Foodborne Viral Pathogens

Peter A. White, Natalie E. Netzler, Grant S. Hansman, Peter A. White, Natalie E. Netzler, Grant S. Hansman

• Publisher: CRC Press
• Year: 2016
• Print ISBN: 9781466579507
• eBook ISBN: 9781315392288
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Molecular Biology
• Index: Biological Sciences

Viral transmission through contaminated food and water claims hundreds of thousands of lives every year, particularly affecting children in developing nations. Foodborne viral pathogens are associated with gastroenteritis and hepatitis, causing widespread epidemics that affect all populations and demographics worldwide. Foodborne Viral Pathogens comprehensively covers the predominant etiological viral agents of foodborne disease, including norovirus, hepatitis A virus, hepatitis E virus, astrovirus, sapovirus and rotavirus, and several emerging viruses and prions. By improving food safety awareness and viral detection, and through promotion of global food safety standards, our ability to cope with and control foodborne disease will be enhanced.

Foodborne Viral Pathogens includes a detailed review of the molecular biology, potential vaccines, and available antiviral treatments of all major foodborne viral pathogens and prions. Written by specialists and leading virologists, this book features techniques used for typing, viral detection, strategies for control, and viral risk assessments. This book is intended as a detailed handbook for food microbiology and medical applications and will be a useful guide for anyone with an interest in foodborne disease.

Section II

Important Agents in Foodborne Viral Infections

6 Norovirus and Sapovirus

Kun Lee Lim, Natalie E. Netzler, Grant S. Hansman, Jason M. Mackenzie, and Peter A. White

CONTENTS

Norovirus

Introduction

History

Norovirus Is the Most Common Cause of Gastroenteritis

Rise of Norovirus

Norovirus Is the Dominant Cause of AGE in NSW, Australia

NoV Classification and Epidemiology

NoV Classification and Genetic Diversity

Molecular Epidemiology of NoV

Pandemic Noroviruses of the Genogroup II, Genotype 4 Lineage

Epidemic Noroviruses

Norovirus Structure and Genome Organization

NoV Nonstructural Proteins Involved in Genome Replication

NoV Structural Proteins

Replication and Life Cycle of NoV

NoV Binding and Cell Entry

Translation of Viral Proteins

Norovirus Evolution

Antigenic Variation NoV Evolution

RNA Recombination

Nomenclature of NoV Recombinants

Norovirus Clinical Disease

Pathogenesis

Immunity

Virus–Host Interaction and Innate Immunity

Host Susceptibility Factors

Transmission

Non-Foodborne Outbreak Settings

Norovirus Transmission from Food and Water

Transmission from Seafood

Norovirus Transmission from Food Handlers

Transmission from Contaminated Water

Transmission from Fresh Produce

NoV Prevention and Control

Vaccine Development

Norovirus: Conclusions

Sapovirus

Introduction

Classification and History

Genome Organization

Detection Methods

Pathogenesis and Clinical Manifestation

Environmental Persistence

Epidemiology

Transmission of Infection

Foodborne Transmission

Sapovirus: Conclusions

References

NOROVIRUS

Introduction

Human norovirus (NoV) is the leading cause of acute gastroenteritis (AGE) globally [1,2], and carries with it a large social and financial burden resulting from forced time off work, business closures, and hospitalizations [3]. Foodborne transmission is a key route for NoV infection, as the virus is spread rapidly via contaminated food handlers and food products. In many developed nations, NoV has been identified as the leading cause of foodborne disease, accounting for more than half of the cases of foodborne illness each year [4, 5, 6 and 7]. As the etiological agent responsible for the majority of foodborne illness (up to 80%) is never identified, estimates additionally attribute NoV with a large proportion of these unresolved cases [4].

NoV remains challenging to develop vaccinations against, with the virus continually mutating to evade herd immunity. Human NoV is also very difficult to culture in immortalized cells, severely hampering efforts to develop treatments and vaccines against the virus [8]. Without a reliable animal model to study human NoV directly, most studies rely on murine norovirus (MNV), a genogroup V NoV. MNV has been used to infer details of the infection cycle, including viral cell entry, and is frequently used to study aspects of NoV replication in both cell culture and in vivo mouse studies [9,10].

NoVs are classified within the Caliciviridae family and named after calyx (the Greek word for cup) because of the cuplike pattern on the virion surface [1]. Of the six Caliciviridae genera, NoV is attributed with the highest incidence of human disease [3]. Symptoms of NoV infection include vomiting and diarrhea, often accompanied by nausea, stomach cramps, malaise, and fever [11], which follow a relatively short incubation period of 24–48 h. Symptoms usually persist for 2–4 days in healthy adults [12], but infections can persist for months or even years in immunosuppressed or immunocompromised individuals [13, 14 and 15]. While the main route of NoV transmission is person-to-person [16], foodborne NoV is another significant route [3]. This section of the chapter reviews NoV and its transmission via contaminated food and water.

HISTORY

NoV was first described as hyperemesis hiemis or winter vomiting disease by Zahorsky in 1929 [17,18]. However, the disease was not fully understood at that time [19]. In the 1970s, several transmissibility studies in volunteer subjects who were orally administered stool filtrates obtained from infected patients showed that they developed similar gastroenteritis symptoms [20, 21 and 22]. These studies demonstrated that an unknown nonbacterial agent was the primary cause of transmissible AGE.

The original Norwalk virus was discovered in a fecal sample obtained from an AGE outbreak at an elementary school in Norwalk, Ohio, in 1968. The outbreak had a high attack rate of 50% (116 of 232) among the schoolchildren [23,24]. Norwalk virus, subsequently named after the town where it was found, is the prototype of the Norovirus genus. However, it took four more years before the actual physical virus particle was first visualized by Kapikian et al. in 1972 using electron microscopy (EM) [25].

Following the discovery of Norwalk virus, other similar viruses were subsequently detected and collectively termed Norwalk-like viruses (NLV) or small round structured viruses (SRSV) [26]. These viruses were typically named after the location where they were identified or by their appearance as visualized with EM [27,28]. Norwalk virus, the prototype NoV, is classified as NoV genogroup I, genotype 1 (GI.1). Complete sequencing and characterization of the Norwalk virus genome was accomplished by Jiang et al. in the early 1990s [29]. This achievement allowed further investigation into viral taxonomy using molecular techniques, including reverse transcription polymerase chain reaction (RT-PCR) and sequencing. In 2002, NLVs were collectively renamed as a single genus, Norovirus [30]. In summary, NoV-associated AGE with vomiting was recognized for many years before the actual virus was finally discovered. The true health burden of NoV has really only come to light in recent years.

NOROVIRUS IS THE MOST COMMON CAUSE OF GASTROENTERITIS

Rise of Norovirus

Historically, rotavirus (RoV) was reported as the major cause of diarrhea in children globally and was estimated to kill more than 440,000 children each year [31]. However, since 2006, the vaccines Rotarix (GlaxoSmithKline) and RotaTeq (Merck) have been introduced into the health-care programs of many countries. Following their inclusion, a dramatic decrease (~70%) in the incidence of RoV-associated AGE has been reported in these countries [32, 33, 34 and 35]. A similar trend has been seen in New South Wales (NSW), Australia, where the incidence of RoV infections decreased substantially following the introduction of the RoV vaccine in 2007, with the last major epidemic in 2005 (Figure 6.1).

FIGURE 6.1 Detection of enteric viruses at the South Eastern Area Laboratory Services (SEALS) diagnostic facility, Prince of Wales Hospital, Sydney, Australia. The monthly total positive stool specimens for norovirus (NoV), adenovirus (AdV), astrovirus (AsV), and rotavirus (RoV) detected in cases of acute gastroenteritis were evaluated between January 2004 and December 2010. Enzyme immunoassays (EIAs) were performed to detect viral antigens in stool specimens, and viruses are color-coded as per the legend. The RoV vaccine was introduced to the NSW health-care system in 2007 and has contributed to a dramatic decrease of RoV associated infections in subsequent years. (Adapted and modified from Eden, J.S., The Evolutionary Dynamics of Norovirus, UNSW Australia, 2012 [36].)

Norovirus Is the Dominant Cause of AGE in NSW, Australia

In Australia, the first NoV foodborne-associated outbreak was reported in 1978 and was linked to oyster consumption [37]. The etiological agent, NoV, was confirmed by visualization of virus particles in 39% of fecal specimens by EM and in 75% of samples by immune-EM [37].

To determine the role of NoV as an etiological agent of AGE, a total...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Preface
• Editors
• Contributors
• SECTION I New Technologies, Risk Assessment, and Strategies for Control of Viral Foodborne Illness
• SECTION II Important Agents in Foodborne Viral Infections