Multiple-subgenotype infections of Giardia intestinalis detected in Palestinian clinical cases using a subcloning approach

Genetic diversity and molecular diagnosis of Giardia

Giardia is a genus of flagellated protozoan parasites that infect the small intestine of humans and animals, causing the diarrheal illness known as giardiasis. Giardia exhibits significant genetic diversity among its isolates, which can have important implications for disease transmission and clinical presentation. This diversity is influenced by the coevolution of Giardia with its host, resulting in the development of unique genetic assemblages with distinct phenotypic characteristics. Although panmixia has not been observed, some assemblages appear to have a broader host range and exhibit higher transmission rates. Molecular diagnostic methods enable researchers to examine the genetic diversity of Giardia populations, enhancing our understanding of the genetic diversity, population structure, and transmission patterns of this pathogen and providing insights into clinical presentations of giardiasis.

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.

Suitability of current typing procedures to identify epidemiologically linked human Giardia duodenalis isolates

Background

Giardia duodenalis is a leading cause of gastroenteritis worldwide. Humans are mainly infected by two different subtypes, i.e., assemblage A and B. Genotyping is hampered by allelic sequence heterozygosity (ASH) mainly in assemblage B, and by occurrence of mixed infections. Here we assessed the suitability of current genotyping protocols of G. duodenalis for epidemiological applications such as molecular tracing of transmission chains.

Methodology/Principal findings

Two G. duodenalis isolate collections, from an outpatient tropical medicine clinic and from several primary care laboratories, were characterized by assemblage-specific qPCR (TIF, CATH gene loci) and a common multi locus sequence typing (MLST; TPI, BG, GDH gene loci). Assemblage A isolates were further typed at additional loci (HCMP22547, CID1, RHP26, HCMP6372, DIS3, NEK15411).

Of 175/202 (86.6%) patients the G. duodenalis assemblage could be identified: Assemblages A 25/175 (14.3%), B 115/175 (65.7%) and A+B mixed 35/175 (20.0%). By incorporating allelic sequence heterozygosity in the analysis, the three marker MLST correctly identified 6/9 (66,7%) and 4/5 (80.0%) consecutive samples from chronic assemblage B infections in the two collections, respectively, and identified a cluster of five independent patients carrying assemblage B parasites of identical MLST type. Extended MLST for assemblage A altogether identified 5/6 (83,3%) consecutive samples from chronic assemblage A infections and 15 novel genotypes. Based on the observed A+B mixed infections it is estimated that only 75% and 50% of assemblage A or B only cases represent single strain infections, respectively. We demonstrate that typing results are consistent with this prediction.

Conclusions/Significance

Typing of assemblage A and B isolates with resolution for epidemiological applications is possible but requires separate genotyping protocols. The high frequency of multiple infections and their impact on typing results are findings with immediate consequences for result interpretation in this field.

Giardia duodenalis is a leading cause of gastroenteritis worldwide. Humans are mainly infected by the two different genetic subtypes, assemblage A and B. Molecular typing tools for epidemiological applications such as tracking transmission, attribution to a source and outbreak investigations have been developed and are highly desirable. However, to what degree the tetraploid genome with allelic sequence heterogeneity (ASH), and the frequent occurrence of mixed, assemblage A and B infections hamper performance is unclear. Here, we assessed the suitability of current genotyping protocols for deciphering the molecular epidemiology of G. duodenalis. Against a common reporting bias, we incorporated ASH in the analysis and we show that typing with resolution for epidemiological applications is possible for both, assemblage A and B isolates, but requires separate protocols. We also demonstrate how the high frequency of multiple infections overall impacts on typing results, which has immediate consequences for result interpretation in this field.

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.

Genetic Diversity of the Flavohemoprotein Gene of Giardia lamblia: Evidence for High Allelic Heterozygosity and Copy Number Variation

Purpose

The flavohemoprotein (gFlHb) in Giardia plays an important role in managing nitrosative and oxidative stress, and potentially also in virulence and nitroimidazole drug tolerance. The aim of this study was to analyze the genetic diversity of gFlHb in Giardia assemblages A and B clinical isolates.

Methods

gFlHb genes from 20 cultured clinical Giardia isolates were subjected to PCR amplification and cloning, followed by Sanger sequencing. Sequences of all cloned PCR fragments from each isolate were analyzed for single nucleotide variants (SNVs) and compared to genomic Illumina sequence data. Identical clone sequences were sorted into alleles, and diversity was further analyzed. The number of gFlHb gene copies was assessed by mining PacBio de novo assembled genomes in eight isolates. Homology models for assessment of SNV's potential impact on protein function were created using Phyre2.

Results

A variable copy number of the gFlHb gene, between two and six copies, depending on isolate, was found. A total of 37 distinct sequences, representing different alleles of the gFlHb gene, were identified in AII isolates, and 41 were identified in B isolates. In some isolates, up to 12 different alleles were found. The total allelic diversity was high for both assemblages (>0.9) and was coupled with a nucleotide diversity of <0.01. The genetic variation (SNVs per CDS length) was 4.8% in sub-assemblage AII and 5.4% in assemblage B. The number of non-synonymous (ns) SNVs was high in gFIHb of both assemblages, 1.6% in A and 3.0% in B, respectively. Some of the identified nsSNV are predicted to alter protein structure and possibly function.

Conclusion

In this study, we present evidence that gFlHb, a putative protective enzyme against oxidative and nitrosative stress in Giardia, is a variable copy number gene with high allelic diversity. The genetic variability of gFlHb may contribute metabolic adaptability against metronidazole toxicity.

Extremely diversified haplotypes observed among assemblage B population of Giardia intestinalis in Kenya

In molecular epidemiological studies of Giardia intestinalis, an pathogenic intestinal flagellate, due to the presence of allelic sequence heterogeneity (ASH) on the tetraploid genome, the image of haplotype diversity in the field remains uncertain. Here we employed the nine assemblage B positive stool samples, which had previously reported from Kenyan children, for the clonal sequence analysis of multiple gene loci (glutamate dehydrogenase (GDH), triosephosphate isomerase (TPI), and beta-giardin (BG)). The diversified unique assemblage B haplotypes as GDH (n = 67), TPI (n = 84), and BG (n = 62), and the assemblage A haplotypes as GDH (n = 7), TPI (n = 14), and BG (n = 15), which were hidden in the previous direct-sequence results, were detected. Among the assemblage B haplotypes, Bayesian phylogeny revealed multiple statistically significant clusters (9, 7, and 7 clusters for GDH, TPI, and BG, respectively). A part of the clusters (2 for GDH and 1 for BG), which included >4 haplotypes from an individual sample, indicated the presence of co-transmission with multiple strains sharing a recent ancestor. Locus-dependent discrepancies, such as different compositions of derived samples in clusters and different genotyping results for the assemblages, were also observed and considered to be the traces of both intra- and inter-assemblage genetic recombination respectively. Our clonal sequence analysis for giardial population, which applied firstly in Kenya, could reveal the higher rates of ASH far beyond the levels reported in other areas and address the complex population structure. The clonal analysis is indispensable for the molecular field study of G. intestinalis.

Improvement in cyst recovery and molecular detection of Giardia duodenalis from stool samples

Molecular detection of Giardia duodenalis by polymerase chain reaction (PCR) is difficult in faecal samples due to inhibitors that contaminate DNA preparations, or due to low cyst concentrations. In order to eliminate inhibitors, improve cyst recovery and molecular detection of G. duodenalis, different types of water, distillates (MDs), deionized (MDz), injection (MI) or Milli-Q^® (MM) were used instead of formaldehyde (F) in the laboratory routine method (Ritchie). Cysts were isolated from faecal samples with low cyst concentrations (< 1 cyst/field), medium (1-2 cysts/field) or high (> 2 cysts/field). Cyst recovery was improved using all water types (MDs, MDz, MI, MM) compared to formaldehyde. At all cyst concentrations, the use of MM consistently showed the greatest recovery of G. duodenalis cysts . DNA samples from recovered cysts were tested for the glutamate dehydrogenase (GDH) and β-giardin (βg) genes. The use of Milli-Q^® water allowed to detect both genes in all cyst concentrations, including low. The method processed with the other types of water amplified these genes at high and medium cyst concentrations. GDH and βg genes were not detected when the sample was processed with formaldehyde. These experimental results were confirmed in clinical samples. The results suggest that Milli-Q^® water provides the highest cyst recovery from stool samples and, correspondingly, the highest sensitivity for detecting G. duodenalis by microscopy or PCR for GDH and βg genes, even at low concentration of cysts.

Epidemiological distribution of genotypes of Giardia duodenalis in humans in Spain

BACKGROUND

Although the distribution of Giardia duodenalis genotypes in humans has been increasingly reported in recent years, data on possible differences in pathogen transmission between age groups and virulence between genotypes are scarce. The purpose of this study is to investigate the genetic diversity of G. duodenalis in humans in Spain and compare the distribution of G. duodenalis assemblages A and B between children and adults and clinical presentations between the two genotypes.

METHODS

In the present study, 125 microscopy-positive fecal samples were collected from humans in Spain over a 7-year period. PCR and sequence analyses of the triosephosphate isomerase, β-giardin and glutamate dehydrogenase genes were used to identify the multilocus genotypes of G. duodenalis.

RESULTS

Sequence analysis of three genetic loci identified both G. duodenalis assemblages A (29) and B (66), with co-infections of the two in two patients. Among the sequences obtained in this study, four multilocus genotypes (MLGs) of the sub-assemblage AII were observed within assemblage A. In contrast, 19 MLGs were detected within assemblage B due to the high sequence diversity at each locus. One MLG, however, was found in 51.9% (27/52) of assemblage B samples. Children were more commonly infected by assemblage B (44/53 or 83%) than adults (22/42 or 52.4%; χ2 = 10.371, df = 1, P = 0.001). Asymptomatic infection was more common in patients with assemblage A (4/29 or 13.8%) than in those with assemblage B (1/66 or 1.5%; χ2 = 6.091, df = 1, P = 0.029), and the frequency of abdominal pain occurrence was higher in assemblage B patients (65/66 or 98.5%) than assemblage A patients (25/29 or 86.2%; χ2 = 6.091, df = 1, P = 0.029).

CONCLUSIONS

These results illustrate the existence of differences in genotype distribution between children and adults and clinical presentations between G. duodenalis genotypes. They are useful in understanding the transmission of G. duodenalis in humans in Spain.

A modified PCR-RFLP method to determine genetic diversity of Giardia lamblia human isolates based on triosephosphate isomerase (TPI) gene

An infection of digestive system, Giardiasis, caused by tiny parasites called Giardia lamblia (also known Giardia intestinalis or Giardia duodenalis). Giardia sp. is the most common intestinal parasite of humans and other animals throughout the world. Isolates of G. lamblia are classified into eight assemblages based on isoenzyme and DNA analyses. Assemblages A and B infect humans and a broad range of other hosts. The purpose of this study was to genotype human isolates of G. lamblia by PCR-RFLP in Karaj city. 60 positive fecal samples of G. lamblia were collected. DNA extraction and amplification of TPI gene were successfully conducted by nested-PCR. Subsequently, all samples were positive. Sequencing on 5 samples was conducted to determine genetic differences. The presence of 2 genotypes of G. lamblia (A and B) was revealed by the alignment of the TPI sequences obtained with reference sequences. The results of RFLP technique show that 35 of 60 (58.3%) isolates belonged to assemblage A, and 17 of 60 (28.3%) belonged to assemblage B but 1(1.7%) sample was not determined. Whereas, 7 (11.6%) specimens were detected as mixed infections. The latter RFLP was carried out to identify subtypes.The final results were 100% (35/35) AII, 82.3% (14/17) BIII, and 17.7% (3/17) BIV. This study suggests that the modified RFLP method is favorably time saving and easily achievable and highly economical. Hence, the sub-assemblage AII might be dominant in Karaj city.

Distribution of Giardia duodenalis (Assemblages A and B) and Cryptosporidium parvum amongst migrant workers in Peninsular Malaysia

The influx of low skilled workers from socioeconomically deprived neighbouring countries to Malaysia has raised concerns about the transmission of communicable gastrointestinal diseases such as giardiasis and cryptosporidiosis to the local population. Therefore, a cross sectional study was conducted to investigate the prevalence of both diseases and the genetic diversity of these pathogens in the migrant population. Microscopic examination of faecal samples from 388 migrant workers involved in five working sectors were screened and 10.8% (n = 42) were found to be positive with Giardia spp. and 3.1% (n = 12) with Cryptosporidium spp. infections. PCR amplicons at the triosephosphate isomerase (tpi) gene were successfully obtained for Giardia duodenalis from 30 (30/388; 7.73%) samples with assemblages AII and B in 13 (13/30; 43.3%) and 17 (17/30; 56.7%) positive samples, respectively. Nine samples (9/388; 2.3%) were identified as Cryptosporidium parvum using PCR-RFLP analysis. Country of origin, duration of residence in Malaysia and working sectors significantly influenced G. duodenalis assemblage AII infections amongst the targeted population. Meanwhile, C. parvum infection was significantly associated with those working in the food service sector. Despite the low presence of pathogenic G. duodenalis and C. parvum in the study population, the results highlight the risk of anthroponotic foodborne and waterborne transmission and therefore call for implementation of control strategies through improvements in personal hygiene and sanitation standards.

Genetic variability and transcontinental sharing of Giardia duodenalis infrapopulations determined by glutamate dehydrogenase gene

Microevolutionary data of Giardia duodenalis sub-assemblages is a prerequisite for determining the invasion zoonotic patterns of the parasite. To infer transmission patterns that could not be differentiated by the phenotypic features, a population genetic investigation is crucial for the elucidation of the genetic structure of G. duodenalis among the continents. Forty G. duodenalis positive fecal samples were collected from different foci of Northwest Iran. The specimens were subjected to Trichrome staining and sucrose gradient flotation. DNA samples were extracted, amplified, and sequenced by targeting glutamate dehydrogenase (gdh) gene. The global gdh sequences of sub-assemblages AII and BIV retrieved from NCBI GenBank were analyzed to estimate diversity indices, neutrality indices, and gene migration tests. Sequencing analyses indicated various levels of genetic variability of sub-assemblages AII and BIV among the five continents. Sub-assemblage BIV had greater genetic variability (haplotype diversity: 0.975; nucleotide diversity: 0.04246) than sub-assemblage AII. The statistical Fst value demonstrated that the genetic structure of sub-assemblages AII and BIV are moderately differentiated between European-American populations (Fst: 0.05352-0.15182), whereas a significant differentiation was not seen among other geographical population pairs. We conclude that a high gene flow of G. duodenalis sub-assemblages AII and BIV is unequivocally sharing among the continents. The current findings strengthen our knowledge to assess the evolutionary patterns of G. duodenalis in endemic foci of the world and it will become the basis of public health policy to control human giardiasis.

Strong genetic structure revealed by multilocus patterns of variation in Giardia duodenalis isolates of patients from Galicia (NW-Iberian Peninsula)

We report a survey of genetic variation at three coding loci in Giardia duodenalis of assemblages A and B obtained from stool samples of patients from Santiago de Compostela (Galicia, NW-Iberian Peninsula). The mean pooled synonymous diversity for assemblage A was nearly five times lower than for assemblage B (0.77%±0.30% and 4.14%±1.65%, respectively). Synonymous variation in both assemblages was in mutation-drift equilibrium and an excess of low-frequency nonsynonymous variants suggested the action of purifying selection at the three loci. Differences between isolates contributed to 40% and 60% of total genetic variance in assemblages A and B, respectively, which revealed a significant genetic structure. These results, together with the lack of evidence for recombination, support that (i) Giardia assemblages A and B are in demographic equilibrium and behave as two genetically isolated populations, (ii) infections are initiated by a reduced number of individuals, which may be genetically diverse and even belong to different assemblages, and (iii) parasites reproduce clonally within the host. However, the observation of invariant loci in some isolates means that mechanisms for the homogenization of the genetic content of the two diploid nuclei in each individual must exist.

Prevalence of Giardia duodenalis assemblages and sub-assemblages in symptomatic patients from Damascus city and its suburbs

Giardia duodenalis is one of the most important human enteric parasites worldwide and is endemic throughout the world with a vast range of mammalian hosts. However, there is limited information on the prevalent genetic variability of G. duodenalis in Syria. This study aimed to evaluate the predominance of G. duodenalis assemblages/sub-assemblages causing humans infection in the city of Damascus and its suburbs. 40 symptomatic giardiasis patients were recruited in this study. Fecal samples were genotyped using PCR/RFLP assay targeting the β-giardin and glutamate dehydrogenase (gdh) genes. HaeIII, BspL1 and RsaI restriction enzymes were used to differentiate between G. duodenalis assemblages/sub-assemblages. Our data showed that 65% of isolates were of assemblage A; 45% belonged to sub-assemblage AII and 20% to sub-assemblage AI. Assemblage B was detected in 27.5% of isolates; 12.5% fit in sub-assemblage BIV, 5% fit in sub-assemblage BIII and 10.5% fit in Discordant genotype BIII/BIV. Mixed genotypes (AII+BIII and AI+BIV) were identified in 3 isolates (7.5%). Significant correlation was found between Giardia AII sub-assemblage and weight loss symptom (P-value=0.05) as well as between contact with domestic animals (cats, P-value=0.027). Moreover, a significant correlation was found between sub-assemblage AI and livestock breeding (P-value=0.000). In conclusion genotyping of human Giardia duodenalis isolates suggests anthroponotic transmission for the route of infection in Damascus and its suburbs. Further studies are needed to screen a wide geographic areas in Syria and to estimate the prevalence of G. duodenalis infection in our population.

Positive correlation of HIV infection with Giardia intestinalis assemblage B but not with assemblage A in asymptomatic Kenyan children

A cross-sectional molecular epidemiological study of Giardia intestinalis infection was conducted among asymptomatic Kenyan children with (n = 123) and without (n = 111) HIV infection. G. intestinalis assemblage B infection was positively correlated with HIV infection [HIV (+), 18.7% vs. HIV (-), 11.7%; P = 0.013], whereas assemblage A infection was not [HIV (+), 4.1% vs. HIV (-), 6.3%; P = 0.510]. Thus, HIV infection is a risk factor for G. intestinalis assemblage B infection but not for assemblage A infection.

Prevalence and Genetic Diversity of Giardia duodenalis and Cryptosporidium spp. among School Children in a Rural Area of the Amhara Region, North-West Ethiopia

Backgroud

Giardia duodenalis and Cryptosporidium spp. are enteric protozoan causing gastrointestinal illness in humans and animals. Giardiasis and cryptosporidiosis are not formally considered as neglected tropical diseases, but belong to the group of poverty-related infectious diseases that impair the development and socio-economic potential of infected individuals in developing countries.

Methods

We report here the prevalence and genetic diversity of G. duodenalis and Cryptosporidium spp. in children attending rural primary schools in the Bahir Dar district of the Amhara Region, Ethiopia. Stool samples were collected from 393 children and analysed by molecular methods. G. duodenalis was detected by real-time PCR, and the 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 species was carried out by sequencing of a partial fragment of the small-subunit ribosomal RNA gene.

Principal Findings

The PCR-based prevalences of G. duodenalis and Cryptosporidium spp. were 55.0% (216/393) and 4.6% (18/393), respectively. A total of 78 G. duodenalis isolates were successfully characterized, revealing the presence of sub-assemblages AII (10.3%), BIII (28.2%), and BIV (32.0%). Discordant typing results AII/AIII and BIII/BIV were identified in 7.7% and 15.4% of the isolates, respectively. An additional five (6.4%) isolates were assigned to assemblage B. No mixed infections of assemblages A+B were found. Extensive genetic variation at the nucleotide level was observed within assemblage B (but no within assemblage A), resulting in the identification of a large number of sub-types. Cryptosporidium diversity was demonstrated by the occurrence of C. hominis, C. parvum, and C. viatorum in the population under study.

Conclusions

Our data suggest an epidemiological scenario with an elevated transmission intensity of a wide range of G. duodenalis genetic variants. Importantly, the elevated degree of genetic diversity observed within assemblage B is consistent with the occurrence of intra-assemblage recombination in G. duodenalis.

Multilocus genotyping of Giardia duodenalis isolates from children in Oromia Special Zone, central Ethiopia

BACKGROUND

Giardia duodenalis is the etiologic agent of giardiasis in humans and other mammals worldwide. The burden of disease is high among children in developing countries where sanitation is inadequate. However, the epidemiology and genetic diversity of this parasite is poorly understood in Ethiopia. This study aimed to determine the prevalence and genetic diversity of G. duodenalis in asymptomatic children in Oromia Special Zone, central Ethiopia.

RESULTS

A total of 286 fresh fecal specimens were collected from children and screened using microscopy and PCR. The prevalence of Giardia duodenalis was 10.8 % (31/286) and 16.8 % (48/286) as detected by microscopy and nested PCR, respectively. The infection rate by the study area, sex and age group difference was not significant (P > 0.05). Genotyping results showed that 22.9 % (11/48) of the isolates belonged to assemblage A while 77.1 % (37/48) belonged to assemblage B. Although double peaks were observed at the chromatogram level, no mixed assemblage or sub-assemblage infections were demonstrated. Isolates of assemblage A mostly belonged to the sub-assemblage AII and showed similarity with previously described isolates. However, there was great genetic variability within assemblage B that showed heterogeneous nucleotide positions. Fifteen of them were new genotypes: 5 at the triose phosphate isomerase (tpi), 2 at the β-giardin (bg), and 8 at the glutamate dehydrogenase (gdh) genes.

CONCLUSIONS

Giardia duodenalis mainly assemblage B infection was predominant among the asymptomatic children in the study area. The high polymorphism found in isolates of assemblage B warrants a more defining tool to discriminate assemblage B at the sub-assemblage level. The findings of the present study indicate that there is a need to carry out national screening programs aiming to detect asymptomatic infections to minimize the reservoir of the disease.

First genetic characterisation of Giardia in human isolates from Jordan

Little is known about the epidemiology of Giardia in Jordan and to date, no genotyping studies have been conducted on Giardia isolates from Jordanians. In the present study, a total of 49 microscopy-positive faecal samples from Jordanian patients suffering from giardiasis were analysed at two loci: the triose phosphate isomerase (tpi) gene and the glutamate dehydrogenase (gdh) gene. At the tpi locus, a total of 28 samples amplified and assemblage A was identified in 46.4 % (13/28) samples, while assemblage B was identified in 50 % (14/28) samples and a mixed assemblage A and B was identified in one sample (3.6 %) (Table 1). At the gdh locus 48 isolates amplified and of these assemblages A was identified in 43.7 % (21/48) of isolates and assemblage B in 56.3 % (27/48) of isolates. No mixed infections were detected at the gdh locus. Subtyping at the gdh locus identified sub-assemblage AII in 43.7 % (21/48) of isolates and sub-assemblages BIII and BIV in 25 % (12/48) and 31.2 % (15/48) of isolates, respectively, with more genetic diversity in AII isolates than BIII or BIV isolates. Novel sub-types within each sub-assemblage were identified suggesting unique endemicity and anthroponotic transmission of Giardia in Jordanian patients suffering from giardiasis. Further studies are required to better understand the epidemiology and transmission of Giardia in Jordan.

Molecular Characterization of Giardia duodenalis in Children in Kenya

BACKGROUND

Giardia duodenalis is an important intestinal protozoan in humans worldwide with high infection rates occurring in densely populated and low resource settings. The parasite has been recorded to cause diarrhea in children. This study was carried out to identify G. duodenalis assemblages and sub-assemblages in children presenting with diarrhea in Kenya.

METHODS

A total of 2112 faecal samples were collected from children aged ≤ 5 years and screened for the presence of Giardia cysts using microscopy. A total of 96 (4.5%) samples were identified as Giardia positive samples and were genotyped using glutamate dehydrogenase (gdh), triose phosphate isomerase (tpi) and β-giardin loci.

RESULTS

The three markers successfully genotyped 72 isolates and grouped 2 (1.4) isolates as Assemblage A, 64 (88.9) as Assemblage B and 7 (9.7%) consisted of mixed infections with assemblage A and B. A further analysis of 50 isolates using GDH Polymerase Chain Reaction and Restriction Fragment Length Polymorphism (PCR-RFLP) categorized 2 assemblage A isolates as sub-assemblage AII while 6 and 14 assemblage B isolates were categorized into sub-assemblage BIII and BIV respectively. A mixed infection with sub-assemblage BIII and BIV was recorded in 28 isolates. Over half (55.6%) of Giardia infections were recorded among the children between 13 to 48 months old.

CONCLUSION

This paper reports the first data on the assemblages and sub-assemblages of Giardia duodenalis in children representing with diarrhea in Kenya.

Molecular detection of giardiasis among children at Cairo University Pediatrics Hospitals

Giardiasis is a prevailing intestinal disease in children. This study aimed to determine molecular prevalence of Giardia intestinalis in children attending Cairo University Pediatrics Hospitals, using copro-PCR assays, conventional methods and to evaluate diagnostic effectiveness of used tests. 229 fecal samples were collected from children suffering from gastrointestinal symptoms and examined for Giardia by microscopy, Immuno-chromatographic test (ICT), copro-DNA using two PCR assays targeting tpi [nested-PCR (nPCR)] and 18S [conventional-PCR (cPCR)] genes. Out of 229 samples assessed, Giardia was diagnosed in 13.9, 17, 17.9, 4.8 % of cases using microscopy, ICT, nPCR (tpi) and cPCR (18S), respectively. Nominating both PCR assays as composite reference standard, microscopy and ICT were of reliable specificity (100 and 96.9 %) and accuracy (95.6 and 93.6 %) but of limited sensitivity (78.6 and 76.2 %). Kappa agreement showed, there was substantial agreement of ICT (0.776) and almost perfect agreement of microscopy (0.839) with PCR assays. Giardia showed a molecular prevalence of 18.3 % (42/229). ICT assay for Giardia surpassed microscopy but both couldn't be used as a consistent single detection method due to their lowered sensitivities. nPCR targeting tpi is a reliable diagnostic test aiding to determine true prevalence of Giardia.

Detection and molecular characterisation of Giardia duodenalis, Cryptosporidium spp. and Entamoeba spp. among patients with gastrointestinal symptoms in Gambo Hospital, Oromia Region, southern Ethiopia

OBJECTIVES

To assess the prevalence and genetic diversity of the enteric protozoa species G. duodenalis, Cryptosporidium spp. and Entamoeba histolytica in individuals with gastrointestinal symptoms compatible with infections by these pathogens seeking medical attention in a rural area in southern Ethiopia.

METHODS

A total of 92 stool samples were initially screened by direct microscopy and immunochromatography and further confirmed by molecular methods. G. duodenalis-positive samples were molecularly characterised by multilocus genotyping of the glutamate dehydrogenase and β-giardin genes of the parasite. PCR and DNA sequence analysis of the gene encoding the 60-kDa glycoprotein was used for the subtyping of Cryptosporidium isolates. Detection and differential diagnosis of E. histolytica/dispar were conducted by real-time PCR.

RESULTS

PCR-based prevalences were 10.9% for G. duodenalis, 1.1% for Cryptosporidium spp. and 3.3% for Entamoeba spp. Seven (four novel and three known) subtypes of G. duodenalis assemblage B were identified at the GDH locus and 5 (one novel and four known) at the BG locus. A novel variant of C. hominis subtype IbA9G3 was also identified. Two Entamoeba isolates were assigned to E. dispar and an additional one to E. histolytica.

CONCLUSION

Although preliminary, our results strongly suggest that giardiasis, cryptosporidiosis and amoebiasis represent a significant burden in Ethiopian rural population.

Genotyping of Giardia duodenalis isolates from dogs in Guangdong, China based on multi-locus sequence

This study aimed to identify the assemblages (or subassemblages) of Giardia duodenalis by using normal or nested PCR based on 4 genetic loci: glutamate dehydrogenase (gdh), triose phosphate isomerase (tpi), β-giardin (bg), and small subunit ribosomal DNA (18S rRNA) genes. For this work, a total of 216 dogs' fecal samples were collected in Guangdong, China. The phylogenetic trees were constructed with MEGA5.2 by using the neighbor-joining method. Results showed that 9.7% (21/216) samples were found to be positive; moreover, 10 samples were single infection (7 isolates assemblage A, 2 isolates assemblage C, and 1 isolate assemblage D) and 11 samples were mixed infections where assemblage A was predominant, which was potentially zoonotic. These findings showed that most of the dogs in Guangdong were infected or mixed-infected with assemblage A, and multi-locus sequence typing could be the best selection for the genotype analysis of dog-derived Giardia isolates.

Molecular epidemiology of giardiasis among Orang Asli in Malaysia: application of the triosephosphate isomerase gene

BACKGROUND

Giardia duodenalis is a flagellate parasite which has been considered the most common protozoa infecting human worldwide. Molecular characterization of G. duodenalis isolates have revealed the existence of eight groups (Assemblage A to H) which differ in their host distribution. Assemblages A and B are found in humans and in many other mammals.

METHODS

This cross-sectional study was conducted to identify assemblage's related risk factors of G. duodenalis among Orang Asli in Malaysia. Stool samples were collected from 611 individuals aged between 2 and 74 years old of whom 266 were males and 345 were females. Socioeconomic data were collected through a pre-tested questionnaire. All stool samples were processed with formalin-ether sedimentation and Wheatley's trichrome staining techniques for the primary identification of G. duodenalis. Molecular identification was carried out by the amplification of a triosephosphate isomerase gene using nested-PCR assay.

RESULTS

Sixty-two samples (10.2%) were identified as assemblage A and 36 (5.9%) were assemblage B. Risk analysis based on the detected assemblages using univariate and logistic regression analyses identified subjects who have close contact with household pets i.e. dogs and cats (OR = 2.60; 95% CI = 1.42, 4.78; P = 0.002) was found to be significant predictor for assemblage A. On the other hand, there were three significant risk factors caused by assemblage B: (i) children ≤15 years old (OR = 2.33; 95% CI = 1.11, 4.87; P = 0.025), (ii) consuming raw vegetables (OR = 2.82; 95% CI = 1.27, 6.26; P = 0.011) and (iii) the presence of other family members infected with giardiasis (OR = 6.31; 95% CI = 2.99, 13.31; P < 0.001).

CONCLUSIONS

The present study highlighted that G. duodenalis infection among Orang Asli was caused by both assemblages with significant high prevalence of assemblage A. Therefore, taking precaution after having contact with household pets and their stool, screening and treating infected individuals, awareness on the importance of good health practices and washing vegetables are the practical intervention ways in preventing giardiasis in Orang Asli community.

Giardia--from genome to proteome

In this review, the current status of genomic and proteomic research on Giardia is examined in terms of evolutionary biology, phylogenetic relationships and taxonomy. The review also describes how characterising genetic variation in Giardia from numerous hosts and endemic areas has provided a better understanding of life cycle patterns, transmission and the epidemiology of Giardia infections in humans, domestic animals and wildlife. Some progress has been made in relating genomic information to the phenotype of Giardia, and as a consequence, new information has been obtained on aspects of developmental biology and the host-parasite relationship. However, deficiencies remain in our understanding of pathogenesis and host specificity, highlighting the limitations of currently available genomic datasets.

Giardiasis: a review on assemblage distribution and epidemiology in India

Giardiasis is a significant cause of diarrheal disease and associated morbidity in children and adults worldwide. In addition to diarrhea, it can also lead to malnutrition and cognitive deficits in children from developing countries. Giardia duodenalis is considered to be a species complex of several assemblages, of which assemblage A and B are predominantly associated with human infections. Assemblage type has been associated with risk of occurrence of symptoms and duration of illness. Hence genotyping of giardial isolates may help understand better the epidemiology and transmission ecology of the disease in a particular setting or area. In India, prevalence rates of Giardia infection in patients with diarrhea range from 0.4% to 70%, and asymptomatic cyst passage has been found to be as high as 50% in rural southern India. In this review, the global distribution of giardial assemblage, zoonotic transmission and the association of assemblage with disease have been discussed, followed by epidemiology of giardiasis in India.

High prevalences of infection with Giardia intestinalis genotype B among children in urban and rural areas of Argentina

The protozoan parasite most frequently associated with diarrhoea worldwide is Giardia intestinalis. In 2005, a study was initiated to identify the genotypes of this parasite infecting children in the Argentinian provinces of Buenos Aires, Mendoza and Chaco, and to explore the associations between the genotype detected in a child, the characteristics of the child's household and the child's clinical presentation. Overall, 998 children (504 boys and 494 girls) aged between 2-14 years, with or without symptoms, were enrolled. The G. intestinalis in 94 of the 117 stool samples found positive for the parasite by microscopy were successfully genotyped by PCR. Seventy-seven of the children were found to be infected with genotype B only and 14 with genotype AII only, three children being found to have mixed (AII and B) infections. Only genotype B was detected in children from rural areas (P<0·05) and most Giardia detected in children from households with a piped water supply were also of this genotype (P<0·05). The other household characteristics investigated (quality of building, history of flooding, type of sanitation, level of overcrowding, and presence/absence of pet dogs) had no significant effect on the genotype distribution. Children infected with genotype AII were significantly younger than those infected with genotype B (P<0·05) and there was a significant positive association between infection with genotype B and abdominal pain (P<0·05). Diarrhoea was not, however, found to be significantly associated with genotype-AII or genotype-B infection. This is the first published report on the Giardia genotypes circulating in the provinces of Mendoza and Chaco. The results indicate the importance of asymptomatic children in the transmission of Giardia among the young.

Multilocus genotyping of human Giardia isolates suggests limited zoonotic transmission and association between assemblage B and flatulence in children

BACKGROUND

Giardia intestinalis is one of the most common diarrhea-related parasites in humans, where infection ranges from asymptomatic to acute or chronic disease. G. intestinalis consists of eight genetically distinct genotypes or assemblages, designated A-H, and assemblages A and B can infect humans. Giardiasis has been classified as a possible zoonotic disease but the role of animals in human disease transmission still needs to be proven. We tried to link different assemblages and sub-assemblages of G. intestinalis isolates from Swedish human patients to clinical symptoms and zoonotic transmission.

METHODOLOGY/PRINCIPAL FINDINGS

Multilocus sequence-based genotyping of 207 human Giardia isolates using three gene loci: ß-giardin, glutamate dehydrogenase (gdh), and triose phosphate isomerase (tpi) was combined with assemblage-specific tpi PCRs. This analysis identified 73 patients infected with assemblage A, 128 with assemblage B, and six with mixed assemblages A+B. Multilocus genotypes (MLGs) were easily determined for the assemblage A isolates, and most patients with this genotype had apparently been infected through anthroponotic transmission. However, we also found evidence of limited zoonotic transmission of Giardia in Sweden, since a few domestic human infections involved the same assemblage A MLGs previously reported in Swedish cats and ruminants. Assemblage B was detected more frequently than assemblage A and it was also more common in patients with suspected treatment failure. However, a large genetic variability made determination of assemblage B MLGs problematic. Correlation between symptoms and assemblages was found only for flatulence, which was significantly more common in children less than six years of age infected with assemblage B.

CONCLUSIONS/SIGNIFICANCE

This study shows that certain assemblage A subtypes are potentially zoonotic and that flatulence is connected to assemblage B infections in young children. Determination of MLGs from assemblages A and B can be a valuable tool in outbreak situations and to help identify possible zoonotic transmission.

Zoonotic enteric protozoa

A growing number of enteric protozoan species are considered to have zoonotic potential. Their clinical impact varies and in many cases is poorly defined. Similarly, the epidemiology of infections, particularly the role of non-human hosts, requires further study. In this review, new information on the life cycles and transmission of Giardia, Cryptosporidium, Entamoeba, Blastocystis and Balantidium are examined in the context of zoonotic potential, as well as polyparasitism and clinical significance.

Zoonotic potential and molecular epidemiology of Giardia species and giardiasis

Molecular diagnostic tools have been used recently in assessing the taxonomy, zoonotic potential, and transmission of Giardia species and giardiasis in humans and animals. The results of these studies have firmly established giardiasis as a zoonotic disease, although host adaptation at the genotype and subtype levels has reduced the likelihood of zoonotic transmission. These studies have also identified variations in the distribution of Giardia duodenalis genotypes among geographic areas and between domestic and wild ruminants and differences in clinical manifestations and outbreak potentials of assemblages A and B. Nevertheless, our efforts in characterizing the molecular epidemiology of giardiasis and the roles of various animals in the transmission of human giardiasis are compromised by the lack of case-control and longitudinal cohort studies and the sampling and testing of humans and animals living in the same community, the frequent occurrence of infections with mixed genotypes and subtypes, and the apparent heterozygosity at some genetic loci for some G. duodenalis genotypes. With the increased usage of multilocus genotyping tools, the development of next-generation subtyping tools, the integration of molecular analysis in epidemiological studies, and an improved understanding of the population genetics of G. duodenalis in humans and animals, we should soon have a better appreciation of the molecular epidemiology of giardiasis, the disease burden of zoonotic transmission, the taxonomy status and virulences of various G. duodenalis genotypes, and the ecology of environmental contamination.

Molecular analysis of household transmission of Giardia lamblia in a region of high endemicity in Peru

BACKGROUND

Giardia lamblia is ubiquitous in multiple communities of nonindustrialized nations. Genotypes A1, A2, and B (Nash groups 1, 2, and 3, respectively) are found in humans, whereas genotypes C and D are typically found in dogs. However, genotypes A and B have occasionally been identified in dogs.

METHODS

Fecal Giardia isolates from 22 families and their dogs, living in Pampas de San Juan, were collected over 7 weeks in 2002 and 6 weeks in 2003. Samples were genotyped, followed by sequencing and haplotyping of many of these isolates by using loci on chromosomes 3 and 5.

RESULTS

Human infections were all caused by isolates of genotypes A2 and B. Human coinfections with genotypes A2 and B were common, and the reassortment pattern of different subtypes of A2 isolates supports prior observations that suggested recombination among genotype A2 isolates. All dogs had genotypes C and/or D, with one exception of a dog with a mixed B/D genotype infection.

CONCLUSIONS

In a region of high endemicity where infected dogs and humans constantly commingle, different genotypes of Giardia are almost always found in dogs and humans, suggesting that zoonotic transmission is very uncommon.

Genetic characterizations of Cryptosporidium spp. and Giardia duodenalis in humans in Henan, China

Cryptosporidium and Giardia infections are common causes of diarrhea worldwide. To better understand the transmission of human cryptosporidiosis and giardiasis in Henan, China, 10 Cryptosporidium-positive specimens and 18 Giardia-positive specimens were characterized at the species/genotype and subtype levels. Cryptosporidium specimens were analyzed by DNA sequencing of the small subunit rRNA and 60kDa glycoprotein genes. Among those genotyped, nine belonged to C. hominis and one C. felis, with the former belonging to three subtype families: Ia, Ib, and Id. The three Ib subtypes identified, IbA16G2, IbA19G2, and IbA20G2, were very different from the two common Ib subtypes (IbA9G3 and IbA10G2) found in other areas of the world. The distribution of Giardia duodenalis genotypes and subtypes was assessed by sequence analysis of the triosephosphate isomerase (tpi) gene. The assemblages A (eight belonging to A-I and four A-II) and B (belonging to six new subtypes) were found in 12 and six specimens, respectively. More systematic studies are needed to understand the transmission of Cryptosporidium and G. duodenalis in humans in China.