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FOOD SAFETY HAZARDS IN AQUACULTURE SEAFOOD HYGIENE Lecture by Géza Szita. Chemical compsition of the water. Salt concentration of the sea water: 0.35 %.
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FOOD SAFETY HAZARDS IN AQUACULTURE SEAFOOD HYGIENELecture by Géza Szita
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.%
Permanent hardnessis hardness (mineral content) that cannot be removed by boiling.CaSO4, CaCl2MgSO4, MgCl2
Temporary hardnessis hardness that can be removed by boilingCa+HCO3-▬ CaCO3 + H2O + CO2
Toxic materials in the waterAmmonia NH3Hydroxil-amine OH- NH2Nitrite NO2Nitrate NO3Hidrogene-sulphide H2SSulfite ions SO3
1. TERMS, PRODUCTION~ Seafood: alI fish and shellfish (crustaceans, molluscs)finfish: salt- and fresh-water wild fishery I aquaculture> 300 speciesshellfishmolluscs (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
Mollusks The 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.
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).
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.
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 2. FOODBORNE DISEASES FROM SEAFOOD
Paragonimiasisendemic in Asia, South America, West Afticasnails (first) ~ crustaceans (second) ~ humans, mammals parasite infects the lungs (tuberculosis)B. Nematodiasesintemediate hosts marine or ftesh-water fishdefinitive hosts: marine mammals, birds, pigsmode of infection: ingestion of fish infective larvaeCapillariasis- 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 daysAnisaldasis
C Cestodiasesin humans fishborne infections not commonDiphyllobothriasis- D. latum: mainly in cold waters (Eastern Europe, USA) - humans and fish-eating mammals: definitive" hosts- fish: intennediate hosts (salmon)- treatment: praziquantel, niclosamide
~ Bacteriadivided 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 processingEnterobacteriaceaeintroduced 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 riskCampylobacter: little information on the occurrence in aquaculture use of poultry manure for fertilizing ponds ~ potential riskVibrio spp.Salt-tolerant organisms ~ occour naturally in marine environments in both tropical and temperate regionsV. 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 fishAeromonaspart of the normal aquatic floraA. hydrophila ~ fishbome disease'~ risk is low
Clostridium botulinumanaerobic, neurotoxin-producing organismsseven types ~ type E is naturally found in aquatic ~environments ~ often isolated from fishprevention of toxin productionListeria monocytogenesfrequently isolated from aquaculture products in temperate regionsrisk: raw or without heat treatment
VirusesViruses causing disease in fish are not pathogenic to humanstransmission of enteric virus diseases through waste-water reusesystems 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 poisoningproduced by dinoflagellate algaesmall fish feed algae ~ eaten by larger predatory fishannually 10,000-50,000 cases (USA ~ Florida, Hawaii) mostly due to group er, red snapper, Sphyraena barracudaciguatoxin accumulates in the liver, intestines, reproductive organs and muscles of the fishCats are particularly sensitive ~ indicatorPrevention 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 organismstoxin accumulates in the tissues of bivalve molluscs (mussels, clams, oysters, etc.)ingestion of a single clam, if heavily contaminated ~ can kilI a personPrevention: 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 ~ tetrodotoxinMajor 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 cleanedDogs, cats and birds are also susceptible
D. HistamineDue to ingestion of spoiled fish -) mostly Scombroidae (eg, tuna, machereI)develops post-mortem due to improper handling and inadequate refrigerationtissues of scromboid fish contains high level of histidine -). histamine (Vibrio, Klebsiella, etc.)Histamine degraded orally - cadaverine and putrescine (cocontaminants) inhibit histaminases in human intestineLevels > 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. AgrochemicalsFertilizers (urea, ammon ion, salts, trace element mixes) ~ usually no risk to food safety when used according to good agricultural practiceWater treatment compounds (lime, oxidizing agents, flocculants)~ non-hazardousPesticides (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 SEEFOODFish· must be washed and chilled in ice or in cold water immediatley after catching· all of the ship equipment use for fish chilling must be c1eaned and disinfected after each debarkation· fish must be eviscerated as quickly as possible· chilling is also required during transportation to port and during distribution for further pocessing · thorough washing is very important ~ removes up to 95% of putrefactive microorganisms present on the fish skin · during transportation for long distances, the water must be aired; optimum temperature 4-80 oC
Shellfishenvironmental monitoring of water qualityUS 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 harvestingshellfish transferred from marginally polluted areas tounpolluted waters and left min. 14-28 days ~ will purifythemselves (depuration)public education about the risks associated with eating raw shell fish
pH of fish meat = 6.8 - 7.0H2S (lead acetate) at 50 oCfree ammoniatrimethil-aminehistamine - below 100 ppm