9%) were also detected. Among the subassemblages, AI (5.7%), AII (8.0%), AIII (3.4), BIII (30.7%), and BIV (17.0%) were diagnosed including the mixed AII/BIII (15.9%), BIII/BIV (15.9%), AI/AIII (2.3%), and AI/AII (1.1%) infections. Binary logistic regression indicated associations for assemblage A with stomach upset, history of nitroimidazole treatment, and residing in a homestead with cattle and B with age < 18 years, history of eating outdoors, vomiting, steatorrhea, and residing in a homestead with cattle, goats, and poultry (p < 0.05 for all). Among the subassemblages, associations were found for AI with residing in a homestead having cattle and history of nitroimidazole treatment, BIII with residing in a homestead having cattle and poultry, and BIV with steatorrhea (p < 0.05 for all). Altogether, this study illustrates that G. duodenalis assemblage B and subassemblage BIII are the most predominant and are linked to age < 18 years, gastrointestinal manifestations, and living in a homestead with domestic ruminants and poultry.

Conclusion

Targeted mass prophylactic treatment of domestic animals and utilization of gastrointestinal presentations, age < 18 years, and a history of nitroimidazole use are useful in the diagnosis and prevention of giardiasis among residents of rural communities.

Genotyping and epidemiological distribution of diarrhea-causing isolates of Giardia duodenalis in southeastern part of West Bengal, India

The prevalence and genetic diversity of the protozoan pathogen Giardia duodenalis have been extensively studied worldwide. There is currently a lack of data regarding the genetic variability of the organism in eastern India. Understanding the circulating genotypes and associated risk factors is crucial for effective planning and implementing control measures. Therefore, the objective of the study was to conduct an epidemiological study to determine the prevalence and identify the various genotypes present. This survey adds to our knowledge on the occurrence and distribution of Giardia genotypes in the studied region. The overall prevalence was found to be 6.8%. This parasitic infection was significantly associated with two age groups, i.e., >0-5 years and >5-12 years. Using a multilocus genotyping method, we genotyped 52 human Giardia isolates that were obtained from diarrheal patients. Two distinct assemblages were found in the population-30.8% belonged to assemblage A; 63.5% belonged to assemblage B, prevalent in the population; and 5.7% belonged to a combined assemblage A+B. Sub-assemblage AII was found in 17.3% of the cases, followed by sub-assemblage AI (13.5%). High levels of genetic diversity were found within the population of assemblage B undergoing balancing selection. Overall, the high prevalence of the parasite observed, particularly among children, raises a major concern and necessitates implementation of robust control measures. Furthermore, we report the presence of numerous unique genotypes, circulating in this limited geographical boundary, which can be useful dataset for future studies.

Prevalence and molecular characterization of Giardia intestinalis isolated from children and calves in Babylon province, Iraq

Background and Aim

Giardia intestinalis is one of the most prevalent intestinal parasites in humans and animals, and children in close contact with livestock are particularly at risk of infection. This study aimed to detect assemblages of G. intestinalis and determine the origin of zoonotic transmission of Giardia in children and calves in different parts of Babylon province, Iraq.

Materials and Methods

One hundred stool samples from children (68 boys and 32 girls) and 100 fecal samples from calves (46 males and 54 females) of different ages were randomly collected. Molecular techniques were used to estimate the prevalence of G. intestinalis in children and calves. A nested polymerase chain reaction (PCR) was performed by targeting the triose phosphate isomerase gene in the samples to detect G. intestinalis assemblages.

Results

The overall rates of infection with G. intestinalis in children and calves were 21% and 34%, respectively, using the conventional microscopic method. The results illustrated that 61.90% (13/21) and 38.09% (8/21) of positive samples from children were allocated to assemblages A and B, respectively (p > 0.05). In calves, assemblages A and B were detecte in 82.35% (28/34) and 17.64% (6/34) of positive samples from calves, respectively (p ≤ 0.001). Ten PCR products were sequenced and submitted to the GenBank database. Phylogenetic analysis detected five human sequences each belonging to G. intestinalis assemblages A (OM850335-OM850339) and B (OM850340-OM850344). Similarly, five calf sequences each belonged to G. intestinalis assemblages A (ON75756-ON757660) and B (ON757661-ON757665).

Conclusion

The detection of large numbers of G. intestinalis assemblage A in both humans and cattle indicated that cattle could be a main source of zoonotic G. intestinalis infection in children in Babylon province, Iraq.

High Diversity of Giardia duodenalis Assemblages and Sub-Assemblages in Asymptomatic School Children in Ibadan, Nigeria

Giardia duodenalis is a significant contributor to the burden of diarrheal disease in sub-Saharan Africa. This study assesses the occurrence and molecular diversity of G. duodenalis and other intestinal parasites in apparently healthy children (n = 311) in Ibadan, Nigeria. Microscopy was used as a screening method and PCR and Sanger sequencing as confirmatory and genotyping methods, respectively. Haplotype analyses were performed to examine associations between genetic variants and epidemiological variables. At microscopy examination, G. duodenalis was the most prevalent parasite found (29.3%, 91/311; 95% CI: 24.3–34.7), followed by Entamoeba spp. (18.7%, 58/311; 14.5–23.4), Ascaris lumbricoides (1.3%, 4/311; 0.4–3.3), and Taenia sp. (0.3%, 1/311; 0.01–1.8). qPCR confirmed the presence of G. duodenalis in 76.9% (70/91) of the microscopy-positive samples. Of them, 65.9% (60/91) were successfully genotyped. Assemblage B (68.3%, 41/60) was more prevalent than assemblage A (28.3%, 17/60). Mixed A + B infections were identified in two samples (3.3%, 2/60). These facts, together with the absence of animal-adapted assemblages, suggest that human transmission of giardiasis was primarily anthroponotic. Efforts to control G. duodenalis (and other fecal-orally transmitted pathogens) should focus on providing safe drinking water and improving sanitation and personal hygiene practices.

The controversies surrounding Giardia intestinalis assemblages A and B

Giardia intestinalis continues to be one of the most encountered parasitic diseases around the world. Although more frequently detected in developing countries, Giardia infections nonetheless pose significant public health problems in developed countries as well. Molecular characterisation of Giardia isolates from humans and animals reveals that there are two genetically different assemblages (known as assemblage A and B) that cause human infections. However, the current molecular assays used to genotype G. intestinalis isolates are quite controversial. This is in part due to a complex phenomenon where assemblages are incorrectly typed and underreported depending on which targeted locus is sequenced. In this review, we outline current knowledge based on molecular epidemiological studies and raise questions as to the reliability of current genotyping assays and a lack of a globally accepted method. Additionally, we discuss the clinical symptoms caused by G. intestinalis infection and how these symptoms vary depending on the assemblage infecting an individual. We also introduce the host-parasite factors that play a role in the subsequent clinical presentation of an infected person, and explore which assemblages are most seen globally.

Prevalence of intestinal protozoan parasites among school children in africa: A systematic review and meta-analysis

Introduction

Parasitic infections, especially intestinal protozoan parasites (IPPs) remain a significant public health issue in Africa, where many conditions favour the transmission and children are the primary victims. This systematic review and meta-analysis was carried out with the objective of assessing the prevalence of IPPs among school children in Africa.

Methods

Relevant studies published between January 2000 and December 2020 were identified by systematic online search on PubMed, Web of Science, Embase and Scopus databases without language restriction. Pooled prevalence was estimated using a random-effects model. Heterogeneity of studies were assessed using Cochrane Q test and I² test, while publication bias was evaluated using Egger’s test.

Results

Of the 1,645 articles identified through our searches, 46 cross-sectional studies matched our inclusion criteria, reported data from 29,968 school children of Africa. The pooled prevalence of intestinal protozoan parasites amongst African school children was 25.8% (95% CI: 21.2%-30.3%) with E. histolytica/ dispar (13.3%; 95% CI: 10.9%-15.9%) and Giardia spp. (12%; 95% CI: 9.8%-14.3%) were the most predominant pathogenic parasites amongst the study participants. While E. coli was the most common non-pathogenic protozoa (17.1%; 95% CI: 10.9%-23.2%).

Conclusions

This study revealed a relatively high prevalence of IPPs in school children, especially in northern and western Africa. Thus, poverty reduction, improvement of sanitation and hygiene and attention to preventive control measures will be the key to reducing protozoan parasite transmission.

Pathogenic intestinal protozoan parasites (IPPs) remain a major public health concern. Studies have documented that, the prevalence rates of protozoan infections are quite high in developing regions, particularly Africa and children are the primary victims. Despite numerous studies have been conducted on IPPs in school children in African countries, data on the burden of these infections in African school children have not yet been synthesised. This systematic review and meta-analysis was conducted to provide continent-wide prevalence of IPPs amongst African school children. Our study found that about 25.8% of the children had one or more species of intestinal protozoan parasites in their faecal specimens. E. histolytica/ dispar and Giardia spp. were the most predominant parasites amongst the study participants. The relatively high prevalence estimate of IPPs amongst African children and the considerable variation in the disease prevalence over the years, between and within countries and regions clearly indicates the needs to improve sanitation and hygiene, paying more attention to preventive control measures as well as poverty reduction which are the key to reducing protozoan parasite transmission.

GIARDIA DUODENALIS GENOTYPING NOT LINKED TO CLINICAL SYMPTOMATOLOGY AND NUTRITIONAL STATUS OF SCHOOL-AGED CHILDREN OF SOLEDAD AND GALAPA MUNICIPALITY SCHOOLS, ATLÁNTICO, COLOMBIA

Giardia duodenalis genotypes A and B have been reported in Colombia. The population consisted of 235 schoolchildren whose ages ranged from 2 to 10 yr of age from the municipalities of Soledad and Galapa in the department of Atlántico, Colombia. Fecal samples were obtained and then analyzed in triplicate using the sedimentation in formalin-ether (Ritchie's method) and direct examination techniques. Of the 235 fecal samples, 35 samples were positive for G. duodenalis; positive samples were concentrated in a sucrose gradient and sonicated for 3 cycles of 20 sec. DNA extraction was performed, and the parasites were genotyped by conventional PCR amplifying a region of the β-giardin gene. A general prevalence of G. duodenalis of 13.2% was found, and of these genotyped samples, 13 (56.7%) and 7 (20%) corresponded to genotype A, 1 (4.3%), and 3 (25%) corresponded to genotype B, and 9 (39.1%) and 2 (16.7%) were not defined, in the municipalities Soledad and Galapa, respectively. Additionally, 23 children were diagnosed with symptomatologic giardiasis, and 12 were asymptomatic; the most relevant symptoms were abdominal pain (7, 20%) and diarrhea (13, 56.7%). The nutritional status of children with Giardia genotypes A and B were as follows: 3 in a state of malnutrition (10%), 10 normal (33.3%), and 6 overweight and obese (20%) with genotype A, and 1 in a state of malnutrition (3.3%) and 3 normal (10%) with genotype B. The genotypes found in G. duodenalis did not show an association with nutritional status or with the clinical manifestations evaluated in schoolchildren.

Neighborhood-Based Socioeconomic Determinants of Cognitive Impairment in Zambian Children With HIV: A Quantitative Geographic Information Systems Approach

BACKGROUND

Place-based inequalities, such as exposure to violence and access to nutritious food and clean water, may contribute to human immunodeficiency virus (HIV)-associated cognitive impairment. In this study, we investigated neighborhood effects on cognition in children and adolescents with HIV in Lusaka, Zambia.

METHODS

We conducted a prospective cohort study of 208 children with perinatally acquired HIV (ages 8-17) and 208 HIV-exposed uninfected controls. Participants underwent neuropsychological testing and interviews assessing socioeconomic status. Geographic regions with clusters of participants with HIV and cognitive impairment were identified using quantitative geographic information systems (QGIS) and SaTScan. Associations between location of residence and cognitive function were evaluated in bivariable and multivariable regression models. Mediation analysis was performed to assess direct and indirect effects of location of the residence on cognitive impairment.

RESULTS

Residence in Chawama, one of the poorest neighborhoods in Lusaka, was significantly associated with cognitive impairment in participants with HIV (odds ratio 2.9; P = .005) and remained significant in a multivariable regression model controlling for potential confounders. Mediation analysis found that 46% of the cognitive effects of residence in Chawama were explained by higher rates of malnutrition, lower school attendance, and poorer self-reported health.

CONCLUSIONS

Place-based socioeconomic inequality contributes to cognitive impairment in Zambian children and adolescents with HIV. Neighborhood effects may be mediated by concentrated poverty, malnutrition, limited access to education and health care, and other yet unknown environmental factors that may be potentially modifiable.

The risk factors for intestinal Giardia spp infection: Global systematic review and meta-analysis and meta-regression

Parasitic infections are a public health concern as they can cause aggression, growth retardation, weight loss, anemia, and other health problems. In this study, a systematic review and meta-analysis were performed to find an association between the probable social-environmental risk factors including lack of safe drinking water, no hand washing, sex, age, no access to education, no access to toilet, and Giardia spp infection. We conducted literature research among international databases including Scopus, PubMed, Web of Science and Cochrane from1 January 1995 to March 15, 2020, including 23 articles with 102 studies while the odds ratio (OR) was calculated using 2 × 2 tables or extracted. The pooled effect size with 95% confidence intervals (CIs) was estimated using a random or fixed-effects model. The results show a significant association between intestinal Giardia spp infection risk and lack of safe drinking water (OR: 1.14; 95%CI: 1.02-1.25); no access to toilet (OR: 1.22; 95%CI: 1.07-1.37); and age (2-10 vs 10-30 year) (OR: 1.42; 95%CI: 1.09-1.78). An insignificant association was observed between intestinal Giardia spp infection risk and age (<2 vs 2-10 year) (OR: 0.89; 95%CI: 0.75-1.02); no access to education (OR: 1.10; 95%CI: 0.80-1.40); Sex (male vs female) (OR: 1.04; 95%CI: 0.74-1.34); and no handwashing (OR: 1.18; 95%CI: 0.87-1.49). The results of meta-regression also indicate that intestinal Giardia spp infection has decreased over time (C= -0.024, p-value = 0.03) significantly, and also by growth of human development index (HDI) (C= - 0.42, p-value = 0.29) insignificantly. Improvement of personal hygiene, sanitation and raising public awareness can be effective in reducing Giardia spp infections.

Molecular diversity of Giardia duodenalis in children under 5 years from the Manhiça district, Southern Mozambique enrolled in a matched case-control study on the aetiology of diarrhoea

Giardia duodenalis is an enteric parasite commonly detected in children. Exposure to this organism may lead to asymptomatic or symptomatic infection. Additionally, early-life infections by this protozoan have been associated with impaired growth and cognitive function in poor resource settings. The Global Enteric Multicenter Study (GEMS) in Mozambique demonstrated that G. duodenalis was more frequent among controls than in diarrhoeal cases (≥3 loosing stools in the previous 24 hours). However, no molecular investigation was conducted to ascertain the molecular variability of the parasite. Therefore, we describe here the frequency and genetic diversity of G. duodenalis infections in children younger than five years of age with and without diarrhoea from the Manhiça district in southern Mozambique enrolled in the context of GEMS. Genomic DNA from 757 G. duodenalis-positive stool samples by immunoassay collected between 2007-2012, were reanalysed by multiplex PCR targeting the E1-HP and C1-P21 genes for the differentiation of assemblages A and B. Overall, 47% (353) of the samples were successfully amplified in at least one locus. Assemblage B accounted for 90% (319/353) of all positives, followed by assemblage A (8%, 29/353) and mixed A+B infections (1%, 5/353). No association between the presence of a given assemblage and the occurrence of diarrhoea could be demonstrated. A total of 351 samples were further analysed by a multi-locus sequence genotyping (MLSG) approach at the glutamate dehydrogenase (gdh), ß-giardin (bg) and triose phosphate isomerase (tpi) genes. Overall, 63% (222/351) of samples were genotyped and/or sub-genotyped in at least one of the three markers. Sequence analysis revealed the presence of assemblages A (10%; 23/222) and B (90%; 199/222) with high molecular diversity at the nucleotide level within the latter; no mixed infections were identified under the MLSG scheme. Assemblage A sequences were assigned to sub-assemblages AI (0.5%, 1/222), AII (7%, 15/222) or ambiguous AII/AIII (3%, 7/222). Within assemblage B, sequences were assigned to sub-assemblages BIII (13%, 28/222), BIV (14%, 31/222) and ambiguous BIII/BIV (59%, 132/222). BIII/BIV sequences accumulated the majority of the single nucleotide polymorphisms detected, particularly in the form of double peaks at chromatogram inspection. This study demonstrated that the occurrence of gastrointestinal illness (diarrhoea) was not associated to a given genotype of G. duodenalis in Mozambican children younger than five years of age. The assemblage B of the parasite was responsible for nine out of ten infections detected in this paediatric population. The extremely high genetic diversity observed within assemblage B isolates was compatible with an hyperendemic epidemiological scenario where infections and reinfections were common. The obtained molecular data may be indicative of high coinfection rates by different G. duodenalis assemblages/sub-assemblages and/or genetic recombination events, although the exact contribution of both mechanisms to the genetic diversity of the parasite remains unknown.

Food and waterborne parasites in Africa - threats and opportunities

This Special Issue (SI) was conceptualized on the basis that success in tackling foodborne and waterborne parasites (FBP and WBP) will contribute to achievement of seven of the United Nation's Sustainable Development Goals (SDGs). We chose to take a closer look at research on FBP and WBP in Africa, given that attaining these SDGs may be particularly challenging there. In this SI we present 7 articles that provide particular insights into FBP and WBP from different regions in Africa. The articles take different approaches. Three papers are reviews addressing "occurrence" (either widely, in terms of parasite and/or geography, or with focus on a specific parasite genus at a more regional level); all 3 articles emphasise the importance of a "One Health" approach regarding control and prevention of FBP and WBP, and the need for further research to fulfil the information gaps identified. Two articles then report on investigations regarding the knowledge and understanding of different communities in Africa regarding various FBP and WBP. These articles highlight lack of awareness among communities at risk, and also, perhaps of greater relevance, gaps in the knowledge of health workers regarding some FBP and WBP of public health importance. The final two articles are research articles regarding prevalence and occurrence of specific WBP, both as infections and in the environment. This SI, while limited in depth and scope, provides insights into some of the current challenges associated with FBP and WBP in Africa that might result in a lack of success regarding attainment of the previously mentioned seven SDGs. We anticipate significant advances in research on FBP and WBP in Africa, and hope that a future SI on the same topic may present a more positive picture regarding the current status and research achievements.