Submitted to: Applied and Environmental Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/5/2013
Publication Date: 6/5/2013
Citation: Nair, C., Dancho, B.A., Kingsley, D.H., Calci, K., Meade, G.K., Mena, K.D., Pillai, S. 2013. Sensitivity of hepatitis A and murine norovirus to electron beam irradiation in oyster homogenates and whole oysters - quantifying the reduction in potential infection risks. Applied and Environmental Microbiology. 79:3796-3801. Interpretive Summary: This study evaluates the potential of electron beam technology to inactivate foodborne viruses within oysters. Electron beam (E-beam) is ionizing radiation generated from electricity rather than a radioactive source. Until this report, its potential for sanitizing raw shellfish had not been investigated. While a 10 fold reduction of a human norovirus surrogate and hepatitis A virus is demonstrated using E-beam on virus contaminated oysters, this reduction is judged to be insufficient to warrant the application of E beam as an intervention technology for shellfish that may be contaminated with norovirus or hepatitis A. This study does document the degree of virus inactivation that could be expect to occur concurrently if E-beam treatments were used as an intervention for pathogenic bacteria.
Technical Abstract: Despite worldwide regulations and advisories restricting shellfish harvest to approved locations, consumption of raw oysters continues to be an exposure route for human norovirus (NoV) and hepatitis A virus (HAV). Therefore, a technology that can reduce the public health risks is needed. The focus of this study was to evaluate the inactivation of HAV and the NoV research surrogate, murine norovirus 1 (MNV) in Eastern oysters (Crassostrea virginica) by high-energy electron beam (E beam) irradiation and to quantify the reduction of potential infection risks if this technology were as employed on oysters at varying virus contamination levels. The infection was quantified using a beta-Poisson model. The E beam dose required to reduce the MNV and HAV titer by 90% (D 10 value) in whole oysters was 4.05 and 4.83 kGy, respectively. The microbial risk assessment calculations suggests that if a typical serving of 12 raw oysters was contaminated with 100,000 PFU, a 5 kGy treatment would achieve a 12 percent and 15 percent reduction in NoV and HAV infections, respectively. If the serving size contained only 100 PFU, a 5 kGy treatment would achieve a 26 percent reduction of NoV and a 94 percent reduction of HAV. The study demonstrates that even if E beam processing was used on oysters, it would not completely eliminate the risk of viral illness, given the highly infectious nature of NoV and HAV, and the limited inactivation observed at the maximum United States FDA-approved dose of 5.5 kGy for oysters.