Rat and mouse poisoning occurs when the cat either directly ingests rat poison or indirectly ingests it after catching and consuming a rodent who has itself ingested poison. Many rat and mouse poisons contain anticoagulants which inhibit the coagulation of blood. Internal bleeding occurs due to the poison which blocks the body’s production of clotting factors.
What causes internal bleeding?
Blood vessels are tubes which transport blood around the body, endothelial cells line the vessel walls which help blood travel easily through them. If the blood vessel breaks, three mechanisms occur to slow and stop the loss of blood.
Vasoconstriction: Small muscles in the blood vessel wall constrict which reduces the amount of blood flow, reducing blood loss.
Primary hemostasis: Platelets are circulating cells are activated, which clump together and bind to the site on the damaged blood vessel, to form a plug.
Secondary hemostasis (also known as coagulation cascade): Proteins known as coagulation factors are manufactured by the liver. A complex set of chemical reactions occurs involving coagulation factors, converting factor 1 (fibrinogen) into fibrin, long thin strands which entangle the platelets.
Rat poison depletes the body of Vitamin K which is necessary for the formation of certain blood clotting factors.
Two types of rat poison contain anticoagulants.
First generation rat poisons have a shorter half-life, which is the time it takes for the poison to decrease by half. The active ingredient in first generation rat poisons is Warfarin. Poisoning occurs after several repeated exposures.
Second generation rat poisons are considerably more potent and. The active ingredients in second-generation rat poisons are usually bromadiolone or brodifacoum. A single dose is enough to kill a cat.
The poisons have no effect on clotting factors already in circulation, so there will be a lag of 1-3 days before these clotting factors run out (and are not replaced) and symptoms occur.