An up-date on Giardia and giardiasis

Molecular Characterization of Giardia intestinalis Detected in Humans and Water Samples in Egypt

BACKGROUND

Giardia intestinalis is a common cause of gastrointestinal illness especially in children of developing countries. Giardia assemblages A and B are the major human infective genotypes.

OBJECTIVE

The present study aimed to investigate the role of water supply in the epidemiology of giardiasis via genotyping G. intestinalis detected in diarrheic children and in water samples in Egyptian rural areas.

METHODS

Stool samples of 100 diarrheic children, 40 drinking water samples and 10 raw water samples of canals were examined microscopically for Giardia. DNA was extracted from microscopically positive faecal samples and from all of the collected water samples. Amplification of Giardia tpi gene was performed by a nested PCR using assemblage A- and assemblage B-specific primers. Giardia gdh gene was amplified by a heminested PCR. Giardia genotypes were determined by restriction fragment polymorphism (RFLP) analysis of the amplified products. Sequencing of the amplified products was performed in two faecal and two water samples RESULTS: Giardia intestinalis was detected in 24 children, in none of the drinking water samples and in all canal water samples. Giardia sub-assemblage AII was identified in all stool and raw water samples. The RFLP pattern was confirmed in sequenced samples.

CONCLUSION

The presence of the same Giardia sub-assemblage in diarrheic children and in raw water samples shows by molecular evidence the potential for waterborne dissemination of Giardia in Egypt. Further studies are needed to monitor cyst levels and infectivity of the genotype detected in water for risk assessment and management.

Longitudinal analysis of Giardia duodenalis assemblages in animals inhabiting drinking water catchments in New South Wales and Queensland - Australia (2013-2015)

Giardia duodenalis is one of the most common waterborne zoonotic parasites worldwide, and its occurrence in the environment and catchment reservoir water has serious implications for management of drinking water. The aim of the present study was to use molecular tools to identify the Giardia spp. infecting animals inhabiting five drinking water catchments across two states in Australia; New South Wales and Queensland, to better understand the potential health risks they pose. We used quantitative PCR to screen a total of 2174 faecal samples collected from dominant host species in catchment areas for the presence of G. duodenalis. All samples positive for G. duodenalis were further characterized and subtyped at tpi and gdh loci, respectively. The overall prevalence of G. duodenalis was 15.3% (332/2174, 95%CI; 13.8-16.9), and two zoonotic assemblages (assemblages A and B) and one potentially zoonotic assemblage (E) were detected in various host species. Additional subtyping of a subset of samples (n = 76) identified four human infectious sub-assemblages including AI, AII, BII-like and BIV-like, all of which have been previously reported in humans in Australia. The finding of zoonotic assemblages of G. duodenalis in the present study necessitates continued identification of the sources/carriers of human pathogenic strains in drinking water catchment areas for more accurate risk assessment and optimal catchment management.

Isolation and Functions of Extracellular Vesicles Derived from Parasites: The Promise of a New Era in Immunotherapy, Vaccination, and Diagnosis

Experimental and epidemiological evidence shows that parasites, particularly helminths, play a central role in balancing the host immunity. It was demonstrated that parasites can modulate immune responses via their excretory/secretory (ES) and some specific proteins. Extracellular vesicles (EVs) are nano-scale particles that are released from eukaryotic and prokaryotic cells. EVs in parasitological studies have been mostly employed for immunotherapy of autoimmune diseases, vaccination, and diagnosis. EVs can carry virulence factors and play a central role in the development of parasites in host cells. These molecules can manipulate the immune responses through transcriptional changes. Moreover, EVs derived from helminths modulate the immune system via provoking anti-inflammatory cytokines. On the other hand, EVs from parasite protozoa can induce efficient immunity, that makes them useful for probable next-generation vaccines. In addition, it seems that EVs from parasites may provide new diagnostic approaches for parasitic infections. In the current study, we reviewed isolation methods, functions, and applications of parasite's EVs in immunotherapy, vaccination, and diagnosis.

Cryptosporidium and Giardia in Ruminants

Cryptosporidium and Giardia are ubiquitous protozoan parasites that infect a broad range of vertebrate hosts, including domestic and wild animals as well as humans. Both parasites are of medical and veterinary importance. Infections with Cryptosporidium and Giardia in ruminants are associated with diarrhea outbreaks, mainly in young animals. Ruminants are potential sources of infection for humans because some species of Cryptosporidium and assemblages of Giardia duodenalis have been isolated from both ruminants and humans. Knowledge of these parasites has greatly expanded in the last 2 decades from simple microscopic observations of organisms to the knowledge acquired from molecular tools.

Giardia lamblia Decreases NF-κB p65RelA Protein Levels and Modulates LPS-Induced Pro-Inflammatory Response in Macrophages

The protozoan Giardia lamblia is the most common cause of parasitic gastrointestinal infection worldwide. The parasite developed sophisticated, yet not completely disclosed, mechanisms to escape immune system and growth in the intestine. To further understand the interaction of G. lamblia with host immune cells, we investigated the ability of parasites to modulate the canonical activation of mouse macrophages (Raw 264.7 cell line) and human monocyte-derived macrophages triggered by the TLR4 agonist, lipopolysaccharide (LPS). We observed that G. lamblia impairs LPS-evoked pro-inflammatory status in these macrophage-like cells through inhibition of cyclooxygenase-2 and inducible nitric oxide synthase expression and subsequent NO production. This effect was in part due to the activity of three G. lamblia proteases, a 135 kDa metalloprotease and two cysteine proteases with 75 and 63 kDa, that cleave the p65^RelA subunit of the nuclear factor-kappa B (NF-κB). Moreover, Tnf and Ccl4 transcription was increased in the presence of the parasite. Overall, our data indicates that G. lamblia modulates macrophages inflammatory response through impairment of the NF-κB, thus silencing a crucial signaling pathway of the host innate immune response.

The Chymase Mouse Mast Cell Protease-4 Regulates Intestinal Cytokine Expression in Mature Adult Mice Infected with Giardia intestinalis

Mast cells have been shown to affect the control of infections with the protozoan parasite Giardia intestinalis. Recently, we demonstrated that Giardia excretory-secretory proteins inhibited the activity of the connective tissue mast cell-specific protease chymase. To study the potential role of the chymase mouse mast cell protease (mMCP)-4 during infections with Giardia, mMCP-4^+/+ and mMCP-4^−/− littermate mice were gavage-infected with G. intestinalis trophozoites of the human assemblage B isolate GS. No significant changes in weight gain was observed in infected young (≈10 weeks old) mMCP-4^−/− and mMCP-4^+/+ littermate mice. In contrast, infections of mature adult mice (>18 weeks old) caused significant weight loss as compared to uninfected control mice. We detected a more rapid weight loss in mMCP-4^−/− mice as compared to littermate mMCP-4^+/+ mice. Submucosal mast cell and granulocyte counts in jejunum increased in the infected adult mMCP-4^−/− and mMCP-4^+/+ mice. This increase was correlated with an augmented intestinal trypsin-like and chymotrypsin-like activity, but the myeloperoxidase activity was constant. Infected mice showed a significantly lower intestinal neutrophil elastase (NE) activity, and in vitro, soluble Giardia proteins inhibited human recombinant NE. Serum levels of IL-6 were significantly increased eight and 13 days post infection (dpi), while intestinal IL-6 levels showed a trend to significant increase 8 dpi. Strikingly, the lack of mMCP-4 resulted in significantly less intestinal transcriptional upregulation of IL-6, TNF-α, IL-25, CXCL2, IL-2, IL-4, IL-5, and IL-10 in the Giardia-infected mature adult mice, suggesting that chymase may play a regulatory role in intestinal cytokine responses.

An image-based Pathogen Box screen identifies new compounds with anti-Giardia activity and highlights the importance of assay choice in phenotypic drug discovery

Giardia duodenalis, the most prevalent human intestinal parasite causes the disease, giardiasis. On an annual basis G. duodenalis infects ~1 billion people, of which ~280 million develop symptomatic disease. Giardiasis can be severe and chronic, causing malnutrition, stunted growth and poor cognitive development in children. Current treatment options rely on drugs with declining efficacy and side-effects. To improve the health and well-being of millions of people world-wide, new anti-Giardia drugs with different modes of action to currently used drugs are required. The Medicines for Malaria Venture's Pathogen Box, a collection of bio-active compounds specifically chosen to stimulate infectious disease drug discovery, represents an opportunity for the discovery of new anti-Giardia agents. While the anti-Giardia activity of Pathogen Box compounds has been reported, this work failed to identify known anti-Giardia controls within the compound set. It also reported the activity of compounds previously screened and shown to be inactive by others, suggesting data may be inaccurate. Given these concerns the anti-Giardia activity of Pathogen Box compounds was re-assessed in the current study. Data from this work identified thirteen compounds with anti-Giardia IC₅₀ values ≤2 μM. Five of these compounds were reference compounds (marketed drugs with known anti-microbial activity), or analogues of compounds with previously described anti-Giardia activity. However, eight, including MMV676358 and MMV028694, which demonstrated potent sub-μM IC₅₀s against assemblage A, B and metronidazole resistant parasites (0.3 μM and 0.9 μM respectively), may represent new leads for future drug development. Interestingly, only four of these compounds were identified in the previously reported Pathogen Box screen highlighting the importance of assay selection and design when assessing compounds for activity against infectious agents.

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13 compounds with anti-Giardia IC₅₀ values < 2 μM were identified.

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8 compounds represent new leads for drug development.

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MMV676358 and MMV028694 demonstrated the most promising acting.

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Data highlight the importance of assay selection and design in drug discovery.

Efficacy of Ageratum conyzoides extracts against Giardia duodenalis trophozoites: an experimental study

Background

Giardia duodenalis causes giardiasis in humans, particularly in developing countries. Despite the availability of treatments, resistance to some of the commercial anti-Giardia drugs has been reported in addition to their harmful side effects. Therefore, novel treatments for giardiasis are required. In this study, we aimed to assess the in vitro activity of crude extracts of Ageratum conyzoides against G. duodenalis trophozoites.

Methods

Plants were classified into three groups based on their flower colors: white (W), purple (P), and white–purple (W–P). Plants were separately cut into leaf (L) and flower (F) parts. Changes in internal organelle morphology of trophozoites following exposure to crude extracts were assessed using transmission electron microscopy (TEM). In subsequent experiments, efficacy of the most active essential oils from crude extracts [half maximal inhibitory concentrations (IC₅₀) ≤ 100 μg/mL] against G. duodenalis trophozoites was tested. In vitro anti-Giardia assays using essential oils were performed in the same way as those performed using crude extracts.

Results

LW–P and FP extracts showed high activity (IC₅₀ ≤ 100 μg/mL) against G. duodenalis trophozoites, with IC₅₀ ± SD values of 45.67 ± 0.51 and 96.00 ± 0.46 μg/mL, respectively. In subsequent experiments, IC₅₀ ± SD values of LW–P and FP essential oils were 35.00 ± 0.50 and 89.33 ± 0.41 μg/mL, respectively. TEM revealed the degeneration of flagella and ventral discs of G. duodenalis trophozoites following exposure to crude extracts.

Conclusion

Crude LW–P and FP extracts of A. conyzoides showed the highest activity against G. duodenalis. Exposure to crude extract induced changes in the flagella and ventral discs of G. duodenalis trophozoites, which play important roles in attachment to the surface of mucosal cells. Our results suggest that the tested extracts warrant further research in terms of their efficacy and safety as giardiasis treatment.

Epidemiology of human giardiasis in Romania: A 14 years survey

Giardia spp. is the most common intestinal protozoan (causing gastrointestinal illness) and the most frequent cause of parasitic gastroenteritis in humans and animals worldwide. The aim of this study was to highlight new data in a specific area regarding clinical presentation and epidemiological prevalence over a long period of time. Patients (a total number of 54,623 patients) admitted in a tertiary center for infectious diseases serving a county for a period of 14 years were tested for infection with Giardia. Positive cases were recorded through analyzing the clinical complaints, the month of incidence and the demographic area from which the patients came from. Longitudinal trends have been evaluated. The incidence of giardiasis among the tested patients was 4.47%. A decreasing trend was observed regarding the annual incidence. Patients between the ages of 15 and 44 presented most commonly giardiasis, especially those from urban areas and women. The most common symptoms are loss of appetite (71.24%) and abdominal pain (69.07%). The highest monthly incidence was quoted in July (10.65%), August (10.49%) and June (10.20%). This epidemiological study allows a better knowledge of the infection with Giardia spp. It gives the long-term changes in demographic characteristics of the infected patients in a specific area and the monthly incidence.

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

Giardia duodenalis is one of the most common causes of diarrhea in humans with about 250–300 million cases per year. It is considered to be a species complex comprising of eight genetic assemblages (A to H), with assemblages A and B being the major causes of human infections. In this study we carried out genotypic characterization of G. duodenalis isolates detected in asymptomatic school-going children aged 3–16 years. Between May and September 2017, a total of 329 fecal samples were collected from school-going children from Chawama compound of Lusaka City and were screened for Giardia by microscopic examination. All microscopically positive fecal samples were analyzed by semi-nested polymerase chain reaction (PCR) targeting the glutamate dehydrogenase (gdh) gene. Genotyping of amplified PCR products was conducted by restriction fragment length polymorphism (RFLP) and DNA sequence analysis. Microscopically, Giardia was found in 10% (33/329) of fecal samples. The PCR-RFLP analysis of the gdh gene revealed assemblages A and B in 27.3% (9/33) and 72.7% (24/33), respectively. Furthermore, analysis with restriction enzymes identified sub-assemblages AII (27.3%, 9/33), BIII (12.1%, 4/33), BIV (51.5%, 17/33) and mixed infections of BIII and BIV (9.1%, 3/33). Phylogenetic analysis showed the clustering of 27.6% (8/29) and 72.4% (21/29) of Zambian Giardia gdh gene sequences into assemblages A and B, respectively. This study has revealed the presence of both assemblage A and B and that spread of G. duodenalis in school-going children appears to be mostly through anthroponotic transmission. To our knowledge, this is the first report of genotypic characterization of G. duodenalis identified in Zambia.

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Giardia duodenalis infection observed in asymptomatic children

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First report of genotypes circulating in Zambia

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Presence of sub-assemblages AII, BIII and BIV

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Co-infection with sub-assemblages BIII and BIV reported

Prevalence and Genotype Distribution of Giardia duodenalis in Rabbits in Shandong Province, Eastern China

Giardia duodenalis is a zoonotic enteric parasite that can infect humans and a number of animal species including rabbits with a worldwide distribution. Infection with G. duodenalis can cause serious public health problems and significant economic losses to animal husbandry. So accurate understanding of the prevalence and genotype distribution of G. duodenalis in rabbits is necessary. In the present study, a total of 616 fecal samples were collected from rabbits in Shandong province, eastern China, and examined in G. duodenalis prevalence and genotypes by nested PCR amplification of β-giardin (bg), glutamate dehydrogenase (gdh), and triosephosphate isomerase (tpi) gene loci of G. duodenalis. Sixty-nine (11.2%) of the examined rabbit fecal samples were G. duodenalis-positive. Of them, the prevalence of G. duodenalis is 8.4% (41/490) in Rizhao city and 22.2% (28/126) in Weihai city. Breeds, region, and feeding modes were highly correlated with G. duodenalis infection in rabbits. Moreover, three genotypes (assemblages A, B, and E) were identified in rabbits at three gene loci, and the assemblage E was the dominant genotype, while the assemblage A was reported in rabbits in China for the first time. It is noticeable that two rabbits were found to be infected with two different G. duodenalis assemblages (assemblages A and E, assemblages B and E, respectively). These findings enrich the genotype distribution of G. duodenalis in rabbits and provide baseline data for preventing and controlling G. duodenalis infection in rabbits in eastern China.

Multilocus genotyping of Giardia duodenalis in Southwestern Iran. A community survey

Giardia duodenalis is one of the main enteric pathogens associated with diarrheal disease. In developing countries, giardiasis is a major public health concern, particularly in children under five years of age. This study aimed to evaluate the occurrence and genetic diversity of G. duodenalis causing human infections in Shushtar County, Southwestern Iran. Individual faecal specimens were collected from 1,163 individuals (male/female ratio: 0.9; age range 2-75 years) with (n = 258) and without (n = 905) gastrointestinal symptoms living in rural and urban settings during the period 2017-2018. Conventional (sucrose flotation and microscopy) methods were used for the initial detection of G. duodenalis cysts in faecal specimens. Microscopy-positive samples were confirmed by PCR amplification and sequencing of the small subunit rRNA (ssu rRNA) gene of the parasite. A multilocus genotyping (MLG) scheme targeting the triose phosphate isomerase (tpi), the glutamate dehydrogenase (gdh), and the beta-giardin (bg) genes was used for genotyping purposes. Giardia duodenalis cysts were detected in 7.7% (90/1,163) of samples by microscopy, of which 82 were confirmed by ssu-PCR. Successful amplification and sequencing results were obtained for 23.2% (19/82), 9.8% (8/82), and 8.5% (7/82) of the confirmed samples at the tpi, gdh, and bg loci, respectively. MLG data for the three loci were available for two samples only. Out of the 24 samples genotyped at any loci, 50% (12/24) were identified as assemblage A and the remaining half as assemblage B. Overall, AII was the most prevalent sub-assemblage detected (41.7%, 10/24), followed by BIII (25.0%, 6/24), discordant BIII/BIV (5/24) or AII/AIII (2/24) sequences, and BIV (1/24). No significant correlation was demonstrated between a given assemblage/sub-assemblage and the occurrence of clinical symptoms. No genotypes adapted to animal hosts other than humans (e.g. assemblages C-F) were found circulating in the investigated human population, suggesting that transmission of human giardiasis in this Iranian region is primarily of anthroponotic nature. Further molecular-based studies are needed to confirm and expand these results, and to ascertain the presence and public health relevance of the parasite in environmental (e.g. drinking water) samples.

DNA topoisomerase IIIβ promotes cyst generation by inducing cyst wall protein gene expression in Giardia lamblia

Giardia lamblia causes waterborne diarrhoea by transmission of infective cysts. Three cyst wall proteins are highly expressed in a concerted manner during encystation of trophozoites into cysts. However, their gene regulatory mechanism is still largely unknown. DNA topoisomerases control topological homeostasis of genomic DNA during replication, transcription and chromosome segregation. They are involved in a variety of cellular processes including cell cycle, cell proliferation and differentiation, so they may be valuable drug targets. Giardia lamblia possesses a type IA DNA topoisomerase (TOP3β) with similarity to the mammalian topoisomerase IIIβ. We found that TOP3β was upregulated during encystation and it possessed DNA-binding and cleavage activity. TOP3β can bind to the cwp promoters in vivo using norfloxacin-mediated topoisomerase immunoprecipitation assays. We also found TOP3β can interact with MYB2, a transcription factor involved in the coordinate expression of cwp1-3 genes during encystation. Interestingly, overexpression of TOP3β increased expression of cwp1-3 and myb2 genes and cyst formation. Microarray analysis confirmed upregulation of cwp1-3 and myb2 genes by TOP3β. Mutation of the catalytically important Tyr residue, deletion of C-terminal zinc ribbon domain or further deletion of partial catalytic core domain reduced the levels of cleavage activity, cwp1-3 and myb2 gene expression, and cyst formation. Interestingly, some of these mutant proteins were mis-localized to cytoplasm. Using a CRISPR/Cas9 system for targeted disruption of top3β gene, we found a significant decrease in cwp1-3 and myb2 gene expression and cyst number. Our results suggest that TOP3β may be functionally conserved, and involved in inducing Giardia cyst formation.

Recent advances in functional research in Giardia intestinalis

This review considers current advances in tools to investigate the functional biology of Giardia, it's coding and non-coding genes, features and cellular and molecular biology. We consider major gaps in current knowledge of the parasite and discuss the present state-of-the-art in its in vivo and in vitro cultivation. Advances in in silico tools, including for the modelling non-coding RNAs and genomic elements, as well as detailed exploration of coding genes through inferred homology to model organisms, have provided significant, primary level insight. Improved methods to model the three-dimensional structure of proteins offer new insights into their function, and binding interactions with ligands, other proteins or precursor drugs, and offer substantial opportunities to prioritise proteins for further study and experimentation. These approaches can be supplemented by the growing and highly accessible arsenal of systems-based methods now being applied to Giardia, led by genomic, transcriptomic and proteomic methods, but rapidly incorporating advanced tools for detection of real-time transcription, evaluation of chromatin states and direct measurement of macromolecular complexes. Methods to directly interrogate and perturb gene function have made major leaps in recent years, with CRISPr-interference now available. These approaches, coupled with protein over-expression, fluorescent labelling and in vitro and in vivo imaging, are set to revolutionize the field and herald an exciting time during which the field may finally realise Giardia's long proposed potential as a model parasite and eukaryote.

Occurrence and multilocus genotyping of Giardia duodenalis in captive non-human primates from 12 zoos in China

Giardia duodenalis is a common enteric protozoan that infects a range of hosts including humans and other mammals. Multilocus genotyping of G. duodenalis in captive non-human primates (NHPs) from zoos in China is limited. In this study, we evaluated 302 NHP fecal samples collected from 32 different NHP species. The primates were from 12 zoos distributed across eight provinces and two municipalities (Chongqing and Beijing) of China. The overall infection rate was 8.3% (25/302). The six G. duodenalis-positive zoos and their infection rates were: Suzhou Zoo (40.0%, 4/10), Yangzhou Zoo (22.2%, 2/9), Dalian Zoo (16.7%, 4/24), Chengdu Zoo (12.8%, 6/47), Guiyang Forest Wildlife Zoo (12.1%, 7/58), and Changsha Zoo (4.7%, 2/43). Molecular analysis of three loci, beta-giardin (bg), triose phosphate isomerase (tpi), and glutamate dehydrogenase (gdh), showed high genetic heterogeneity, and seven novel subtypes (BIII-1, MB10-1, WB8-1, B14-1, MB9-1, DN7-1, and BIV-1) were detected within assemblage B. Additional analysis revealed 12 different assemblage B multilocus genotypes (MLGs), one known MLG and 11 novel MLGs. Based on phylogenetic analysis, 12 assemblage B MLGs formed two main clades, MLG-SW (10-12, 18) and MLG-SW (13, 14, 16, 17), the other four MLG-SW (15, 19, 20, 21) were scattered throughout the phylogenetic tree in this study. Using multilocus genotyping, this study expands our understanding of the occurrence of Giardia infection and genetic variation in Giardia in captive non-human primates from zoos in China.

5-Nitroimidazole refractory giardiasis is common in Matanzas, Cuba and effectively treated by secnidazole plus high-dose mebendazole or quinacrine: a prospective observational cohort study

OBJECTIVE

To evaluate the effectiveness and tolerability of secnidazole combined with high-dose mebendazole for treatment of 5-nitroimidazole-resistant giardiasis.

METHOD

Adults with microscopically verified Giardia intestinalis monoinfection attending a secondary level hospital in Matanzas City, Cuba were prospectively included in a cohort. A recently introduced treatment ladder consisting of metronidazole as first-line treatment, followed by secnidazole, tinidazole, secnidazole plus mebendazole and quinacrine as second-to fifth-line treatments, respectively, was used. Adverse events and treatment success were determined by questioning and microscopy on concentrated stool samples, respectively on days 3, 5 and 7 after the end of treatment. If G. intestinalis was detected on day 3, 5 or 7, then the infection was classified as refractory and no further microscopy was performed.

RESULTS

A total of 456 individuals were included. Metronidazole, 500 mg three times daily for 5 days, cured 248/456 (54%) patients. A single 2-g secnidazole dose as second-line treatment cured 50/208 (24%) patients. A single 2-g tinidazole dose as third-line treatment cured 43/158 (27%) patients. Three rounds of 5-nitroimidazole therapy therefore cured 341/456 (75%) patients. Secnidazole plus mebendazole (200 mg every 8 hours for 3 days) cured 100/115 (87%) of nitroimidazole refractory infections. Quinacrine cured the remaining 15 patients. All treatments were well tolerated.

CONCLUSIONS

5-Nitroimidazole refractory giardiasis was common, indicating that an alternative first-line treatment may be needed. Retreatment of metronidazole refractory giardiasis with an alternative 5-nitroimidazole was suboptimal, indicating cross-resistance. Mebendazole plus secnidazole were well tolerated and effective for the treatment of 5-nitroimidazole refractory G. intestinalis infection in this setting.

RORγt+ Treg to Th17 ratios correlate with susceptibility to Giardia infection

Infections with Giardia are among the most common causes of food and water-borne diarrheal disease worldwide. Here, we investigated Th17, Treg and IgA responses, and alterations in gut microbiota in two mouse lines with varying susceptibility to Giardia muris infection. Infected BALB/c mice shed significantly more cysts compared with C57BL/6 mice. Impaired control of infection in BALB/c mice was associated with lower Th17 activity and lower IgA levels compared with C57BL/6 mice. The limited metabolic activity, proliferation and cytokine production of Th17 cells in BALB/c mice was associated with higher proportions of intestinal Foxp3⁺RORγt⁺ regulatory T cells and BALB/c mice developed increased RORγt⁺ Treg:Th17 ratios in response to G. muris infection. Furthermore, G. muris colonization led to a significantly reduced evenness in the gut microbial communities of BALB/c mice. Our data indicate that differential susceptibility to Giardia infections may be related to RORγt⁺ Treg controlling Th17 activity and that changes in the microbiota composition upon Giardia infection partially depend on the host background.

Identification of the NADP+ Structural Binding Site and Coenzyme Effect on the Fused G6PD::6PGL Protein from Giardia lamblia

Giardia lambia is a flagellated protozoan parasite that lives in the small intestine and is the causal agent of giardiasis. It has been reported that G. lamblia exhibits glucose-6-phosphate dehydrogenase (G6PD), the first enzyme in the pentose phosphate pathway (PPP). Our group work demonstrated that the g6pd and 6pgl genes are present in the open frame that gives rise to the fused G6PD::6PGL protein; where the G6PD region is similar to the 3D structure of G6PD in Homo sapiens. The objective of the present work was to show the presence of the structural NADP⁺ binding site on the fused G6PD::6PGL protein and evaluate the effect of the NADP⁺ molecule on protein stability using biochemical and computational analysis. A protective effect was observed on the thermal inactivation, thermal stability, and trypsin digestions assays when the protein was incubated with NADP⁺. By molecular docking, we determined the possible structural-NADP⁺ binding site, which is located between the Rossmann fold of G6PD and 6PGL. Finally, molecular dynamic (MD) simulation was used to test the stability of this complex; it was determined that the presence of both NADP⁺ structural and cofactor increased the stability of the enzyme, which is in agreement with our experimental results.

Exosome Biogenesis in the Protozoa Parasite Giardia lamblia: A Model of Reduced Interorganellar Crosstalk

: Extracellular vesicles (EVs) facilitate intercellular communication and are considered a promising therapeutic tool for the treatment of infectious diseases. These vesicles involve microvesicles (MVs) and exosomes and selectively transfer proteins, lipids, mRNAs, and microRNAs from one cell to another. While MVs are formed by extrusion of the plasma membrane, exosomes are a population of vesicles of endosomal origin that are stored inside the multivesicular bodies (MVBs) as intraluminal vesicles (ILVs) and are released when the MVBs fuse with the plasma membrane. Biogenesis of exosomes may be driven by the endosomal sorting complex required for transport (ESCRT) machinery or may be ESCRT independent, and it is still debated whether these are entirely separate pathways. In this manuscript, we report that the protozoan parasite, Giardia lamblia, although lacking a classical endo-lysosomal pathway, is able to produce and release exosome-like vesicles (ElV). By using a combination of biochemical and cell biology analyses, we found that the ElVs have the same size, shape, and protein and lipid composition as exosomes described for other eukaryotic cells. Moreover, we established that some endosome/lysosome peripheral vacuoles (PVs) contain ILV during the stationary phase. Our results indicate that ILV formation and ElV release depend on the ESCRT-associated AAA+-ATPase Vps4a, Rab11, and ceramide in this parasite. Interestingly, EIV biogenesis and release seems to occur in Giardia despite the fact that this parasite has lost most of the ESCRT machinery components during evolution and is unable to produce ceramide de novo. The differences in protozoa parasite EV composition, origin, and release may reveal functional and structural properties of EVs and, thus, may provide information on cell-to-cell communication and on survival mechanisms.

Transcriptomic and proteomic analyses of Giardia intestinalis: Intestinal epithelial cell interactions

Giardia intestinalis is a unicellular protozoan parasite that infects the small intestines of humans and animals. Giardiasis, the disease caused by the parasite, occurs globally across socioeconomic boundaries but is mainly endemic in developing countries and particularly within young children, where pronounced effects manifests in a failure to thrive condition. The molecular pathogenesis of Giardia has been studied using in vitro models of human and rat intestinal epithelial cells (IECs) and parasites from the two major human genotypes or assemblages (A and B). High-quality, genome sequencing of representative isolates from assemblages A (WB) and B (GS) has enabled exploration of these host-parasite models using 'omics' technologies, allowing deep and quantitative analyses of global gene expression changes in IECs and parasites during their interactions, cross-talk and competition. These include a major up-regulation of immune-related genes in the IECs early after the start of interactions, as well as competition between host cells and parasites for nutrients like sugars, amino acids and lipids, which is also reflected in their secretome interactions. Unique parasite proteins dominate these interactions, with many major up-regulated genes being either hypothetical proteins or members of Giardia-specific gene families like the high-cysteine-rich membrane proteins (HCMPs), variable surface proteins (VSPs), alpha-giardins and cysteine proteases. Furthermore, these proteins also dominate in the secretomes, suggesting that they are important virulence factors in Giardia and crucial molecular effectors at the host-parasite interface.

Host factors associated with Giardia duodenalis infection in dogs across multiple diagnostic tests

Background

The aim of this study was to assess potential associations between Giardia duodenalis infection in dogs, as determined by three diagnostic tests, and dog’s group of origin, fecal consistency, age, sex, neuter status, and co-infections with other gastrointestinal parasites.

Methods

Fecal samples from 1291 dogs from four groups (household, shelter, hunting and clinical dogs) were tested with qPCR, rapid enzyme immunochromatographic assay (IDEXX SNAP^®Giardia), and direct immunofluorescence (DFA, Merifluor) for presence of G. duodenalis. Moreover, fecal samples were tested with centrifugation sedimentation flotation (CSF) coproscopical analysis for presence of gastrointestinal parasites. Associations were expressed as odds ratios (ORs).

Results

Several significant associations were found, of which a few were consistent for all three tests and Giardia positivity in general (positive with at least one of these tests). Dogs older than one year were significantly less likely to test positive for Giardia than younger dogs. Group-housed dogs, especially hunting dogs, were significantly more likely to test positive for Giardia compared to household and clinical dogs. A consistently significant association with Trichuris appeared to be driven by the high prevalence in hunting dogs. Although there was no significant association between loose stool and Giardia infection in the overall population, household dogs were significantly more likely to test Giardia-positive when having loose stool. Overall, Giardia-positive dogs with loose stool shed significantly more cysts, both determined semi-quantitatively with CSF and quantitatively by qPCR, than positive dogs with no loose stool. When other gastrointestinal parasites were present, significantly fewer cysts were detected with CSF, but this was not confirmed with qPCR.

Conclusion

Giardia is the most common gastrointestinal parasite in Dutch dogs, except for hunting dogs, in which Trichuris and strongyle-type eggs (hookworms) prevailed. Giardia infection was not significantly associated with loose stool, except for household dogs. Young dogs and group-housed dogs were significantly more often Giardia-positive. These associations were consistent across diagnostic tests. Young dogs, clinical dogs and dogs with loose stool shed Giardia cysts in the highest numbers. If another gastrointestinal parasite was present lower numbers of cysts were observed by microscope (CSF), but not with a molecular method (qPCR).

Animal Models of Undernutrition and Enteropathy as Tools for Assessment of Nutritional Intervention

: Undernutrition is a major public health problem leading to 1 in 5 of all deaths in children under 5 years. Undernutrition leads to growth stunting and/or wasting and is often associated with environmental enteric dysfunction (EED). EED mechanisms leading to growth failure include intestinal hyperpermeability, villus blunting, malabsorption and gut inflammation. As non-invasive methods for investigating gut function in undernourished children are limited, pre-clinical models are relevant to elucidating the pathophysiological processes involved in undernutrition and EED, and to identifying novel therapeutic strategies. In many published models, undernutrition was induced using protein or micronutrient deficient diets, but these experimental models were not associated with EED. Enteropathy models mainly used gastrointestinal injury triggers. These models are presented in this review. We found only a few studies investigating the combination of undernutrition and enteropathy. This highlights the need for further developments to establish an experimental model reproducing the impact of undernutrition and enteropathy on growth, intestinal hyperpermeability and inflammation, that could be suitable for preclinical evaluation of innovative therapeutic intervention.

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.

Gastrointestinal motility and absorptive disorders in patients with inflammatory bowel diseases: Prevalence, diagnosis and treatment

Inflammatory bowel diseases (IBD), Crohn`s disease and ulcerative colitis, are chronic conditions associated with high morbidity and healthcare costs. The natural history of IBD is variable and marked by alternating periods of flare and remission. Even though the use of newer therapeutic targets has been associated with higher rates of mucosal healing, a great proportion of IBD patients remain symptomatic despite effective control of inflammation. These symptoms may include but not limited to abdominal pain, dyspepsia, diarrhea, urgency, fecal incontinence, constipation or bloating. In this setting, commonly there is an overlap with gastrointestinal (GI) motility and absorptive disorders. Early recognition of these conditions greatly improves patient care and may decrease the risk of mistreatment. Therefore, in this review we describe the prevalence, diagnosis and treatment of GI motility and absorptive disorders that commonly affect patients with IBD.

Molecular epidemiology of giardiasis from a veterinary perspective

A total of eight Giardia species are accepted. These include: Giardia duodenalis (syn. Giardia intestinalis and Giardia lamblia), which infects humans and animals, Giardia agilis, Giardia ardeae, Giardia psittaci, Giardia muris, Giardia microti, Giardia peramelis and G. cricetidarum, which infect non-human hosts including amphibians, birds, rodents and marsupials. Giardia duodenalis is a species complex consisting of eight assemblages (A-H), with assemblages A and B the dominant assemblages in humans. Molecular studies to date on the zoonotic potential of Giardia in animals are problematic and are hampered by lack of concordance between loci. Livestock (cattle, sheep, goats and pigs) are predominantly infected with G. duodenalis assemblage E, which has recently been shown to be zoonotic, followed by assemblage A. In cats and dogs, assemblages A, B, C, D and F are commonly reported but relatively few studies have conducted molecular typing of humans and their pets and the results are contradictory with some studies support zoonotic transmission but the majority of studies suggesting separate transmission cycles. Giardia also infects a broad range of wildlife hosts and although much less well studied, host-adapted species as well as G. duodenalis assemblages (A-H) have been identified. Fish and other aquatic wildlife represent a source of infection for humans with Giardia via water contamination and/or consumption of undercooked fish and interestingly, assemblage B and A predominated in the two molecular studies conducted to date. Our current knowledge of the transmission dynamics of Giardia is still poor and the development of more discriminatory typing tools such as whole genome sequencing (WGS) of Giardia isolates is therefore essential.

Multilocus genotyping of Giardia duodenalis isolated from patients in Egypt

Human giardiasis is a common waterborne/foodborne parasitic disease worldwide, especially in developing countries. Prevalence and molecular identity of Giardia parasites are largely controversial. The present study was conducted to determine the occurrence of Giardia parasites and the genetic profile of circulating assemblage(s) in patients attended the outpatient clinic at Kafrelsheikh University hospital, Kafr El Sheikh Province, Egypt. A total of 318 patients, of different age and sex, referred to the clinic were subjected to fecal examination. Microscopic results revealed that 181/318 (56.9%) were positive for Giardia parasites. Multilocus genotyping by PCR/sequencing of beta-giardin (bg), triose phosphate isomerase (tpi), and glutamate dehydrogenase (gdh) genes of representative number of positive samples (65) revealed that assemblages A, B and mixed infections (A + B) occurred in 26/65 (40.0%), 32/65 (49.2%) and 10.8% (7/65) of the analyzed isolates, respectively. MLGs analysis indicated that assemblage A sequences clustered in two novel types of AII sub-assemblage. In assemblage B sequences, BIII was the predominant (22/23, 95.7%) sub-assemblage compared to BIV (1/23, 4.3%). Collectively, assemblage B MLGs displayed greater levels of genetic diversity compared to assemblage A. Our data indicate that assemblages A and B of G. duodenalis circulate in humans at Kafr El Sheikh Province, Egypt, and that high genetic diversity exists at the assemblage and/or sub-assemblage levels.

Prevalence and Zoonotic Potential of Giardia intestinalis in Dogs of the Central Region of Mexico

Simple Summary

Giardia intestinalis is a parasite that causes disease in different species, including humans and dogs. It is prevalent worldwide and disease in humans is mainly the consequence of poor hygiene habits and close interaction with infected animals. Because cross infections can be seen between humans and dogs, it is critically important to know which genotypes affect each species, useful for determining if dogs are the source of infection for humans in a particular setting. The aim of this study was to determine if dogs in the central region of Mexico play a significant role in human infections from this same area. Sampling of dog feces was performed in animal shelters, dog breeding establishments, animal control facilities and homes. Direct coproparasitoscopic diagnosis was performed; PCR and RFLP analysis were used to obtain genotypes. Results from all of the positive samples show that the genotypes from dogs matched G. intestinalis assemblage A, which does cause infection and disease in humans. These findings highlight the fact that infection in dogs by G. intestinalis needs to be controlled in order to stop transmission amongst the dog population, and, most importantly, to prevent human contagion.

Abstract

Giardia intestinalis is a protozoan of worldwide distribution capable of infecting a large number of species, including humans and domestic animals. Dogs represent a risk to public health due to cross-infections by the zoonotic assemblages. However, there is little information concerning the prevalence and frequency of this parasite and its assemblages in dogs of the central region of Mexico, thus this study aimed to contribute to this matter. A total of 402 feces samples from dogs of different settings (shelter, breeding establishments, domestic and stray) were obtained and direct coproparasitoscopic examination by flotation revealed a prevalence of 25%. PCR was performed for amplification of the β-Giardin gene, to which 24 samples were positive. Assemblages were obtained through RFLP analysis, using enzymes Hae III to obtain the main genotypes (A–G), and Hha I to subtype assemblage A. All 24 samples were genotyped as assemblage A, with 83% as AI and 17% as AII. Thus, these findings confirm that dogs in the central region of Mexico are a risk for zoonotic transmission of this parasite, emphasizing the importance of a much needed control of the disease in this species.

Molecular Genotyping of Giardia duodenalis in Humans in the Andimeshk County, Southwestern Iran

INTRODUCTION

Giardia duodenalis, one of the most common intestinal protozoa, infects a wide range of vertebrates, including humans and animals.

MATERIALS AND METHODS

In this study, 84 Giardia duodenalis positive stool samples were collected from 3580 patients attending the Imam Ali Hospital and two public health centers in Andimeshk County, southwestern Iran. Stool samples were examined initially by microscopy, and then G. duodenalis was confirmed by SSU rRNA gene and genotypes were determined by amplification of the gdh and β-giardin genes.

RESULTS

The SSU rRNA, gdh, and β-giardin genes were successfully amplified in 89.3%, 58.3%, and 51.2% samples, respectively. Of the positive samples for gdh and β-giardin, 40 isolates were successfully sequenced. Twenty-three isolates belonged to assemblage A, sub-assemblage AII, and 17 belonged to assemblage B. Of the 24 successfully amplified asymptomatic cases, 12 belonged to assemblage A and 12 belonged to assemblage B.

CONCLUSION

The current study found that 64.3% of the patients were asymptomatic. From an epidemiological point of view, the high percentage of asymptomatic patients is important because of their role in the transmission of Giardia. The predominant assemblage was assemblage A, sub-assemblage AII. In general, therefore, it seems that most infections are probably transmitted by anthroponotic pathways in the region.

Giardia intestinalis cystatin is a potent inhibitor of papain, parasite cysteine proteases and, to a lesser extent, human cathepsin B

Cystatins are important regulators of papain-like cysteine proteases. In the protozoan parasite Giardia intestinalis, papain-like cysteine proteases play an essential role in the parasite's biology and pathogenicity. Here, we characterized a cysteine protease inhibitor of G. intestinalis that belongs to type-I-cystatins. The parasite cystatin is shown to be a strong inhibitor of papain (K_i  ≈ 0.3 nm) and three parasite cysteine proteases (CP14019, CP16160 and CP16779, K_i  ≈ 0.9-5.8 nm), but a weaker inhibitor of human cathepsin B (K_i  ≈ 79.9 nm). The protein localizes mainly in the cytoplasm. Together, these data suggest that cystatin of G. intestinalis plays a role in the regulation of cysteine protease activities in the parasite and, possibly, in the interaction with the host.

Occurrence and multilocus genotyping of Giardia duodenalis in black-boned sheep and goats in southwestern China

BACKGROUND

Giardia duodenalis is an important intestinal protozoan infecting both humans and animals, causing significant public health concern and immeasurable economic losses to animal husbandry. Sheep and goats have been reported as common reservoirs of G. duodenalis, but only a limited amount of information is available for native breeds of these small ruminants in China. The present study investigated the prevalence and multilocus genotypes of G. duodenalis in black-boned sheep and goats, two important native breeds in Yunnan Province, southwestern China.

METHODS

Fecal samples were collected from 336 black-boned goats and 325 black-boned sheep from five counties (Meishui, Shanshu, Shilin, Yongsheng and Nanping) of Yunnan Province and the genomic DNA was extracted from these feces. The prevalence of G. duodenalis was determined by the nested PCR targeting the β-giardin (bg) gene. The assemblages and multilocus genotypes (MLGs) were investigated based on analyses of three genetic loci, i.e. bg, glutamate dehydrogenase (gdh) and triosephosphate isomerase (tpi).

RESULTS

Giardia duodenalis infection was detected in both black-boned sheep and goats, and the prevalence of G. duodenalis in black-boned sheep (21.8%, 71/325) was significantly higher (χ² = 36.63, df = 1, P < 0.001) than that in black-boned goats (4.8%, 16/336). Significant differences in prevalence were also observed in goats and sheep from different counties (χ² = 39.83, df = 4, P < 0.001) and age groups (χ² = 97.33, df = 3, P < 0.001). Zoonotic assemblage A and animal-specific assemblage E were identified in both black-boned sheep and goats with the latter as the predominant assemblage. Based on sequences obtained from the three genetic loci (bg, gdh and tpi), 16 MLGs were obtained in black-boned sheep and goats, including 15 MLGs in assemblage E and one MLG in assemblage A.

CONCLUSIONS

Our results not only extended the host range of G. duodenalis, but also revealed high genetic variations in G. duodenalis assemblages. The findings of the present study also provide baseline data for preventing and controlling G. duodenalis infection in black-boned sheep and goats in Yunnan Province.

Development of CRISPR/Cas9-mediated gene disruption systems in Giardia lamblia

Giardia lamblia becomes dormant by differentiation into a water-resistant cyst that can infect a new host. Synthesis of three cyst wall proteins (CWPs) is the fundamental feature of this differentiation. Myeloid leukemia factor (MLF) proteins are involved in cell differentiation, and tumorigenesis in mammals, but little is known about its role in protozoan parasites. We developed a CRISPR/Cas9 system to understand the role of MLF in Giardia. Due to the tetraploid genome in two nuclei of Giardia, it could be hard to disrupt a gene completely in Giardia. We only generated knockdown but not knockout mutants. We found that knockdown of the mlf gene resulted in a significant decrease of cwp gene expression and cyst formation, suggesting a positive role of MLF in encystation. We further used mlf as a model gene to improve the system. The addition of an inhibitor for NHEJ, Scr7, or combining all cassettes for gRNA and Cas9 expression into one plasmid resulted in improved gene disruption efficiencies and a significant decrease in cwp gene expression. Our results provide insights into a positive role of MLF in inducing Giardia differentiation and a useful tool for studies in Giardia.

Gastrointestinal Malabsorption of Thyroxine

Levothyroxine, a largely prescribed drug with a narrow therapeutic index, is often a lifelong treatment. The therapeutic efficacy of T4 may be marred by behavioral, pharmacologic, and pathologic issues acting as interfering factors. Despite a continuous search for an optimal T4 treatment, a significant number of patients fail to show a complete chemical and/or clinical response to this reference dose of T4. Gastrointestinal malabsorption of oral T4 represents an emerging cause of refractory hypothyroidism and may be more frequent than previously reputed. In this review, we examine the pharmacologic features of T4 preparations and their linkage with the intestinal absorption of the hormone. We have stressed the major biochemical and pharmacologic characteristics of T4 and its interaction with the putative transporter at the intestinal level. We have examined the interfering role of nutrients, foods, and drugs on T4 absorption at the gastric and intestinal levels. The impact of gastrointestinal disorders on T4 treatment efficacy has been also analyzed, in keeping with the site of action and the interfering mechanisms. Based on the evidence obtained from the literature, we also propose a schematic diagnostic workup for the most frequent and often hidden gastrointestinal diseases impairing T4 absorption.

Helicobacter pylori and enteric parasites co-infection among diarrheic and non-diarrheic Egyptian children: seasonality, estimated risks, and predictive factors

Helicobacter pylori (H. pylori) and intestinal parasites are known for their high prevalence in children. Both of them infect the gastrointestinal tract with overlapping clinical pictures. This study was conducted to determine H. pylori prevalence and its association with intestinal parasites in children, moreover to estimate risk and predictive factors for their detection in stool samples. Single fecal samples were collected from 226 Egyptian pediatric patients (125 diarrheic and 101 non-diarrheic) attending gastroenterology outpatients' clinics, from February 2016 to June 2017. All stool specimens were microscopically examined to search for ova and parasites. Copro-DNAs detection of H. pylori and Cryptosporidium were performed using nested-PCR assays. H. pylori was detected molecularly in 36.8% of the total study population, with a higher prevalence in diarrheic than in non-diarrheic children. Intestinal parasites were detected in 27.4% of the total study populations, of these, 43.9% had co-existence with H. pylori colonized patients and was significantly associated with Cryptosporidium spp. and G. intestinalis. Estimated risk of the presence of H. pylori was in January. Our data provide a better understanding of the epidemiology of H. pylori infection when associated with intestinal parasites. H. pylori co-existence with G. intestinals and Cryptosporidium may suggest the association of H. pylori infection with markers of fecal exposure. Whether H. pylori provides favorable conditions for intestinal parasitosis or vice versa, still further investigations are needed with an emphasis upon determining correlation with gut microbiomes.

Pre-ozonation of source water: Assessment of efficacy against Giardia duodenalis cysts and effects on natural organic matter

The protozoan Giardia duodenalis is one of the parasites of primary concern in drinking water treatment plants, due to its resistance to chlorination. Another matter of concern regarding chlorination of drinking water is the formation of disinfection by-products in the presence of precursors such as natural organic matter (NOM). In this study, the effects of ozonation (5 mg L^-1) on G. duodenalis cysts in raw surface water from a drinking water treatment plant were evaluated, and the presence and alteration of NOM were assessed, as an indicative of the potential to prevent total organic halogen (TOX) formation during post-chlorination. Following ozone treatment, the presence of damaged cysts was observed by direct immunofluorescence assay (IFA) and confirmed by the molecular approach propidium monoazide-polymerase chain reaction (PMA-PCR). Using an animal model, analysis of the intestinal tissues revealed that 80% of the animals inoculated with ozonated water were positive for trophozoites. This study shows that analysis of intestinal fragments is imperative to accurately assess animal infection following inoculation of treated cysts. More importantly, considering the low infective dose of Giardia cysts in susceptible hosts, an ozone dosage usually applied in drinking water treatment plants did not completely inactivate G. duodenalis cysts in surface water. Nonetheless, the results suggest that competitive reactions with NOM have occurred, and the applied ozone dosage has proven useful to remove NOM reactivity, and thus prevent halogenated DBP formation during post-chlorination.

Giardia: an under-reported foodborne parasite

Foodborne zoonotic pathogens are a serious public health issue and result in significant global economic losses. Despite their importance to public health, epidemiological data on foodborne diseases including giardiasis caused by the enteric parasite, Giardia duodenalis, are lacking. This parasite is estimated to cause ∼28.2 million cases of diarrhoea each year due to contamination of food, but very few foodborne outbreaks have been documented due to the limitations of current detection as well as surveillance methods. The current method for the recovery of Giardia cysts from food matrices using immunomagnetic separation requires further standardisation and cost reduction before it can be widely used. It also should incorporate downstream molecular procedures for genotyping, and traceback and viability analyses. Foodborne giardiasis can be potentially controlled through improvements in national disease surveillance systems and the establishment of Hazard Analysis and Critical Control Point interventions across the food chain. Studies are needed to assess the true prevalence and public health impact of foodborne giardiasis.

Robust and stable transcriptional repression in Giardia using CRISPRi

Giardia lamblia is a binucleate protistan parasite causing significant diarrheal disease worldwide. An inability to target Cas9 to both nuclei, combined with the lack of nonhomologous end joining and markers for positive selection, has stalled the adaptation of CRISPR/Cas9-mediated genetic tools for this widespread parasite. CRISPR interference (CRISPRi) is a modification of the CRISPR/Cas9 system that directs catalytically inactive Cas9 (dCas9) to target loci for stable transcriptional repression. Using a Giardia nuclear localization signal to target dCas9 to both nuclei, we developed efficient and stable CRISPRi-mediated transcriptional repression of exogenous and endogenous genes in Giardia. Specifically, CRISPRi knockdown of kinesin-2a and kinesin-13 causes severe flagellar length defects that mirror defects with morpholino knockdown. Knockdown of the ventral disk MBP protein also causes severe structural defects that are highly prevalent and persist in the population more than 5 d longer than defects associated with transient morpholino-based knockdown. By expressing two guide RNAs in tandem to simultaneously knock down kinesin-13 and MBP, we created a stable dual knockdown strain with both flagellar length and disk defects. The efficiency and simplicity of CRISPRi in polyploid Giardia allows rapid evaluation of knockdown phenotypes and highlights the utility of CRISPRi for emerging model systems.

A high-throughput sequencing assay to comprehensively detect and characterize unicellular eukaryotes and helminths from biological and environmental samples

BACKGROUND

Several of the most devastating human diseases are caused by eukaryotic parasites transmitted by arthropod vectors or through food and water contamination. These pathogens only represent a fraction of all unicellular eukaryotes and helminths that are present in the environment and many uncharacterized organisms might have subtle but pervasive effects on health, including by modifying the microbiome where they reside. Unfortunately, while we have modern molecular tools to characterize bacterial and, to a lesser extent, fungal communities, we lack suitable methods to comprehensively investigate and characterize most unicellular eukaryotes and helminths: the detection of these organisms often relies on microscopy that cannot differentiate related organisms, while molecular assays can only detect the pathogens specifically tested.

RESULTS

Here, we describe a novel sequencing-based assay, akin to bacterial 16S rRNA sequencing, that enables high-throughput detection and characterization of a wide range of unicellular eukaryotes and helminths, including those from taxonomical groups containing all common human parasites. We designed and evaluated taxon-specific PCR primer pairs that selectively amplify all species from eight taxonomical groups (Apicomplexa, Amoeba, Diplomonadida, Kinetoplastida, Parabasalia, Nematoda, Platyhelminthes, and Microsporidia). We then used these primers to screen DNA extracted from clinical, biological, and environmental samples, and after next-generation sequencing, identified both known and previously undescribed organisms from most taxa targeted.

CONCLUSIONS

This novel high-throughput assay enables comprehensive detection and identification of eukaryotic parasites and related organisms, from a wide range of complex biological and environmental samples. This approach can be easily deployed to many settings and will efficiently complement existing methods and provide a holistic perspective on the microbiome.

Giardia duodenalis in the UK: current knowledge of risk factors and public health implications

Giardia duodenalis is a ubiquitous flagellated protozoan parasite known to cause giardiasis throughout the world. Potential transmission vehicles for this zoonotic parasite are both water and food sources. As such consumption of water contaminated by feces, or food sources washed in contaminated water containing parasite cysts, may result in outbreaks. This creates local public health risks which can potentially cause widespread infection and long-term post-infection sequelae. This paper provides an up-to-date overview of G. duodenalis assemblages, sub-assemblages, hosts and locations identified. It also summarizes knowledge of potential infection/transmission routes covering water, food, person-to-person infection and zoonotic transmission from livestock and companion animals. Public health implications focused within the UK, based on epidemiological data, are discussed and recommendations for essential Giardia developments are highlighted.

Secreted Giardia intestinalis cysteine proteases disrupt intestinal epithelial cell junctional complexes and degrade chemokines

Giardiasis is a common diarrheal disease caused by the protozoan parasite Giardia intestinalis. Cysteine proteases (CPs) are acknowledged as virulence factors in Giardia but their specific role in the molecular pathogenesis of disease is not known. Herein, we aimed to characterize the three main secreted CPs (CP14019, CP16160 and CP16779), which were identified by mass spectrometry in the medium during interaction with intestinal epithelial cells (IECs) in vitro. First, the CPs were epitope-tagged and localized to the endoplasmic reticulum and cytoplasmic vesicle-like structures. Second, we showed that recombinant CPs, expressed in Pichia pastoris, are more active in acidic environment (pH 5.5-6) and we determined the kinetic parameters using fluorogenic substrates. Third, excretory-secretory proteins (ESPs) from Giardia trophozoites affect the localization of apical junctional complex (AJC) proteins and recombinant CPs cleave or re-localize the AJC proteins (claudin-1 and -4, occludin, JAM-1, β-catenin and E-cadherin) of IECs. Finally, we showed that the ESPs and recombinant CPs can degrade several chemokines, including CXCL1, CXCL2, CXCL3, IL-8, CCL2, and CCL20, which are up-regulated in IECs during Giardia-host cell interactions. This is the first study that characterizes the role of specific CPs secreted from Giardia and our results collectively indicate their roles in the disruption of the intestinal epithelial barrier and modulating immune responses during Giardia infections.

DNA damage induced by metronidazole in Giardia duodenalis triggers a DNA homologous recombination response

The mechanisms underlying metronidazole (MTZ) resistance in Giardia duodenalis have been associated with decreased activity of the enzymes implicated in its activation including nitroductase-1, thioredoxin reductase and pyruvate-ferredoxin oxidoreductase (PFOR). MTZ activation generates radicals that can form adducts with proteins such as thioredoxin reductase and α- and -β giardins as well as DNA damage resulting in trophozoite's death. The damage induced in DNA requires a straight forward response that may allow parasite survival. Here, we studied changes in histone H2A phosphorylation to evaluate the DNA repair response pathway after induction of double strand break (DSB) by MTZ in Giardia DNA. Our results showed that the DNA repair mechanisms after exposure of Giardia trophozoites to MTZ, involved a homologous recombination pathway. We observed a significant increase in the expression level of proteins GdDMC1B, which carries out Rad51 role in G. duodenalis, and GdMre11, after 12 h of exposure to 3.2 μM MTZ. This increase was concomitant with the generation of DSB in the DNA of trophozoites treated MTZ. Altogether, these results suggest that MTZ-induced DNA damage in Giardia triggers the DNA homologous recombination repair (DHRR) pathway, which may contribute to the parasite survival in the presence of MTZ.

Biochemical Characterization and Structural Modeling of Fused Glucose-6-Phosphate Dehydrogenase-Phosphogluconolactonase from Giardia lamblia

Glucose-6-phosphate dehydrogenase (G6PD) is the first enzyme in the pentose phosphate pathway and is highly relevant in the metabolism of Giardialamblia. Previous reports suggested that the G6PD gene is fused with the 6-phosphogluconolactonase (6PGL) gene (6pgl). Therefore, in this work, we decided to characterize the fused G6PD-6PGL protein in Giardialamblia. First, the gene of g6pd fused with the 6pgl gene (6gpd::6pgl) was isolated from trophozoites of Giardialamblia and the corresponding G6PD::6PGL protein was overexpressed and purified in Escherichia coli. Then, we characterized the native oligomeric state of the G6PD::6PGL protein in solution and we found a catalytic dimer with an optimum pH of 8.75. Furthermore, we determined the steady-state kinetic parameters for the G6PD domain and measured the thermal stability of the protein in both the presence and absence of guanidine hydrochloride (Gdn-HCl) and observed that the G6PD::6PGL protein showed alterations in the stability, secondary structure, and tertiary structure in the presence of Gdn-HCl. Finally, computer modeling studies revealed unique structural and functional features, which clearly established the differences between G6PD::6PGL protein from G. lamblia and the human G6PD enzyme, proving that the model can be used for the design of new drugs with antigiardiasic activity. These results broaden the perspective for future studies of the function of the protein and its effect on the metabolism of this parasite as a potential pharmacological target.

Recent advances in the genomic and molecular biology of Giardia

Giardia duodenalis is the most common gastrointestinal protozoan parasite of humans and a significant contributor to the global burden of both diarrheal disease and post-infectious chronic disorders. Robust tools for analyzing gene function in this parasite have been developed and a range of genetic tools are now available. These together with public databases have provided insights on the function of different genes in Giardia. In this review we provide a current perspective on different molecular aspects of Giardia related to genomics, regulation of encystation, trophozoite transcriptional responses to physiological and xenobiotic (drug-induced) stress, and mechanisms of drug resistance. We also examine recent insights that have contributed to gain knowledge in the study of VSPs, antigenic variation, epigenetics, DNA repair and in the direct manipulation of gene function in Giardia, with a particular focus on the inducible Cre/loxP system.

Molecular characterization of Cryptosporidium spp. and Giardia duodenalis in children in Egypt

BACKGROUND

The transmission of Cryptosporidium spp. and Giardia duodenalis into humans varies according to species/genotypes of the pathogens. Although infections with both parasites are recorded in Egypt, few data are available on the distribution of Cryptosporidium species and G. duodenalis genotypes. The present study assessed the occurrence and genetic diversity of Cryptosporidium spp. and G. duodenalis in Egyptian children.

METHODS

In the present study, 585 fecal specimens were collected from children eight years old and younger in three provinces (El-Dakahlia, El-Gharbia and Damietta) during March 2015 to April 2016. PCR-RFLP analysis of the small subunit rRNA gene and sequence analysis of the 60 kDa glycoprotein gene were used to detect and subtype Cryptosporidium spp., respectively, whereas PCR and sequence analyses of the triose phosphate isomerase, glutamate dehydrogenase and β-giardin genes were used to detect and genotype Giardia duodenalis.

RESULTS

The overall infection rates of Cryptosporidium spp. and G. duodenalis were 1.4% and 11.3%, respectively. The Cryptosporidium species identified included C. hominis and C. parvum, each with three subtype families. The C. hominis subtypes were IbA6G3 (n = 2), IdA17 (n = 1), IdA24 (n = 1) and IfA14G1R5 (n = 1), while C. parvum subtypes were IIdA20G1 (n = 1), IIaA15G2R1 (n = 1), and IIcA5G3a (n = 1). The G. duodenalis identified included both assemblages A (n = 31) and B (n = 34). All G. duodenalis assemblage A belonged to the anthroponotic sub-assemblage AII, while a high genetic heterogeneity was seen within assemblage B.

CONCLUSIONS

Data from this study are useful in our understanding of the genetic diversity of Cryptosporidium spp. and G. duodenalis in Egypt and the potential importance of anthroponotic transmission in the epidemiology of both pathogens.