Sensitive PCR-restriction fragment length polymorphism assay for detection and genotyping of Giardia duodenalis in human feces

Identification of a novel assemblage G subgenotype and a zoonotic assemblage B in rodent isolates ofGiardia duodenalisin the Canary Islands, Spain

The flagellated parasiteGiardia duodenalisis known as one of the most common causes of protozoal diarrhoea in both humans and animals worldwide. The aim of the present work was to perform the first study ofG. duodenalisin rodents in the Canary Islands (Spain) and analyse the level of genetic variation and the potential zoonotic role of the isolates. Stool samples were collected from 284 wild rodents andGiardiacysts were detected by light microscopy. The overall prevalence of giardiasis was 25·4% and ranged from 19·4% in El Hierro to 34% in Gran Canaria. Positive samples were further characterized by PCR and nucleotide sequencing of the triose phosphate isomerase (TPI),β-giardin (BG) and glutamate dehydrogenase (GDH) genes. Our study revealed assemblage G as the most frequent genotype and identified two rodent-infectingG. duodenalishaplotypes of this assemblage, HI and HII. Phylogenetic analysis supported the monophyly of haplotype HI, which we suggest to be considered as a novelG. duodenalissub-assemblage GII, due to the high genetic distances among this sub-genotype and assemblage G. Furthermore,G. duodenalisassemblage B was detected in an inhabited area in La Palma, a fact that may pose a potential risk ofG. duodenalistransmission from rodents to humans.

Molecular identification of Giardia duodenalis in Ecuador by polymerase chain reaction-restriction fragment length polymorphism

The aim of this study was to determine the genetic diversity of Giardia duodenalis present in a human population living in a northern Ecuadorian rain forest. All Giardia positive samples (based on an ELISA assay) were analysed using a semi-nested polymerase chain reaction-restriction fragment length polymorphism assay that targets the glutamate dehydrogenase (gdh) gene; those amplified were subsequently genotyped using NlaIV and RsaI enzymes. The gdh gene was successfully amplified in 74 of 154 ELISA positive samples; 69 of the 74 samples were subsequently genotyped. Of these 69 samples, 42 (61%) were classified as assemblage B (26 as BIII and 16 as BIV), 22 (32%) as assemblage A (3 as AI and 19 as AII) and five (7%) as mixed AII and BIII types. In this study site we observe similar diversity in genotypes to other regions in Latin America, though in contrast to some previous studies, we found similar levels of diarrheal symptoms in those individuals infected with assemblage B compared with those infected with assemblage A.

Investigation of Possible Correlation between Giardia duodenalis Genotypes and Clinical Symptoms in Southwest of Iran

BACKGROUND

Giardia duodenalis is one of the most important human enteric parasites throughout the world. Clinical symptoms of this parasite vary from asymptomatic infection to chronic diarrhea. Still it is not clear, whether different types of pathogenesis are due to different strains of organism or to variable host factors. The purpose of this study was to investigate possible correlation of clinical symptoms with assemblages among symptomatic and asymptomatic cases collected from southwest of Iran.

METHODS

Fecal samples were collected from 100 symptomatic and asymptomatic cases, which were positive for G. duodenalis. The samples were subjected to semi-nested PCR and RFLP for gdh gene.

RESULTS

Among symptomatic patients, 54% had mixed genotypes AII and BIII, 28% and 18% of samples indicated assemblages BIII and AII, respectively. In contrast, among asymptomatic cases, 64%, 26% and 10%samples had mixed genotypes, BIII and AII assemblages, respectively. Statistical analysis using Chi- Square test showed that there was no significant correlation between assemblage and clinical symptoms in current study.

CONCLUSION

High prevalence of mixed infection in both groups may affect this conclusion, therefore further study in more details are necessary to clarify these finding. Additionally, it is important to carry out investigations regarding human host factors as well.

Evaluation of an immunochromatographic dip strip test for simultaneous detection of Cryptosporidium spp, Giardia duodenalis, and Entamoeba histolytica antigens in human faecal samples

Immunochromatographic (IC) tests may play an important role in the future diagnosis of parasitic diseases because of their speed and simplicity of use. A recently developed test to detect Cryptosporidium spp, Giardia duodenalis and Entamoeba histolytica was evaluated. Microscopy and PCR were the "gold standard" reference techniques and the results of this IC test were compared with those obtained with ELISA and IC single test for the three parasites. One hundred sixty stool samples were assayed. Using microscopy, 22 samples were diagnosed as positive for Cryptosporidium spp., 31 for Giardia duodenalis, 41 for Entamoeba histolytica/dispar, and 68 had a negative diagnosis for the three parasites. Results of IC tests show sensitivities of 70-72% for Cryptosporidium, 90-97% for Giardia and 62.5% for Entamoeba histolytica. Specificities were of 93.6-94.9%, >99% and 96.1%, respectively. In all diagnoses, agreement with microscopy and PCR was over 90%, except in the triple test and microscopy in E. histolytica detection that was 76.3%, due to the inability of microscopy to differentiate E. histolytica from nonpathogenic species such as E. dispar or E. moshkovskii. The triple stool immunoassays provide adequate sensitivities and specificities for use in outbreak situations, for screening proposals and for massive assays in endemic areas where a large number of samples must be analysed or as complementary test for individual diagnosis.

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.

Identification and molecular characterization of Cryptosporidium and Giardia in children and cattle populations from the province of Álava, North of Spain

The prevalence of and factors associated with the protozoan enteropathogens Cryptosporidium and Giardia have been investigated in selected children and cattle populations from the province of Álava (Northern Spain). The presence of these organisms was detected in fecal samples using commercially available coproantigen-ELISA (CpAg-ELISA) and immunochromatographic (ICT) assays. A total of 327 caregivers of children participants were asked to answer questions on risk factors potentially associated to the prevalence of Cryptosporidium and Giardia, including water-use practices, water sports and contact with domestic or pet animals. Molecular analyses were conducted using a nested-PCR technique to amplify the small-subunit (SSU) rRNA gene of Cryptosporidium and the triosephosphate isomerase (tpi) gene of Giardia. Cryptosporidium oocysts and Giardia cysts were found in 3 and 16 samples using the CpAg-ELISA, and in 5 and 9 samples using the ICT test, respectively. Cryptosporidium and Giardia were also found in 7 and 17 samples by CpAg-ELISA, and 4 and 14 samples by ICT, respectively, of 227 cattle fecal samples. The overall Cryptosporidium and Giardia infection prevalences, based on a Bayesian approach accounting for the imperfect sensitivities and specificities of both diagnostic tests, were estimated to 1.0% (95% BCI: 0.2%-2.8%) and 3.1% (1.5%-5.3%) in children and 3.0% (0.5%-9.2%) and 1.4% (0.0%-6.4%) in cattle, respectively. In humans, a single Cryptosporidium isolate was characterized as C. hominis. Of seven Giardia isolates, four were identified as assemblage B, two as assemblage A-II and one was a mixed assemblage B+A-II infection. No Cryptosporidium or Giardia isolates could be obtained from cattle samples. Although limited, these results seem to suggest that cattle are unlikely to be an important reservoir of zoonotic Cryptosporidium and/or Giardia in the province of Álava.

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.

Identification of a novel Assemblage B subgenotype and a zoonotic Assemblage C in human isolates of Giardia intestinalis in Egypt

Giardia intestinalis (G. intestinalis) is a flagellate parasite which has been considered the most common protozoan infecting human. Molecular techniques are of great value in studying the taxonomy, the zoonotic potential of animal isolates and the correlation between the genetic variability of the parasite and the range of clinical symptoms observed in humans. The present work aims at genotyping G. intestinalis isolates from Egypt using molecular techniques. PCR targeting the β-giardin locus, RFLP and sequencing were applied to 12 microscopically positive and 3 microscopically negative samples (which were positive by real time PCR targeting SSUr DNA). Two other loci, triose phosphate isomerase (TPI) gene and glutamate dehydrogenase (GDH) gene PCR and RFLP were also applied to all study isolates. The most frequent genotype was Assemblage B (13 out of 15), while Assemblage A and C were present in one sample each. This is the first report on zoonotic transmission of Assemblage C (dog genotype) to human in Egypt. Sequencing of the Assemblage B isolates revealed new subgenotypes with consistent mutations at specific positions, some of which were not characterized previously. The results shed light on the possibility that G. intestinalis can infect humans through a zoonotic route and open the door to wider investigations using different genetic loci to genotype Giardia isolates.

Intestinal parasitic infestation among children in a semi-urban Indian population

BACKGROUND

Survey on the prevalence of various intestinal parasitic infestations in different geographic regions is a prerequisite to obtain an accurate understanding of the burden and cause of intestinal parasitic infestations in a particular area. The aim of the present study was to determine the intestinal parasitic infestation among children in a semi-urban area.

MATERIALS AND METHODS

A total of 335 stool samples were collected, processed, and microscopically examined for intestinal parasites.

RESULTS

One hundred twenty-eight (38%) stool samples showed presence of ova/cysts. Multiple parasites were seen in 42 (32.8%) samples. Among the protozoans, Entamoeba histolytica (55.3%) was the most common followed by Giardia lamblia (40.4%). Ascaris lumbricoides and Hymenolepis nana (24.2%) were the most common helminths detected.

CONCLUSIONS

In most of the cases, intestinal parasitic infestation spreads due to low standards of personal hygiene, poor sanitation, non-usage of toilets and an illiterate population, thus suggesting regular surveys to help in devising optimum methods of control.

Risk of Giardia infection for drinking water and bathing in a peri-urban area in Sao Paulo, Brazil

A high incidence of waterborne diseases is observed worldwide and in order to address contamination problems prior to an outbreak, quantitative microbial risk assessment is a useful tool for estimating the risk of infection. The objective of this paper was to assess the probability of Giardia infection from consuming water from shallow wells in a peri-urban area. Giardia has been described as an important waterborne pathogen and reported in several water sources, including ground waters. Sixteen water samples were collected and examined according to the US EPA (1623, 2005). A Monte Carlo method was used to address the potential risk as described by the exponential dose response model. Giardia cysts occurred in 62.5% of the samples (<0.1-36.1 cysts/l). A median risk of 10⁻¹ for the population was estimated and the adult ingestion was the highest risk driver. This study illustrates the vulnerability of shallow well water supply systems in peri-urban areas.

Molecular diagnosis of infections and resistance in veterinary and human parasites

Since 1977, >2000 research papers described attempts to detect, identify and/or quantify parasites, or disease organisms carried by ecto-parasites, using DNA-based tests and 148 reviews of the topic were published. Despite this, only a few DNA-based tests for parasitic diseases are routinely available, and most of these are optional tests used occasionally in disease diagnosis. Malaria, trypanosomiasis, toxoplasmosis, leishmaniasis and cryptosporidiosis diagnosis may be assisted by DNA-based testing in some countries, but there are very few cases where the detection of veterinary parasites is assisted by DNA-based tests. The diagnoses of some bacterial (e.g. lyme disease) and viral diseases (e.g. tick borne encephalitis) which are transmitted by ecto-parasites more commonly use DNA-based tests, and research developing tests for these species makes up almost 20% of the literature. Other important uses of DNA-based tests are for epidemiological and risk assessment, quality control for food and water, forensic diagnosis and in parasite biology research. Some DNA-based tests for water-borne parasites, including Cryptosporidium and Giardia, are used in routine checks of water treatment, but forensic and food-testing applications have not been adopted in routine practice. Biological research, including epidemiological research, makes the widest use of DNA-based diagnostics, delivering enhanced understanding of parasites and guidelines for managing parasitic diseases. Despite the limited uptake of DNA-based tests to date, there is little doubt that they offer great potential to not only detect, identify and quantify parasites, but also to provide further information important for the implementation of parasite control strategies. For example, variant sequences within species of parasites and other organisms can be differentiated by tests in a manner similar to genetic testing in medicine or livestock breeding. If an association between DNA sequence and phenotype has been demonstrated, then qualities such as drug resistance, strain divergence, virulence, and origin of isolates could be inferred by DNA-based tests. No such tests are in clinical or commercial use in parasitology and few tests are available for other organisms. Why have DNA-based tests not had a bigger impact in veterinary and human medicine? To explore this question, technological, biological, economic and sociological factors must be considered. Additionally, a realistic expectation of research progress is needed. DNA-based tests could enhance parasite management in many ways, but patience, persistence and dedication will be needed to achieve this goal.

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.

[Prevalence of Giardia duodenalis assemblage B in humans in Zaragoza and León, Spain]

OBJECTIVES

To study Giardia duodenalis assemblages circulating in the health areas of two hospitals in Zaragoza and León (Spain).

METHODS

A total of 211 stool samples with Giardia were genotyped by PCR of the tpi gene.

RESULTS

Assemblage B was the most prevalent, both in Zaragoza (84,7%) and León (95,1%). The remaining isolates were identified as AII+B.

CONCLUSIONS

We detected the spread of G. duodenalis assemblage B in Zaragoza and in León, with an increase in its prevalence in Zaragoza compared to previous studies.

Genotypes of Giardia intestinalis clinical isolates of gastrointestinal symptomatic and asymptomatic Saudi children

Giardiasis is the most worldwide parasitic disease with the major clinical impact on infant and children. Two genotypes were reported commonly among humans (assemblage A and B). In this study, genotypes of Giardia intestinalis clinical isolates obtaining from 24 gastrointestinal symptomatic Saudi primary school children and 16 asymptomatic ones were explored by real-time polymerase chain reaction using the high resolution melting curve analysis targeting intergenic spacer (IGS) region rDNA of G. intestinalis. Children having acute, intermittent, and chronic diarrhea were 14, 5, and 5, respectively. Among all the giardiasis subjects, assemblage B was 37.5% followed by both of assemblages AI and AII with 30% and 27.5%, respectively. Mixed infection with the three previous assemblages was present in 5% of cases. Among symptomatic children, the prevalence of assemblage B was 62.5% then followed by assemblage AI (16.7%) and assemblage AII with 12.5%. All of the children who harbored G. intestinalis assemblages B were symptomatic, while asymptomatic ones had only assemblage AI and AII with 50% each. The difference was statistically highly significant. In symptomatic patients having acute diarrhea, assemblage B was present in 71.5%, while assemblage AI and AII were equal with 7.1%. All of the patients (14.3%) with mixed infection had acute diarrhea. In intermittent diarrhea, assemblage AI and B were equally distributed with 40% each. In chronic diarrhea, assemblage AI and AII were equal with 20% each, while assemblage B was found in 60%. The difference was statistically not significant. In conclusion, assemblage B is the commonest, while assemblage A is a predominant in symptomatic and asymptomatic giardiasis Saudi children, respectively. So human transmission is the common risk factor among symptomatic, while zoonotic transmission is a common risk factor in asymptomatic ones. On the other hand, a strong correlation between assemblage B and symptoms and no relation between genotypes and types of diarrhea are found. Also, PCR with HRM in one-step closed-tube methods is able to genotype G. intestinalis IGS rDNA without using the sequencing methods or the electrophoresis.

Prevalence and clinical correlations of genetic subtypes of Giardia lamblia in an urban setting

The clinical significance of different genetic subtypes or assemblages of Giardia lamblia is uncertain. Cases of giardiasis in south-west London between 1999 and 2005 were studied, comparing molecular-typing results with clinical and epidemiological findings from routine surveillance. We identified 819 cases, of whom 389 returned surveillance questionnaires. A subset of 267 faecal samples was submitted for typing by sequencing of the triose phosphate isomerase (tpi) and ribosomal RNA genes, and/or a separate duplex PCR of the tpi gene. Typing was successful in 199 (75%) samples by at least one of the molecular methods. Assemblage A accounted for 48 (24%) samples and Assemblage B for 145 (73%); six (3%) were mixed. Both assemblages had similar seasonality, age distribution and association with travel. Clinical features were available for 59 successfully typed cases: both assemblages caused similar illness, but Assemblage A was significantly more frequently associated with fever than Assemblage B.

Giardia intestinalis in Thailand: identification of genotypes

This study was undertaken to determine the genetic diversities of Giardia intestinalis isolated in Thailand. G. intestinalis cysts were collected from stool samples of 61 subjects residing in Bangkok or in rural communities of Thailand with and without gastrointestinal symptoms. All the cyst samples gave positive tpi amplicons (100% sensitivity), either of the 148- or the 81-bp tpi segments. Cyst assemblage identification of the 148- and 81-bp tpi gene segments by polymerase chain reaction showed that 8% of the cysts were assemblage A, 41% assemblage A and B combined, and 51% assemblage B. The prevalence of assemblage A was significantly lower than that of assemblage B and the mixed types. Restriction fragment length polymorphism (RFLP) of the 384-bp beta-giardin gene segment revealed that 12% and 88% of the assemblage A cysts were AI and AII respectively. RFLP, based on the 432-bp gdh gene segment, showed 45.5% of the assemblage B cysts to be BIII and 54.5% to be BIV. The AI sub-assemblage was less prevalent than the others. All subjects with AI and 50% of the subjects with BIII sub-assemblage cysts were symptomatic; 80% of symptomatic Bangkok residents were adults/elderly while 85% of the rural cases were children.

Real-time PCR/RFLP assay to detect Giardia intestinalis genotypes in human isolates with diarrhea in Egypt

Two major genotypic assemblages of Giardia intestinalis infect humans; the nested real-time polymerase chain reaction (PCR) was used for targeting the triose phosphate isomerase (tpi) gene to detect and genotype G. intestinalis in human feces in Egypt. Among 97 fecal samples, 30 (31%) were diagnosed as giardiasis by saline wet mount microscopy after staining with Lugol's iodine. The tpi gene was amplified from 41 (42.3%) fecal samples, of which 11 were microscopy-negative specimens. Of the total samples, 24 (58.5%) contained assemblage A group I, and 7 (17.1%) were assemblage A group II from the group of patients complaining of intermittent diarrhea. Eight (19.5%) samples contained assemblage B from patients with persistent diarrhea. Two (5%) samples had a mixture of assemblage A group II and assemblage B. The technique was able to detect as few as 20 trophozoites per PCR on fecal DNA-isolated, microscopy-negative, and quantitative (q)PCR-positive specimens; there was a higher average cycle threshold value than microscopy-positive and qPCR-positive specimens, suggesting that they represented true, low-burden infections. In conclusion, we could genotype G. intestinalis from fresh stool samples in Egypt; in infections commonly presented with intermittent diarrhea, the most prevalent genotype was assemblage A group I. The most vulnerable age group included 10- to 20-yr-old individuals.

Sexual transmission of intestinal parasites in men who have sex with men

Direct oral-anal sexual contact is a common practice among men who have sex with men (MSM) and is implicated in the transmission of various enteric pathogens including intestinal parasites. The present study reviewed data on the sexual transmission of intestinal parasites among MSM, and highlighted advances in the diagnosis of such infections. The emergence and spread of intestinal parasites is of public health concern particularly in the homosexual community. Intestinal parasitic infection should be considered in the differential diagnosis of gastrointestinal disease in this population. Combination of traditional diagnostic procedures with implementation of testing based on novel molecular methods in the accurate identification of intestinal parasites is important so that early intervention and control of infection is facilitated.

Multilocus genotyping of Cryptosporidium and Giardia in non-outbreak related cases of diarrhoea in human patients in Belgium

Stool samples from Belgian patients suffering from abdominal pain and/or diarrhoea were examined for Cryptosporidium and Giardia. Cryptosporidium-positive samples were genotyped using the 70 kDa heat shock protein and the 60 kDa glycoprotein (GP60) genes: C. hominis was identified in 54.2% and C. parvum in 45.8% of the samples. Sequencing at the GP60 locus indicated that subgenotype IbA10G2 of C. hominis and subgenotype IIaA15G2R1 of C. parvum were the most prevalent, although several other subgenotypes were identified. For Giardia, sequencing at the beta-giardin, triose phosphate isomerase (TPI) and glutamate dehydrogenase (GDH) genes revealed assemblage B as the most prevalent (74.4%) in human patients. A high degree of heterogeneity was found, especially on the beta-giardin gene, and to a lesser extent on the GDH gene. Furthermore, using a novel species-specific PCR based on the TPI gene, mixed infections with both assemblage A and B were detected in a large number (32.4%) of human patients, which might have important epidemiological implications.

Molecular characterisation of Giardiaduodenalis in captive non-human primates reveals mixed assemblage A and B infections and novel polymorphisms

Giardia is frequently detected in stools of non-human primates (NHP). However, a molecular identification has been rarely applied to Giardia isolates from NHP, and the distribution of the zoonotic assemblages A and B remains unclear. Moreover, little is known about the genetic variability among the isolates, although this may contribute to the elucidation of the different transmission pathways, including the role of NHP as a reservoir for human giardiasis. Therefore, 258 Giardia samples from 31 NHP species housed in nine zoological gardens and one sanctuary in Belgium and The Netherlands were characterised based on an assemblage-specific PCR targeting the triose phosphate isomerase (tpi) gene to identify both assemblage A and B infections. In addition, a multi-locus sequencing approach based on the glutamate dehydrogenase, the tpi and the beta-giardin genes was used to examine both the genetic variability and the ability to allocate these isolates to different NHP groups. Overall, assemblage B was the most prevalent (78.6%), but mixed assemblage A and B infections occurred in 32.7% of the samples. Sequencing of the isolates revealed the presence of new polymorphisms for both assemblages and at the three loci examined. The majority of the assemblage B isolates could not be grouped into recently described sub-assemblages, particularly at the tpi gene. Isolates could only be allocated to a specific group when polymorphisms of the three loci were combined. The results confirm that NHP are a potential reservoir for zoonotic transmission and advocate the use of assemblage-specific primers in molecular epidemiological surveys, as mixed infections are likely to be underestimated. The high level of heterogeneity within assemblages indicates that a revised nomenclature of these sub-assemblages is needed, but points out the potency of a multi-locus sequencing approach to unravel the complex epidemiology of Giardia duodenalis.

Quantification of Giardia transcripts during in vitro excystation: interest for the estimation of cyst viability

The aim of the present study was to evaluate the potential of transcript quantification as an indicator of Giardia cyst viability. The variations of beta-giardin, EF1A and ADHE mRNAs were quantified during excystation by real-time RT-PCR assays and compared with the percentages of viability estimated using propidium iodide staining and in vitro excystation. The first experiments were performed with purified G. duodenalis assemblage B cysts. When 55% of excysting protozoa were observed, the increase of the selected transcripts ranged from 0.40+/-0.13 to 0.97+/-0.11 log10 after 1h of incubation in excystation medium. Purified cysts were also stored at 4 degrees C for up to 56 days and analysed at several sampling times. Significant correlations were observed between the variations of the selected mRNAs and the percentages of viability estimated with staining and excystation methods. Among the three transcripts, beta-giardin appeared to be the most appropriate to study the viability of Giardia cysts concentrated from wastewater samples.

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

To evaluate the geographic distribution of Giardia intestinalis genotypes in Nablus, West Bank, Palestine, a genotyping study was performed using clinical fecal samples. Microscopic examination confirmed that 8 of 69 (11.6%) samples were G. intestinalis positive, and subsequent genotyping analyses targeting the small-subunit ribosomal RNA (18S rRNA) and glutamate dehydrogenase (GDH) genes revealed the G. intestinalis genotypes within the 8 samples. Of these 8 samples, 6 were clustered with assemblage A-II and the remaining 2 samples were clustered with assemblage B by 18S rRNA gene analysis; however, direct sequencing of the GDH gene segments from the latter 2 samples showed a mixed infection profile. To assess those samples, we employed a subcloning approach and successfully isolated 6 independent assemblage B subgenotypes. These partial GDH gene sequences (393 bp) had 15 single-nucleotide polymorphisms, all of which were synonymous transition substitutions at the third nucleotide position of codons. From the results, we concluded that the highly polymorphic gene loci such as GDH gene locus might provide us an opportunity to obtain a detailed molecular data even from the samples with multiple-subgenotype mixed infections. Therefore, subcloning approach is recommended in genotyping studies, especially in those conducted in giardiasis-endemic areas, where the repeated and cumulative infections could be commonly expected.

Is Giardia a significant pathogen in production animals?

Although Giardia duodenalis is recognised worldwide as the most important parasitic cause of gastro-intestinal disorder in human patients, the relevance of infection in production animals is prone to debate. Since the 1980s, clinical disease has been associated with giardiasis in production animals, both in natural conditions and in experimental studies. However, most Giardia research is focussed on the relevance of production animals as a reservoir for zoonotic transmission. In this study, the current knowledge on clinical relevance of giardiasis in production animals is reviewed, along with the diagnosis, treatment and control of infection. Furthermore, future research objectives are discussed.

Giardia duodenalis assemblages associated with diarrhea in children in South India identified by PCR-RFLP

Giardial diarrhea in a birth cohort of 452 children in an urban slum in South India was characterized. Of the 155 episodes that occurred in 99 children, 73% were acute diarrhea. Children with better educated mothers and a toilet at home had lower odds of acquiring giardial diarrhea, whereas low socioeconomic status and drinking municipal water were associated with greater risk. Children with co-infections tended to have a slightly longer duration of diarrhea (P = 0.061) and showed significantly more wasting after an episode than children with diarrhea resulting from Giardia alone (P = 0.032). Among the 99 cases, 50 diarrheal and 51 asymptomatic Giardia positive samples were genotyped by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) at the triose phosphate isomerase gene. Assemblage B was predominant both in giardial diarrhea (80%) and asymptomatic giardiasis (94%). Children with Assemblage A subgroup-II alone or dual infections with both assemblage A and B had diarrhea more frequently (P = 0.07).

First genotyping of Giardia lamblia from human and animal feces in Argentina, South America

The purpose of this study was to investigate the genotypes of Giardia lamblia from human and animal feces and their epidemiological and clinical characteristics in Argentina, South America. Seventy isolates, 60 from humans (adults and children), eight from dogs and two from cows were processed by polymerase chain reaction-restriction fragment length polymorphism. Data corresponding to demographic, socio-cultural and environmental variables and presence/absence of signs/symptoms were collected. The triosephosphate isomerase gene was amplified from 43 (71.66%) of the 60 human fecal samples. Among these, 3/43 (6.98%) were genotype AII and 40/43 (93.02%) were genotype B. Assemblage AII was detected in three children who lived together in a shantytown and they were oligosymptomatic and none had diarrhea. This genotype was not found in animals. Genotype B showed a high prevalence in both adults and children. It was also found in polysymptomatic people, many of whom presented diarrhea. It was also found only in one dog. The present study represents the first contribution to the knowledge of G. lamblia genotypes in Argentina.

Identification of genotypes of Giardia intestinalis of human isolates in Egypt

In Egypt, the genotyping study of Giardia intestinalis in human is limited. To determine the prevalence of G. intestinalis, faecal samples were collected from Egypt. Samples were concentrated using density gradient centrifugation. The samples were subjected to PCR and DNA sequence analysis for TPI gene. Prevalence of Giardia infection was 34.6% of 52 examined. DNA sequence showed that the Assemblage B was the most prevalent (80%) genotype, the 15% of the positive samples belonged to Assemblage E, and the 5% of them belonged to Assemblage A. Certainly, both genotypes A and B are highly common in human worldwide. However, up to now, Assemblage E had not been known to be infectious for humans. Therefore, this is the first time that Assemblage E is reported in human. However, further analyses of a second locus are required to confirm this result. The extent to which Giardia-infected cattle in Egypt might pose a risk of human infection is unknown.

Identification of zoonotic Giardia genotypes in marsupials in Australia

A total of 421 fecal samples from a variety of captive and wild marsupial hosts in Western Australia, Victoria and South Australia were screened for the presence of Giardia species/genotypes using PCR and sequence analysis of a fragment of the 18S rRNA gene. Giardia spp. were identified in 13.4% (28/209) of samples from captive marsupials and 13.7% (29/212) of samples from wild marsupials. Sequence analysis at the 18S locus identified the zoonotic Giardia duodenalis Genotypes A and B in both captive and wild marsupials. Eight isolates were typed as genotype B3 and B4 at the gdh locus, although 7/8 were typed as genotype A at the 18S rRNA locus. The possible reasons for this discordance are discussed. This is the first report of genotype B and only the second report of genotype A in marsupials. As some of the genotype B isolates were identical to human-derived Giardia gdh sequences, these results suggest that marsupials in catchments may pose a public health risk and therefore warrant further investigation.

Giardia duodenalis assemblage, clinical presentation and markers of intestinal inflammation in Brazilian children

Data on the relationship between the two genotypes of Giardia duodenalis that infect humans, assemblages A and B, their clinical presentation and intestinal inflammation are limited. We analyzed 108 stool samples previously collected for a diarrhoeal study among Brazilian children, representing 71 infections in 47 children. Assemblage B was most prevalent, accounting for 43/58 (74.1%) infections, while assemblage A accounted for 9/58 (15.5%) infections and 6/58 (10.3%) infections were mixed (contained both assemblage A and B). There was no significant difference in diarrhoeal symptoms experienced during assemblage A, B or mixed infections. Children with assemblage B demonstrated greater variability in G. duodenalis cyst shedding but at an overall greater level (n=43, mean 3.6 x 10(5), range 5.3 x 10(2)-2.5 x 10(6)cysts/ml) than children infected with assemblage A (n=9, mean 1.4 x 10(5), range 1.5 x 10(4)-4.6 x 10(5)cysts/ml; P=0.009). Children with mixed infections shed more cysts (mean 8.3 x 10(5), range 3.1 x 10(4)-2.8 x 10(6)cysts/ml) than children with assemblage A or B alone (P=0.069 and P=0.046 respectively). This higher rate of cyst shedding in children with assemblage B may promote its spread, accounting for its increased incidence. Additionally, second and third infections had decreasing faecal lactoferrin, suggesting some protection against severity, albeit not against infection, by prior infection.

Giardia duodenalis assemblage, clinical presentation and markers of intestinal inflammation in Brazilian children

Data on the relationship between the two genotypes of Giardia duodenalis that infect humans, assemblages A and B, their clinical presentation and intestinal inflammation are limited. We analyzed 108 stool samples previously collected for a diarrhoeal study among Brazilian children, representing 71 infections in 47 children. Assemblage B was most prevalent, accounting for 43/58 (74.1%) infections, while assemblage A accounted for 9/58 (15.5%) infections and 6/58 (10.3%) infections were mixed (contained both assemblage A and B). There was no significant difference in diarrhoeal symptoms experienced during assemblage A, B or mixed infections. Children with assemblage B demonstrated greater variability in G. duodenalis cyst shedding but at an overall greater level (n=43, mean 3.6 x 10(5), range 5.3 x 10(2)-2.5 x 10(6)cysts/ml) than children infected with assemblage A (n=9, mean 1.4 x 10(5), range 1.5 x 10(4)-4.6 x 10(5)cysts/ml; P=0.009). Children with mixed infections shed more cysts (mean 8.3 x 10(5), range 3.1 x 10(4)-2.8 x 10(6)cysts/ml) than children with assemblage A or B alone (P=0.069 and P=0.046 respectively). This higher rate of cyst shedding in children with assemblage B may promote its spread, accounting for its increased incidence. Additionally, second and third infections had decreasing faecal lactoferrin, suggesting some protection against severity, albeit not against infection, by prior infection.

Molecular epidemiology of giardiasis

Giardia duodenalis is a widespread parasite of mammalian species, including humans. Due to its invariant morphology, investigation on aspects such as host specificity and transmission patterns requires a direct genetic characterization of cysts/trophozoites from host samples. A number of molecular assays have been developed to help unravel the complex epidemiology of this infection. A coherent picture has emerged from those studies, indicating the existence of seven genetic groups (or assemblages), two of which (A and B) are found in both humans and animals, whereas the remaining five (C-G) are host-specific. Sequence-based surveys have identified a number of genotypes within assemblages A and B in animal species, some of which may have zoonotic potential. Recently, however, molecular approaches have been complicated by the recognition of intra-isolate sequence heterogeneity (i.e., "mixed templates", that affects identification of subtypes within each assemblage), and by the unreliable assignment of isolates to G. duodenalis assemblages generated by different genetic markers. This raises concerns about previous interpretation of genotyping data, especially when single genetic markers have been used. The mechanisms that may be responsible for these findings, including allelic sequence heterozygosity and meiotic recombination, are discussed.

Correlation between the presence of symptoms and the Giardia duodenalis genotype

Clinical manifestations of Giardia duodenalis infection vary from asymptomatic infection to chronic diarrhoea. We study the correlation between the presence of symptoms and the G. duodenalis genotype in 108 patients with giardiasis. Patient age ranged from 2 to 72 years old. We found a correlation between assemblage AII and symptomatic infections, and between assemblage B and asymptomatic infections in the overall patient group and in patients less than five years of age. Nevertheless, if only patients of more than five years of age were considered, no statistically significant relationship between assemblage and symptomatic or asymptomatic Giardia infections was found. In these patients, host factors may affect the presence of clinical manifestations more than Giardia assemblage.

Giardia cysts in sewage influent in Bergen, Norway 15-23 months after an extensive waterborne outbreak of giardiasis

AIMS

In autumn/winter 2004, a large outbreak of waterborne giardiasis occurred in Bergen, Norway. Over 1 year later, the concentrations and genotypes of Giardia cysts occurring in sewage influent were studied to investigate the impact of the outbreak event on Giardia infections in the community.

METHODS AND RESULTS

Sewage influent samples from four sewage treatment works (STW) serving Bergen were analysed for Giardia cysts on four occasions between 15 and 23 months after the outbreak. Cysts genotypes were investigated at one to three genes. Data from influent analysis from one of the STW before the outbreak, and from patient faecal samples analysed during the outbreak, provided baseline comparative data. Relatively high concentrations of Giardia cysts of diverse genotypes, both from Assemblages A and B, were detected at all STW.

CONCLUSIONS

Comparison of data suggests that although Giardia cyst concentrations in sewage influent returned to pre-outbreak levels within 18 months after the outbreak peak, the genetic composition of the isolates remained significantly influenced by the Assemblage B isolate associated with the outbreak.

SIGNIFICANCE AND IMPACT OF THE STUDY

Genotypes associated with an extensive outbreak of giardiasis continued to occur in Giardia infections in Bergen's population many months after the outbreak was considered to be over.

Molecular identification of Giardia duodenalis isolates from humans, dogs, cats and cattle from the state of São Paulo, Brazil, by sequence analysis of fragments of glutamate dehydrogenase (gdh) coding gene

The nucleotide sequence of glutamate dehydrogenase (gdh) coding genes were obtained from cysts of Giardia duodenalis isolated from feces of naturally infected cats (n=19), dogs (n=27), humans (n=37) and cattle (n=5). The samples were from several municipalities within the state of São Paulo, Brazil and were collected from January 2004 to August 2006. Sequences analysis of the 37 specimens recovered from humans revealed 29 G. duodenalis assemblage AII and 8 G. duodenalis assemblage B. Among samples from cats, 11 were classified into assemblage F and 8 into assemblage AI. Only the host-adapted assemblages C and D were detected in samples from dogs (7 and 20, respectively). Among the samples from cattle, the genotype livestock was found in four samples and the assemblage AI was detected in one sample. The molecular identification of assemblages of G. duodenalis isolates from different hosts reveals that genetic diversity of this protozoon in Brazil is similar to that of Giardias from other parts of the world.

Sensitivity of nested PCR in the detection of low numbers of Giardia lamblia cysts

Nested PCR was performed on individually isolated Giardia lamblia cysts in replicates of 50 for sets of 1, 2, 3, 4, 5, 7, and 10 cysts. Amplification ranged from 80% for 1 cyst to 100% for 10 cysts. The results suggest that nested PCR is well adapted for G. lamblia single-cyst detection.

Comparative evaluation ofGiardia duodenalissequence data

A review of theGiardia duodenalissequences currently available on the GenBank database was completed to compare the different genotyping loci (small subunit ribosomal DNA, glutamate dehydrogenase, triose-phosphate isomerase and beta giardin) for their ability to discern assemblage and subassemblage groups and infer phylogenetic relationships. In total, 405Giardia duodenalissequences were sorted and aligned to examine the substitutions within and between the assemblages – A and B (zoonotic), C and D (dogs), E (livestock), F (cats) and G (rodents). It was found that all of the genes could reproducibly group isolates into their assemblages and that the AI/AII subassemblage groups were robust and identifiable at all loci. However, the assemblage B subgroups were not reproducible at half of the loci (small subunit ribosomal DNA and beta giardin), not due to their conserved nature, but because there was insufficient sequence data of reference isolates available for comparison. It is anticipated that further investigation of these loci may reveal the core subgroups of this medically important and zoonotic assemblage and also those of others. The closer, more recent, phylogenetic relationships amongst the assemblages appear to be resolved; however, more sequence data from the current loci, and possibly new loci, will be required to establish the remaining relationships.

Molecular characterization of human isolates of Giardia duodenalis from Ethiopia

Giardia duodenalis, a flagellated protozoan, represents a common cause of gastroenteritis in Ethiopia, however very little information is available on the epidemiology and transmission routes of this pathogen, and a genetic characterization of the parasite has never been attempted in this country. The aim of this study was the genetic analysis of human isolates of G. duodenalis collected in different localities across the country, both from urban and rural areas. A fragment of the beta-giardin gene was amplified by nested PCR and analyzed by restriction and sequence analyses. Of the 59 isolates examined, 31 (52%) were typed as assemblage A and 13 (22%) as assemblage B. A strong correlation between the presence of symptoms and infection with assemblage B was observed. The remaining 15 (25%) isolates were typed as mixed infections by PCR-RFLP, specifically, A+F (in seven isolates) and A+B (in eight isolates). Sequencing of the A+F products confirmed the presence of assemblage F in three isolates, whereas the remaining four were identified as assemblage A. The detection of assemblage F, a cat-specific assemblage that to date has not been associated with human infections, was not able to be confirmed by the analysis of two commonly used markers (small subunit ribosomal RNA and triosephosphate isomerase). The analysis of the one isolate that was successfully amplified with the glutamate dehydrogenase primers unambiguously identified it as G. duodenalis, yet it was distinct from the established A and F sequences; thus the exact genetic identity of these isolates remains unclear.

Genotyping of Giardia duodenalis isolates among residents of slum area in Manila, Philippines

Giardia duodenalis is a flagellated protist that causes gastrointestinal disease throughout the world. In the Philippines, study on G. duodenalis is limited. It is also believed that prevalence rates of this organism in the country are underestimated. In this study, stool samples from residents living in a slum area in Manila were collected. These were examined under microscopy for identification of common helminthic and protistan parasites. Results showed that 22.05% of 2,354 stool samples collected contained Giardia cysts. A fraction of samples (n = 133) positive for Giardia cysts were set aside. Genomic DNA was extracted from these samples and a polymerase chain reaction-restriction fragment length polymorphism procedure based on the organism's triose phosphate isomerase gene was utilized. This particular procedure is capable of distinguishing assemblages or genotypes within G. duodenalis. The highest identified assemblage was Assemblage B (86.47%). The two genotypes of Assemblage A were also detected. This is the first report on the identification of genotypes of G. duodenalis in the Philippines. The results of this study can serve as basis for future control and prevention of giardiasis and parasitism in the country.

Detection and genotyping of Giardia intestinalis isolates using intergenic spacers(IGS)-based PCR

Giardia intestinalis infections arise primarily from contaminated food or water. Zoonotic transmission is possible, and at least 7 major assemblages including 2 assemblages recovered from humans have been identified. The determination of the genotype of G. intestinalis is useful not only for assessing the correlation of clinical symptoms and genotypes, but also for finding the infection route and its causative agent in epidemiological studies. In this study, methods to identify the genotypes more specifically than the known 2 genotypes recovered from humans have been developed using the intergenic spacer (IGS) region of rDNA. The IGS region contains varying sequences and is thus suitable for comparing isolates once they are classified as the same strain. Genomic DNA was extracted from cysts isolated from the feces of 5 Chinese, 2 Laotians and 2 Koreans infected with G. intestinalis and the trophozoites of WB, K1, and GS strains cultured in the laboratory, respectively. The rDNA containing the IGS region was amplified by PCR and cloned. The nucleotide sequence of the 3' end of IGS region was determined and examined by multiple alignment and phylogenetic analysis. Based on the nucleotide sequence of the IGS region, 13 G. intestinalis isolates were classified to assemblages A and B, and assemblage A was subdivided into A1 and A2. Then, the primers specific to each assemblage were designed, and PCR was performed using those primers. It detected as little as 10 pg of DNA, and the PCR amplified products with the specific length to each assemblage (A1, 176 bp; A2, 261 bp; B, 319 bp) were found. The PCR specific to 3 assemblages of G. intestinalis did not react with other bacteria or protozoans, and it did not react with G. intestinalis isolates obtained from dogs and rats. It was thus confirmed that by applying this PCR method amplifying the IGS region, the detection of G. intestinalis and its genotyping can be determined simultaneously.

Global impact of diarrheal diseases that are sampled by travelers: the rest of the hippopotamus

Travelers who experience diarrhea (i.e., "turista") are exposed to the same pathogens and illnesses that pose some of the greatest threats to life and development among malnourished children in developing areas around the world, where inadequate water and poor sanitation remain. This article focuses on new findings about the impact, diagnosis, and control of these illnesses and the genetic predispositions of persons who acquire them. Despite the reductions in mortality due to dehydrating diarrhea, the morbidity associated with diarrheal illnesses continues unabated. Furthermore, we increasingly recognize the lasting detrimental effects of enteric infections that occur during early childhood on later physical and cognitive development and, in patients with acquired immunodeficiency syndrome, on the absorption of antiretroviral drugs. Genetic predispositions to inflammation and potential protection associated with such alleles as ApoE4, which are not suspected of being involved in diarrhea, remind us of how much we have to learn about the effect and interactions of enteric tropical infectious diseases with regard to our host genome. New diagnostic methods hold promise for improved recognition and, hopefully, control of enteric infections worldwide.