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.

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.

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.

The effect of blueberry extracts on Giardia duodenalis viability and spontaneous excystation of Cryptosporidium parvum oocysts, in vitro

Methods ◽  
2007 ◽  
Vol 42 (4) ◽  
pp. 339-348 ◽  
Author(s):  
J.-P. Anthony ◽  
L. Fyfe ◽  
D. Stewart ◽  
G.J. McDougall ◽  
H.V. Smith
Keyword(s):  
Cryptosporidium Parvum ◽  
Giardia Duodenalis ◽  
Cryptosporidium Parvum Oocysts

scholarly journals Efficacy of Two Peroxygen-Based Disinfectants for Inactivation of Cryptosporidium parvum Oocysts

2005 ◽  
Vol 71 (5) ◽  
pp. 2479-2483 ◽  
Author(s):  
Joaquin Quilez ◽  
Caridad Sanchez-Acedo ◽  
Catalina Avendaño ◽  
Emilio del Cacho ◽  
Fernando Lopez-Bernad
Keyword(s):  
Cryptosporidium Parvum ◽  
Deleterious Effect ◽  
In Vitro Assays ◽  
Infectivity Assay ◽  
Vital Dyes ◽  
Vital Dye ◽  
Potential Efficacy ◽  
Infected Goat ◽  
Cryptosporidium Parvum Oocysts

ABSTRACT Two commercial peroxygen-based disinfectants containing hydrogen peroxide plus either peracetic acid (Ox-Virin) or silver nitrate (Ox-Agua) were tested for their ability to inactivate Cryptosporidium parvum oocysts. Oocysts were obtained from naturally infected goat kids and exposed to concentrations of 2, 5, and 10% Ox-Virin or 1, 3, and 5% Ox-Agua for 30, 60, and 120 min. In vitro excystation, vital dyes (4′,6′-diamidino-2-phenylindole and propidium iodide), and infectivity in neonatal BALB/c mice were used to assess the viability and infectivity of control and disinfectant-treated oocysts. Both disinfectants had a deleterious effect on the survival of C. parvum oocysts, since disinfection significantly reduced and in some cases eliminated their viability and infectivity. When in vitro assays were compared with an infectivity assay as indicators of oocyst inactivation, the excystation assay showed 98.6% inactivation after treatment with 10% Ox-Virin for 60 min, while the vital-dye assay showed 95.2% inactivation and the infectivity assay revealed 100% inactivation. Treatment with 3% Ox-Agua for 30 min completely eliminated oocyst infectivity for mice, although we were able to observe only 74.7% inactivation as measured by excystation assays and 24.3% with vital dyes (which proved to be the least reliable method for predicting C. parvum oocyst viability). These findings indicate the potential efficacy of both disinfectants for C. parvum oocysts in agricultural settings where soil, housing, or tools might be contaminated and support the argument that in comparison to the animal infectivity assay, vital-dye and excystation methods overestimate the viability of oocysts following chemical disinfection.

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.

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