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Background There is significant need for accurate diagnostic tools for Cryptosporidium spp. and Giardia duodenalis infections in resource limited countries where diarrhoeal disease caused by these parasites is often prevalent. The present study assessed the diagnostic performance of three commercially available rapid diagnostic tests (RDTs) based on faecal-antigen detection for Cryptosporidium spp. and/or G. duodenalis infections in stool samples of children admitted with severe acute malnutrition (SAM) and diarrhoea. An established multiplex PCR was used as reference test. Methods Stool samples from children with SAM and diarrhoea enrolled in a randomized controlled trial (registered at clinicaltrials.gov/ct2/show/NCT02246296 ) in Malawi ( n =  175) and Kenya ( n =  120) between December 2014 and December 2015 were analysed by a multiplex PCR for the presence of Cryptosporidium spp. , G. duodenalis or Entamoeba histolytica parasite DNA. Cryptosporidium- positive samples were species typed using restriction fragment length polymorphism analysis. A sub-sample of the stool specimens ( n =  236) was used for testing with three different RDTs. Diagnostic accuracy of the tests under evaluation was assessed using the results of PCR as reference standard using MedCalc software. Pearson Chi-square test and Fisher’s exact test were used to determine (significant) difference between the number of cryptosporidiosis or giardiasis cases found by PCR in Malawi and Kenya. The overall diagnostic accuracy of each RDT was calculated by plotting a receiver operating characteristic (ROC) curve for each test and to determine the area under the curve (AUC) using SPSS8 software. Results Prevalence of Cryptosporidium spp. by PCR was 20.0 and 21.7% in Malawi and Kenya respectively, mostly C. hominis. G. duodenalis prevalence was 23.4 and 5.8% in Malawi and Kenya respectively. E. histolytica was not detected by PCR. RDT testing followed the same pattern of prevalence. RDT sensitivities ranged for cryptosporidiosis from 42.9 to 76.9% and for G. duodenalis from 48.2 to 85.7%. RDT specificities ranged from 88.4 to 100% for Cryptosporidium spp. and from 91.2 to 99.2% for G. duodenalis infections. Based on the estimated area under the curve (AUC) values, all tests under evaluation had an acceptable overall diagnostic accuracy (> 0.7), with the exception of one RDT for Cryptosporidium spp. in Malawi. Conclusions All three RDTs for Cryptosporidium spp. and Giardia duodenalis evaluated in this study have a moderate sensitivity, but sufficient specificity. The main value of the RDTs is within their rapidness and their usefulness as screening assays in surveys for diarrhoea.

Giardiasis, caused by Giardia duodenalis, is a leading cause of diarrhoea in resource-poor countries. To gain a better insight into the epidemiology of Giardia in Africa, we undertook a robust study to comprehend the distribution and prevalence of Giardia infection in humans, animals and their dispersal in the environment. Our protocol was registered with PROSPERO (registration number CRD42022317653). Deep literature search from 5 electronic databases, namely, AJOL, Google scholar, PubMed, ScienceDirect and Springer Link was performed using relevant keywords. Meta-analysis was performed using a random-effects model and heterogeneity among studies was evaluated using Cochran's Q and the I2-statistic. More than 500 eligible studies published from 1 January 1980 until 22 March 2022 were retrieved. In humans, exactly 48 124 Giardia spp. infection cases were registered from the 494 014 stool samples examined resulting in a pooled prevalence estimate (PPE) of 8.8% using microscopy. Whereas copro-antigen tests and molecular diagnostic methods generated PPE of 14.3 and 19.5%, respectively, with HIV+ subjects and those with diarrhoeatic stool having infection rates of 5.0 and 12.3%, respectively. The PPE of Giardia spp. infection in animals using molecular methods was 15.6%, which was most prevalent in pigs (25.2%) with Nigeria registering the highest prevalence at 20.1%. The PPE of Giardia spp. contamination from waterbodies was 11.9% from a total of 7950 samples which were detected using microscopy, with Tunisia documenting the highest infection rate of 37.3%. This meta-analysis highlights the necessity of ‘One Health’ approach for consolidated epidemiological studies and control of giardiasis in the African continent.

Giardia is a leading but treatable cause of infectious gastroenteritis worldwide, with a reported prevalence of 2-7% in high income countries and 2-30% in low income countries.1 Giardiasis is included in the World Health Organization Neglected Diseases Initiative owing to its burden and association with poverty.2 Its incidence in the United Kingdom is underestimated because of the lack of diagnostic sensitivity of traditional faecal microscopy3 and the mistaken belief that it is mostly acquired abroad, so often only people reporting foreign travel are tested. This update discusses the epidemiology, clinical presentation, diagnosis, and management of giardiasis specifically in high income countries. References

Human intestinal spirochaetosis is caused by the colonisation of the luminal membrane of the colon and rectum by anaerobic spirochaetes belonging to the genus Brachyspira. The common method used for its diagnosis is routine haematoxylin and eosin staining of colonic and rectal biopsy samples. The clinical spectrum of human intestinal spirochaetosis is heterogeneous, ranging from asymptomatic colonisation to symptoms such as chronic mucosal diarrhoea, rectal bleeding, and abdominal pain. In this Grand Round, we present a detailed report of the endoscopic and histological evaluation and clinical and therapeutic management of an immunocompetent patient with chronic watery diarrhoea caused by intestinal spirochaetosis followed by infection with Giardia lamblia. The initial histological picture mimicked other causes of chronic diarrhoea, such as inflammatory bowel disease, microscopic colitis, and eosinophilic enterocolitis, leading to a delay in diagnosis and treatment. A full course of metronidazole led to the remission of symptoms and to the complete eradication of pathogens as shown by the follow-up histological assessment. This case report highlights the need to consider intestinal spirochaetosis in the differential diagnosis of chronic watery diarrhoea, even when immunodeficiency or other probable risk factors are not present.

A fieldworker got more involved in research than intended when he contracted a Giardia duodenalis infection shortly after collecting faecal samples from wild Norwegian reindeer. Almost 50% of the reindeer samples showed heavy infections with G. duodenalis assemblage AI. Molecular comparison with the fieldworker’s infection revealed identical sequences at the loci successfully amplified. Although causality is inherently difficult to establish in wildlife-associated infections, the worker’s long history without previous infection, his intense exposure during sampling, absence of alternative known risk factors, and onset of symptoms consistent with exposure indicate that the reindeer samples were the most plausible source. These findings suggest a rare case of well-supported wildlife-associated Giardia transmission.

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.

Giardia duodenalis is a common gastrointestinal protozoan parasite, causing diarrheal illness in humans worldwide. Yet, the distribution of G. duodenalis genotypes among human patients and their clinical relevance remains controversial. This study aimed to detect G. duodenalis in children in Upper Egypt and identify causative genotypes and elucidate a possible correlation between genotype and clinical presentation. One hundred sixty-five children, regardless of symptoms, were tested for giardiasis. Giardia positive stool samples (40/165) were subjected to PCR amplification targeting the tpi gene with positive PCR results in only 35 cases (87.5%). Assemblage-specific amplification of genotypes (A, B, and the zoonotic E strains) revealed predominantly G. duodenalis Assemblage A (45.7%). Assemblage B and mixed A and B infections were detected in 31.4% and 22.8% of children, respectively. Assemblage E was not detected. G. duodenalis assemblage A was dominant in children who complained of diarrhea and abdominal cramps. In contrast, asymptomatic children with positive stool samples display a higher frequency of assemblage B and mixed infections. The study highlights the predominance of Giardia Assemblage A in our study locality. This study is the first for this endemic area to use the copro-PCR technique for diagnosis and genotyping of giardiasis. Study results show the value of simple species-specific primers for genotyping in communities with little access to laboratory resources. Further genetic studies are needed to clarify the association between parasite genetic diversity and patient symptomatology.

Background Giardiasis is recognized as the most prevalent enteric protozoal infection worldwide. Although gastrointestinal symptoms are the most common manifestations of giardiasis, several studies have reported cases of urticaria associated with this infection. Urticaria is a common mast cell-dependent disorder characterized by wheals, angioedema, or both. The aim of this study was to conduct the first systematic review to comprehensively synthesize the clinical, diagnostic, and therapeutic features of urticaria as a dermatologic manifestation in patients with giardiasis. Methods This review was conducted in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement. PubMed/MEDLINE, Web of Science, Scopus, ScienceDirect, and Google Scholar were searched without language restrictions up to 2025 to identify articles reporting patients with urticaria and giardiasis. Results Thirteen papers describing a total of 23 patients (14 males and 9 females, aged 4 to 56 years) were included. The locations of urticarial lesions varied, involving the head, trunk, and extremities. The duration of urticaria ranged from 8 h to 8 months. Other clinical manifestations reported in the patients included diarrhea, pruritus, abdominal distension, arthropathy, anorexia, headache, vomiting, abdominal pain, and dysphagia. Increased Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), elevated Immunoglobulin E (IgE), eosinophilia, stool examination, and Enzyme-linked immunosorbent assay (ELISA) were among the diagnostic tests utilized. Metronidazole, tinidazole, and quinacrine hydrochloride were the most commonly prescribed medications for treatment. Conclusions Our review highlights the diversity of clinical presentations and diagnostic approaches, and, for the first time, provides a consolidated resource for clinicians encountering this uncommon extraintestinal manifestation of giardiasis. In the initial evaluation of patients presenting with urticaria and a history of gastrointestinal symptoms, particularly those residing in areas with poor hygiene, potential exposure to contaminated water, or recent travel to such regions, parasitic infections, especially giardiasis, should be considered among the differential diagnoses. By addressing this under-recognized association, our study fills a significant knowledge gap regarding urticaria associated with giardiasis, ultimately facilitating earlier diagnosis, appropriate treatment, and improved patient prognosis.

The aims of this study were to verify the prevalence of Cryptosporidium spp. and Giardia spp. in animal feces and drinking water on dairy farms and to identify a possible relation between the exposure factors and the presence of these parasites. Fecal samples from cattle and humans and water samples were collected on dairy farms in Paraná, Brazil. Analysis of (oo)cysts in the feces was performed by the modified Ziehl-Neelsen staining and centrifugal flotation in zinc sulfate. Test-positive samples were subjected to nested PCR amplification of the 18SSU ribosomal RNA gene for identification of Cryptosporidium and Giardia and of the gp60 gene for subtyping of Cryptosporidium. Microbiological analysis of water was carried out by the multiple-tube method and by means of a chromogenic substrate, and parasitological analysis was performed on 31 samples by direct immunofluorescence and nested PCR of the genes mentioned above. Identification of the species of Cryptosporidium was performed by sequencing and PCR with analysis of restriction fragment length polymorphisms. The prevalence of Giardia and Cryptosporidium was higher in calves than in adults. Among the samples of cattle feces, Cryptosporidium parvum was identified in 41 (64%), C. ryanae in eight (12.5%), C. bovis in four (6.3%), C. andersoni in five (7.8%), and a mixed infection in 20 samples (31.3%). These parasites were not identified in the samples of human feces. Thermotolerant coliform bacteria were identified in 25 samples of water (45.5%). Giardia duodenalis and C. parvum were identified in three water samples. The gp60 gene analysis of C. parvum isolates revealed the presence of two strains (IIaA20G1R1 and IIaA17G2R2) in the fecal samples and one (IIaA17G2R1) in the water samples. The presence of coliforms was associated with the water source, structure and degradation of springs, rain, and turbidity. The prevalence of protozoa was higher in calves up to six months of age. C. parvum and G. duodenalis were identified in the water of dairy farms, as were thermotolerant coliforms; these findings point to the need for guidance on handling of animals, preservation of water sources, and water treatment.

Giardiasis is a common intestinal infection caused by Giardia duodenalis , which is a major economic and health burden for humans and livestock. Currently, a convenient and effective detection method is urgently needed. CRISPR/Cas12a-based diagnostic methods have been widely used for nucleic acid-based detection of pathogens due to their high efficiency and sensitivity. In this study, a technique combining CRISPR/Cas12a and RPA was established that allows the detection of G. duodenalis in faecal samples by the naked eye with high sensitivity (10 −1 copies/μL) and specificity (no cross-reactivity with nine common pathogens). In clinical evaluations, the RPA-CRISPR/Cas12a-based detection assay detected Giardia positivity in 2% (1/50) of human faecal samples and 47% (33/70) of cattle faecal samples, respectively, which was consistent with the results of nested PCR. Our study demonstrated that the RPA-CRISPR/Cas12a technique for G. duodenalis is stable, efficient, sensitive, specific and has low equipment requirements. This technique offers new opportunities for on-site detection in remote and poor areas.