Page 980 - Problem-Based Feline Medicine

972 PART 11 CAT WITH AN ABNORMAL GAIT

associated with coral reefs (mostly coral trout, Cardiovascular effects are biphasic. Low doses of toxin
Spanish mackerel, barracuda). tend to induce hypotension, hyperventilation, brady-
cardia and atrioventricular block. As toxin absorption
A marine benthic dinoflagellate, Gambierdiscus toxi-
increases, the higher doses cause hypertension, tachy-
cus, is believed to produce a precursor to ciguatoxin,
cardia, respiratory depression and perhaps cardiac
gambiertoxin, which undergoes biotransformation
arrest.
within the stomach of herbivorous fish. The resultant
ciguatoxin is absorbed from the stomach and Recovery is slow and signs may persist for 1–2 weeks.
sequestered in the muscles and viscera (potency
increases tenfold in the process).
Diagnosis
Ciguatoxin is heat stable and not affected by cooking.
History of access to coral reef fish.
Ciguatoxin is lipid soluble and may cross the
Presence of gastrointestinal signs along with neuro-
blood–brain barrier, which accounts for the CNS effects.
logical signs is supportive.
An associated toxin, maitotoxin, is water soluble and is
A rapid calorimetric immunoassay (the “stick test”)
believed to account for the gastrointestinal effects.
conducted on the fish flesh is inexpensive and quick
Ciguatoxin interferes with the sodium channels and of use in ciguatera endemic regions.
located on the cell membrane of neurons. In the muscle
sarcolemma it increases sodium permeability of the
Differential diagnosis
cell membrane. Increased sodium permeability
enhances activation. Rule out other causes of neurological signs, especially
tick paralysis and brown snake envenomation. Cats
Cardiac effects are the most life threatening and
with ciguatoxicity typically have gastrointestinal signs,
involve arrhythmias and negative inotropy. Focal
a history of access to reef fish, a lack of voice involve-
myocardial necrosis is evident histologically.
ment (typical in tick paralysis), and no coagulation
Centrally mediated interference with phrenic nerve defects (typical in brown snake).
conduction may lead to respiratory failure and death.
Rule out toadfish (tetrodotoxin) poisoning largely via
history of access as well as pupillary dilation and
Clinical signs voice changes are more typical of tetrodotoxin.

Cats fed reef fish are at risk of poisoning, as are humans,
even though incidences are low. Cats fed viscera and Treatment
liver of these fish may consume a lethal meal because
No specific treatment is available. Symptomatic and
ciguatoxin levels are 50 times greater than in fish flesh.
supportive measures including maintenance of body
Signs begin within 3–6 hours of ingestion of a toxic fluids and artificial respiration may be required.
meal and may last up to 14 days.
Gastric lavage and/or induction of emesis in the early
Neurological signs include hindlimb paralysis stages of intoxication may decrease the severity of signs.
extending to forelimbs in severe cases, and ataxia.
Atropine (up to 1 mg/kg) helps control the gastroin-
Gastrointestinal signs include hypersalivation and
testinal signs as well as reduces the bradycardia
vomiting.
and hypotensive components of the cardiovascular
Less severe cases may have some mild gastrointestinal effects.
signs and mild paresis.
Lignocaine by constant rate infusion (400 μg/kg/min)
Respiratory difficulty and arrhythmias may also has been shown to alleviate the cardiovascular effects
occur. Death from respiratory failure can occur several of ciguatoxin in the cat, probably by blocking the
days later. sodium channels.