Zinc Phosphide Poisoning in Cats

The poison works by reacting with your cat’s stomach acid after ingestion and producing deadly phosphine gas. This gas affects red blood vessels in the kidneys, liver and lungs leading to cardiovascular collapse (heart failure) and death. It is most effective in animals that have no vomit reflex, such as rats and rabbits, but can be lethal in cats if not treated immediately.

If you notice your cat is being lethargic, retching, or has begun to vomit, zinc phosphide poisoning may be the culprit. Zinc phosphide is a main ingredient in many rodenticides and other pest poisons. Your cat is at a higher risk of zinc phosphide poisoning if allowed outdoors. Zinc phosphide is extremely poisonous and ingestion can be life threatening.

The symptoms of zinc phosphide poisoning are very similar to the effects of other poisons in cats. Even if your cat only exhibits a few of these symptoms, zinc phosphide poisoning may still be the cause. Immediate action is required. Symptoms are as follows:

• Lack of appetite
• Garlic/rotten fish smelling breath
• Rapid and or difficulty breathing
• Lethargy
• Weakness
• Abdominal bloat or pain
• Diarrhea and gas
• Vomiting
• Drooling
• Seizures or convulsions
• Coma
• Death

Please note, if your cat has vomited indoors it is crucial that you immediately ventilate the area, as phosphine gas is also harmful to humans. If your cat has vomited outdoors, wash away all vomit while standing upwind. Remove all solids left over to prevent pets from eating the poison a second time. If you or anyone else in the home starts showing any of the above symptoms, call 911 at once.

For zinc phosphide to poison your cat, it must be ingested. If your cat ingests a rodent who has eaten rat poison, the poison can transfer to the cat. The more food in the cat’s stomach, the more toxic gas that will be produced, leading to worsening symptoms. The main causes of zinc phosphide poisoning are:

• Ingestion of any rodenticide
• Ingestion of small mammals who have eaten rodenticide
• Ingestion of any other pest poison

Call your veterinarian or pet poison control as soon as possible if poisoning is suspected. The longer the gas is left in the cat’s stomach, the worse the cat’s condition will get. If you witnessed the cat eating pest poison, or eating a rodent, tell your veterinarian at once. If other poisons can be ruled out, your cat will be able to receive treatment sooner. You may be advised to induce vomiting at home, but in most cases, you will be instructed to rush the cat to a vet clinic or animal hospital. Once there, the veterinarian will:

• Ask if there are rodenticides in your home
• Ask if the cat is allowed outdoors
• Inquire if you've noticed the cat eating mice or other rodents recently
• Check for garlic/rotten fish smelling breath
• Assess other symptoms to ensure zinc phosphide is the most likely cause of poisoning

It is important to be sure if the cat has been poisoned by zinc phosphide before inducing vomit, as the effects of some other poisons are exacerbated by vomiting. Ingestion of calcium phosphide, aluminum phosphide and magnesium phosphide will all produce phosphine gas and are to be treated the same way.

Treatment options for zinc phosphide poisoning typically include:

• Vomiting induced in a ventilated area
• Gastric lavage (stomach washing) with a mixture that is 5% sodium bicarbonate to raise the pH in the stomach and delay the formation of gas
• Activated charcoal administered to absorb toxins
• Evaluation of all organs to assess if the cat is responding favourably
• Upon positive response, medication will be given to reduce the production of stomach acid to stop the chemical reaction causing the phosphine to be produced.

If the cat does not respond favourably after all treatments have been attempted, the prognosis is poor; the cat may die of heart failure.

The minimum expected hospital stay for a cat who has been poisoned by zinc phosphide is 48 hours. The cat will be closely monitored throughout this stay to ensure organs are recovering and red blood cells are increasing.

You can expect your cat to be depressed or lethargic for several days after being discharged. Ensure all poison has been removed from your home. Take measures to keep your cat indoors to avoid consumption of poison affected rodents.