Article

Effect of Cyanuric Acid on the Inactivation of Cryptosporidium parvum under Hyperchlorination Conditions

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Cyanuric acid (CYA) is a chlorine stabilizer used in swimming pools to limit UV degradation of chlorine, thus reducing chlorine use and cost. However, CYA has been shown to decrease the efficacy of chlorine disinfection. In the event of a diarrheal incident, CDC recommends implementing 3-log10 inactivation conditions for Cryptosporidium (CT value = 15 300 mg·min/L) to remediate pools. Currently, CYA's impact on Cryptosporidium inactivation is not fully determined. We investigated the impact of multiple concentrations of CYA on C. parvum inactivation (at 20 and 40 mg/L free chlorine; average pH 7.6; 25 °C). At 20 mg/L free chlorine, average estimated 3-log10 CT values were 17 800 and 31 500 mg·min/L with 8 and 16 mg/L CYA, respectively, and the average estimated 1-log10 CT value was 76 500 mg·min/L with 48 mg/L CYA. At 40 mg/L free chlorine, 3-log10 CT values were lower than those at 20 mg/L, but still higher than those of free chlorine-only controls. In the presence of ∼100 mg/L CYA, average 0.8- and 1.4-log10 reductions were achieved by 72 h at 20 and 40 mg/L free chlorine, respectively. This study demonstrates CYA significantly delays chlorine inactivation of Cryptosporidium oocysts, emphasizing the need for additional pool remediation options following fecal incidents.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Laboratory studies of the effect of CYA on chlorine disinfection rates have been conducted with various microorganisms, including bacteria [6][7][8], protozoa [9,10], viruses [11,12], algae [13], and amoeba [14]. Various reports on the effects of CYA have also been published from field studies [15][16][17]. ...
... For the purposes of this model, it was assumed that HOCl is the only active biocide in chlorinated pool water containing CYA. This assumption was tested by evaluation of inactivation data for a number of microorganisms with particular focus on Streptococcus faecalis [6][7][8] and Cryptosporidium [9]. Additional information on disinfection kinetics is provided in Supplementary Material S5. ...
... The proposition that the primary biocide in chlorine solutions with CYA is HOCl is further supported by the Cryptosporidium data from Murphy [9] (see Figure 4). The ln(P/P0) were adjusted for die-off. ...
Article
Full-text available
Current regulatory codes for swimming pool disinfection separately regulate free chlorine (FC) and cyanuric acid (CYA). It is well-known that CYA affects disinfection rates by reversibly binding to FC in aqueous solutions. However, limits for these regulated parameters have neither systematically accounted for this chemistry nor been based on the risk of gastrointestinal illness. This study was intended to determine the minimum concentration of FC relative to CYA based on the risk of gastrointestinal illness from normal fecal sloughing of selected pathogens and to find a simple regulatory rule for jointly managing FC and CYA for consistent disinfection. Literature data on CYA’s effect on microbial inactivation rates were reanalyzed based on the equilibria governing hypochlorous acid (HOCl) concentration. A model was developed that considers the rates of pathogen introduction into pool water, disinfection, turbulent diffusive transport, and pathogen uptake by swimmers to calculate the associated risk of illness. Model results were compared to U.S. Environmental Protection Agency (EPA) untreated recreational water acceptable gastrointestinal illness risk. For Cryptosporidium, correlation between log inactivation and Chick–Watson Ct was far better when C refers to HOCl concentration than to FC (r = −0.96 vs. −0.06). The HOCl concentration had a small variation (± 1.8%) at a constant CYA/FC ratio for typical FC and CYA ranges in swimming pools. In 27 U.S. states, the allowed FC and CYA results in HOCl concentrations spanning more than a factor of 500. Using conservative values for a high bather load pool with 2 mg/L FC and 90 mg/L CYA, the model predicted a 0.071 annual probability of infection for Giardia, exceeding the EPA regulatory 0.036 limit for untreated recreational waters. FC and CYA concentrations in swimming pools should be jointly regulated as a ratio. We recommend a maximum CYA/FC ratio of 20.
... Another feature of cyanuric acid is the active hydrogen atom, which plays an important role in the formation of Hamilton complexes [1][2]. The formation of these complexes occurs due to the interaction of active hydrogen with substrates containing electron donors. ...
... The obtained substances were analyzed by IR-, 1 H, 13 C-NMR [15][16], using methods using a gas chromatography-mass spectrometer APCI Method from Agilent Technologies 6420 in a column with 5% phenylmethyl-silicone liquid CI 18, in the temperature range from 150 0 С to 320 0 С with inert mass spectrum of Agilent Technologies 9973 with control parameter up to 500 0 С. ...
Article
The work describes the processes of synthesis of cyanuric acid, its mono-, di-, tri-vinyl ethers in the solvent, Cact/KOH system under pressure, optimal synthesis conditions, catalyst activation, the effect of the molar ratio of the starting materials on the yield of cyanuric acid vinyl ethers, analyzed the effect of structure and the number of radicals in the structure of vinyl esters of cyanuric acid during the process, data of chromatography-mass spectroscopic analysis are presented. It is known that cyanuric acid and its halogenated derivatives are used as biologically active substances. Analysis of the results shows that cyanuric acid can kill 72% of the studied microorganisms. Replacing the hydroxyl group in the cyanuric acid molecule with a vinyl group increases the biological activity of the compound, as well as its resistance to microorganisms.
... Cyanuric acid concentrations measured in swimming pool water were at least four orders of magnitude higher than those found in other water types. This can be attributed to the use of cyanuric acid in swimming pools and recreational waters to stabilize chlorine (Murphy et al., 2015). The WHO (2006) recommends an upper limit of 1.0 Â 10 8 ng/L for water concentrations of cyanuric acid in swimming pools. ...
... The WHO (2006) recommends an upper limit of 1.0 Â 10 8 ng/L for water concentrations of cyanuric acid in swimming pools. Excess cyanuric acid has been shown to decrease the disinfection efficacy of chlorine against bacteria (Murphy et al., 2015). In this study, 2 of 20 pool water samples contained cyanuric acid above 1.0 Â 10 8 ng/L. ...
Article
The extensive use of melamine and its three derivatives (i.e., ammeline, ammelide, and cyanuric acid) contributes to their widespread occurrence in the environment. Nevertheless, limited information is available on their distribution in the aquatic environment. In this study, concentrations and profiles of melamine and its derivatives were determined in 223 water samples, comprising river water, lake water, seawater, tap water, bottled water, rain water, wastewater, and swimming pool water, collected from New York State, USA. The sum concentrations of melamine and its derivatives (Σ4MELs) decreased in the following order: swimming pool water (median: 1.5 × 107 ng/L) >> wastewater (1240) > precipitation (739) > tap water (512) > river water (370) > lake water (347) > seawater (186) > bottled water (98). Cyanuric acid was the major compound, accounting for 60–100% of Σ4MELs concentrations in swimming pool water, wastewater, precipitation, tap water, seawater, and bottled water, whereas melamine dominated in river and lake water (54–64% of Σ4MELs). Significant positive correlations (0.499 < R < 0.703, p < 0.002) were found between the concentrations of melamine and atrazine concentrations in surface waters. The geographic distribution in the concentrations of Σ4MELs in river, lake, and tap water corresponded with the degree of urbanization, suggesting that human activities contribute to the sources of these chemicals in the aquatic environments. A preliminary hazard assessment of melamine and cyanuric acid in water suggested that their ecological or human health risks were minimal. This is the first study to document the occurrence and spatial distribution of melamine and its derivatives in waters from the United States.
... The emergence of Cryptosporidium as the leading etiology of aquatic facility-associated outbreaks results from the parasite's extreme chlorine tolerance. Free available chlorine inactivates most infectious pathogens within minutes at CDC-recommended concentrations of at least 1 ppm § ; however, Cryptosporidium oocysts can survive for days (9). As the Alabama outbreak investigation indicates, even properly operated and maintained aquatic venues can be sites of Cryptosporidium transmission. ...
... As the Alabama outbreak investigation indicates, even properly operated and maintained aquatic venues can be sites of Cryptosporidium transmission. In addition, cyanuric acid (a stabilizer added to prevent chlorine depletion by the sun's ultraviolet light) has been found to substantially delay chlorine inactivation of Cryptosporidium (9). Consequently, in July 2016, CDC issued revised recommendations for hyperchlorination (https://www.cdc.gov/healthywater/swimming/ ...
Article
Full-text available
What is already known about this topic? Cryptosporidium has emerged as the leading etiology of recreational water–associated outbreaks, particularly those associated with aquatic facilities (places that contain one or more aquatic venues [e.g., swimming pools, interactive water play venues or water playgrounds, or hot tubs/spas] and support infrastructure [e.g., chemical storage space]). What is added by this report? Most Cryptosporidium species are indistinguishable by traditional diagnostic tests (microscopy or immunoassays); only molecular diagnostic methods, such as those used by CryptoNet, the first U.S. molecularly based surveillance system for a parasitic disease, can distinguish these species and their subtypes. Given that individual Cryptosporidium species can have unique host ranges, identifying the Cryptosporidium species can provide insight into possible exposures and outbreak sources. In the summer of 2016, when detection of cryptosporidiosis outbreaks increased, CryptoNet supported outbreak investigations by further elucidating Cryptosporidium chains of transmission. What are the implications for public health practice? Regular analysis of molecular characterization and epidemiologic data through CryptoNet for each nationally notified cryptosporidiosis case can further elucidate Cryptosporidium chains of transmission and cryptosporidiosis epidemiology (e.g., by monitoring geographic and temporal changes in the distribution of Cryptosporidium species and their subtypes and associated exposures). CryptoNet data can then be used to optimize development of evidence-based prevention strategies. Not swimming when ill with diarrhea is key to preventing and controlling aquatic facility–associated cryptosporidiosis outbreaks (https://www.cdc.gov/healthywater/swimming/ swimmers/steps-healthy-swimming.html). State and local jurisdictions and aquatic facilities can voluntarily adopt recommendations in CDC’s Model Aquatic Health Code (https:// www.cdc.gov/mahc/editions/current.html) to prevent and control Cryptosporidium transmission in public aquatic venues. © 2017, Department of Health and Human Services. All rights reserved.
... They added that infection incrimination increased as an important cause of morbidity and mortality worldwide, and that partial immunity after exposure suggested the potential for successful vaccines, and several were in development; however, surrogates of protection are not well defined. Also, Murphy et al. (2015) in USA reported that an infected swimmer excreted 107-108 oocysts in a diarrheal incident in water that can survive >7 days at CDC-recommended concentrations of >1ppm free available chlorine. Chalmers and Cacciò (2016) in United Kingdom concluded that increased dependable Cryptosporidium diagnostic practices were fundamental to the meaningful interpretation of surveillance data, species distribution and genotypes. ...
... For example, when CYA reacts with melamine (MEL), it can induce high nephrotoxicity and aggravate renal toxicity (Wang et al., 2012;Chang et al., 2014;Kannan, 2018, 2019c, b). In addition, when abundant CYA was present in water, the disinfection efficacy of FC became lower toward Cryptosporidium oocysts (Murphy et al., 2015) and Giardia (Falk et al., 2019). In fact, CYA has been detected frequently in human urine samples (Sathyanarayana et al., 2019;Zhu and Kannan, 2019a). ...
Article
Chlorinated cyanurates (CCAs) are a type of disinfectants currently used worldwide for fight of Coronavirus. However, CCAs upon dosed into water can release not only free chlorine (FC), a strong disinfectant, but also cyanurate (CYA), a persistent compound potentially harmful to human and environment. Therefore, detecting CYA and FC in water are very important not only for ensuring sufficient disinfection but also for monitoring the impacts of FC and CYA on receiving watershed. However, conventional analytical methods for them are mostly based on colorimetric methods, which have high method detection limits (MDLs) and rely on chemical reactions that are likely sensitive to coexisting chemicals. To overcome these issues, we herein proposed a facile and reaction-free method to detect CYA and FC together in just one run by ion chromatography (IC) equipped with both conductivity and ultraviolet absorbance detectors. The method features obvious advantages over colorimetric methods in being lower MDLs (3.6 μg/L for CYA and 9.0 μg/L for FC), environmental-friendly (i.e., no organic solvent involved), and more resistant to alkaline solution. With this method, trace levels of CYA (i.e., 34–44 μg/L), which were nondetectable by conventional method, were found in two river water samples, implying that the local environment was already polluted by CCAs during the pandemic period. Overall, this study demonstrates a robust tool that may assist better understanding and monitoring the fate and transport of trace CCA derivatives in water.
... These opposite results may denote that the action of chlorine-based disinfectants is not speciesdependent. The results also reinforce that chlorinated cyanurates are less effective disinfectants against planktonic bacteria in comparison to the use of free chlorine alone (Murphy et al., 2015;Wahman, 2018;Wojtowicz, 2001). ...
Article
The understanding of microbial susceptibility to disinfectants is an important step to provide drinking water (DW) of adequate microbiological quality. In drinking water distribution systems (DWDS) the application of disinfectants is the main approach to control microorganisms. Although chlorine has been commonly used for DW treatment, the increase of microbial resistance and the production of harmful disinfection by-products promote the necessity to seek new alternatives. This study evaluated the antimicrobial activity of sodium dichloroisocyanurate (NaDCC), trichloroisocyanuric acid (TCCA), and pentapotassium bis(peroxymonosulphate) bis(sulphate) (OXONE) against two emerging pathogens isolated from DW, Acinetobacter calcoaceticus and Stenotrophomonas maltophilia. Free chlorine from calcium hypochlorite was used for comparison. The dose and time-responses against planktonic bacteria were performed as well as the assessment of the effects on membrane integrity. Moreover, the effects against 48 h-old biofilms formed on polyvinyl chloride and stainless steel were evaluated in terms of biofilm culturability and removal. Minimum bactericidal concentrations of 2.1 and 3.1 mg/L for NaDCC, 2.5 and 3.8 mg/L for TCCA, 340 and 690 mg/L for OXONE, and 0.80 and 1.0 mg/L for free chlorine alone were obtained against S. maltophilia and A. calcoaceticus, respectively. The kinetic modeling revealed that NaDCC and TCCA caused similar inactivation rates and the time for first log reduction by OXONE was less than 10 min, for both bacteria. All the disinfectants triggered significant bacterial cytoplasmic membrane destabilization, even at sub-lethal concentrations. A 30 min treatment with the disinfectants allowed a reduction in the biofilm culturability up to 5 log. OXONE was the disinfectant with the best efficiency against both bacterial biofilms. However, one of the disinfectants caused significant biofilm removal (reduction < 1 log cells/cm²). This study highlights NaDCC, TCCA, and OXONE as promising alternatives to free chlorine for DW disinfection, particularly for planktonic growth control and biofilm culturability reduction.
... Cryptosporidiosis is a notifiable disease in Australia, and data indicate that aquatic facilities are a major source of cryptosporidiosis outbreaks [2][3][4][5][6][7][8]. This is mainly due to the resistance of the parasite's environmental stage, the oocyst, to normal chlorine levels used to disinfect pools, its very low infectious dose (1-125 oocysts), and small size that render most pool filtration systems ineffective in removing oocysts and preventing outbreaks [9][10][11]. Although ozone [12] and ultraviolet (UV) radiation [13] secondary treatments can inactivate Cryptosporidium oocysts, in most cases, they do not have a residual effect in the pool and cryptosporidiosis outbreaks are still reported in association with ozone and UV-treated pools [5,14]. ...
Article
PurposeThere is a dearth of research conducted on the Knowledge, Attitude and Practices (KAP) of swimming pool patrons and staff to determine their understanding of the importance of Cryptosporidium and its transmission in swimming pools.Methods We conducted a KAP survey of public swimming pool patrons (n = 380) and staff (n = 40) attending five public swimming pools in Western Australia (WA).ResultsKnowledge, attitudes and practices (KAP) of Cryptosporidium varied between patrons and staff but were generally limited. Only 26.1% and 25.0% of patrons and staff had heard of Cryptosporidium, while 17.4% and 10.0% knew that it causes diarrhoea, respectively. Thirty-one percent of patrons were aware of their pool policy concerning gastroenteritis and Cryptosporidium, compared to 62.5% of staff. Less than 50% of patrons demonstrated awareness of how features within the pool environment were relevant to the control of Cryptosporidium. Only about a third of patrons (35%) and staff (37.5%) were aware that showering before swimming reduced the risk of gastroenteritis.Conclusion Raising awareness about hygiene-related practices through the delivery of targeted health education messages to the general public is essential to reduce the burden of Cryptosporidium infections in aquatic environments.
... Alternative in vitro techniques that have been explored include experimental infections in cell cultures, in vitro excystation, sporulation, vital dye inclusion/exclusion, propidium monoazide PCR (PMA-PCR), nucleic acid sequence-based amplification (NASBA), and reverse transcription quantitative PCR (RT-qPCR) [11], with each method having advantages and disadvantages. In vitro cell culture has been widely used for assessing the efficacy of Cryptosporidium inactivation by chlorination and UV irradiation among others [12][13][14][15]. It has been shown that the in vitro excystation method overestimated the viability of Cryptosporidium oocysts when, in particular, assessing the efficacy of UV inactivation, which was thus suggested to be less efficacious [16]. ...
Article
Full-text available
Cryptosporidium oocysts are known for being very robust, and their prolonged survival in the environment has resulted in outbreaks of cryptosporidiosis associated with the consumption of contaminated water or food. Although inactivation methods used for drinking water treatment, such as UV irradiation, can inactivate Cryptosporidium oocysts, they are not necessarily suitable for use with other environmental matrices, such as food. In order to identify alternative ways to inactivate Cryptosporidium oocysts, improved methods for viability assessment are needed. Here we describe a proof of concept for a novel approach for determining how effective inactivation treatments are at killing pathogens, such as the parasite Cryptosporidium. RNA sequencing was used to identify potential up-regulated target genes induced by oxidative stress, and a reverse transcription quantitative PCR (RT-qPCR) protocol was developed to assess their up-regulation following exposure to different induction treatments. Accordingly, RT-qPCR protocols targeting thioredoxin and Cryptosporidium oocyst wall protein 7 (COWP7) genes were evaluated on mixtures of viable and inactivated oocysts, and on oocysts subjected to various potential inactivation treatments such as freezing and chlorination. The results from the present proof-of-concept experiments indicate that this could be a useful tool in efforts towards assessing potential technologies for inactivating Cryptosporidium in different environmental matrices. Furthermore, this approach could also be used for similar investigations with other pathogens.
... The parasite is also the leading cause of recreational water associated gastroenteritis outbreaks worldwide (Efstratiou et al., 2017;Hlavsa et al., 2017;Ryan et al., 2017). This is largely due to the resistance of the environmental stage of the parasite, the oocyst, to normal chlorine levels used for pool disinfection and its very low infectious dose (1-125 oocysts) (Murphy et al., 2015;Ryan et al., 2017). Cryptosporidium may be introduced into swimming pools by both symptomatic or asymptomatic bathers, mainly via poor swimmer hygiene (Yoder et al., 2010). ...
Article
Cryptosporidium is an important protozoan parasite and due to its resistance to chlorine is a major cause of swimming pool-associated gastroenteritis outbreaks. The present study combined contact tracing and molecular techniques to analyse cryptosporidiosis cases and outbreaks in Western Australia in 2019 and 2020. In the 2019 outbreak, subtyping at the 60 kDa glycoprotein (gp60) gene identified 89.0% (16/18) of samples were caused by the C. hominis IdA15G1 subtype. Amplicon next generation sequencing (NGS) at the gp60 locus identified five C. hominis IdA15G1 subtype samples that also had C. hominis IdA14 subtype DNA, while multi locus sequence typing (MLST) analysis on a subset (n = 14) of C. hominis samples identified three IdA15G1 samples with a 6 bp insertion at the end of the trinucleotide repeat region of the cp47 gene. In 2020, 88.0% (73/83) of samples typed were caused by the relatively rare C. hominis subtype IbA12G3. Four mixed infections were observed by NGS with three IdA15G1/ IdA14 mixtures and one C. parvum IIaA18G3R1 sample mixed with IIaA16G3R1. No genetic diversity using MLST was detected. Epidemiological and molecular data indicates that the outbreaks in 2019 and 2020 were each potentially from swimming pool point sources and a new C. hominis subtype IbA12G3 is emerging in Australia. The findings of the present study are important for understanding the introduction and transmission of rare Cryptosporidium subtypes to vulnerable populations.
... Because of the combination of a fast equilibrium (Matte et al., 1990) between H 3 Cy and its three dissociation products, HOCl, and chlorinated cyanurates ( Fig. 1 and Table 1) and the possibility of direct reactions with method reagents ( Jensen and Johnson, 1990), typical wet chemistry methods (e.g., N,N-diethyl-p-phenylenediamine [DPD]-based methods and amperometric titration) used to measure the free chlorine concentration in drinking water systems adding dichlor or trichlor exhibit measurement bias from the presence of chlorinated cyanurates (Whittle, 1970;Canelli, 1980;Wajon and Morris, 1980;Jensen and Johnson, 1990;Wahman et al., 2017). Therefore, when TOTCy is greater than zero and no ammonia is present to form chloramines, the free chlorine concentration is overestimated, which is important because the effective disinfectant in systems wherein chlorinated cyanurates and free chlorine are present is considered to be free chlorine, specifically HOCl (Canelli, 1974;Engel et al., 1983;Yamashita et al., 1988;Wojtowicz, 1996;Murphy et al., 2015). ...
Article
In the United States, approved methods to measure free chlorine concentrations in drinking water systems adding sodium dichloroisocyanurate (dichlor) or trichloroisocyanuric acid (trichlor) as chlorine sources exhibit measurement bias from the presence of chlorinated cyanurates, leading to overestimated free chlorine concentrations for regulatory compliance. One option to overcome this limitation is to estimate free chlorine concentrations using an established water chemistry model (full model), but the full model has only been determined for 25°C. The current research used a simplified version of the full model (simple model) and estimated the unknown temperature dependence (5°C to 35°C) of the two remaining equilibrium constants (K 7a and K 9a ) required for the simple model. At 0 M ionic strength (μ), or , = 38.8 ± 6.0 kJ/mol (95% confidence interval [CI]), or , and = 42.7 ± 3.0 kJ/mol (95% CI). At 25°C and μ of 0 M, the simple model estimated pK 7a and pK 9a are 4.65 ± 0.059 (95% CI) and 5.83 ± 0.020 (95% CI), respectively. As an example of the impact of temperature, the free chlorine concentration for a 2 mg Cl 2 /L dichlor addition (pH 7.0) decreases from 0.90 mg Cl 2 /L at 25°C to 0.60 mg Cl 2 /L at 5°C. If temperature was not considered, a system operating at 5°C would overestimate their free chlorine concentration by 50%, which could have significant implications for understanding disinfection efficacy, illustrating the developed model's significance.
... Chlorine is the primary barrier to the transmission of patho- gens in treated recreational water. At CDC-recommended concentrations of at least 1 ppm, † † † free available chlorine inactivates most pathogens within minutes although extremely chlorine-tolerant Cryptosporidium can survive for >7 days (2,3). Cryptosporidium is transmitted when a diarrheal incident (i.e., a high-risk Cryptosporidium contamination event) occurs in the water and the contaminated water is ingested. ...
Article
Full-text available
This report summarizes trends in outbreaks associated with recreational water use from 2000–2014, which include infections with pathogens of concern for transplant recipients, such as Legionella and Cryptosporidium
... Chlorine is the primary barrier to the transmission of patho- gens in treated recreational water. At CDC-recommended concentrations of at least 1 ppm, † † † free available chlorine inactivates most pathogens within minutes although extremely chlorine-tolerant Cryptosporidium can survive for >7 days (2,3). Cryptosporidium is transmitted when a diarrheal incident (i.e., a high-risk Cryptosporidium contamination event) occurs in the water and the contaminated water is ingested. ...
Article
Full-text available
Outbreaks associated with exposure to treated recreational water can be caused by pathogens or chemicals in venues such as pools, hot tubs/spas, and interactive water play venues (i.e., water playgrounds). During 2000-2014, public health officials from 46 states and Puerto Rico reported 493 outbreaks associated with treated recreational water. These outbreaks resulted in at least 27,219 cases and eight deaths. Among the 363 outbreaks with a confirmed infectious etiology, 212 (58%) were caused by Cryptosporidium (which causes predominantly gastrointestinal illness), 57 (16%) by Legionella (which causes Legionnaires' disease, a severe pneumonia, and Pontiac fever, a milder illness with flu-like symptoms), and 47 (13%) by Pseudomonas (which causes folliculitis ["hot tub rash"] and otitis externa ["swimmers' ear"]). Investigations of the 363 outbreaks identified 24,453 cases; 21,766 (89%) were caused by Cryptosporidium, 920 (4%) by Pseudomonas, and 624 (3%) by Legionella. At least six of the eight reported deaths occurred in persons affected by outbreaks caused by Legionella. Hotels were the leading setting, associated with 157 (32%) of the 493 outbreaks. Overall, the outbreaks had a bimodal temporal distribution: 275 (56%) outbreaks started during June-August and 46 (9%) in March. Assessment of trends in the annual counts of outbreaks caused by Cryptosporidium, Legionella, or Pseudomonas indicate mixed progress in preventing transmission. Pathogens able to evade chlorine inactivation have become leading outbreak etiologies. The consequent outbreak and case counts and mortality underscore the utility of CDC's Model Aquatic Health Code (https://www.cdc.gov/mahc) to prevent outbreaks associated with treated recreational water.
... Of note, cyanuric acid prolongs the inactivation time of infectious pathogens, with inactivation times increasing with higher cyanuric levels. For example, at 20 ppm FAC, raising the cyanuric acid level from 16 ppm to 48 ppm decreases effectiveness of inactivation from 26.3 hours (99.9% inactivation) to 63.8 hours (90% inactivation) (Murphy et al., 2015). ...
Article
We investigated a gastrointestinal illness cluster among persons who attended a baseball tournament (>200 teams) during July 2015. We interviewed representatives of 19 teams; illness was reported among only the 9 (47%) teams that stayed at Hotel A (p < .01). We identified 55 primary cases. A case-control study demonstrated that pool exposure at Hotel A was significantly associated with illness (odds ratio: 7.3; 95% confidence interval: 3.6, 15.2). Eight out of nine (89%) stool specimens tested were positive for Cryptosporidium, with C. hominis IfA12G1 subtype identified in two specimens. The environmental health assessment detected a low free available chlorine level, and pool water tested positive for E. coli and total coliforms. A possible diarrheal contamination event, substantial hotel pool use, and use of cyanuric acid might have contributed to this outbreak and magnitude. Aquatic facilities practicing proper operation and maintenance (e.g., following the Centers for Disease Control and Prevention’s Model Aquatic Health Code) can protect the public’s health.
... Recent research shows a 67,200 min contact time in the presence of 50 mg/L cyanuric acid and at a lower pH (6.5) is necessary to achieve a 3 log reduction of oocysts (Shields et al., 2009). At 100 mg/L cyanuric acid, only a 0.8 log reduction of Cryptosporidium oocysts was achieved in the presence of 20 mg/L chlorine over 72 h (Murphy et al., 2015). We recommend pools using stabilizers reduce cyanuric acid to 50 mg/L before shockchlorinating and achieve a 67,200 min contact time after a reported loose fecal release, or install a secondary disinfection system. ...
Article
Background: Infection risk estimates from swimming in treated recreational water venues are lacking and needed to prioritize public health interventions in swimming pools. Quantitative infection risk estimates among different age groups are needed to identify vulnerable populations. High risk populations can be targeted during public health interventions, like education campaigns and pool operation improvements. Objectives: This study estimated per-swim and annual Cryptosporidium infection risks in adults (>18) and children (≤18) using new experimental data collected in the U.S. on swimmer behavior. Methods: Risks were estimated using oocyst concentration data from the literature, and data collected in this study on pool water ingestion, swim duration and pool use frequency. A sensitivity analysis identified the most influential model variables on infection probability. Results: The average estimated risk of Cryptosporidium infection was 2.6×10(-4) infections/swim event. The per-swim risk estimate in the present study differed from others because behavior data (ingestion rates, swim duration, and visit frequency) were collected in different countries and varied from U.S. estimates. We found swimmer behaviors influence infection risk. This is the first study to report annual risk of Cryptosporidium infection among swimmers by age group. Using U.S. exposure data, annual risk was estimated at 2.9×10(-2) infections/year for children and 2.2×10(-2) infections/year for adults. Annual risk for all swimmers was estimated at 2.5×10(-2) infections/year from swimming in treated recreational water venues. Due to increased ingestion and swim duration, child swimmers had the highest annual risk estimate. Cryptosporidium concentration is the most influential variable on infection probability. Conclusions: Results suggest the need for standardized pool water quality monitoring for Cryptosporidium, education, development of interventions to reduce ingestion, consideration of behaviors unique to swimming populations in future risk assessments and improvement of oocyst removal from pool water. Child swimmers were the most vulnerable sub-population, and should be targeted in healthy swimming education campaigns.
... Thus, TCCA can guarantee less DBP formation than NaClO on the basis of same initial chlorine dose. Meanwhile, some studies show that an excess of cyanuric acid may delay the inactivation of microbes such as streptococcus faecalis and cryptosporidium parvum (Murphy et al., 2015;Wojtowicz, 1996). However, based on the empirically fitted regression equation t 0.99 ¼ 0.0268*[HClO] À1.014 proposed by Wojtowicz (1996), linking between 99% kill time and HClO concentration, the estimated kill time of enteric bacteria by TCCA could only be delayed by 0.011 min compared to NaClO. ...
Article
Sodium hypochlorite (NaClO) is the most commonly used disinfectant in pool treatment system. Outdoor pools usually suffer from the strong sunlight irradiation which degrades the free chlorine rapidly. In addition, more pools start to adopt the recirculation of swimming pool water, which intensifies the disinfection by-product (DBP) accumulation issue. Given these potential drawbacks of using NaClO in the tropical environment, two alternative organic-based disinfectants, trichloroisocyanuric acid (TCCA, C3Cl3N3O3) and bromochlorodimethylhydantoin (BCDMH, C5H6BrClN2O2), were investigated and compared to NaClO in terms of their self-degradation and the formation of DBPs, including trihalomethanes (THMs) and haloacetic acids (HAAs), under simulated tropical climate conditions. The result reveals that halogen stabilizer, TCCA, had the advantages of slower free chlorine degradation and lower DBP concentration compared to NaClO, which makes it a good alternative disinfectant. BCDMH was not recommended mainly due to the highly reactive disinfecting ingredient, hypobromous acid (HBrO), which fails to sustain the continuous disinfection requirement. Total disinfectant dosage was the main factor that affects residual chlorine/bromine and THM/HAA formation regardless of different disinfectant dosing methods, e.g. shock dosing (one-time spiking) in the beginning, and continuous dosing during the whole experimental period. Two-stage second-order-kinetic-based models demonstrate good correlation between the measured and predicted data for chlorine decay (R2 ≥ 0.95), THM (R2 ≥ 0.99) and HAA (R2 ≥ 0.83) formation. Higher temperature was found to enhance the DBP formation due to the temperature dependence of reaction rates. Thus, temperature control of pools, especially for those preferring higher temperatures (e.g. hydrotherapy and spa), should take both bather comfort and DBP formation potential into consideration. It is also observed that chlorine competition existed between different precursors from natural organic matters (NOM) in filling water and body fluid analogue (BFA). Among the composition of BFA, uric acid, citric acid and hippuric acid were found to be the main precursors for HAA formation.
... CYA builds up after multiple additions because, unlike the hypochlorite, it is very stable chemically and does not degrade in the absence of enzymes. Studies dating back to the 1960s have demonstrated that high concentrations of CYA in pools significantly reduce disinfection efficacy, and thus, viruses, bacteria, and protozoa that may enter the water will not be inactivated (5)(6)(7). Therefore, it is essential to remove CYA when the concentration rises above 1 mM (~100 ppm). To date, the remedy for high CYA concentrations has been to drain and refill the pools, which is inefficient in terms of pool management and significantly increases freshwater usage. ...
Article
Full-text available
Unlabelled: Chlorinated isocyanuric acids are widely used water disinfectants that generate hypochlorite, but with repeated application, they build up cyanuric acid (CYA) that must be removed to maintain disinfection. 3-Aminopropyltriethoxysilane (APTES)-treated Escherichia coli cells expressing cyanuric acid hydrolase (CAH) from Moorella thermoacetica exhibited significantly high CYA degradation rates and provided protection against enzyme inactivation by hypochlorite (chlorine). APTES coating or encapsulation of cells had two benefits: (i) overcoming diffusion limitations imposed by the cell wall and (ii) protecting against hypochlorite inactivation of CAH activity. Cells encapsulated in APTES gels degraded CYA three times faster than nonfunctionalized tetraethoxysilane (TEOS) gels, and cells coated with APTES degraded CYA at a rate of 29 µmol/min per mg of CAH protein, similar to the rate with purified enzyme. UV spectroscopy, fluorescence spectroscopy, and scanning electron microscopy showed that the higher rates were due to APTES increasing membrane permeability and enhancing cyanuric acid diffusion into the cytoplasm to reach the CAH enzyme. Purified CAH enzyme was shown to be rapidly inactivated by hypochlorite. APTES aggregates surrounding cells protected via the amine groups reacting with hypochlorite as shown by pH changes, zeta potential measurements, and infrared spectroscopy. APTES-encapsulated E. coli cells expressing CAH degraded cyanuric acid at high rates in the presence of 1 to 10 ppm hypochlorite, showing effectiveness under swimming pool conditions. In contrast, CAH activity in TEOS gels or free cells was completely inactivated by hypochlorite. These studies show that commercially available silica materials can selectively enhance, protect, and immobilize whole-cell biocatalysts for specialized applications. Importance: Hypochlorite is used in vast quantities for water disinfection, killing bacteria on surfaces, and washing and whitening. In pools, spas, and other waters, hypochlorite is frequently delivered as chlorinated isocyanuric acids that release hypochlorite and cyanuric acid. Over time, cyanuric acid accumulates and impairs disinfection and must be removed. The microbial enzyme cyanuric acid hydrolase can potentially remove cyanuric acid to restore disinfection and protect swimmers. Whole bacterial cells expressing cyanuric acid hydrolase were encapsulated in an inert silica matrix containing an amine group. The amine group serves to permeabilize the cell membrane and accelerate cyanuric acid degradation, and it also reacts with hypochlorite to protect against inactivation of cyanuric acid hydrolase. Methods for promoting whole-cell biocatalysis are important in biotechnology, and the present work illustrates approaches to enhance rates and protect against an inhibitory substance.
Article
As urban communities continue to grow, demand for recreational access (including swimming) in drinking water sources have increased, yet relatively little is understood about the public health implications this poses for drinking water consumers. Preventative risk-based approaches to catchment management, informed by quantitative microbial risk assessment (QMRA), requires accurate input data to effectively model risks. A sound understanding of the knowledge gaps is also important to comprehend levels of uncertainty and help prioritise research needs. Cryptosporidium is one of the most important causes of waterborne outbreaks of gastroenteritis globally due to its resistance to chlorine. This review was undertaken by Water Research Australia to provide the most up-to-date information on current Cryptosporidium epidemiological data and underlying assumptions for exposure assessment, dose response and risk assessment for generic components of QMRA for Cryptosporidium and highlights priorities for common research. Key interim recommendations and guidelines for numerical values for relatively simple screening level QMRA modelling are provided to help support prospective studies of risks to drinking water consumers from Cryptosporidium due to body-contact recreation in source water. The review does not cover site-specific considerations, such as the levels of activity in the source water, the influence of dilution and inactivation in reservoirs, or water treatment. Although the focus is Australia, the recommendations and numerical values developed in this review, and the highlighted research priorities, are broadly applicable across all drinking source water sources that allow recreational activities.
Article
This article describes 208 outbreaks associated with recreational water exposures in the U.S., the majority of which were due to either Cryptosporidium or Legionella infections and were primarily reported after exposure to public (i.e., nonbackyard) recreational water. These outbreaks resulted in 3646 cases of illness, 286 hospitalizations, and 13 deaths; all deaths were due to Legionella infection. Most outbreaks began between June and August each year, suggesting that solid organ transplant candidates and recipients should be mindful of the risks associated with public recreational water, particularly during the summer months.
Article
Outbreaks associated with treated recreational water can be caused by pathogens or chemicals in aquatic venues such as pools, hot tubs, water playgrounds, or other artificially constructed structures that are intended for recreational or therapeutic purposes. For the pseriod 2015-2019, public health officials from 36 states and the District of Columbia (DC) voluntarily reported 208 outbreaks associated with treated recreational water. Almost all (199; 96%) of the outbreaks were associated with public (nonbackyard) pools, hot tubs, or water playgrounds. These outbreaks resulted in at least 3,646 cases of illness, 286 hospitalizations, and 13 deaths. Among the 155 (75%) outbreaks with a confirmed infectious etiology, 76 (49%) were caused by Cryptosporidium (which causes cryptosporidiosis, a gastrointestinal illness) and 65 (42%) by Legionella (which causes Legionnaires' disease, a severe pneumonia, and Pontiac fever, a milder illness with flu-like symptoms). Cryptosporidium accounted for 2,492 (84%) of 2,953 cases resulting from the 155 outbreaks with a confirmed etiology. All 13 deaths occurred in persons affected by a Legionnaires' disease outbreak. Among the 208 outbreaks, 71 (34%) were associated with a hotel (i.e., hotel, motel, lodge, or inn) or a resort, and 107 (51%) started during June-August. Implementing recommendations in CDC's Model Aquatic Health Code (MAHC) (1) can help prevent outbreaks associated with treated recreational water in public aquatic venues.
Article
The aim of this study was to ascertain the biocidal efficacy, based on the so-called C·t values, and the usage expenses of seven disinfection products in recreational waters using Escherichia coli and Pseudomonas aeruginosa as microorganism models of fecal and environmental contamination, respectively. A 250-L indoor fully equipped pool basin was harnessed as a proof-of-concept setup for the evaluation of chlorine-based [viz., trichloroisocyanuric acid (trichloro), sodium hypochlorite, sodium hypochlorite + isocyanuric acid, and saline electrolysis] and unconventional (viz., 1-bromo-3-chloro-5,5-dimethylilhidantoine, chlorine dioxide and hydrogen peroxide) biocides at 30°C and different pH values. The economic losses resulting from human action, mimicked by urea addition, were also considered. Experimental results showed that trichloro, chlorine dioxide, and sodium hypochlorite were the most effective disinfection agents with a log 3 removal of both organisms in 60 s regardless of the water pH. On the other hand, sodium hypochlorite and trichloro afforded unparalleled cost-effectiveness. Chlorine dioxide exhibits the greatest biocide efficacy, yet its elevated usage costs make it merely applicable in shock treatments to offset high organic loads.
Article
Full-text available
This report describes the 444 cryptosporidiosis outbreaks that occurred in the United States between 2009 and 2017 and discusses preventive measures for this infection.
Chapter
This chapter provides a detailed protocol to assess disinfection efficacy of chlorine against Cryptosporidium oocysts including the core chlorine disinfection assay, the in vitro cell culture infectivity assay, and microscopy analysis and data interpretation.
Article
Full-text available
Cryptosporidium is a parasite that causes cryptosporidiosis, a profuse, watery diarrhea that can last up to 3 weeks in immunocompetent patients and can lead to life-threatening malnutrition and wasting in immunocompromised patients.* Fecal-oral transmission can occur by ingestion of contaminated recreational water, drinking water, or food, or through contact with infected persons or animals. For the period 2009-2017, public health officials from 40 states and Puerto Rico voluntarily reported 444 cryptosporidiosis outbreaks resulting in 7,465 cases. Exposure to treated recreational water (e.g., in pools and water playgrounds) was associated with 156 (35.1%) outbreaks resulting in 4,232 (56.7%) cases. Other predominant outbreak exposures included contact with cattle (65 outbreaks; 14.6%) and contact with infected persons in child care settings (57; 12.8%). The annual number of reported cryptosporidiosis outbreaks overall increased an average of approximately 13% per year over time. Reversing this trend will require dissemination of prevention messages to discourage swimming or attending child care while ill with diarrhea and encourage hand washing after contact with animals. Prevention and control measures can be optimized by improving understanding of Cryptosporidium transmission through regular analysis of systematically collected epidemiologic and molecular characterization data.
Article
Two chlorinated cyanurates, commonly referred to as dichlor (anhydrous sodium dichloroisocyanurate or sodium dichloroisocyanurate dihydrate) and trichlor (trichloroisocyanuric acid), may be approved for use in U.S. drinking water systems as chlorine sources. One complication with dichlor or trichlor's application in drinking water is that the actual free chlorine concentration in these systems cannot be quantified accurately by currently approved methods. Based on known water chemistry, two hypothesized advantages of dichlor or trichlor use are potential increased residual chlorine stability and decreased regulated disinfectant byproduct (DBP) formation. To inform these practical considerations, the current research investigated measurement bias in N,N‐diethyl‐p‐phenylenediamine (colorimetric and portable parallel analyzer), indophenol, amperometric titration, and amperometric electrode free chlorine methods. In addition, hold studies using a surface water and dosed with either free chlorine only, dichlor, or trichlor provided the first side‐by‐side comparisons of disinfectant residual stability and regulated DBP formation.
Article
Since 1958, cyanuric acid and two chlorinated cyanurates, commonly referred to as dichlor (anhydrous sodium dichloroisocyanurate or sodium dichloroisocyanurate dihydrate) and trichlor (trichloroisocyanuric acid), have been added to outdoor swimming pools to stabilize chlorine residual by minimizing sunlight‐related degradation. Subsequently, in July 2001, dichlor and trichlor were approved for routine drinking water treatment under the US Federal Insecticide, Fungicide, and Rodenticide Act, and manufacturers have achieved NSF 60 certification for dichlor or trichlor addition to drinking water. Currently in the United States, dichlor or trichlor for drinking water use may be approved by states, tribes, or territories. One complicating factor with dichlor or trichlor is that the actual free chlorine concentration in these systems cannot be measured accurately by currently approved methods. This review summarizes the existing water chemistry associated with dichlor and trichlor use as a chlorine source in drinking water, along with the associated implications.
Article
Full-text available
During the 2012 summer swim season, aquatic venue data and filter backwash samples were collected from 127 metro-Atlanta pools. Last-recorded water chemistry measures indicated 98% (157/161) of samples were from pools with ≥1 mg/L residual chlorine without stabilized chlorine or ≥2 mg/L with stabilized chlorine and 89% (144/161) had pH readings 7.2-7.8. These water quality parameters are consistent with the 2016 Model Aquatic Health Code (2nd edition) recommendations. We used previously validated real-time polymerase chain reaction assays for detection of seven enteric microbes, including Escherichia coli, and Pseudomonas aeruginosa. E. coli was detected in 58% (93/161) of samples, signifying that swimmers likely introduced fecal material into pool water. P. aeruginosa was detected in 59% (95/161) of samples, indicating contamination from swimmers or biofilm growth on surfaces. Cryptosporidium spp. and Giardia duodenalis were each detected in approximately 1% of samples. These findings indicate the need for aquatics staff, state and local environmental health practitioners, and swimmers to each take steps to minimize the risk of transmission of infectious pathogens.
Article
The Summary of Notifiable Infectious Diseases and Conditions - United States, 2015 (hereafter referred to as the summary) contains the official statistics, in tabular and graphical form, for the reported occurrence of nationally notifiable infectious diseases and conditions in the United States for 2015. Unless otherwise noted, data are final totals for 2015 reported as of June 30, 2016. These statistics are collected and compiled from reports sent by U.S. state and territories, New York City, and District of Columbia health departments to the National Notifiable Diseases Surveillance System (NNDSS), which is operated by CDC in collaboration with the Council of State and Territorial Epidemiologists (CSTE). This summary is available at https://www.cdc.gov/MMWR/MMWR_nd/index.html. This site also includes summary publications from previous years.
Article
Full-text available
Cyanuric acid hydrolases are of industrial importance because of their use in aquatic recreational facilities to remove cyanuric acid, a stabilizer for the chlorine. Degradation of excess cyanuric acid is necessary to maintain chlorine disinfection in the waters. Cyanuric acid hydrolase opens the cyanuric acid ring hydrolytically and subsequent decarboxylation produces carbon dioxide and biuret. In the present study, we report the X-ray structure of TrzD, a cyanuric acid hydrolase from Acidovorax citrulli. The crystal structure at 2.19 ? resolution shows a large displacement of the catalytic lysine (Lys163) in domain 2 away from the active site core, whereas the two other active site lysines from the two other domains are not able to move. The lysine displacement is proposed here to open up a channel for product release. Consistent with that, the structure also showed two molecules of the co-product, carbon dioxide, one in the active site and another trapped in the proposed exit channel. Previous data indicated that the domain 2 lysine residue plays a role in activating an adjacent serine residue carrying out nucleophilic attack, opening the cyanuric acid ring, and the mobile lysine guides products through the exit channel.
Article
Cryptosporidium is the leading cause of swimming pool outbreaks of gastroenteritis. Transmission occurs through the ingestion of oocysts that are passed in the faeces of an infected person or animal when an accidental faecal release event occurs. Cryptosporidium parasites present specific challenges for infection control as oocysts are highly resistant to chlorine levels used for pool disinfection, infected individuals can shed large numbers of oocysts, there is a long incubation period and shedding of oocysts occurs even after symptom resolution. The purposes of this review are to identify key barriers to limiting swimming poolassociated outbreaks of cryptosporidiosis and to outline needs for research and collaboration to advance co-ordinated management practices. We reviewed swimming pool-associated cryptosporidiosis outbreaks, disinfection teachniques, current regulations and the role of staff and patrons. Key barriers to limiting swimming pool-associated outbreaks of cryptosporidiosis are a lack of uniform national and international standards, poor adherence and understanding of regulations governing staff and patron behaviour, and low levels of public knowledge and awareness.
Article
Full-text available
Problem/condition: Aquatic facility-associated illness and injury in the United States include disease outbreaks of infectious or chemical etiology, drowning, and pool chemical-associated health events (e.g., respiratory distress or burns). These conditions affect persons of all ages, particularly young children, and can lead to disability or even death. A total of 650 aquatic facility-associated outbreaks have been reported to CDC for 1978-2012. During 1999-2010, drownings resulted in approximately 4,000 deaths each year in the United States. Drowning is the leading cause of injury deaths in children aged 1-4 years, and approximately half of fatal drownings in this age group occur in swimming pools. During 2003-2012, pool chemical-associated health events resulted in an estimated 3,000-5,000 visits to U.S. emergency departments each year, and approximately half of the patients were aged <18 years. In August 2014, CDC released the Model Aquatic Health Code (MAHC), national guidance that can be adopted voluntarily by state and local jurisdictions to minimize the risk for illness and injury at public aquatic facilities. Reporting period covered: 2013. Description of system: The Network for Aquatic Facility Inspection Surveillance (NAFIS) was established by CDC in 2013. NAFIS receives aquatic facility inspection data collected by environmental health practitioners when assessing the operation and maintenance of public aquatic facilities. This report presents inspection data that were reported by 16 public health agencies in five states (Arizona, California, Florida, New York, and Texas) and focuses on 15 MAHC elements deemed critical to minimizing the risk for illness and injury associated with aquatic facilities (e.g., disinfection to prevent transmission of infectious pathogens, safety equipment to rescue distressed bathers, and pool chemical safety). Although these data (the first and most recent that are available) are not nationally representative, 15.7% of the estimated 309,000 U.S. public aquatic venues are located in the 16 reporting jurisdictions. Results: During 2013, environmental health practitioners in the 16 reporting NAFIS jurisdictions conducted 84,187 routine inspections of 48,632 public aquatic venues. Of the 84,187 routine inspection records for individual aquatic venues, 78.5% (66,098) included data on immediate closure; 12.3% (8,118) of routine inspections resulted in immediate closure because of at least one identified violation that represented a serious threat to public health. Disinfectant concentration violations were identified during 11.9% (7,662/64,580) of routine inspections, representing risk for aquatic facility-associated outbreaks of infectious etiology. Safety equipment violations were identified during 12.7% (7,845/61,648) of routine inspections, representing risk for drowning. Pool chemical safety violations were identified during 4.6% (471/10,264) of routine inspections, representing risk for pool chemical-associated health events. Interpretation: Routine inspections frequently resulted in immediate closure and identified violations of inspection items corresponding to 15 MAHC elements critical to protecting public health, highlighting the need to improve operation and maintenance of U.S. public aquatic facilities. These findings also underscore the public health function that code enforcement, conducted by environmental health practitioners, has in preventing illness and injury at public aquatic facilities. Public health action: Findings from the routine analyses of aquatic facility inspection data can inform program planning, implementation, and evaluation. At the state and local level, these inspection data can be used to identify aquatic facilities and venues in need of more frequent inspections and to select topics to cover in training for aquatic facility operators. At the national level, these data can be used to evaluate whether the adoption of MAHC elements minimizes the risk for aquatic facility-associated illness and injury. These findings also can be used to prioritize revisions or updates to the MAHC. To optimize the collection and analysis of aquatic facility inspection data and thus application of findings, environmental health practitioners and epidemiologists need to collaborate extensively to identify public aquatic facility code elements deemed critical to protecting public health and determine the best way to assess and document compliance during inspections.
Article
Cyanuric acid was likely present on prebiotic Earth, may have been a component of early genetic materials, and is today synthesized industrially on a scale of more than one hundred million pounds per year in the United States. In light of this, it is not surprising that some bacteria and fungi have a metabolic pathway that sequentially hydrolyzes cyanuric acid and its metabolites to release the nitrogen atoms as ammonia to support growth. The initial reaction that opens the s -triazine ring is catalyzed by the unusual enzyme cyanuric acid hydrolase. This enzyme is in a rare protein family that consists of only cyanuric acid hydrolase (CAH) and barbiturase; the latter participating in pyrimidine catabolism by some actinobacterial species. The X-ray structures of two cyanuric acid hydrolase proteins show that this family has a unique protein fold. Phylogenetic, bioinformatic, enzymological, and genetic studies in total are consistent with the idea that CAH is an ancient protein fold that was rare in microbial populations, but is currently becoming more widespread in microbial populations in the wake of anthropogenic synthesis of cyanuric acid and other s -triazine compounds that are metabolized via a cyanuric acid intermediate. The need for removal of cyanuric acid from swimming pools and spas, where it is used as a disinfectant stabilizer, can potentially be met using an enzyme filtration system. A stable, thermophilic cyanuric acid hydrolase from Moorella thermoacetica is being tested for this purpose.
Article
Full-text available
Cryptosporidium spp. are a major cause of diarrheal disease in both immunocompetent and immunodeficient individuals. They also cause waterborne disease in both the United States and United Kingdom. Studies on the mechanisms of immunity to cryptosporidiosis indicate the importance of the T-cell response. The spectrum and severity of disease in immunocompromised individuals with cryptosporidiosis reflect this importance since the most severe disease is seen in individuals with defects in the T-cell response. The most commonly studied group is that of patients with AIDS. These patients suffer from more severe and prolonged gastrointestinal disease that can be fatal; in addition, body systems other than the gastrointestinal tract may be affected. The widespread use of antiretroviral therapy does appear to be having a beneficial effect on recovery from cryptosporidiosis and on the frequency of infection in human immunodeficiency virus-positive patients. Other diseases that are associated with increased risk of severe cryptosporidiosis, such as primary immunodeficiencies, most notably severe combined immunodeficiency syndrome, are also predominantly associated with T-cell defects. Of the remaining groups, children with acute leukemia seem to be most at risk from cryptosporidiosis. There is less evidence of severe complications in patients with other malignant diseases or in those receiving immunosuppressive chemotherapy.
Article
Full-text available
The in vitro cultivation of protozoan parasites of the genus Cryptosporidium has advanced significantly in recent years. These obligate, intracellular parasites colonize the epithelium of the digestive and respiratory tracts, are often difficult to obtain in significant numbers, produce durable oocysts that defy conventional chemical disinfection methods, and are persistently infectious when stored at refrigerated temperatures (4 to 8 degrees C). While continuous culture and efficient life cycle completion (oocyst production) have not yet been achieved in vitro, routine methods for parasite preparation and cell culture infection and assays for parasite life cycle development have been established. Parasite yields may be limited, but in vitro growth is sufficient to support a variety of research studies, including assessing potential drug therapies, evaluating oocyst disinfection methods, and characterizing life cycle stage development and differentiation.
Article
Techniques for culturing, harvesting, and testing bacteria to evaluate bactericidal chemicals for swimming pools are described. Concentrations of 25, 50, and 100 mg of the chlorine stabilizer cyanuric acid per liter increased the time required for a 99% kill of Streptococcus faecalis by 0.5 mg of chlorine per liter at pH 7.4 and 20 C from less than 0.25 min without cyanuric acid to 4, 6, and 12 min, respectively. The effect of concentrations of ammonia nitrogen in the range found in swimming pools on the rate of kill of 0.5 mg of chlorine per liter and of chlorine plus cyanuric acid was tested. At concentrations of ammonia nitrogen greater than 0.05 mg per liter, faster rates of kill of S. faecalis were obtained with 100 mg of cyanuric acid per liter plus 0.5 mg of chlorine per liter than with 0.5 mg of chlorine per liter alone. When water samples from four swimming pools with low ammonia levels were used as test media, 0.5 mg of added chlorine per liter killed 99.9% of the added S. faecalis in less than 2 min, but water from a pool with a large number of children required 60 to 180 min of treatment.
Article
Even extremely low dosages of ultraviolet light can be highly effective for inactivating Cryptosporidium oocysts.
Article
The ability of chlorine dioxide (ClO2) to achieve 2-log inactivation of Cryptosporidium in drinking water has been documented. No studies have specifically addressed the effects of ClO2 on C. parvum oocyst infectivity in chlorinated recreational water venues (e.g., pools). The aim of this research was to determine the efficacy of ClO2 as an alternative to existing hyperchlorination protocols that are used to achieve a 3-log inactivation of Cryptosporidium in such venues. To obtain a 3-log inactivation of C. parvum Iowa oocysts, contact times of 105 and 128 min for a solution containing 5 mg/L ClO2 with and without the addition of 2.6 mg/L free chlorine, respectively, were required. Contact times of 294 and 857 min for a solution containing 1.4 mg/L ClO2 with and without the addition of 3.6 mg/L free chlorine, respectively, were required. The hyperchlorination control (21 mg/L free chlorine only) required 455 min for a 3-log inactivation. Use of a solution containing 5 mg/L ClO2 and solutions containing 5 or 1.4 mg/L ClO2 with the addition of free chlorine appears to be a promising alternative to hyperchlorination for inactivating Cryptosporidium in chlorinated recreational water venues, but further studies are required to evaluate safety constraints on use.
Article
Recreational water-associated disease outbreaks result from exposure to infectious pathogens or chemical agents in treated recreational water venues (e.g., pools and hot tubs or spas) or untreated recreational water venues (e.g., lakes and oceans). For 2009-2010, the most recent years for which finalized data are available, public health officials from 28 states and Puerto Rico electronically reported 81 recreational water-associated disease outbreaks to CDC's Waterborne Disease and Outbreak Surveillance System (WBDOSS) via the National Outbreak Reporting System (NORS). This report summarizes the characteristics of those outbreaks. Among the 57 outbreaks associated with treated recreational water, 24 (42%) were caused by Cryptosporidium. Among the 24 outbreaks associated with untreated recreational water, 11 (46%) were confirmed or suspected to have been caused by cyanobacterial toxins. In total, the 81 outbreaks resulted in at least 1,326 cases of illness and 62 hospitalizations; no deaths were reported. Laboratory and environmental data, in addition to epidemiologic data, can be used to direct and optimize the prevention and control of recreational water-associated disease outbreaks.
Article
Recent studies have shown that Cryptosporidium parvum oocysts demonstrate high susceptibility to low dosages of medium-pressure ultraviolet (UV) light. These investigations have raised several questions, which include determination of minimum medium-pressure UV dosages necessary to inactivate C. parvum oocysts, elucidation of differences (if any) between medium-and low-pressure UV light for inactivating C parvum oocysts, and evaluation of medium-pressure UV effectiveness in inactivating oocysts suspended in poorer quality water. To compare low- and medium-pressure UV, the authors exposed oocysts suspended in deionized water to UV delivered by either medium- or low-pressure UV lamps at bench scale using a collimated beam apparatus. The applied UV dosages ranged from 3 to 33 mJ/cm², and oocyst inactivation was assessed using the neonatal mouse infectivity assay. At 3 mJ/cm², medium-pressure UV showed a 3.4-log inactivation of oocysts, and low-pressure UV showed a 3.0-log inactivation, demonstrating medium- and low-pressure UV did not differ significantly in inactivating C. parvum oocysts.
Article
The efficiency of chloroisocyanurates in swimming pool disinfection has been demonstrated by a number of authors (Andersen, 1965; Kolwalski and Hilton, 1966; Robinton and Mood, 1967; Fitzgerald and der Vartanian, 1969). The disinfection rate was seen to slow down during studies on different bacteria; this was attributed to the existence of a weak concentration of free chlorine (HOCl + ClO−). However, since these studies were carried out when the aqueous chemistry of chloroisocyanurates was not completely elucidated, the specific action of chloroisocyanurates was difficult to determine. This, in part, was due to the large number and variety of experimental procedures and analytical methods for chlorine measurements, and to the lack of specificity of the methods employed.We studied the action of chloroisocyanurates on three environmental strains: S. faecalis, S. aureus, Ps. aeruginosa and on one collection strain: Ps. aeruginosa—CIP. Disinfection tests were carried out in the laboratory, in pH and temperature conditions typically found in swimming pools (pH 7.5, 25°C). The initial concentration of total chlorine varies from 0.5 to 2.5 mg I−1, for concentrations of isocyanuric acid, H3Cy, from 25 to 360 mg 1−1. With these concentrations, free chlorine (HOCl + ClO−) does not exceed 3% of total chlorine (that is, less than 0.08 mg 1−1). We used an easy and rapid method of dosage which distinguishes between “available chlorine” [(HOCl + ClO−) + (chlorine from isocyanurates, HnClmCyp−)] and “total chlorine”: absorption spectrophotometry after reaction with the N-diethylparaphenylenediamine (DPD). We adopted a common method for monitoring simultaneously, chlorine concentration and bacterial count. In this way, we studied the kinetics of selected bacteria inactivation, relative to H3Cy concentration and for different levels of available chlorine.
Article
Obtaining an accurate assessment of a treatment system's antimicrobial efficacy in recreational water is difficult given the large scale and high flow rates of the water systems. A laboratory test system was designed to mimic the water conditions and potential microbial contaminants found in swimming pools. This system was utilized to evaluate the performance of an in situ ozone disinfection device against four microorganisms: Cryptosporidium parvum, bacteriophage MS2, Enterococcus faecium, and Pseudomonas aeruginosa. The sampling regimen evaluated the antimicrobial effectiveness in a single pass fashion, with samples being evaluated initially after exposure to the ozone unit, as well as at points downstream from the device. Based on the flow dynamics and log reductions, cycle threshold (Ct) values were calculated. The observed organism log reductions were as follows: >6.7 log for E. faecium and P. aeruginosa; >5.9 log for bacteriophage MS2; and between 2.7 and 4.1 log for C. parvum. The efficacy results indicate that the test system effectively functions as a secondary disinfection system as defined by the Centers for Disease Control and Prevention's Model Aquatic Health Code.
Article
Cyanuric acid is used to stabilize free chlorine to reduce photodegradation in outdoor swimming pools. While there have been numerous studies examining its effect on the disinfection rates of bacteria and viruses, it is not known whether cyanuric acid can significantly impact the effectiveness of hyperchlorination for inactivating Cryptosporidium oocysts present in fecally-contaminated swimming pools. This study examined the effect of cyanuric acid on the disinfection rate of Cryptosporidium parvum under swimming pool hyperchlorination conditions (20 mg/ml free chlorine). When 50 mg/L cyanuric acid was present there was a 0.70-log10 reduction in oocyst viability after 10 hours as compared to a 3.7-log10 reduction without cyanuric acid. Aids to remediation, such as decreasing the pH to enhance the germicidal efficiency of the free chlorine and doubling the amount of free chlorine residual, were still unable to achieve a 3-log10 reduction. Current public health recommendations for hyperchlorination and pool remediation are insufficient for pools using cyanurate-stabilized chlorine to achieve a three log inactivation of the parasite.
Article
The inhibitory influence of cyanuric acid on the virucidal effect of chlorine was studied. The time required for 99.9% inactivation of ten enteroviruses and two adenoviruses by 0.5 mg/l free available chlorine at pH 7.0 and 25 degrees C was prolonged approximately 4.8-28.8 times by the addition of 30 mg/l cyanuric acid. Comparative inactivation of poliovirus 1 by free available chlorine with or without cyanuric acid revealed the following. The inactivation rate by 1.5 mg/l free available chlorine with 30 mg/l cyanuric acid or by 0.5 mg/l free available chlorine with 1 mg/l cyanuric acid was slower than by 0.5 mg/l free available chlorine alone. Temperature and pH did not affect the inhibitory influence of cyanuric acid on the disinfectant action of chlorine. In the swimming-pool and tap water, cyanuric acid delayed the virucidal effect of chlorine as much as in the 'clean' condition of chlorine-buffered distilled water. The available chlorine value should be increased to 1.5 mg/l when cyanuric acid is used in swimming-pool water.
Article
Techniques for culturing, harvesting, and testing bacteria to evaluate bactericidal chemicals for swimming pools are described. Concentrations of 25, 50, and 100 mg of the chlorine stabilizer cyanuric acid per liter increased the time required for a 99% kill of Streptococcus faecalis by 0.5 mg of chlorine per liter at pH 7.4 and 20 C from less than 0.25 min without cyanuric acid to 4, 6, and 12 min, respectively. The effect of concentrations of ammonia nitrogen in the range found in swimming pools on the rate of kill of 0.5 mg of chlorine per liter and of chlorine plus cyanuric acid was tested. At concentrations of ammonia nitrogen greater than 0.05 mg per liter, faster rates of kill of S. faecalis were obtained with 100 mg of cyanuric acid per liter plus 0.5 mg of chlorine per liter than with 0.5 mg of chlorine per liter alone. When water samples from four swimming pools with low ammonia levels were used as test media, 0.5 mg of added chlorine per liter killed 99.9% of the added S. faecalis in less than 2 min, but water from a pool with a large number of children required 60 to 180 min of treatment.
Article
Despite the evaluation of over 100 antimicrobial drugs, the diarrheal disease cryptosporidiosis has remained refractory to treatment. We report the evaluation of five dinitroaniline herbicides including trifluralin, profluralin, nitralin, pendimethalin, and fluchloralin for anticryptosporidial activity in an in vitro cultivation model of Cryptosporidium parvum. All five compounds exhibited significant anticryptosporidial activities with no corresponding evidence of toxicity. The most active compound was pendimethalin with an IC50 of 0.19 microM while nitralin was the least active with an IC50 of 4.5 microM. These compounds should be evaluated further in an animal model of cryptosporidiosis.
Article
Cryptosporidium is a chlorine-resistant protozoan parasite and the etiological agent in many disinfected recreational water outbreaks. While previous studies have reported disinfection Ct values for Cryptosporidium parvum using sodium hypochlorite, these studies have employed conditions and procedures which are not ideal for establishing public health remediation recommendations for chlorinated recreational water venues. In the present study, free chlorine Ct values were measured at pH 7.5 using young oocysts (<1 month old) and tissue culture to determine oocyst viability. Two different oocyst isolates were used: one originating from Iowa and one from Maine (USA). This study determined that the Ct values for a 3-log reduction in oocyst viability were 10,400 (Iowa) and 15,300 (Maine) at pH 7.5. These Ct values are higher than the Centers for Disease Control and Prevention (USA) currently recommends (Ct = 9,600) for achieving a 3.0-log inactivation of Cryptosporidium oocysts during remediation of recreational water venues following fecal diarrhea accidents.
An evaluation of the inhibitory influence of cyanuric acid upon swimming pool disinfection Virucidal effect of chlorinated water containing cyanuric acid The effect of cyanuric acid on the disinfection rate of Cryptosporidium parvum in 20-ppm free chlorine The Model Aquatic Health Code 1st Edition
  • E D Robinton
  • E W Mood
  • T Yamashita
  • K Sakae
  • Y Ishihara
  • S Isomura
  • H Inoue
  • V R Hill
  • M J Beach
Robinton, E. D.; Mood, E. W. An evaluation of the inhibitory influence of cyanuric acid upon swimming pool disinfection. Am. J. Public Health N 1967, 57 (2), 301−310. (10) Yamashita, T.; Sakae, K.; Ishihara, Y.; Isomura, S.; Inoue, H. Virucidal effect of chlorinated water containing cyanuric acid. Epidemiol. Infect. 1988, 101 (3), 631−639. (11) Shields, J. M.; Arrowood, M. J.; Hill, V. R.; Beach, M. J. The effect of cyanuric acid on the disinfection rate of Cryptosporidium parvum in 20-ppm free chlorine. J. Water Health 2009, 7 (1), 109− 114. (12) The Model Aquatic Health Code 1st Edition. August 2014. http://www.cdc.gov/healthywater/pdf/swimming/pools/mahc/ Complete-First-Edition-MAHC-Code.pdf (accessed: Jan. 21, 2015).
  • M C Hlavsa
  • V A Roberts
  • A M Kahler
  • E D Hilborn
  • T J Wade
  • L C Backer
Hlavsa, M. C.; Roberts, V. A.; Kahler, A. M.; Hilborn, E. D.; Wade, T. J.; Backer, L. C.; Yoder, J. S. Recreational Water-Associated Disease OutbreaksUnited States, 2009−2010. MMWR 2014, 63 (1), 6−10.
Equilibria in Aqueous Solutions of Chlorinated Isocyanurate Efficacy of chlorine dioxide tablets on inactivation of Cryptosporidium oocysts
  • O ' Brien
  • J E Morris
  • J C Butler
  • J N Rubin
O'Brien, J. E.; Morris, J. C.; Butler, J. N. Equilibria in Aqueous Solutions of Chlorinated Isocyanurate. In Chemistry of Water Supply, Treatment, and Distribution; Rubin, A. J., Ed.; Ann Arbor Science Publishers Inc.: Ann Arbor, MI, 1974; pp 333.358. (21) Murphy, J. L.; Haas, C. N.; Arrowood, M. J.; Hlavsa, M. C.; Beach, M. J.; Hill, V. R. Efficacy of chlorine dioxide tablets on inactivation of Cryptosporidium oocysts. Environ. Sci. Technol. 2014, 48, 5849−5856.
Notice to readers: Revised recommendations for responding to fecal accidents in disinfected swimming venues
Centers for Disease Control and Prevention..Notice to readers: Revised recommendations for responding to fecal accidents in disinfected swimming venues. MMWR 2008, 57 (6), 151−152.
Environmental Science & Technology Article DOI: 10.1021/acs.est.5b00962
Environmental Science & Technology Article DOI: 10.1021/acs.est.5b00962 Environ. Sci. Technol. 2015, 49, 7348−7355
  • J M Shields
  • V R Hill
  • M J Arrowood
  • M J Beach
Clin. Microbiol. Rev. 2002, 15 (3), 390−400. (14) Shields, J. M.; Hill, V. R.; Arrowood, M. J.; Beach, M. J.
  • M C Hlavsa
  • V A Roberts
  • A M Kahler
  • E D Hilborn
  • T J Wade
  • L C Backer
  • Yoder
Hlavsa, M. C.; Roberts, V. A.; Kahler, A. M.; Hilborn, E. D.; Wade, T. J.; Backer, L. C.; Yoder, J. S. Recreational Water-Associated Disease OutbreaksUnited States, 2009−2010. MMWR 2014, 63 (1), 6−10.
  • Arrowood M. J.