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PubMed1994

Detection of Cryptosporidium and Giardia intestinalis in Bedouin children from southern Israel.

During an 18 month period, a total of 4796 stool specimens collected from 151 Bedouin children enrolled in a cohort study and followed from birth, were screened for Giardia intestinalis, Cryptosporidium spp. and other intestinal parasites. Specimens were collected in phenol-alcohol-formalin (PAF) preservative and examined prior to, and after, formalin-ether concentration (FEC). During 6 months of the second year Giardia intestinalis was observed in 17.6% of the specimens and Cryptosporidium in 0.9% as compared with 1.8% (Giardia intestinalis) and 1.6% (Cryptosporidium) observed during the first year. Giardia intestinalis was detected in 8.4% (407/4796) of all the samples examined and Cryptosporidium in 1.3% (63/4796). Other intestinal protozoan parasites and helminthic ova demonstrated in the stool specimens included: Entamoeba coli (0.1%); Entamoeba histolytica (< 0.1%); Hymenolepis nana (0.1%); and Trichuris trichiura (< 0.1%). Mixed infection with 2 parasites was observed in 0.3% of the specimens. PAF fixation was found to be highly effective in preserving the integrity and antigenicity of both Cryptosporidium-oocysts and Giardia intestinalis-cysts. The detection rate of Giardia intestinalis and Cryptosporidium before FEC was not significantly different from that obtained after FEC, showing differences of only 1% and 3% for Giardia intestinalis and Cryptosporidium, respectively.

Animals↗

PubMed1988

Giardia-bile salt interactions in vitro and in vivo.

Giardia lamblia predominantly colonizes the proximal small intestine where bile is plentiful. We have investigated interactions between bile and this parasite by (i) examining the specificity of the stimulatory effect of bile on parasite growth in vitro, (ii) studying the possible association between giardiasis and bile salt deconjugation in vivo, and (iii) quantifying bile salt uptake by Giardia and relating this to uptake by other microorganisms. Our findings indicate that the growth promoting effects of ox bile and pure bile salt (sodium glycocholate) are, as far as is known, specific for Giardia, since the growth of a related protozoon, Trichomonas vaginalis, and a variety of enteric bacteria was either unchanged or inhibited. We were unable to detect deconjugated ('free') bile salt in duodenal fluid from UK patients with giardiasis and found no evidence to suggest that Giardia deconjugated bile salts in vitro. However, Giardia avidly took up conjugated bile salt, apparently in a concentration-dependent manner and to a much greater degree than Trichomonas and enteric bacteria. Thus, bile specifically stimulates growth of Giardia, and bile salt is avidly consumed by the parasite. The mechanism by which bile stimulates parasite growth is unknown, but uptake of conjugated bile salt by Giardia could reduce intraluminal bile salt concentrations and possibly interfere with micellar solubilization of fat. This may contribute to the steatorrhoea which is well recognized in symptomatic patients with giardiasis.

Animals↗

PubMed1989

Giardia cyst wall-specific carbohydrate: evidence for the presence of galactosamine.

Gas chromatographic (GC), mass spectrometric (MS), lectin binding and enzymatic analyses of the carbohydrates from Giardia cyst walls, intact cysts and trophozoites were performed to investigate the carbohydrate composition of Giardia cyst walls and to test the hypothesis that the Giardia cyst wall is composed largely of chitin. Galactosamine, verified by MS, was present in Giardia cyst walls and intact cysts (ca. 47 nmol 10(-6) cysts). Since not even trace amounts of it were detected in trophozoites by either GC or lectin binding, galactosamine is hypothesized to be a cyst wall-specific amino hexose. Based on the putative binding affinity of Phaseolus limensis lectin, galactosamine may be present in cyst walls as N-acetylgalactosamine. Neither glucosamine nor sialic acid were detected in as much as 11 mg dry weight of cysts, cyst walls, or trophozoites. Glucose, the most abundant carbohydrate, and ribose were detected in Giardia cysts and trophozoites. Galactose (ca. 10 nmol 10(-6) cysts) was detected in cysts but not in trophozoites. The lack of detectable levels of (1) glucosamine in cyst wall hydrolysates, (2) cyst staining by Calcofluor M2R, (3) endogenous chitinase activity and (4) N-acetylglucosamine when cysts served as a substrate for exogenous chitinase suggests that the Giardia cyst wall is not composed largely of chitin as previously reported. beta-N-Acetylgalactosaminidase, EC 3.2.1.32, activity was detected in cysts and trophozoites and represents the first carbohydrate splitting hydrolase detected in Giardia.

Animals↗

PubMed2002

Genetic manipulation of Giardia lamblia.

Giardia lamblia is a flagellated protozoan that infects several species including humans and is a major agent of waterborne outbreaks of diarrhea. G. lamblia is also important in the study of basic eukaryotic molecular biology and evolution; however, it has been difficult to employ standard genetic methods in the study of Giardia. Over the past 6 years, two transfection systems were developed and used for the genetic manipulation of G. lamblia. Both systems allow transient or stable transfection of Giardia and/or foreign genes. The DNA-based transfection system allows electroporation of circular or linear plasmid DNA into trophozoites. The RNA virus-based transfection system requires electroporation of in vitro transcribed RNA into GLV-infected trophozoites. Because G. lamblia is one of the most rudimentary eukaryotes, its processes of transcription, translation and protein transport, as well as its metabolic and biochemical pathways, are of interest. Study of these areas will continue to be advanced using transfection in combination with cellular and molecular tools. Several groups have combined these technologies with other techniques to study protein transport and the transcriptional and post-transcriptional regulation of Giardia genes, including encystation-specific and variant surface protein genes. In addition, coupling antisense techniques with transfection has permitted functional knockout of Giardia metabolic genes, allowing Giardia metabolic pathways to be studied. In the near future, both transfection systems will be potent tools in our investigations of the perplexing questions in Giardia biology.

Animals↗

PubMed1998

Protein synthesis in Giardia lamblia may involve interaction between a downstream box (DB) in mRNA and an anti-DB in the 16S-like ribosomal RNA.

Giardia lamblia, a parasitic protozoan, has been regarded as one of the most conserved eukaryotes evolved from the prokaryotes. One of its unique features appears to be the unusually short 5'-untranslated regions (UTR) (1-6 nucleotides (nts)) and the apparent absence of 5'-cap structures from its mRNAs. Transfection of the Giardia trophozoites with luciferase-encoding chimeric transcripts, flanked by the 5'- and 3'-ends of giardiavirus (GLV) (+)-strand RNA, indicated that the translational efficiency was enhanced by 5000-fold when the 5'-viral sequence extended 264 nts into the capsid coding region and fused with the luciferase open reading frame (ORF). A 13-nt downstream box (DB) was identified within this region which complements a 15-nt sequence between nts # 1382 and 1396 near the 3'-end of the Giardia 16S-like ribosomal RNA (the anti-DB). Deletion or scrambling of this DB in the mRNA leads to a significant loss of the translational efficiency in Giardia. A Shine-Dalgarno (SD)-like element was also identified at 9-14 nts upstream from the initiation codon in the viral (+)-strand RNA, but alteration of its sequence led to no change in translation. Using the sequence complementary to ribosomal anti-DB to probe the Giardia mRNAs available in the databases, each mRNA was found to contain a putative DB with an average length from 8 to 13 nts. It is thus possible that initiation of translation in Giardia may involve a DB in the coding region of mRNA that may bind to a putative anti-DB in the small ribosomal RNA through base pairing. This mechanism of ribosome recruitment, which finds a potential parallel in Escherichia coli, could illustrate a relatively close distance between Giardia and prokaryotes in terms of translation initiation, and may provide a model for studying the evolution of translation machinery.

5' Untranslated Regions↗

PubMed2005

In vivo killing of Giardia trophozoites harbouring bacterial endosymbionts by intestinal Paneth cells: an ultrastructural study.

To date Paneth cells have not previously been reported to kill Giardia trophozoites and other protozoa in vivo. Here we report the first evidence for in vivo killing of Giardia trophozoites by intestinal Paneth cells. Transmission electron microscopic (TEM) examination of duodenal specimens taken from naturally infected mice revealed that only Giardia trophozoites harbouring peripheral bacterial endosymbionts were destroyed and lysed in the vicinity of the activated Paneth cells. Additionally, intestinal epithelium was more affected by Giardia harbouring bacterial endosymbionts than Giardia with no endosymbionts. Our findings imply that the bacterial endosymbionts within Giardia trophozoites have a role in both host protective and pathological mechanisms, probably through altering the trophozoite antigencity. These observations might shed light on the diversity in infectivity and host specificity of Giardia species.

Animals↗

PubMed2003

Evaluation of an internal positive control for Cryptosporidium and Giardia testing in water samples.

AIMS: An internal positive control for Cryptosporidium and Giardia monitoring was evaluated for use in routine water monitoring quality control. The control, known as ColorSeed C&G (BTF Pty Ltd, Sydney, Australia), is a suspension containing exactly 100 Cryptosporidium oocysts and 100 Giardia cysts that have been modified by attachment of Texas Red to the cell wall, allowing them to be differentiated from unmodified oocysts and cysts. The control enables recovery efficiencies to be determined for every water sample analysed. METHODS AND RESULTS: A total of 494 water samples were seeded with ColorSeed C&G and with unlabelled Cryptosporidium and Giardia and then analysed. Additionally, the robustness of the ColorSeed labelling was challenged with various chemical treatments. Recoveries were significantly lower for the ColorSeed Texas Red labelled Cryptosporidium and Giardia than recoveries of unlabelled Cryptosporidium and Giardia. However, the differences in recoveries were small. On average ColorSeed Cryptosporidium recoveries were 3.3% lower than unlabelled Cryptosporidium, and ColorSeed Giardia recoveries were 4% lower than unlabelled Giardia. CONCLUSIONS: ColorSeed C&G is suitable for use as an internal positive control for routine monitoring of both treated and raw water samples. SIGNIFICANCE AND IMPACT OF THE STUDY: The small differences in recoveries are unlikely to limit the usefulness of ColorSeed C&G as an internal positive control. The ColorSeed labelling was found to be robust after different treatments.

Animals↗

PubMed1986

Natural history of Giardia infection of infants and children in rural Guatemala and its impact on physical growth.

Longitudinal data on Giardia excretion, diarrheal disease, and physical growth during the first 3 yr of life collected more than 20 yr ago in 45 Guatemalan children were analyzed. This report describes the natural history of this infection and estimates its effects on growth. All children had at least one Giardia infection, prevalence and incidence rates reaching 20.2% and 5.3%, respectively by the end of the third year. The mean number of Giardia infections per child increased from 0.7 in the first to 3.6 in the third year. More than 40% of these infections lasted 2-6 wk or more and were commonly associated with diarrhea. Weight velocity was significantly lower in the second year of life in Giardia-infected than in Giardia-negative children (p = 0.03). The duration of Giardia episodes and their association with diarrhea appeared to be the most important factors associated with growth disturbance. Although simultaneous infection with other enteropathogens occurred in many children, our findings suggest that Giardia infection may have independent deleterious effects on children's growth.

Body Height↗

PubMed2004

Secretory IgA antibody responses in Venezuelan children infected with Giardia duodenalis.

We standardized and evaluated an ELISA technique for the detection of total and specific anti-Giardia duodenalis secretory IgA antibodies (sIgA). Samples of saliva and serum of 161 Venezuelan schoolchildren were analysed. After stool examination, 66 children were diagnosed to be infected with Giardia duodenalis, 22 with other protozoa, and 73 non-parasitized. The mean (+ 2 SD) values of secretory IgA in the non-parasitized group was considered as the criterion of positivity. The levels of total and specific anti-Giardia sIgA were significantly higher in children with Giardia compared with the group with other protozoa (p < 0.01) and the non-parasitized group (p < 0.001). The ELISA technique developed showed values of sensitivity and specificity of 74 and 94 per cent, respectively, a predictive value of 92 per cent for positive samples and 80 per cent for negative samples. Specific anti-Giardia IgA serum levels showed a low sensitivity (57 per cent) and a predictive value for negative samples (53 per cent). Our results suggest that secretory anti-Giardia IgA levels measured in saliva samples may reflect local intestinal IgA responses elicited by these parasites. Thus, determinations of the levels of sIgA anti-Giardia could be a useful diagnostic tool for giardiasis in children.

Animals↗

PubMed2006

Occurrence of Cryptosporidium oocysts and Giardia cysts in sewage in Norway.

Samples of sewage influent from 40 sewage treatment works (STW) throughout Norway were examined for Cryptosporidium oocysts and Giardia duodenalis cysts. Both parasites were detected frequently (80% of STW were Cryptosporidium positive; 93% of STW were Giardia positive) and at maximum concentrations of > 20,000 parasites/liter. The data suggest giardiasis is more widespread, and/or occurs with greater infection intensity, than cryptosporidiosis in Norway. STW serving higher person equivalents were more likely to be positive and had higher parasite concentrations. Parasite concentrations were used to estimate the proportion of contributing populations that could be clinically infected. For Cryptosporidium, the highest estimates were up to 5 per 100,000 individuals for two populations in eastern Norway. For Giardia, the highest estimate was 40 infected per 100,000 persons (approximately five times the usual national annual average) contributing to an STW in western Norway. As this population experienced a large waterborne giardiasis outbreak 6 months after sampling, it can be speculated that regular challenge with Giardia may occur here. Most Giardia isolates in sewage influent were assemblage A, although some assemblage B isolates were detected. There was substantial heterogeneity, but most samples contained isolates similar to genotype A3. Removal efficiencies at two STW with secondary treatment processes were estimated to be approximately 50% for Cryptosporidium and > 80% for Giardia. An STW with minimal treatment had negligible removal of both parasites. Many STW in Norway have minimal treatment and discharge effluent into rivers and lakes, thus, risk of contamination of water courses by Cryptosporidium and Giardia is considerable.

Animals↗

PubMed1988

Cross-species transmission of Giardia spp.: inoculation of beavers and muskrats with cysts of human, beaver, mouse, and muskrat origin.

Giardia cysts isolated from humans, beavers, mice, and muskrats were tested in cross-species transmission experiments for their ability to infect either beavers or muskrats. Giardia cysts, derived from multiple symptomatic human donors and used for inoculation of beavers or muskrats, were shown to be viable by incorporation of fluorogenic dyes, excystation, and their ability to produce infections in the Mongolian gerbil model. Inoculation of beavers with 5 x 10(5) Giardia lamblia cysts resulted in the infection of 75% of the animals (n = 8), as judged by the presence of fecal cysts or intestinal trophozoites at necropsy. The mean prepatent period was 13.1 days. An infective dose experiment, using 5 x 10(1) to 5 x 10(5) viable G. lamblia cysts collected by fluorescence-activated cell sorting, demonstrated that doses of between, less than 50, and less than 500 viable cysts were required to produce infection in beavers. Scanning electron microscopy of beaver small intestine revealed that attachment of G. lamblia trophozoites produced lesions in the microvillous border. Inoculation of muskrats with G. lamblia cysts produced infections when the dose of cysts was equal to or greater than 1.25 x 10(5). The inoculation of beavers with Giardia ondatrae or Giardia muris cysts did not produce any infection; however, the administration to muskrats of Giardia cysts of beaver origin resulted in the infection of 62% of the animals (n = 8), with a prepatent period of 5 days. Our results demonstrated that beavers and muskrats could be infected with Giardia cysts derived from humans, but only by using large numbers of cysts.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2001

Adherence of Giardia lamblia trophozoites to Int-407 human intestinal cells.

Attachment of Giardia lamblia trophozoites to enterocytes is essential for colonization of the small intestine and is considered a prerequisite for parasite-induced enterocyte dysfunction and clinical disease. In this work, coincubation of Giardia with Int-407 cells, was used as an in vitro model to study the role of cytoskeleton and surface lectins involved in the attachment of the parasite. This interaction was also studied by scanning and transmission electron microscopy. Adherence was dependent on temperature and was maximal at 37 degrees C. It was reduced by 2.5 mM colchicine (57%), mebendazole (10 microg/ml) (59%), 100 mM glucose (26%), 100 mM mannose (22%), 40 mM mannose-6-phosphate (18%), and concanavalin A (100 microg/ml) (21%). No significant modification was observed when Giardia was pretreated with cytochalasins B and D and with EDTA. Giardia attachment was also diminished by preincubating Int-407 cells with cytochalasin B and D (5 microg/ml) (16%) and by glutaraldehyde fixation of intestinal cells and of G. lamblia trophozoites (72 and 100%, respectively). Ultrastructural studies showed that Giardia attaches to the Int-407 monolayer predominantly by its ventral surface. Int-407 cells contact trophozoites with elongated microvilli, and both trophozoite imprints and interactions of Giardia flagella with intestinal cells were also observed. Transmission electron microscopy showed that Giardia lateral crest and ventrolateral flange were important structures in the adherence process. Our results suggest a combination of mechanical and hydrodynamic forces in trophozoite attachment; surface lectins also seem to mediate binding and may be involved in specific recognition of host cells.

Animals↗

PubMed2005

Identification in the ancient protist Giardia lamblia of two eukaryotic translation initiation factor 4E homologues with distinctive functions.

Eukaryotic translation initiation factor 4E (eIF4E) binds to the m(7)GTP of capped mRNAs and is an essential component of the translational machinery that recruits the 40S small ribosomal subunit. We describe here the identification and characterization of two eIF4E homologues in an ancient protist, Giardia lamblia. Using m(7)GTP-Sepharose affinity column chromatography, a specific binding protein was isolated and identified as Giardia eIF4E2. The other homologue, Giardia eIF4E1, bound only to the m(2,2,7)GpppN structure. Although neither homologue can rescue the function of yeast eIF4E, a knockdown of eIF4E2 mRNA in Giardia by a virus-based antisense ribozyme decreased translation, which was shown to use m(7)GpppN-capped mRNA as a template. Thus, eIF4E2 is likely the cap-binding protein in a translation initiation complex. The same knockdown approach indicated that eIF4E1 is not required for translation in Giardia. Immunofluorescence assays showed wide distribution of both homologues in the cytoplasm. But eIF4E1 was also found concentrated and colocalized with the m(2,2,7)GpppN cap, 16S-like rRNA, and fibrillarin in the nucleolus-like structure in the nucleus. eIF4E1 depletion from Giardia did not affect mRNA splicing, but the protein was bound to Giardia small nuclear RNAs D and H known to have an m(2,2,7)GpppN cap, thus suggesting a novel function not yet observed among other eIF4Es in eukaryotes.

Amino Acid Sequence↗

PubMed1987

Usefulness of an enzyme-linked immunosorbent assay for detection of Giardia antigen in feces.

The usefulness of a recently developed enzyme-linked immunosorbent assay which detects Giardia lamblia antigen in feces was determined in experimentally infected humans. Giardia antigen was determined in serially collected fecal specimens from humans inoculated with two Giardia isolates, GS/M and Isr. A total of 277 stools from 18 volunteers were tested, 74 from Isr-inoculated volunteers and 203 from GS/M-inoculated volunteers. None of the five Isr-inoculated volunteers became infected, and none of their stools contained Giardia antigen. In contrast, all of the 13 GS/M-inoculated volunteers became infected, and Giardia antigen was present one or more times in the stools of each. Of 203 stools from GS/M-inoculated volunteers, 73 contained Giardia cysts, and 69 of these (94.5%) had detectable antigen. In contrast, 108 of the 203 specimens were positive for Giardia antigen and only 73 had cysts. Most antigen-positive but cyst-negative specimens occurred during treatment, but during patency 71 stools contained antigen and 65 had cysts. The enzyme-linked immunosorbent assay is infections and is easier to perform.

Antigens, Protozoan↗

PubMed1999

Giardia induces proliferation and interferon gamma production by intestinal lymphocytes.

BACKGROUND: Murine intraepithelial lymphocytes kill Giardia lambia; responses of human intestinal lymphocytes to this parasite are unknown. AIMS: To examine giardia induced proliferation, interferon gamma production, migration, and cytotoxicity by lymphocytes from the human intestine and peripheral blood. METHODS: Giardia were added to intraepithelial lymphocytes, lamina propria lymphocytes, and peripheral blood lymphocytes, obtained from jejunal mucosa and blood of otherwise healthy patients undergoing gastric bypass surgery for morbid obesity. Proliferation was measured by 3H-thymidine incorporation; frequency of proliferation precursors, by limiting dilution analysis; interferon gamma production, by ELISA; cytotoxicity, by 51Cr release of radiolabelled giardia and by release of serine esterases by effector lymphocytes that mediate cytotoxicity. RESULTS: The CD4+ T lymphocytes from intestine and blood proliferated in response to giardia. The stimulus by the parasite was mitogenic rather than antigenic due to the fact that the peak response was on day 3 rather than day 6, and the large number of precursors was in the range of that for mitogens. CD4+ T lymphocytes from both sites produced interferon gamma in response to giardia. Lymphocytes did not migrate towards or kill the parasite. CONCLUSIONS: Giardia induced the same degree of proliferation and interferon gamma production by CD4+ T lymphocytes in intestine and blood, but did not trigger cytotoxicity or migration.

Animals↗

PubMed2002

Prevalence of Giardia and Cryptosporidium and characterization of Cryptosporidium spp. isolated from wildlife, human, and agricultural sources in the North Saskatchewan River Basin in Alberta, Canada.

The environmental distribution of Giardia spp. and Cryptosporidium spp. is dependent upon human, agricultural, and wildlife sources. The significance of each source with regard to the presence of parasites in the environment is unknown. This 2-year study examined parasite prevalence in human sewage influent, wildlife, and agricultural sources associated with the North Saskatchewan River Basin in Alberta, Canada. Fecal samples were collected from cow-calf, dairy, and hog operations in the watershed area. Sewage-treatment facilities were sampled bimonthly during the 2-year study, and wildlife scat was collected at locations along tributaries of the North Saskatchewan River. All samples were analyzed for the presence of Giardia and Cryptosporidium, using sucrose-gradient separation followed by immunofluorescent microscopy. Giardia and Cryptosporidium were detected in all three sources. The lowest prevalence of both Giardia (3.28%) and Cryptosporidium (0.94%) was found in wildlife, with 6 of 19 species testing positive. Sewage influent had the highest prevalence of Giardia (48.80%) and Cryptosporidium parvum-like oocysts (5.42%); however, the concentration of both parasites was minimal compared with the concentration detected in cattle feces. Cow-calf sources contained the highest concentration of Giardia (mean 5800/g feces, P < 0.01), and dairy sources contained the highest concentration of C. parvum-like oocysts (mean 295/g feces, P < 0.01). Although prevalence and concentration are higher in cattle feces than in sewage, the Giardia and Cryptosporidium in animal manure do not have direct access to water draining into the North Saskatchewan River. PCR-based characterization of rDNA from isolates of Cryptosporidium collected from Alberta human, pig, calf, mature steer, dog, cat, and beaver hosts revealed distinct genetic differences that may reflect host specificity.

Animals↗

PubMed2002

Giardia in beaver (Castor canadensis) and nutria (Myocastor coypus) from east Texas.

We examined the prevalence of Giardia sp. infection in nuisance beaver (Castor canadensis) and nutria (Myocastor coypus) in east Texas. From October 1992 through September 1993, 100 beaver and 30 nutria were collected in routine wildlife management activities conducted by the U.S. Department of Agriculture-Animal and Plant Health Inspection Service-Texas Animal Damage Control Service. Fecal and duodenal mucoid samples were preserved from each animal. Fecal samples were examined for the occurrence of Giardia sp. cysts using the Merifluor immunoassay detection kit: 30 beaver (30.0%) and 20 nutria (66.7%) were positive for Giardia sp. Duodenal mucoid samples were examined for Giardia sp. trophozoites using trichrome staining. with 26 beaver (26.0%) and 20 nutria (73.3%) testing positive. Combining both techniques resulted in 33 beaver (33.0%) and 22 nutria (73.3%) testing positive for Giardia sp. We found no relationship between Giardia sp. and host age, sex, river system, habitat, county, or season in beaver. However, a relationship was found when season and habitat were considered together. No relationship was found between Giardia sp. and age, river system, habitat, county, or season in nutria: however, more males (87.5%) were infected than females (46.4%).

Animals↗

PubMed2006

Transport of giardia and manure suspensions in saturated porous media.

Experiments were conducted to elucidate the transport behavior of cysts of Giardia and manure suspensions through several aquifer sands. Decreasing the median grain size of the sand resulted in lower peak effluent concentrations and increased deposition of the Giardia and manure particles in the sand near the column inlet. The effluent concentration curves for the manure suspensions also exhibited asymmetric shapes that tended to include larger particle sizes as the manure suspension was continuously added. Simulations of the transport of Giardia and manure particles using a simple and flexible power law model for the solid-water mass exchange term provided a satisfactory description of the effluent and spatial distribution data. The cumulative size distribution (CSD) of manure particles in the suspension initially and after passage through the packed columns was used to identify the mechanisms that were controlling the deposition of manure particles and Giardia. The CSD data indicated that manure particles were completely removed at early times by mechanical filtration and/or straining when the ratio of the particle to the median grain diameter was greater than 0.003 to 0.017. However, the CSD changed with increasing time due to deposition-induced filling of straining sites. The Giardia transport was controlled by straining. For a given sand, higher effluent concentrations of Giardia were observed in the presence than in the absence of manure suspension. The relative increase of Giardia in the effluent concentrations varied from 75 to 172%. Hence, pathogen transport studies conducted in the absence of manure suspension may underestimate transport potential in manure-contaminated environments.

Animals↗