In recent months an unprecedented number of poisonings associated with rat and mouse baits have been seen in cats. No doubt the plague of rats and mice in country areas has caused the wide spread use of these poisons.
The active ingredient in rodent poisons is Warfarin, or a closely related chemical. Its mode of action is to act on the animal’s liver and prevent the production of prothrombin by interfering with the action of Vitamin K. Prothrombin is the precursor of thrombin, an essential factor in clotting of blood.
The amount of poison required to poison an animal is quite varied. Some of the newly developed substances are far more potent than older preparations. The size of the animal and whether it has a full or empty stomach has a bearing in the amount required to produce clinical poisoning.
There is some evidence that repeated small doses of the poison can suddenly induce a massive fatal hemorrhage in the same way as a single large dose. Diets high in fat, and prolonged antibiotic therapy may make the cat more susceptible to the effects of small amounts of poison.
Owners often ask if their pets will become affected by eating rats or mice that have been poisoned. It seems that as the poison is fairly rapidly absorbed, by the time the rat or mouse is affected by the poison it is no longer toxic to other animals.
In theory, if the cat was to eat a large number of rodents that had amounts of the chemical still unabsorbed in their stomachs, poisoning may be possible. This is very unlikely and by far the majority of cats become poisoned by eating the baits before the target animals.
The symptoms of poisoning vary with the amount of poison absorbed. As the poison prevents blood clotting, hemorrhages may occur in various organs of the body. In exceptional cases the animal may be found dead without any previous signs of illness. In these cases the cause of death is usually due to massive bleeding within the brain or spinal cord.
Sometimes the cat will cough, vomit or pass blood in its bowel motions. In less acute cases the cat will merely become lethargic, will be reluctant to walk or jump and if made to exercise, will begin to breathe heavily.
In a recent case the owners sought veterinary treatment when the kitten began to bleed from the mouth. The source of the hemorrhage was a temporary tooth that had become loose in the gum.
The affected animal is anemic, the gums, interior of the mouth and eyelids have lost the normal pink color and appear white. There may be small hemorrhages visible in the white portion of the eye.
Fortunately all but the very acute forms of Warfarin poisoning are usually reversible. Treatment is aimed at replacing the factors in the blood that have been destroyed by the poison. In some cases blood transfusions are given. Vitamin K in large doses is always administered, and the animal is kept very quiet and away from any likely causes of injury.
Extreme care should be taken when laying baits. Placing the baits on a shelf or under the house is not necessarily safe from an inquisitive kitten. Older cats are usually extremely fastidious but it seems even they may be tempted to try some of the newer preparations.
If you suspect that your pet has eaten a bait contact your veterinary surgeon. Attempts to induce vomiting with emetics may only increase the likelihood of hemorrhage in a poisoned animal.