FOOD SAFETY HAZARDS

IN AQUACULTURE

SEAFOOD HYGIENE

Lecture by Géza Szita

Chemical compsition of the water

Salt concentration of the sea water: 0.35 %

Chloride (Cl): 55.04 wt%

Sodium (Na): 30.61 wt%

Sulphate (SO4): 7.68 wt%

Magnesium (Mg): 3.69 wt%

Calcium (Ca): 1.16 wt.%

Potassium (K): 1.10 wt.%

Freshwater

Total water 'hardness'

(including both Ca2+ and Mg2+ ions)

Permanent hardness

is hardness (mineral content) that cannot be removed by boiling.

CaSO4, CaCl

2

MgSO4, MgCl

2

Temporary hardness

is hardness that can be removed by boiling

Ca+HCO3

- ▬ CaCO3 + H

2O + CO

2

Toxic materials in the water

Ammonia NH3

Hydroxil-amine OH- NH2

Nitrite NO2

Nitrate NO3

Hidrogene-sulphide H2S

Sulfite ions SO3

1. TERMS, PRODUCTION

~ Seafood: alI fish and shellfish (crustaceans, molluscs)finfish: salt- and fresh-water wild fishery I aquaculture> 300 species

shellfishmolluscs (salt-water): mussels, snails, clams, oysters, abalone scallops, cuttlefishcrustaceans (salt/fresh-water): shrimp or prawns, crayfish,lobsters, crabs etc.

Molluscs include chitons, clams, mussels, snails,nudibranchs (sea-slugs), tusk shells, octopus and squid.

Characteristics of molluscs

Unsegmented soft body

Most have internal or external shell

Have a mantle (fold in the body wall that lines the shell)

Muscular foot and/or tentacles

MollusksThe mollusks or molluscs are the large and diverse phylum Mollusca, which includes a variety of familiar creatures well-known for their decorative shells or as seafood. These range from tiny snails and clams to the octopus and squid (which are considered the most intelligent invertebrates). The giant squid is the largest invertebrate, and, except for their larvae and some recently captured juveniles, has never been observed alive, although the Colossal Squid is likely to be even larger.Mollusks are triploblastic protostomes. The principal body cavity is a blood-filled hemocoel, with an actual coelom present but reduced to vestiges around the hearts, gonads, and metanephridia (kidney-like organs). The body is divided into a head, often with eyes or tentacles, a muscular foot and a visceral mass housing the organs. Covering the body is a thick sheet called the mantle, which in most forms secretes a calcareous shell.

Mollusks have a mantle, which is a shell-like outer cover, and a muscular foot that is used for motion. Many mollusks have their mantle produce a calcium carbonate external shell and their gill extracts oxygen from the water and disposes waste. All species of the phylum Mollusca have a complete digestive tract that starts from the mouth to the anus. Many have a radula, mostly composed of chitin, in the mouth, which allows then to scrape food from the surface by sliding back and forth. Mollusks also have a coelom, made from cell masses, where all organs are suspended. Unlike Coelomates, mollusks lack body segmentation.

Development passes through one or two trocophore stages, one of which (the veliger) is unique to the group. These suggest a close relationship between the mollusks and various other protostomes, notably the Annelids.

Mollusks

Bivalves

The bivalves are the second largest class of molluscs. They differ from snails in having two shells, usually mirror images of each other. Some like oysters and mussels live attached to rocks and other hard surfaces while others, like pipis, burrow in sand. Leptonoidean bivalves (in picture) are a group which usually live commensally with other animals. Most have a large foot and are active crawlers.

Limatula strangei. Some bivalves, such as the scallops are able to actively move when endangered by vigorously flapping their shells and squirting out jets of water. Limatula also moves very vigorously when disturbed. The tentacles around the mantle edge are sticky, very mobile and parts can break off them when the animal is disturbed, leaving a potential predator with a sticky writhing worm-like object to deal with as the Limatula escapes (25mm).

Octopus

Hapalochlaena fasciata. There are a number of species of blue-ringed octopus in Australian waters. They are all dangerous to handle, as the poison they use to kill their prey (crabs, snails) is highly venomous to humans. This species is common in New South Wales. Usually a dull mottled colour, it can become yellow with bright blue markings when disturbed.

Squid

Tunafish

SwordfishSwordfish

2. FOODBORNE DISEASES FROM SEAFOOD

raw shellfish or undercooked, smoked, lightly salted fishery products

shellfish: sedentary animals ~ filter their food from coastal

and estuar waters ~ often subject to pollution by sewage

effluents and rain runoff from agricultural lands

~ bacteria, chemical contaminants are concentrated in shellfish

~ quality of shellfish .~ quality of estuarine water in which they have been

harvested

. finfish: prevalance of hazards higher in coastal and inland aquaculture

post-harvest handling, processing

3. BIOLOGICAL HAZARDS

~ Parasites

large number of fish species are potential sources of important parasitic

zoonoses

consumption of raw or inadequatly cooked seefood

fish: intermediate hosts of parasites (humans. the definitive hosts)

A. Trematodiases

important diseases in various parts of the world

ingestion ofviable encysted trematode metacercariae

three important genera: Clonorchis, Opisthorchis, Paragonimus .

Chlonorchiasis

definitive hosts: humans, dogs, cats, rats

larvae ~ fresh-water snails ~ cercariae ~ metacercariae ~

fish musc1e (secondary intermediate hosts) ~ humans ~ bile duct ~

cholangitis, cholangiohepatitis

treatment: praziquantel60 mglkg orally.

Opisthorchiasis

endemic in several Asian countries

first intermediate hosts: snails

Paragonimiasisendemic in Asia, South America, West Afticasnails (first) ~ crustaceans (second) ~ humans, mammals parasite infects the lungs (tuberculosis)

B. Nematodiases

intemediate hosts marine or ftesh-water fishdefinitive hosts: marine mammals, birds, pigsmode of infection: ingestion of fish infective larvae

Capillariasis- gastroenteritis ~ may be fatal- migratory fish-eating birds ~ natural definitive hosts ~spread faeces contaminated with parasite eggs in freshwater fish ponds along migratory routes- treatment: mebendazole 400 mg/day for 20-30 days

Anisaldasis

C Cestodiases

in humans fishborne infections not common

Diphyllobothriasis

- D. latum: mainly in cold waters (Eastern Europe, USA) - humans and fish-

eating mammals: definitive" hosts

- fish: intennediate hosts (salmon)

- treatment: praziquantel, niclosamide

~ Bacteria

divided into two groups:naturally present in the aquatic environment (indigenous bacteria)present as a result of contamination with human or animai faecescontamination during post-harvest handling and processing

Enterobacteriaceaeintroduced into aquaculture ponds by animaI manure or human waste ~ significant numbers in products from waste- fed systems

- Salmonella:may be naturally present in some tropical aquatic environmentaquatic birds spread themfishborne human infeétions rarestrains isolated from humans are different from those found in products from aquaculture

- E. coli : bovine manure as pond fertilizer ~ pathogenicstrains into the pond water0157:H7 ~ cattle ~ waterborne infection

Shigella: occasionally, very little risk

Campylobacter: little information on the occurrence in aquaculture use of poultry manure for fertilizing ponds ~ potential risk

Vibrio spp. Salt-tolerant organisms ~ occour naturally in marine environments in both tropical and temperate regions

V. cholerae also occours in fresh water frequently isolated from sediments, plankton, molluscs, finfish, crustaceanspositive correlation with admixture of contaminated human waste12 species associated with seefoodsome human pathogenic Vibrio spp. may also be fish pathogens

V. Parahaemolyticus ~ particularly associated with consumption of raw marine crustaceans and fish

Aeromonaspart of the normal aquatic flora

A. hydrophila ~ fishbome disease'~ risk is low

Clostridium botulinum

anaerobic, neurotoxin-producing organismsseven types ~ type E is naturally found in aquatic ~environments ~ often isolated from fish

prevention of toxin production

Listeria monocytogenesfrequently isolated from aquaculture products in temperate regionsrisk: raw or without heat treatment

Viruses

Viruses causing disease in fish are not pathogenic to humans

transmission of enteric virus diseases through waste-water reuse

systems is far not so important as bacterial or helminthic diseases

Other biological hazards

large number of toxic compounds produced by aquatic organisms can cause human diseases

produced by aquatic microorganisms: algae, bacteria that serve as food for the larvae of commercially important crustaceans and finfish

possible sources of infection in farmed finfish and crustaceans:ingestion of toxic microorganisms or toxic products in feed

marine zootoxins are among the most highly toxic substances known:

Toxin LD50 (micro g/kg) in mice (IP)

Ciguatoxin 0.5 Saxitoxin 3.0 Tetrodotoxin 8.0 Botulinum A 0.0001 TCDD 2.0

A. Ciguatera poisoning

produced by dinoflagellate algae

small fish feed algae ~ eaten by larger predatory fish

annually 10,000-50,000 cases (USA ~ Florida, Hawaii) mostly due

to group er, red snapper, Sphyraena barracuda

ciguatoxin accumulates in the liver, intestines, reproductive organs

and muscles of the fish

Cats are particularly sensitive ~ indicator

Prevention difficult: ciguatoxin fish do not appear or taste spoiled

B. Saxitoxin poisoning (paralytic shellfish poisoning, PSP)

Saxitoxin: produced by toxic dinoflagellates ~ food base for millions of marine

organisms

toxin accumulates in the tissues of bivalve molluscs (mussels, clams, oysters,

etc.)

ingestion of a single clam, if heavily contaminated ~ can kilI a person

Prevention: coastal shellfish monitoring programs ~ prohibit harvest during

periods when toxin levels are high ("bIoom")

C Tetrodotoxin poisoning (Puffer fish poisoning)

Many species of puffer fish ~ tetrodotoxin

Major cause offatal food poisoning in Japan (fugu)

(Captain Cook nearly died of tetrodotoxin poisoning in New Caledonia in 1774)

Tetrodotoxin: potent vasopressor and neurotoxin concentrates in the liver,

skin ~ flesh becomes contaminated while the fish is cleaned

Dogs, cats and birds are also susceptible

D. Histamine

Due to ingestion of spoiled fish -) mostly Scombroidae (eg, tuna, machereI)

develops post-mortem due to improper handling and inadequate refrigeration

tissues of scromboid fish contains high level of histidine -). histamine (Vibrio,

Klebsiella, etc.)

Histamine degraded orally - cadaverine and putrescine (cocontaminants) inhibit

histaminases in human intestine

Levels > 50mg histamine / 100 g of flesh ~ hazardous

4. CHEMICAL HAZARDS

Through exposure to compounds used in the aquaculture systems

or by pollution of waterways or sources of water

A. Agrochemicals

Fertilizers (urea, ammon ion, salts, trace element mixes) ~ usually no risk to food

safety when used according to good agricultural practice

Water treatment compounds (lime, oxidizing agents, flocculants)~ non-hazardous

Pesticides (algicides, herbicides) no major risk disinfectants ~ widely used ~ no risk to

consumer chemotherapeutica (antimicrobials, parasiticides)

. drugs approved

. drug residues

- Metals(Pb, Cd, Cu, Zn, Fe )

present as a result of geochemical processes result of pollution pH of the water pollutants

Mercury

Chlorinated compounds (DDT, PCBs, dioxins)

5. CONTROL OF FOODBORNE DISEASE FROM SEEFOOD

Fish

· must be washed and chilled in ice or in cold water immediatleyafter catching

· all of the ship equipment use for fish chilling must be c1eanedand disinfected after each debarkation

· fish must be eviscerated as quickly as possible

· chilling is also required during transportation to port and duringdistribution for further pocessing· thorough washing is very important ~ removes up to 95% ofputrefactive microorganisms present on the fish skin· during transportation for long distances, the water must be aired;optimum temperature 4-80 oC

Shellfish

environmental monitoring of water quality

US Public Health Service: shellfish growing areas are surveyedfor safety ~ only those waters not subject to sewage contamination and havingcoliform counts <: 70 organisms/100 ml are approved for harvesting

shellfish transferred from marginally polluted areas tounpolluted waters and left min. 14-28 days ~ will purifythemselves (depuration)

public education about the risks associated with eating rawshell fish

pH of fish meat = 6.8 - 7.0

H2S (lead acetate) at 50 oC

free ammonia

trimethil-amine

histamine - below 100 ppm