Multilocus genotyping of Giardia duodenalis in Malaysia

Giardia duodenalis is considered the most common intestinal parasite in humans worldwide. In Malaysia, many studies have been conducted on the epidemiology of giardiasis. However, there is a scarcity of information on the genetic diversity and the dynamics of transmission of G. duodenalis. The present study was conducted to identify G. duodenalis assemblages and sub-assemblages based on multilocus analysis of the glutamate dehydrogenase (gdh), beta-giardin (bg) and triose phosphate isomerase (tpi) genes. Faecal specimens were collected from 484 Orang Asli children with a mean age of 7 years and examined using light microscopy. Specimens positive for Giardia were subjected to PCR analysis of the three genes and subsequent sequencing in both directions. Sequences were edited and analysed by phylogenetic analysis. G. duodenalis was detected in 17% (84 of 484) of the examined specimens. Among them, 71 were successfully sequenced using at least one locus. Genotyping results showed that 30 (42%) of the isolates belonged to assemblage A, 32 (45%) belonged to assemblage B, while discordant genotype results were observed in 9 specimens. Mixed infections were detected in 43 specimens using a tpi-based assemblage specific protocol. At the sub-assemblages level, isolates belonged to assemblage A were AII. High nucleotide variation found in isolates of assemblage B made subtyping difficult to achieve. The finding of assemblage B and the anthroponotic genotype AII implicates human-to-human transmission as the most possible mode of transmission among Malaysian aborigines. The high polymorphism found in isolates of assemblage B warrants a more defining tool to discriminate assemblage B at the sub-assemblage level.     

Prevalence of Giardia duodenalis assemblages and sub-assemblages in symptomatic patients from Damascus city and its suburbs

Giardia duodenalis is one of the most important human enteric parasites worldwide and is endemic throughout the world with a vast range of mammalian hosts. However, there is limited information on the prevalent genetic variability of G. duodenalis in Syria. This study aimed to evaluate the predominance of G. duodenalis assemblages/sub-assemblages causing humans infection in the city of Damascus and its suburbs. 40 symptomatic giardiasis patients were recruited in this study. Fecal samples were genotyped using PCR/RFLP assay targeting the β-giardin and glutamate dehydrogenase (gdh) genes. HaeIII, BspL1 and RsaI restriction enzymes were used to differentiate between G. duodenalis assemblages/sub-assemblages. Our data showed that 65% of isolates were of assemblage A; 45% belonged to sub-assemblage AII and 20% to sub-assemblage AI. Assemblage B was detected in 27.5% of isolates; 12.5% fit in sub-assemblage BIV, 5% fit in sub-assemblage BIII and 10.5% fit in Discordant genotype BIII/BIV. Mixed genotypes (AII+BIII and AI+BIV) were identified in 3 isolates (7.5%). Significant correlation was found between Giardia AII sub-assemblage and weight loss symptom (P-value = 0.05) as well as between contact with domestic animals (cats, P-value = 0.027). Moreover, a significant correlation was found between sub-assemblage AI and livestock breeding (P-value = 0.000). In conclusion genotyping of human Giardia duodenalis isolates suggests anthroponotic transmission for the route of infection in Damascus and its suburbs. Further studies are needed to screen a wide geographic areas in Syria and to estimate the prevalence of G. duodenalis infection in our population.     

Giardiasis in NSW: Identification of Giardia duodenalis assemblages contributing to human and cattle cases,and an epidemiological assessment of sporadic human giardiasis

Two genetic assemblages (A and B) of the protozoan parasite species, Giardia duodenalis, infect humans, domestic animals and wildlife. In New South Wales, Australia, over 2000 sporadic human giardiasis cases are reported annually, but parasite sources and links between sporadic cases are unknown. This study describes G. duodenalis assemblages contributing to human and cattle cases in NSW, and examines demographic, spatial, and temporal distributions of NSW human infections and G. duodenalis assemblages. Genotyping by PCR-restriction fragment length polymorphism of the glutamate dehydrogenase (gdh) gene identified G. duodenalis assemblage B as the most common (86%) cause of infection among human cases (n = 165). Approximately 37% of cattle DNA samples were PCR positive (18S rRNA, gdh), and G. duodenalis assemblages E (69%) or B (31%) were identified from these samples. Human assemblage A was more common among older age groups, and seasonality in the geographic dispersal of human assemblage A was observed. The results of this study indicate G. duodenalis assemblage B is highly prevalent among humans in NSW, and the potential for cross-species transmission exists between humans and cattle in this region. Spatio-temporal and demographic distributions of human assemblage A and B are highlighted, and risk factors associated with these dispersal patterns warrants further research.     

Molecular diagnosis and genotype analysis of Giardia duodenalis in asymptomatic children from a rural area in central Colombia

Giardiasis is a parasitic infection that affects around 200 million people worldwide. This parasite presents a remarkable genetic variability observed in 8 genetic clusters named as ‘assemblages’ (A–H). These assemblages are host restricted and could be zoonotic where A and B infect humans and animals around the globe. The knowledge of the molecular epidemiology of human giardiasis in South-America is scarce and also the usefulness of PCR to detect this pathogen in fecal samples remains controversial. The aim of this study was to conduct a cross-sectional study to compare the molecular targets employed for the molecular diagnosis of Giardia DNA and to discriminate the parasite assemblages circulating in the studied population. We analyzed 181 fecal samples from Children at La Virgen, Cundinamarca, Colombia that were DNA-extracted and analyzed by SSU rDNA, tpi and gdh loci. We observed positivity by microscopy of 13% and by PCR around 76–80% depending on the molecular marker. Additionally, a lack of statistical concordance between microscopy and PCR was detected. Regarding the genetic assemblages, we detected assemblage A (3%), assemblage B (90%) and mixed infections assemblages A + B (7%). Hence, the sub-assemblages were typed as AI, AII, BIII and BIV across the population. This study represents a reliable attempt to understand the molecular epidemiology of giardiasis in Colombia and the use of PCR to detect cryptic infections. The epidemiological implications are herein discussed.     

Multilocus genotyping of Giardia duodenalis isolates from calves in Oromia Special Zone,Central Ethiopia

Giardia duodenalis is a widespread protozoan parasite that infects human and other mammals. Assessing the zoonotic transmission of the infection requires molecular characterization as there is considerable genetic variation within the species. This study was conducted to identify assemblages of Giardia duodenalis in dairy calves; and to assess the potential role of cattle isolates in zoonotic transmission in central Ethiopia. A total of 449 fecal samples were collected and screened using microscopy and PCR targeting the small-subunit (ssu) rRNA, triose phosphate isomerase (tpi), β-giardin (bg) and glutamate dehydrogenase (gdh) genes. The overall prevalence of Giardia duodenalis in dairy calves was found to be 9.6% (43/449). The prevalence of infection based on sex, age and breed difference was statistically not significant (p > 0.05). Genotyping results revealed the presence of assemblage E and assemblage A (AI). The genotypic frequency reported was 95.3% (41/43) for assemblage E and 4.7% (2/43) for assemblage A. There was one mixed infection with assemblages AI and E. Sequence analyses showed the existence of 10 genotypes within assemblage E. One genotype that showed novel nucleotide substitution was identified at the ssu rRNA locus. The other 9 genotypes, 3 at each locus, were identified at the tpi, the bg and the gdh loci with two of the gdh genotypes were novel. Findings of the current study indicate the occurrence of the livestock-specific assemblage E and the potentially zoonotic assemblage A, with the former being more prevalent. Although the zoonotic assemblage was less prevalent, there is a possibility of zoonotic human infection as AI is reported from both animals and humans.     

Strong genetic structure revealed by multilocus patterns of variation in Giardia duodenalis isolates of patients from Galicia (NW-Iberian Peninsula)

We report a survey of genetic variation at three coding loci in Giardia duodenalis of assemblages A and B obtained from stool samples of patients from Santiago de Compostela (Galicia, NW-Iberian Peninsula). The mean pooled synonymous diversity for assemblage A was nearly five times lower than for assemblage B (0.77% ± 0.30% and 4.14% ± 1.65%, respectively). Synonymous variation in both assemblages was in mutation-drift equilibrium and an excess of low-frequency nonsynonymous variants suggested the action of purifying selection at the three loci. Differences between isolates contributed to 40% and 60% of total genetic variance in assemblages A and B, respectively, which revealed a significant genetic structure. These results, together with the lack of evidence for recombination, support that (i) Giardia assemblages A and B are in demographic equilibrium and behave as two genetically isolated populations, (ii) infections are initiated by a reduced number of individuals, which may be genetically diverse and even belong to different assemblages, and (iii) parasites reproduce clonally within the host. However, the observation of invariant loci in some isolates means that mechanisms for the homogenization of the genetic content of the two diploid nuclei in each individual must exist.     

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.     

First molecular characterisation of Cryptosporidium and Giardia from Bubalus bubalis (water buffalo) in Victoria,Australia

We conducted a molecular epidemiological survey of Cryptosporidium and Giardia from Bubalus bubalis (water buffalo) on two extensive farms (450 km apart) in Victoria, Australia. Faecal samples (n = 476) were collected from different age groups of water buffalo at two time points (six months apart) and tested using a PCR-based mutation scanning-targeted sequencing-phylogenetic approach, employing markers within the small subunit of ribosomal RNA (designated pSSU) and triose phosphate isomerase (ptpi) genes. Based on pSSU data, Cryptosporidium parvum, Cryptosporidium bovis and Cryptosporidium genotypes 1, 2 (each 99% similar genetically to Cryptosporidium ryanae) and 3 (99% similar to Cryptosporidium suis) were detected in two (0.4%), one (0.2%), 38 (8.0%), 16 (3.4%) and one (0.2%) of the 476 samples tested, respectively. Using ptpi, Giardia duodenalis assemblages A and E were detected in totals of 56 (11.8%) and six (1.3%) of these samples, respectively. Cryptosporidium was detected on both farms, whereas Giardia was detected only on farm B, and both genera were detected in 1.5% of all samples tested. The study showed that water buffaloes on these farms excreted C. parvum and/or G. duodenalis assemblage A, which are consistent with those found in humans, inferring that these particular pathogens are of zoonotic significance. Future work should focus on investigating, in a temporal and spatial manner, the prevalence and intensity of such infections in water buffaloes in various geographical regions in Australia and in other countries.     

Giardia intestinalis in Thailand: Identification of Genotypes

This study was undertaken to determine the genetic diversities of Giardia intestinalis isolated in Thailand. G. intestinalis cysts were collected from stool samples of 61 subjects residing in Bangkok or in rural communities of Thailand with and without gastrointestinal symptoms. All the cyst samples gave positive tpi amplicons (100% sensitivity), either of the 148- or the 81-bp tpi segments. Cyst assemblage identification of the 148- and 81-bp tpi gene segments by polymerase chain reaction showed that 8% of the cysts were assemblage A, 41% assemblage A and B combined, and 51% assemblage B. The prevalence of assemblage A was significantly lower than that of assemblage B and the mixed types. Restriction fragment length polymorphism (RFLP) of the 384-bp β-giardin gene segment revealed that 12% and 88% of the assemblage A cysts were AI and AII respectively. RFLP, based on the 432-bp gdh gene segment, showed 45.5% of the assemblage B cysts to be BIII and 54.5% to be BIV. The AI sub-assemblage was less prevalent than the others. All subjects with AI and 50% of the subjects with BIII sub-assemblage cysts were symptomatic; 80% of symptomatic Bangkok residents were adults/elderly while 85% of the rural cases were children.Key words: β-giardin, Genotyping, Giardia duodenalis, Giardia intestinalis, Giardiasis, Glutamate dehydrogenase, Triose phosphate isomerase, Thailand     

Genetic analysis of Giardia and Cryptosporidium from people in Northern Australia using PCR-based tools

To date, there has been limited genetic study of the gastrointestinal pathogens Giardia and Cryptosporidium in northern parts of Australia. Here, PCR-based methods were used for the genetic characterization of Giardia and Cryptosporidium from 695 people with histories of gastrointestinal disorders from the tropical North of Australia. Genomic DNAs from fecal samples were subjected to PCR-based analyses of regions from the triose phosphate isomerase (tpi), small subunit (SSU) of the nuclear ribosomal RNA and/or the glycoprotein (gp60) genes. Giardia and Cryptosporidium were detected in 13 and four of the 695 samples, respectively. Giardia duodenalis assemblages A and B were found in 4 (31%) and 9 (69%) of the 13 samples in persons of < 9 years of age. Cryptosporidium hominis (subgenotype IdA18), Cryptosporidium mink genotype (subgenotype IIA16R1) and C. felis were also identified in single patients of 11–21 years of age. Future studies might focus on a comparative study of these and other protists in rural communities in Northern Australia.     

Genetic characterisation of Cryptosporidium and Giardia from dairy calves: Discovery of species/genotypes consistent with those found in humans

Cryptosporidium and Giardia are important genera of parasitic protists that can cause significant diarrhoeal diseases in humans and other animals. Depending on the species/genotype of parasite, human infection may be acquired via anthroponotic or zoonotic transmission routes. Here, we undertook a molecular epidemiological investigation of these two genera of parasites in pre- and post-weaned calves from eight locations in Canterbury, New Zealand, by PCR-coupled sequencing and phylogenetic analysis of sequence data for regions in the 60 kDa glycoprotein (pgp60) gene of Cryptosporidium and/or the triose-phosphate isomerase (ptpi) gene of Giardia. The pgp60 and ptpi regions were specifically amplified from 15 (8.3%) and 11 (6.1%) of the 180 individual faecal samples, respectively. The sequences derived from all of the amplicons were aligned with homologous reference sequences and subjected to phylogenetic analysis by Bayesian inference. For Cryptosporidium, three samples contained Cryptosporidium parvum genotype IIa, subgenotypes IIaA15G3R1, IIaA19G3R1 and IIaA23G4. Twelve samples contained Cryptosporidium hominis genotype Ib, subgenotype IbA10G2R2. While subgenotypes IIaA15G3R1 and IIaA23G4 are new records, IIaA19G3R1 and IbA10G2R2 are commonly found in humans in various countries. For Giardia, two samples contained Giardia duodenalis assemblage A, also common in humans. In contrast, nine samples contained G. duodenalis assemblage E, which is the first report of this assemblage in cattle in New Zealand. Therefore, the present results indicate that dairy calves on the South Island of New Zealand harbour ‘zoonotic’ genotypes of Cryptosporidium and Giardia, which is likely to have significant public health implications.     

Investigation into potential transmission sources of Giardia duodenalis in a threatened marsupial (Petrogale penicillata)

Assemblages of the protozoan parasite Giardia duodenalis common in humans and domestic species are increasingly identified in wildlife species, raising concern about the spill-over of pathogens from humans and domestic animals into wildlife. Here, the identity and prevalence of G. duodenalis in populations of a threatened marsupial, the brush-tailed rock-wallaby (Petrogale penicillata), was investigated. Identification of G. duodenalis isolates, across three loci (18S rRNA, β-giardin and gdh), from rock-wallaby fecal samples (n = 318) identified an overall detection rate of 6.3%. No significant difference in G. duodenalis detection was found among captive, wild and supplemented populations. Isolates were assigned to the zoonotic assemblages A and B at 18S rRNA, with sub-assemblages AI and BIV identified at the β-giardin and gdh loci, respectively. Assemblages AI and BIV have previously been identified in human clinical cases, but also in domestic animals and wildlife. The identification of these assemblages in brush-tailed rock-wallabies suggests there are transmission routes of G. duodenalis from humans or other animals to Australian wildlife, both in captivity and in the wild.     

Molecular typing of Giardia duodenalis in cattle,sheep and goats in an arid area of central Iran

Giardia duodenalis is one of the most common intestinal parasites in humans as well as livestock and wildlife. It is of both public and veterinary health importance in developing nations. A molecular survey of Giardia duodenalis assemblages in ruminants from Yazd Province, Iran was conducted on 484 animal faecal samples collected per rectum from slaughtered ruminants including 192 cattle, 192 sheep and 100 goats from June to November 2017. Species-specific and assemblage-specific PCRs for assemblages A, B and E at the triose phosphate isomerase (tpi) gene were performed, and samples positive for Giardia were confirmed by sequencing. In total, 25 (5.16%) of examined faecal samples including eight cattle (4.2%), twelve sheep (6.2%) and five goats (5%) were infected with G. duodenalis. Assemblage-specific PCR detected G. duodenalis assemblage E in seven faecal samples (six in sheep and one in a goat). Assemblages A and B were not detected. This study provides the first insight into Giardia infection in slaughtered livestock in Iran. Although the prevalence of infection with Giardia in this hot-arid area of Iran was low, educating people about direct contact with livestock such as farmers and abattoirs workers about this zoonotic infection is important.     

Prevalence and multilocus genotypes of Giardia duodenalis infecting pigs in Ogun state,Nigeria

Giardia duodenalis is an intestinal flagellated protozoan parasite that is infectious to humans and a wide range of animals worldwide. While varying prevalence rates have been reported in pigs worldwide, there are currently no published reports on the genotypes of Giardia infecting pigs in any African country. The present study is on the prevalence and genotypes of G. duodenalis in 209 pigs raised on four farms in Ogun State Nigeria. Using an enzyme-linked immunosorbent assay (ELISA) kit, Giardia duodenalis coproantigens were detected on all farms and in 25.4% (53/209) of pigs sampled. However, there was no significant influence (p > 0.05) of age, sex and stool consistencies of the pigs on the distribution of the infection. Genotyping of Giardia duodenalis in all ELISA-positive samples, achieved by the amplification of the small subunit ribosomal RNA (ssu rRNA), glutamate dehydrogenase (gdh), triosephosphate isomerase (tpi) and beta giardin (bg) genes, identified 14 and 37 assemblage B and E isolates respectively while mixed infection by both assemblages was recorded in two isolates. Novel nucleotide substitutions were identified in four assemblage B isolates at the ssu rRNA locus. Genetic diversity was observed among the assemblage B isolates after multiple alignment analyses of the gdh, tpi and bg sequences whereby sub-assemblages BII (n = 2), BIII (n = 9) and BIV (n = 3) were identified. The assemblage B isolates from pigs in this study were phylogenetically related to isolates from humans, marmoset and cattle while the assemblage E isolates were related to isolates from sheep, goats and cattle. These findings suggest that pigs in southwest Nigeria predominantly harbour G. duodenalis isolates that could be infectious to other animal species and to a lesser extent, isolates that may be of zoonotic importance.     

Sequence analysis and prokaryotic expression of Giardia lamblia α-18 giardin gene

To study the genetic variation and prokaryotic expression of α18 giardin gene of Giardia lamblia zoonotic assemblage A and host-specific assemblage F, the α18 genes were amplified from G. lamblia assemblages A and F by PCR and sequenced. The PCR product was cloned into the prokaryotic expression vector pET-28a(+) and the positive recombinant plasmid was transformed into Escherichia coli Rosetta (DE3) strain for the expression. The expressed α18 giardin fusion protein was validated by SDS-PAGE and Western blot analysis, and purified by Ni-Agarose resin. The putative sequence of α18 giardin amino acid was analyzed by bioinformatics software. Results showed that the α18 giardin gene was 861 bp in length, encoding 286 amino acids; it was 100% homologous between human-derived and dog-derived G. lamblia assemblage A, but it was 86.8% homologous with G. lamblia assemblage F (cat-derived). Giardin α18 was about 36 kDa in molecular weight, with good reactivity. Prediction based on in silico analyses: it had hydrophobicity, without signal peptide and transmembrane domain, and contained 11 alpha regions, 13 beta sheets, 1 beta turn and 7 random coils in secondary structure. The above information would lay the foundation for research about the subcellular localization and biological function of α18 giardin in G. lamblia.     

Molecular Identification of Giardia duodenalis Isolates from Fars Province,Iran

Background

Giardia duodenalis is one of the most common human intestinal protozoan parasites worldwide and is endemic throughout the world with a vast range of mammalian hosts. The present study aimed to identify the prevalence of G. duodenalis isolates and determine the most common of its assemblages in the patients referring to health centers and hospitals in Fars province, Iran that will be subjected to further molecular investigation.

Methods

We collected 1000 human fecal samples from health centers and hospitals in Shiraz, Iran in a one year period from September 2009 to August 2010. Microscopic examination for the presence of G. duodenalis cysts and trophozoites was performed by direct wet mount before and after the concentration techniques. Extraction of DNA was performed by Phenol-Chloroform-Isoamylalcohol (PCI). G. duodenalis-positive specimens were analyzed by PCR. A fragment of the SSU-rDNA (292 bp) gene was amplified by PCR using the forward primer RH11 and the reverse primer RH4. Genotyping was performed using sequence analysis of G. duodenalis glutamate dehydrogenase gene using primers GDHeF, GDHiF, and GDHiR.

Results

The prevalence of Giardia infection was 10.7% (107/1000) examined based on microscopic examination. PCR identified 80% (40/50) of the samples as positive for G. duodenalis based on SSU-rDNA amplification on sucrose gradient samples. Besides, genotyping results indicated 32 isolates (80%) as assemblage AII and 8 isolates (20%) as assemblage BIII and BIV based on the DNA sequence analysis of the glutamate dehydrogenase locus of G. duodenalis.

Conclusion

The findings of this study emphasize that Iran (Fars Province) is a favorable area for giardiasis with an anthroponotic infection route.     

Investigation of Possible Correlation between Giardia duodenalis Genotypes and Clinical Symptoms in Southwest of Iran

Background

Giardia duodenalis is one of the most important human enteric parasites throughout the world. Clinical symptoms of this parasite vary from asymptomatic infection to chronic diarrhea. Still it is not clear, whether different types of pathogenesis are due to different strains of organism or to variable host factors. The purpose of this study was to investigate possible correlation of clinical symptoms with assemblages among symptomatic and asymptomatic cases collected from southwest of Iran.

Methods

Fecal samples were collected from 100 symptomatic and asymptomatic cases, which were positive for G. duodenalis. The samples were subjected to semi-nested PCR and RFLP for gdh gene.

Results

Among symptomatic patients, 54% had mixed genotypes AII and BIII, 28% and 18% of samples indicated assemblages BIII and AII, respectively. In contrast, among asymptomatic cases, 64%, 26% and 10%samples had mixed genotypes, BIII and AII assemblages, respectively. Statistical analysis using Chi- Square test showed that there was no significant correlation between assemblage and clinical symptoms in current study.

Conclusion

High prevalence of mixed infection in both groups may affect this conclusion, therefore further study in more details are necessary to clarify these finding. Additionally, it is important to carry out investigations regarding human host factors as well.     

New insight into the epidemiology of rabbit hemorrhagic disease viruses in Portugal: Retrospective study reveals the circulation of genogroup 5 (G5) in Azores and discloses the circulation of G1 and G6 strains in mainland until 2008

The genetic relationships between 10 rabbit hemorrhagic disease strains collected in Portugal between 2006 and 2013, originated in the mainland and Azorean islands, were investigated based on the vp60 gene variability. A genetic diversity ranging from 2% to 13% was determined among the 10-vp60 complete sequences revealing a significant level of genetic heterogeneity between same strains. Phylogenetic Bayesian analysis showed that the Portuguese RHDV strains fell within different genogroups, namely G1, G5 and G6. Interestingly, all strains obtained from Azores, where RHDV was first detected in 1988, belong to G5 genogroup. G5 strains, that were not identified in the continent so far, seem to be the dominant group in these Atlantic islands.G1-related strains belonging to the Iberian group 3 (n = 3) and G6 (RHDVa) strains (n = 2) were identified among the samples originated in mainland which were collected between 2006 and 2008. Although the presence of G1 and G6 in Portugal had been shown before, our data refines the time of circulation of these strains until at least 2008.In summary, this study revises the epidemiological information of RHDV in Portugal since it reports for the first time the presence of G5 strains in Azores and demonstrates the circulation of G1 and G6 strains in mainland Portugal until the late 2000s.     

High genetic diversity of Giardia duodenalis assemblage E in Chinese dairy cattle

Giardia duodenalis is a common protozoan parasite that can infect humans and animals. Although previous studies demonstrated that the assemblage E of G. duodenalis is prevalent in cattle, studies on its genetic diversity were mostly based on single loci and very few involved multilocus analysis. To better understand the genetic variability and structure of G. duodenalis assemblage E in Chinese dairy cattle, 651 multilocus sequences derived from nine provinces (Gansu, Guangdong, Henan, Jiangsu, Ningxia, Shaanxi, Shanghai, Sichuan and Xinjiang) of China were analyzed in this study. Results showed that a total of 220 haplotypes were identified in the G. duodenalis assemblage E, with a high haplotype diversity (Hd = 0.97225) and low nucleotide diversity (π = 0.00259). The genetic differentiation index (FST) and gene flow (Nm) results indicated low degree of genetic differentiation, implying frequent genetic communication. Combined with the analysis of molecular variance (AMOVA), genetic variation within populations (81.7%) was higher than that among populations (18.3%), indicating low degree of genetic differentiation between populations. Such low rates of gene differentiation supported no significant correlations with geographical divisions. Moreover, both negative Tajima's D and Fu's FS values of neutrality tests and unimodal curve of mismatch distribution analyses indicated that G. duodenalis assemblage E population in Chinese dairy cattle had experienced demographic expansion. Overall, these findings contribute to an improved understanding of the population genetics and evolutionary biology of G. duodenalis assemblage E and assist in its control in cattle.