Giardia lamblia: effect of infection with symptomatic and asymptomatic isolates on the growth of gerbils (Meriones unguiculatus)

The Cysteine Protease Giardipain-1 from Giardia duodenalis Contributes to a Disruption of Intestinal Homeostasis

In giardiasis, diarrhoea, dehydration, malabsorption, weight loss and/or chronic inflammation are indicative of epithelial barrier dysfunction. However, the pathogenesis of giardiasis is still enigmatic in many aspects. Here, we show evidence that a cysteine protease of Giardia duodenalis called giardipain-1, contributes to the pathogenesis of giardiasis induced by trophozoites of the WB strain. In an experimental system, we demonstrate that purified giardipain-1 induces apoptosis and extrusion of epithelial cells at the tips of the villi in infected jirds (Meriones unguiculatus). Moreover, jird infection with trophozoites expressing giardipain-1 resulted in intestinal epithelial damage, cellular infiltration, crypt hyperplasia, goblet cell hypertrophy and oedema. Pathological alterations were more pronounced when jirds were infected intragastrically with Giardia trophozoites that stably overexpress giardipain-1. Furthermore, Giardia colonization in jirds results in a chronic inflammation that could relate to the dysbiosis triggered by the protist. Taken together, these results reveal that giardipain-1 plays a key role in the pathogenesis of giardiasis.

Prevalence and Associated Factors of Intestinal Helminths Among Kindergarten Children in Gondar Town, Northwest Ethiopia

BACKGROUND

Intestinal parasitic infections (IPIs) are small organisms that infect the gastro-intestinal tract of human beings. Causes malnutrition, iron deficiency anemia, impairment of physical and mental development in children. The aim of this study was to determine the prevalence of intestinal helminthiasis and associated factors among Kindergarten (KG) children in Gondar Town, northwest Ethiopia.

METHODS

Institution-based cross-sectional study was conducted on 390 Kindergarten children in Gondar town, Northwest, Ethiopia from March to May 2019. Study subjects were selected using systematic random sampling method. Data were gathered through direct interview by using a pretested questionnaire. Stool specimens were collected and examined using Kato Katz technique. Chi square was used to assess the association between variables and p-value less than 0.05 was taken as a statistical significance.

RESULTS

The overall prevalence of intestinal helminthiasis was 16.7%, while those of participants infected by soil-transmitted helminths (STHs) and intestinal Schistosomiasis were 13.8% and 5.9%, respectively. Ascaris lumbricoides was the predominant STHs (9%) followed by Trichuris trichiura (2.3%) and hookworm (1.5%). Light infection was observed in almost all of the infected study participants. Intestinal helminthiasis was found to be significantly associated with age, KG level of children, maternal occupation, and educational status of parents.

CONCLUSION

A significant number of children were infected by intestinal parasites in the study area. A. lumbricoides and intestinal Schistosomiasis were the most predominant of the isolated parasites.

Animal Models of Undernutrition and Enteropathy as Tools for Assessment of Nutritional Intervention

: Undernutrition is a major public health problem leading to 1 in 5 of all deaths in children under 5 years. Undernutrition leads to growth stunting and/or wasting and is often associated with environmental enteric dysfunction (EED). EED mechanisms leading to growth failure include intestinal hyperpermeability, villus blunting, malabsorption and gut inflammation. As non-invasive methods for investigating gut function in undernourished children are limited, pre-clinical models are relevant to elucidating the pathophysiological processes involved in undernutrition and EED, and to identifying novel therapeutic strategies. In many published models, undernutrition was induced using protein or micronutrient deficient diets, but these experimental models were not associated with EED. Enteropathy models mainly used gastrointestinal injury triggers. These models are presented in this review. We found only a few studies investigating the combination of undernutrition and enteropathy. This highlights the need for further developments to establish an experimental model reproducing the impact of undernutrition and enteropathy on growth, intestinal hyperpermeability and inflammation, that could be suitable for preclinical evaluation of innovative therapeutic intervention.

Host specificity in the Giardia duodenalis species complex

Giardia duodenalis is a unicellular flagellated parasite that infects the gastrointestinal tract of a wide range of mammalian species, including humans. Investigations of protein and DNA polymorphisms revealed that G. duodenalis should be considered as a species complex, whose members, despite being morphologically indistinguishable, can be classified into eight groups, or Assemblages, separated by large genetic distances. Assemblages display various degree of host specificity, with Assemblages A and B occurring in humans and many other hosts, Assemblage C and D in canids, Assemblage E in hoofed animals, Assemblage F in cats, Assemblage G in rodents, and Assemblage H in pinnipeds. The factors determining host specificity are only partially understood, and clearly involve both the host and the parasite. Here, we review the results of in vitro and in vivo experiments, and clinical observations to highlight relevant biological and genetic differences between Assemblages, with a focus on human infection.

Predominance of Giardia lamblia assemblage A among iron deficiency anaemic pre-school Egyptian children

Intestinal parasites and nutritional deficiency can coexist and influence each other. This study aimed to clarify the association between Giardia genotypes and presence of iron deficiency anaemia (IDA) among pre-school Egyptian children. Two groups (IDA and non-anaemic) of giardiasis children (44/group) were selected according to their recovery response after treatment of giardiasis. Each group included 24 and 20 gastrointestinal symptomatic and asymptomatic, respectively. Giardia human genotypes were performed by intergenic spacer (IGS) gene based polymerase chain reaction (PCR) with high-resolution melting curve (HRM). PCR/HRM proved that Tms of assemblage A and B ranged from 79.31 ± 0.29 to 84.77 ± 0.31. In IDA patients, assemblages A and B were found among 40/44 (90.9 %) and 4/44 (9.1 %), respectively, while in non-anaemic patients, assemblages A and B were found in 10/44 (22.7 %) and 32/44 (72.7 %), respectively, beside two (4.6 %) cases had mixed infection. The difference was statistically significant. No significant relation was found between symptomatic or asymptomatic assemblages and IDA as assemblage A was found in 21/24 (87.5 %) and 19/20 (95 %) of symptomatic and asymptomatic, respectively, while 3/24 (12.5 %) and 1/20 (5 %) of assemblage B were symptomatic was asymptomatic, respectively. A significant relation was found between assemblage A subtypes distribution among IDA patients as AI and AII were detected on 23 (52.3 %) and 16 (36.4 %) of patients, respectively, while one case (2.3 %) had mixed infection. In conclusion, assemblage A is predominant among IDA giardiasis children suggesting its role in enhancing the occurrence of IDA while B has a protective role.

The invasive potential of Giardia intestinalis in an in vivo model

Giardiasis is a neglected parasitic disease that affects primarily children, in whom it delays physical and mental development. The pathophysiology of giardiasis in not well understood, and most reports have identified Giardia intestinalis trophozoites only in the lumen and on the brush border of the small intestine. We identified Giardia trophozoites within the epithelium of the small intestine of a lactose intolerance patient. The Giardia trophozoites were obtained and cultured in vitro. In addition, we demonstrated Giardia trophozoite invasion in an animal model. Giardia trophozoites invaded the intestinal mucosa and submucosa of infected gerbils. The invasive trophozoites were observed at 21, 30 and 60 days age, and the average numbers of invaded sites were 17 ± 5, 15 ± 4, and 9 ± 3, respectively. We found trophozoites between epithelial cells, at the base of empty goblet cells, in lacteal vessels and within the submucosa. The morphological integrity of the invasive trophozoites was demonstrated via electron microscopy. The analysis of the gerbils infected with the trophozoites of the WB reference strain did not show intraepithelial trophozoites. These results demonstrate another Giardia pathogenic mechanism, opening the door to numerous future studies.

Prevalence of Giardia intestinalis and Hymenolepis nana in Afghan refugee population of Mianwali district, Pakistan

BACKGROUND

Present study aimed to investigate prevalence of Giardia intestinalis and Hymenolepis nana in Afghan refugees visiting Central Health Unit (CHU), Kot Chandana (Mianwali, Northern Punjab) during two years period (February 2007 to December 2009).

METHODS

A total of 687 stool samples were collected from different age groups of both genders. Samples were processed under sterile conditions after gross examination. Microscopic examination was done on same day along with eggs (H. nana), cyst and trophozoites (G. intestinalis) detection after staining.

RESULTS

The prevalence of G. intestinalis was significantly higher (x2=59.54, p<0.001) than that of H. nana. Females were found more likely to be infected as compared to males (OR: 1.40, 95% CI=1.03-1.92). Prevalence of both parasites decreased with age and highest prevalence was observed in young individuals belonging to 1-15 years of age group (41.8% and 48.7% respectively for H. nana and G. intestinalis, p<0.001). Abdominal distress (OR: 1.13, 95%CI=0.83-1.53), vomiting (OR: 1.13, 95%CI=1.13-1.81) and rectal prolapse (OR: 4.26, 95%CI=1.38-13.16) were the gastro-intestinal clinical symptoms observed in G. intestinalis. Whereas, bloody diarrhea (OR: 1.56, 95%CI=1.00-2.43) and rectal prolapse (OR: 5.79, 95%CI=1.87-17.91) were associated with H. nana infections.

CONCLUSIONS

Intestinal parasitic infections are common among Afghan refugees and serious preventive measures should be implemented to promote the safety and healthy lifestyle of these people.

Marked antigiardial activity of Yucca baccata extracts: a potential natural alternative for treating protozoan infections

Human Giardiosis is a public health problem in Mexico, where the national prevalence was estimated to be up to 68%. Misuse of antiprotozoal drugs may result in low effectiveness and undesirable side effects. Research on natural products is a good strategy for discovering more effective antiparasitic compounds. This study evaluated the antigiardial activity of extracts of Yucca baccata, which is native to northwestern Mexico. Forty-two gerbils (females) were weighed and orally inoculated with 5 × 10⁶ Giardia trophozoites. Two gerbils were selected at random to confirm infection. Forty living gerbils were randomly allocated into 5 treatment groups (8 per group). Gerbils were randomly assigned to be treated with 24.4 mg/mL, 12.2 mg/mL, and 6.1 mg/mL of extracts, metronidazole (2 mg/mL) or PBS, which were intragastrically administered once per day for 3 days. Nine gerbils died during the study course. On day 10 postinfection, gerbils were euthanized and trophozoites were quantified. Yucca extracts reduced, albeit not significantly, the trophozoite counts in the duodenum segment. Only the high-extract concentration significantly reduced the trophozoite counts in the proximal segment and it was similar to that of metronidazole. Extracts of Y. baccata may represent an effective and natural therapeutic alternative for human giardiosis.

Effects of dietary zinc manipulation on growth performance, zinc status and immune response during Giardia lamblia infection: a study in CD-1 mice

Associations between Giardia lamblia infection and low serum concentrations of zinc have been reported in young children. Interestingly, relatively few studies have examined the effects of different dietary zinc levels on the parasite-infected host. The aims of this study were to compare the growth performance and zinc status in response to varying levels of dietary zinc and to measure the antibody-mediated response of mice during G. lamblia infection. Male CD-1 mice were fed using 1 of 4 experimental diets: adequate-zinc (ZnA), low-zinc (ZnL), high-zinc (ZnH) and supplemented-zinc (ZnS) diet containing 30, 10, 223 and 1383 mg Zn/kg respectively. After a 10 days feeding period, mice were inoculated orally with 5 × 10⁶G. lamblia trophozoites and were maintained on the assigned diet during the course of infection (30 days). Giardia-free mice fed ZnL diets were able to attain normal growth and antibody-mediated response. Giardia-infected mice fed ZnL and ZnA diets presented a significant growth retardation compared to non-infected controls. Zinc supplementation avoided this weight loss during G. lamblia infection and up-regulated the host’s humoral immune response by improving the production of specific antibodies. Clinical outcomes of zinc supplementation during giardiasis included significant weight gain, higher anti-G. lamblia IgG antibodies and improved serum zinc levels despite the ongoing infection. A maximum growth rate and antibody-mediated response were attained in mice fed ZnH diet. No further increases in body weight, zinc status and humoral immune capacity were noted by feeding higher zinc levels (ZnS) than the ZnH diet. These findings probably reflect biological effect of zinc that could be of public health importance in endemic areas of infection.

Giardia: both a harmless commensal and a devastating pathogen

The highly prevalent protozoan Giardia lamblia is an enteropathogen that can be asymptomatic in some individuals, while leading to persistent diarrhea and substantial morbidity in others. In this issue of the JCI, Bartelt et al. describe a mouse model of the disease and investigate the contribution of coincident malnutrition with the development of symptomatic infection. This work in part explains how Giardia infection can lead to growth retardation, and may offer insights that guide future therapeutic strategies.

In vitro activity of the F-6 fraction of oregano against Giardia intestinalis

Giardiosis is a neglected parasitic disease that produces diarrhoea and different degrees of malabsorption in humans and animals. Its treatment is based on derivatives of 5-nitroimidazoles, benzimidazoles, nitrofuranes, acridine and nitrotiazoles. These drugs produce undesirable secondary effects, ranging from a metallic taste in the mouth to genetic damage and the selection of resistant strains; therefore, it is necessary to develop new therapeutic alternatives. We demonstrated that a 2-h treatment with 2·87 μg ml(-1) of fraction 6 of Lippia graveolens (F-6) was sufficient to kill half of an experimental Giardia intestinalis (Syn. G. duodenalis, G. lamblia) population, based on the reduction of MTT-tetrazolium salt levels. F-6 breaks the nuclear envelope and injures the ventral suckling disc. The major compounds of F-6 were characterized as naringenin, thymol, pinocembrin and traces of compounds not yet identified. The results suggest that Lippia is a potential source to obtain compounds with anti-Giardia activity. This knowledge is an important starting point to develop new anti-giardial drugs. Future studies will be required to establish the efficacy of F-6 in vivo using an animal model.

Intestinal growth and pathology of Giardia duodenalis assemblage subtype A(I), A(II), B and E in the gerbil model

This study investigated the significance of the genetic differences between assemblages A, B and E on intestinal growth and virulence. Intestinal growth and virulence were studied in 2 laboratory (A(I): WB and B: GS/M-83-H7) and 6 field isolates of assemblage subtype A(I), A(II), B and E(III). Intestinal trophozoite burdens, body weight and faecal consistency were monitored until day 29 post-infection (p.i.), morphological (mucosal architecture and inflammation) and functional (disaccharidase and alkaline phosphatase enzyme activity) damage to the small intestine were evaluated on days 7 and 18 p.i. The assemblage subtypes A(I) and B were more infectious and produced higher trophozoite loads for a longer period compared to the subtypes A(II) and E(III). The body weight of infected gerbils was significantly reduced compared to uninfected controls, but did not differ between the assemblage subtypes. Consistent softening of the faeces was only observed with assemblage B. Assemblage B next to assemblage subtype A(I) elicited relatively higher pathogenicity, characterized by more extensive damage to mucosal architecture, decreased brush-border enzyme function and infiltration of inflammatory cells. Assemblage E(III) and A(II) isolates showed relatively low virulence. The Giardia assemblage subtypes exhibit different levels of growth and virulence in the gerbil model.

Molecular epidemiology of Giardia duodenalis in an endangered carnivore--the African painted dog

The African painted dog (Lycaon pictus) is an endangered carnivore of sub-Saharan Africa. To assist in conservation efforts a parasitological survey was conducted on wild and captive populations. Faecal samples were collected and examined for the presence of parasites using traditional microscopy techniques. The protozoan Giardia duodenalis was identified at a prevalence of approximately 26% in the wild populations and 62% in the captive population. Molecular characterisation of these isolates using three loci, 18S rRNA, β-giardin and the glutamate dehydrogenase gene revealed the zoonotic assemblages A and B existed in high proportions in both populations. The dog assemblages C and D were rarely observed. The identification of the zoonotic genotype suggests this species has the potential to act as a reservoir for human infections. Zoonotic transmission may be possible in captive populations due to the close interaction with humans however, in wild populations anthropozoonotic transmission seems more likely. This study is the first to observe G. duodenalis in the African painted dog and to identify a possible emerging disease in this wild carnivore.

Giardia in symptomatic dogs and cats in Europe--results of a European study

The percentage of Giardia infection in dogs and cats with gastrointestinal signs presenting to clinics was examined across Europe using the IDEXX SNAP Giardia Test (IDEXX Laboratories). Veterinary practices were asked to identify diarrheic and/or vomiting dogs and cats and to use the test on fecal samples from these animals. A selection for "asymptomatic" testing was also available on the data collection sheet for testing that occurred outside the target "symptomatic" population. Results from 8685 dogs and 4214 cats were submitted during the sampling period from 2005 to 2006. Analysis of the data showed 24.78% of the samples positive for Giardia among tested dogs and 20.3% among tested cats. The younger the dog or the cat, the higher the risk of being positive, peaking in the category below 6 months. The main clinical symptom, diarrhoea, also showed a higher risk of being positive, OR's of acute diarrhoea were almost double of those of the category "asymptomatic" for dogs or cats, the same range was calculated for chronic diarrhoea. Differences in participating countries were also seen. The risk of being positive was half or less in UK, Spain, Netherlands, Italy compared to Germany, and only in Belgium it showed to be higher. The results of this study show that Giardia is a common enteric agent among dogs and cats with gastrointestinal signs in Europe.

Giardia intestinalis and nutritional status in children participating in the complementary nutrition program, Antioquia, Colombia, May to October 2006

Giardia intestinalis infection is prevalent throughout the world and widely distributed in developing countries. In general, children display serious consequences to their state of health, including slow height-weight development; therefore, the main aim of this study was to determine the association between Giardia infection and the nutritional status of children who participate in the program of complementary feeding (Mejoramiento Alimentario y Nutricional de Antioquia (MANA) - Instituto Colombiano de Bienestar Familiar (ICBF)). A cross-sectional study examining the association of giardiasis with nutritional status was conducted. A total of 2035 children aged eight months to six years-old were studied. Data were collected using structured questionnaires, anthropometric measurements and laboratory analysis of blood and stool samples. Analysis of the results showed that 27.6% of children were infected with G. intestinalis, while 8.1% and 1.9% were mildly and significantly underweight, respectively, and 14.1% presented stunting. Giardiasis was statistically identified as a strong predictor of stunting in this study population.

Prevalence of enteroparasites and genotyping of Giardia lamblia in Peruvian children

Enteroparasites in children from three marginal urban districts of Trujillo (Peru) were studied to treat these children and to design a prevention and control programme. A total of 845 children were examined. The general prevalence of enteroparasites was of 66.3%, and 45.6% were multiparasitized. The pathogenic enteroparasite prevalence were 23.8% (Giardia lamblia), 4.6% (Iodamoeba buschlii), 2.6% (Cyclospora cayetanensis), 2.2% (Hymenolepis nana), and 2% (Cryptosporidium spp.). G. lamblia was the most frequent parasite both in diarrheic children (28.1%) as well as in nondiarrheic ones (19.5%). The G. lamblia genotypes were molecularly characterized by sequence analysis of the glutamate dehydrogenase (gdh) gene using PCR and RFLP. Sequence analysis revealed both Assemblage A (AI and AII) and Assemblage B (BIV), with the predominance of Assemblage AI. All the samples with Assemblage A were diarrheic but not those with Assemblage B. This is the first study of molecular characterization of G. lamblia in Peruvian children and confirms the importance of asymptomatic patients in the transmission of the giardiosis, especially in places with poor hygiene and sanitation.

Goblet cells: are they an unspecific barrier against Giardia intestinalis or a gate?

Giardiosis is one of the major intestinal parasitic diseases of human beings as well as wild and domesticated animals. Several protective mechanisms against infection have been described. However, specific information about relationship between giardiosis and the increased proliferation of goblet cells (GC) in patients infected with Giardia intestinalis (Syn. G. duodenalis, G. lamblia) is scarce. In this work, we compare and quantify the number of GC, and have inferred their metabolic state in the small intestine of dogs parasitized with Giardia intestinalis compared to dogs without parasites. Small intestine segments were processed using routine methods for histology and electron microscopy; areas and cells were screened with an Axiovision Ver. 4.0 system. Data were analyzed by ANOVA and comparison of averages. Parasitized dogs showed higher GC numbers than nonparasitized ones. Averages were: 20+/-0.81 GC/25 microm(2) with independent mucin granules and 11+/-1.53 GC/25 microm(2) that were expelling mucus, compared to 11+/-0.94 GC/25 microm(2) and 1+/-0.27 GC/25 microm(2), respectively, in nonparasitized dogs (Tukey, p<0.001). The increases in GC number seem to be an unspecific defensive mechanism against Giardia trophozoites. However, we found some evidence supporting that GC hyperplasia could be a prejudicial to epithelial barrier that gives rise to gates allowing for Giardia-tissue invasion.

Intestinal parasitism in Peruvian children and molecular characterization of Cryptosporidium species

Intestinal parasitism was studied in children of Trujillo (Peru) to create a prevention and control program. Fecal samples of 489 children were examined. The general prevalence of intestinal parasitosis was found to be 68%. The most frequent pathogenic enteroparasites were Giardia lamblia (26.4%), Cyclospora cayetanensis (13%), Hymenolepis nana (2%), Hymenolepis diminuta (1.6%), and Cryptosporidium spp. (1%). All these parasites appeared both in diarrheic and nondiarrheic children, except Cryptosporidium, which invariably caused diarrhea. Multiple parasitism was frequent, 45.6% of the children presenting two, three, or four intestinal parasites. Cryptosporidium was the only parasite that was not associated with the others. Only five children were affected of cryptosporidiosis, presenting explosive diarrhea, nausea, and vomiting. Cryptosporidium species and genotypes involved in the infantile cryptosporidiosis were determined by polymerase chain reaction-restriction fragment length polymorphism. Four children were parasitized by Cryptosporidium hominis and only one by Cryptosporidium parvum. Our results confirm that anthroponotic transmission of Cryptosporidium is predominant in Peru.

Oregano (Lippia spp.) kills Giardia intestinalis trophozoites in vitro: antigiardiasic activity and ultrastructural damage

In the world, giardiosis is still a very important parasitic disease; only in Asia, Africa and America, there are more than 200 million of infected people in a year. The usual treatments are drugs that produce undesirable secondary effects, perhaps favouring the resistant strain selection. One alternative is to research compounds from plants used as antidiarrhoeic or antiparasitic in the traditional medicine. In a previous work, we found that Lippia beriandieri (Oregano) revealed to be more potent than tinidazole, a common antigiardiasic drug. In this current work, we tested the cell viability by re-culture and reduction of MTT-tetrazolium salts to MTT-formazan, and we showed the effect of oregano ethanolic extracts against Giardia intestinalis (synonyms: Giardia duodenalis, Giardia lamblia) trophozoites at concentrations ranging form 58 to 588 microg. We demonstrated the ultrastructural injury produced by oregano extracts in this parasite. Trophozoites lost their size and shape and showed damage in nucleus structure, perhaps by breaking the pattern of nucleoskeleton proteins.

Effects of giardiasis on school success, weight and height indices of primary school children in Turkey

BACKGROUND

Giardia intestinalis, the most common parasite in the world, causes several adverse effects on school children, with the prevalence rate ranging between 7.3% and 28% (mean 13.8%) in Turkey. The aim of the present study was to investigate possible adverse effects of G. intestinalis on success at school, and the mean weight and height of primary school children in Sivas, Turkey.

METHODS

Five primary schools from central Sivas, Turkey, had a number of students from different socioeconomic conditions and regions. The stool specimens were examined by light microscopy for giardiasis using saline-Lugol and/or zinc sulfate flotation method. Three groups in the present study include the symptomatic giardiasis group (SG), which included children with giardiasis along with abdominal pain and/or diarrhea, the asymptomatic giardiasis group (ASG) without any symptom and the non-parasitic (NPG) group without any parasites.

RESULTS

While 599 (34.6%) out of 1730 children were parasitic, 192 (11.1%) had only G. intestinalis. Ninety-eight (5.7%) of 192 were SG (with diarrhea and/or abdominal pain and 94 (5.4%) were ASG. The weights and heights were lower in the children with giardiasis than the children without any parasite. There was a significant difference between the giardiasis group and NPG when the numbers of persons living in the house were compared. While there were no significant difference between the giardiasis group and NPG when the sexes were compared, success at school and economical levels were found to be significantly different between these groups.

CONCLUSION

There was a higher prevalence of giardiasis in primary school children and their physical and mental conditions were affected adversely. Giardia infections in particular have adverse effects on success at school.

Giardia intestinalis and other zoonotic parasites: Prevalence in adult dogs from the southern part of Mexico City

The protozoan Giardia intestinalis is a mammalian-infecting parasite. It produces diarrhoea and malabsorption in its hosts. There is growing evidence that dogs could be reservoirs and play an important role in transmission. In Mexico, there are few data on the frequency of G. intestinalis. Therefore, we studied the small intestine of stray dogs, euthanazed at the "Culhuacan" Control Canine Centre, towards the end of 1997 and during the summer of 1998. We microscopically analysed intestinal contents and mucus samples taken every 3cm. During the cold season (winter), parasites were not found in 38/100 dogs, in contrast to 8/100 through the warm season. We found that 42/100 in winter and 51/100 in summer harboured G. intestinalis. To our knowledge, these G. intestinalis frequencies are the highest found in adult dogs worldwide. The results showed a rise in Ancylostoma spp. from 23/100 to 67/100 during the cold and warm seasons. Toxocara canis frequencies varied between 12/100 and 18/100, respectively. The data suggest that the probability of infection is higher during the hottest months compared to the coldest months of the year. Both puppies and adult dogs are highly infected. Dogs are reservoirs for zoonotic parasites; for this reason, it is imperative for humans to avoid fecal contamination in streets, public gardens and parks.

Variation in Giardia: implications for taxonomy and epidemiology

The taxonomy, life cycle patterns and zoonotic potential of Giardia infecting mammals and birds have been poorly understood and controversial for many years. The development of molecular tools for characterising isolates of Giardia directly from faeces or environmental samples has made an enormous contribution to resolving these issues. It is now clear that the G. duodenalis morphological group is a species complex comprising a series of what appear to be largely host-adapted species, and at least two zoonotic species for which humans are the major host, but which are also capable of infecting other mammals. It is proposed that this new information be reflected in the redesignation of several species of Giardia described previously. The molecular epidemiological tools that are now available need to be applied in different endemic foci of Giardia transmission, as well as in outbreak situations, in order to understand better the frequency of zoonotic transmission as well as to develop more effective approaches to controlling giardiasis.

Molecular characterization of Brazilian human Giardia duodenalis isolates using isoenzyme and random amplified polymorphic DNA analysis

Isoenzymes and RAPD (random amplified polymorphic DNA) analysis were used to characterize three Brazilian human isolates of Giardia duodenalis and its clones. The Portland-1 strain (ATCC 30888) was included in the study as a reference pattern. Both methods divided the isolates into two main groups, one represented by the Portland-1 strain, the other constituted by the Brazilian isolates, which, in turn, were divided into 2 subgroups. The dendogram constructed with the RAPD data, using seven primers, revealed a great heterogeneity between Brazilian isolates and the Portland-1 strain. There was no relationship to the clinical characteristics of the isolates. Although a lot of similarity has been observed among Brazilian isolates and its clones, individual polymorphism was detected, which could be related to the clonal reproduction of this protozoan.

Genetic homogeneity of axenic isolates of Giardia intestinalis derived from acute and chronically infected individuals in Mexico

Twenty-six axenic isolates of Giardia intestinalis, established in Mexico City over an 11-year period from symptomatic and asymptomatic individuals with acute or chronic infections, were typed genetically. A segment of the glutamate dehydrogenase gene was amplified by PCR and examined by restriction analysis using BspH1 and ApaI to determine the major genetic assemblages to which the isolates belonged. This was coupled with the amplification and analysis of segments of variant-specific surface protein genes to determine genetic subgroupings. Despite their heterogeneous clinical backgrounds, the isolates were found to be genetically homogeneous-all belonging to genetic group I of assemblage A. The results show that type A-I G. intestinalis is ubiquitous in Mexico City and that host factors play an important, if not dominant, role in determining the clinical outcome of Giardia infections in humans.

Mucosal defences against Giardia

Giardia lamblia (syn. G. duodenalis or G. intestinalis), the causative agent of giardiasis, is one of the most common causes worldwide of intestinal infections in humans. Symptomatic infection is characterized by diarrhoea, epigastric pain, nausea, vomiting, and weight loss, yet many infections are asymptomatic. The protozoan, unicellular parasite resides in the lumen and attaches to the epithelium and overlying mucus layers but does not invade the mucosa and causes little or no mucosal inflammation. Giardiasis is normally transient, indicating the existence of effective host defences, although re-infections can occur, which may be related to differences in infecting parasites and/or incomplete immune protection. Mucosal defences against Giardia must act in the small intestinal lumen in the absence of induction by classical inflammatory mediators. Secretory IgA antibodies have a central role in anti-giardial defence. B cell-independent mechanisms also exist and can contribute to eradication of the parasite, although their identity and physiological importance are poorly understood currently. Possible candidates are nitric oxide, antimicrobial peptides such as Paneth cell alpha-defensins, and lactoferrin. Elucidation of the key anti-giardial effector mechanisms will be important for selecting the best adjuvants in the rational development of vaccination strategies against Giardia.

Intestinal infection with Giardia spp. reduces epithelial barrier function in a myosin light chain kinase-dependent fashion

BACKGROUND & AIMS

Giardiasis causes malabsorptive diarrhea, and symptoms can be present in the absence of any significant morphologic injury to the intestinal mucosa. The effects of giardiasis on epithelial permeability in vivo remain unknown, and the role of T cells and myosin light chain kinase (MLCK) in altered intestinal barrier function is unclear. This study was conducted to determine whether Giardia spp. alters intestinal permeability in vivo, to assess whether these abnormalities are dependent on T cells, and to assess the role of MLCK in altered epithelial barrier function.

METHODS

Immunocompetent and isogenic athymic mice were inoculated with axenic Giardia muris trophozoites or sterile vehicle (control), then assessed for trophozoite colonization and gastrointestinal permeability. Mechanistic studies using nontransformed human duodenal epithelial monolayers (SCBN) determined the effects of Giardia on myosin light chain (MLC) phosphorylation, transepithelial fluorescein isothiocyanate-dextran fluxes, cytoskeletal F-actin, tight junctional zonula occludens-1 (ZO-1), and MLCK.

RESULTS

Giardia infection caused a significant increase in small intestinal, but not gastric or colonic, permeability that correlated with trophozoite colonization in both immunocompetent and athymic mice. In vitro, Giardia increased permeability and phosphorylation of MLC and reorganized F-actin and ZO-1. These alterations were abolished with an MLCK inhibitor.

CONCLUSIONS

Disruption of small intestinal barrier function is T cell independent, disappears on parasite clearance, and correlates with reorganization of cytoskeletal F-actin and tight junctional ZO-1 in an MLCK-dependent fashion.

Sensitive PCR-restriction fragment length polymorphism assay for detection and genotyping of Giardia duodenalis in human feces

An assay that uses heminested PCR-restriction fragment length polymorphism analysis for the detection and genotyping of Giardia duodenalis on the basis of polymorphism in the triose phosphate isomerase (tpi) gene was developed. This assay was evaluated with DNA extracted from purified parasite material, bacterial cultures, whole human feces containing G. duodenalis and other parasites, and their corresponding immunofluorescence-stained fecal smears on glass microscope slides. The assay was specific and discriminated between G. duodenalis assemblages A and B. RFLP analysis further distinguished two groups (designated groups I and II) within assemblage A. Among 35 DNA samples extracted from whole feces from patients with confirmed sporadic giardiasis, the tpi gene was amplified from 33 (94%). Of these, nine (27%) samples contained assemblage A group II, 21 (64%) contained assemblage B, and 3 (9%) contained a mixture of assemblage A group II and assemblage B. The tpi gene of G. duodenalis assemblage B was amplified from 21 of 24 (88%) DNA samples extracted from whole feces from patients with confirmed cases of infection in a nursery outbreak. No amplification was detected from the remaining three DNA samples. Overall, analysis of DNA extracted from material recovered from stained microscope slides identified identical G. duodenalis genotypes in 35 (65%) of the 54 samples for which a genotype was established with DNA from whole feces. The heminested PCR method developed is sensitive, simple, and rapid to perform and is applicable for the analysis of other intestinal pathogens.

Human giardiasis: genotype linked differences in clinical symptomatology

Giardia duodenalis infection in humans can cause a variety of clinical symptoms. The relation between clinical symptomatology and the Giardia isolate genotype was studied in 18 Dutch patients infected with G. duodenalis who visited their general practitioner. Contrary to earlier studies, a 100% correlation between severity of diarrhoeal complaints and genotype was found: assemblage A isolates were solely detected in patients with intermittent diarrhoeal complaints, while assemblage B isolates were present in patients with persistent diarrhoeal complaints. These results are significant because they show for the first time that genetically linked features of G. duodenalis are major determinants in the severity of infection in human giardiasis.