A stomach-acting carbamate used as a molluscicide,
insecticide and acaricide.
Animals most affected
Dogs, cattle, (all species).
accidental ingestion of granules or pastes
used as molluscicides, containing 14% of the compound;
accidental ingestion of commercially
prepared rape seeds, treated with a powder containing 50% of
methiocarb prior to sowing);
criminal poisoning, using either baited meat, containing the granules or the
powder, or water deliberately contaminated with the dispersible powder, and which
may achieve a concentration of 50% methiocarb.
Methylcarbamate inhibition of cholinesterase.
Oral doses in mg/kg or concentrations in
LC50 (96 h)
Similar to those resulting from exposure to organophosphorous compounds:
gastrointestinal effects, the first to present: hypersalivation, vomiting, diarrhoea
respiratory effects: bronchial hypersecretion, bronchospasm with cougliing and
neurological effects: muscular fasciculations, tremor, ataxia, occasionally convulsions,
followed by depression, prostration and coma, bradycardia may occur; death
due to asphyxia is frequent, occurring within several hours or up to 48 days
presence of blue granules (or blue liquid in the stomach contents.)
atropine (at the outset of the poisonin within the first 24 hours), 0.2 mg/kg
im or sc, until full atropinization is attained and maintained. Repeat treatment
pralidoxime is ineffective.
emetics, if ingestion within less than 2 hours;
adsorbents (activated vegetable charcoal);
diazepam (e.g. Valium) if indicated, 1-2 mg/kg iv (do not administer barbiturates
or other cardiorespiratory depressants).
Laboratory investigations For causal agents
suspected paste or bait, sample of contaminated water.
Measurement of the level of cholinesterase inhibition
(Immediate freezing of samples necessary as the enzymes degrade very quickly)
brain and plasma (carnivores);
brain, whole blood and cardiac clot (ruminants).
A 4-year old Beauceron bitch ingested a significant amount of methiocarb-treated
rape seed from a sack which had broken open. The dog presented at the clinic with
a staggering gait, hypersalivation and myoclonic spasms. She later collapsed into
decubitus. Immediate treatment with apomorphine made the dog vomit about 500 g of
the treated rape seed and some fragments of a plant. The vet then performed a stomach
washout and gave atropine, 0.5mg iv. In the following hours, the myoclonic spasms
increased in intensity and the animal became extremely excited, with cardiac arrhythmias
and coughing. Twelve hours later the animal was in a depressed state in a light coma.
Atropine was administered for 24 hours, at the end of which time the dog got up,
although still with a marked tremor, but then went into a state of collapse. She
drank copious amounts of water in addition to the fluids (serum glucose, Ringer's
lactate, Heptaminol, protective agents for the liver and diuretics) administered
by the veterinary surgeon.
Thirty-six hours later, the bitch was noticeably calmer and able to get up, although
continuing to shake. However there were no breathing difficulties and the cardiac
rhythm returned to normal. After 2-3 days the animal recovered, although still weak.