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Public health risks from fish and fish products
Scottish Food Enforcement Officers
Craig Burton
Perth
April 08
Potential hazards
• Potential public health risks can arise from
– Toxins
– Parasites
– Xenobiotes (Man-made substances)
Definitions
• Toxin
– A poisonous substance produced by an organism
• Parasite
– An organism that lives on or in another and derives nutrition
from the host with a detrimental effect on the host.
• Xenobiote
– A substance that is not of biological origin found in the
ecosystem or body
Fish toxins
• 3 main toxins and several minor ones
– Ciguatera
– Tetrodotoxin
– Scombroid poisoning
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Clupeoid fish poisoning
Gempylid poisoning
Hallucinatory fish poisoning
Ichthyohaemotoxic poisoning
Ichthyohepatotoxic poisoning
Ichthyootoxic poisoning
Elasmobranch poisoning
Ciguatera
• Most serious toxin world-wide and commonest
• Mainly tropics and sub-tropics
– Between 35o N and 35o S
• Mainly reef fish species – 400 species implicated
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Barracuda
Grouper
Snapper
Sea Bass
Coral Trout
Rock Cod
Jacks / Tevally
Parrot Fish
Moray Eel
Ciguatera
• No external indication of toxicity
• Heat stable
• Possible 5 toxins involved
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Ciguatoxin
Maitotoxin
Scaritoxin
Palytoxin
Okadic acid
• Cause – dinoflagellates (Gambierdiscus toxicus)
Ciguatera
• Symptoms:
– Various, 2 – 12 hours after ingestion
– Gastro-intestinal (nausea, vomiting, cramps, diarrhoea)
– Cadiovascular (hypotension, tachycardia, bradycardia)
– Neurological (headache, joint pain, delirium, paralysis, coma)
– Sensation (itch, burning, numbness, tingling,
– Skin lesions
• Can be fatal (0.1 - 10%)
dysaesthesia)
Ciguatera
• Can be treated
– Treat symptoms and provide support
• Best tactic – Avoidance
– Be cautious of large reef fish – especially
predators
– Do not eat fish liver, gonads or intestines
– Caution if evidence of algal blooms
– Sale of some fish species banned in some areas /
seasons
Tetrodotoxin
• Most famous fish toxin
• Japanese ‘Fugu’
• Toxin found in
– Puffer Fish
– Ocean Sunfish
– Porcupine Fish
• Occurs in
– Ovaries
– Liver
– Intestines
Tetrodotoxin
• Heat stable
• Slightly water soluble
• Neurotoxin
– 65 mg lethal
– Has medical uses as a pain killer
• Symptoms: 5 – 40 minutes (to 3 hours)
– General (weak, pale, dizzy, unco-ordinated, salivation, sweating)
– Neurological (numbness, paraesthesia, muscle twitching, paralysis)
– Gastro-intestinal (nausea, vomiting, diarrhoea, pain)
– Cardiovascular (chest pain, irregular pulse, hypotension)
Tetrodotoxin
• Treatment
– Respiratory support and general care
– Can improve rapidly
– Full resolution
• Can be fatal (up to 60% if untreated and can kill in
17 mins)
Scombroid toxin
• Fish spoilage problem
• Associated with
– Tuna (all species)
– Mackerels (all species)
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Herring
Sardine
Anchovy
Bluefish
Amberjack
Kingfish
Scombroid toxin
• Cause
– Fish treated incorrectly after capture or during storage
– Left in the sun
– Kept at room temperature for hours
• What happens
– Bacteria (Proteus, Clostridium, Salmonella, Klebsicila, Escherichia)
convert Histidine in the muscles to Suarine (histamine-like)
Scombroid toxin
• External Indication
– Fish taste sharp, bitter or peppery
• Laboratory confirmation
– Histamine > 100 µM (mg) per 100 g fish muscle
(Codex Std < 20 mg 100g-1)
Scombroid toxin
• Symptoms: 20 – 60 mins
– General (dry mouth, thirst, burning throat, cannot swallow, headache,
metallic taste, weakness, pain, fever)
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Gastro-intestinal (nausea, vomiting, diarrhoea, cramps)
Cardiovascular (palpitations, tachycardia, hypotension, ST depression)
Skin (general redness, itching, urticaria)
Respiration (bronchospasm, distress, cyanosis)
Scombroid toxin
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Often mistaken for fish allergy
Treat with anti-histamines (steroids)
Rarely fatal
Usually resolves 12 – 16 h, but can last days
Rarer toxins
• Clupeoid fish poisoning
– Anchovy
– Herring
– Sardine
– Rapid onset (minutes)
– Often fatal
– Liver failure (if survive)
– Possibly related to Ciguatera poisoning
• Gempylid poisoning
– Escolars and pelagic mackerels
– Diarrhoea
Rarer toxins
• Hallucinatory fish poisoning
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Mullet
Goatfish
Drummers
Rockcod
Surgeon fish
Rare and localised
Heat stable
Rapid onset - < 2 h
Symptoms
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Impaired consciousness
Hallucination
Bizarre dreams
Paranoia
– Resolves < 24 h
Rarer toxins
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Ichthyohaemotoxic poisoning
– Drinking fish blood, especially freshwater eels
– Heat labile, protein-bound
– Symptoms
– Gastro-intestinal (nausea, vomiting, pain)
– Neurological (numbness, weakness, paralysis)
– Can be fatal
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Ichthyohepatotoxic poisoning
– Eating fish livers (tuna, mackerel, bass, grouper, snapper, sandfish)
– Like vitamin A overdose
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Ichthyootoxic poisoning
– Eating fish eggs / roe (eg Barbel roe, but can affect caviar by bacterial spoilage)
– Rare
– Symptoms
– Gastro-intestinal (nausea, vomiting, diarrhoea)
– Neurological (tinnitus, respiratory distress, coma)
– General (dry mouth)
– Resolves in days
Rarer toxins
• Elasmobranch poisoning
– Associated with eating sharks and rays
– Often from liver and gonads (but also in muscle)
– Heat stable
– Water soluble
– Symptoms
– Gastro-intestinal (nausea, vomiting, diarrhoea, pain)
– Neurological (numbness, tingling, weakness, visual, paralysis,
delirium, coma)
– Cardiovascular (tachycardia, thready pulse)
– Skin (itchy, peel off)
– General (headache, pain, prostration)
– Can be fatal
– Recovery 5 - 20 days
Parasites
• Affect freshwater and marine fish
• 76 recognised pathogenic species
• 3 main groups:
– Nematodes (Round worms)
– Trematodes (Flukes)
– Cestodes (Tape worms)
• Also
– Acanthocephala
Parasites
• Problems mainly associated with raw or lightly
processed fish
• Typical ‘risk’ dishes
– Raw fish (eg Sashimi, Sushi)
– Cold-smoked fish
– Lightly salted (cured) fish (eg Gravfisk)
– Pickled fish (eg Roll-mop herring)
– Marinated fish
– Undercooked fish
Parasites
• Penetrate human gut if ingested
– Inflammation
– Ulceration
– Granuloma formation
– Can migrate to other organs (serious)
• Infection rare in UK
(but 40 – 50 million people (5-7%) affected world-wide, mainly Asia)
• Can be of short duration (days) or can be chronic
(decades)
Nematodes (Round worms)
• Main condition
– Anisakiasis (eosinophilic phlegmonous enteritis, eosinophilic
granuloma)
• Main causal agents
– Herring Worm (Anisakis simplex)
– Cod Worm (Pseudoterranova decipiens)
– Eustrongylides spp
– Gnathostoma sprinigerum (FW - Thailand)
– Angiostrongylus cantonensis (FW)
• Worms mainly found in fish gut, but move to muscle
tissue after death
Nematodes
• Symptoms (within hours)
– Abdominal pain
– Nausea
– Vomiting
– May cough up larvae
– After 1-2 weeks, mimics Crohn’s disease (IBS)
– Other (more serious) if migration to other organs
– Brain
– Heart
– Lungs
Nematodes
• Common fish hosts
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Herring
Cod
Pollock
Haddock
Alaskan pollock
Mackerel
Anchovy
Tuna
Salmon
Squid
Trematodes (Flukes)
• Fish are intermediate host
• Several genera can infect humans
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Heterophyes spp
Microphallus spp
Nanophyetus spp
Opisthorchis spp
Chlonorchis spp
Metagonimus spp
Paragonimus spp (crustacea)
Trematodes
• Symptoms
– Depends on main site of infection of fluke
– Liver flukes
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– Chlonorchis spp
– Opisthorchis spp
Abdominal pain
Nausea
Diarrhoea / Constipation
Eosinophilia
– Cholangitis
– Cholelithiasis
– Pancreatitis
– Cholangiocarcinoma
– Heptamegaly
– Malnutrition
Trematodes
• Symptoms
– Intestinal flukes
– Heterophyes spp
– Metagonimus spp
– Abdominal pain
– Diarrhoea
– Heart (muscle and valves)
– Brain
Trematodes
• Symptoms
– Lung flukes
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– Paragonimus spp
Abdominal pain
Diarrhoea
Fever
Cough
Urticaria
Hepatospleanomegaly
Lung abnormality
Eosinophilia
– Cough
– Expectoration
– Haemoptysis
– Brain
– Other organs
Trematodes
• Symptoms
– Other “fish flu”
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– Nanophyetus spp
Abdominal discomfort
Diarrhoea
Nausea
Fatigue
Weight loss
Eosinophilia
Trematodes
• Common fish hosts
– Mullet (Mugil spp)
– Sea Bass (Dicentrarchus spp)
– Herring
– Salmonids
– Tilapia
– FW fish (carps)
Cestodes (Tape worms)
• Fish are intermediate host
• Main concern 2 genera
– Diplogonoporus spp
– Diphyllobothrium spp
– Diphyllobothrium latum
– Broad tapeworm
– Human optimum host
– Grows to 10 m
– Long lived (decades)
Cestodes
• Symptoms
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Can be none (asymptomatic)
Abdominal discomfort
Diarrhoea
Vomiting
Weight loss
Vitamin B12 deficiency
Pernicious anaemia
Intestinal obstruction
Cestodes
• Common fish hosts
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Pike
Perch
Burbot
Salmonids
Drums (Serranids)
Blue Whiting
Anchovy
Sardine
Turbot
Prevention of parasite infection
• Freeze fish
– EU requirement (853/2004)
– Freeze to -20oC for 24 h
– Other advice (FDA)
– Blast freeze to -35oC for 15 h
– Freeze to -23oC for 168 h
– Freeze or store at -20oC for minimum of 7 d
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Cook fish to > 60oC throughout depth
Candling and removal (minimise risk)
Belly flap removal (minimise risk)
Gut at sea or as kill (and cure) can reduce risk
Xenobiotes
• Several non-biological substances of health concern
can occur in fish and fish products
– From the environment
– Hydrocarbons
– Persistent Organic Pollutants (Dioxins, Polychlorinated
biphenols [PCB], Organophosphates, Organochlorides)
– Polycyclic Aromatic Hydrocarbons (PAH)
– Heavy metals (Pb, Hg (CH3-Hg), Cd etc)
– Radionucleotides
– Synthetic hormones (freshwater)
Xenobiotes
– From direct intervention
– Veterinary medicine residues (aquaculture)
– Polycyclic Aromatic Hydrocarbons (PAH) (processing)
– Colourants (processing)
Xenobiotes
• Some have permitted maximum levels set in
legislation
– International (Codex Alimetarius)
– European (1881/2006, 2377/90, 94/36/EC)
– UK (Contaminants in Food Regs 2007)
• UK fisheries and aquaculture monitored
• Imports should be certificated
(EU approved residue monitoring plan in export country)
Thank you.
Enjoy your fish!
Craig Burton
[email protected]
01967 431573
07876 035771 (Mobile)