Pathogenesis and post-infectious complications in giardiasis

Giardiavirus infection alleviates growth restriction and intestinal damage caused by the intestinal parasite Giardia duodenalis

BACKGROUND

Giardia duodenalis is a prevalent intestinal pathogen causing giardiasis, a condition characterized by diarrhea and frequently linked to malnutrition and growth impairments in children. The virulence of Giardiavirus (GLV) may efficiently clear Giardia parasites from infected patients. However, we have a limited understanding of GLV transmission among Giardia species and GLV-infected Giardia's impact on pathogenicity.

METHODS

This study investigated extracellular vesicles (EVs) isolated via ultracentrifugation or exosome assay kit to detect the presence of GLV in EVs, the results were detected using ultrastructure and molecular methods, including transmission electron microscopy, scanning electron microscopy, quantitative polymerase chain reaction (qPCR), and dot blot. Transwell migration assays confirmed the spread of GLV-enveloped EVs among Giardia species using inhibitor experiments and immunofluorescence. Mice gavaged with Giardia, with or without GLV infection, were assessed for disease progression, including growth parameters (weight and size gains), intestinal permeability, and pathology.

RESULTS

Parts of GLV exploit the Giardia EVs pathway to reach the extracellular environment, allowing GLV to spread among Giardia species via these EVs. The uptake of GLV-containing EVs by Giardia results in rapid trophozoite infection, and GLV wrapped in EVs also offers protection against external interference. Importantly, EV-coated GLV-infected Giardia leads to divergent clinical symptoms in mice, posing less risk to mice and reducing symptoms, such as emaciation, stunted growth, and lesion damage, compared with GLV-free Giardia-infected mice.

CONCLUSIONS

Our studies show that GLV wrapped in EVs can spread among Giardia species, and GLV infection alleviates the lesions caused by Giardia. These findings reveal that GLV could be a target for the development of novel intervention strategies against Giardia.

Performance of the Vetscan Imagyst in point-of-care detection of Giardia duodenalis in canine fecal samples

Giardia duodenalis is a common parasite of the gastrointestinal tract of dogs, with an especially high prevalence in dogs <1-y-old. Methods for detecting G. duodenalis are point-of-care (POC) tests such as lateral-flow tests or fecal flotation. The Vetscan Imagyst (Zoetis) is a new POC device for the detection of G. duodenalis in fecal samples using zinc sulfate flotation, automated slide scanning, and image recognition with artificial intelligence. Vetscan results are the number of Giardia cysts per coverslip. We compared the performance of the Vetscan and another POC test (SNAP Giardia test; Idexx) with a direct immunofluorescence assay (IFA) performed in a specialized parasitology laboratory as the reference test. We included 164 dogs <19-mo-old. We used pooled fecal samples from 3 defecations gained within 2-3 d and tested the repeatability of the Vetscan by triplicate measurement. Compared to IFA, Vetscan had a diagnostic sensitivity of 88.4% and specificity of 98.1%; SNAP had a diagnostic sensitivity of 74.4% and specificity of 98.1%. A variation coefficient of 67.0% was determined for the Vetscan results. The performance of the Vetscan is acceptable for the qualitative evaluation of fecal samples (Giardia positive or negative), and the device can be used by untrained personnel. Given its high variation coefficient, we do not recommend the Vetscan for monitoring the number of cysts.

Molecular characterization and risk analysis of Giardia duodenalis assemblages in corticosteroid-treated and non-treated patients in Ismailia, Arab Republic of Egypt

BACKGROUND

Giardia duodenalis (G. duodenalis) is an intestinal protozoan parasite of human and animal hosts. The present study investigated and compared the assemblages of G. duodenalis-infected faecal samples in patients on corticosteroid therapy (POCT) and control patients-not on corticosteroid therapy (CONT) and differentiated its assemblages and/or sub-assemblages' relationship with associated risk factors.

METHODS

Utilizing multi-locus sequence typing (MLST) with three loci targeted-triosephosphate isomerase (tpi), ꞵ-giardin (bg), and glutamate dehydrogenase (gdh)-G. duodenalis isolated from POCT and CONT were analyzed. Risk factors linked with Giardia infection and its assemblages were investigated.

RESULTS

In total, 52 G. duodenalis-infected patients were enrolled: 21 POCT and 31 CONT. The mean age was 12.3 years, the majority were male (59.6%), and 73.1% lived in rural areas. The POCT group was 36 times more likely than the CONT group to have a concurrent parasitic infection. About 73% (38/52) of Giardia samples were genotyped and/or sub-genotyped in at least one of the three loci. MLST identified sixteen isolates (42.0%) as assemblage B, ten isolates (26.3%) as assemblage A, and twelve isolates (31.6%) as a mixed infection of A + B and B + E. Most individuals of the POCT group were infected with G. duodenalis assemblage A while most of the CONT group were infected with assemblage B. Sub-assemblage AII was identified by phylogenetic analysis in the isolates of both groups under investigation.

CONCLUSION

This research advances giardiasis epidemiology in Arab Republic of Egypt (ARE) and reflects how corticosteroid-treated patients differ from those non-treated in Giardia assemblage pattern and their susceptibility to concomitant infection. Overall, Giardia assemblage patterns in this research populations reflect anthroponotic and zoonotic transmission, emphasizing the importance of public health policy and giardiasis prevention of illness transmission, particularly among those on corticosteroid therapy in ARE.

Multiplex PCR for gastrointestinal parasites in stool: Benchmarking against direct microscopy and simplex PCR

PURPOSE

To develop and validate a multiplex conventional PCR assay to simultaneously detect Cryptosporidium spp., Entamoeba histolytica, and Giardia lamblia in diarrheal samples as a rapid, cost-effective, and sensitive diagnostic tool for prevalent co-infections for improved diagnostic accuracy and efficiency in resource-limited settings.

METHODS

Stool samples collected from patients with gastrointestinal symptoms after taking written consent, processed via wet mount, iodine mount, and PCR assays. Cohen's kappa statistical analysis was done to test agreement.

RESULT

Among 240 patients, 28.75% showed intestinal protozoa via Microscopy; Single-plex and multiplex PCR demonstrated 100% concordance, detecting 27.9%; confirmed by sequencing. Highest parasite positivity was observed in transplant and immunocompromised patients, with moderate to almost perfect agreement between microscopy and molecular methods.

CONCLUSION

Multiplex-conventional PCR offers superior sensitivity and specificity over microscopy and 100% concordance with single-plex PCR, enabling rapid, cost-effective diagnosis of multiple parasites from single stool sample. Its adoption could revolutionize parasitic infection management in routine diagnostics.

Lactobacillus gasseri and Gardnerella vaginalis produce extracellular vesicles that contribute to the function of the vaginal microbiome and modulate host-Trichomonas vaginalis interactions

Trichomonas vaginalis is an extracellular protozoan parasite of the human urogenital tract, responsible for a prevalent sexually transmitted infection. Trichomoniasis is accompanied by a dysbiotic microbiome that is characterised by the depletion of host-protective commensals such as Lactobacillus gasseri, and the flourishing of a bacterial consortium that is comparable to the one seen for bacterial vaginosis, including the founder species Gardnerella vaginalis. These two vaginal bacteria are known to have opposite effects on T. vaginalis pathogenicity. Studies on extracellular vesicles (EVs) have been focused on the direction of a microbial producer (commensal or pathogen) to a host recipient, and largely in the context of the gut microbiome. Here, taking advantage of the simplicity of the human cervicovaginal microbiome, we determined the molecular cargo of EVs produced by L. gasseri and G. vaginalis and examined how these vesicles modulate the interaction of T. vaginalis and host cells. We show that these EVs carry a specific cargo of proteins, which functions can be attributed to the opposite roles that these bacteria play in the vaginal biome. Furthermore, these bacterial EVs are delivered to host and protozoan cells, modulating host-pathogen interactions in a way that mimics the opposite effects that these bacteria have on T. vaginalis pathogenicity. This is the first study to describe side-by-side the protein composition of EVs produced by two bacteria belonging to the opposite spectrum of a microbiome and to demonstrate that these vesicles modulate the pathogenicity of a protozoan parasite. Such as in trichomoniasis, infections and dysbiosis co-occur frequently resulting in significant co-morbidities. Therefore, studies like this provide the knowledge for the development of antimicrobial therapies that aim to clear the infection while restoring a healthy microbiome.

Intestinal parasitic infections in children from marginalised Roma communities: prevalence and risk factors

BACKGROUND

Intestinal parasitic infections remain a significant global health issue, particularly affecting poor and marginalised populations. These infections significantly contribute to children's diseases, malnutrition, poor school performance, cognitive disorders, and future economic losses. This study aimed to explore and compare the occurrence of intestinal parasites in early childhood among the group of infants from the Slovak majority population and from marginalised Roma communities (MRCs). Furthermore, it aimed to explore the health complaints of children with and without intestinal parasitic infection in the past month and assess the effect of various risk factors on the occurrence of intestinal parasitic infection in infants from MRCs.

METHODS

We obtained cross-sectional data from mothers and stool samples of their children aged 13-21 months using the first wave of the longitudinal RomaREACH study. A total of 181 stools from infants were analysed: 105 infants from the Slovak majority population and 76 from MRCs.

RESULTS

Infants from MRCs are significantly more often infected by Ascaris lumbricoides, Trichuris trichiura and Giardia duodenalis than their better-off peers from the majority population. Infection rates are 30% in infants from MRCs vs. 0% in the majority population (p < 0.001). Single and mixed infections were observed in children from MRCs. Infants with intestinal parasitic infections suffer significantly more often from various health complaints, particularly cough, stomach ache, irritability, and diarrhoea. Within MRCs, the risk of parasitic infections in infants is significantly increased by risk factors such as the absence of flushing toilets in households (OR = 4.17, p < 0.05) and contact with un-dewormed animals (OR = 3.61, p < 0.05). Together with the absence of running water in the household, these three factors combined increase the risk more than ten times (p < 0.01).

CONCLUSION

Maintaining hygienic standards in conditions of socioeconomic deprivation in MRCs without running water and sewage in the presence of un-dewormed animals is problematic. These living conditions contribute to the higher prevalence of parasitic infections in children from MRCs, causing various health complaints and thus threatening their health and healthy development.

Mucosal vaccination in a murine gnotobiotic model of Giardia lamblia infection

Giardia lamblia is an important protozoan cause of diarrheal disease worldwide, delayed development and cognitive impairment in children in low- and middle-income countries, and protracted post-infectious syndromes in developed regions. G. lamblia resides in the lumen and at the epithelial surface of the proximal small intestine but is not mucosa invasive. The protozoan parasite is genetically diverse with significant genome differences across strains and assemblages. Animal models, particularly murine models, have been instrumental in defining mechanisms of host defense against G. lamblia, but mice cannot be readily infected with most human pathogenic strains. Antibiotic pretreatment can increase susceptibility, suggesting that the normal microbiota plays a role in controlling G. lamblia infection in mice, but the broader implications on susceptibility to diverse strains are not known. Here, we have used gnotobiotic mice to demonstrate that robust intestinal infection can be achieved for a broad set of human-pathogenic strains of the genetic assemblages A and B. Furthermore, gnotobiotic mice were able to eradicate infection with a similar kinetics to conventional mice after trophozoite challenge. Germ-free mice could also be effectively immunized by the mucosal route with a protective antigen, α1-giardin, in a manner dependent on CD4 T cells. These results indicate that the gnotobiotic mouse model is powerful for investigating acquired host defenses in giardiasis, as the mice are broadly susceptible to diverse G. lamblia strains yet display no apparent defects in mucosal immunity needed for controlling and eradicating this lumen-dwelling pathogen.

Exploration of Giardia small nucleolar RNAs (snoRNAs) and their possible microRNA derivatives

Small nucleolar RNAs (snoRNAs) are short non-coding RNAs that are abundant in the nucleoli of eukaryotic cells and play a crucial role in various aspects of ribosomal RNA (rRNA) maturation, including modifications such as 2′-O-methylation or pseudouridylation. On the other hand, Giardia duodenalis is a microaerophilic, flagellated, binucleate protozoan responsible for causing giardiasis. Although numerous snoRNAs have been detected in Giardia, their investigation remains limited. Nevertheless, they have been found to play a crucial role in the rRNA precursor processing pathway and influence other cellular functions. In addition, it has been proposed that some microRNAs are generated from these snoRNAs through excision by the Giardia endoribonuclease Dicer. These microRNAs are believed to contribute to the regulation of antigenic variation, which allows the parasite to evade the host immune response. Specifically, they play a role in modulating variant-specific surface proteins (VSPs) and other cysteine-rich surface antigens (CSAs). The main objective of this study was to bring together the available data on snoRNAs in Giardia, uncovering their functions in various processes and their importance on a global scale. In addition, the research delved into potential microRNAs speculated to originate from snoRNAs, exploring their impact on cellular processes.

Giardia telomeres and telomerase

Giardia duodenalis, the protozoan responsible for giardiasis, is a significant contributor to millions of diarrheal diseases worldwide. Despite the availability of treatments for this parasitic infection, therapeutic failures are alarmingly frequent. Thus, there is a clear need to identify new therapeutic targets. Giardia telomeres were previously identified, but our understanding of these structures and the critical role played by Giardia telomerase in maintaining genomic stability and its influence on cellular processes remains limited. In this regard, it is known that all Giardia chromosomes are capped by small telomeres, organized and protected by specific proteins that regulate their functions. To counteract natural telomere shortening and maintain high proliferation, Giardia exhibits constant telomerase activity and employs additional mechanisms, such as the formation of G-quadruplex structures and the involvement of transposable elements linked to telomeric repeats. Thus, this study aims to address the existing knowledge gap by compiling the available information (until 2023) about Giardia telomeres and telomerase, focusing on highlighting the distinctive features within this parasite. Furthermore, the potential feasibility of targeting Giardia telomeres and/or telomerase as an innovative therapeutic strategy is discussed.

Current Understanding of Giardia lamblia and Pathogenesis of Stunting and Cognitive Deficits in Children from Low- and Middle-Income Countries

Purpose of Review

Giardia lamblia is a common intestinal parasite worldwide, mainly in children from low- and middle-income countries (LMIC). Also, it has been associated with increased intestinal permeability, stunting, and cognitive impairment. Nonetheless, the pathogenesis of long-term consequences is difficult to elucidate.

Recent Findings

Recent studies try to understand the long-term consequences of Giardia infections. First, well-characterized studies associate Giardia with intestinal damage and child growth. Second, infections appear not to be associated with inflammation, but "lack of inflammation" may not, however, entirely exclude a pro-inflammatory pathway. Finally, some important amino acids are lower and could contribute to prolongate stunting and cognitive deficit.

Summary

Giardia infections in LMIC used to be associated with child growth shortfalls, gut permeability, and cognitive deficits. Multifactorial effects could be associated with Giardia, including nutritional, altered microbiota, and generation of potentially toxic microbial metabolic byproducts, all together increasing risk of long-term outcomes.

Evaluation of the Use of Singleplex and Duplex CerTest VIASURE Real-Time PCR Assays to Detect Common Intestinal Protist Parasites

Cryptosporidium spp., Giardia duodenalis and Entamoeba histolytica are species of protozoa- causing diarrhoea that are common worldwide, while Entamoeba dispar, Dientamoeba fragilis and Blastocystis sp. appear to be commensal parasites whose role in pathogenicity remains controversial. We conducted the clinical evaluation of five singleplex and one duplex CerTest VIASURE Real-Time PCR Assays against a large panel of positive DNA samples (n = 358), and specifically to Cryptosporidium spp. (n = 96), G. duodenalis (n = 115), E. histolytica (n = 25) E. dispar (n = 11), Blastocystis sp. (n = 42), D. fragilis (n = 37), and related parasitic phylum species such as Apicomplexa, Euglenozoa, Microsporidia and Nematoda. DNA samples were obtained from clinical stool specimens or cultured isolates in a national reference centre. Estimated diagnostic sensitivity and specificity values were 0.94-1 for Cryptosporidium spp., 0.96-0.99 for G. duodenalis, 0.96-1 for E. histolytica, 1-1 for E. dispar, and 1-0.99 for D. fragilis in the evaluated singleplex assays. In the duplex assay for the simultaneous detection of Blastocystis sp. and D. fragilis these values were 1-0.98 and 1-0.99, respectively. Measures of diagnostic precision for repeatability and reproducibility were found to be under acceptable ranges. The assays identified six Cryptosporidium species (C. hominis, C. parvum, C. canis, C. felis, C. scrofarum, and C. ryanae), four G. duodenalis assemblages (A, B, C, and F), and six Blastocystis subtypes (ST1-ST5, and ST8). The evaluated singleplex and duplex VIASURE Real-Time PCR assays provide sensitive, practical, and cost-effective choices to the molecular diagnosis of the main diarrhoea-causing intestinal protists in clinical microbiology and research laboratories.

Differential gene expression (DGE) analysis in persons with a history of giardiasis

Giardiasis, which is caused by Giardia duodenalis, has clinical symptoms such as steatorrhea and can be very dangerous in children. In addition, some documents reported that this parasite is present inside the tissue of patients with cancer. In this study, we analyzed the gene expression profiles of some main genes important to apoptosis and anti-apoptosis in humans.Expression profile arrays of Genomic Spatial Event (GSE) 113666, GSE113667, and GSE113679 obtained from Gene Expression Omnibus were used for meta-analysis using R commands. Cytoscape and STRING databases used the protein-protein Interaction network. Then, the Kyoto Encyclopedia of Genes and Genomes and Gene Ontology analysis was performed. Similar genes in Homo sapiens were identified using Basic Local Alignment Search Tool analysis. The validation was performed on eight people using real-time Polymerase chain reaction. In addition to the candidate genes, the gene expression of some other genes, including Serine/Threonine Kinase 1 (AKT1), Cyclin Dependent Kinase Inhibitor 2A (CDKN2A), Kirsten Rat Sarcoma (KRAS), and Phosphatidylinositol-4,5-Bisphosphate 3-Kinase Catalytic Subunit Alpha (PIK3CA) were also examined. Analysis of the expression of serum amyloid A1 (SAA1), Regenerating Islet-Derived 3 Gamma (REG3G), and REG3A genes did not show any difference between the two groups of healthy and diseased people. Examining the mean expression of the four genes AKT1, CDKN2A, KRAS, and PIK3CA showed that three genes of AKT1, CDKN2A, and KRAS had increased expression in people with a history of giardiasis compared to healthy people. We showed that the gene expression pattern differs in apoptosis and anti-apoptosis signaling in people with a history of giardiasis. Giardia duodenalis seems to induce post-non-infectious symptoms with stimulation of human gene expression.

Giardiasis and diarrhea in dogs: Does the microbiome matter?

BACKGROUND

Giardia duodenalis (Gd) causes intestinal parasitosis. The involvement of the intestinal microbiome in determining the infection's clinical phenotype is unknown.

OBJECTIVE

Investigate the fecal microbiome features in dogs with giardiasis.

ANIMALS AND METHODS

Cross-sectional study, including fecal samples of kenneled dogs with Gd diagnosed by fecal Giardia antigen dot ELISA. The fecal microbial compositional characteristics and dysbiosis index (DI) were compared between diarrheic and nondiarrheic dogs.

RESULTS

Fecal samples of 38 Gd-infected dogs (diarrheic, 21; nondiarrheic, 17) were included. No differences were found in Faith's phylogenic diversity and beta diversity (weighted UniFrac distances) and in specific taxa abundances at the phylum, genus, and species levels, as well as in alpha and beta diversities between diarrheic and nondiarrheic dogs, and also when divided by sex or age. Among diarrheic dogs, alpha diversity was higher in males than in females (pairwise Kruskal-Wallis, q = 0.01). Among males, fecal abundances of the genus Clostridium (W = 19) and Clostridium spiroforme species (W = 33) were higher in diarrheic compared to nondiarrheic dogs. In diarrheic dog fecal samples, Proteobacteria were more prevalent (W = 1), whereas Verrucomicrobia were less prevalent in dogs <1 year of age than in older dogs. The fecal sample DI of 19 diarrheic and 19 nondiarrheic dogs was similar (median, -0.2; range, -4.3 to 4.5 and median, -1.0; range, -4.3 to 5.8, respectively).

CONCLUSIONS

The fecal microbial composition of symptomatic and asymptomatic dogs with giardiasis is similar. Based on fecal DI, giardiasis is not characterized by prominent dysbiosis. Other host and parasite characteristics might determine the severity of giardiasis in dogs.

[Feline and canine giardiosis: An Update]

Giardia duodenalis is a facultative pathogenic intestinal parasite. Giardiosis in dogs and cats may appear with or without clinical signs. Typical signs include diarrhea with or without vomiting. The prevalence in young animals is high and may amount to up to 50%. There are 8 different genotypes (A - H), which are called assemblages. Assemblages C and D are most common in dogs and assemblage F most frequent in cats. However, animals may also be infected with the zoonotically effective assemblages A and B or exhibit mixed infections. The immunofluorescence test (IFA), the enzyme-linked immunosorbent assay (ELISA) and fecal centrifugation using zinc sulphate solution are currently recommended as diagnostic methods. Polymerase chain reaction (PCR) may be used to determine the corresponding assemblage. Approved treatments for giardiosis include fenbendazole and metronidazole. In addition, undertaking specific hygiene measures is warranted. Only animals showing clinical signs or those living in the same household with high-risk patients (e. g. immunosuppressed humans) are recommended to receive medication. The aim of treatment is clinical improvement of the diseased dogs and cats. Frequently, complete elimination of Giardia is not attained.

A thermo-resistant and RNase-sensitive cargo from Giardia duodenalis extracellular vesicles modifies the behaviour of enterobacteria

Extracellular vesicles (EVs) recently emerged as important players in the pathophysiology of parasitic infections. While the protist parasite Giardia duodenalis can produce EVs, their role in giardiasis remains obscure. Giardia can disrupt gut microbiota biofilms and transform commensal bacteria into invasive pathobionts at sites devoid of colonizing trophozoites via unknown mechanisms. We hypothesized that Giardia EVs could modify gut bacterial behaviour via a novel mode of trans-kingdom communication. Our findings indicate that Giardia EVs exert bacteriostatic effects on Escherichia coli HB101 and Enterobacter cloacae TW1, increasing their swimming motility. Giardia EVs also decreased the biofilm-forming ability of E. coli HB101 but not by E. cloacae TW1, supporting the hypothesis that these effects are, at least in part, bacteria-selective. E. coli HB101 and E. cloacae TW1 exhibited increased adhesion/invasion onto small intestine epithelial cells when exposed to Giardia EVs. EVs labelled with PKH67 revealed colocalization with E. coli HB101 and E. cloacae TW1 bacterial cells. Small RNA sequencing revealed a high abundance of ribosomal RNA (rRNA)- and transfer RNA (tRNA)-derived small RNAs, short-interfering RNAs (siRNAs) and micro-RNAs (miRNAs) within Giardia EVs. Proteomic analysis of EVs uncovered the presence of RNA chaperones and heat shock proteins that can facilitate the thermal stability of EVs and its sRNA cargo, as well as protein-modifying enzymes. In vitro, RNase heat-treatment assays showed that total RNAs in EVs, but not proteins, are responsible for modulating bacterial swimming motility and biofilm formation. G. duodenalis small RNAs of EVs, but not proteins, were responsible for the increased bacterial adhesion to intestinal epithelial cells induced upon exposure to Giardia EVs. Together, the findings indicate that Giardia EVs contain a heat-stable, RNase-sensitive cargo that can trigger the development of pathobiont characteristics in Enterobacteria, depicting a novel trans-kingdom cross-talk in the gut.

Microbiota and parasite relationship

The diversity of microbiota is different in each person. Many health problems such as autoimmune diseases, diabetes, cardiovascular diseases, and depression can be caused by microbiota imbalance. Since the parasite needs a host to survive, it interacts closely with the microbiota elements. Blastocystis acts on the inflammatory state of the intestine and may cause various gastrointestinal symptoms, on the contrary, it is more important for gut health because it causes bacterial diversity and richness. Blastocystis is associated with changes in gut microbiota composition, the ultimate indicator of which is the Firmicutes/Bacteroidetes ratio. The Bifidobacterium genus was significantly reduced in IBS patients and Blastocystis, and there is a significant decrease in Faecalibacterium prausnitzii, which has anti-inflammatory properties in Blastocystis infection without IBS. Lactobacillus species reduce the presence of Giardia, and the produced bacteriocins prevent parasite adhesion. The presence of helminths has been strongly associated with the transition from Bacteroidetes to Firmicutes and Clostridia. Contrary to Ascaris, alpha diversity in the intestinal microbiota decreases in chronic Trichuris muris infection, and growth and nutrient metabolism efficiency can be suppressed. Helminth infections indirectly affect mood and behavior in children through their effects on microbiota change. The main and focus of this review is to address the relationship of parasites with microbiota elements and to review the data about what changes they cause. Microbiota studies have gained importance recently and it is thought that it will contribute to the treatment of many diseases as well as in the fight against parasitic diseases in the future.

Regulatory Functions of Hypoxia in Host-Parasite Interactions: A Focus on Enteric, Tissue, and Blood Protozoa

Body tissues are subjected to various oxygenic gradients and fluctuations and hence can become transiently hypoxic. Hypoxia-inducible factor (HIF) is the master transcriptional regulator of the cellular hypoxic response and is capable of modulating cellular metabolism, immune responses, epithelial barrier integrity, and local microbiota. Recent reports have characterized the hypoxic response to various infections. However, little is known about the role of HIF activation in the context of protozoan parasitic infections. Growing evidence suggests that tissue and blood protozoa can activate HIF and subsequent HIF target genes in the host, helping or hindering their pathogenicity. In the gut, enteric protozoa are adapted to steep longitudinal and radial oxygen gradients to complete their life cycle, yet the role of HIF during these protozoan infections remains unclear. This review focuses on the hypoxic response to protozoa and its role in the pathophysiology of parasitic infections. We also discuss how hypoxia modulates host immune responses in the context of protozoan infections.

Parasitic infections as potential risk factors for attention deficit hyperactivity disorder (ADHD) in children

Attention deficit hyperactivity disorder (ADHD) represents a mysterious neuropsychiatric alarming concern due to indefinite etiopathogenesis among children. Notably, the studies which investigated the correlation between ADHD and parasitic infections are insufficient. Therefore, this research aimed to assess the correlation between ADHD and some tissue dwelling and intestinal parasitic infections in children. The study was conducted on 200 children, including 100 children suffering from ADHD (Group I) and 100 healthy children as a control group (Group II). All caregivers fulfilled predesigned sociodemographic form and Conners parent rating scale (CPRS-48) questionnaire. Blood samples were collected to determine hemoglobin level as well as relative eosinophilic count. The presence of anti-Toxoplasma IgG and anti-Toxocara IgG in serum by Enzyme-Linked Immunosorbent Assay (ELISA) was further investigated. Also, micronutrients as zinc, iron, and copper levels were measured. Schistosoma antigen was investigated in urine samples. Stool samples were subjected to direct wet smear, concentration technique and modified Ziehl-Neelsen (MZN) staining for coccidian parasites detection. Cryptosporidium parvum, Giardia lamblia and Entamoeba histolytica antigens were investigated in stool samples. Group I expressed more liability to sociodemographic risk factors, decreased levels of Hb, iron, zinc, and copper with statistically significant difference (P < 0.001). Comparison between Group I and Group II regarding the detected parasitic infections exhibited statistically significant difference except Schistosoma antigen positivity which expressed no statistical significance. The present study concluded that the parasitic infections with their consequences are potential risk factors in children with ADHD indicating that their early diagnosis and treatment may help in ADHD prevention.

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

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

Multigene typing of Giardia Duodenalis isolated from tuberculosis and non-tuberculosis subjects

Giardia duodenalis is a cryptic protozoan, which has eight assemblages (A-H). Assemblages A and B are the main genotypes reported from humans with probable anthroponotic and zoonotic transmission. The current study aimed to characterize G. duodenalis assemblages in tuberculosis (TB) patients and healthy subjects using multilocus genotyping (MLG). Thirty Giardia-positive stool samples, which were obtained from TB patients and healthy subjects were included in the study. After total DNA extraction, three β-giardin (bg), triosephosphate isomerase (tpi), glutamate dehydrogenase (gdh) genes were amplified and sequenced. Obtained sequences were compared to the GenBank database to characterize assemblages. Phylogenetic analysis using Maximum Likelihood (ML) and Tamura 3-parameter was performed for each gene. From 30 Giardia-positive subjects, 17 (57%) and 13 (43%) were from healthy and TB-infected subjects, respectively. There was no significant co-existence of Giardia and tuberculosis (P-value = 0.051). In addition, 14 (46.7%) and 16 (53.3%) of Giardia isolates were from asymptomatic and symptomatic subjects, respectively. PCR amplification was successful in 25 single samples (83.3%) consisted of 20 for tpi, 15 for bg, and 13 for gdh genes. Accordingly, 13/25 (52%) and 8/25 (32%) belonged to assemblage A and assemblages B, respectively, whereas 4/25 (16%) were either assemblage A or B with different genes at the same time. Significant correlation between assemblages and TB, age, and symptoms was not seen. The phylogenetic analyses represented no separation based on TB and gastrointestinal symptoms. Assemblage A was the predominant genotype in samples. The high frequency of assemblage AII indicated importance of anthroponotic transmission of Giardia in both healthy and TB patients. In addition, considering the exclusive reports of sub-assemblage AIII in wild ruminants, the presence of AIII in the current study have to be carefully interpreted. The inconsistency between the assemblage results of either bg or gdh loci with tpi gene signifies the insufficiency of single gene analysis and the necessity for MLG in molecular epidemiology of G. duodenalis.

Performance of sewage treatment technologies for the removal of Cryptosporidium sp. and Giardia sp.: Toward water circularity

Cryptosporidium sp. and Giardia sp. are parasites that cause diseases in the population. Most of parasite diseases regarding the consumption of drinking water polluted with sewage are caused by Cryptosporidium sp. or Giardia sp. it is because of the incomplete disinfection of the wastewater treatment. Therefore, in this work the removal or inactivation efficiency of different treatment technologies presented by around 40 scientific studies was evaluated, with a view to water circularity. For Cryptosporidium sp., we conclude that the most efficient secondary technologies are aerobic technologies, which remove between 0.00 and 2.17 log units (Ulog), with activated sludge presenting the greatest efficiency, and that the tertiary technologies with the greatest removal are those that use ultrasound, which reach removal values of 3.17 Ulog. In the case of Giardia sp., the secondary technologies with the greatest removal are anaerobic technologies, with values between 0.00 and 3.80 Ulog, and the tertiary technologies with the greatest removal are those that combine filtration with UV or a chemical disinfection agent. Despite the removal values obtained, the greatest concern remains detecting and quantifying the infectious forms of both parasites in effluents; therefore, although the technologies perform adequately, discharge effluents must be monitored with more sensitive techniques, above all aiming for circularity of the treated water in a context of the water scarcity that affects some parts of the world.

Molecular characterization of Giardia lamblia and risk factors for giardiasis among immunocompromised patients in southern Brazil

Acute Giardia infections often cause diarrhea and stomach upset. Chronic infections can lead to malnutrition, micronutrient deficiencies, malabsorption and weight loss. This study assessed the prevalence of G. lambia infection and assessed associated risk factors among immunocompomised patients undergoing chemotherapeutic treatment in southern Brazil. A total of 110 immunocompromised patients in Pelotas, RS, Brazil, consented to participate in this study and were recruited. Socioeconomic and epidemiological profile of patients was collected by questionnaire. The prevalence for Giardia were determined through microscopy by the centrifugation-flotation technique using stool samples of every patient. In addition, the genetic characterization of the parasite was carried out by amplifying and sequencing the glutamate dehydrogenase (gdh) gene. By microscopy, the prevalence of giardiasis was 17.3% (19/110). Furthermore, the DNA sequences revealed that 7 (36.8%) out of 19 isolates belonged to assemblage B, while 6 of them (31.6%) belonged to assemblage C, 5 (26.3%) to assemblage A and 1 (5.3%) to assemblage D. Risk factors (p ≤ 0.05) for giardiasis were schooling level (OR=8.0 (1.02 - 62.91) sharing a house with more than three people (OR=14.1 (3.77 - 52.51), water sources (OR=38.9 (10.4 - 145.7), sewage treatment (OR=14.2 (3.1 - 65.5), waste destination (OR=7.44 (2.0 - 27.3), owning pets (OR=4.6 (1.0 - 21.2) and cultivating a vegetable garden (OR=4.2 (1.3 - 13.6). The prevalence of G. lamblia in immunocompromised patients was considered elevate with the identification of four assemblage of the parasite (A, B, C and D).

Protozoa-Derived Extracellular Vesicles on Intercellular Communication with Special Emphasis on Giardia lamblia

Parasitic diseases are an important worldwide problem threatening human health and affect millions of people. Acute diarrhea, intestinal bleeding, malabsorption of nutrients and nutritional deficiency are some of the issues related to intestinal parasitic infections. Parasites are experts in subvert the host immune system through different kinds of mechanisms. There are evidences that extracellular vesicles (EVs) have an important role in dissemination of the disease and in modulating the host immune system. Released by almost all types of cells, these nanovesicles are a natural secretory product containing multiple components of interest. The EVs are classified as apoptotic bodies, microvesicles, exosomes, ectosomes, and microparticles, according to their physical characteristics, biochemical composition and cell of origin. Interestingly, EVs play an important role in intercellular communication between parasites as well as with the host cells. Concerning Giardia lamblia, it is known that this parasite release EVs during it life cycle that modulate the parasite growth and adherence as well the immune system of the host. Here we review the recently updates on protozoa EVs, with particular emphasis on the role of EVs released by the flagellate protozoa G. lamblia in cellular communication and its potential for future applications as vaccine, therapeutic agent, drug delivery system and as diagnostic or prognostic biomarker.

Diarrhea due to parasites: a short, updated point of view from the clinical setting

Diarrhea represents a common manifestation of several gastrointestinal diseases. Infectious agents are the most common causes of diarrhea in developing countries, where the inadequate sanitation and hygiene are prevalent. In these countries, the scarcity of preventive measures as well as the limited health resources cause a substantial increase in incidence, morbidity and mortality due to infectious diseases, including diarrhea. Currently, with the availability of rapid and inexpensive air transportation millions of people travel for tourism, work and immigration from developing countries to industrialized countries and vice versa. This leads to a high number of imported pathogens such as parasites causing infectious diarrhea. Importantly, while most cases of parasitic diarrhea are short, mild and self-limited, other cases may be associated with chronic diarrhea and serious morbidity and mortality. The aim of the current review was to provide an update, from a clinician's point of view, of the main parasites causing diarrhea, with a focus on their diagnosis and management in the clinical setting.

The Fire Under the Ash: Parasitic infections as potential risk factors for Attention Deficit Hyperactivity Disorder (ADHD) in children.. [DOI: 10.21203/rs.3.rs-1983187/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Attention deficit hyperactivity disorder (ADHD) represents a mysterious neuropsychiatric alarming concern due to indefinite etiopathogenesis among children. Notably, the studies which investigated the correlation between ADHD and parasitic infections are insufficient. Therefore, this research aimed to assess the correlation between ADHD and some tissue dwelling and intestinal parasitic infections in children. The study was conducted on 200 children, including 100 children suffering from ADHD (Group I) and 100 healthy children as a control group (Group II). All caregivers fulfilled predesigned sociodemographic form and Conners parent rating scale (CPRS-48) questionnaire. Blood samples were collected to determine hemoglobin level as well as relative eosinophilic count. The presence of anti-Toxoplasma IgG and anti-Toxocara IgG in serum by Enzyme-Linked Immunosorbent Assay (ELISA) was further investigated. Also, micronutrients as zinc, iron, and copper levels were measured. Schistosoma antigen was investigated in urine samples. Stool samples were subjected to direct wet smear, concentration technique and modified Ziehl-Neelsen (MZN) staining for coccidian parasites detection. Cryptosporidium parvum, Giardia lamblia and Entamoeba histolytica antigens were investigated in stool samples. Group I expressed more liability to sociodemographic risk factors, decreased levels of Hb, iron, zinc, and copper with statistically significant difference (P < 0.001). Comparison between Group I and Group II regarding the detected parasitic infections exhibited statistically significant difference except Schistosoma antigen positivity which expressed no statistical significance. The present study concluded that the parasitic infections with their consequences are potential risk factors in children with ADHD indicating that their early diagnosis and treatment may help in ADHD prevention.

Mimics of Crohn's Disease

Crohn's disease is a chronic inflammatory disease that can affect any portion of the gastrointestinal tract. Associated symptoms can vary based on the severity of disease, extent of involvement, presence of extraintestinal manifestations, and development of complications. Diagnosis is based on a constellation of findings. Many diseases can mimic Crohn's disease and lead to diagnostic conundrums. These include entities associated with the gastrointestinal luminal tract, vascular disease, autoimmune processes, various infections, malignancies and complications, drug- or treatment-induced conditions, and genetic diseases. Careful consideration of possible causes is necessary to establish the correct diagnosis.

Dual RNA Sequencing Reveals Key Events When Different Giardia Life Cycle Stages Interact With Human Intestinal Epithelial Cells In Vitro

Giardia intestinalis is a protozoan parasite causing diarrheal disease, giardiasis, after extracellular infection of humans and other mammals’ intestinal epithelial cells (IECs) of the upper small intestine. The parasite has two main life cycle stages: replicative trophozoites and transmissive cysts. Differentiating parasites (encysting cells) and trophozoites have recently been shown to be present in the same regions of the upper small intestine, whereas most mature cysts are found further down in the intestinal system. To learn more about host-parasite interactions during Giardia infections, we used an in vitro model of the parasite’s interaction with host IECs (differentiated Caco-2 cells) and Giardia WB trophozoites, early encysting cells (7 h), and cysts. Dual RNA sequencing (Dual RNAseq) was used to identify differentially expressed genes (DEGs) in both Giardia and the IECs, which might relate to establishing infection and disease induction. In the human cells, the largest gene expression changes were found in immune and MAPK signaling, transcriptional regulation, apoptosis, cholesterol metabolism and oxidative stress. The different life cycle stages of Giardia induced a core of similar DEGs but at different levels and there are many life cycle stage-specific DEGs. The metabolic protein PCK1, the transcription factors HES7, HEY1 and JUN, the peptide hormone CCK and the mucins MUC2 and MUC5A are up-regulated in the IECs by trophozoites but not cysts. Cysts specifically induce the chemokines CCL4L2, CCL5 and CXCL5, the signaling protein TRKA and the anti-bacterial protein WFDC12. The parasite, in turn, up-regulated a large number of hypothetical genes, high cysteine membrane proteins (HCMPs) and oxidative stress response genes. Early encysting cells have unique DEGs compared to trophozoites (e.g. several uniquely up-regulated HCMPs) and interaction of these cells with IECs affected the encystation process. Our data show that different life cycle stages of Giardia induce different gene expression responses in the host cells and that the IECs in turn differentially affect the gene expression in trophozoites and early encysting cells. This life cycle stage-specific host-parasite cross-talk is an important aspect to consider during further studies of Giardia’s molecular pathogenesis.

Different Drugs, Same End: Ultrastructural Hallmarks of Autophagy in Pathogenic Protozoa

Protozoan parasites interact with a wide variety of organisms ranging from bacteria to humans, representing one of the most common causes of parasitic diseases and an important public health problem affecting hundreds of millions of people worldwide. The current treatment for these parasitic diseases remains unsatisfactory and, in some cases, very limited. Treatment limitations together with the increased resistance of the pathogens represent a challenge for the improvement of the patient’s quality of life. The continuous search for alternative preclinical drugs is mandatory, but the mechanisms of action of several of these compounds have not been described. Electron microscopy is a powerful tool for the identification of drug targets in almost all cellular models. Interestingly, ultrastructural analysis showed that several classes of antiparasitic compounds induced similar autophagic phenotypes in trypanosomatids, trichomonadids, and apicomplexan parasites as well as in Giardia intestinalis and Entamoeba spp. with the presence of an increased number of autophagosomes as well as remarkable endoplasmic reticulum profiles surrounding different organelles. Autophagy is a physiological process of eukaryotes that maintains homeostasis by the self-digestion of nonfunctional organelles and/or macromolecules, limiting redundant and damaged cellular components. Here, we focus on protozoan autophagy to subvert drug effects, discussing its importance for successful chemotherapy.

Conserved metabolic enzymes as vaccine antigens for giardiasis

Giardia lamblia is a leading protozoal cause of diarrheal disease worldwide. Infection is associated with abdominal pain, malabsorption and weight loss, and protracted post-infectious syndromes. A human vaccine is not available against G. lamblia. Prior studies with human and murine immune sera have identified several parasite antigens, including surface proteins and metabolic enzymes with intracellular functions. While surface proteins have demonstrated vaccine potential, they can exhibit significant variation between G. lamblia strains. By comparison, metabolic enzymes show greater conservation but their vaccine potential has not been established. To determine whether such proteins can serve as vaccine candidates, we focused on two enzymes, α-enolase (ENO) and ornithine carbamoyl transferase (OCT), which are involved in glycolysis and arginine metabolism, respectively. We show in a cohort of patients with confirmed giardiasis that both enzymes are immunogenic. Intranasal immunization with either enzyme antigen in mice induced strong systemic IgG1 and IgG2b responses and modest mucosal IgA responses, and a marked 100- to 1,000-fold reduction in peak trophozoite load upon oral G. lamblia challenge. ENO immunization also reduced the extent and duration of cyst excretion. Examination of 44 cytokines showed only minimal intestinal changes in immunized mice, although a modest increase of CCL22 was observed in ENO-immunized mice. Spectral flow cytometry revealed increased numbers and activation state of CD4 T cells in the small intestine and an increase in α4β7-expressing CD4 T cells in mesenteric lymph nodes of ENO-immunized mice. Consistent with a key role of CD4 T cells, immunization of CD4-deficient and Rag-2 deficient mice failed to induce protection, whereas mice lacking IgA were fully protected by immunization, indicating that immunity was CD4 T cell-dependent but IgA-independent. These results demonstrate that conserved metabolic enzymes can be effective vaccine antigens for protection against G. lamblia infection, thereby expanding the repertoire of candidate antigens beyond primary surface proteins.

Dissection of Barrier Dysfunction in Organoid-Derived Human Intestinal Epithelia Induced by Giardia duodenalis

BACKGROUND & AIMS

The protozoa Giardia duodenalis is a major cause of gastrointestinal illness worldwide, but underlying pathophysiological mechanisms remain obscure, partly due to the absence of adequate cellular models. We aimed at overcoming these limitations and recapitulating the authentic series of pathogenic events in the primary human duodenal tissue by using the human organoid system.

METHODS

We established a compartmentalized cellular transwell system with electrophysiological and barrier properties akin to duodenal mucosa and dissected the events leading to G. duodenalis-induced barrier breakdown by functional analysis of transcriptional, electrophysiological, and tight junction components.

RESULTS

Organoid-derived cell layers of different donors showed a time- and parasite load-dependent leak flux indicated by collapse of the epithelial barrier upon G. duodenalis infection. Gene set enrichment analysis suggested major expression changes, including gene sets contributing to ion transport and tight junction structure. Solute carrier family 12 member 2 and cystic fibrosis transmembrane conductance regulator-dependent chloride secretion was reduced early after infection, while changes in the tight junction composition, localization, and structural organization occurred later as revealed by immunofluorescence analysis and freeze fracture electron microscopy. Functionally, barrier loss was linked to the adenosine 3',5'-cyclic monophosphate (cAMP)/protein kinase A-cAMP response element-binding protein signaling pathway.

CONCLUSIONS

Data suggest a previously unknown sequence of events culminating in intestinal barrier dysfunction upon G. duodenalis infection during which alterations of cellular ion transport were followed by breakdown of the tight junctional complex and loss of epithelial integrity, events involving a cAMP/protein kinase A-cAMP response element-binding protein mechanism. These findings and the newly established organoid-derived model to study G. duodenalis infection may help to explore new options for intervening with disease and infection, in particular relevant for chronic cases of giardiasis.

A hybrid sequencing and assembly strategy for generating culture free Giardia genomes

Giardia duodenalis is a pathogenic intestinal protozoan parasite of humans and many other animals. Giardia duodenalis is found throughout the world, and infection is known to have adverse health consequences for human and other mammalian hosts. Yet, many aspects of the biology of this ubiquitous parasite remain unresolved. Whole genome sequencing and comparative genomics can provide insight into the biology of G. duodenalis by helping to reveal traits that are shared by all G. duodenalis assemblages or unique to an individual assemblage or strain. However, these types of analyses are currently hindered by the lack of available G. duodenalis genomes, due, in part, to the difficulty in obtaining the genetic material needed to perform whole genome sequencing. In this study, a novel approach using a multistep cleaning procedure coupled with a hybrid sequencing and assembly strategy was assessed for use in producing high quality G. duodenalis genomes directly from cysts obtained from feces of two naturally infected hosts, a cat and dog infected with assemblage A and D, respectively. Cysts were cleaned and concentrated using cesium chloride gradient centrifugation followed by immunomagnetic separation. Whole genome sequencing was performed using both Illumina MiSeq and Oxford Nanopore MinION platforms. A hybrid assembly strategy was found to produce higher quality genomes than assemblies from either platform alone. The hybrid G. duodenalis genomes obtained from fecal isolates (cysts) in this study compare favorably for quality and completeness against reference genomes of G. duodenalis from cultured isolates. The whole genome assembly for assemblage D is the most contiguous genome available for this assemblage and is an important reference genome for future comparative studies. The data presented here support a hybrid sequencing and assembly strategy as a suitable method to produce whole genome sequences from DNA obtained from G. duodenalis cysts which can be used to produce novel reference genomes necessary to perform comparative genomics studies of this parasite.

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Assemblage A and D genomes were generated directly from cysts isolated from feces.

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Genomes were sequenced using Illumina and Oxford Nanopore sequencing platforms.

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A hybrid sequencing/assembly strategy was used to generate G. duodenalis genomes.

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A hybrid strategy yields reference quality genomes from fecal isolates.

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These methods have generated the most contiguous Assemblage D genome to date.

High-fat diet increases the severity of Giardia infection in association with low-grade inflammation and gut microbiota dysbiosis

Exogenous factors that may influence the pathophysiology of Giardia infection remain incompletely understood. We have investigated the role of dietary fat in the pathogenesis of Giardia infection. Male 3 to 4-week-old C57BL/6 mice were fed either a low fat (LF) or a high fat (HF) diet for 12 days and challenged with G. duodenalis. In infected animals, the trophozoite burden was higher in HF + Giardia mice compared to the LF + Giardia group at day 7 post infection. Fatty acids exerted direct pro-growth effects on Giardia trophozoites. Analysis of disease parameters showed that HF + Giardia mice exhibited more mucosal infiltration by inflammatory cells, decreased villus/crypt ratios, goblet cell hyperplasia, mucus disruption, increased gut motility, and elevated fecal water content compared with LF + Giardia. HF diet-dependent exacerbation of Giardia-induced goblet cell hyperplasia was associated with elevated Atoh1 and Muc2 gene expression. Gut microbiota analysis revealed that the HF diet alone induces a taxonomic shift. HF + Giardia mice exhibited microbiota dysbiosis characterized by an increase of Firmicutes and a decrease of Bacteroidetes and significant changes in α- and β-diversity metrics. Taken together, the findings suggest that a HF diet exacerbates the outcome of Giardia infection. The data demonstrate that elevated dietary fat represents an important exogenous factor promoting the pathophysiology of giardiasis.

Age and Giardia intestinalis Infection Impact Canine Gut Microbiota

Giardia intestinalis is a flagellated protozoan responsible for giardiosis (also called giardiasis in humans), the most prevalent and widespread parasitic infection in humans and mammals worldwide. The intestinal microbiota is highly diverse and any alteration in its composition may impact on the health of the host. While studies on the mouse model of giardiosis described the role of the gut microbiota in host susceptibility to infection by the parasite, little is known about the gut microbiota during natural infections in dogs and particularly in puppies. In this study, we monitored naturally G. intestinalis-infected puppies for 3 months and quantified cyst excretion every 2 weeks. All puppies remained subclinically infected during the sampling period as confirmed by fecal examination. In parallel, we performed 16S Illumina sequencing of fecal samples from the different time points to assess the impact of G. intestinalis infection on gut microbiota development of the puppies, as well as gut health markers of immunity such as fecal IgA and calprotectin. Sequencing results revealed that the canine fecal microbiota of Giardia-infected puppies becomes more complex and less diverse with increasing age. In addition, significant differences in the structure of the microbiota were observed between puppies with high and low Giardia cyst excretion. Chronic subclinical G. intestinalis infection appears to be associated with some detrimental structural changes in the gut microbiota. G. intestinalis-associated dysbiosis is characterized by an enrichment of facultative anaerobic, mucus-degrading, pro-inflammatory species and opportunistic pathogens, as well as a reduction of Lactobacillus johnsonii at specific time points. Calprotectin levels increased with age, suggesting the establishment of chronic low-grade inflammation in puppies. Further work is needed to demonstrate whether these alterations in the canine gut microbiota could lead to a dysbiosis-related disease, such as irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD).

Unexpected organellar locations of ESCRT machinery in Giardia intestinalis and complex evolutionary dynamics spanning the transition to parasitism in the lineage Fornicata

BACKGROUND

Comparing a parasitic lineage to its free-living relatives is a powerful way to understand how that evolutionary transition to parasitism occurred. Giardia intestinalis (Fornicata) is a leading cause of gastrointestinal disease world-wide and is famous for its unusual complement of cellular compartments, such as having peripheral vacuoles instead of typical endosomal compartments. Endocytosis plays an important role in Giardia's pathogenesis. Endosomal sorting complexes required for transport (ESCRT) are membrane-deforming proteins associated with the late endosome/multivesicular body (MVB). MVBs are ill-defined in G. intestinalis, and roles for identified ESCRT-related proteins are not fully understood in the context of its unique endocytic system. Furthermore, components thought to be required for full ESCRT functionality have not yet been documented in this species.

RESULTS

We used genomic and transcriptomic data from several Fornicata species to clarify the evolutionary genome streamlining observed in Giardia, as well as to detect any divergent orthologs of the Fornicata ESCRT subunits. We observed differences in the ESCRT machinery complement between Giardia strains. Microscopy-based investigations of key components of ESCRT machinery such as GiVPS36 and GiVPS25 link them to peripheral vacuoles, highlighting these organelles as simplified MVB equivalents. Unexpectedly, we show ESCRT components associated with the endoplasmic reticulum and, for the first time, mitosomes. Finally, we identified the rare ESCRT component CHMP7 in several fornicate representatives, including Giardia and show that contrary to current understanding, CHMP7 evolved from a gene fusion of VPS25 and SNF7 domains, prior to the last eukaryotic common ancestor, over 1.5 billion years ago.

CONCLUSIONS

Our findings show that ESCRT machinery in G. intestinalis is far more varied and complete than previously thought, associates to multiple cellular locations, and presents changes in ESCRT complement which pre-date adoption of a parasitic lifestyle.

Prevalence and multi-locus genotyping of Giardia duodenalis in rabbits from Shaanxi province in northwestern China

Giardia duodenalis is an important parasite with veterinary and public health significance worldwide. The presence and zoonotic assemblages of G. duodenalis have previously been reported in rabbits. In this study, to understand the infection status of G. duodenalis in rabbits from Shaanxi province, a total of 537 fecal samples were collected from two breeds of rabbits in four age groups (<30 days, 31–90 days, 91–200 days and >200 days) from four geographical origins (Fengxiang, Yangling, Tongchuan, and Shanyang). The presence of G. duodenalis in these samples was assessed using molecular assays based on beta-giardin (bg). The glutamate dehydrogenase (gdh) and triosephosphate isomerase (tpi) loci were then amplified in the bg-positive samples for multi-locus genotype (MLG) analysis. The total prevalence of G. duodenalis in these rabbits was 3.54% (19/537). Giardia duodenalis infection was found in both breeds of rabbits, and in all farms and age groups, but with no statistically significant differences related to these factors (p > 0.05). Two assemblages, including B and E, were identified, with the former the predominant assemblage detected in both breeds, and in all age groups and farms. Sequence analysis revealed 2 (named as rbg1-2), 1 (named as rtpi1), and 2 (named as rgdh1-2) haplotypes at the gene loci of bg, tpi, and gdh, respectively, forming a multilocus genotype (MLG) of assemblage B (rbg1, rtpi1, and rgdh1). These findings reveal the significant zoonotic potential and genetic diversity of G. duodenalis in rabbits in Shaanxi Province, PR China.

Harmonization of Protocols for Multi-Species Organoid Platforms to Study the Intestinal Biology of Toxoplasma gondii and Other Protozoan Infections

The small intestinal epithelium is the primary route of infection for many protozoan parasites. Understanding the mechanisms of infection, however, has been hindered due to the lack of appropriate models that recapitulate the complexity of the intestinal epithelium. Here, we describe an in vitro platform using stem cell-derived intestinal organoids established for four species that are important hosts of Apicomplexa and other protozoa in a zoonotic context: human, mouse, pig and chicken. The focus was set to create organoid-derived monolayers (ODMs) using the transwell system amenable for infection studies, and we provide straightforward guidelines for their generation and differentiation from organ-derived intestinal crypts. To this end, we reduced medium variations to an absolute minimum, allowing generation and differentiation of three-dimensional organoids for all four species and the subsequent generation of ODMs. Quantitative RT-PCR, immunolabeling with antibodies against marker proteins as well as transepithelial-electrical resistance (TEER) measurements were used to characterize ODM's integrity and functional state. These experiments show an overall uniform generation of monolayers suitable for Toxoplasma gondii infection, although robustness in terms of generation of stable TEER levels and cell differentiation status varies from species to species. Murine duodenal ODMs were then infected with T. gondii and/or Giardia duodenalis, two parasites that temporarily co-inhabit the intestinal niche but have not been studied previously in cellular co-infection models. T. gondii alone did not alter TEER values, integrity and transcriptional abundance of tight junction components. In contrast, in G. duodenalis-infected ODMs all these parameters were altered and T. gondii had no apparent influence on the G. duodenalis-triggered phenotype. In conclusion, we provide robust protocols for the generation, differentiation and characterization of intestinal organoids and ODMs from four species. We show their applications for comparative studies on parasite-host interactions during the early phase of a T. gondii infection but also its use for co-infections with other relevant intestinal protozoans.

Giardia spp. and the Gut Microbiota: Dangerous Liaisons

Alteration of the intestinal microbiome by enteropathogens is commonly associated with gastrointestinal diseases and disorders and has far-reaching consequences for overall health. Significant advances have been made in understanding the role of microbial dysbiosis during intestinal infections, including infection with the protozoan parasite Giardia duodenalis, one of the most prevalent gut protozoa. Altered species composition and diversity, functional changes in the commensal microbiota, and changes to intestinal bacterial biofilm structure have all been demonstrated during the course of Giardia infection and have been implicated in Giardia pathogenesis. Conversely, the gut microbiota has been found to regulate parasite colonization and establishment and plays a critical role in immune modulation during mono and polymicrobial infections. These disruptions to the commensal microbiome may contribute to a number of acute, chronic, and post-infectious clinical manifestations of giardiasis and may account for variations in disease presentation within and between infected populations. This review discusses recent advances in characterizing Giardia-induced bacterial dysbiosis in the gut and the roles of dysbiosis in Giardia pathogenesis.

Molecular Epidemiology of Giardia Infections in the Genomic Era

Giardia duodenalis is a major gastrointestinal parasite of humans and animals across the globe. It is also of interest from an evolutionary perspective as it possesses many features that are unique among the eukaryotes, including its distinctive binucleate cell structure. While genomic analysis of a small number of isolates has provided valuable insights, efforts to understand the epidemiology of the disease and the population biology of the parasite have been limited by the molecular tools currently available. We review these tools and assess the impact of affordable and rapid genome sequencing systems increasingly being deployed in diagnostic settings. While these technologies have direct implications for public and veterinary health, they will also improve our understanding of the unique biology of this fascinating parasite.

Giardia duodenalis in humans and animals - Transmission and disease

Giardia duodenalis is a protozoan parasite infecting the upper intestinal tract of humans, as well as domestic and wild animals worldwide. Transmission of giardiasis occurs through the faecal-oral route, and may be either direct (i.e., person-to-person, animal-to-animal or zoonotic) or indirect (i.e., waterborne or foodborne). While asymptomatic infections are common in both humans and animals, a wide range of enteric symptoms have been reported, along with extra-intestinal and post-infectious complications. A definitive diagnosis of giardiasis is generally made by detection of cysts in stool specimens through microscopical examination of wet mounts, or through the use of permanent or fluorescent antibody stains. More recently, molecular methods have become popular for diagnosis and for testing environmental samples. Symptomatic giardiasis is often treated to reduce the duration of symptoms, to prevent complications, and to minimize transmission of the parasite to other hosts. Direct faecal-oral transmission of giardiasis can be largely controlled thorough improved hygiene and sanitation. In the case of waterborne transmission, a multiple barrier approach, including limiting access of people and animals to watersheds and reservoirs, and treatment using flocculation, filtration and disinfection, is necessary to minimize the risk. Since foodborne transmission is often associated with the consumption of fresh produce, a number of control measures can be taken during pre- and post-harvest, as well as at the food handler/consumer level to minimize the risk of contamination, or for removing or inactivating parasites. Good husbandry and farm management practices are important in controlling the spread of giardiasis in livestock and companion animals.

Update on Giardia: Highlights from the seventh International Giardia and Cryptosporidium Conference

Although Giardia duodenalis is recognized as one of the leading causes of parasitic human diarrhea in the world, knowledge of the mechanisms of infection is limited, as the pathophysiological consequences of infection remain incompletely elucidated. Similarly, the reason for and consequences of the very specific genome-organization in this parasite with 2 active nuclei is only partially known. Consistent with its tradition, the 7th International Giardia and Cryptosporidium Conference (IGCC 2019) was held from June 23 to 26, 2019, at the Faculty of Medicine and Pharmacy of the University of Rouen-Normandie, France, to discuss current research perspectives in the field. This renowned event brought together an international delegation of researchers to present and debate recent advances and identify the main research themes and knowledge gaps. The program for this interdisciplinary conference included all aspects of host-parasite relationships, from basic research to applications in human and veterinary medicine, as well as the environmental issues raised by water-borne parasites and their epidemiological consequences. With regard to Giardia and giardiasis, the main areas of research for which new findings and the most impressive communications were presented and discussed included: parasite ecology and epidemiology of giardiasis, Giardia-host interactions, and cell biology of Giardia, genomes and genomic evolution. The high-quality presentations discussed at the Conference noted breakthroughs and identified new opportunities that will inspire researchers and funding agencies to stimulate future research in a “one health” approach to improve basic knowledge and clinical and public health management of zoonotic giardiasis.