During the winter, we see many cases of animals ingesting rat poison. Most
of the cases we see are due to ingestion of anticoagulants (warfarin, brodifacoum)
rat poisons. It should be noted that there are actually three general groups
of rat poisons.
- Anticoagulants (warfarin, brodifacoum)
- bromethalin, a neurotoxin
- cholecalciferol-containing rodenticides
The anticoagulant rodenticides are
the most common, and are marketed under many trade names. The mechanism of
action of the anticoagulant rodenticides is to deplete vitamin K, which is
required for normal blood clotting. Diagnosis is usually based on the owner
seeing the pet ingest bait or a rodent that has eaten bait. Rodents that have
eaten anticoagulant rodenticides may contain enough chemical rodenticide to
poison a dog or cat. If treatment is started early, prognosis is usually good.
Bromethalin is a new
nonanticoagulant (Assault, Vengeance) designed to be lethal to rodents after a
single dose. The minimum lethal dose for the dog is approximately 21g bait per
pound body weight, meaning that a 30 lb dog would have to consume 630g bait (or
15 packs of bait) to receive a lethal dose. Ingestion of rodents that have
consumed bromethalin does not cause toxicity in the dog. Thus bromethalin is a
safer rodenticide for use where dogs are present than the anticoagulant
rodenticides. Bromethalin is a neurotoxin directly affecting the brain and
cerebrospinal fluid. Clinical signs associated with ingestion of bromethalin
appear about 10 hours post-ingestion and include severe muscle tremors,
excitability, running fits, seizures and depression.
The last category of rodenticides
is those containing cholecalciferol or vitamin D (Quintox, Rampage, Ortho
Mouse-B-Gone, Ortho Rat-B-Gone). As little as 1g bait per pound body weight can
cause toxicity in the dog. Young dogs appear to be more sensitive. These
rodenticides act by causing vitamin D toxicosis, raising serum calcium levels
to dangerously high levels. Clinical signs arise within 18 to 36 hours after
ingestion, and include depression, anorexia, increased urination and increased
water intake. Muscles are affected by high calcium, and the animal becomes very
weak. Heart conduction becomes slowed, and ventricular fibrillation and cardiac
arrest may result.
With all of these, immediate
treatment is vital.
Please be careful with any of these rodenticides.
Place the bait in a location inaccessible by pets or consider using a
mechanical type of rodent control such as an old-fashioned mousetrap or the
newer nonchemical mouse-motels.