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.

Microwave Inactivation of Cyclospora cayetanensis Sporulation and Viability of Cryptosporidium parvum Oocysts

2006 ◽  
Vol 69 (8) ◽  
pp. 1957-1960 ◽  
Author(s):  
YNES R. ORTEGA ◽  
JYEYIN LIAO
Keyword(s):  
Cryptosporidium Parvum ◽  
Propidium Iodide ◽  
Cryptosporidium Oocyst ◽  
Cooking Time ◽  
Cyclospora Cayetanensis ◽  
The Third ◽  
Infectivity Assay ◽  
Cryptosporidium Oocysts ◽  
Cryptosporidium Parvum Oocysts ◽  
Cooking Times

The efficacy of microwave heating on the viability of Cryptosporidium parvum oocysts and on the sporulation of Cyclospora cayetanensis oocysts for various periods of cooking times (0, 10, 15, 20, 30, and 45 s) at 100% power was determined. Cyclospora oocysts were stored in 2.5% dichromate at 23°C for 2 weeks, and sporulation rates were then determined. The 4′,6-diamidino-2-phenylindole and propidium iodide vital stain and the neonate animal infectivity assay determined Cryptosporidium oocyst viability. Cryptosporidium oocysts could be completely inactivated with as little as 20 s of cooking time, whereas Cyclospora sporulation was observed up to 45 s. Two of the examined microwave ovens were more effective at reducing sporulation and viability than the third one. Because of the variability of temperature achieved by the various ovens, cooking time was not an accurate parameter for parasite inactivation. Cryptosporidium oocysts could be inactivated only when temperatures of 80°C or higher were reached in the microwave ovens.

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 Ozone on the Viability of Cryptosporidium parvum Oocysts and a Comparison of Experimental Methods

1993 ◽  
Vol 27 (3-4) ◽  
pp. 93-96 ◽  
Author(s):  
J. F. W. Parker ◽  
G. F. Greaves ◽  
H. V. Smith
Keyword(s):  
Cryptosporidium Parvum ◽  
Influencing Factor ◽  
Experimental Methods ◽  
Ozone Treatment ◽  
Vital Dyes ◽  
Experimental Systems ◽  
Increased Temperature ◽  
Constant Dose ◽  
Cryptosporidium Parvum Oocysts

Cryptosporidium parvum oocysts were exposed to ozone using two experimental systems. The first method involved producing residual concentrations of 1, 3 and 5 mg/L of ozone in 500 ml of water in a Drechsel gas bottle, which was then inoculated with oocysts. The second method involved inoculating 7 L of water with oocysts and then applying a constant dose of 1, 3 and 5 mg/L of ozone, circulating the water in a contactor system. Viability was assessed by the inclusion/exclusion of fluorogenic vital dyes. Comparison of these two methods showed that the second method was considerably more successful at reducing oocyst viability than the first method. Experiments performed at an increased temperature using method one indicated that temperature was an influencing factor on oocyst inactivation by ozone treatment.

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

Applications of in-vitro cell culture for measuring infectivity and inactivation of Cryptosporidium parvum

2004 ◽  
Vol 4 (2) ◽  
pp. 87-92
Author(s):  
P.A. Rochelle
Keyword(s):  
Cell Culture ◽  
Cryptosporidium Parvum ◽  
Rt Pcr ◽  
In Vitro Cell Culture ◽  
Infectivity Assay ◽  
Public Health Officials ◽  
Practical Tool ◽  
Cell Culture Assay ◽  
Evaluating Methods

Cryptosporidium parvum presents a significant problem for the water industry and public health officials because of its prevalence in sources of drinking water and its resistance to chlorine-based disinfectants; there is an urgent need for alternative, more effective disinfection strategies. Therefore, developing and evaluating methods for assessing the infectivity and inactivation of C. parvum oocysts are of paramount importance. Infectivity assays based on in-vitro cell culture have been developed as alternatives to human and animal-based assays to overcome ethical, cost, and practicality issues. Data obtained over a two-year period with an HCT-8 cell culture/RT-PCR infectivity assay generated an ID50 of 99 oocysts (95% CI: 84-117) and demonstrated that the cell culture assay was equivalent to the standard CD-1 mouse model for measuring infectivity of C. parvum oocysts. Aggregate data generated over two years using the HCT-8 cell culture/RT-PCR assay to measure UV disinfection of C. parvum demonstrated that 2.4 mJ/cm2 and 4.9 mJ/cm2 were necessary to achieve 1-log10 and 2-log10 inactivation, respectively. This work demonstrated that an HCT-8 cell culture-based infectivity coupled with RT-PCR for detecting C. parvum infections is a practical tool that can provide valuable information about the efficacy of disinfectants and the infectivity of oocysts in environmental waters.

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.

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