Duodenalis Infection Research Articles

Prevalence of Giardia duodenalis assemblages among dairy herds in the New York City Watershed

A longitudinal herd-level study was carried out to determine the cumulative incidence of Giardia duodenalis infections in dairy cattle in the New York City Watershed. We also sought to assess the changes in infection pattern of animals diagnosed as shedding Giardia over time, determine risk factors that may be associated with G. duodenalis infections, and identify potentially zoonotic infections. A total of 2109 fecal samples were randomly collected from dairy cattle at 34 farms in the New York City Watershed on a seasonal basis. A total of 504 Giardia-positive samples were identified by zinc sulfate flotation. The overall cumulative incidence of G. duodenalis based on flotation results was 23.9% with 73.8% of all infections occurring in animals under 180 days of age (372/504). The intensity of infection ranged from 2 to 563,200 cysts/gram of feces. Cattle shedding Cryptosporidium spp. oocysts were twice as likely to shed G. duodenalis cysts in comparison to the animals that did not shed oocysts (1.81 95% CI 1.26–2.60 p=0.0012). In the multivariate analysis, only the age of the animal and the presence of dogs on the farm were significantly associated with the likelihood of shedding G. duodenalis. DNA was extracted from positive samples and analyzed by polymerase chain reaction (PCR) of the beta-giardin and triosephosphate isomerase genes of Giardia spp. 304 samples were analyzed by PCR of which 131 were sequenced. 22.1% of sequenced samples were identified as assemblage A and 77.9% were identified as assemblage E. Interestingly, 100% of specimens identified as assemblage A were from calves under 84 days of age indicating that younger cattle are important reservoirs for potentially zoonotic assemblages of G. duodenalis.

Impacts of naturally acquired protozoa and strongylid nematode infections on growth and faecal attributes in lambs

On two separate sampling occasions, faecal samples were collected from lambs (2–5 months of age) grazing pasture on two separate sheep farms in southern Western Australia. Live weight, body condition score (BCS), faecal consistency score (FCS) and faecal dry matter percentage (DM%) were measured. Faecal samples were screened by PCR for Cryptosporidium (18S rRNA, actin and 60kDa glycoprotein [gp60] loci), Giardia duodenalis (glutamate dehydrogenase [gdh] and β-giardin) and patent strongylid nematode infections (ITS-2 nuclear ribosomal DNA for Haemonchus contortus, Teladorsagia circumcincta, Trichostrongylus spp. Chabertia ovina and Oesophagostomum spp.). Faecal worm egg counts (WECs) were performed using a modified McMaster WEC technique. The WECs were adjusted for FCS and transformed using log10(adjusted WEC+25) prior to statistical analyses.Cryptosporidium, Giardia and Trichostrongylus spp. detected by PCR were associated with an increased risk of non-pelleted faeces (FCS≥3.0) for both flocks. Cryptosporidium-positive lambs were 2.8–11.6 times more likely to have non-pelleted faeces and Giardia-positive lambs were 2.4–14.0 times more likely to have non-pelleted faeces compared to lambs negative for each respective parasite. Lambs positive for both Cryptosporidium and Giardia were 2.9–11.8 times more likely to have non-pelleted faeces than lambs positive for only one or neither of these parasites. Mixed internal parasite infections were found to have greater impacts on FCS and BCS than single infections. A higher number of internal parasites detected per lamb was associated with lower BCS and more loose faeces. The relationship between parasite detection and live weight or growth rate were inconsistent for both flocks. Adjusted WEC was correlated with FCS and faecal DM% for one flock only, although little or no correlation was found with live weight and growth rate for both flocks. Cryptosporidium ubiquitum and Cryptosporidium parvum were the most prevalent Cryptosporidium species isolated in the two flocks. Giardia assemblage E was the most commonly isolated genotype assemblage from both flocks, while assemblage A was isolated almost as frequently as assemblage E in the one flock. One flock was a potential source of zoonotic Cryptosporidium and the other flock was a potential source of zoonotic Giardia.

Molecular evidence for zoonotic transmission of Giardia duodenalis among dairy farm workers in West Bengal, India

No study in the past has examined the genetic diversity and zoonotic potential of Giardia duodenalis in dairy cattle in India. To assess the importance of these animals as a source of human G. duodenalis infections and determine the epidemiology of bovine giardiasis in India, fecal samples from 180 calves, heifers and adults and 51 dairy farm workers on two dairy farms in West Bengal, India were genotyped by PCR-RFLP analysis of the β-giardin gene of G. duodenalis followed by DNA sequencing of the nested PCR products. The overall prevalence of G. duodenalis in cattle was 12.2% (22/180), the infection being more prevalent in younger calves than in adult cattle. Zoonotic G. duodenalis Assemblage A1 was identified in both calves and workers although the most prevalent genotype detected in cattle was a novel Assemblage E subgenotype. These findings clearly suggest that there is a potential risk of zoonotic transmission of G. duodenalis infections between cattle and humans on dairy farms in India.

The efficacy of a treatment with fenbendazole against an experimental Giardia duodenalis infection in lambs

The aim of the present study was to evaluate the efficacy of fenbendazole (Panacur 2.5%; Intervet/Schering-Plough) at 15mg/kg/day during 3 consecutive days in lambs experimentally infected with Giardia duodenalis, and to evaluate the benefit of the treatment with fenbendazole on growth, faecal consistency and general health. To this end, 42 weaned (∼12 weeks of age) and healthy lambs were selected and housed into three experimental groups based on weight. One group of 14 lambs remained uninfected (group 1: negative control group), while the other 28 lambs were infected with a total of 105G. duodenalis cysts, 11 days prior to treatment (D11). Based on the average individual cyst counts between D4 and D2, the infected animals were allocated on D1 into two groups of 14 animals each. Treatment was randomly assigned to one of these two groups, and all animals in the treatment group (group 3) were orally treated with fenbendazole at 15mg/kg/day during 3 consecutive days starting from D0 (day of treatment). The lambs in the positive (group 2) and negative control group received a placebo (water). From 3 days after treatment (D3) onwards, cyst excretion was determined three times a week during 4 consecutive weeks after the start of the treatment. The faecal consistency and general health were recorded at each sampling day. The weight was recorded prior to treatment and at the end of each week throughout the experimental period. During the experimental period, there was a high (≥97.8%) and continuous reduction in cyst excretion in the treatment group compared to the positive control group for 12 days, resulting in a significant (P<0.001) reduction of the cumulative cyst excretion until D21. There were no significant differences in general health and faecal consistency between the three groups, as there were no overt clinical symptoms in any of the infected animals. Prior to treatment the weight did not differ between the three groups. Although not significantly different, the animals in the treatment group gained on average 4.23kg over the 4-week period, while the infected and non-infected animals gained 3.78kg and 3.52kg, respectively.

Co-infection with Ascaris lumbricoides modulates protective immune responses against Giardia duodenalis in school Venezuelan rural children

We evaluated the effect of Ascaris lumbricoides on Giardia duodenalis infection and TH1/TH2 type immune mechanisms toward this parasite in 251 rural parasitized and 70 urban non-parasitized school children. The children were classified according to light (0–5000eggs/gfaeces) or moderate (>5001–50,000eggs/gfaeces) A. lumbricoides infection. Anti G. duodenalis skin hyper-reactivity, IgE, IgG, IL-13, IFN γ, IL6 and IL-10 levels were compared among G. duodenalis infected and non-infected children according to light or moderate A. lumbricoides infection. It was found that 62% of the A. lumbricoides moderately infected children were co-infected by G. duodenalis compared to 45% of the lightly infected group. After treatment, 42% of the A. lumbricoides moderately group were infected with G. duodenalis compared to 11% of their lightly counterparts, being A. lumbricoides IL-10 levels higher (p<0.0001) in the moderately infected group. In the A. lumbricoides lightly parasitized children, G. duodenalis infection was associated to a significant increase (p<0.005) of the levels of G. duodenalis IL-13, IFN-γ, IL-6, IgE, IgG and skin test hyper reactivity. In contrast, there was no effect of G. duodenalis infection in the elevation of these parameters among the A. lumbricoides moderately parasitized group, being those levels similarly lower as those observed in the control group. Inverse correlations were found between the levels of anti G duodenalis antibodies, skin test hyper-reactivity and cytokines with the intensity of A. lumbricoides infection (p>0.0001) and A. lumbricoides IL-10 levels (p>0.0001), suggesting that co-infection with A. lumbricoides may affect both TH1 and TH2 type immunity against G. duodenalis that may play an important role in the susceptibility to the infection after chemotherapy in children from endemic areas.

Impact of a citywide sanitation program in Northeast Brazil on intestinal parasites infection in young children.

BackgroundSanitation affects health, especially that of young children. Residents of Salvador, in Northeast Brazil, have had a high prevalence of intestinal parasites. A citywide sanitation intervention started in 1996 aimed to raise the level of sewer coverage from 26% to 80% of households.ObjectivesWe evaluated the impact of this intervention on the prevalence of Ascaris lumbricoides, Trichuris trichuria, and Giardia duodenalis infections in preschool children.MethodsThe evaluation was composed of two cross-sectional studies (1998 and 2003–2004), each of a sample of 681 and 976 children 1–4 years of age, respectively. Children were sampled from 24 sentinel areas chosen to represent the range of environmental conditions in the study site. Data were collected using an individual/household questionnaire, and an environmental survey was conducted in each area before and after the intervention to assess basic household and neighborhood sanitation conditions. Stool samples were examined for the presence of intestinal parasites. The effect of the intervention was estimated by hierarchical modeling, fitting a sequence of multivariate regression models.FindingsThe prevalence of A. lumbricoides infection was reduced from 24.4% to 12.0%, T. trichuria from 18.0% to 5.0%, and G. duodenalis from 14.1% to 5.3%. Most of this reduction appeared to be explained by the increased coverage in each neighborhood by the sewage system constructed during the intervention. The key explanatory variable was thus an ecological measure of exposure and not household-based, suggesting that the parasite transmission prevented by the program was mainly in the public (vs. the domestic) domain.ConclusionThis study, using advanced statistical modeling to control for individual and ecological potential confounders, demonstrates the impact on intestinal parasites of sanitation improvements implemented at the scale of a large population.

Prevalence, molecular typing and risk factor analysis for Giardia duodenalis infections in dogs in a central London rescue shelter

A cross-sectional survey to investigate canine infections with Giardia duodenalis was undertaken at a central London rescue shelter between October 2006 and March 2007. The objectives of the study were to (i) estimate the prevalence of infection in dogs admitted to a London dog shelter using a commercially available ELISA-based test kit; (ii) identify the relative importance of potential dog level risk factors for infection; and (iii) identify the occurrence of different G. duodenalis assemblages present in this population in order to identify presence of any potentially zoonotic assemblages. A faecal sample was collected from each dog entering the shelter within 1 day of arrival. Each sample was tested for the presence of parasite cyst wall protein using the Giardia SNAP test kit (Idexx Laboratories). Samples were graded for faecal consistency on a standard scale and data on age, breed, categorized breed group, sex and neutered status were collected for each dog. Associations between infection status and each dog level variable were investigated using univariable and multivariable logistic regression. Selected G. duodenalis-positive samples were genotyped using previously described primers targeting the 18S rDNA gene and the β-giardin gene. Samples from a total of 878 dogs were collected and the true prevalence found to be 21.0% (95% CI 16.7–25.4%). In the present study, the odds of infection decreased with increasing age (adjusted odds ratio 0.66, 95% CI 0.54–0.80, p < 0.0001) and was increased for Rottweilers (adjusted odds ratio 2.12, 95% CI 1.03–4.34, p = 0.04). Of the 51 samples selected for genotyping, 41 samples yielded a good amplification at one or both of the targeted genes, demonstrating the occurrence of mainly dog-specific assemblages C and D. The potentially zoonotic assemblage A and a mixed template C/D were found in two individual dogs. The results of the present study illustrate the high prevalence of G. duodenalis in shelter dogs. Although predominantly infected with dog-specific assemblages, the identification of assemblage A suggests that appropriate precautions should be taken to minimize the risk of transmission to staff.

Molecular Epidemiology of Cross-Species Giardia duodenalis Transmission in Western Uganda

Background Giardia duodenalis is prevalent in tropical settings where diverse opportunities exist for transmission between people and animals. We conducted a cross-sectional study of G. duodenalis in people, livestock, and wild primates near Kibale National Park, Uganda, where human-livestock-wildlife interaction is high due to habitat disturbance. Our goal was to infer the cross-species transmission potential of G. duodenalis using molecular methods and to investigate clinical consequences of infection.Methodology/Principal FindingsReal-time PCR on DNA extracted from fecal samples revealed a combined prevalence of G. duodenalis in people from three villages of 44/108 (40.7%), with prevalence reaching 67.5% in one village. Prevalence rates in livestock and primates were 12.4% and 11.1%, respectively. Age was associated with G. duodenalis infection in people (higher prevalence in individuals ≤15 years) and livestock (higher prevalence in subadult versus adult animals), but other potential risk factors in people (gender, contact with domestic animals, working in fields, working in forests, source of drinking water, and medication use) were not. G. duodenalis infection was not associated with gastrointestinal symptoms in people, nor was clinical disease noted in livestock or primates. Sequence analysis of four G. duodenalis genes identified assemblage AII in humans, assemblage BIV in humans and endangered red colobus monkeys, and assemblage E in livestock and red colobus, representing the first documentation of assemblage E in a non-human primate. In addition, genetic relationships within the BIV assemblage revealed sub-clades of identical G. duodenalis sequences from humans and red colobus.Conclusions/SignificanceOur finding of G. duodenalis in people and primates (assemblage BIV) and livestock and primates (assemblage E) underscores that cross-species transmission of multiple G. duodenalis assemblages may occur in locations such as western Uganda where people, livestock, and primates overlap in their use of habitat. Our data also demonstrate a high but locally variable prevalence of G. duodenalis in people from western Uganda, but little evidence of associated clinical disease. Reverse zoonotic G. duodenalis transmission may be particularly frequent in tropical settings where anthropogenic habitat disturbance forces people and livestock to interact at high rates with wildlife, and this could have negative consequences for wildlife conservation.

Intestinal Protozoan Infections in Relation to Nutritional Status and Gastrointestinal Morbidity in Colombian School Children

While Giardia duodenalis infection has been consistently associated with nutrient malabsorption and stunting in children, the effects of other protozoans on nutritional status or gastrointestinal morbidity are less clear. We sought to determine whether infection with common intestinal protozoans including Giardia duodenalis, Entamoeba coli and Blastocystis hominis was associated with anthropometric and micronutrient status, gastrointestinal symptoms, visits to the doctor or school absenteeism in children 5-12 years of age from Bogotá, Colombia. We obtained stool samples from 442 children enrolled in primary schools in 2006 and examined the presence of intestinal protozoans in relation to height, body mass index, plasma concentrations of vitamins A and B12, ferritin and zinc and erythrocyte folate. In addition, we examined the associations between protozoan infections and the incidence of common gastrointestinal symptoms, which were registered prospectively in morbidity diaries. The prevalence rates of G. duodenalis, E. coli and B. hominis infection were 6.3, 23.1 and 22.4%, respectively. Giardia infection was associated with lower height-for-age z-score (p = 0.04), whereas E. coli infection was associated with low erythrocyte folate (p = 0.04), and B. hominis infection was related to higher vitamin A levels (p = 0.05). Infection with E. coli was also associated with a significantly higher incidence of fever but fewer visits to the doctor, while B. hominis infection was associated with significantly less diarrhea, diarrhea with vomiting, doctor visits and school absenteeism. In conclusion, G. duodenalis and E. coli infections were associated with indicators of poor nutritional status in this population, while B. hominis was related to apparently decreased morbidity.

Giardiasis – why do the symptoms sometimes never stop?

Although giardiasis is considered by most medical practitioners to be an easily treated infection, prolonged symptoms due to, or following, Giardia duodenalis infection can have a significant impact on quality of life. Symptom recurrence, including abdominal symptoms and fatigue, can result from re-infection, treatment failure, disturbances in the gut mucosa or post-infection syndromes. In developed countries, these sequelae can have an enormous impact on quality of life; in developing countries, particularly in children, they add yet another burden to populations that are already disadvantaged. Here, we outline current knowledge, based on individual case sequelae from sporadic infections, observations of population effects following outbreaks and studies of phenotypic and genotypic diversity between morphologically identical isolates of parasites. We also raise further questions, looking for clues as to why giardiasis sometimes becomes an intrusive, long-term problem.

Giardia duodenalis infection and anthropometric status in preschoolers in Salvador, Bahia State, Brazil

The aim of this study was to estimate the association between Giardia duodenalis infection and anthropometric deficits, as measured by weight-for-age and height-for-age. This cross-sectional study included 629 children from 12 to 48 months of age, selected from 30 geographic areas in the city of Salvador, Bahia State, Brazil. Poisson regression and linear regression were used for the multivariate statistical analyses. G. duodenalis was diagnosed in 13.5% of the children. The children's breastfeeding duration and living conditions (garbage collection and paved streets or sidewalks) modified the effect of G. duodenalis infection on anthropometric status. Among infected children, there were statistically significant associations between weight deficit and shorter breastfeeding (PR=2.22; 95%CI: 1.56-3.14) and inadequate paving of streets and sidewalks (PR=2.00; 95%CI: 1.37-2.92), while height deficit was associated with deficient public garbage collection (PR=2.21; 95%CI: 1.31-2.51). In the linear regression, the association with the anthropometric indicators remained positive and statistically significant. The child's unhealthy living environment aggravated the negative effect of G. duodenalis infection on anthropometric status, and breastfeeding was a protective factor in the outcome.

Prevalence and molecular characterization of Giardia duodenalis and Cryptosporidium spp. in dairy cattle in Ontario, Canada

Giardia duodenalis and Cryptosporidium spp. are intestinal protozoan parasites that infect a wide range of host species, including humans. Molecular characterization of these parasites has demonstrated that a number of genotypes and species are common to both humans and animals, and that zoonotic transmission may occur. Numerous studies have reported a high prevalence of G. duodenalis and Cryptosporidium spp. in cattle, particularly calves, and these animals are frequently associated with zoonotic transmission. In the present study, a total of 143 faecal samples from adults, heifers and calves were collected from two dairy cattle farms in eastern Ontario, Canada. The prevalence and molecular characteristics of G. duodenalis and Cryptosporidium spp. in these animals were determined in order to investigate the potential for transmission between cattle and humans in this region. Following DNA extractions from faecal samples, nested-PCR protocols were used to amplify fragments of the 16S rRNA gene and the heat-shock protein 70 (HSP-70) gene for determining the prevalence of G. duodenalis and Cryptosporidium spp. infections, respectively. Genotypes of G. duodenalis, and species of Cryptosporidium, were determined by means of DNA sequencing of amplicons, and subsequent sequence alignment. Cattle on both farms showed a high prevalence of G. duodenalis (42.0%) and Cryptosporidium spp. (27.3%). G. duodenalis infections were more prevalent in calves and heifers than in adults, and Cryptosporidium spp. infections were only observed in calves and heifers. The zoonotic genotype, G. duodenalis Assemblage B was isolated from 24.5% of the cattle tested, while G. duodenalis Assemblage E was found in 17.5% of the cattle tested. The overall prevalence of the zoonotic species Cryptosporidium parvum in the animals tested was found to be 21.7%, while only 1.4% were infected with C. bovis. These findings suggest that there is a potential risk of zoonotic and/or zooanthroponotic transmission of G. duodenalis and C. parvum infections between cattle and humans in eastern Ontario, likely by means of contaminated water or food, or through direct faecal-oral transmission in the case of farmers and veterinary staff.

Persisting symptoms and duodenal inflammation related to Giardia duodenalis infection

After a large waterborne outbreak of Giardia infection in Bergen, some patients experienced persisting abdominal symptoms despite metronidazole treatment. This study aimed at investigating possible causes for their symptoms. Over a 15 month period, 124 referred patients were evaluated in a prospective cohort analysis with a standardised investigation including duodenal biopsies and aspirate, blood tests and faecal parasite and calprotectin tests. Recovered subjects were recruited for symptom analysis. Persisting Giardia duodenalis infection was found in 40 patients (32.3%). Duodenal biopsies showed signs of inflammation in 57 patients (47.1%). Microscopic duodenal inflammation was present in 34 (87.2%) of the Giardia positive and 23 (28.0%) of the Giardia negative patients. There were significant associations between persistent Giardia positivity, microscopic duodenal inflammation and a positive calprotectin test. Duodenal aspirate and duodenal biopsies performed poorly in diagnosis of persistent giardiasis. In patients with persisting symptoms after metronidazole treated Giardia infection we commonly found chronic Giardia infection and microscopic duodenal inflammation, especially in illness duration less than 7 months. Both these findings subsided over time. Increasingly, investigations could not determine a definite cause for the persistent symptoms. The very long-term post-giardiasis diarrhoea, bloating, nausea and abdominal pain documented here need further study.

Correlation between the presence of symptoms and the Giardia duodenalis genotype

Clinical manifestations of Giardia duodenalis infection vary from asymptomatic infection to chronic diarrhoea. We study the correlation between the presence of symptoms and the G. duodenalis genotype in 108 patients with giardiasis. Patient age ranged from 2 to 72 years old. We found a correlation between assemblage AII and symptomatic infections, and between assemblage B and asymptomatic infections in the overall patient group and in patients less than five years of age. Nevertheless, if only patients of more than five years of age were considered, no statistically significant relationship between assemblage and symptomatic or asymptomatic Giardia infections was found. In these patients, host factors may affect the presence of clinical manifestations more than Giardia assemblage.

GIARDIA DUODENALIS CYSTS ISOLATED FROM WILD MOOSE AND REINDEER IN NORWAY: GENETIC CHARACTERIZATION BY PCR-RFLP AND SEQUENCE ANALYSIS AT TWO GENES

There are few genotyping studies of Giardia duodenalis isolates from cervid hosts, although a previous study suggested that cervids may be a source of infection for humans and cattle. Giardia duodenalis isolates collected from wild moose (Alces alces) and reindeer (Rangifer tarandus) in Norway during 2002 and 2003 were characterized by polymerase chain reaction-restriction fraction length polymorphism (PCR-RFLP) at the beta-giardin gene, and sequence analysis at both the beta-giardin and glutamate dehydrogenase (gdh) genes. All results suggested that these isolates (n=25) belonged to assemblage A. Three different restriction patterns were obtained with PCR-RFLP, one of which has previously been associated with assemblage A. At the beta-giardin gene, sequences from six reindeer isolates and one moose isolate were identical to a previously published assemblage A sequence from G. duodenalis cysts isolated from dairy calves. The other 10 moose isolates could be divided into five groups, with between two and 14 single nucleotide polymorphisms (SNPs) from the published genotype A2. At the gdh gene, three different sequences were obtained, differing from each other by between one and 15 SNPs and which have all been previously published as genotype A1, but with different specific hosts. Grouping of the isolates based on the sequences from both genes gave complex results; whereas all the G. duodenalis isolates from reindeer grouped together, two moose isolates, which had identical sequences at the beta-giardin gene, had sequences that differed from each other by 15 SNPs at the gdh gene. The results of these studies, together with the large Norwegian populations of these cervids and the amount of fecal matter they produce, indicate that moose and reindeer may be significant reservoirs of G. duodenalis infection in Norway, which may be of importance to veterinary and public health.

Tendencia de la prevalencia y factores asociados a la infección por Giardia duodenalis en escolares y preescolares de una zona rural de Cundinamarca

Giardia doudenalis infection remains an important public health problem worldwide, as well as in Colombia. This infection is associated with poverty and lack of public services. The study was designed to describe prevalence trends of Giardia duodenalis infections in preschool and school-age children from the village of La Virgen, Quipile, Cundinamarca, and its possible association with socioeconomic variables. Three cross-sectional studies were undertaken in 1995, 2001 and 2005. In each, a non-random sample was selected among children aged <1 to 15 years. Fecal samples were collected for direct examination in order to determine G. duodenalis infection and other intestinal parasites. During the 2005 survey information was collected concerning the sociodemographic and economic conditions in each family group from which a child was sampled. The prevalence of G. duodenalis infection did not change significantly during the study period-13.6% in 1995, 12.8% in 2001 and 15.2% in 2005. These results suggested that belonging to the subsidized health care regime was associated with G. duodenalis infection (prevalence rate [PR]: 4.47; 95% confidence interval [95% CI] 0.6-32.0), not having water supply (PR 2.6; 95% CI 1.1-6.0) and involvement in agricultural activities (PR 2.5; 95% CI 1.0-6.4). Giardiasis is a continuing public health problem at La Virgen. As long as the environmental and socioeconomic factors associated with infection persist, this intestinal protozoan infection will not be controlled.

Prevalence of Giardia duodenalis genotypes in adult dairy cows

The prevalence of Giardia duodenalis genotypes was determined in adult dairy cows. Fecal specimens were collected from two farms each in Vermont, New York, Pennsylvania, Maryland, Virginia, North Carolina, and Florida. Specimens, cleaned of fecal debris and concentrated using CsCl density gradient centrifugation, were subjected to PCR and DNA sequence analysis. The prevalence of G. duodenalis infection, ranged from 3% to 64%, with an average prevalence of 27% (144 positive cows out of 541 examined). DNA sequence analysis of the 16S rRNA gene revealed the presence of both Assemblage A and Assemblage E, G. duodenalis. Overall, Assemblage E was present in 25% of all animals tested and Assemblage A was present in 2% of the animals. As a percentage of G. duodenalis isolates, Assemblage E represented 94% and Assemblage A represented 6%. Although, most of the cows were infected with a genotype that is not known to be infectious for humans, adult cows on five farms did harbor varying levels of zoonotic Assemblage A, G. duodenalis. Therefore, although adult cows do not appear to be a significant source of human infectious cysts in the environment, the risk from this age group should not entirely be discounted.

Giardia duodenalis infection: risk factors for children living in sub-standard settlements in Brazil

The objective of the present study was to characterize Giardia duodenalis infection among children living in sub-standard settlement areas in the municipality of Juiz de Fora, Minas Gerais State, Brazil. The cross-sectional epidemiological study included 590 children from 1 to 5 years of age. Data were collected from one child per selected family through home interviews with the parent or guardian and parasitological examination of stool samples. Thirty-one putative risk factors concerning family structure, socioeconomic status, and environmental factors were analyzed by multivariate logistic regression. Prevalence of G. duodenalis infection was 18% (106 children). Four potential risk factors were heavily associated with G. duodenalis infection: number of under-five children in the same household, index child's birth order, existence of a bathroom in the home, and drinking water source.

Efficacy of vaccination in preventing giardiasis in calves

The objective of this study was to evaluate the efficacy of a vaccine in the prevention of Giardia duodenalis infection in calves. Six 2-week old calves were vaccinated subcutaneously with a sonicated G. duodenalis trophozoite vaccine. Six 2-week old control calves received a subcutaneous injection of sterile phosphate-buffered-saline mixed with adjuvant. Injections were repeated after 28 days. Eleven days after the second injection, calves were challenged orally with 1 × 10 5 purified G. duodenalis cysts from a naturally infected calf. Throughout the study, fecal samples were collected at regular intervals and examined for the presence of G. duodenalis cysts. Blood samples were collected weekly until G. duodenalis challenge and bi-weekly following challenge. Calves were euthanized 14 days after challenge and G. duodenalis trophozoites within the small intestines were enumerated. Serum antibody titers were significantly higher in vaccinated compared to non-vaccinated calves. Vaccinated calves tended to excrete more G. duodenalis cysts in their feces than non-vaccinated calves. The number of trophozoites in the small intestine was not different between vaccinated and non-vaccinated calves. Changes consistent of moderate enteritis were found in the intestines of one vaccinated and one non-vaccinated calf. Despite a serological immune response following vaccination, this vaccine was not efficacious in preventing giardiasis or reducing cyst shedding in calves.

Genotyping of Giardia duodenalis from human and animal samples from Brazil using β-giardin gene: A phylogenetic analysis

Giardia duodenalis is one of the major diarrhea agents in human and animals distributed worldwide, and present high levels of genetic diversity, showing seven genotypes: A, B, C, D, E, F, and G. Only Assemblages A and B have been detected in humans and in a wide range of other mammalians hosts, whereas the remaining Assemblages (C–G) are host-specific. Molecular characterization of cysts of human and animal origin are useful to address the co-circulate isolates between these host, and represents an objective means to evaluate zoonotic infection hypothesis. In the present work the G. duodenalis genotypes were characterized by restriction fragment length polymorphisms and DNA sequencing analysis of PCR products of the β-giardin gene. The cysts were collected in the city of Rio de Janeiro, in Brazil, from a population composed by humans ( n = 366, 310 children and 56 adults), domestic animals ( n = 11) from a municipal daycare center in the surroundings of a slum and neighborhood medium–high class domestic animals ( n = 18). Parasitological exams were developed in human fecal samples. Parasites were found in 60% (186/310) and 66% (37/56) of the samples from children and adults, respectively. Among children's samples, 27.7% (86/310) were positive for G. duodenalis. Only 1.7% (1/56) of the adults was positive for this parasite. In general a total of 87 fecal samples (86 from children and 1 from adult) from all population studied were positive for G. duodenalis, and 62 of these were subjected to molecular analysis using a PCR that amplified a fragment of the β-giardin gene. Sixty samples were typed as genotype A1, two as genotype A2 and genotype B was not encountered. Among domestic animals samples ( n = 29), eight (seven dogs and one cat) from the slum community were identified as genotype A1, and all control samples ( n = 18) were negative in the molecular assay. The host-specific genotypes C, D and, F were not found. In this study we described single case of G. duodenalis infection associated with a child and her dog and both isolates characterized as genotype A1. Despite the low incidence, this data suggest the putative existence of a zoonotic cycle of G. duodenalis in the studied population.