Public health risks from fish and fish products

Craig Burton

Scottish Food Enforcement Officers

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

– 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

– 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

– 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, dysaesthesia)

– Skin lesions

• Can be fatal (0.1 - 10%)

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)

– 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)

– Gastro-intestinal (nausea, vomiting, diarrhoea, cramps)

– Cardiovascular (palpitations, tachycardia, hypotension, ST depression)

– Skin (general redness, itching, urticaria)

– Respiration (bronchospasm, distress, cyanosis)

Scombroid toxin

• 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– Mullet– Goatfish– Drummers– Rockcod– Surgeon fish

– Rare and localised– Heat stable– Rapid onset - < 2 h– Symptoms

– Impaired consciousness– Hallucination– Bizarre dreams– Paranoia

– Resolves < 24 h

Rarer toxins

• 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• Ichthyohepatotoxic poisoning

– Eating fish livers (tuna, mackerel, bass, grouper, snapper, sandfish)– Like vitamin A overdose

• 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– Herring– Cod– Pollock– Haddock– Alaskan pollock– Mackerel– Anchovy– Tuna– Salmon– Squid

Trematodes (Flukes)

• Fish are intermediate host• Several genera can infect humans

– 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 – 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

– Paragonimus spp– Abdominal pain– Diarrhoea– Fever– Cough– Urticaria– Hepatospleanomegaly– Lung abnormality– Eosinophilia

– Cough– Expectoration– Haemoptysis– Brain– Other organs

Trematodes

• Symptoms– Other “fish flu”

– 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– Can be none (asymptomatic)– Abdominal discomfort– Diarrhoea– Vomiting– Weight loss– Vitamin B12 deficiency– Pernicious anaemia– Intestinal obstruction

Cestodes

• Common fish hosts– 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

• 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)

Craig Burtonc_burton@seafish.co.uk

01967 43157307876 035771 (Mobile)

Thank you. Enjoy your

fish!