Effects of ozonation and chlorination on viability and infectivity of Cryptosporidium parvum oocysts

2000 ◽  
Vol 41 (7) ◽  
pp. 39-46 ◽  
Author(s):  
T. Hirata ◽  
D. Chikuma ◽  
A. Shimura ◽  
A. Hashimoto ◽  
N. Motoyama ◽  
...  
Keyword(s):  
Cryptosporidium Parvum ◽  
Experimental Studies ◽  
Free Chlorine ◽  
Log Reduction ◽  
Cryptosporidium Parvum Oocysts ◽  
Permeability Assay

Experimental studies on ozonation and chlorination were conducted to determine capacity for inactivating Cryptosporidium parvum oocysts in batch modes at pH 7, 20°C. In both experiments, the log reduction of animal infectivity was linear and clearly decreased as disinfectant CT product increased. However, the curve of reduction in viability determined by both in vitro excystation assay and DAPI/PI permeability assay exhibited a shoulder. The CT products of ozone per 1 log reduction in infectivity were 3 mg middot min/L for 0.5 mg/L and 1.5 mg · min/L for 0.3 mg/L, while viability determined by in vitro excystation was reduced by only 0.2 logs for the CT product of 3 mg · min/L. In the chlorination experiment, thereduction of animal infectivity was up to 3 logs for the CT product of 2,700 mg middot; min/L, while reduction of viability was smaller at 0.16 logs in in vitro excystation and 0.04 logs in DAPI/PI permeability (in PI exclusion) for the same CT product. The CT product of free chlorine per 1 log reduction in infectivity was estimated to be in the range of 800 to 900 mg · min/L.

Development of ATP assay as a surrogate indicator of viability of Cryptosporidium parvum oocysts

2000 ◽  
Vol 41 (7) ◽  
pp. 181-188 ◽  
Author(s):  
I. Somiya ◽  
S. Fujii ◽  
N. Kishimoto ◽  
R-H. Kim
Keyword(s):  
Linear Relationship ◽  
Cryptosporidium Parvum ◽  
Simple Procedure ◽  
Ozone Treatment ◽  
Atp Assay ◽  
Cryptosporidium Oocysts ◽  
Batch Condition ◽  
Cryptosporidium Parvum Oocysts ◽  
Permeability Assay

Adenosine Triphosphate (ATP) determination was applied to evaluate viability of Cryptosporidium oocysts. Three pretreatment methods, such as incubation in acidified Hanks balanced salt solution (HBSS), excystation and sonication were investigated for ATP extraction from oocysts. Incubation in acidified HBSS was insufficient to extract ATP from oocysts, but a linear relationship between the number of oocysts and the concentration of ATP extracted was observed in the test of excystation and sonication treatments. Sonicationtreatment was able to extract ATP from oocysts more rapidly and precisely than excystation treatment. ATP amount per oocyst by sonication treatment (ATPs) was evaluated to be 2.9×10–8 μg on average, andits detection limit was 500 oocysts/100 μl. Ozone treatment experiments were conducted in batch condition to evaluate differences among ATP concentrations extracted, in vitro excystation and DAPI/PI permeability assays. ATPs assay was observed to have a linear relationship with DAPI/PI permeability assay (R2=0.98). As a result, ATP assay is applicable as a surrogate indicator of the viability of C. parvum, and is superior to in vitro excystation and DAPI/PI permeability assay, because of its rapid, accurate and simple procedure.

Inactivation of Cryptosporidium spp. oocysts with ozone and ultraviolet irradiation evaluated by in vitro excystation and animal infectivity

2000 ◽  
Vol 41 (7) ◽  
pp. 119-125 ◽  
Author(s):  
Y. Kanjo ◽  
I. Kimata ◽  
M. Iseki ◽  
S. Miyanaga ◽  
H. Okada ◽  
...  
Keyword(s):  
Cryptosporidium Parvum ◽  
Room Temperature ◽  
Ozone Exposure ◽  
Batch Reactors ◽  
Log Reduction ◽  
Disinfection Methods ◽  
Cryptosporidium Parvum Oocysts ◽  
Uv Lamp ◽  
Infectivity Test

Cryptosporidium parvum and Cryptosporidium muris oocysts were exposed to ozone and/or ultraviolet(UV) lamp in bench-scale batch reactors. The effect of ozone, UV, and sequential disinfection method on two kinds of oocysts were determined with in vitro excystation and animal infectivity test. The results of ozone exposure experiments showed that the required Ct values were about 3 and 8 mg · min./L for 2-log and 3-log reduction ininfectivity of C. parvum oocysts at room temperature, respectively. But larger values of Ct were needed at low temperature. In the case of sequential disinfection methods with ozone and UV, more than 1-log reduction in infectivity was achieved with 15 sec. of UV irradiation. There was no significant correlation between the excystation ratios and the reduction ratios in infectivity. Moreover, the results of dose-response of animal infectivity test indicated the possibility of a new method to evaluate the infectivity of Cryptosporidium parvum oocysts.

Survival ofCryptosporidium parvumoocysts in source separated human urine

1999 ◽  
Vol 45 (9) ◽  
pp. 740-746 ◽  
Author(s):  
Caroline E Höglund ◽  
Thor Axel B Stenström
Keyword(s):  
Cryptosporidium Parvum ◽  
Human Urine ◽  
Ph Effects ◽  
Primary Methods ◽  
Dye Permeability ◽  
Cryptosporidium Parvum Oocysts ◽  
Microbial Risks ◽  
Permeability Assay ◽  
Made In

The survival of Cryptosporidium parvum in source separated urine was investigated as part of a broader study on microbial risks associated with the reuse of human urine for sustainable agriculture. A dye permeability assay and in vitro excystation were the primary methods used to assess viability. In the collected urine most of the nitrogen is present as ammonia and the pH is generally around 9. Parallel investigations were made in buffers to compare possible toxic effects of urine to actual pH effects. Oocysts in the untreated urine were inactivated below the detection limit (1/300) within 63 days. This inactivation rate was significantly higher (P < 0.01) than in urine adjusted to pH 5 or 7 according to the dye permeability assay. The corresponding difference between different pH values was not seen in buffers, suggesting that the antiprotozoan effect of urine was mediated by other factors besides pH. The Swedish practice of storing urine for six months before its use thus appears satisfactory for the inactivation of Cryptosporidium oocysts.Key words: Cryptosporidium parvum, oocysts, human urine, survival, source separation.

Aging of Cryptosporidium parvum oocysts in river water and their susceptibility to disinfection by chlorine and monochloramine

1998 ◽  
Vol 44 (12) ◽  
pp. 1154-1160 ◽  
Author(s):  
Christian Chauret ◽  
Kerry Nolan ◽  
Ping Chen ◽  
Susan Springthorpe ◽  
Syed Sattar
Keyword(s):  
Cryptosporidium Parvum ◽  
Environmental Fate ◽  
Water Environment ◽  
Water Disinfection ◽  
Ottawa River ◽  
In Situ Conditions ◽  
Cryptosporidium Parvum Oocysts ◽  
St Lawrence River

Cryptosporidium parvum oocysts were aged in waters from both the St. Lawrence River and the Ottawa River. In situ survival experiments were carried out by incubating the oocysts in either dialysis cassettes or microtubes floated into an overflow tank. A significant portion of the oocysts survived in the test waters for several weeks. Oocyst survival in the St. Lawrence River was better in membrane-filtered (0.2-µm-pore diameter) water than in unfiltered water, suggesting that biological antagonism may play a role in the environmental fate of the parasite. Oocysts aged in river waters under in situ conditions and control oocysts kept refrigerated in synthetic water (100 ppm as CaCO3; pH 7.0) were subjected to the same disinfection protocol. Aged oocysts were at least as resistant as, if not more resistant than, the control oocysts to disinfection. This indicates that the oocysts surviving in the water environment may be just as difficult to inactivate by potable water disinfection as freshly shed oocysts. Therefore, water treatment should not be based on the assumption that environmental oocysts may be more easily inactivated than freshly shed oocysts. First-order kinetics die-off rates varied from one river to another (from 0.013 to 0.039 log10·day-1) and from one experiment to another with water from the same river collected at different times. Calculation of the die-off rates based on either in vitro excystation or in vitro excystation in combination with total counts (overall die-off rates) showed that the assessment of oocyst viability by microscopic methods must account for the total oocyst loss observed during long-term inactivation assays of river waters.Key words: Cryptosporidium, survival, disinfection, biological antagonism.

scholarly journals Assessment of a dye permeability assay for determination of inactivation rates of Cryptosporidium parvum oocysts.

1997 ◽  
Vol 63 (10) ◽  
pp. 3844-3850 ◽  
Author(s):  
M B Jenkins ◽  
L J Anguish ◽  
D D Bowman ◽  
M J Walker ◽  
W C Ghiorse
Keyword(s):  
Cryptosporidium Parvum ◽  
Dye Permeability ◽  
Cryptosporidium Parvum Oocysts ◽  
Permeability Assay

scholarly journals Inactivation of Cryptosporidium parvumOocysts by Ammonia

1998 ◽  
Vol 64 (2) ◽  
pp. 784-788 ◽  
Author(s):  
Michael B. Jenkins ◽  
Dwight D. Bowman ◽  
William C. Ghiorse
Keyword(s):  
Cryptosporidium Parvum ◽  
Continuous Flow ◽  
Free Ammonia ◽  
Infected Calf ◽  
Alkaline Ph ◽  
Wild Type ◽  
Dye Permeability ◽  
Permeability Assay ◽  
Soil And Water

ABSTRACT The survival of Cryptosporidium parvum oocysts in soil and water microhabitats may be affected by the environmental production and release of free ammonia. The objective of this study was to determine the effects of increasing free ammonia concentrations and times of exposure on oocyst viability. Wild-type oocysts were obtained from naturally infected calf feces by chemical (continuous-flow) centrifugation and sucrose gradients. Ammonia (NH3) from a commercial solution was applied in concentrations ranging from 0.007 to 0.148 M. Exposure times ranged from 10 min to 24 h at a constant temperature of 24 ± 1°C. Viability of oocysts was determined with a dye permeability assay and an in vitro excystation assay (M. B. Jenkins, L. J. Anguish, D. D. Bowman, M. J. Walker, and W. C. Ghiorse, Appl. Environ. Microbiol. 63:3844–3850, 1997). Even the lowest concentration of ammonia decreased significantly the viability of oocysts after 24 h of exposure. Increasing concentrations of ammonia increased inactivation rates, which ranged from 0.014 to 0.066 h−1. At the highest concentration of ammonia, a small fraction of viable oocysts still remained. Exposure to pH levels corresponding to those associated with the ammonia concentrations showed minimal effects of alkaline pH alone on oocyst viability. This study shows that environmentally relevant concentrations of free ammonia may significantly increase the inactivation of oocysts in ammonia-containing environments.

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