Bacterial Pathogens, Mycotoxins, Viruses, Parasites, and Fish Toxins ◾ 391
matter. Vegetables (salads) can be contaminated with polluted water. Shellfish (oysters, clams,
mussels, and cockles) harvested from water polluted with sewage and eaten raw or improperly
heated before eating have been implicated in many outbreaks of both types of viruses. The virus
can survive in shellfish for a long time. Depuration (in tanks filled with disinfected saline water)
or relaying (kept in unpolluted water in the sea) for self-cleaning of the viruses from the digestive tracts of the shellfish may not be very effective for hepatitis A or NoV. In the United States,
the major cause of foodborne viral disease outbreaks is the contamination of ready-to-eat foods
because of poor personal hygiene and contaminated equipment used with foods served at delicatessens, cafeterias, and restaurants.
Prevention
The two major preventative methods of foodborne virus infections are to kill the viruses in contaminated foods and to adopt good sanitation and personal hygiene habits to control contamination. Proper heat treatment, such as pasteurization, is enough to kill the viruses. Steaming lightly
to open the shellfish may not be an effective heat-treatment procedure. Hydrostatic pressure processing, currently being used to open the shellfish, can also destroy the viruses if the pressure used
is above 300 MPa. As indicated before, depuration and relaying may not be effective. Sanitation,
using oxidative agents, such as hypochlorite, can kill viruses in contaminated equipment or in
water used in food processing. Good personal hygiene and keeping suspected individuals away
from handling ready-to-eat foods will also be important to control viral foodborne infections.
Vaccination against hepatitis A is available and is used to control the disease.
Detection Methods 6
Because enteric viruses do not multiply in food and are usually present in food in relatively low
numbers, their detection from a contaminated food poses difficulties. Initially, the viruses are concentrated from a suspected food. For identification of hepatitis A virus, specific cell culture procedures and immunological methods have been developed. The reverse transcription-polymerase
chain reaction (RT-PCR) nucleic acid amplification method is effective in detecting both hepatitis
A and NoVs and is commonly used. In one such method, the viral RNA is amplified with hepatitis
A or Norovirus-specific primers by RT-PCR, using a viral RNA internal standard control. By this
method, a total of 10 2–3 viruses were detected in suspected food samples (e.g., ham, turkey, and
roast beef). Enzyme immunoassays (EIA) are also used using antibodies to viral capsid proteins
and now genome sequencing is used for identification.
Norovirus 8–10
Norovirus (NoV) infection is characterized by self-limiting vomiting and diarrhea and occurs
all year round but peaks in winter months. It was originally isolated from an outbreak in school
children in Norwalk, Ohio (USA) in 1968, and the virus was not identified until 1972 by Dr.
Albert Z. Kapikian who named it “Norwalk virus.” Now it is called norovirus. Norovirus cases
cause approximately 21 million illnesses annually in the United States. It is a nonenveloped virus
with an icosahedral symmetric structure and is very small (27–38 nm). It is a single-stranded RNA
virus and belongs to the family of Caliciviridae. Norovirus has been grouped into five genogroups
(GI-GV), and genogroups GI, GII, and GIV are known to infect humans. The method to cultivate
matter. Vegetables (salads) can be contaminated with polluted water. Shellfish (oysters, clams,
mussels, and cockles) harvested from water polluted with sewage and eaten raw or improperly
heated before eating have been implicated in many outbreaks of both types of viruses. The virus
can survive in shellfish for a long time. Depuration (in tanks filled with disinfected saline water)
or relaying (kept in unpolluted water in the sea) for self-cleaning of the viruses from the digestive tracts of the shellfish may not be very effective for hepatitis A or NoV. In the United States,
the major cause of foodborne viral disease outbreaks is the contamination of ready-to-eat foods
because of poor personal hygiene and contaminated equipment used with foods served at delicatessens, cafeterias, and restaurants.
Prevention
The two major preventative methods of foodborne virus infections are to kill the viruses in contaminated foods and to adopt good sanitation and personal hygiene habits to control contamination. Proper heat treatment, such as pasteurization, is enough to kill the viruses. Steaming lightly
to open the shellfish may not be an effective heat-treatment procedure. Hydrostatic pressure processing, currently being used to open the shellfish, can also destroy the viruses if the pressure used
is above 300 MPa. As indicated before, depuration and relaying may not be effective. Sanitation,
using oxidative agents, such as hypochlorite, can kill viruses in contaminated equipment or in
water used in food processing. Good personal hygiene and keeping suspected individuals away
from handling ready-to-eat foods will also be important to control viral foodborne infections.
Vaccination against hepatitis A is available and is used to control the disease.
Detection Methods 6
Because enteric viruses do not multiply in food and are usually present in food in relatively low
numbers, their detection from a contaminated food poses difficulties. Initially, the viruses are concentrated from a suspected food. For identification of hepatitis A virus, specific cell culture procedures and immunological methods have been developed. The reverse transcription-polymerase
chain reaction (RT-PCR) nucleic acid amplification method is effective in detecting both hepatitis
A and NoVs and is commonly used. In one such method, the viral RNA is amplified with hepatitis
A or Norovirus-specific primers by RT-PCR, using a viral RNA internal standard control. By this
method, a total of 10 2–3 viruses were detected in suspected food samples (e.g., ham, turkey, and
roast beef). Enzyme immunoassays (EIA) are also used using antibodies to viral capsid proteins
and now genome sequencing is used for identification.
Norovirus 8–10
Norovirus (NoV) infection is characterized by self-limiting vomiting and diarrhea and occurs
all year round but peaks in winter months. It was originally isolated from an outbreak in school
children in Norwalk, Ohio (USA) in 1968, and the virus was not identified until 1972 by Dr.
Albert Z. Kapikian who named it “Norwalk virus.” Now it is called norovirus. Norovirus cases
cause approximately 21 million illnesses annually in the United States. It is a nonenveloped virus
with an icosahedral symmetric structure and is very small (27–38 nm). It is a single-stranded RNA
virus and belongs to the family of Caliciviridae. Norovirus has been grouped into five genogroups
(GI-GV), and genogroups GI, GII, and GIV are known to infect humans. The method to cultivate