Transcript Vibrio vulnificus - Lectures For UG-5

Safety Hazards with Marine food
Products
MBT Lec 11
Introduction
Fish and shellfish can become contaminated
 from their natural environment or from subsequent handling or processing.

Fish and shellfish act as intermediate hosts for a number of parasites that
can infect humans

Water polluted with sewage is a particular problem with filter-feeding
molluscan shellfish such as oysters and mussels. which are often eaten raw
or after only light cooking.

These feed by filtering nutrients from large volumes of their surrounding
water, at the same time accumulating microorganisms from their
environment.

Since shell fish are mainly harvested from shallow coastal waters where
sewage contamination is likely to be greatest, they are commonly
contaminated with pathogenic bacteria and viruses of human (and animal)
enteric origin.
Vibrio parahaemolyticus

Fish from warmer coastal waters can often be contaminated with the bacterium
Vibrio parahaemolyticus and can be transferred to other fish both at the market and
in the home.

Vibrio parahaemolyticus cause an intestinal infection that is characterized by lower
gastrointestinal distress such as diarrhea and cramps. In some cases, nausea,
vomiting, fever and headache may also be present.

Occasionally, this disease may manifest itself as a dysentery-like illness with bloody
or mucoid stools, high fever and a high white blood cell count, but normally the
disease has a duration of only two to three days.

Illness with Vibrio parahaemolyticus is most common during the summer months
and is frequently associated with consumption of oyster.

V. parahaemolyticus is readily killed by thorough cooking but can be spread to
cooked fish by inadequate separation of raw and cooked products.
Vibrio vulnificus

Vibrio vulnificus is a bacterium in the same family as those that cause cholera. It
normally lives in warm seawater and is part of a group of vibrios that are called
"halophilic“

Vibrio vulnificus is associated with seafoods, particularly oysters. Which are
often eaten uncooked.

V. vulnificus can cause disease in those who eat contaminated seafood or have
an open wound that is exposed to seawater.

Among healthy people, ingestion of V. vulnificus can cause vomiting, diarrhea,
and abdominal pain.

In immunocompromised persons, particularly those with chronic liver
disease, V. vulnificus can infect the bloodstream, causing a severe and lifethreatening illness characterized by fever and chills, decreased blood pressure
(septic shock), and blistering skin lesions. V. vulnificus bloodstream infections
are fatal about 50% of the time.

V. vulnificus can cause an infection of the skin when open wounds are
exposed to warm seawater; these infections may lead to skin breakdown and
ulceration.

Persons who are immunocompromised are at higher risk for invasion of the
organism into the bloodstream and potentially fatal complications
Vibrio cholerae

Vibrio cholerae is often transmitted by water.

But foods that have been in contact with contaminated water also serve as a
vehicle of infection.

These would naturally include fish from contaminated water or washed with
it after being caught.
Relaying

Numbers of pathogenic bacteria in their tissues can be reduced by
transferring the shellfish to clean coastal waters (relaying) or

by holding them in tanks in which the water is re-circulated and disinfected
with ultraviolet light (a process known as depuration).

While this is an effective and well proven procedure for bacteria, it is far
less so for viruses which seem to persist much longer in shellfish.
Algae Intoxications

Fish can also be the cause of a number of different intoxications where
cooking does not eliminate the problem.

These toxins are often the products of algae.

When these algae are consumed by filter- feeding shellfish or small
herbivorous fish, the toxin accumulates in the flesh which may then be
consumed and accumulated by larger carnivorous fish.
Ciguatera

Ciguatera is an example of this where the toxin (ciguatoxin) is produced by
the dinoflagellate alga Gambierdiscus toxicus and then amplified through
the food chain.

This particular condition occurs only with fish from tropical and subtropical
regions but other types of dinoflagellate intoxication occur in cooler
climates.

Usually this follows an algal bloom where environmental conditions lead to
a sudden proliferation of the toxin-producing algae.
Ciguatera

Ciguatera presents primarily as an acute neurologic disease manifested by a
constellation of gastrointestinal (diarrhea, abdominal cramps and vomiting),
neurologic (paresthesias, pain in the teeth, pain on urination, blurred vision,
temperature reversal) and cardiovascular signs and symptoms within a few
hours of contaminated fish ingestion.

The pathneumonic symptom of Ciguatera intoxication is hot/cold temperature
reversal, although not all patients report this.

Acute fatality, usually due to respiratory failure, circulatory collapse or
arrhythmias, ranges from 0.1% to 12% of reported cases; presently in the
Pacific, the mortality is less than 1%. Lethality is usually seen with ingestion of
the most toxic parts of fish ie. the liver, viscera

The symptoms of Ciguatera poisoning, especially the paresthesias and
weakness, can persist in varying severity for weeks to months after the acute
illnes
Limiting Contamination

In many fish products, salt is an important factor in limiting the growth of
pathogens.

For example, pre-salting is a common practice in fish drying where it helps
accelerate drying while limiting the growth of bacteria during the process.

In smoked fish, a minimum salt content of 3% in the water phase and an
internal temperature of at least 63oC during smoking have been
recommended in order to control Clostridium botulinum.
Clostridium botulinum

Clostridium botulinum is a Gram-positive, rod-shaped bacterium that produces
several toxins. The best known are its neurotoxins, subdivided in types A-G, that
cause the flaccid muscular paralysis seen in botulism.

Types A, B, E, and F cause botulism in humans, while types C and D cause
botulism in animals and birds. Type G was identified in 1970 but has not been
determined as a cause of botulism in humans or animals.

Foodborne botulism results from the ingestion of pre-formed toxin in food.
Botulinum toxin can be found in foods that have not been properly handled or
canned and is often present in canned vegetables, meat, and seafood products

Problems with Clostridium botulinum have been encountered with some
traditional fermented fish products.


These rely on a combination of salt and reduced pH for their safety.
If the product has insufficient salt, or fails to achieve a rapid pH drop to below
4.5, C. botulinum can grow.
Clostridium botulinum

Botulinum toxin is a neurotoxin, thus it affects the nervous system and is
characterized by descending, flaccid paralysis that can cause respiratory failure.

Foodborne botulism produces symptoms beginning in 6 to 36 hours, though
some can even start after two weeks. Symptoms include double and blurred
vision, slurred speech, difficulty swallowing, dry mouth, diarrhea, nausea, and
muscle weakness that descends through the body.

Recovery occurs with prompt administration of antitoxin and respiratory
intensive care. Deaths that occur within the first two weeks of botulism are
often the result of pulmonary or systematic infection and failure to recognize the
disease.

Often the symptoms of foodborne botulism are mistaken for symptoms
associated with stroke, chemical intoxication, myasthenia gravis, and GuillainBarre syndrome
SCOMBROID

Scombroid, one of the most common fish poisonings, occurs worldwide in
both temperate and tropical waters.

The illness occurs after eating improperly refrigerated or preserved fish
containing high levels of histamine, and often resembles a moderate to
severe allergic reaction.
Fish that cause scombroid have naturally high levels of histidine in the flesh
and include tuna, mackerel, mahimahi (dolphin fish), sardine, anchovy,
herring, bluefish, amberjack, and marlin.


Histidine is converted to histamine by bacterial overgrowth in fish that has
been improperly stored (>20°C) after capture. Histamine and other scombro
toxins are resistant to cooking, smoking, canning, or freezing.
SCOMBROID

Symptoms of scombroid poisoning resemble an acute allergic reaction and
usually appear 10–60 minutes after eating contaminated fish.

They include flushing of the face and upper body (resembling sunburn), severe
headache, palpitations, itching, blurred vision, abdominal cramps, and diarrhea.
Untreated, symptoms usually resolve within 12 hours.

Rarely, there may be respiratory compromise, malignant arrhythmias, and
hypotension requiring hospitalization. Diagnosis is usually clinical. A clustering
of cases helps exclude the possibility of fish allergy.

Fish contaminated with histamine may have a peppery, sharp, salty, or bubbly
taste but may also look, smell, and taste normal.

The key to prevention is to make sure that the fish is promptly chilled (below
38°F) after capture. Cooking, smoking, canning, or freezing will not destroy
histamine in contaminated fish.
Parasites in raw, frozen, and smoked fish

Human pathogenic parasites occur in several species of fish that may be coldsmoked, including gadoids, salmonids, sole or flounder, grouper, halibut ,
herring, mackerel, mullet, sablefish, sprat, small tunas, and turbot.

Parasites are also identified as a potential hazard in some invertebrates that may
be cold-smoked or cold-smoked and dried, including octopus, squid, snails, and
crabs/crayfish.

Several species of salmonid parasites, such as Anisakis spp. (a nematode or
roundworm), Diphyllobothrium spp. (a cestode or tapeworm and Nanophyetus
salmincola are of public health concern

ll wild-caught Pacific salmon (Oncorhynchus spp.) are considered to have A.
simplex larvae present. Prevalence reached more than 75% in fresh U.S.
commercial sockeye salmon (O. nerka), chum salmon (O. keta), coho salmon
(O. kisutch), and king salmon (O. tschawyscha) (Myers 1979; Deardoff and
Overstreet 1991)
Parasites

Freezing raw fish prior to smoking remains the most effective way to ensure
that viable parasites are not present in cold-smoked products consumed by
the public. It is essential, therefore, that raw fish potentially containing
viable parasites be frozen and held in that state for a period of time that
assures destruction of all viable parasites in that fish species.

The Fish and Fishery Products Hazards and Controls Guide recommends a
temperature below -4 oF (-20 oC) for 7 d or -31 oF (-35 oC) (internal) for 15
h to kill the parasites of concern