Methods for the detection of Cryptosporidium and Giardia: From microscopy to nucleic acid based tools in clinical and environmental regimes

Prevalence and molecular characterization of Giardia duodenalis in companion dogs, domestic livestock and wildlife in the Jordan Basin, Israel

Giardiasis is a small intestinal disease caused by the zoonotic parasite, Giardia duodenalis. This study presents the molecular findings of G. duodenalis infection in companion dogs, domestic livestock and wildlife in the Northern Jordan Basin, Israel. Identification of G. duodenalis was accomplished by nested PCR (nPCR) targeting the 18S rRNA gene. Samples were collected from water (five samples from four sources of which one was recycled water), as well as feces from wolves (Canis lupus) (n = 34), jackals (Canis aureus) (n = 24), wild boars (Sus scrofa) (n = 40), cattle (Bos taurus) (n = 40), dogs (Canis lupus familiaris) (n = 37) and nutria (Mayocastor coypus) (n = 100). All positive samples were sequenced and a phylogenetic tree was drawn using the Bayesian Inference (BI) algorithm. Differences in G. duodenalis prevalence between the different hosts were analyzed by Pearson's chi-square (p < 0.05). Of the total 275 fecal samples, 36 were positive for G. duodenalis (13%). Frequency rates among different animal species was highest in wolves (32.3%), whilst rates in wild boars (22.5%), dogs (16.2%), cattle (12.5%) and jackals (4.2%), were observed to be significantly lower (p < 0.001). Three out of 5 recycled water (RW) samples were G. duodenalis positive. Three clusters with high posterior probabilities (PP) were found in the BI: Cluster 1: samples from wolves, wild boars, water and cattle together with database sequences of assemblages A, B and F, Cluster 2: samples from dogs, nutria and a jackal with sequences from assemblage D and Cluster 3: samples from cattle, wild boars, wolves and dogs with sequences from assemblage C and D. We suggest that wolves serve as reservoirs of G. duodenalis in this region. The finding of Giardia in RW suggests that this vehicle may further contaminate crops intended for human consumption as this water source is used for agricultural irrigation.

[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.

Genotyping and epidemiological distribution of diarrhea-causing isolates of Giardia duodenalis in southeastern part of West Bengal, India

The prevalence and genetic diversity of the protozoan pathogen Giardia duodenalis have been extensively studied worldwide. There is currently a lack of data regarding the genetic variability of the organism in eastern India. Understanding the circulating genotypes and associated risk factors is crucial for effective planning and implementing control measures. Therefore, the objective of the study was to conduct an epidemiological study to determine the prevalence and identify the various genotypes present. This survey adds to our knowledge on the occurrence and distribution of Giardia genotypes in the studied region. The overall prevalence was found to be 6.8%. This parasitic infection was significantly associated with two age groups, i.e., >0-5 years and >5-12 years. Using a multilocus genotyping method, we genotyped 52 human Giardia isolates that were obtained from diarrheal patients. Two distinct assemblages were found in the population-30.8% belonged to assemblage A; 63.5% belonged to assemblage B, prevalent in the population; and 5.7% belonged to a combined assemblage A+B. Sub-assemblage AII was found in 17.3% of the cases, followed by sub-assemblage AI (13.5%). High levels of genetic diversity were found within the population of assemblage B undergoing balancing selection. Overall, the high prevalence of the parasite observed, particularly among children, raises a major concern and necessitates implementation of robust control measures. Furthermore, we report the presence of numerous unique genotypes, circulating in this limited geographical boundary, which can be useful dataset for future studies.

Occurrence of gastrointestinal parasites in dogs in a rural area of Santa Catarina, Brazil

We investigated the occurrence of gastrointestinal parasites in dogs in rural areas of the municipality of Painel, Santa Catarina, Brazil. For this, 91 canine feces samples were collected from 82 farms between August, 2017 and January, 2018. These fecal materials were processed using the techniques of spontaneous sedimentation, centrifugation-floatation in zinc sulfate and Ziehl-Neelsen staining. A questionnaire in the form of an interview was administered to the dogs' owner and information about the farm and the main care provided for the dogs was obtained. Among 91 sampled dogs, 27 (29.7%) were positive for at least one parasite species. Ancylostoma was the most prevalent genus (16.5%), followed by Giardia duodenalis (14.3%), Trichuris vulpis (6.6%), Toxocara canis (5.5%), Entamoeba spp. (4.8%), Cryptosporidium spp. (3.3%) and Taeniidae (1.1%). Most dogs do not receive veterinarian care and rarely received antiparasitic treatment. They were free to roam and had free access to animal remains and garbage, which was reflected in the significant associations with the occurrence of parasites that were found. We conclude that rural dogs harbor gastrointestinal parasites, but that their owners are unaware of the risks that these parasites can bring to human health.

Absence of Giardia spp. in fecal samples from capybaras (Hydrochoerus hydrochaeris) inhabiting urban areas in the state of Mato Grosso do Sul, Brazil

Giardiasis is a major cause of diarrhea in humans and animals worldwide. Currently, there are nine species of Giardia, including Giardia duodenalis, which infects most vertebrates. The capybara (Hydrochoerus hydrochaeris) is the largest herbivorous rodent in the world. Although capybaras are hosts of several parasites of public health importance, including helminths and protozoa, there is a paucity of research on their zoonotic potential. We investigated the prevalence of Giardia spp. in populations of capybaras living in urban areas. Fecal samples from 247 capybaras were collected in Lagoa Maior, located in the municipality of Três Lagoas, and in Lago do Amor and Parque das Nações Indígenas, both located in the municipality of Campo Grande, state of Mato Grosso do Sul, Brazil. Fecal samples from capybaras originated from 133 adults (54%), 61 cubs (25%), and 53 juveniles (21%); 183 samples were collected in the rainy season and 64 in the dry season. Giardia spp. DNA was screened by the small-subunit ribosomal RNA (SSU rRNA) targeted PCR. Samples with DNA band sizes suggestive of Giardia spp. amplicons were examined by PCR targeting the glutamate dehydrogenase (GDH) and triosephosphate isomerase (TPI) genes. PCR amplicons were subjected to genetic sequencing. Nested PCR screening of the SSU rRNA gene revealed 16 samples showing faint DNA bands in gel electrophoresis with sizes similar to Giardia spp. amplicons. PCR amplicons of the SSU rRNA gene were analyzed by Sanger sequencing. Most of the sequencing reactions failed, and the chromatogram reads of some samples were ambiguous, suggesting nonspecific amplification. Therefore, all the capybara fecal samples were considered negative for Giardia spp. Two published studies on Giardia spp. in capybaras reported findings similar to ours, i.e., the absence or a low positivity rate for Giardia spp. However, further studies are needed to determine the possible role of capybaras in the epidemiology of giardiasis.

Comparative study of a broad qPCR panel and centrifugal flotation for detection of gastrointestinal parasites in fecal samples from dogs and cats in the United States

BACKGROUND

For decades, zinc sulfate centrifugal fecal flotation microscopy (ZCF) has been the mainstay technique for gastrointestinal (GI) parasite screening at veterinary clinics and laboratories. Elsewhere, PCR has replaced microscopy because of generally increased sensitivity and detection capabilities; however, until recently it has been unavailable commercially. Therefore, the primary aim of this study was to compare the performance of real-time PCR (qPCR) and ZCF for fecal parasite screening. Secondary aims included further characterization of markers for hookworm treatment resistance and Giardia spp. assemblages with zoonotic potential and qPCR optimization.

METHODS

A convenience sampling of 931 canine/feline fecal samples submitted to a veterinary reference laboratory for routine ZCF from the Northeast US (11/2022) was subsequently evaluated by a broad qPCR panel following retention release. Detection frequency and agreement (kappa statistics) were evaluated between ZCF and qPCR for seven GI parasites [hookworm/(Ancylostoma spp.), roundworm/(Toxocara spp.), whipworm/(Trichuris spp.), Giardia duodenalis, Cystoisospora spp., Toxoplasma gondii, and Tritrichomonas blagburni] and detections per sample. Total detection frequencies were compared using a paired t-test; positive sample and co-infection frequencies were compared using Pearson's chi-squared test (p ≤ 0.05 significant) and qPCR frequency for hookworm benzimidazole (BZ) resistance (F167Y) and zoonotic Giardia spp. assemblage markers calculated. Confirmatory testing, characterization, and qPCR optimization were carried out with Sanger sequencing.

RESULTS

qPCR detected a significantly higher overall parasite frequency (n = 679) compared to ZCF (n = 437) [p =  < 0.0001, t = 14.38, degrees-of-freedom (df) = 930] and 2.6 × the co-infections [qPCR (n = 172) vs. ZCF (n = 66)], which was also significant (p =  < 0.0001, X2 = 279.49; df = 1). While overall agreement of parasite detection was substantial [kappa = 0.74; (0.69-0.78], ZCF-undetected parasites reduced agreement for individual and co-infected samples. qPCR detected markers for Ancylostoma caninum BZ resistance (n = 5, 16.1%) and Giardia with zoonotic potential (n = 22, 9.1%) as well as two parasites undetected by ZCF (T. gondii/T. blagburni). Sanger sequencing detected novel roundworm species, and qPCR optimization provided detection beyond ZCF.

CONCLUSIONS

These results demonstrate the statistically significant detection frequency advantage offered by qPCR compared to routine ZCF for both single and co-infections. While overall agreement was excellent, this rapid, commercially available qPCR panel offers benefits beyond ZCF with detection of markers for Giardia assemblages with zoonotic potential and hookworm (A. caninum) BZ resistance.

Biosensors as early warning detection systems for waterborne Cryptosporidium

Waterborne disease is a global health threat contributing to a high burden of diarrhoeal disease, and growing evidence indicates a prospective increase in incidence coinciding with the profound effects of climate change. A major causative agent of gastrointestinal disease is Cryptosporidium, a protozoan waterborne parasite identified in over 70 countries. Cryptosporidium is a cause of high disease morbidity in children and the immunocompromised with limited treatment options for patients at risk of severe illness. The hardy nature of the organism leads to its persistence in various water sources, with certain water treatment procedures proving inefficient for its complete removal. While diagnostic methods for Cryptosporidium are well-defined in the clinical sphere, detection of Cryptosporidium in water sources remains suboptimal due to low dispersion of organisms in large sample volumes, lengthy processing times and high costs of equipment and reagents. A need for improvement exists to identify the organism as an emerging threat in domestic water systems, and the technological advantages that biosensors offer over current analytical methods may provide a preventative approach to outbreaks of Cryptosporidium. Biosensors are innovative, versatile and adaptable analytical tools that could provide highly sensitive, rapid, on-site analysis needed for Cryptosporidium detection in low-resource settings.

Molecular detection and characterization of Cryptosporidium spp., Giardia duodenalis, and Enterocytozoon bieneusi infections in dromedary camels (Camelus dromedaries) in Egypt

Introduction

Few studies have investigated the occurrence of microeukaryotic gut parasites in dromedary camels in Egypt, and the majority of these investigations are based on microscopic analysis of fecal material.

Methods

Herein, we assessed the occurrence, molecular diversity, and zoonotic potential of protozoan (Cryptosporidium spp. and Giardia duodenalis) and microsporidian (Enterocytozoon bieneusi) pathogens in individual fecal samples (n = 102) of dromedary camels with (n = 26) and without (n = 76) diarrhea from Aswan Governorate, Upper Egypt. Other factors possibly associated with an increased risk of infection (geographical origin, sex, age, and physical condition) were also analyzed. The SSU rRNA or ITS genes were targeted by molecular (PCR and Sanger sequencing) techniques for pathogen detection and species identification.

Results and discussion

The most abundant species detected was G. duodenalis (3.9%, 4/102; 95% CI: 1.1-9.7), followed by Cryptosporidium spp. (2.9%, 3/102; 95% CI: 0.6-8.4). All samples tested negative for the presence of E. bieneusi. Sequence analysis data confirmed the presence of zoonotic C. parvum (66.7%, 2/3) and cattle-adapted C. bovis (33.3%, 1/3). These Cryptosporidium isolates, as well as the four Giardia-positive isolates, were unable to be amplified at adequate genotyping markers (Cryptosporidium: gp60; Giardia: gdh, bg, and tpi). Camels younger than 2 years old were significantly more likely to harbor Cryptosporidium infections. This connection was not statistically significant, although two of the three cryptosporidiosis cases were detected in camels with diarrhea. The spread of G. duodenalis infections was unaffected by any risk variables studied. This is the first report of C. parvum and C. bovis in Egyptian camels. The finding of zoonotic C. parvum has public health implications since camels may function as sources of oocyst pollution in the environment and potentially infect livestock and humans. Although preliminary, this study provides useful baseline data on the epidemiology of diarrhea-causing microeukaryotic parasites in Egypt. Further research is required to confirm and expand our findings in other animal populations and geographical regions of the country.

Enteric protozoal infections in camels: Etiology, epidemiology, and future perspectives

Camels have great potential as a safety valve for current and future food security for pastoralists, agropastoralists, and urban populations. Enteric protozoal diseases are important causes of economic losses in camels; however, they are poorly concerned globally. The most common members of enteric protozoa are Balantidium, Eimeria, Giardia, and Cryptosporidium. Some of them threaten human health as humans can be infected by consuming food or water contaminated with camel feces, particularly in poor communities with inadequate sanitation and low-quality healthcare facilities. For these reasons, a comprehensive and careful investigation was conducted on some enteric protozoal diseases of camels to present an updated insight into the etiology, epidemiology, and future trends in diagnosing and controlling camel enteric protozoa. Future studies on the camel enteric protozoa should be carried out to develop advanced diagnostic approaches in diverse farm animal species. Moreover, the protozoan zoonotic potential should be considered to secure human health.

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.

Diagnosis and control of cryptosporidiosis in farm animals

Cryptosporidium is a pathogenic protozoan parasite infecting the gastrointestinal epithelium of human and animal hosts. In farm animals, cryptosporidiosis causes significant economic losses including deaths in newborn animals, retarded growth, increased labor involved and high cost of drugs. The detection of Cryptosporidium oocysts in fecal samples is traditionally dependent on examination of stained slides by light microscope or by advanced microscopical tools such as: electron microscopy and phase contrast microscopy. Immunological diagnosis using either antibody or antigen detection could offer high sensitivity and specificity. Examples for these tests are Enzyme Linked Immunosorbent Assay (ELISA), Immunochromatographic tests, Immunochromatographic lateral flow (ICLF), Immunofluorescence assays (IFA) and Flow cytometry coupled with cell sorting. Molecular methods could differentiate species and genotypes of Cryptosporidium and help in studying the epidemiological features of this parasite with rapid, simple and sensitive procedures. Nanotechnology-based platforms could improve the sensitivity and specificity of other detection methods like: ELISA, ICLF, IFA and polymerase chain reaction. As the available prophylactic and therapeutic drugs or natural products treatments are insufficient and no approved vaccines are available, the best approach to control this parasite is by following firm hygienic measures. Many vaccine attempts were performed using hyperimmune colostrum, live or attenuated vaccines, recombinant and Deoxyribonucleic acid vaccines. Also, Clustered Regularly Interspaced Short Palindromic Repeats/Cas9 technology could help in Cryptosporidium genome editing to improve drug and vaccine discovery. Another approach that could be useful for assigning drug targets is metabolomics. Probiotics were also used successfully in the treatment of acute diarrhea and they proved a limiting effect on cryptosporidiosis in animal models. In addition, nanotherapy-based approaches could provide a good strategy for improving the potency of any type of drugs against Cryptosporidium and give good anti-cryptosporidial effects. In conclusion, accurate diagnosis using advanced techniques is the key to the control and prevention of cryptosporidiosis.

Burden and Epidemiology of Human Intestinal Giardia duodenalis Infection in Colombia: A Systematic Review

The genus Giardia is a unicellular protozoan able to parasitize both humans and animals. Cysts of Giardia can be found in soil samples, aquatic environments, food, and any surface that gets in contact with the feces of parasitized animals. The aim of this systematic review was to analyze the burden and epidemiology of Giardia infection in Colombia summarizing recent scientific reports and existing knowledge and to identify knowledge gaps that may be addressed in future investigations. This work follows the guidelines established by "Preferred Reporting Items for Systematic Reviews and Meta-Analyzes" (PRISMA). Published scientific literature from 1 January 2010 to 18 September 2022 was searched in six electronic scientific databases using the search terms: "Giardia" OR "Giardiasis" AND "Colombia". Twenty-three scientific articles were performed in 22 departments of Colombia at rural, urban, and a combination of rural and urban contexts. The prevalence of Giardia in the Colombian population was between 0.9 and 48.1% when the samples were analyzed with classical microscopy; the range of Giardia prevalence was even bigger (4.2-100%) when qPCR and nested PCR were used. The dominant Giardia assemblages found in Colombia were A and B, and most frequent subassemblages were AII, BIII, and BIV.

Development and Preliminary Evaluation of a Nanoparticle-Assisted PCR Assay for the Detection of Cryptosporidium parvum in Calves

C. parvum is an important diarrheal pathogen in humans and animals, especially in young hosts. To accurately and rapidly detect C. parvum infection in calves, we established a nano-PCR assay targeting the cgd3_330 gene for the specific detection of C. parvum. This nano-PCR assay was ten times more sensitive than that of the normal PCR assay by applying the same primers and did not cross-react with C. andersoni, C. bovis, C. ryanae, Balantidium coli, Enterocytozoon bieneusi, Giardia lamblia, and Blastocystis sp. To further test the nano-PCR in clinical settings, a total of 20 faecal samples from calves were examined by using the nano-PCR, the normal PCR, and the nested PCR assays. The positive rates were 30% (6/20), 30% (6/20), and 25% (5/20) for the nano-PCR, the normal PCR, and the nested PCR assays, respectively, indicating that the nano-PCR and the normal PCR assays had the same positive rate (30%). Taken together, the present study could provide a candidate method for the specific detection of C. parvum infection in calves in clinical settings.

Working toward improved monitoring of Cryptosporidium and Giardia (oo)cysts in water samples: testing alternatives to elution and immunomagnetic separation from USEPA Method 1623.1

OBJECTIVE

This study was designed to find a method to enhance the recovery of Cryptosporidium spp. and Giardia spp. parasites from water samples for research purposes compared to the results that can be achieved with USEPA Method 1623.1. Four different approaches were used to test water samples that were artificially spiked with parasites. The approaches were: (i) Method 1623.1 itself, (ii) elution of Method 1623.1 combined with microfiltration, (iii) an elution technique based on grinding the filter membrane in a blender before the eluent was concentrated by immunomagnetic separation, and (iv) the blender elution followed by microfiltration. Fluorescence microscopy was used to determine which approach led to the highest parasite recovery rates.

RESULTS

Method 1623.1 gave the best results for Giardia, while all four approaches were statistically equivalent for Cryptosporidium. We evaluated the costs and laboratory time requirements for each protocol to give readers a complete comparison of the methods tested. Elution of Method 1623.1 combined with microfiltration resulted in lower costs and less laboratory work time without compromising the recovery of the parasites.

A Simple Alcohol-based Method of Oocyst Inactivation for Use in the Development of Detection Assays for Cryptosporidium

Cryptosporidium spp. are obligate, intracellular parasites that cause life-threatening diarrhea among children and immunocompromised adults. Transmission occurs by the fecal-oral route following ingestion of thick-walled oocysts that can contaminate, persist, and resist disinfection in water and food. Sodium hypochlorite, peroxides, ozone, formaldehyde, and ammonia are suitable disinfectants against Cryptosporidium oocysts. Effective concentrations of these chemicals can be toxic and not practical for downstream research use of non-viable oocysts. Oocyst inactivation approaches such as UV light, heat, and treatments with ethanol or methanol are generally more accessible for routine lab use, yet their applicability in Cryptosporidium assay development is limited. The aims of this study were to evaluate methods of inactivation of Cryptosporidium oocysts that can be readily applied in the laboratory and test the utility of whole inactive oocysts in quantitative PCR (qPCR). Experiments were performed on C. parvum oocysts subjected to heat (75 °C/10 min) or treated with increasing concentrations of ethanol and methanol over time. Viability assays based on propidium iodide (PI) staining, in vitro excystation, and infection of the Hct-8 cell line were used to evaluate the efficacies of the treatments. Excystation of sporozoites was not impaired with 24 h exposures of oocysts to 50% ethanol or methanol, even though significant PI incorporation was observed. Concentrations of ≥70% of these chemicals were required to completely inhibit excystation and infection of Hct-8 cells in vitro. Inactivated oocysts stored for up to 30 days at 4 °C retained cyst wall integrity and antigenicity as observed by light microscopy and immunofluorescence. Moreover, non-viable oocysts applied directly in qPCR assays of the COWP gene were useful reference reagents for the identification and quantification of Cryptosporidium in spiked water samples. In summary, we have established a practical approach to inactivate C. parvum oocysts in the laboratory that is suitable for the development of detection or diagnostic assays targeting the parasite.

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Disinfectant-based inactivation of oocysts is not feasible for assay development.

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Inactivation methods that retain antigen and nucleic acid integrity are limited.

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Alcohol-inactivated oocysts are suitable as reference reagents in qPCR.

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We present a method to effectively inactivate oocysts and retain assayable properties.

A comparison of assays for the detection of Cryptosporidium parvum in the feces of scouring calves

Cryptosporidium parvum is a zoonotic, protozoan parasite that causes potentially life-threatening diarrhea in the host and can be transmitted via the fecal-oral route. C. parvum can infect cattle and may be detected in their feces using a variety of tests. We compared the level of agreement, ease of procedure, and cost among PCR, lateral flow immunoassay, fluorescent antibody, and Kinyoun acid-fast stain direct smear tests. Over the course of 9 mo, 74 calf fecal samples were submitted and tested for C. parvum using all 4 tests. A Fleiss kappa value of 0.813 was obtained, indicating an excellent level of agreement among tests. Overall, the best test based on cost and ease of procedure was the Kinyoun acid-fast stain direct smear.

Waterborne protozoan outbreaks: An update on the global, regional, and national prevalence from 2017 to 2020 and sources of contamination

The aim of this review is to identify the worldwide trend of waterborne protozoan outbreaks and how it varies between geographic regions during the period from 2017 to 2020. Data about waterborne protozoan outbreaks were gathered and stratified by continent, country, water source, and protozoan species associated with the outbreak. The highest prevalence of waterborne protozoan outbreaks was reported in developed countries. Out of 251 outbreaks reported worldwide during the studied period, 141, 51 and 24 outbreaks were recorded in the USA, UK, and New Zealand, respectively. These outbreaks were mainly associated with Cryptosporidium (192 outbreaks) and Giardia (48 outbreaks). Cyclospora cayetanensis, Dientamoebafragilis and Toxoplasma gondii were associated with 7 outbreaks. One outbreak was associated with each of Blastocystis hominis, Entamoeba histolytica, Microsporidia or Naegleria fowleri. This data suggests large discrepancies in the number of outbreaks reported between geographic regions, with most outbreaks recorded in developed countries. Differences in the prevalence of outbreaks between countries are likely attributed to the availability of diagnostic capabilities and surveillance programs to monitor water contamination with pathogenic protozoa. More attention and concerted efforts are required to improve water safety and to alleviate the impact of waterborne protozoan infections. Appropriate surveillance of water contamination with protozoa can enable public health officials to identify source of contamination and implement the necessary measures to limit transmission and prevent outbreaks.

Comprehensive review of conventional and state-of-the-art detection methods of Cryptosporidium

Cryptosporidium is a critical waterborne protozoan pathogen found in water resources that have been a major cause of death and serious illnesses worldwide, costing millions of dollars annually for its detection and treatment. Over the past several decades, substantial efforts have been made towards developing techniques for the detection of Cryptosporidium. Early diagnostic techniques were established based on the existing tools in laboratories, such as microscopes. Advancements in fluorescence microscopy, immunological, and molecular techniques have led to the development of several kits for the detection of Cryptosporidium spp. However, these methods have several limitations, such as long processing times, large sample volumes, the requirement for bulky and expensive laboratory tools, and the high cost of reagents. There is an urgent need to improve these existing techniques and develop low-cost, portable and rapid detection tools for applications in the water quality industry. In this review, we compare recent advances in nanotechnology, biosensing and microfluidics that have facilitated the development of sophisticated tools for the detection of Cryptosporidium spp.Finally, we highlight the advantages and disadvantages, of these state-of-the-art detection methods compared to current analytical methodologies and discuss the need for future developments to improve such methods for detecting Cryptosporidium in the water supply chain to enable real-time and on-site monitoring in water resources and remote areas.

Is the Medium Still the Message? Culture-Independent Diagnosis of Gastrointestinal Infections

Infectious diarrhea is caused by a variety of pathogens, including viruses, bacteria, and parasitic organisms. Though the causative agent of diarrhea has historically been evaluated via stool cultures, recently, culture-independent diagnostic tests (CIDT) have been developed and utilized with increasing frequency. Current practice guidelines recommend their use as adjuncts to stool cultures for diagnosing acute and chronic diarrhea. The three principal CIDT are microscopy, enzyme-based immunoassays (EIAs), and molecular based polymerase chain reaction (PCR). This review explores the common causes of infectious diarrhea, the basics of stool culture, the diagnostic utility of these three culture-independent modalities, and the strengths and weaknesses of all currently available clinical techniques. It also outlines considerations for specific populations including returning travelers and those with inflammatory bowel disease.

Portable on-chip colorimetric biosensing platform integrated with a smartphone for label/PCR-free detection of Cryptosporidium RNA

Cryptosporidium, a protozoan pathogen, is a leading threat to public health and the economy. Herein, we report the development of a portable, colorimetric biosensing platform for the sensitive, selective and label/PCR-free detection of Cryptosporidium RNA using oligonucleotides modified gold nanoparticles (AuNPs). A pair of specific thiolated oligonucleotides, complementary to adjacent sequences on Cryptosporidium RNA, were attached to AuNPs. The need for expensive laboratory-based equipment was eliminated by performing the colorimetric assay on a micro-fabricated chip in a 3D-printed holder assembly. A smartphone camera was used to capture an image of the color change for quantitative analysis. The detection was based on the aggregation of the gold nanoparticles due to the hybridization between the complementary Cryptosporidium RNA and the oligonucleotides immobilized on the AuNPs surface. In the complementary RNA's presence, a distinctive color change of the AuNPs (from red to blue) was observed by the naked eye. However, in the presence of non-complementary RNA, no color change was observed. The sensing platform showed wide linear responses between 5 and 100 µM with a low detection limit of 5 µM of Cryptosporidium RNA. Additionally, the sensor developed here can provide information about different Cryptosporidium species present in water resources. This cost-effective, easy-to-use, portable and smartphone integrated on-chip colorimetric biosensor has great potential to be used for real-time and portable POC pathogen monitoring and molecular diagnostics.

CRISPR/Cas12a-powered immunosensor suitable for ultra-sensitive whole Cryptosporidium oocyst detection from water samples using a plate reader

Waterborne pathogens, such as Cryptosporidium parvum, pose a major threat to public health globally, and this requires screening of drinking and environmental water for low number of contaminating microbes. However, current detection approaches generally require trained experts with sophisticated instruments, and are not suitable for large-scale screening and rapid outbreak response. Recent advances in ultrasensitive CRISPR/Cas-based biosensing continue to expand the range of detectable molecular targets, however single microbes could not be directly detected so far, especially in environmental samples. Here, we report an ultrasensitive CRISPR/Cas12a-powered immunosensing method suitable for microbial detection which links antibody-based recognition with CRISPR/Cas12a-based fluorescent signal amplification through an antibody-DNA conjugate. This approach is shown here to detect whole 4 µm size Cryptosporidium parvum oocysts with a linear range from 6.25 - 1600 oocysts/mL, at a maximum sensitivity of single oocyst per sample. Its potential to apply to various complex sample matrices has also been demonstrated. After sample dilution by factor of 10, we were able to detect 10 oocysts from a back-wash mud samples from water treatment plate. This method uses the same experimental setup (plate reader) as a conventional ELISA assay thus reducing the need for microscopy-based identification of Cryptosporidium, which represents the gold-standard but requires high level expertise and time-consuming manual counting. This work highlights the potential of CRISPR/Cas-based biosensing for water quality assessment and ultrasensitive whole pathogen detection.

A review on application of next-generation sequencing methods for profiling of protozoan parasites in water: Current methodologies, challenges, and perspectives

The advancement in metagenomic techniques has provided novel tools for profiling human parasites in environmental matrices, such as water and wastewater. However, application of metagenomic techniques for the profiling of protozoan parasites in environmental matrices is not commonly reported in the literature. The key factors leading to the less common use of metagenomics are the complexity and large eukaryotic genome, the prevalence of small parasite populations in environmental samples compared to bacteria, difficulties in extracting DNA from (oo)cysts, and limited reference databases for parasites. This calls for further research to develop optimized methods specifically looking at protozoan parasites in the environment. This study reviews the current workflow, methods and provide recommendations for the standardization of techniques. The article identifies and summarizes the key methods, advantages, and limitations associated with metagenomic analysis, like sample pre-processing, DNA extraction, sequencing approaches, and analysis methods. The study enhances the understanding and application of standardized protocols for profiling of protozoan parasite community from highly complexe samples and further creates a resourceful comparison among datasets without any biases.

Comparative Performance of Eight PCR Methods to Detect Cryptosporidium Species

Diagnostic approaches based on PCR methods are increasingly used in the field of parasitology, particularly to detect Cryptosporidium. Consequently, many different PCR methods are available, both “in-house” and commercial methods. The aim of this study was to compare the performance of eight PCR methods, four “in-house” and four commercial methods, to detect Cryptosporidium species. On the same DNA extracts, performance was evaluated regarding the limit of detection for both C. parvum and C. hominis specificity and the ability to detect rare species implicated in human infection. Results showed variations in terms of performance. The best performance was observed with the FTD^® Stool parasites method, which detected C. parvum and C. hominis with a limit of detection of 1 and 10 oocysts/gram of stool respectively; all rare species tested were detected (C. cuniculus, C. meleagridis, C. felis, C. chipmunk, and C. ubiquitum), and no cross-reaction was observed. In addition, no cross-reactivity was observed with other enteric pathogens. However, commercial methods were unable to differentiate Cryptosporidium species, and generally, we recommend testing each DNA extract in at least triplicate to optimize the limit of detection.

Global epidemiology of Giardia duodenalis infection in cancer patients: a systematic review and meta-analysis

Background

Application of chemotherapeutics in cancer patients may provide an immunosuppressive milieu, favourable for parasitic infections. Giardia duodenalis is an important zoonotic intestinal parasite responsible for diarrhoea in humans worldwide.

Methods

The present systematic review and meta-analysis was conducted to estimate the prevalence of G. duodenalis and respective odds ratios (ORs) in cancer patients around the globe. Four online databases—PubMed, Scopus, Web of Science and Google Scholar—were carefully explored for relevant literature without time limitation until 28 November 2020. Meta-analysis was done based on a random effects model to pool the estimations and define 95% confidence intervals (CIs).

Results

The overall weighted prevalence of G. duodenalis infection in cancer patients was calculated to be 6.9% (95% CI 0.5 to 9.3) globally, based on data from 32 studies. Although not statistically significant, eight case–control studies revealed that cancer patients were 1.24 times (95% CI 0.66 to 2.31; p=0.501) more exposed to G. duodenalis infection than healthy controls. Moreover, the prevalence of infection was not significantly associated with quantitative variables, including publication year (regression coefficient −0.0135, p=0.578), sample size (regression coefficient −0.0007, p=0.074) and human development index (regression coefficient −1.6263, p=0.419). Also, subgroup analysis of the pooled G. duodenalis infection was performed for publication year, World Health Organization regions, countries, continents, cancer types and country income.

Conclusions

Altogether, the epidemiology of G. duodenalis infection and its associated risk factors in immunocompromised individuals, especially cancer patients, is still open to question and deserves comprehensive investigations.

Establishment and preliminary application of nanoparticle-assisted PCR assay for detection of Cryptosporidium spp

Cryptosporidium is an important intestinal protozoan parasite that causes diarrhoea in humans and animals. To rapidly and specifically detect Cryptosporidium spp., we designed a pair of primers based on the small subunit ribosomal RNA (SSU rRNA) gene of Cryptosporidium spp. to be used in a new nanoparticle-assisted PCR (nano-PCR) assay. The minimum detectable concentration (1.02 pg) of this nano-PCR was 10 times more sensitive than conventional PCR using the same primer pair. The DNA samples of C. parvum, C. baileyi, C. xiaoi, C. ryanae, and C. andersoni were successfully detected by the nano-PCR. No amplifications were evident with DNA samples of some common intestinal pathogens, including Eimeria tenella, Blastocystis sp., Giardia lamblia, Enterocytozoon bieneusi, and Balantidium coli. To validate the clinical usefulness of the novel nano-PCR, a total of 40 faecal samples from goats, camels, calves, and chickens were examined. The positive rate of Cryptosporidium spp. was 27.5% (11/40), which was consistent with that of an established nested PCR. These results indicate that the novel nano-PCR assay enables the rapid, specific, and accurate detection of Cryptosporidium infection in animals. The findings provide a technical basis for the clinical diagnosis, prevention, and control of cryptosporidiosis.

FELINE GIARDIASIS IN TURKEY: PREVALENCE AND GENETIC AND HAPLOTYPE DIVERSITY OF GIARDIA DUODENALIS BASED ON THE β-GIARDIN GENE SEQUENCE IN SYMPTOMATIC CATS

Giardia duodenalis is a common zoonotic protozoan parasite with a broad host distribution. The main objectives of the present study were to determine the prevalence of giardiasis and to reveal the genetic and haplotype diversity of G. duodenalis in symptomatic cats in Turkey. Fecal samples were collected from cats (n = 102) with diarrhea that were admitted to different pet clinics in the Central Anatolia region of Turkey. All samples were analyzed by microscopic examination (ME), rapid immunochromatographic test (ICT), and PCR targeting the β-giardin (bg) loci of the parasite. Phylogenetic, haplotype, and network analyses of G. duodenalis based on the bg gene were carried out. Overall, G. duodenalis was detected in 70/102 (68.6%) of the cats with diarrhea by ME (38/102, 37.3%), ICT (51/102, 50%), and PCR (30/102, 29.4%). According to sequence analyses of the bg gene region, all isolates were identified as G. duodenalis assemblage B. Haplotype analyses revealed 2 known and 8 novel haplotypes for G. duodenalis assemblage B. This study provides first prevalence and genetic and haplotype diversity data on G. duodenalis assemblage B from cats in Turkey.

Cryptosporidium species and subtypes in river water and riverbed sediment using next-generation sequencing

This study uncovered the prevalence, harboured species, and subtype diversity of Cryptosporidium species in river water and its sediment from the Apies River in South Africa. Cryptosporidium spp. concentrations in freshwater and its sediment were determined using Ziehl-Neelsen staining and quantitative Polymerase Chain Reaction (qPCR) techniques. Next-generation sequencing (NGS) targeting the 60 kDa glycoprotein (gp60) gene of Cryptosporidium spp. was performed to reveal the species, subtype families and subtypes harboured in freshwater and its sediment. Although the results revealed that water samples had a higher prevalence (30%) compared with sediment (28%), the number of observable Cryptosporidium spp. oocysts in sediment samples (ranging from 4.90 to 5.81 log₁₀ oocysts per 1 Liter) was higher than that of river water samples (ranging from 4.60 to 5.58 log₁₀ oocysts per 1 L) using Ziehl-Neelsen staining. The 18S ribosomal ribonucleic acid (rRNA) gene copy of Cryptosporidium in riverbed sediments ranged from 6.03 to 7.65 log₁₀, whereas in river water, it was found to be between 4.20 and 6.79 log₁₀. Subtyping results showed that in riverbed sediments, Cryptosporidium parvum accounted for 40.72% of sequences, followed by Cryptosporidium hominis with 23.64%, Cryptosporidium cuniculus with 7.10%, Cryptosporidium meleagridis with 4.44% and the least was Cryptosporidium wrairi with 2.59%. A considerable percentage of reads in riverbed sediment (21.25%) was not assigned to any subtype. River water samples had 45.63% of sequences assigned to C. parvum, followed by 30.32% to C. hominis, 17.99% to C. meleagridis and 5.88% to C. cuniculus. The data obtained are concerning, as Cryptosporidium spp. have intrinsic resistance to water treatment processes and low infectious doses, which can pose a risk to human health due to the various uses of water (for human consumption, leisure, and reuse).

A review of Cryptosporidium spp. and their detection in water

Cryptosporidium spp. are one of the most important waterborne pathogens worldwide and a leading cause of mortality from waterborne gastrointestinal diseases. Detection of Cryptosporidium spp. in water can be very challenging due to their low numbers and the complexity of the water matrix. This review describes the biology of Cryptosporidium spp. and current methods used in their detection with a focus on C. parvum and C. hominis. Among the methods discussed and compared are microscopy, immunology-based methods using monoclonal antibodies, molecular methods including PCR (polymerase chain reaction)-based assays, and emerging aptamer-based methods. These methods have different capabilities and limitations, but one common challenge is the need for better sensitivity and specificity, particularly in the presence of contaminants. The application of DNA aptamers in the detection of Cryptosporidium spp. oocysts shows promise in overcoming these challenges, and there will likely be significant developments in aptamer-based sensors in the near future.

Kinetic modeling of the synergistic thermal and spectral actions on the inactivation of Cryptosporidium parvum in water by sunlight

Water contamination with the enteroprotozoan parasite Cryptosporidium is a current challenge worldwide. Solar water disinfection (SODIS) has been proved as a potential alternative for its inactivation, especially at household level in low-income environments. This work presents the first comprehensive kinetic model for the inactivation of Cryptosporidium parvum oocysts by sunlight that, based on the mechanism of the process, is able to describe not only the individual thermal and spectral actions but also their synergy. Model predictions are capable of estimating the required solar exposure to achieve the desired level of disinfection under variable solar spectral irradiance and environmental temperature conditions for different locations worldwide. The thermal contribution can be successfully described by a modified Arrhenius equation while photoinactivation is based on a series-event mechanistic model. The wavelength-dependent spectral effect is modeled by means of the estimation of the C. parvum extinction coefficients and the determination of the quantum yield of the inactivation process. Model predictions show a 3.7% error with respect to experimental results carried out under a wide range of temperature (30 to 45 °C) and UV irradiance (0 to 50 W·m^-2). Furthermore, the model was validated in three scenarios in which the spectral distribution radiation was modified using different plastic materials common in SODIS devices, ensuring accurate forecasting of inactivation rates for real conditions.

High-Yield Purification of Giardia intestinalis Cysts from Fecal Samples

Giardia is an enteric protozoan parasite that causes gastroenteritis in all classes of vertebrates. It is ranked among the leading causes of death in children under 5 years of age. Giardiasis affects approximately 280 million people worldwide annually, a situation exacerbated by the low availability of effective treatments and the lack of a vaccine. In addition, the parasite is difficult to manipulate in in vitro environments, which hampers the development of effective disease management strategies. This article highlights the development of a method for the purification of viable Giardia cysts from fecal samples, verified by a trypan blue dye exclusion test. This protocol produces a 10-fold increase in yield over current methods. By combining sucrose flotation with gated filtration, the protocol significantly reduces the amount of debris in the purified cysts suspension. Cyst viability is verified by a trypan blue dye exclusion test. The ability to purify large quantities of Giardia from fecal samples could advance the development of effective treatments to target this worldwide prevalent parasite. © 2020 Wiley Periodicals LLC. Basic Protocol: Purification of Giardia cysts from fecal samples Support Protocol: Cyst viability test.

Intestinal Schistosomiasis and Giardiasis Co-Infection in Sub-Saharan Africa: Can a One Health Approach Improve Control of Each Waterborne Parasite Simultaneously?

Both intestinal schistosomiasis and giardiasis are co-endemic throughout many areas of sub-Saharan Africa, significantly impacting the health of millions of children in endemic areas. While giardiasis is not considered a neglected tropical disease (NTD), intestinal schistosomiasis is formally grouped under the NTD umbrella and receives significant advocacy and financial support for large-scale control. Although there are differences in the epidemiology between these two diseases, there are also key similarities that might be exploited within potential integrated control strategies permitting tandem interventions. In this review, we highlight these similarities and discuss opportunities for integrated control of giardiasis in low and middle-income countries where intestinal schistosomiasis is co-endemic. By applying new, advanced methods of disease surveillance, and by improving the provision of water, sanitation and hygiene (WASH) initiatives, (co)infection with intestinal schistosomiasis and/or giardiasis could not only be more effectively controlled but also better understood. In this light, we appraise the suitability of a One Health approach targeting both intestinal schistosomiasis and giardiasis, for if adopted more broadly, transmission of both diseases could be reduced to gain improvements in health and wellbeing.

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.

Cryptosporidium spp. in groundwater supplies intended for human consumption - A descriptive review of global prevalence, risk factors and knowledge gaps

Cryptosporidiosis is one of the leading causes of diarrhoeal illness and mortality induced by protozoan pathogens worldwide. As a largely waterborne disease, emphasis has been given to the study of Cryptosporidium spp. in surface waters, readily susceptible to pathogenic contamination. Conversely, the status of Cryptosporidium in potable groundwater sources, generally regarded as a pristine and "safe" drinking-water supply owing to (sub)-soil protection, remains largely unknown. As such, this investigation presents the first literature review aimed to ascertain the global prevalence of Cryptosporidium in groundwater supply sources intended for human consumption. Thirty-seven peer-reviewed studies were identified and included in the review. Groundwater sample and supply detection rates (estimated 10-20%) indicate Cryptosporidium is frequently present in domestic groundwater sources, representing a latent health concern for groundwater consumers. Specifically, sample (10.4%) and source (19.1%) detection rates deriving from comprehensive "temporal" investigations are put forward as representative of a contamination 'baseline' for Cryptosporidium in 'domestic' groundwater supplies. Proposed 'baseline' prevalence figures are largely applicable in preventive risk-based catchment and groundwater quality management including the formulation of Quantitative Microbial Risk Assessment (QMRA). Notwithstanding, a large geographical disparity in available investigations and lack of standardized reporting restrict the transferability of research findings. Overall, the mechanisms responsible for Cryptosporidium transport and ingress into groundwater supplies remain ambiguous, representing a critical knowledge gap, and denoting a distinctive lack of integration between groundwater and public-health sub-disciplines among investigations. Key recommendations and guidelines are provided for prospective studies directed at more integrative and multi-disciplinary research.

Diarrhoea associated with gastrointestinal parasites in grazing sheep

Diarrhoea is a common, widespread and frustrating reality for sheep enterprises in most sheep producing regions globally and of particular concern in Australia as the major risk factor for breech flystrike. Parasitic disease has long been recognised as an important factor in diarrhoea in sheep, particularly the gastrointestinal nematodes (Trichostrongylus and Teladorsagia species). This review focuses on the role of parasitic infections in causing diarrhoea in sheep, with emphasis on the epidemiology of diarrhoea outbreaks related to worms and opportunities to manage the risk of diarrhoea outbreaks in sheep related to parasitic infections. Parasitic nematodes damage the gastrointestinal tract via a complex relationship between direct impacts from worms, such as physical changes to the gut mucosa, and indirect effects largely associated with the host response. Diarrhoea associated with large worm burdens is most efficiently managed through integrated parasite management programs. Despite some limitations, measuring faecal worm egg counts remains a mainstay for assessing the contribution of worms to outbreaks of diarrhoea in sheep. Larval hypersensitivity scouring is emerging as a significant cause of worm-related diarrhoea in sheep without large adult worm burdens in some geographic locations. The syndrome describes a heightened inflammatory response to the ingestion of trichostrongylid infective larvae seen in the gut of sheep with diarrhoea, and is most effectively addressed through selecting sheep for low breech soiling ('dag scores'), as worm resistant sheep may show an increased propensity for diarrhoea, even with low rates of larval challenge. Importantly, dag should be considered as a separate trait to WEC in breeding indexes. Outbreaks of diarrhoea in young sheep are often multifactorial, and co-infections with nematodes and other infectious agents associated with diarrhoea are common. This presents challenges for the field investigation of diarrhoea in grazing sheep.

Waterborne protozoan pathogens in environmental aquatic biofilms: Implications for water quality assessment strategies

Biofilms containing pathogenic organisms from the water supply are a potential source of protozoan parasite outbreaks and a significant public health concern. The aim of the present study was to demonstrate the simultaneous and multi-spatial occurrence of waterborne protozoan pathogens (WBPP) in substrate-associated biofilms (SAB) and compare it to surface water (SW) and sediments with bottom water (BW) counterparts using manual filtration and elution from low-volume samples. For scenario purposes, simulated environmental biofilm contamination was created from in-situ grown one-month-old SAB (OM-SAB) that were spiked with Cryptosporidium parvum oocysts. Samples were collected from the largest freshwater reservoirs in Luzon, Philippines and a University Lake in Thailand. A total of 69 samples (23 SAB, 23 SW, and 23 BW) were evaluated using traditional staining techniques for Cryptosporidium, and Immunofluorescence staining for the simultaneous detection of Cryptosporidium and Giardia. WBPP were found in 43% SAB, 39% SW, and 39% BW of the samples tested in the present study with SAB results reflecting SW and BW results. Further highlights were demonstrated in the potential of using low-volume samples for the detection of parasites in source water. Scanning electron microscopy of OM-SAB samples revealed a naturally-associated testate amoeba shell, while Cryptosporidium oocysts spiked samples provided a visual profile of what can be expected from naturally contaminated biofilms. This study provides the first evidence for the simultaneous and multi-spatial occurrence of waterborne protozoan pathogens in low-volume aquatic matrices and further warrants SAB testing along with SW and BW matrices for improved water quality assessment strategies (iWQAS).

Update on the major imported protozoan infections in travelers and migrants

Globalization has contributed to the emergence of specific parasitic diseases in novel geographical areas, and in these regions, these infections in travelers and immigrants may cause a considerable burden of disease. Timely diagnosis and treatment of protozoan infections to decrease mortality and prevent associated complications are essential. In this respect, the increased availability of specific DNA-detection procedures has improved the diagnosis of many imported parasitic infections. Travelers and immigrants with associated comorbidities or immunosuppression may pose a special challenge regarding management. An updated review of the main protozoan infections in mobile populations (malaria, Chagas disease, leishmaniasis, enteric protozoan infections) is provided, focusing on the changing epidemiology of these diseases, recent developments in diagnosis and management and the possibility of local transmission of imported infections.

Clinical Management of Infectious Diarrhea

BACKGROUND

Infectious diarrhea is the most common cause of diarrhea worldwide and is responsible for more deaths than other gastrointestinal tract diseases such as gastrointestinal cancers, peptic ulcer disease or inflammatory bowel disease. Diarrheal disease still represents the 8th leading cause of death worldwide, with more than 1,6 million attributed fatalities in 2016 alone. The majority of cases can be divided into three principal clinical presentations: acute watery diarrhea lasting 5-10 days and normally self-limiting, bloody diarrhea (dysentery), and persistent diarrhea with or without intestinal malabsorption.

METHODS

We performed an electronic search on PUBMED of the scientific literature concerning infectious diarrhea and its clinical management.

AIM

In this review article, we analyze the most important causes of infectious diarrhea and their constellation of signs and symptoms, providing an update on the diagnostic tools available in today's practice and on the different treatment options.

CONCLUSION

Even though the majority of intestinal infections are self-limiting in immunocompetent individuals, specific diagnosis and identification of the causative agent remain crucial from public health and epidemiological perspectives. Specific diagnostic investigation can be reserved for patients with severe dehydration, more severe illness, persistent fever, bloody stools, immunosuppression, and for cases of suspected nosocomial infection or outbreak and it includes complete blood count, creatinine and electrolytes evaluation, determination of leukocytes and lactoferrin presence in the stools, stool culture, together with C. difficile testing, PCR, ova and parasites' search, endoscopy and abdominal imaging. Since acute diarrhea is most often self-limited and caused by viruses, routine antibiotic use is not recommended for most adults with mild, watery diarrhea. However, when used appropriately, antibiotics are effective against shigellosis, campylobacteriosis, C. difficile colitis, traveler's diarrhea, and protozoal infections. Furthermore, antibiotics use should be considered in patients who are older than 65 years, immunocompromised, severely ill, or septic.

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

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

Occurrence and molecular characterization of Giardia duodenalis in child population from Colombia

Giardia duodenalis is one of the most prevalent human intestinal parasite, with children living in developing countries being particularly at risk of infection. The occurrence and molecular diversity of G. duodenalis was investigated in stools specimens from 307 individuals aged one to nineteen years in Colombia. Samples were collected in three educational establishments (n: 163) and two hospital laboratories (n: 144) from urban and rural areas. Feces were concentrated using a biphasic sedimentation method and wet mounts of the sediment were examined by light microscopy. G. duodenalis assemblages and sub-assemblages were determined on positive samples by PCR of the triose phosphate isomerase (tpi), β-giardin (bg) and small-subunit (ssu) rRNA genes. G. duodenalis infection was detected by microscopy in 23 individuals (7.5%). The protozoan was more prevalent among specimens collected in educational establishments (11.6%) than in those obtained from hospital laboratories (2.8%). Infection was most common in individuals from urban areas and children aged 1-5 years. No significant association between diarrhea and infection could be demonstrated. Twenty Giardia-positive samples were successfully allocated to assemblage B (n: 11), sub-assemblage AII (n: 7), and assemblage A (n: 2). Results indicate the potential for transmission of G. duodenalis infection in children attending educational establishments and individuals from urban areas, where transmission seems to be primarily anthroponotic.

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.

Detection of Giardia spp. with formalin/ether concentration in Brassica oleracea (cabbage) and Lactuca sativa (lettuce)

Methods to detect protozoa are needed for food safety monitoring. We evaluated protocols to recover Giardia spp. cysts in Brassica oleracea (cabbage) and Lactuca sativa (lettuce) and then detection was performed by concentrating with formalin/ether solutions and microscopy or immunofluorescence or DNA amplification via PCR. To evaluate this methodology, G. duodenalis cysts were inoculated in triplicate (10 cysts) in 35-g samples of lettuce and cabbage. The method obtaining the highest percentage of recovery in cabbage was sulfamic acid solution plus stirring with stomacher (47.7% ± 7.5). For lettuce, the best method was glycine solution plus stirring with stomacher (46.6% ± 5.3). Inter-observer agreement was of 0.99. Giardia was detected by amplifying specific sequences for the DNA coding SSU rRNA. In 27 lettuce samples and 27 cabbage samples, obtained from supermarkets and street vendors, two lettuce samples (7.4%) and one cabbage sample (3.7%) were positive for Giardia via PCR assay and were sequenced, determining that they were two of assemblage B and one of lettuce to assemblage E. This method is proposed to detect Giardia in vegetables by PCR detection, enabling public health authorities to identify genotypes circulating in food, which will help to establish measures that reduce outbreaks of parasitic diseases associated with contaminated food.

Molecular epidemiology of Giardia and Cryptosporidium infections - What's new?

New information generated since 2016 from the application of molecular tools to infections with Giardia and Cryptosporidium is critically summarised. In the context of molecular epidemiology, nomenclature, taxonomy, in vitro culture, detection, zoonoses, population genetics and pathogenicity, are covered. Whole genome sequencing has had the greatest impact in the last three years. Future advances will provide a much better understanding of the zoonotic potential of both parasites, their diversity and how this is linked to pathogenesis in different hosts.