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PubMed1993

Waterborne Giardia cysts and Cryptosporidium oocysts in the Yukon, Canada.

Several outbreaks of waterborne giardiasis have occurred in southern Canada, but nothing has been reported from the Canadian North. The objective of this study was to collect information relevant to waterborne giardiasis and cryptosporidiosis in the Yukon including epidemiological data and analyses of water, sewage, and animal fecal samples. Remote, pristine water samples were found to be contaminated with Giardia cysts (7 of 22 or 32%) but not with Cryptosporidium oocysts. Giardia cysts were found in 21% (13 of 61) of animal scats, but no Cryptosporidium oocysts were observed (small sample size). Whitehorse's drinking water was episodically contaminated with Giardia cysts (7 of 42 or 17%) and Cryptosporidium oocysts (2 of 42 or 5%). Neither were found in Dawson City's water supply. The only water treatment in the Yukon is chlorination, but contact times and free chlorine residuals are often too low to provide adequate protection by disinfection. Raw sewage samples from the five largest population centers in the Yukon contained 26 to 3,022 Giardia cysts and 0 to 74 Cryptosporidium oocysts per liter. Treated sewage from Whitehorse contained fewer Giardia cysts but more Cryptosporidium oocysts on average. Both were detected in Lake Laberge, downstream of Whitehorse, which has a history of fecal coliform contamination. Daily monitoring of raw sewage from the suburbs of Whitehorse showed a summertime peak of Giardia cysts and occasional Cryptosporidium oocysts after springtime contamination of drinking water. Despite this evidence, epidemiological data for the Yukon showed an endemic infection rate of only 0.1% for giardiasis (cryptosporidiosis is not notifiable).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1996

Evaluation of PCR, nested PCR, and fluorescent antibodies for detection of Giardia and Cryptosporidium species in wastewater.

Giardiasis and cryptosporidiosis are diseases caused by the protozoan parasites Giardia lamblia and Cryptosporidium parvum. Waterborne transmission of these organisms has become more prevalent in recent years, and regulatory agencies are urging that source and finished water be screened for these organisms. A major problem associated with testing for these organisms is the lack of reliable methodologies and baseline information on the prevalence of these parasites in various water sources. Our study addressed both of these issues. We evaluated the presence and reduction of Giardia cysts and Cryptosporidium oocysts in sewage effluent by a combination of indirect fluorescent antibody (IFA) staining and PCR. Our results indicated a 3-log reduction of Giardia cysts and a 2-log reduction of Cryptosporidium oocysts through the sewage treatment process as determined by IFA. We developed a nested PCR to detect Cryptosporidium oocysts and used a double PCR to detect Giardia cysts. A 100% correlation was noted between IFA and PCR detection of Giardia cysts while correlation for Cryptosporidium oocysts was slightly less. On the basis of these results, PCR may be a useful tool in the environmental analysis of water samples for Giardia and Cryptosporidium organisms.

Animals↗

PubMed1996

Studies of Giardia spp. and Cryptosporidium spp. in two adjacent watersheds.

Two adjacent British Columbia, Canada, watersheds with similar topographical features were studied. Both the Black Mountain Irrigation District (BMID) and the Vernon Irrigation District (VID) serve rural agricultural communities which are active in cattle ranching. The present study was carried out in five phases, during which a total of 249 surface water samples were tested in the study watersheds. The aims of these phases were to determine levels of parasite contamination in raw water samples collected from the intakes as well as from other sites in each watershed and to investigate cattle in the watersheds as potential sources of parasite contamination of surface drinking water supplies. Giardia cysts were not detected in the raw water samples collected from lake sources at the headwaters of both watersheds but were found in 100% (70 or 70) of water samples collected at the BMID intake and 97% (68 of 70) of water samples collected at the VID intake. Significantly higher levels (P < 0.05) of Giardia cysts were found at the BMID intake (phase 1, 7 to 2,215 cysts per 100 liters; phase 3, 4.6 to 1,880 cysts per 100 liters) when compared with that of the VID intake (2 to 114 cysts per 100 liters). The BMID watershed has a more complex system of surface water sources than the VID watershed. Cattle have access to creeks in the BMID watershed, whereas access is restricted in the VID watershed. Collection of raw water samples from a creek upstream and downstream of a cattle ranch in the BMID watershed showed that the downstream location had significantly higher (P < 0.05) levels (0.6 to 42.9 cysts per 100 liters and 1.4 to 300.0 oocysts per 100 liters) of both Giardia cysts and Cryptosporidium oocysts than those of the upstream location (0.5 to 34.4 cysts per 100 liters and 0.5 to 34.4 oocysts per 100 liters). Peak concentrations of both parasites coincided with calving activity. Fecal samples, collected from cattle in both watersheds, showed 10% (3 of 30) in the BMID and 50% (5 of 10) in the VID watersheds to be Giardia positive. No Cryptosporidium-positive fecal samples were found. Giardia cysts isolated from the BMID watershed were repeatedly infective to gerbils in contrast to those from the VID watershed. The 10 BMID drinking water Giardia isolates retrieved into culture and biotyped showed zymodeme and karyotype heterogeneity. The differences in patterns of parasite contamination and cattle management practices contribute to the unique watershed characteristics observed between two areas which are topographically similar and geographically adjacent.

Animals↗

PubMed2003

Evaluation of three commercial assays for detection of Giardia and Cryptosporidium organisms in fecal specimens.

There is an increasing demand for diagnostic testing for Giardia intestinalis (G. lamblia) and Cryptosporidium parvum, with a priority being placed on obtaining diagnostic results in an efficient and timely manner. Several commercial companies have developed rapid diagnostic tests that are simple to perform and can be completed in less time than traditional methods for detecting Giardia and Cryptosporidium: We compared one of these rapid tests, the ImmunoCard STAT! (Meridian Bioscience, Inc.) lateral-flow immunoassay, with the MERIFLUOR direct fluorescent-antibody (DFA) test, the ProSpecT EZ microplate assay for Giardia and the ProSpecT microplate assay for Cryptosporidium, and modified Kinyoun's acid-fast stained smears for the detection of Cryptosporidium using 246 specimens. The MERIFLUOR DFA (Meridian Bioscience, Inc.) test detected the largest number of cases (32 Giardia and 37 Cryptosporidium) infections and was used to calculate the sensitivity and specificity of the other tests. For Giardia, the sensitivities of the ImmunoCard STAT! and the ProSpecT Giardia EZ microplate assay (Alexon-Trend, Inc.) were 81 and 91%, respectively. For detection of Cryptosporidium, the sensitivities of the ImmunoCard STAT!, the ProSpecT Cryptosporidium microplate assay (Alexon-Trend, Inc.), and modified Kinyoun's acid-fast stained smears were 68, 70, and 78%, respectively. Test specificities were equal to or greater than 99%. Specimens with very small numbers of organisms were not detected by the ImmunoCard STAT!, the ProSpecT microplate assay or modified Kinyoun's acid-fast stained smears.

Animals↗

PubMed1988

Attachment of Giardia lamblia to rat intestinal epithelial cells.

The human enteric protozoan, Giardia lamblia, has surface membrane lectin activity which mediates parasite adherence to erythrocytes. To determine whether an intestinal binding site exists for this lectin we have studied the interaction in vitro between axenically cultured Giardia trophozoites and isolated rat intestinal epithelial cells. Scanning electron microscopy showed that Giardia attached to the apical microvillus membrane and basolateral membrane of rat enterocytes. Any location on the parasite surface could mediate attachment without predeliction for the ventral disc. Trophozoites attached more avidly to jejunal compared with colonic epithelial cells. Attachment was inhibited at 4 degrees C, by sugars and glycoproteins containing D-mannosyl residues and by subagglutinating concentrations of anti-Giardia rabbit serum and two monoclonal antibodies, all with reactivity to parasite surface membrane determinants. Trypsinisation of trophozoites also reduced attachment but the ability to attach was rapidly restored after returning trophozoites to TYI-S culture medium for 4 h at 37 degrees C. Attachment was unaltered by the presence of the microfilament inhibitor cytochalasin B and in the absence of Ca++ and Mg++ ions. These findings support previous work that Giardia possesses a surface membrane mannose binding lectin and indicate that appropriate binding sites are present on rat intestinal epithelial cells. This lectin may play a part in mediating adherence of Giardia to mammalian intestine and could be a target for host immune defence.

Animals↗

PubMed2000

Genotyping of Giardia lamblia isolates from humans in China and Korea using ribosomal DNA Sequences.

Genetic characterization of a total of 15 Giardia lamblia isolates, 8 from Anhui Province, China (all from purified cysts) and 7 from Seoul, Korea (2 from axenic cultures and 5 from purified cysts), was performed by polymerase chain reaction amplification and sequencing of a 295-bp region near the 5' end of the small subunit ribosomal DNA (eukaryotic 16S rDNA). Phylogenetic analyses were subsequently conducted using sequence data obtained in this study, as well as sequences published from other Giardia isolates. The maximum parsimony method revealed that G. lamblia isolates from humans in China and Korea are divided into 2 major lineages, assemblages A and B. All 7 Korean isolates were grouped into assemblage A, whereas 4 Chinese isolates were grouped into assemblage A and 4 into assemblage B. Two Giardia microti isolates and 2 dog-derived Giardia isolates also grouped into assemblage B, whereas Giardia ardeae and Giardia muris were unique.

Animals↗

PubMed1989

Detection of giardia antigen in stool samples by a semi-quantitative enzyme immunoassay (EIA) test.

A semi-quantitative enzyme immunoassay (EIA) test for the detection of Giardia intestinalis antigen in faeces was developed. In order to avoid unspecific reactions due to anticalf serum activity, IgG fractions of anti-giardia rabbit and sheep sera were purified from antibovine antibodies by immunoadsorption. Faecal specimens tested in the assay were mixed with normal horse serum to avoid unspecific and proteolytic effects of stool components. Out of a range of bacterial and parasitic antigens tested, only high concentrations of Ascaris suum egg antigen and Shigella sonnei gave slight unspecific reactions. During an outbreak of waterborne giardia infection faecal samples from 49 individuals were tested. Giardia cysts were found by microscopy in 22 individuals and specimens from 24 persons were positive by EIA. The estimated amount of antigen found in the positive samples ranged from 50 to 5,000 ng giardia protein/ml. After filtration through a 0.45 microns filter antigenic activity was found in the filtrate of 10 samples. In 3/6 samples with no cysts detected by microscopy, mainly soluble giardia antigen was found.

Adolescent↗

PubMed2003

[Are domestic Cryptosporidium and Giardia infections in Norway underdiagnosed?].

BACKGROUND: Cryptosporidium and Giardia are recognised as common causes of waterborne disease in several countries. In order to describe investigative practices for these protozoan parasites in Norway, we surveyed medical microbiology laboratories nationwide for faecal screening policies and methods used for detection of Cryptosporidium and Giardia. MATERIAL AND METHODS: All medical microbiology laboratories in Norway received questionnaires on laboratory methods, indications for screening, and numbers of samples investigated over the 1998-2002 period. RESULTS: Of the 22 laboratories that receive faecal samples, 17 had established diagnostic routines for Giardia detection, 14 for Cryptosporidium. Examination for Giardia cysts was standard procedure in all 17 laboratories, mainly in specimens from immigrants and travellers returning from abroad. Examination for Cryptosporidium was, on the other hand, infrequent. Ten of the 14 laboratories reported less than 10 examinations per year. Giardia was frequently detected, with 1 to 6% positive samples in the various laboratories. Cryptosporidium was seldom detected; all laboratories reported only 0-1 positive sample per year. INTERPRETATION: While laboratories frequently screen faecal samples for Giardia, screening for Cryptosporidium is rare. Little is known about the public health significance of domestic infections with these parasites in Norway; further investigation is needed in order to estimate the burden of disease they cause and to implement control measures if required.

Animals↗

PubMed2004

Potential diagnosis of Giardia lamblia infection through specific antibody detection in saliva.

Thirty six patients presenting with gastrointestinal symptoms were studied for the presence of specific anti-Giardia lamblia salivary IgA antibodies. Stool samples were examined for parasites especially G. lamblia by direct smear. Duodenal aspirate was examined for the parasite. Saliva samples were collected from each patient and examined by ELISA technique for the specific anti-Giardia lamblia IgA antibodies. 94.4% of positive cases for G. laimblia by stool analysis had positive anti-Giardia salivary IgA antibodies. 33.3% of stool negative cases were positive for anti-Giardia salivary IgA antibodies. All Giardia negative cases by duodenal aspirate examination were negative for anti-Giardia salivary IgA antibodies. Detection of antiGiardia salivary IgA antibodies was an excellent tool for screening G. lamblia in patients with long standing symptoms of more than one month duration.

Animals↗

PubMed1992

Isolation and characterization of a NADP-dependent glutamate dehydrogenase gene from the primitive eucaryote Giardia lamblia.

Giardia lamblia is believed to be the earliest branching derivative from the eucaryotic lineage. Genomic and cDNA clones encoding the giardia NADP-dependent glutamate dehydrogenase have been isolated and characterized. Southern hydridization using genomic DNA indicates that the gene encoding this activity is unique and single copy. Primer extension, S1 nuclease protection, and genomic and cDNA sequence analysis demonstrate that gene transcripts are initiated within a conserved AT-rich sequence element immediately preceding the ATG translation initiation codon and the short 5' untranslated region is not extended by transsplicing. The open reading frame is 1350 nucleotides in length and encodes a protein of 449 amino acids. The reading frame is not interrupted by introns and the primary transcript is probably not subjected to RNA editing. In the strictly anaerobic metabolism of giardia, NADP-dependent glutamate dehydrogenase activity participates along with alanine aminotransferase, in the cyclic dissipation of reducing equivalents (NADPH) through the conversion of pyruvate to alanine. The deduced amino acid sequence of the giardia protein exhibits substantial homology to numerous fungal and eubacterial NADP-dependent glutamate dehydrogenases. Comparisons of alignment gap positions and amino acid identities indicate that the giardia sequence is at least as similar or more similar to the eubacterial sequence than it is to the fungal sequence. This supports the hypothesis that giardia diverged very early from the eucaryotic lineage.

Amino Acid Sequence↗

PubMed2004

The hematological status, plasma vitamin B12 and folic acid levels, and intestinal pathology in rats infected with Giardia lamblia.

The purpose of our study was to investigate the hematological status, vitamin B12 and folic acid absorption and intestinal pathology after Giardia lamblia infection in a rat model. Adult Wistar rats were assigned randomly to receive human giardia cysts orally in the amount of 5 x 10(5) or 1.0 x 10(6) cysts, or none in the controls. The results showed that all the rats injected with giardia cysts became infected. The cyst output in the infected rats varied considerably. In rats infected with 5.0 x 10(5) giardia cysts, the incubation period until cyst output was 10 days compared with 4 days in rats infected with the higher amount of 1.0 x 106 giardia cysts. The highest peaks for cysts output in these 2 groups were on days 4-33, which decreased gradually to days 40-58. The hematocrit and hemoglobin levels in the infected rats were statistically significantly lower than in the controls on days 16, 22, 33, and 37 post-infection (p < 0.05). A reverse relationship between giardia cyst output and hemoglobin concentration was found in the infected rats (p = 0.05). There were no significant differences in plasma vitamin B12 and folic acid levels between the infected rats and the control rats. No pathological changes were found in the small intestine of infected rats. These findings suggest that giardiasis did not affect the absorption of plasma vitamin B12 and folic acid but caused anemia in a rat model.

Animals↗

PubMed2006

Evaluating Cryptosporidium and Giardia concentrations in combined sewer overflow.

Since the first identified Cryptosporidium outbreaks occurred in the 1980s and the massive 1993 Milwaukee, WI outbreak affected more than 400,000 people, the concern over the public health risks linked to protozoan pathogens Cryptosporidium and Giardia has grown. Cryptosporidium and Giardia, found in streams, rivers, groundwater, and soil, form hardy, disinfection-resistant oocysts and cysts. Both organisms are recognized causative agents of gastrointestinal illnesses linked to the consumption of contaminated surface or groundwater. This study, the first in a planned series to estimate the urban contribution to the total Cryptosporidium and Giardia receiving-water loads, focused on combined sewer overflow (CSO). CSOs are discharges of mixed untreated sewage and stormwater released directly into receiving waters during rainfall. This engineered relief is necessary to accommodate hydraulic strain when the combined rain and sanitary flows exceed the system capacity. Limited comprehensive data are available assessing the CSO discharge contribution as a source of these two pathogens. Works by States et al. and Gibson et al. each found Cryptosporidium and much greater Giardia concentrations in CSOs draining parts of Pittsburgh, PA. This project estimated the relative detection frequency and concentration of Cryptosporidium and Giardia in CSO. Analytical results were obtained using a modification of Method 1623, originally developed for much cleaner environmental samples. These data are useful for drinking water treatment plants located downstream of CSOs. It is also significant in determining the potential concentrations of parasites at treatment plant intakes and for assessing health risks for water contact and fishing activities. Commonly monitored indicator organisms (total coliform, fecal coliform, E. coli, Enterococcus, and fecal streptococcus), endospores, and selected physical and chemical parameters were analyzed to further describe the samples. CSO from urban areas was not found to be a significant contributor of Cryptosporidium, however, it was found to be a Giardia source.

Animals↗

PubMed1989

Purine deoxynucleoside salvage in Giardia lamblia.

Giardia lamblia is dependent on the salvage of preformed purines and pyrimidines, including deoxythymidine. Dependence on deoxynucleoside salvage is extremely unusual among eucaryotic cells (Moore, E. C., and Hurlbert, R. B. (1985) Pharmacol & Ther. 27, 167-196). The present study investigates the possibility that giardia lacks ribonucleotide reductase and depends entirely on deoxynucleoside salvage. A ribonucleotide reductase inhibitor, hydroxyurea, at concentrations up to 2 mM had no effect on the growth of giardia. This is 15-20 times the ED50 of hydroxyurea for the protozoans Trypanosoma cruzi, Trypanosoma gambiense, and Leishmania donovani. A lysate of giardia had no detectable ribonucleotide reductase. Although radiolabeled adenine, adenosine, guanine, and guanosine were readily incorporated into RNA by cultured cells, no adenine or adenosine and only trace amounts of guanine and guanosine were detectable in DNA. This is in contrast to deoxynucleosides, where 58% of deoxyadenosine and 10% of deoxyguanosine incorporated into nucleic acid were found in DNA. Phosphorylation of both deoxyadenosine and deoxyguanosine was catalyzed by a cell lysate of giardia when nucleoside kinase co-substrates were included in the assay but not when phosphotransferase co-substrates were present. The absence of detectable ribonucleotide reductase, the failure to incorporate purine nucleobases and nucleosides into DNA to any significant extent, the ready incorporation of deoxynucleosides into DNA, and the demonstration of a purine deoxynucleoside kinase suggest that giardia are dependent on the salvage of exogenous deoxynucleosides.

Animals↗

PubMed1986

Cytotoxicity of monoclonal antibodies to a subset of Giardia isolates.

Previous studies showed that some Giardia lamblia isolates differ and can be categorized on the basis of their DNA banding patterns after digestion with endonuclease restriction enzymes, surface antigens, and excretory-secretory (E-S) products. In the present study, monoclonal antibodies (McAb) were produced that reacted with one specific group of Giardia isolates. These McAb recognized a 170,000 dalton antigen, which was present on the surface of these Giardia and released into the medium as an E-S antigen. This antigen was previously characterized and found to distinguish this subgroup of Giardia. In addition, these McAb were cytotoxic only for this subgroup of Giardia. Immobilization occurred immediately, and killing was documented by 7 min. The mechanism(s) of killing remains unknown but was shown to be complement independent and did not occur with Fab'. These McAb identifies certain isolates and can be used to type Giardia.

Animals↗

PubMed1997

Ribosomal RNA sequencing reveals differences between the genotypes of Giardia isolates recovered from humans and dogs living in the same locality.

A polymerase chain reaction-based method for genotyping Giardia duodenalis isolates using a polymorphic region near the 5' end of the small subunit ribosomal (SSU) RNA gene is described. Analysis was performed using Giardia cysts purified directly from feces. Isolates were collected from humans and dogs living in isolated Aboriginal communities where Giardia infections are highly endemic. This is the first report of the genetic characterization of Giardia from dogs and humans living in the same locality. Comparison of the SSU-rRNA sequences from 13 human and 9 dog isolates revealed 4 different genetic groups. Groups 1 and 2 contained all of the human isolates, whereas groups 3 and 4 consisted entirely of Giardia samples recovered from dogs. One dog sample contained templates from both groups 2 and 3. These results suggest that zoonotic transmission of Giardia infections between humans and dogs does not occur frequently in these communities. The dog-associated SSU-rRNA sequences have not been reported before, suggesting a new G. duodenalis subgroup. A genetic basis for the differences observed between the groups was supported by sequence analysis of 9 in vitro cultured isolates that were placed into the same genetic groups established by enzyme electrophoresis.

Animals↗

PubMed1998

Efficacy of fenbendazole in the treatment of experimental Giardia infection in dogs.

OBJECTIVE: To evaluate the efficacy of fenbendazole as a treatment for Giardia sp. ANIMALS: 10 male and 10 female commercial-source Beagles. PROCEDURE: The experiment was conducted in 2 replicates. Dogs considered free of Giardia infection on the basis of results of 3 consecutive negative fecal examinations were experimentally infected with approximately 1,000 Giardia cysts isolated from dog feces. After verification of infection, the dogs were allocated to 2 groups (treated and untreated) and were housed in separate rooms. Treated dogs received 50 mg of fenbendazole/kg of body weight, p.o., daily, for 3 days. After treatment on the third day, treated dogs were removed from their runs, shampooed, rinsed with disinfectant, and returned to disinfected runs. Fecal samples were collected from all dogs 12 times during the next 25 days. RESULTS: Giardia cysts were found in the feces of every untreated dog during all or part of the test period. Nine of 10 treated dogs did not have Giardia cysts in any fecal sample examined; the other dog had a positive result on a single sample in the third week after treatment. CONCLUSION AND CLINICAL RELEVANCE: Fenbendazole, at the nematocidal label dosage, is an effective drug for treatment of Giardia infection in dogs.

Animals↗

PubMed2005

Giardia duodenalis infection and wastewater irrigation in Pakistan.

The risk of Giardia duodenalis (Giardia) infection in farmers using untreated wastewater in agriculture was investigated in the city of Faisalabad, Pakistan, through a cross-sectional study. The study found a significantly increased risk of (asymptomatic) Giardia infection in wastewater farming households when compared with farming households using regular (non-wastewater) irrigation water (OR 3.3, 95% CI 2.5-4.4). Textile labourers who were employed in the city of Faisalabad but who lived in the same village as the wastewater farmers showed a risk of Giardia infection in between that of wastewater and non-wastewater farming households (OR 2.4, 95% CI 1.9-3.1). This study suggests that exposure to wastewater with high Giardia concentrations carries an increased risk for (asymptomatic) Giardia infection.

Agricultural Workers' Diseases↗

PubMed1984

Occurrence of Giardia lamblia in children in day care centers.

We prospectively evaluated excretion of Giardia lamblia in children in day care centers in Houston by conducting two prevalence studies of 600 children enrolled in 30 DCC, day care centers, and an 18-month longitudinal study in 82 children in one center. In the two prevalence surveys, Giardia cysts were identified in 72 (21%) and 67 (26%) children, respectively, who provided stool specimens. Trophozoites were found in 15 (4%) and 8 (3%), respectively. There was no correlation between the frequency of recent diarrheal episodes and the finding of Giardia. Stool specimens containing cysts were significantly (P less than 0.0001) more frequent in the 13- to 30-month-old children than in children younger than 12 months. Children attending day care centers for more than 3 months were more likely to be excreting Giardia than those attending for less than 3 months. In the longitudinal study, cysts were detected in stool specimens from 27 (33%) of the 82 children at least once during the survey. Twelve children had Giardia cysts in weekly stool specimens for a mean of 6.2 +/- 1.2 months and trophozoites for 3.3 +/- 1.2 months. The number of enteric symptoms observed in children and the classification of nutritional status based on monthly height and weekly weight measurements did not differ significantly when infected and noninfected children were compared. Asymptomatic Giardia excretion in children younger than 36 months is common and appears to be well tolerated.

Child Day Care Centers↗