Foodborne Viral Infections

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Questions and Answers

What is the primary source of enteric viruses that contaminate food?

Animals consuming contaminated water

Pest infestations

Human feces (correct)

Contaminated soil

What is the current status of cultivating Norwalk-like viruses in cell cultures?

It is still in the experimental stage

It is not possible to cultivate NLVs in cell cultures

The method has not yet been successful (correct)

It has been successfully achieved

What is the main source of both hepatitis A and NLV outbreaks?

Food contaminated with fecal matter of infected people (correct)

Poor personal hygiene

Infected food handlers with symptoms

Contaminated water

What is the minimum dose level required for enteric viruses to cause infection?

Low dose level Signup and view all the answers

What is the ranking of viral foodborne infection in terms of the number of cases affected in the US between 1986 and 1987?

Third Signup and view all the answers

How long can NLV symptoms last?

1 to 2 days Signup and view all the answers

What is the purpose of pasteurization in preventing foodborne virus infections?

To kill the viruses in contaminated foods Signup and view all the answers

What is the effect of pasteurization on enteric viruses?

It can effectively kill the enteric viruses Signup and view all the answers

Why are shellfish implicated in many outbreaks of both types of viruses?

Because they are harvested from water polluted with sewage Signup and view all the answers

What is unique about hepatitis A virus compared to Norwalk-like viruses?

HAV can be grown in cell cultures, but NLVs cannot Signup and view all the answers

What is the size range of hepatitis A and Norwalk-like viruses?

27-28 nm Signup and view all the answers

When do symptoms of hepatitis A typically occur?

After 4 weeks, with a range of 2 to 7 weeks Signup and view all the answers

What may or may not occur after ingesting hepatitis A viruses through contaminated food or other sources?

An individual may or may not develop symptoms Signup and view all the answers

What is a major preventative method of foodborne virus infections?

Killing the viruses in contaminated foods Signup and view all the answers

How are NLVs typically transmitted?

Through contaminated food and water Signup and view all the answers

What is the purpose of using oxidative agents such as hypochlorite?

To kill viruses in contaminated equipment or in water Signup and view all the answers

In what year was Vibrio parahaemolyticus first recognized as a foodborne pathogen in the U.S.?

1971 Signup and view all the answers

What is the optimal temperature range for the growth of Vibrio parahaemolyticus?

30 to 37oC Signup and view all the answers

What is the characteristic of Vibrio parahaemolyticus that makes it sensitive to drying?

It is extremely sensitive to drying Signup and view all the answers

What is the name of the toxin produced by Vibrio parahaemolyticus?

Thermostable direct hemolysin (TDH) Signup and view all the answers

What is the characteristic of Vibrio parahaemolyticus that allows it to grow in the presence of salt?

It is halophilic Signup and view all the answers

What is the seasonal variation of Vibrio parahaemolyticus in estuarine environments?

It is present in higher numbers during summer months Signup and view all the answers

What is the characteristic of Vibrio parahaemolyticus that makes it vulnerable to pasteurization?

It is sensitive to heat Signup and view all the answers

What is the characteristic of Kanagawa-positive strains of Vibrio parahaemolyticus?

They can cause hemolysis Signup and view all the answers

Study Notes

Viral Foodborne Infections

Viral foodborne infections are rarely examined for contamination, but they were the fifth leading cause of foodborne disease outbreaks in the US between 1973 and 1987.
Between 1986 and 1987, viral infections ranked third in the number of cases affected by foodborne disease outbreaks.
Hepatitis A and Norwalk-like viruses are the most commonly associated viruses with foodborne infections.

Characteristics of Viral Infections

Foodborne viral infections can only occur from enteric pathogenic human viruses.
Hepatitis A and Norwalk-like viruses are small RNA viruses, with sizes of 27-28 nm.
Hepatitis A viruses can be grown in cell cultures and used to produce vaccines, while Norwalk-like viruses have not been successfully cultivated in cell cultures.

Habitat of Viral Infections

Enteric viruses are excreted in high numbers in human feces and do not multiply outside the human body, including contaminated foods.
Pasteurization can effectively kill enteric viruses.

Disease and Symptoms of Viral Infections

Enteric viruses can cause infection at a low dose level.
Symptoms of hepatitis A virus infection occur 2-7 weeks after ingestion and include fever, malaise, nausea, vomiting, abdominal discomfort, and liver inflammation.
Symptoms of Norwalk-like virus infection appear 12-24 hours after ingestion and include vomiting and diarrhea.

Food Association of Viral Infections

Food contaminated with fecal matter of infected people, either directly or indirectly, is the main source of viral outbreaks.
Infected food handlers, even without symptoms, can contaminate ready-to-eat food with fecal matter.
Shellfish harvested from polluted water and eaten raw or improperly heated have been implicated in many outbreaks.

Prevention of Viral Infections

Killing viruses in contaminated foods through proper heat treatment, such as pasteurization, is a major preventative method.
Good sanitation and personal hygiene habits, such as washing hands, can control contamination.
Keeping suspected individuals away from handling ready-to-eat food can also prevent viral infections.

Vibrio parahaemolyticus

Vibrio parahaemolyticus are Gram-negative, nonsporulating, motile, curved rods that are catalase and oxidase positive.
They grow in a medium containing glucose without producing gas, but are unable to ferment lactose and sucrose.

Habitat of Vibrio parahaemolyticus

Vibrio parahaemolyticus strains are halophilic bacteria distributed in coastal waters worldwide, with a seasonal variation and highest numbers during the summer months.

Toxin and Toxin Production of Vibrio parahaemolyticus

Not all strains of Vibrio parahaemolyticus are pathogenic, but foodborne pathogenic strains can cause hemolysis due to the presence of a heat-stable hemolysin (thermostable direct hemolysin, TDH).

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Description

This quiz covers the importance of examining food for contamination by enteric viruses, and the prevalence of viral foodborne infections in the US.