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

The global prevalence of Giardia infection in horses: A systematic review and meta-analysis

Giardia duodenalis as a common zoonotic parasite is a public health problem infecting humans and a wide range of animals, including horses. This systematic review and meta-analysis was conducted to estimate the global pooled prevalence of Giardia infection in horses. Literature searches were conducted using databases including Scopus, ScienceDirect, PubMed, Web of Science and ProQuest to December 2023. A random-effect model was performed to calculate the pooled prevalence and corresponding 95% confidence interval (CI) according to the degree of heterogeneity in the included studies. Of 2661 articles, approximately 27 articles were eligible for inclusion in the meta-analysis. The pooled prevalence of giardiasis in horses using the random effect method was 8.93% (95% CI = 5.98% to 12.42%). There were significant differences between the giardiasis prevalence in different continent, countries and ages of horses. The highest and lowest prevalence of giardiasis was found in Europe (12.24%) and Africa (0 %), respectively. The prevalence of Giardia was significantly higher in horses <3 years of ages. Based on the diagnostic method, the highest and lowest incidence of horse Giardia infection was detected by immunological assays (9.24%) and molecular methods (7.87%), respectively. The result of our study showed that assemblage B is the most common genotype in horses followed by assemblage A and E. Due to the widespread use of horses on farms or for recreational riding, data on the source of infection, prevalence, transmission mechanisms, and genotype are crucial for the establishment of control and prevention strategies.

First Report on Genotyping of Giardia duodenalis in Farmed Rabbits in Algeria

Relatively, the epidemiology of giardiasis in rabbits has been poorly documented worldwide. In Algeria, few molecular studies reporting G. duodenalis genotyping/subtyping have been conducted only in livestock and in humans. The present study aims to perform genotyping and subtyping of G. duodenalis in farmed rabbits using multilocus sequence typing (MLST) analysis. Forty-four faecal samples were collected from 23 rabbit farms in Boumerdes and Tizi Ouzou provinces, located in central Algeria. Firstly, the detection of Giardia cysts in the faeces of rabbits was performed using the ELISA method (RIDASCREEN® Giardia test). Subsequently, positive ELISA samples were subjected to PCR amplification and sequencing of three genetic loci, including the triose phosphate isomerase (tpi), beta-giardin (bg), and glutamate dehydrogenase (gdh) genes. ELISA test detected 13 (29.5%) positive samples among 44 screened samples. Of which, molecular analysis showed the presence of nine positive samples at least by one gene. Eight positive samples were determined as G. duodenalis assemblage B based on phylogenetic analyses of sequences from the three loci. One sample was clustered with assemblage E reference sequences for the gdh gene, while tpi and bg results showed assemblage B. The present study reports valuable data on the epidemiology of giardiasis in rabbits in Algeria, particularly the occurrence of zoonotic G. duodenalis assemblage B.

Global prevalence of Giardia infection in nonhuman mammalian hosts: A systematic review and meta-analysis of five million animals

BACKGROUND

Members of the Giardia genus are zoonotic protozoan parasites that cause giardiasis, a diarrheal disease of public and veterinary health concern, in a wide range of mammal hosts, including humans.

METHODOLOGY

We conducted a systematic review and meta-analysis to provide evidence-based data on the worldwide prevalence of Giardia infection in nonhuman mammals that can be used as scientific foundation for further studies. We searched public databases using specific keywords to identify relevant publications from 1980 to 2023. We computed the pooled prevalence estimates utilizing a random-effects meta-analysis model. Animals were stratified according to their taxonomic hierarchy, as well as ecological and biological factors. We investigated the influence of predetermined variables on prevalence estimates and heterogeneity through subgroup and meta-regression analyses. We conducted phylogenetic analysis to examine the evolutionary relationships among different assemblages of G. duodenalis.

PRINCIPAL FINDINGS

The study included 861 studies (1,632 datasets) involving 4,917,663 animals from 327 species, 203 genera, 67 families, and 14 orders from 89 countries. The global pooled prevalence of Giardia infection in nonhuman mammals was estimated at 13.6% (95% CI: 13.4-13.8), with the highest rates observed in Rodentia (28.0%) and Artiodactyla (17.0%). Herbivorous (17.0%), semiaquatic (29.0%), and wild (19.0%) animals showed higher prevalence rates. A decreasing prevalence trend was observed over time (β = -0.1036477, 95% CI -0.1557359 to -0.0515595, p < 0.000). Among 16,479 G. duodenalis isolates, 15,999 mono-infections belonging to eight (A-H) assemblages were identified. Assemblage E was the predominant genotype (53.7%), followed by assemblages A (18.1%), B (14.1%), D (6.4%), C (5.6%), F (1.4%), G (0.6%), and H (0.1%). The highest G. duodenalis genetic diversity was found in cattle (n = 7,651, where six assemblages including A (13.6%), B (3.1%), C (0.2%), D (0.1%), E (81.7%), and mixed infections (1.2%) were identified.

CONCLUSIONS/SIGNIFICANCE

Domestic mammals are significant contributors to the environmental contamination with Giardia cysts, emphasizing the importance of implementing good management practices and appropriate control measures. The widespread presence of Giardia in wildlife suggests that free-living animals can potentially act as sources of the infection to livestock and even humans through overlapping of sylvatic and domestic transmission cycles of the parasite.

Systematic Review of Microorganism Removal Performance by Physiochemical Water Treatment Technologies

Access to safe drinking water is crucial for public health necessitating the use of effective water treatment processes. We conducted a systematic literature review on microorganism removal by physical treatment processes used in drinking water treatment systems with the aim of providing current summary data to update the World Health Organization's Guidelines for Drinking Water Quality (GDWQ) and to reflect on the data available for comparison of treatment technologies. We reviewed peer-reviewed articles reporting original data that were published between 1997 and March 2022 on the following physical treatment technologies: roughing filters, storage reservoirs, bank filtration, conventional and high-rate clarification, dissolved air flotation, lime softening, granular media filtration, slow sand filtration, precoat filtration, membrane filtration, granular activated carbon, ceramic membrane filtration, and soil aquifer treatment. The literature search was conducted in several databases including Web of Science and PubMed. Data from 165 articles were included in the analysis and used to calculate Log Reduction Values (LRVs) for each technology by microbial contaminant type (bacteria, virus, or protozoa). The quantity and quality of data ranged widely for each technology. We found granular media, membranes (microfiltration (MF), ultrafiltration (UF), and reverse osmosis (RO)), and precoat filtration to remove the most protozoa with average LRVs of 3.0 (95% CI 2.8-3.3), 5.7 (95% CI 5.4-6.0), and 4.4 (95% CI 4.1-4.7), respectively. Bacteria was removed most effectively by membrane filtration (MF, UF, RO) with average LRVs of 4.5 (95% CI 3.9-5.1) and moderately by dissolved air flotation, lime softening, and soil aquifer treatment with average LRVs of 2.7, 2.6, and 2.4 respectively. Viruses were removed most effectively by reverse osmosis membrane filtration with an average LRV of 4.9 (95% CI 4.0-5.7). This data provides valuable information on pathogen reduction and areas of needed research. The variation in results underscores the importance of further consideration when selecting technologies to use and the need for standardized reporting in both lab and field studies. It is important to consider variables in water quality and technology operation that may impact treatment effectiveness when selecting treatment options for use. The findings contribute to ongoing efforts to revise the WHO's GDWQ, offering updated insights into LRVs for different water treatment technologies.

A Global Systematic Review and Meta-Analysis of Giardia duodenalis in Rabbits: Epidemiology, Genetic Diversity and Possible Zoonotic Concerns

BACKGROUND

Giardia duodenalis is a pathogenic protozoan responsible for gastrointestinal infections in various hosts, including rabbits. Understanding its epidemiology, genetic diversity and zoonotic implications is vital for public health and veterinary medicine. This systematic review and meta-analysis aimed to synthesize global data on the prevalence of G. duodenalis in rabbit populations, assess the genetic diversity of the isolates and evaluate the associated zoonotic potential.

METHODS

We conducted a thorough literature search across multiple databases (PubMed, Scopus, Web of Science and Google Scholar) for studies published until 18 October 2024. Only peer-reviewed articles reporting original research on G. duodenalis in rabbits were included. We extracted data on prevalence rates, testing times, publication years, countries, continents, WHO regions, diagnostic methods, genes used, assemblages and sub-assemblages. A meta-analysis using random-effects models was performed to calculate pooled prevalence rates, with the I2 index used to assess heterogeneity.

RESULTS

A total of 26 studies/datasets were analysed, covering data from 5543 rabbits across 15 countries. The estimated pooled prevalence of G. duodenalis in rabbits was 12.1% (95% CI: 7%-20%), with substantial heterogeneity (I2 = 96.5%). Geographic analysis showed higher prevalence rates in Africa and the AFR WHO region (72.3%, 95% CI: 61.7%-80.8%). Genetic analysis revealed three zoonotic assemblages (A, B and E) and two zoonotic sub-assemblages (AI and BIV) of G. duodenalis in rabbits, highlighting concerns over zoonotic transmission.

CONCLUSIONS

The findings highlight the global presence and genetic diversity of G. duodenalis in rabbits, indicating potential zoonotic risks. Ongoing monitoring and research are essential to clarify the transmission dynamics and public health implications of G. duodenalis in these animals. Raising awareness among pet owners, veterinarians and public health officials is vital to mitigate potential zoonosis.

Rabbits as reservoirs: An updated perspective of the zoonotic risk from Cryptosporidium and Giardia

Rabbits are highly abundant in many countries and can serve as reservoirs of diseases for a diversity of pathogens including the enteric protozoan parasites, Cryptosporidium and Giardia. Both parasites shed environmentally robust environmental stages (oo/cysts) and have been responsible for numerous waterborne outbreaks of diseases. Cryptosporidium hominis and C. parvum are responsible for most infections in humans, while Giardia duodenalis assemblages A and B, cause most human cases of giardiasis. Cryptosporidium cuniculus, the dominant species infecting rabbits, is the only spceies other than C. hominis and C. parvum to have caused a waterborne outbreak of gastritis, which occurred in the United Kingdom in 2008. This review examines the prevalence of Cryptosporidium and Giardia species in rabbits to better understand the public health risks of contamination of water sources with Cryptosporidium and Giardia oo/cysts from rabbits. Despite the abundance of C. cuniculus in rabbits, reports in humans are relatively rare, with the exception of the United Kingdom and New Zealand, and reports of C. cuniculus in humans from the United Kingdom have declined substantially since the 2008 outbreak. Subtyping of C. cuniculus has supported the potential for zoonotic transmission. Relatively few studies have been conducted on Giardia, but assemblage B dominates. However, improved typing methods are required to better understand the transmission dynamics of Giardia assemblages in rabbits. Similarly, it is not well understood if pet rabbits or contaminated water are the main source of C. cuniculus infections in humans. Well-planned studies using high-resolution typing tools are required to understand the transmission dynamics better and quantify the public health risk of Cryptosporidium and Giardia from rabbits.

Zoonotic Cryptosporidium and Giardia in marsupials-an update

Marsupials, inhabiting diverse ecosystems, including urban and peri-urban regions in Australasia and the Americas, intersect with human activities, leading to zoonotic spill-over and anthroponotic spill-back of pathogens, including Cryptosporidium and Giardia. This review assesses the current knowledge on the diversity of Cryptosporidium and Giardia species in marsupials, focusing on the potential zoonotic risks. Cryptosporidium fayeri and C. macropodum are the dominant species in marsupials, while in possums, the host-specific possum genotype dominates. Of these three species/genotypes, only C. fayeri has been identified in two humans and the zoonotic risk is considered low. Generally, oocyst shedding in marsupials is low, further supporting a low transmission risk. However, there is some evidence of spill-back of C. hominis into kangaroo populations, which requires continued monitoring. Although C. hominis does not appear to be established in small marsupials like possums, comprehensive screening and analysis are essential for a better understanding of the prevalence and potential establishment of zoonotic Cryptosporidium species in small marsupials. Both host-specific and zoonotic Giardia species have been identified in marsupials. The dominance of zoonotic G. duodenalis assemblages A and B in marsupials may result from spill-back from livestock and humans and it is not yet understood if these are transient or established infections. Future studies using multilocus typing tools and whole-genome sequencing are required for a better understanding of the zoonotic risk from Giardia infections in marsupials. Moreover, much more extensive screening of a wider range of marsupial species, particularly in peri-urban areas, is required to provide a clearer understanding of the zoonotic risk of Cryptosporidium and Giardia in marsupials.

Variation in the Structure and Composition of Bacterial Communities within Drinking Water Fountains in Melbourne, Australia

Modern drinking water distributions systems (DWDSs) have been designed to transport treated or untreated water safely to the consumer. DWDSs are complex environments where microorganisms are able to create their own niches within water, biofilm or sediment. This study was conducted on twelve drinking fountains (of three different types, namely types A, B and C) within the Melbourne (Australia) city area with the aim to (i) characterize the water quality and viable and total counts at each fountain, (ii) compare the differences in the structure and diversity of the bacterial community between bulk water and biofilm and (iii) determine differences between the bacterial communities based on fountain type. Samples of water and biofilm were assessed using both culture-dependent and culture-independent techniques. Heterotrophic plate counts of water samples ranged from 0.5 to 107.5 CFU mL−1, and as expected, total cell counts (cells mL−1) were, on average, 2.9 orders of magnitude higher. Based on the mean relative abundance of operational taxonomic units (OTUs), ANOSIM showed that the structure of the bacterial communities in drinking water and biofilm varied significantly (R = 0.58, p = 0.001). Additionally, ANOSIM showed that across fountain types (in water), the bacterial community was more diverse in fountain type C compared to type A (p < 0.001) and type B (p < 0.001). 16S rRNA next-generation sequencing revealed that the bacterial communities in both water and biofilm were dominated by only seven phyla, with Proteobacteria accounting for 71.3% of reads in water and 68.9% in biofilm. The next most abundant phylum was Actinobacteria (10.4% water; 11.7% biofilm). In water, the genus with the highest overall mean relative abundance was Sphingomonas (24.2%), while Methylobacterium had the highest mean relative abundance in biofilm samples (54.7%). At the level of genus and higher, significant differences in dominance were found across fountain types. In water, Solirubrobacterales (order) were present in type C fountains at a relative abundance of 17%, while the mean relative abundance of Sphingomonas sp. in type C fountains was less than half that in types A (25%) and B (43%). In biofilm, the relative abundance of Sphingomonas sp. was more than double in type A (10%) fountains compared to types B (4%) and C (5%), and Sandarakinorhabdus sp. were high in type A fountains (6%) and low in types B and C (1%). Overall this research showed that there were significant differences in the composition of bacterial communities in water and biofilm from the same site. Furthermore, significant variation exists between microbial communities present in the fountain types, which may be related to age. Long-established environments may lead to a greater chance of certain bacteria gaining abilities such as increased disinfection resistance. Variations between the structure of the bacterial community residing in water and biofilm and differences between fountain types show that it is essential to regularly test samples from individual locations to determine microbial quality.

Prevalence and molecular characterization of novel species of the Diplomonad genus Octomitus (Diplomonadida: Giardiinae) from wildlife in a New York watershed

Octomitus is a diplomonad genus known to inhabit the intestinal tracts of rodents. Ultrastructural morphology and 18S rDNA gene sequence analysis support the placement of Octomitus as the closest sister lineage to Giardia, a parasite which causes diarrheal disease in humans and animals worldwide. However, further information on the ecology and diversity of Octomitus is currently scarce. Expanding the available database of characterized sequences for this organism would therefore be helpful to studies of Diplomonad ecology, evolution, and epidemiology, particularly related to the evolution of parasitism in Giardia and Spironucleus, another related Diplomonad common in commercial fish farming. In order to study the prevalence and genotypic diversity of Octomitus, we developed a nested PCR assay specific to Octomitus and optimized to detect genotypes in fecal samples collected from wildlife in a New York watershed, and sequenced a portion of the small subunit ribosomal DNA (18S rDNA) gene to identify samples to species level. Molecular evidence suggested that Octomitus genotypes display similar prevalence to Cryptosporidium and microsporidian pathogens in wildlife as well as strong host preference for rodent and opossum hosts. Phylogenetic analysis showed strong support for 14 Octomitus genotypes, 13 of these novel, and patterns of host-parasite co-evolution.

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First molecular detection assay for novel Octomitus genotypes.

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13 new Octomitus genotypes are identified in diverse rodent hosts and a marsupial.

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Comparable prevalence of Octomitus in wildlife to Cryptosporidium and microsporidia (24.3%).

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Octomitus likely has little, if any, public health impact.

Cryptosporidium and Giardia in dam water on sheep farms - An important source of transmission?

Cryptosporidium and Giardia infections can negatively impact livestock health and reduce productivity, and some species and genotypes infecting livestock have zoonotic potential. Infection occurs via the faecal-oral route. Waterborne infections are a recognised source of infection for humans, but the role of livestock drinking water as a source of infection in livestock has not been described. This study aimed to determine whether contaminated drinking water supplies, such as farm dams, are a likely transmission source for Cryptosporidium and Giardia infections for extensively managed sheep. Dam water samples (n = 47) were collected during autumn, winter and spring from 12 farm dams located on six different farms in south west Western Australia, and faecal samples (n = 349) were collected from sheep with access to these dams. All samples were initially screened for Cryptosporidium spp. at the 18S locus and Giardia spp. at the gdh gene using qPCR, and oocyst numbers were determined directly from the qPCR data using DNA standards calibrated by droplet digital PCR. Cryptosporidium-positive sheep faecal samples were typed and subtyped by sequence analysis of 18S and gp60 loci, respectively. Giardia-specific PCR and Sanger sequencing targeting tpi and gdh loci were performed on Giardia- positive sheep faecal samples to characterise Giardia duodenalis assemblages. To identify Cryptosporidium and Giardia spp. in dam water samples, next-generation sequencing analysis of 18S and gdh amplicons were performed, respectively. Two species of Cryptosporidium (Cryptosporidium xiaoi and Cryptospordium ubiquitum (subtype family XIIa)) were detected in 38/345 sheep faecal samples, and in water from 9/12 farm dams during the study period, with C. xiaoi the species most frequently detected in both faeces and dam water overall. Giardia duodenalis assemblages AI, AII and E were detected in 36/348 faecal samples and water from 10/12 farm dams. For dam water samples where oo/cysts were detected by qPCR, Cryptosporidium oocyst concentration ranged from 518-2429 oocysts/L (n = 14), and Giardia cyst concentration ranged from 102 to 1077 cysts/L (n = 17). Cryptosporidium and Giardia with zoonotic potential were detected in farm dam water, including C. ubiquitum, C. hominis, C. parvum, C. cuniculus, C. xiaoi, and G. duodenalis assemblages A, B and E. The findings suggest that dam water can be contaminated with Cryptosporidium species and G. duodenalis assemblages that may infect sheep and with zoonotic potential, and farm dam water may represent one source of transmission for infections.

Multilocus genotyping of Giardia duodenalis in Bactrian camels (Camelus bactrianus) in China

The protozoan parasite Giardia duodenalis is known to infect humans and a wide range of animals globally. However, no studies on G. duodenalis infection in Bactrian camels have been reported. In the present study, in order to examine the prevalence and genetic diversity of G. duodenalis in Bactrian camels, 852 fecal samples were collected from 24 sampling sites in three geographical areas (Gansu province, Inner Mongolia, and Xinjiang Uygur autonomous regions) of northwestern China, and subjected to multilocus sequence typing (MLST) analysis targeting the 18S rRNA, β-giardin (bg), glutamate dehydrogenase (gdh), and triosephosphate isomerase (tpi) genes. About 84 fecal samples tested positive for Giardia infection, with an overall prevalence of 9.8%, including three samples from camel calves with diarrhea. Significant differences (χ² = 80.7, df = 2, P < 0.01) in the prevalence were found in Bactrian camels belonging to three geographical areas, with the highest (33.3%) in Gansu province and the lowest (4.2%) in Xinjiang Uygur autonomous region. Furthermore, significantly different prevalences (χ² = 34.2, df = 2, P < 0.01) were revealed among age groups, with the highest (35.7%) in camels aged 3 to 6 years old, and the lowest (7.5%) in camels aged > 6 years old. Sequence analysis identified two assemblages, including zoonotic assemblage A and ungulate-adapted assemblage E, with the latter as the dominant G. duodenalis assemblage in each age group and at all sampling sites having positive samples except Hotan. Genetic variations were detected among G. duodenalis isolates in these camels, and eight, three, and seven haplotypes were identified at loci bg, gdh, and tpi, respectively, forming two multilocus genotypes (MLGs) of zoonotic assemblage A and one MLG of assemblage E. To the best of our knowledge, this is the first report on G. duodenalis infection in Bactrian camels, and the data indicate that G. duodenalis have a broad host range.