Calicivirus Inactivation by Nonionizing (253.7-Nanometer-Wavelength [UV]) and Ionizing (Gamma) Radiation

Abstract

Noroviruses (previously Norwalk-like viruses) are the most common viral agents associated with food-and waterborne outbreaks of gastroenteritis. In the absence of culture methods for noroviruses, animal caliciviruses were used as model viruses to study inactivation by nonionizing (253.7-nm-wavelength [UV]) and ionizing (gamma) radiation. Here, we studied the respiratory feline calicivirus (FeCV) and the presumed enteric canine calicivirus (CaCV) and compared them with the well-studied bacteriophage MS2. When UV irradiation was used, a 3-log 10 reduction was observed at a fluence of 120 J/m 2 in the FeCV suspension and at a fluence of 200 J/m 2 for CaCV; for the more resistant phage MS2 there was a 3-log 10 reduction at a fluence of 650 J/m 2 . Few or no differences were observed between levels of UV inactivation in high-and low-proteincontent virus stocks. In contrast, ionizing radiation could readily inactivate MS2 in water, and there was a 3-log 10 reduction at a dose of 100 Gy, although this did not occur when the phage was diluted in high-proteincontent stocks of CaCV or FeCV. The low-protein-content stocks showed 3-log 10 reductions at a dose of 500 Gy for FeCV and at a dose of 300 for CaCV. The inactivation rates for both caliciviruses with ionizing and nonionizing radiation were comparable but different from the inactivation rates for MS2. Although most FeCV and CaCV characteristics, such as overall particle and genome size and structure, are similar, the capsid sequences differ significantly, making it difficult to predict human norovirus inactivation. Adequate management of UV and gamma radiation processes for virus inactivation should limit public health risks.Human caliciviruses are the most important enteric agents of gastroenteritis in industrialized countries (13,17). Many waterborne outbreaks associated with noroviruses have been reported (1,3,5,10,15). Usually, epidemiological data prove that water was the common source for the outbreak, and in some molecular tracing studies norovirus strains were successfully identified in the source water and identical sequences were found in stools from patients (4,8,11,12,16). Virus concentrations in source water may peak with sewage overflow due to heavy rainfall or leaking septic tanks or pipes (2, 20). Breakdown or malfunctioning of water treatment plants may lead to insufficient reductions in virus concentrations in drinking water (20). Moreover, European legislation is mainly based on bacteriological quality parameters that determine fecal contamination of food and water. Viruses, however, are more resistant to treatment (9), are generally harder to detect, and exhibit lower dose-response relationships than bacteria. Therefore, water may meet microbiological safety guidelines but still pose a considerable health hazard.Irradiation treatment is being used more frequently for disinfection of food and water. Bacteriophages have been used as indicators for inactivation of viruses by ionizing and nonionizing radiation since bacteria are generally less resista...

Inactivation of a Human Norovirus Surrogate, Human Norovirus Virus-Like Particles, and Vesicular Stomatitis Virus by Gamma Irradiation

“…Previously, gamma irradiation of the other two human norovirus surrogates, feline calicivirus (FCV) and canine calicivirus (CaCV), has been reported (16). Surprisingly, a 3-log virus reduction at a very low dose of gamma irradiation (0.5 kGy for FCV and 0.3 kGy for CaCV) was observed (16). Based on our results, MNV-1 is much more resistant than FCV and CaCV to gamma irradiation.…”

“…Thus, the irradiation dose that normally would eliminate all pathogenic bacteria would not be sufficient to inactivate the norovirus surrogate. Previously, gamma irradiation of the other two human norovirus surrogates, feline calicivirus (FCV) and canine calicivirus (CaCV), has been reported (16). Surprisingly, a 3-log virus reduction at a very low dose of gamma irradiation (0.5 kGy for FCV and 0.3 kGy for CaCV) was observed (16).…”

“…Thus, survival studies of human norovirus must rely on suitable surrogates such as feline calicivirus (FCV) (16,60), canine calicivirus (CaCV) (16), and murine norovirus 1 (MNV-1) (4,13). It was reported that a 3-log virus reduction was observed in lowprotein-content solution at 0.5 kGy for FCV and 0.3 kGy for CaCV by gamma irradiation (16). It seems that these two surrogates were quite susceptible to gamma irradiation, or at least in low-protein-content solutions.…”

Induction of cell growth arrest by atmospheric non-thermal plasma in colorectal cancer cells

“…OH* can radiate near the UV wavelength of 300-350 nm, while O* can radiate visible light with a wavelength of 570-660 nm. However, it is well known that ultraviolet radiation with a range of 230-240 nm is the most effective in the biological system, and low-pressure mercury UV lamps (253.7 nm) are generally used in bacteria and organic cell treatment (De Roda Husman et al, 2004). Thus, plasma-induced radiation sources that are near UV (300-350 nm) and visible light (570-660 nm) may not be effective sources for apoptosis induction because the wavelengths from radicals are out of range for effective cell treatment.…”

Presence of Noroviruses and Other Enteric Viruses in Sewage and Surface Waters in The Netherlands

“…Bacteria are more readily inactivated by chlorination than are protozoa (49). Viruses are effectively removed or inactivated by slow sand filtration and soil passage, but they are more resistant to UV and coagulation combined with sedimentation (9,43,50). However, a very low concentration of virus may suffice to cause infection, e.g., from 10 to Ͻ10 4 norovirus PCR-detectable units (PDU), leading to gastrointestinal disease in two-thirds of the individuals infected (30).…”