Molecular characterizations of Cryptosporidium, Giardia, and Enterocytozoon in humans in Kaduna State, Nigeria

The use of molecular diagnostic tools in epidemiological investigations of Cryptosporidium, Giardia, and Enterocytozoon has provided new insights into their diversity and transmission pathways. In this study, 157 stool specimens from 2-month to 70-year-old patients were collected, a polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) analysis of the small subunit (SSU) rRNA gene was used to detect and differentiate Cryptosporidium species, and DNA sequence analysis of the 60 kDa glycoprotein (gp60) gene was used to subtype Cryptosporidium hominis and Cryptosporidium parvum. Giardia duodenalis, and Enterocytozoon bieneusi in the specimens were detected using PCR and sequence analysis of the triosephosphate isomerase (tpi) gene and internal transcribed spacer (ITS), respectively. C. hominis and C. parvum were found in two (1.3%) and one (0.6%) specimen respectively, comprising of Ia and IIe (with 8 nucleotide substitutions) subtype families. The G. duodenalis A2 subtype was detected in five (3.2%) specimens, while four genotypes of E. bieneusi, namely A, type IV, D and WL7 were found in 10 (6.4%) specimens. Children aged two years or younger had the highest occurrence of Cryptosporidium (4.4%) and Enterocytozoon (13.0%) while children of 6 to 17 years had the highest Giardia infection rate (40.0%). No Cryptosporidium, Giardia, and Enterocytozoon were detected in patients older than 60 years. Enterocytozoon had high infection rates in both HIV-positive (3.3%) and HIV-negative (8.3%) patients. Results of the study suggest that anthroponotic transmission may be important in the transmission of Cryptosporidium spp. and G. duodenalis while zoonotic transmissions may also play a role in the transmission of E. bieneusi in humans in Kaduna State, Nigeria.     

Detection of Cryptosporidium sp. in two new seal species, Phoca vitulina and Cystophora cristata, and a novel Cryptosporidium genotype in a third seal species, Pagophilus groenlandicus, from the Gulf of Maine

Data on the geographic distribution and host specificity of Cryptosporidium spp. are critical for developing an understanding of likely transmission patterns in nature. During a molecular-based survey of fecal samples from 293 terrestrial and aquatic animals in Maine, USA, we detected Cryptosporidium sp. in 11 harbor seals (Phoca vitulina), 1 hooded seal (Cystophora cristata), and 1 harp seal (Pagophilus groenlandicus). None of the terrestrial or freshwater mammal fecal samples or bird samples tested positive for Cryptosporidium sp. However, the sequencing results of the small subunit (ssu) rRNA gene indicate that the seals were infected with an undescribed species of Cryptosporidium , previously isolated only from ringed seals (Phoca hispida) in northern Quebec, Canada. In addition, the Cryptosporidium sp. detected in the harp seal is significantly different from the previously observed Cryptosporidium sp. in other seals. We confirmed the genetic distinctiveness of this Cryptosporidium genotype and the identity of the other Cryptosporidium sp. seal ssu rRNA sequences by using data from the 70-kDa heat shock protein gene. Based on phylogenetic reconstructions of both genes, it seems that either Cryptosporidium canis or C. felis are sister species to the seal associated Cryptosporidium spp. Our findings extend the range of " Cryptosporidium sp. seal" well south of the 55th parallel, add other species to the list of seals affected by Cryptosporidium sp., and highlight the presence of unrecognized population and potentially species level variation in Cryptosporidium.     

Cryptosporidium,Giardia, and Cyclospora in ancient Peruvians

Twenty-two coprolites of human origin, collected from excavations along the north-central coast of Peru, were examined using fluorescent microscopy for the presence of fecal parasites, with emphasis on Cryptosporidium sp., Giardia sp., and Cyclospora sp. Three samples were positive. One coprolite dated between ca. 2,375 and 1,525 BC contained Giardia sp. cysts. This coprolite corresponded to the Peruvian preceramic period. Another positive coprolite ca. AD 770-830 corresponded to Epoch 3 of the Middle Horizon and contained Cryptosporidium sp. oocysts. The third positive coprolite (corresponding to the Middle Horizon. ca. AD 500-900) contained Giardia sp. cysts. This report demonstrates that Giardia sp. and Cryptosporidium sp. were present in Peruvian coastal populations for at least 4,300 and 1,100 BP.     

Cryptosporidium sp. and Giardia sp. infections in mountain gorillas (Gorilla gorilla beringei) of the Bwindi Impenetrable National Park, Uganda

For conservation purposes and because of growing ecotourism, some mountain gorilla (Gorilla gorilla beringei) populations have been habituated to humans. Fecal specimens (n = 100) of nonhabituated and human-habituated gorillas (5 populations; 6 age classes) were tested for Cryptosporidium sp. oocysts and Giardia sp. cysts by conventional staining and immunofluorescent antibody (IFA). Cryptosporidium sp. infections (prevalence 11%) were not restricted to very young gorillas but were observed in 3-yr-old to >12-yr-old gorillas; most of the infections (73%) occurred in human-habituated gorillas. The prevalence of Giardia sp. infections was 2%; 1 nonhabituated gorilla was concomitantly infected. Oocysts of Cryptosporidium sp. in the gorilla stools were morphologically, morphometrically, and immunologically undistinguishable from a bovine isolate of Cryptosporidium parvum oocysts. Mean concentration of Cryptosporidium sp. oocysts and Giardia sp. cysts in gorilla stools was 9.39x10(4)/g, and 2.49x10(4)/g, respectively. There was no apparent relationship between oocyst concentration and gorilla age, sex, or habituation status. Most Cryptosporidium sp. infections found in gorillas with closest proximity to people may be a result of the habituation process and ecotourism. This study constitutes the first report of Cryptosporidium sp. infections in the family Pongidae, in the free-ranging great apes, and in the species of gorilla.     

Giardia sp. and Cryptosporidium sp. infections in primates in fragmented and undisturbed forest in western Uganda

In June 2005, we collected 115 fecal samples from wild primates in western Uganda and examined them for Cryptosporidium sp. and Giardia sp. with the use of immunofluorescent antibody (IFA) detection. We sampled primates from an undisturbed forest in Kibale National Park and from 3 highly disturbed forest fragments outside the park. Of disturbed forest samples, red colobus (Pilocolobus tephrosceles) and red-tailed guenons (Cercopithecus ascanius) harbored species of Cryptosporidium or Giardia, but black-and-white colobus (Colobus guereza) did not. All primate samples from undisturbed forest were negative for both parasites. Seven of 35 (20%) red colobus and 1 of 20 red-tailed guenons (5%) from forest fragments were infected with either Cryptosporidium sp. or Giardia sp. The presence of Cryptosporidium and Giardia species in primates living in forest fragments, but not in primates in undisturbed forest, suggests that habitat disturbance may play a role in transmission or persistence of these pathogens.     

Cryptosporidium and Giardia in marine-foraging river otters (Lontra canadensis) from the Puget Sound Georgia Basin ecosystem

Species of Cryptosporidium and Giardia can infect humans and wildlife and have the potential to be transmitted between these 2 groups; yet, very little is known about these protozoans in marine wildlife. Feces of river otters (Lontra canadensis), a common marine wildlife species in the Puget Sound Georgia Basin, were examined for species of Cryptosporidium and Giardia to determine their role in the epidemiology of these pathogens. Using ZnSO4 flotation and immunomagnetic separation, followed by direct immunofluorescent antibody detection (IMS/DFA), we identified Cryptosporidium sp. oocysts in 9 fecal samples from 6 locations and Giardia sp. cysts in 11 fecal samples from 7 locations. The putative risk factors of proximate human population and degree of anthropogenic shoreline modification were not associated with the detection of Cryptosporidium or Giardia spp. in river otter feces. Amplification of DNA from the IMS/DFA slide scrapings was successful for 1 sample containing > 500 Cryptosporidium sp. oocysts. Sequences from the Cryptosporidium 18S rRNA and the COWP loci were most similar to the ferret Cryptosporidium sp. genotype. River otters could serve as reservoirs for Cryptosporidium and Giardia species in marine ecosystems. More work is needed to better understand the zoonotic potential of the genotypes they carry as well as their implications for river otter health.     

Prevalence of Cryptosporidium spp. and Giardia spp. in five marine mammal species

Cryptosporidium spp. and Giardia spp. are protozoan parasites that are often associated with severe diarrheal disease in a variety of mammals. Although these parasites have been extensively studied in terrestrial ecosystems, little is known about either parasite in the marine environment. Therefore, the objective of this study was to determine the prevalence of both Cryptosporidium spp. and Giardia spp. in 5 marine mammal species. Fecal samples were collected from 39 bowhead whales (Balaena mysticetus), 49 North Atlantic right whales (Eubalaena glacialis), 31 ringed seals (Phoca hispida), 22 bearded seals (Erignathus barbatus), and 18 beluga whales (Delphinapterus leucas) between 1998 and 2003. Using an immunofluorescent assay, parasites were detected in the feces of bowhead whales, right whales, and ringed seals, while neither parasite was detected in samples from bearded seals or beluga whales. Overall, prevalences were highest in ringed seals (Cryptosporidium spp., 22.6%; Giardia spp., 64.5%) and right whales (Cryptosporidium spp., 24.5%; Giardia spp., 71.4%) and lowest in bowhead whales (Cryptosporidium spp., 5.1%; Giardia spp., 33.3%). To our knowledge, this is the first report of Cryptosporidium spp. and Giardia spp. in either whale species and of Cryptosporidium spp. in the ringed seal.     

Detection and characterization of a Cryptosporidium isolate from a southern elephant seal (Mirounga leonina) from the Antarctic peninsula

The presence of Cryptosporidium and Giardia in 221 fecal samples from different species of Antarctic pinnipeds was investigated by immunofluorescence microscopy and PCR. Cryptosporidium, a skunk-like genotype, was detected only in a southern elephant seal. Giardia was not detected. This is the first report of a Cryptosporidium sp. in Antarctic marine mammals.     

Cryptosporidium pig genotype II diagnosed in pigs from the state of Rio De Janeiro, Brazil

Pigs may represent a source of Cryptosporidium sp. infection to humans. The objective of this study was to identify the Cryptosporidium species present in pigs from the State of Rio de Janeiro, Brazil, and verify what risks pigs represent in the transmission of human cryptosporidiosis, because there is no such information to date in Brazil. Ninety-one samples of pig feces were collected from 10 piggeries in 2 municipalities located in the north and northwest regions of the State of Rio de Janeiro, Brazil. A nested polymerase chain reaction (PCR) protocol to amplify an 830-bp fragment of the small subunit rDNA (SSU rRNA) gene was followed by sequencing of all positive PCR samples. Two samples (2.2%) were Cryptosporidium sp. positive and were identified as pig genotype type II (PGII). This genotype has been observed in an immunocompetent person, in cattle without pigs nearby, and from a potential human source. Its potential for zoonotic transmission is little known and should be rigorously studied.     

Molecular characterization of Cryptosporidium sp. isolated from northern Alaskan caribou (Rangifer tarandus)

Cryptosporidium sp. was found in 3 out of 49 caribou (Rangifer tarandus) from northern Alaska. Segments of both the 18S ribosomal RNA and the heat shock protein genes were amplified from the caribou isolate and compared with that obtained from an isolate from a wild white-tailed deer (Odocoileus virginianus) in Virginia as well as other species and isolates available from GenBank. Analyses showed the white-tailed deer isolate to be identical with the C. parvum cattle genotype; however, the caribou isolate represents a new genotype closely related to C. serpentis, C. muris, and C. andersoni. Giardia sp. was not detected in any of the caribou samples nor was Cryptosporidium sp. or Giardia sp. detected in any of the 42 moose (Alces alces) samples examined.     

Classification of Brucella spp. isolated from marine mammals by DNA polymorphism at the omp2 locus

A number of recent reports have described the isolation and characterization of Brucella strains from a wide variety of marine mammals such as seals, porpoises, dolphins and a minke whale. These strains were identified as brucellae by conventional typing tests. However, their overall characteristics were not assimilable to those of any of the six currently recognized Brucella species and it was suggested that they comprise a new nomen species to be called Brucella maris. In the present study we analysed DNA polymorphism at the omp2 locus of 33 marine mammal Brucella strains isolated from seals, dolphins, porpoises and an otter. The omp2 locus contains two gene copies (named omp2a and omp2b) coding for porin proteins and has been found particularly useful for molecular typing and identification of Brucella at the species, biovar, or strain level. PCR-restriction fragment length polymorphism (RFLP) and DNA sequencing showed that strains isolated from dolphins and porpoises carry two omp2b gene copies instead of one omp2a and one omp2b gene copy or two similar omp2a gene copies reported in the currently recognized species. This observation was also recently made for a minke whale Brucella isolate. The otter and all seal isolates except one were shown to carry one omp2a and one omp2b gene copy as encountered in isolates from terrestrial mammals. By PCR-RFLP of the omp2b gene, a specific marker was detected grouping the marine mammal Brucella isolates. Although marine mammal Brucella isolates may represent a separate group from terrestrial mammal isolates based on omp2b sequence constructed phylogenetic trees, the divergence found between their omp2b and also between their omp2a nucleotide sequences indicates that they form a more heterogeneous group than isolates from terrestrial mammals. Therefore, grouping the marine mammal Brucella isolates into one species Brucella maris seems inappropriate unless the currently recognized Brucella species are grouped. With respect to the current classification of brucellae according to the preferential host, brucellae isolated from such diverse marine mammal species as seals and dolphins could actually comprise more than one species, and at least two new species, B. pinnipediae and B. cetaceae, could be compatible with the classical criteria of host preferentialism and DNA polymorphism at their omp2 locus.     

Novel and canine genotypes of Giardia duodenalis in harbor seals ( Phoca vitulina richardsi)

Feces of harbor seals (Phoca vitulina richardsi) and hybrid glaucous-winged/western gulls (Larus glaucescens / occidentalis) from Washington State's inland marine waters were examined for Giardia and Cryptosporidium spp. to determine if genotypes carried by these wildlife species were the same genotypes that commonly infect humans and domestic animals. Using immunomagnetic separation followed by direct fluorescent antibody detection, Giardia spp. cysts were detected in 42% of seal fecal samples (41/97). Giardia-positive samples came from 90% of the sites (9/10) and the prevalence of positive seal fecal samples differed significantly among study sites. Fecal samples collected from seal haulout sites with over 400 animals were 4.7 times more likely to have Giardia spp. cysts than samples collected at smaller haulout sites. In gulls, a single Giardia sp. cyst was detected in 4% of fecal samples (3/78). Cryptosporidium spp. oocysts were not detected in any of the seals or gulls tested. Sequence analysis of a 398 bp segment of G. duodenalis DNA at the glutamate dehydrogenase locus suggested that 11 isolates originating from seals throughout the region were a novel genotype and 3 isolates obtained from a single site in south Puget Sound were the G. duodenalis canine genotype D. Real-time TaqMan PCR amplification and subsequent sequencing of a 52 bp small subunit ribosomal DNA region from novel harbor seal genotype isolates showed sequence homology to canine genotypes C and D. Sequence analysis of the 52 bp small subunit ribosomal DNA products from the 3 canine genotype isolates from seals produced mixed sequences at could not be evaluated.     

Comparison of primers and optimization of PCR conditions for detection of Cryptosporidium parvum and Giardia lamblia in water.

Eight pairs of published PCR primers were evaluated for the specific detection of Cryptosporidium parvum and Giardia lamblia in water. Detection sensitivities ranged from 1 to 10 oocysts or cysts for purified preparations and 5 to 50 oocysts or cysts for seeded environmental water samples. Maximum sensitivity was achieved with two successive rounds of amplification and hybridization, with oligonucleotide probes detected by chemiluminescence. Primer annealing temperatures and MgCl2 concentrations were optimized, and the specificities of the primer pairs were determined with closely related species. Some of the primers were species specific, while others were only genus specific. Multiplex PCR for the simultaneous detection of Cryptosporidium and Giardia was demonstrated with primers amplifying 256- and 163-bp products from the 18S rRNA gene of Cryptosporidium and the heat shock protein gene of Giardia, respectively. The results demonstrate the potential utility of PCR for the detection of pathogenic protozoa in water but emphasize the necessity of continued development.     

Occurrence of Cryptosporidium and Giardia in wild ducks along the Rio Grande River valley in southern New Mexico.

Fecal samples were taken from wild ducks on the lower Rio Grande River around Las Cruces, N. Mex., from September 2000 to January 2001. Giardia cysts and Cryptosporidium oocysts were purified from 69 samples by sucrose enrichment followed by cesium chloride (CsCl) gradient centrifugation and were viewed via fluorescent-antibody (FA) staining. For some samples, recovered cysts and oocysts were further screened via PCR to determine the presence of Giardia lamblia and Crytosporidium parvum. The results of this study indicate that 49% of the ducks were carriers of Cryptosporidium, and the Cryptosporidium oocyst concentrations ranged from 0 to 2,182 oocysts per g of feces (mean +/- standard deviation, 47.53 +/- 270.3 oocysts per g); also, 28% of the ducks were positive for Giardia, and the Giardia cyst concentrations ranged from 0 to 29,293 cysts per g of feces (mean +/- standard deviation, 436 +/- 3,525.4 cysts per g). Of the 69 samples, only 14 had (oo)cyst concentrations that were above the PCR detection limit. Samples did test positive for Cryptosporidium sp. However, C. parvum and G. lamblia were not detected in any of the 14 samples tested by PCR. Ducks on their southern migration through southern New Mexico were positive for Cryptosporidium and Giardia as determined by FA staining, but C. parvum and G. lamblia were not detected.     

Giardia and Cryptosporidium in mammalian wildlife--current status and future needs

Environmental pollution with human and domestic-animal fecal material is recognized as a potential pathogen pathway for wildlife infections with zooanthropomorphic protozoan parasites such as Giardia and Cryptosporidium. In this article, we review current knowledge about the diversity of free-living and captive terrestrial and marine mammalian wildlife species infected with Giardia and Cryptosporidium. The combination of prevalence studies with modern molecular-genotyping techniques is providing valuable insights into the host specificity and possible transmission routes of these two important parasites.     

Serum biochemistry, serology, and parasitology of boreal caribou (Rangifer tarandus caribou) in the Northwest Territories, Canada

Boreal caribou (Rangifer tarandus caribou) are an ecologically and culturally important wildlife species and now range almost exclusively in the boreal forests of Canada, including the Northwest Territories, northern Alberta, and British Columbia. Boreal caribou are threatened throughout their Canadian range because of direct and indirect natural and anthropogenic factors. In the Northwest Territories, however, they have a continuous range that overall has not yet been subjected to the same degree of anthropogenic habitat fragmentation and degradation that has occurred elsewhere in Canada. To monitor the health of boreal caribou populations and individuals, we collected blood from 104 adult, female boreal caribou captured between March 2003 and February 2006 and measured serum biochemical parameters. Serum creatinine was higher in pregnant than in nonpregnant caribou. Several biochemical parameters differed among years, but they tended to be similar to those reported for reindeer. Serum antibodies were found to an alphaherpesvirus, Toxoplasma gondii, and to the Mycobacterium avium subspecies paratuberculosis in 37.5, 2.9, and 1.3% of boreal caribou, respectively. Fecal samples were collected from 149 boreal caribou, and Cryptosporidium sp. oocysts, Giardia sp. cysts, trichostrongyle ova, dorsal-spined nematode larvae, cestode ova, and Eimeria sp. were found. Trypanosoma sp. was detected in the blood of 72.1% of boreal caribou. Eimeria sp., Cryptosporidium sp., and Giardia sp. have not been previously reported in boreal caribou.     

Isolation and characterization of a Helicobacter sp. from the gastric mucosa of dolphins, Lagenorhynchus acutus and Delphinus delphis

Gastric ulcerations in dolphins have been reported for decades. Some of these lesions were associated with parasitic infections. However, cases of nonparasitic gastric ulcers with no clearly defined etiology also have been reported in wild and captive dolphins. Considerable speculation exists as to whether dolphins have Helicobacter-associated gastritis and peptic ulcer disease. The stomachs of seven stranded Atlantic white-sided dolphins, Lagenorhynchus acutus, and 1 common dolphin, Delphinus delphis, were assessed for the presence of Helicobacter species. Novel Helicobacter species were identified by culture in the gastric mucosa of two of the eight dolphins studied and by PCR in seven of the eight dolphins. The gram-negative organisms were urease, catalase, and oxidase positive. Spiral to fusiform bacteria were detected in gastric mucosa by Warthin Starry staining. Histopathology revealed mild to moderate diffuse lymphoplasmacytic gastritis within the superficial mucosa of the main stomach. The pyloric stomach was less inflamed, and bacteria did not extend deep into the glands. The lesions parallel those observed in Helicobacter pylori-infected humans. Bacteria from two dolphins classified by 16S rRNA analysis clustered with gastric helicobacters and represent a novel Helicobacter sp. most closely related to H. pylori. These findings suggest that a novel Helicobacter sp. may play a role in the etiopathogenesis of gastritis and gastric ulcers in dolphins. To our knowledge this represents the first isolation and characterization of a novel Helicobacter sp. from a marine mammal and emphasizes the wide host distribution and pathogenic potential of this increasingly important genus.     

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)     

Morphologic, host specificity, and molecular characterization of a Hungarian Cryptosporidium meleagridis isolate

This study was undertaken in order to characterize Cryptosporidium meleagridis isolated from a turkey in Hungary and to compare the morphologies, host specificities, organ locations, and small-subunit RNA (SSU rRNA) gene sequences of this organism and other Cryptosporidium species. The phenotypic differences between C. meleagridis and Cryptosporidium parvum Hungarian calf isolate (zoonotic genotype) oocysts were small, although they were statistically significant. Oocysts of C. meleagridis were successfully passaged in turkeys and were transmitted from turkeys to immunosuppressed mice and from mice to chickens. The location of C. meleagridis was the small intestine, like the location of C. parvum. A comparison of sequence data for the variable region of the SSU rRNA gene of C. meleagridis isolated from turkeys with other Cryptosporidium sequence data in the GenBank database revealed that the Hungarian C. meleagridis sequence is identical to a C. meleagridis sequence recently described for a North Carolina isolate. Thus, C. meleagridis is a distinct species that occurs worldwide and has a broad host range, like the C. parvum zoonotic strain (also called the calf or bovine strain) and Cryptosporidium felis. Because birds are susceptible to C. meleagridis and to some zoonotic strains of C. parvum, these animals may play an active role in contamination of surface waters not only with Cryptosporidium baileyi but also with C. parvum-like parasites.     

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.