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 – – – – – – – 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, – 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) – – – – – – 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) Thank you. Enjoy your fish! Craig Burton c_burton@seafish.co.uk 01967 431573 07876 035771 (Mobile)