L34: Fish and shellfish hygiene Flashcards
What is the usual toxin in fish?
Scombrotoxin
What are the usual viruses in bivalves?
Norovirus or astrovirus
WHat are the scombroid fish?
Tuna, mackerel, herring
How does histamine form in fish?
Gram -ve bacteria convert histidine to histamine
How soon do you get illness after histamine?
10 min - 2 hours
What is primary control measure against histamine?
Rapid cooling after harvest
Below what temp can Listeria grow?
5 degrees
Which kind of seafood is associated with Listeria outbreaks?
Smoked
Which kind of fish is botulism associated with?
Fin fish
How can fermented whole fish cause botulism?
NaCl too low
What is the definitive host of nematodes?
Marine mammals
How do nematodes cause disease in humans?
Dies causing inflammation
What is the definitive host of cestodes and trematodes?
Humans
What must happen to fish products intended to be eaten raw?
Frozen
What does freezing fish not prevent?
Allergic reactions to larval proteins
What temperature and for how long must fish be frozen?
-20 for 24 hours or -35 for 15 hours
Which effect may possibly allow pathogenic vibrio spread?
El nino
What is the problem with the estuaries/inlets used for shellfish cultivation?
Also used for sewage disposal
What three diseases can biotoxins cause?
Paralytic, diarrhetic, amnesic shellfish poisoning
WHich kind of shellfish poisoning is neurotoxic?
Paralytic
Which kind of shellfish poisoning is neurotoxic?
Amnesic
What is norovirus incubation like compared to bacteria?
Longer
What is norovirus immunity like?
None - can mutate rapidly
Why do oysters have more microbiological issues?
Consumed raw
Why does norovirus peak in winter in bivalves?
In sewage in winter and taken up
Whick kind of microorganisms are not present in animal waste contamination?
Viruses
What are the four types of bivalve harvesting areas?
A, B, C, prohibited
What does the bivalve risk assessment assess?
Faecal contamination in the area
What are G1 norovirus levels like compared to G2, especially in which season?
Lower, esp in winter
What is correlation between E Coli and norovirus like in individual samples?
Lack
What is correlation between E Coli and norovirus like on a site by site basis in winter?
Better/best
What is depuration?
Bivalve purification in seawater
What is removed rapidly during depuration?
E Coli
What is hardly removed at all in depuration?
Norovirus
Which is the only part of the chain that does not have HACCP?
Primary production
What is traceability of bivalves like?
Registration document at harvest, ID on packet
How many main species of Vibrios are there?
Three
What % of pathogenic Vibrios are removed at depuration?
40-50%
Which Vibrios contaminate seafood, esp raw/undercooked bivalves?
Vulnificus and parahaemolyticus
How quickly does death occur following Vibrios?
2 days
How does Vulnificus contamination occur?
Via GI tract or wounds
What does vulnificus cause in humans?
Primary septicaemia or wound infections
WHich people are especially affected by vulnificus?
Older men with liver problems
What does parahaemolyticus risk depend on?
Unrefrigerated time because rapid proliferation
Which parahaemolyticus strains cause gastroenteritis?
Those with haemolytic activity
