Occurrence of gastrointestinal protozoa in Didelphis albiventris (opossum) in the central region of Rio Grande do Sul state

The aim of this study was to evaluate the parasitism by gastrointestinal protozoa in Didelphis albiventris (opossum) in the central region of Rio Grande do Sul state. Fecal samples from six free living opossums were collected for research of parasites. Samples were analyzed by the centrifugal-flotation method with zinc sulfate and parasites were identified microscopically based on (oo)cyst size and morphology. Cysts of Giardia sp. and oocysts of Cryptosporidium sp. and Eimeria sp. were observed in four of the six opossums. All four infected marsupials showed mild infection by protozoa. This is the first report of Giardia sp. in D. albiventris.     

The use of a ribosomal RNA targeted oligonucleotide probe for fluorescent labelling of viable Cryptosporidiumparvum oocysts

A fluorescence in situ hybridization (FISH) technique has been developed for the fluorescent labelling of Cryptosporidium parvum oocysts in water samples. The FISH technique employs a fluorescently labelled oligonucleotide probe (Cry1 probe) targeting a specific sequence in the 18S ribosomal RNA (rRNA) of C. parvum. Hybridization with the Cry1 probe resulted in fluorescence of sporozoites within oocysts that were capable of excystation, while oocysts that were dead prior to fixation did not fluoresce. Correlation of the FISH method with viability as measured by in vitro excystation was statistically highly significant, with a calculated correlation coefficient of 0·998. Examination of sequence data for Cryptosporidium spp. other than C. parvum suggests that the Cry1 probe is C. parvum -specific. In addition, 19 isolates of C. parvum were tested, and all fluoresced after hybridization with the Cry1 probe. Conversely, isolates of C. baileyi and C. muris were tested and found not to fluoresce after hybridization with the Cry1 probe. The fluorescence of FISH-stained oocysts was not bright enough to enable detection of oocysts in environmental water concentrates containing autofluorescent algae and mineral particles. However, in combination with immunofluorescence staining, FISH enabled species-specific detection and viability determination of C. parvum oocysts in water samples.     

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.     

Giardia and Cryptosporidium spp. in filtered drinking water supplies.

Giardia and Cryptosporidium levels were determined by using a combined immunofluorescence test for filtered drinking water samples collected from 66 surface water treatment plants in 14 states and 1 Canadian province. Giardia cysts were detected in 17% of the 83 filtered water effluents. Cryptosporidium oocysts, were observed in 27% of the drinking water samples. Overall, cysts or oocysts were found in 39% of the treated effluent samples. Despite the frequent detection of parasites in drinking water, microscopic observations of the cysts and oocysts suggested that most of the organisms were nonviable. Compliance with the filtration criteria outlined by the Surface Water Treatment Rule of the U.S. Environmental Protection Agency did not ensure that treated water was free of cysts and oocysts. The average plant effluent turbidity for sites which were parasite positive was 0.19 nephelometric turbidity units. Of sites that were positive for Giardia or Cryptosporidium spp., 78% would have been able to meet the turbidity regulations of the Surface Water Temperature Rule. Evaluation of the data by using a risk assessment model developed for Giardia spp. showed that 24% of the utilities examined would not meet a 1/10,000 annual risk of Giardia infection. For cold water conditions (0.5 degree C), 46% of the plants would not achieve the 1/10,000 risk level.     

Giardia and Cryptosporidium spp. in filtered drinking water supplies.

Giardia and Cryptosporidium levels were determined by using a combined immunofluorescence test for filtered drinking water samples collected from 66 surface water treatment plants in 14 states and 1 Canadian province. Giardia cysts were detected in 17% of the 83 filtered water effluents. Cryptosporidium oocysts, were observed in 27% of the drinking water samples. Overall, cysts or oocysts were found in 39% of the treated effluent samples. Despite the frequent detection of parasites in drinking water, microscopic observations of the cysts and oocysts suggested that most of the organisms were nonviable. Compliance with the filtration criteria outlined by the Surface Water Treatment Rule of the U.S. Environmental Protection Agency did not ensure that treated water was free of cysts and oocysts. The average plant effluent turbidity for sites which were parasite positive was 0.19 nephelometric turbidity units. Of sites that were positive for Giardia or Cryptosporidium spp., 78% would have been able to meet the turbidity regulations of the Surface Water Temperature Rule. Evaluation of the data by using a risk assessment model developed for Giardia spp. showed that 24% of the utilities examined would not meet a 1/10,000 annual risk of Giardia infection. For cold water conditions (0.5 degree C), 46% of the plants would not achieve the 1/10,000 risk level.     

Host adaptation and host-parasite co-evolution in Cryptosporidium: implications for taxonomy and public health

To assess the genetic diversity and evolution of Cryptosporidium parasites, the partial ssrRNA, actin, and 70 kDa heat shock protein (HSP70) genes of 15 new Cryptosporidium parasites were sequenced. Sequence data were analysed together with those previously obtained from other Cryptosporidium parasites (10 Cryptosporidium spp. and eight Cryptosporidium genotypes). Results of this multi-locus genetic characterisation indicate that host adaptation is a general phenomenon in the genus Cryptosporidium, because specific genotypes were usually associated with specific groups of animals. On the other hand, host–parasite co-evolution is also common in Cryptosporidium, as closely related hosts usually had related Cryptosporidium parasites. Results of phylogenetic analyses suggest that the Cryptosporidium parvum bovine genotype and Cryptosporidium meleagridis were originally parasites of rodents and mammals, respectively, but have subsequently expanded their host ranges to include humans. Understanding the evolution of Cryptosporidium species is important not only for clarification of the taxonomy of the parasites but also for assessment of the public health significance of Cryptosporidium parasites from animals.     

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.     

Evaluation of the immunofluorescence procedure for detection of Giardia cysts and Cryptosporidium oocysts in water.

The accurate determination of the presence of Giardia cysts and Cryptosporidium oocysts in surface waters requires a reliable method for the detection and enumeration of these pathogenic organisms. Published methods have usually reported recovery efficiencies of less than 50% for both cysts and oocysts. Typically, the losses are greater for Cryptosporidium oocysts than they are for Giardia cysts. The purpose of this study was to examine procedures used for sample collection, elution, concentration, and clarification to determine when losses of cysts and oocysts occurred during processing. The results showed that major losses of cysts and oocysts occurred during centrifugation and clarification. Depending on the centrifugation force, oocyst losses of as high as 30% occurred for each centrifugation step. A 1.15-specific-gravity Percoll-sucrose gradient was needed to optimize recovery of oocysts from natural water samples. Minor improvements in the procedure could be accomplished by selecting a filter other than the recommended 1-micron-pore-size (nominal-porosity) polypropylene filter.     

Prevalence of and associated risk factors for shedding Cryptosporidium parvum oocysts and Giardia cysts within feral pig populations in California.

Populations of feral pigs (Sus scrofa) may serve as an environmental reservoir of Cryptosporidium parvum oocysts and Giardia sp. cysts for source water. We conducted a cross-sectional study to determine the prevalence of and associated demographic and environmental risk factors for the shedding of C. parvum oocysts and Giardia sp. cysts. Feral pigs were either live-trapped or dispatched from 10 populations located along the coastal mountains of western California, and fecal samples were obtained for immunofluorescence detection of C. parvum oocysts and Giardia sp. cysts. We found that 12 (5.4%) and 17 (7.6%) of 221 feral pigs were shedding C. parvum oocysts and Giardia sp. cysts, respectively. The pig's sex and body condition and the presence of cattle were not associated with the probability of the shedding of C. parvum oocysts. However, younger pigs (< or = 8 months) and pigs from high-density populations (> 2.0 feral pigs/km2) were significantly more likely to shed oocysts compared to older pigs (> 8 months) and pigs from low-density populations (< or = 1.9 feral pigs/km2). In contrast, none of these demographic and environmental variables were associated with the probability of the shedding of Giardia sp. cysts among feral pigs. These results suggest that given the propensity for feral pigs to focus their activity in riparian areas, feral pigs may serve as a source of protozoal contamination for surface water.     

Prevalence and genotyping of human isolates of Giardia duodenalis from Albania

Microscopical and PCR-based techniques were performed in order to investigate the prevalence of infection and the genotypes of Giardia duodenalis from 125 stool samples collected from children living in the urban and the rural areas of Tirana (Albania) and hospitalized with acute gastroenteritis. 7 out of 125 samples resulted positive for Giardia at the microscopic examination (5.6%). In 50 selected samples including the 7 samples positive for Giardia by microscopy, 3 and 15 additional positive samples were detected by immunofluorescence and PCR, respectively. Seasonality appeared as an important parameter to be evaluated in order to better understand the prevalence of infection. Sequence analysis revealed both human Assemblage A and B. This result represents the first data on G. duodenalis genotypes in Albania.     

Comparison of two methods for detection of Giardia cysts and Cryptosporidium oocysts in water.

The steps of two immunofluorescent-antibody-based detection methods were evaluated for their efficiencies in detecting Giardia cysts and Cryptosporidium oocysts. The two methods evaluated were the American Society for Testing and Materials proposed test method for Giardia cysts and Cryptosporidium oocysts in low-turbidity water and a procedure employing sampling by membrane filtration, Percoll-Percoll step gradient, and immunofluorescent staining. The membrane filter sampling method was characterized by higher recovery rates in all three types of waters tested: raw surface water, partially treated water from a flocculation basin, and filtered water. Cyst and oocyst recovery efficiencies decreased with increasing water turbidity regardless of the method used. Recoveries of seeded Giardia cysts exceeded those of Cryptosporidium oocysts in all types of water sampled. The sampling step in both methods resulted in the highest loss of seeded cysts and oocysts. Furthermore, much higher recovery efficiencies were obtained when the flotation step was avoided. The membrane filter method, using smaller tubes for flotation, was less time-consuming and cheaper. A serious disadvantage of this method was the lack of confirmation of presumptive cysts and oocysts, leaving the potential for false-positive Giardia and Cryptosporidium counts when cross-reacting algae are present in water samples.     

华东三省转Bt基因棉花种植对边际水体中Cry1Ab/c蛋白残留的影响

为调查转基因棉花种植地区边际水体中的Cry1Ab/c蛋白残留情况, 在华东地区的山东、江苏、安徽三省棉田设置采样点, 连续3年在棉花的花铃期和收获季节, 对棉区地块内部及周围边际水体随机采样, 进行去杂及纯化处理后, 利用ELISA (酶联免疫吸附测定)方法检测水样中的Cry1Ab/c蛋白含量。结果表明: (1)在花铃期和收获季前后两周, 分别在5个布控点边际水体中检出Cry1Ab/c蛋白, 其中1个布控点阳性蛋白残留浓度最高达到0.4 ppb, 另外4个布控点检测出的阳性蛋白量均在0.04 ppb以下; (2)距离棉田越近, 蛋白检出阳性率越高, 其中棉田内水渠阳性率为13.3%; (3)连续种植时间超过7年的田地周围水体中蛋白阳性率为12.4%。在所有取样时间点中, 与花铃期相比, 收获季更容易检测到阳性结果。这表明在转基因棉花产区, 应在收获季进行适当的指导和监控, 以预防和降低转基因棉花中Cry1Ab/c蛋白对边际水体的潜在影响。     

Batch solar disinfection inactivates oocysts of Cryptosporidium parvum and cysts of Giardia muris in drinking water

AIM: To determine whether batch solar disinfection (SODIS) can be used to inactivate oocysts of Cryptosporidium parvum and cysts of Giardia muris in experimentally contaminated water. METHODS AND RESULTS: Suspensions of oocysts and cysts were exposed to simulated global solar irradiation of 830 W m(-2) for different exposure times at a constant temperature of 40 degrees C. Infectivity tests were carried out using CD-1 suckling mice in the Cryptosporidium experiments and newly weaned CD-1 mice in the Giardia experiments. Exposure times of > or =10 h (total optical dose c. 30 kJ) rendered C. parvum oocysts noninfective. Giardia muris cysts were rendered completely noninfective within 4 h (total optical dose >12 kJ). Scanning electron microscopy and viability (4',6-diamidino-2-phenylindole/propidium iodide fluorogenic dyes and excystation) studies on oocysts of C. parvum suggest that inactivation is caused by damage to the oocyst wall. CONCLUSIONS: Results show that cysts of G. muris and oocysts of C. parvum are rendered completely noninfective after batch SODIS exposures of 4 and 10 h (respectively) and is also likely to be effective against waterborne cysts of Giardia lamblia. SIGNIFICANCE AND IMPACT OF THE STUDY: These results demonstrate that SODIS is an appropriate household water treatment technology for use as an emergency intervention in aftermath of natural or man-made disasters against not only bacterial but also protozoan pathogens.     

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.     

Evaluation of five membrane filtration methods for recovery of Cryptosporidium and Giardia isolates from water samples

We evaluated the efficiency of five membrane filters for recovery of Cryptosporidium parvum oocysts and Giardia lamblia cysts. These filters included the Pall Life Sciences Envirochek (EC) standard filtration and Envirochek high-volume (EC-HV) membrane filters, the Millipore flatbed membrane filter, the Sartorius flatbed membrane filter (SMF), and the Filta-Max (FM) depth filter. Distilled and surface water samples were spiked with 10 oocysts and 10 cysts/liter. We also evaluated the recovery efficiency of the EC and EC-HV filters after a 5-s backwash postfiltration. The backwashing was not applied to the other filtration methods because of the design of the filters. Oocysts and cysts were visualized by using a fluorescent monoclonal antibody staining technique. For distilled water, the highest percent recovery for both the oocysts and cysts was obtained with the FM depth filter. However, when a 5-s backwash was applied, the EC-HV membrane filter (EC-HV-R) was superior to other filters for recovery of both oocysts (n = 53 +/- 15.4 per 10 liters) and cysts (n = 59 +/- 11.5 per 10 liters). This was followed by results of the FM depth filter (oocysts, 28.2 +/- 8, P = 0.015; cysts, 49.8 +/- 12.2, P = 0.4260), and SMF (oocysts, 16.2 +/- 2.8, P = 0.0079; cysts, 35.2 +/- 3, P = 0.0079). Similar results were obtained with surface water samples. Giardia cysts were recovered at higher rates than were Cryptosporidium oocysts with all five filters, regardless of backwashing. Although the time differences for completion of filtration process were not significantly different among the procedures, the EC-HV filtration with 5-s backwash was less labor demanding.     

Giardia cysts and Cryptosporidium oocysts detection in the intake and rapid filter system in a water purification plant

Water samples, taken from the intake and rapid filter system of a water purification plant, were analyzed using an immunofluorescence antibody method for detecting the presence of Giardia cysts and Cryptosporidium oocysts. Giardia cysts and Cryptosporidium oocysts were found in the intake water from zero to 38.7 cysts/100 l and 1.7–50.5 oocysts/100 l with averages of 9.6 cysts/100 l and 19.4 oocysts/100 l. Giardia cysts and Cryptosporidium oocysts were also detected in the samples taken from the rapid filtration unit with mean concentrations of zero to 2.3 cysts/100 l and 0–2.5 oocysts/100 l, respectively. The efficacy of the rapid filter in suspended material and (oo)cyst removal was significant. The removal late was 56–97% for suspended material and 69–100% for the (oo)cysts.     

Improvement of recoveries for the determination of protozoa Cryptosporidium and Giardia in water using method 1623

The U.S. Environmental Protection Agency has developed method 1623 for simultaneous detection of Cryptosporidium oocysts and Giardia cysts in water. Method 1623 includes four major steps: filtration, immunomagnetic separation (IMS), fluorescent antibody (FA) staining and microscopic examination. It was noted that the recovery levels following IMS-FA and FA staining were high, averaging more than 92.0% and 89.0% for C. parvum oocysts and G. lamblia cysts, respectively. In contrast, when the filtration step was incorporated, the recovery level of C. parvum oocysts declined significantly to 18.1% in seeded tap water, while a relatively high recovery level of 77.2% for G. lamblia cysts could still be achieved. Further study indicated that the recovery level of C. parvum oocysts could be enhanced significantly when an appropriate amount of silica particles was added to a water sample. The recovery level of C. parvum oocysts was affected by particle size and concentration. The optimal silica particle size was determined to be within the range of 5-40 microm, and the corresponding optimal silica concentration was 1.42 g for 10-l tap water. When both G. lamblia cysts and C. parvum oocysts were spiked into the tap water sample containing the optimum amount of silica particles, the average recovery levels of oocysts and cysts were 82.7% and 75.4%, respectively. The results obtained clearly suggested that addition of an appropriate amount of silica particles could improve the recovery level of C. parvum oocysts significantly and yet there was no noticeable deleterious effect on the recovery level of G. lamblia cysts. Further study indicated that the rotation time in the IMS procedure using the Dynal GC-Combo IMS kit (which was recommended in method 1623) was important for G. lamblia cyst detection. In contrast, the recovery level of C. parvum oocysts was not affected by the rotation time. Furthermore, it was found that the recovery levels of C. parvum oocysts using methods 1622 and 1623 were quite close although different IMS kits were used in the two methods.     

Occurrence of Cryptosporidium and Giardia genotypes and subtypes in raw and treated water in Portugal

Aims:  Waterborne outbreaks of diarrhoeal illness reported worldwide are mostly associated with Cryptosporidium spp. and Giardia spp. Their presence in aquatic systems makes it essential to develop preventive strategies for water and food safety. This study was undertaken to monitor the presence of Cryptosporidium and Giardia in a total of 175 water samples, including raw and treated water from both surface and ground sources in Portugal.
Methods and Results:  The samples were processed according to USEPA Method 1623 for immunomagnetic separation (IMS) of Cryptosporidium oocysts and Giardia cysts, followed by detection of oocysts/cysts by immunofluorecence (IFA) microscopy, PCR-based techniques were done on all water samples collected. Out of 175 samples, 81 (46·3%) were positive for Cryptosporidium and 67 (38·3%) for Giardia by IFA. Cryptosporidium spp. and G. duodenalis genotypes were identified by PCR in 37 (21·7%) and 9 (5·1%) water samples, respectively. C. parvum was the most common species (78·9%), followed by C. hominis (13·2%), C. andersoni (5·3%), and C. muris (2·6%). Subtype IdA15 was identified in all C. hominis -positive water samples. S ubtyping revealed the presence of C. parvum subtypes IIaA15G2R1, IIaA16G2R1 and IIdA17G1. Giardia duodenalis subtype A1 was identified.
Conclusions:  The results of the present study suggest that Cryptosporidium spp. and Giardia spp. were widely distributed in source water and treated water in Portugal. Moreover, the results obtained indicate a high occurrence of human-pathogenic Cryptosporidium genotypes and subtypes in raw and treated water samples.
Significance and Impact of the Study:  Thus, water can be a potential vehicle in the transmission of cryptosporidiosis, and giardiasis of humans and animals in Portugal.     

Species-specific, nested PCR-restriction fragment length polymorphism detection of single Cryptosporidium parvum oocysts

Concurrent with recent advances seen with Cryptosporidium parvum detection in both treated and untreated water is the need to properly evaluate these advances. A micromanipulation method by which known numbers of C. parvum oocysts, even a single oocyst, can be delivered to a test matrix for detection sensitivity is presented. Using newly developed nested PCR-restriction fragment length polymorphism primers, PCR sensitivity was evaluated with 1, 2, 3, 4, 5, 7, or 10 oocysts. PCR detection rates (50 samples for each number of oocysts) ranged from 38% for single oocysts to 92% for 5 oocysts, while 10 oocysts were needed to achieve 100% detection. The nested PCR conditions amplified products from C. parvum, Cryptosporidium baileyi, and Cryptosporidium serpentis but no other Cryptosporidium sp. or protozoan tested. Restriction enzyme digestion with VspI distinguished between C. parvum genotypes 1 and 2. Restriction enzyme digestion with DraII distinguished C. parvum from C. baileyi and C. serpentis. Use of known numbers of whole oocysts encompasses the difficulty of liberating DNA from the oocyst and eliminates the standard deviation inherent within a dilution series. To our knowledge this is the first report in which singly isolated C. parvum oocysts were used to evaluate PCR sensitivity. This achievement illustrates that PCR amplification of a single oocyst is feasible, yet sensitivity remains an issue, thereby illustrating the difficulty of dealing with low oocyst numbers when working with environmental water samples.     

Evaluation of Five Membrane Filtration Methods for Recovery of Cryptosporidium and Giardia Isolates from Water Samples

We evaluated the efficiency of five membrane filters for recovery of Cryptosporidium parvum oocysts and Giardia lamblia cysts. These filters included the Pall Life Sciences Envirochek (EC) standard filtration and Envirochek high-volume (EC-HV) membrane filters, the Millipore flatbed membrane filter, the Sartorius flatbed membrane filter (SMF), and the Filta-Max (FM) depth filter. Distilled and surface water samples were spiked with 10 oocysts and 10 cysts/liter. We also evaluated the recovery efficiency of the EC and EC-HV filters after a 5-s backwash postfiltration. The backwashing was not applied to the other filtration methods because of the design of the filters. Oocysts and cysts were visualized by using a fluorescent monoclonal antibody staining technique. For distilled water, the highest percent recovery for both the oocysts and cysts was obtained with the FM depth filter. However, when a 5-s backwash was applied, the EC-HV membrane filter (EC-HV-R) was superior to other filters for recovery of both oocysts (n = 53 ± 15.4 per 10 liters) and cysts (n = 59 ± 11.5 per 10 liters). This was followed by results of the FM depth filter (oocysts, 28.2 ± 8, P = 0.015; cysts, 49.8 ± 12.2, P = 0.4260), and SMF (oocysts, 16.2 ± 2.8, P = 0.0079; cysts, 35.2 ± 3, P = 0.0079). Similar results were obtained with surface water samples. Giardia cysts were recovered at higher rates than were Cryptosporidium oocysts with all five filters, regardless of backwashing. Although the time differences for completion of filtration process were not significantly different among the procedures, the EC-HV filtration with 5-s backwash was less labor demanding.