Fish and shellfish hygiene Flashcards
Causes of bivalve-associated illness
- Microbiological
○ Bacteria
○ Viruses
○ (Protozoa)- Biotoxins
○ Paralytic shellfish poisoning
○ Diarrhetic shellfish poisoning
○ Amnesic shellfish poisoning
○ Others - (Chemical contaminants)
○ Little evidence for acute effects - Allergies
- Biotoxins
How much can oysters filter
10-24L per hour
Bacteria causing bivalve-associated illness
Salmonella
Shigella
Vibrio
Campylobacter
Viruses causing bivalve-associated illness (5)
Norovirus
§ Relatively mild gastroenteritis, often including nausea, diarrhoea, vomiting, fever, and abdominal pain
§ Incubation period of 1 to 4 days, duration of about 2 days generally followed by complete recovery
§ The most common cause of infectious intestinal disease in outbreaks and in the community
Sapovirus
Astrovirus
Aichi virus
Hepatitis A virus
§ Extended incubation period of about 4 weeks (range 2-6)
§ Serious debilitating disease with fever, headache, nausea, vomiting, diarrhoea, abdominal pain, and jaundice
§ Self-limiting and rarely causes death, but patients may be incapacitated for several months
Protozoa causing bivalve-associated illness
Giardia
(? Cryptosporidium)
Pathogenic vibrios
Vibrios and human disease
○ Vibrios are a significant cause of seafood-associated illness worldwide
○ Three main species of interest are V. Cholerae, V. Parahaemolyticus, and V. Vulnificus
Foodborne infections
○ Primarily associated with consumption of raw bivalves
§ May also be associated with consumption of undercooked or re-contaminated bivalves
○ A proportion of cases also associated with consumption of crustacea (shrimps, crab, crayfish) or finfish
○ Relative trend in reported number of vibrio infections occurring annually in the USA, compared with that of other foodborne pathogens
Post-harvest processing
○ Purification - only about 40-50% of pathogenic vibrios removed at 48 hours
○ Other procedures
§ Pasteurisation
§ Freezing
§ Ultra-high pressure
Vibrio parahaemolyticus
Widely present in coastal and esturine environments
Causes gastro-enteritis
Ability to produce illness mainly associated with ability to produce certain haemolysins
§ Thermostable Direct Haemolysin (TDH) and TDH-related haemolysin (TRH)
§ E.g. In the USA, only 0.2-3.2% of environmental isolates are TDH +ve
Vibrio vulnificus
Causes primary septicaemia or wound infections
Infection via GI tract (raw oysters) or wounds
Death may occur within 2 days of start of symptoms
Predisposition by certain illnesses
What is the most common fish associated illness
Scombrotoxin