public health risks from fish and fish products craig burton scottish food enforcement officers...

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!