Detection and genetic characterization of Giardia duodenalis in pigs from large-scale farms in Xinjiang, China

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 speeders of the infection to livestock and even humans through overlapping of sylvatic and domestic transmission cycles of the parasite.

Molecular prevalence of Giardia duodenalis in domestic pig (Sus domesticus) and captive wild boar (Sus scrofa) in China: A systematic review and meta-analysis

Giardia duodenalis is a typical enteric protozoan pathogen that causes diarrhea in humans and various animals, including domestic pigs (Sus domesticus) and wild boars (Sus scrofa). A healthy livestock would help maintain a hygienic environment, which is crucial for human health. This review has summarized the molecular prevalence of G. duodenalis among various types of pigs (domestic pigs and captive wild boars) in China on the basis of relevant data. A random-effects model of meta-analysis was used to estimate the overall and subgroup-based pooled prevalence of G. duodenalis, and the I2 index was used for the evaluation of the heterogeneity. Altogether, 23 datasets from 20 studies reporting G. duodenalis in 8282 pigs and captive wild boars across 12 regions in China revealed a 6.5 % (95 % CI, 6.0-7.0) pooled molecular prevalence of the parasite. Sensitivity analysis demonstrated that the data included in this study were stable. Meta-regression analysis showed that regions, type of pigs, age, and gender were not notably associated with the prevalence of G. duodenalis in the swine population in China. It was found that five G. duodenalis assemblages (A-E) are capable of infecting pigs in China, and assemblage E was found to be significantly dominant genotype (i.e., 73.2 % for the positive samples). G. duodenalis assemblages A and B were of major zoonotic concern with regard to humans; however, some reports have also documented assemblages C, D, and E from humans. Until now, information on the occurrence and distribution of G. duodenalis assemblages in Chinese pigs is limited, and therefore requires a rigorous and in-depth research.

First report of prevalence and assemblage analysis of Giardia duodenalis in pigs from Guangxi Zhuang Autonomous Region, southern China

Giardia duodenalis is a common intestinal protozoan that can cause diarrhea and intestinal disease in animals and in humans. However, the prevalence and assemblages of G. duodenalis in pigs from Guangxi Zhuang Autonomous Region have not been reported. In this study, a total of 724 fecal samples (201 from nursery pigs, 183 from piglets, 175 from breeding pigs, and 165 from fattening pigs) were obtained in four areas of the region (Nanning, Yulin, Hezhou, and Guigang). The gene of the small subunit ribosomal RNA (SSU rRNA) of G. duodenalis was amplified by nested PCR. The results show that the prevalence of G. duodenalis in pigs was 3.59% (26/724), of which 14 samples belonged to assemblage A (53.85%) and 12 samples belonged to assemblage E (46.15%). The infection rates of G. duodenalis in Hezhou, Yulin, Nanning, and Guigang were 0%, 0.7%, 10.8% and 1.1%, respectively (χ2 = 45.616, p < 0.01); whereas 5.1% of breeding pigs, 6.0% of piglets, 2.4% of fattening pigs, and 1.0% of nursery pigs were infected with G. duodenalis (χ2 = 8.874, p < 0.05). The SSU rRNA-positive samples were amplified by PCR based on the β-giardin (bg), glutamate dehydrogenase (gdh), and triphosphate isomerase (tpi) genes. Ten, eight and seven positive samples were detected, respectively. Based on phylogenetic analysis of the three genetic loci sequences, a multilocus genotyping A1 was found. The findings of this study provide basic data for the development of prevention and control of G. duodenalis infections in pigs and humans in the Guangxi Zhuang Autonomous Region.

First identification and coinfection detection of Enterocytozoon bieneusi, Encephalitozoon spp., Cryptosporidium spp. and Giardia duodenalis in diarrheic pigs in Southwest China

BACKGROUND

Enterocytozoon bieneusi, Encephalitozoon spp., Cryptosporidium spp., and Giardia duodenalis (G. intestinalis) are enteric pathogens that cause diarrhea in pigs. This study aimed to determine the prevalence of these enteric parasites and their coinfection with E. bieneusi in diarrheic pigs in Southwest China (Chongqing and Sichuan) using nested polymerase chain reaction (nPCR) based methods.

RESULTS

A total of 514 fecal samples were collected from diarrheic pigs from 14 pig farms in Chongqing (five farms) and Sichuan (nine farms) Provinces. The prevalence of Encephalitozoon spp., Cryptosporidium spp. and G. duodenalis was 16.14% (83/514), 0% (0/514), and 8.95% (46/514), respectively. Nested PCR revealed 305 mono-infections of E. bieneusi, six of E. cuniculi, two of E. hellem, and nine of G. duodenalis and 106 concurrent infections of E. bieneusi with the other enteric pathogens. No infections of E. intestinalis and Cryptosporidium species were detected. The highest coinfection was detected between E. bieneusi and E. cuniculi (10.5%, 54/514), followed by E. bieneusi and G. duodenalis (5.8%, 30/514) and E. bieneusi and E. hellem (2.9%, 15/514). E. bieneusi was the most frequently detected enteric pathogen, followed by E. cuniculi, G. duodenalis and E. hellem. There was a significant age-related difference in the prevalence of E. cuniculi in fattening pigs (χ2 = 15.266, df = 3, P = 0.002) and G. duodenalis in suckling pigs (χ2 = 11.92, df = 3, P = 0.008) compared with the other age groups. Sequence analysis of the ITS region of Encephalitozoon species showed two genotypes (II and III) for E. cuniculi and one (TURK1B) for E. hellem. Only G. duodenalis assemblage A was identified in all nested PCR-positive samples. E. bieneusi was found more often than other enteric pathogens.

CONCLUSIONS

This study showed that E. bieneusi, Encephalitozoon spp. [E. cuniculi and E. hellem] and G. duodenalis were common enteric parasites in diarrheic pigs in Chongqing and Sichuan Provinces. In case of both mono-infection and coinfection, E. bieneusi was the most common enteric pathogen in diarrheic pigs. Thus, it may be a significant cause of diarrhea in pigs. Precautions should be taken to prevent the spread of these enteric parasites.

Molecular detection and assemblage analysis of the intestinal protozoan Giardia duodenalis in wild boars in Korea

Giardia duodenalis (syn. G. intestinalis, G. lamblia) is the only Giardia species that infects humans and most other mammals. Wild boars are a reservoir of many viruses, bacteria, and parasites that can be transmitted to livestock and humans. This study examined the infection rate of G. duodenalis in wild boars and confirmed its specificity by comparing assemblages through PCR amplification of the 18S rRNA, gdh, and β-giardin genes. Fecal samples were collected from roadkilled or trapped wild boars from April 2016 to December 2021 in Korea. DNA was extracted directly from 612 wild boar fecal specimens using a commercial kit. PCR was performed targeting the 18S rRNA region, β-giardin, and glutamate dehydrogenase genes of G. duodenalis. Some PCR-positive samples were selected for sequencing analysis. The obtained sequences were subsequently used for phylogenetic tree construction. Of the 612 samples tested, 125 (20.4%) were positive for G. duodenalis. The highest infection rate was detected in the central region (12.0%) and in autumn (12.7%). Among the risk factors, the seasonal factor was statistically significant (p = 0.012). Phylogenetic analysis revealed three genetic assemblages: A, B, and E. Assemblages A and B exhibited 100% identity with Giardia sequences isolated from human and farmed pigs in Korea and Japan. This result cannot be ignored because it indicates the possibility of zoonotic transmission. Therefore, continuous management and monitoring of this pathogen are necessary to prevent transmission and protect animal and human health.

Molecular Detection and Multilocus Genotyping of Giardia duodenalis in Pigs in Fujian Province, Southeastern China

Giardia duodenalis, an intestinal parasite, is widely distributed in humans and various animals, such as pigs, cattle and cats. The clinical symptoms of giardiasis are characterized as including abdominal pain, acute or chronic diarrhea, and bloating and weight loss in humans and animals, leading to public and veterinary health problems worldwide. However, the prevalence and genotypes of G. duodenalis in pigs in Fujian Province, southeastern China, have not been reported. In the present study, 725 fecal samples were collected from six cities (Fuqing, Putian, Nanping, Longyan, Sanming, Zhangzhou) in Fujian Province and analyzed for G. duodenalis prevalence and genotypes using nested PCR targeting the beta-giardin (bg), glutamate dehydrogenase (gdh) and triosephosphate isomerase (tpi) genes. The results shown that total occurrence rate of G. duodenalis was 26.9% (195/725) in pigs, with significant differences in the prevalence among different regions (χ2 = 86.508, p < 0.05) and groups (χ2 = 12.748, p < 0.05). 195, 11 and 6 samples were detected at the bg, tpi and gdh loci, respectively. Each one belonged to a subtype of assemblage E and was analyzed using sequences obtained in this study. Based on phylogenetic analyses of sequences from the three genetic loci, only one MLG E1 was found. The results indicated that pigs may present a potential zoonotic risk of spreading G. duodenalis infection from animals to humans in this area. The findings of the present study also provide basic data for the prevention and control of G. duodenalis infection in pigs and humans in China.

First Characterization and Zoonotic Potential of Cryptosporidium spp. and Giardia duodenalis in Pigs in Hubei Province of China

The zoonotic protozoa parasites Cryptosporidium spp. and Giardia duodenalis infect a wide range of hosts, including humans. Pigs are reservoir hosts for Cryptosporidium spp. and G. duodenalis, which can transmit cryptosporidiosis and giardiasis to humans and other animals. The current study sought to investigate the infection rates and species/genotypes of Cryptosporidium spp. and G. duodenalis in pigs in Hubei of China. The nested PCR and sequence analyses of the small ribosomal subunit RNA (SSU rRNA) gene for Cryptosporidium spp. and the β-giardin (bg) gene for G. duodenalis was utilized to screen for the infection of those parasites in a total of 826 fresh fecal samples. Both Cryptosporidium spp. and G. duodenalis infection rates were 0.97% (8/826). Of the genotyped positive isolates, 6/8 (75%) were C. scrofarum and 2/8 (25%) were C. suis, while two zoonotic species G. duodenalis assemblage E and assemblage A were also detected in 7/8 (87.5%) isolates and 1/8 (12.5%) isolates, respectively. The findings suggest that both of those parasites in pig in intensive farms of Hubei province, China, pose a potential public health risk.

Molecular Detection and Characterization of Giardia duodenalis in Farmed Pigs in Three Provinces of Southern China

Giardia duodenalis is a flagellated zoonotic parasite that can infect various animals and humans, causing economic losses in husbandry and detriments to public health. Although it has been reported in pigs worldwide, there are few reports on the prevalence and assemblages of G. duodenalis infection in pigs in China. In this study, the 396 pig fecal samples were randomly collected from seven farms in Zhejiang, Guangdong and Yunnan provinces in southern China, and were examined by means of the nested PCR amplification of β-giardin (bg), glutamate dehydrogenase (gdh), and triose phosphate isomerase (tpi) for the detection of G. duodenalis. Overall, 21 fecal samples were positive for G. duodenalis, with a prevalence of 5.3%. Three risk factors are associated with G. duodenalis infection, namely, region, age and gender. Moreover, 13, six and two samples were successfully amplified at the bg, gdh and tpi gene loci, respectively. Three assemblages of G. duodenalis were identified, including assemblage E (n = 17), assemblage A (n = 3) and assemblage B (n = 1). Assemblage E was the dominating genotype and was distributed in three provinces. These assemblages of G. duodenalis have also been found in human beings, non-human primates, sheep, goats and cattle, which further reveals that farmed pigs pose a potential threat to public health.

Taxonomy and molecular epidemiology of Cryptosporidium and Giardia - a 50 year perspective (1971-2021)

The protozoan parasites Cryptosporidium and Giardia are significant causes of diarrhoea worldwide and are responsible for numerous waterborne and foodborne outbreaks of diseases. Over the last 50 years, the development of improved detection and typing tools has facilitated the expanding range of named species. Currently at least 44 Cryptosporidium spp. and >120 genotypes, and nine Giardia spp., are recognised. Many of these Cryptosporidium genotypes will likely be described as species in the future. The phylogenetic placement of Cryptosporidium at the genus level is still unclear and further research is required to better understand its evolutionary origins. Zoonotic transmission has long been known to play an important role in the epidemiology of cryptosporidiosis and giardiasis, and the development and application of next generation sequencing tools is providing evidence for this. Comparative whole genome sequencing is also providing key information on the genetic mechanisms for host specificity and human infectivity, and will enable One Health management of these zoonotic parasites in the future.

Zoonotic giardiasis: an update

Giardia duodenalis is a common intestinal parasite in various hosts, with the disease giardiasis being a zoonosis. The use of molecular typing tools has improved our understanding of the distribution and zoonotic potential of G. duodenalis genotypes in different animals. The present review summarizes recent data on the distribution of G. duodenalis genotypes in humans and animals in different areas. The dominance of G. duodenalis assemblages A and B in humans and common occurrence of host-adapted assemblages in most domesticated animals suggests that zoonotic giardiasis is probably less common than believed and could be attributed mainly to contact with or contamination from just a few species of animals such as nonhuman primates, equines, rabbits, guinea pigs, chinchillas, and beavers. Future studies should be directed to advanced genetic characterization of isolates from well-designed epidemiological investigations, especially comparative analyses of isolates from humans and animals living in the same household or community. This will likely lead to better understanding of zoonotic transmission of G. duodenalis in different environmental and socioeconomic settings.

Detection of Point Prevalence and Assemblages of Giardia spp. in Dairy Calves and Sika Deer, Northeast China

Giardia lamblia (syn Giardia duodenalis) is an important protozoan parasite that can cause enterocyte damage and loss of brush border of the epithelial cells in the intestine, resulting in shortening of microvilli and altered epithelial barrier function. Many animals have been detected as the hosts of the G. lamblia. However, the information on the epidemiology and molecular detection of G. lamblia in dairy calves and sika deer in northeastern China is limited. To investigate the prevalence and genotypes of dairy calves and sika deer in northeastern China, a total of 321 fecal samples from dairy calves in Heilongjiang Province and 818 fecal samples from sika deer in four provinces (Jilin Province, Heilongjiang Province, Liaoning Province, and Inner Mongolia Autonomous Region) in China were conducted by PCR methods, between September 2017 and April 2018. The overall prevalence of G. lamblia in dairy calves in Heilongjiang Province and sika deer in the four provinces was 4.98% (16/321) and 0.61% (5/818), respectively. In this study, the point prevalence of Giardia spp. in different factor groups was dissimilar. A total of 16 Giardia spp. positive samples in dairy calves were identified as assemblage E based on the triosephosphate isomerase (tpi), β-giardine (bg), and glutamate dehydrogenase (gdh) genes. Furthermore, two positive samples of assemblage A and three positive samples of assemblage E were identified with gdh and bg genes in the sika deer. Assemblage A was zoonotic genotype of G. lamblia, and assemblage E was identified as the predominant assemblage in dairy calves and sika deer. This study reported the prevalence and genotypes of G. lamblia in dairy calves in Heilongjiang Province and sika deer in four provinces in China. These results provided basic information to understand the epidemiology of G. lamblia in dairy calves and sika deer in China.