Chapter 10 Viruses in Shellfish

Abstract

This chapter describes the outbreak of nonbacterial gastroenteritis and infectious hepatitis has in association with shellfish consumption. These outbreaks were determined to be caused by viruses that either grew poorly in cell culture or cannot be cultivated at all, including hepatitis A virus (HAV) and noroviruses (NoVs). In many outbreaks, the shellfish and shellfish-growing waters met regulatory criteria for fecal-bacterial levels. The practice of depuration, a process by which shellfish purify themselves of enteric bacteria by filtering clean waters, failed to eliminate the risk of viral mediated diseases. A number of molecular methods have been described to detect viruses in bivalve molluscs. Many of these methods were adapted from methods to detect virus using different concentration/extraction methods, and the use of different RT-PCR assays. The initial steps consist of virus elution from shellfish tissues, recovery of viral particles, and then virus concentration. These approaches can be further subdivided based upon whether the whole shellfish or dissected tissues are analyzed. When whole shellfish are analyzed representing different numbers of individual shellfish depending on the species. This approach is particularly useful for small species, such as clams or cockles, because dissection may be technically difficult. Some methods have used acidic adsorption prior to virus elution.