Effect of UV Light on the Inactivation of Recombinant Human Adenovirus and Murine Norovirus Seeded in Seawater in Shellfish Depuration Tanks

Abstract

Shellfish depuration is a process that aims to eliminate pathogens from mollusk tissues. Seawater disinfection during the depuration process is important and ultraviolet (UV) light treatment is the most used method worldwide. Viral models are usually employed as surrogates of fastidious viruses in viability studies. The aim of this study was to employ methods based on green fluorescent protein (GFP) fluorescence and plaque forming units to detect, respectively, recombinant adenovirus (rAdV-GFP) and murine norovirus (MNV) artificially seeded in environmental matrices. These assays were applied to assess the inactivation of rAdV-GFP and MNV in seawater in recirculation shellfish depuration tanks with and without UV light treatment. Kinetics of rAdV GFP-expression was previously measured by UV-spectrophotometer. Flow cytometry (FC), fluorescence microscopy (FM), and plaque assay were used to determine virus titer and detection limits. The influence of the environmental matrix on the performance of the methods was prior determined using either drinking water or filtered seawater seeded with rAdV-GFP. Disinfection of seeded seawater was evaluated with and without UV treatment. The time of 24-h post-infection was established as ideal for fluorescence detection on rAdV-GFP infected cells. FC showed lower sensitivity, when compared to FM, which was similar to plaque assay. Seawater disinfection on depuration tanks was promising and rAdV-GFP declined 99.99 % after 24 and 48 h with and without UV treatment, respectively. MNV was completely inactivated after 24 h in both treatments. As conclusion, the depuration tanks were effective to inactivate rAdV-GFP and MNV and the UV disinfection treatment accelerated the process.

Critical Review on the Public Health Impact of Norovirus Contamination in Shellfish and the Environment: A UK Perspective

“…Using an animal cell line assay, UV treatment has been shown to reduce NoV surrogates to non-infectious levels (Garcia et al 2015; Neish 2013). Typically, however, water temperature was elevated in these experiments and therefore the relevance to human infectivity is thought to be limited (Cook et al 2015).…”

Thermal Inactivation of Enteric Viruses and Bioaccumulation of Enteric Foodborne Viruses in Live Oysters (Crassostrea virginica)

“…Historically, these standards (27)(28)(29)(30) have succeeded in reducing many types of shellfishrelated bacterial outbreaks; however, it has been shown that the bacterial standards are inadequate for estimating the presence of enteric viruses in shellfish and growing waters. Moreover, the depuration process for shellfish harvested from conditionally approved (or category B) growing areas has been shown to be less effective at eliminating enteric viruses than bacteria from contaminated shellfish (31)(32)(33). Therefore, it is necessary to understand the interaction of viruses and shellfish and also to develop efficient methods for inactivating/removing the viruses from this food commodity.…”

Research Progress in Viral Inactivation Utilizing Human Norovirus Surrogates

“…UV light treatment has historically been widely utilized by water treatment plants, has also been used for seawater disinfection in depuration tanks (Garcia et al, 2014). Depuration is a process where specific organisms (in this case bivalve mollusks) are placed into a large area or tank of clean water to allow for expulsion and diffusion/removal of any contaminants that may have been present on the organism (in this case viruses) to be removed.…”

“…This is particularly relevant, as molluscan shellfish are a leading food implicated in human norovirus illness. Garcia et al (2014) investigated the ability of UV to reduce MNV and recombinant human adenovirus artificially seeded into depuration water. Water samples were taken after the treatment and prior to further chemical disinfection (without residual free chlorine).…”

“…More reduction of MNV was observed than adenovirus after 24 and 48 h of treatment, however the treatment was quite effective overall. There was a 4 log reduction of adenovirus and MNV had reached undetectable limits (>6 log reduction) after 24 h, with adenovirus being reduced to the same levels after 48 h (Garcia et al, 2014). Park et al (2016a) investigated the effects of different variables of UV wavelength and photocatalysis on inactivation of MNV.…”