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Cryptosporidium is a waterborne pathogen that causes diarrhea in vertebrates and humans (mainly C. hominis and C. parvum). Ozone (O 3 ) is a powerful disinfectant due to its high oxidative characteristics, and it is used to inactivate microorganisms in drinking water. As an alternative to the gas dissolution system for producing ozone from oxygen, a simpler electrolytic ozone generation system has recently been developed. In the present study, the efficacy of the ozonated water produced by this system in inactivating Cryptosporidium parasites (C. parvum) was evaluated at different current intensities (which change the ozone concentrations) and short exposure times (15-60 s). Oocyst viability and integrity was assessed using vital dye staining, excystation assays, and scanning electron microscopy (SEM). SEM data revealed that oocyst walls were damaged by exposure to ozone molecules even at low concentrations (< 0.01 mg/l for 1 min) (current intensity 0.2 A), but that the excystation assay could not differentiate between deformed oocysts (dead) and partially excysted oocysts (alive). Exposure to ozonated water produced with a low current intensity (0.3 A) for 15 and 120 s resulted in the inactivation of 96.2% (CT value < 0.003) and 99.4% (CT value < 0.020) of the oocysts, respectively. Thus, it was estimated that a CT value more than 0.020 was required to inactivate > 99% of the C. parvum oocysts. These results suggested that the electrolytic ozone generation system may be more effective than gas dissolution ozone generation; however, further studies using additional approaches are needed to obtain clearer evidence., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Cryptosporidium spp. are protozoan parasites that are transmitted via fecal-oral routes and can exhibit chemical resistance. Chlorine resistance makes it very difficult to eliminate parasites present in contaminated drinking water. While the efficacy of ultraviolet light-emitting diodes (UV-LEDs) against microorganisms has been reported, the efficacy of UV-LEDs against Cryptosporidium spp. has not been fully evaluated. Here, we assessed the efficacy of UV-LEDs with peak wavelengths of 268, 275, 284, and 289 nm against Cryptosporidium parvum at various exposure times, with a fixed exposure distance, using two in vitro methods. Consequently, the time required for 2 log 10 inactivation through the excystation method by UV-LEDs of 268, 275, 284, and 289 nm was estimated as 115.5, 104.1, 37.4, and 30.7 min, respectively. The propidium iodide (PI) and 4',6-diamidino-2-phenylindole (DAPI) staining assays estimated the inactivation time as 311.3, 275.2, 60.6, and 39.1 min, respectively. Our results showed that UV-LED irradiation at longer wavelengths produced higher inactivation activity against C. parvum, which corroborates our previously reported in vivo assay results, although further study is needed to clarify the mechanism., (Copyright © 2022 Elsevier B.V. All rights reserved.)

As an alternative to using ultraviolet (UV) lamps, which are made with mercury that is toxic to the environment and human health, UV light-emitting diodes (UV-LEDs) are expected to be effective for inactivating microorganisms in water. Although UV-LEDs have been reported to be effective against bacteria and viruses, the effectiveness of UV-LEDs against Cryptosporidium parasites has not been fully evaluated. As we report here, we have developed an in vivo quantitative inactivation assay for C. parvum oocysts using immunodeficient mice. Using the assay, we evaluated the effectiveness of treatment by UV lamp (254 nm) at approximately 1000 μJ/cm 2 (for 3 s at a distance of 95 mm) compared to inactivation by commercially available UV-LEDs (with peak wavelengths of 268, 275, 284, and 289 nm). The shed patterns of oocysts after treatment with 284- and 289-nm wavelength UV-LEDs were significantly delayed compared to that after treatment with a UV lamp. These findings provide the first suggestion that UV-LEDs are effective against these parasites, as assessed using commercially available 350-mA UV-LEDs under conditions of fixed exposure distance and time., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflicts of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Cryptosporidium parvum is a parasitic protozoan that causes the diarrheal disease cryptosporidiosis, for which no satisfactory chemotherapy is currently available. Although the presence of mitochondria in this parasite has been suggested, its respiratory system is poorly understood due to difficulties in performing biochemical analyses. In order to better understand the respiratory chain of C. parvum, we surveyed its genomic DNA database in GenBank and identified a partial sequence encoding cyanide-insensitive alternative oxidase (AOX). Based on this sequence, we cloned C. parvum AOX (CpAOX) cDNA from the phylum apicomplexa for the first time. The deduced amino acid sequence (335 a.a.) of CpAOX contains diiron coordination motifs (-E-, -EXXH-) that are conserved among AOXs. Phylogenetic analysis suggested that CpAOX is a mitochondrial-type AOX, possibly derived from mitochondrial endosymbiont gene transfer. The recombinant enzyme expressed in Escherichia coli showed quinol oxidase activity. This activity was insensitive to cyanide and highly sensitive to ascofuranone, a specific inhibitor of trypanosome AOX.