Ciguatera poisoning is fish poisoning caused by eating
the flesh of a fish that has eaten a toxin-producing microorganism, the dinoflagellate,
Gambierdiscus toxicus. The poisoning is common in reef fish between
latitudes 35ºN and 35ºS around tropical islands or tropical and semitropical shorelines
in Southern Florida, the Caribbean, the West Indies, and the Pacific and
Indian Oceans. Fish and marine animals affected include barracuda, red snapper,
grouper, sea bass, amberjack, parrot fish, and the moray eel. Incidence is unpredictable
and dependent on environmental changes that affect the level of
dinoflagellates. The toxin is heat-stable, tasteless, and odorless, and is not
destroyed by cooking or gastric acid. Symptoms may begin immediately or within
several hours of ingestion and may include nausea, vomiting, diarrhea, itching and
muscle weakness, aches and spasms. Neurological symptoms may include pain,
ataxia (stumbling gait), paresthesias (tingling), and circumoral parasthesias
(numbness around the mouth). Sensory reversal of hot and cold sensation when
touching or eating objects of extreme temperatures may occur. In severe cases, respiratory failure and cardiovascular collapse may occur. Pruritus (itching) is
characteristically made worse by alcohol ingestion. Gastrointestinal symptoms
usually disappear within 24 to 72 hours. Although complete recovery will occur in
the majority of cases, neurological symptoms may persist for months or years.
Signs and symptoms of ciguatera fish poisoning may be misdiagnosed as decompression
sickness or contact dermatitis from unseen fire coral or jellyfish. Because
of rapid modern travel and refrigeration, ciguatera poisoning may occur far from
endemic areas with international travelers or unsuspecting restaurant patrons.
Never eat the liver, viscera, or roe (eggs) of tropical fish. Unusually
large fish of a species should be suspected. When traveling, consult natives
concerning fish poisoning from local fish, although such information may not
always be reliable. A radioimmunoassay has been developed to test fish flesh for
the presence of the toxin and soon may be generally available.
1. Treatment is largely supportive and symptomatic. If the time since suspected
ingestion of the fish is brief and the victim is fully conscious, induce vomiting
(syrup of Ipecac) and administer purgatives (cathartics, laxatives) to speed the
elimination of undigested fish.
In addition to the symptoms described above, other complications which may
require treatment include hypotension and cardiac dysrhythmias.
3. Antiemetics and antidiarrheal agents may be required if gastrointestinal symptoms
are severe. Atropine may be needed to control bradycardia. IV fluids
may be needed to control hypotension. Calcium gluconate, diazepam, and
methocarbamol can be given for muscle spasm.
4. Amytriptyline has been used successfully to resolve neurological symptoms
such as depression.
5. Cool showers may induce pruritus (itching).
Unlike ciguatera fish poisoning (see paragraph
5C-4.1), where actual toxin is already concentrated in the flesh of the fish, scombroid
fish poisoning occurs from different types of fish that have not been
promptly cooled or prepared for immediate consumption. Typical fish causing
scombroid poisoning include tuna, skipjack, mackerel, bonito, dolphin fish, mahi
mahi (Pacific dolphin), and bluefish. Fish that cause scombroid poisoning are
found in both tropical and temperate waters. A rapid bacterial production of histamine
and saurine (a histamine-like compound) produce the symptoms of a
histamine reaction: nausea, abdominal pain, vomiting, facial flushing, urticaria
(hives), headache, pruritus (itching), bronchospasm, and a burning or itching
sensation in the mouth. Symptoms may begin one hour after ingestion and last 8 to
12 hours. Death is rare.
Immediately clean the fish and preserve by rapid chilling. Do not eat
any fish that has been left in the sun or in the heat longer than two hours.
Oral antihistamine, (e.g., diphenhydramine, cimetidine),
epinephrine (given subcutaneously), and steroids are to be given as needed.
An extremely potent neurotoxin called tetrodotoxin
is found in the viscera, gonads, liver, and skin of a variety of fish, including
the puffer fish, porcupine fish, and ocean sunfish. Puffer fish—also called blow
fish, toad fish, and balloon fish, and called Fugu in Japanese—are found primarily
in the tropics but also in temperate waters of the coastal U.S., Africa, South
America, Asia, and the Mediterranean. Puffer fish is considered a delicacy in
Japan, where it is thinly sliced and eaten as sashimi. Licensed chefs are trained to
select those puffer fish least likely to be poisonous and also to avoid contact with
the visceral organs known to concentrate the poison. The first sign of poisoning is
usually tingling around the mouth, which spreads to the extremities and may lead
to a bodywide numbness. Neurological findings may progress to stumbling gait
(ataxia), generalized weakness, and paralysis. The victim, though paralyzed,
remains conscious until death occurs by respiratory arrest.
Avoid eating puffer fish. Cooking the poisonous flesh will not
destroy the toxin.
1. Provide supportive care with airway management and monitor breathing and
circulation.
2. Monitor anal function.
3. Monitor and treat cardiac dysrhythmias.
Paralytic shellfish poisoning
(PSP) is due to mollusks (bivalves) such as clams, oysters, and mussels ingesting
dinoflagellates that produce a neurotoxin which then affects man. Proliferation of
these dinoflagellates during the warmest months of the year produce a characteristic
red tide. However, some dinoflagellate blooms are colorless, so that
poisonous mollusks may be unknowingly consumed. Local public health authorities
must monitor both seawater and shellfish samples to detect the toxin.
Poisonous shellfish cannot be detected by appearance, smell, or discoloration of
either a silver object or a garlic placed in the cooking water. Also, poisonous shellfish
can be found in either low or high tidal zones. The toxic varieties of
dinoflagellates are common in the following areas: Northwestern U.S. and
Canada, Alaska, part of western South America, Northeastern U.S., the North Sea
European countries, and in the Gulf Coast area of the U.S. One other type of
dinoflagellate, though not toxic if ingested, may lead to eye and respiratory tract
irritation from shoreline exposure to a dinoflagellate bloom that becomes aerosolized
by wave action and wind.
Symptoms of bodywide PSP include circumoral paresthesias
(tingling around the mouth) which spreads to the extremities and may progress to
muscle weakness, ataxia, salivation, intense thirst, and difficulty in swallowing.
Gastrointestinal symptoms are not common. Death, although uncommon, can
result from respiratory arrest. Symptoms begin 30 minutes after ingestion and may
last for many weeks. Gastrointestinal illness occurring several hours after ingestion
is most likely due to a bacterial contamination of the shellfish (see paragraph
5C-4.5). Allergic reactions such as urticaria (hives), pruritus (itching), dryness or
scratching sensation in the throat, swollen tongue and bronchospasm may also be
an individual hypersensitivity to a specific shellfish and not PSP.
Since this dinoflagellate is heat stable, cooking does not prevent
poisoning. The broth or bouillon in which the shellfish is boiled is especially
dangerous since the poison is water-soluble and will be found concentrated in the
broth.
1. No antidote is known. If the victim is fully conscious, induce vomiting with
30cc (two tablespoons) of syrup of Ipecac. Lavaging the stomach with alkaline
fluids (solution of baking soda) may be helpful since the poison is acid-stable.
2. Provide supportive treatment with close observation and advanced life support
if needed until the illness resolves. The poisoning is also related to the quantity
of poisonous shellfish consumed and the concentration of the dinoflagellate
contamination.
Large outbreaks of typhoid fever
and other diarrheal diseases caused by the genus Vibrio have been traced to
consuming contaminated raw oysters and inadequately cooked crabs and shrimp.
Diarrheal stool samples from patients suspected of having bacterial and viral
diseases from shellfish should be placed on a special growth medium (thiosulfatecitrate-
bile salts-sucrose agar) to specifically grow Vibrio species, with isolates
being sent to reference laboratories for confirmation.
To avoid bacterial or viral disease (e.g., Hepatitus A or Norwalk
viral gastroenteritis) associated with oysters, clams, and other shellfish, an individual
should eat only thoroughly cooked shellfish. It has been proven that eating
raw shellfish (mollusks) presents a definite risk of contracting disease.
1. Provide supportive care with attention to maintaining fluid intake by mouth or
IV if necessary.
2. Consult medical personnel for treatment of the various Vibrio species that may
be suspected.
The sea cucumber is frequently eaten in some parts of the world
where it is sold as Trepang or Beche-de-mer. It is boiled and then dried in the sun
or smoked. Contact with the liquid ejected from the visceral cavity of some sea
cucumber species may result in a severe skin reaction (dermatitis) or even blindness.
Intoxication from sea cucumber ingestion is rare.
Local inhabitants can advise about the edibility of sea cucumbers in
that region. However, this information may not be reliable. Avoid contact with
visceral juices.
Because no antidote is known, treatment is only symptomatic.
Skin irritation may be treated like jellyfish stings (paragraph 5C-3.4.4).
Parasitic infestations can be of two types: superficial and
flesh. Superficial parasites burrow in the flesh of the fish and are easily seen and
removed. These may include fish lice, anchor worms, and leeches. Flesh parasites
can be either encysted or free in the muscle, entrails, and gills of the fish. These
parasites may include roundworms, tapeworms, and flukes. If the fish is inadequately
cooked, these parasites can be passed on to humans.
Avoid eating raw fish. Prepare all fish by thorough cooking or hotsmoking.
When cleaning fish, look for mealy or encysted areas in the flesh; cut out
and discard any cyst or suspicious areas. Remove all superficial parasites. Never
eat the entrails or viscera of any fish.
