Rat Poisoning in Cats

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Bromethalin Rodenticide Poisoning in Cats

Bromethalin rodenticide toxicity, more commonly referred to as rat poisoning, occurs when an animal is exposed to the chemical bromethalin, a toxic substance that is found in a variety of rat and mice poisons. Ingestion of bromethalin can lead to cerebral edema (the accumulation of excess water in the brain), and an increase in pressure of cerebrospinal fluid - the liquid within the membrane of the skull that the brain essentially floats in. A variety of neurological-based symptoms can result from this, including muscle tremors, seizures, and impaired movement.

While other species may be affected by the accidental ingestion of rat poison, cats are most frequently prone to this condition.

Symptoms and Types

Common symptoms of toxicosis in cats include anorexia (loss of appetite), impaired movement, paralysis of the animal’s hind limbs, slight muscle tremors, generalized seizures, and a depression of the central nervous system. Ingestion of extremely high doses may cause a sudden onset of muscle tremors, and even seizures.

Clinical signs usually develop within two to seven days of bromethalin ingestion, however it is possible that signs will not develop for up to two weeks following ingestion. If poisoning is mild, with minimal bromethalin ingestion, symptoms may resolve within one to two weeks of onset, although some animals may continue to show signs for four to six weeks.


Bromethalin rodenticide toxicity occurs with the ingestion of rodenticides containing the chemical bromethalin. Cats may also be targets of secondary poisoning if they eat rats or mice that have ingested the poison themselves. Toxic doses of bromethalin are estimated to be 0.3 milligrams per kilogram of body weight for cats.


If bromethalin toxicosis is suspected, testing will include a urine analysis, and brain imaging with magnetic resonance imaging (MRI), or a computed tomography (CT) scan, which may reveal excess fluid in the brain.

Other possible diagnoses that may cause symptoms similar to those of bromethalin toxicosis include neurological syndromes produced by traumatic events (such as a car accident), exposure to other infectious and toxic agents, or a tumor growth.

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