A Rodent Bait With Zinc Phosphide Can Threaten Your Life as Well as Your Pet’s

Rodent Bait

Story at-a-glance

  • Recently, a dog in Colorado who ingested what is believed to be rat bait containing the chemical zinc phosphide, sent an emergency room DVM and three staff members to the hospital.
  • The dog vomited inside the Vail Valley Animal Hospital, and toxic gas emanating from the vomit caused breathing problems for the veterinarian and technicians.
  • The dog is suspected of ingesting a bait containing zinc phosphide, which when mixed with liquid (in this case, stomach contents), creates toxic phosphine gas.
  • Sadly, the dog didn’t survive. Fortunately, this type of incident is not commonly seen at veterinary clinics.
  • If you suspect your pet has ingested a product containing zinc phosphide, in addition to calling your veterinarian or an emergency animal hospital, there are guidelines you should follow in handling your pet.

By Dr. Becker

In December of last year, a dog suspected of ingesting a toxic chemical sent an E.R. veterinarian and three technicians at a Colorado animal hospital to a hospital for human patients.

The dog is thought to have eaten zinc phosphide, which is used as a rodenticide. It kills rats, mice and other rodents when acid in their digestive systems reacts with the phosphide, creating a toxic gas.

Baits containing zinc phosphide have a strong odor similar to garlic that attracts rodents but repulses other animals. The baits usually contain a mixture of zinc phosphide and an emetic to cause vomiting if eaten by humans or pets. (Most rodents don’t have a vomit reflex, which is why the emetic doesn’t cause them to throw up.)

Stomach Contents + Zinc Phosphide = Toxic Gas

When the dog at Vail Valley Animal Hospital in Edwards, Colorado vomited up the rodenticide, it created toxic gas that caused breathing problems for staff that were treating him. The zinc phosphide the dog ingested mixed with the contents of his stomach, creating the toxic gas.

Fire department personnel worked with animal hospital staff to get the dog outside and away from the contaminated area, and equipment was also moved outside so a vet could continue work on the dog. Sadly, the dog did not survive.

Symptoms of Exposure to Phosphine Gas

The gas created by zinc phosphide and liquid is phosphine gas. It’s colorless, flammable and explosive at room temperature. Breathing in the gas in high concentrations causes damage to the heart and lungs, nervous system, liver, and kidneys, and can be fatal.

Human symptoms of nonfatal exposure to the gas include pain in the diaphragm, nausea and vomiting, excitement, and breath that smells of phosphorus. Higher levels of exposure can result in weakness, bronchitis, pulmonary edema, shortness of breath, convulsions and death. The E.R. vet and technicians at Vail Valley Animal Hospital who became ill experienced respiratory distress, a burning sensation in the throat, and trouble breathing.

The CDC views phosphine gas exposure at vet clinics as an occupational hazard, but fortunately, it’s not a common occurrence. Only four reports of poisonings occurred from 2006 to 2011, according to the CDC’s National Institute for Occupational Safety and Health.

If You Think Your Pet Has Ingested Zinc Phosphide …

Rodenticides containing zinc phosphide are used to kill rats, mice, moles and gophers. The product will either be in powder form with a dark gray color, or a grain-based pellet. It will have an odor of fish, garlic or acetylene. Brand names of baits containing zinc phosphide include Arrex, Commando, Dexol, Kilrat, GophaRid, Phosvin, Ridall, Ratol and Sweeney’s Poison Peanuts.

After two phosphine gas poisoning incidents a few years ago, the Michigan Department of Community Health developed guidelines to help humans avoid exposure while providing treatment to exposed pets. These guidelines were actually written for veterinary teams, but I feel they could be helpful for pet parents as well.

  • Take the dog outside to vomit. This will provide plenty of ventilation for both the animal and whoever is treating him, and will also allow the area to be hosed down afterwards.
  • Remain upwind of the dog, and once the dog has vomited, take him upwind of the vomit as well.
  • Don’t place your head close to the ground while trying to help your pet. Phosphine gas is heavier than air and will be highly concentrated closer to the ground.
  • Flush the area with plenty of water and make sure any solid matter is diluted so it won’t attract other animals. There is adequate airflow outdoors to prevent the gas from reaching toxic levels.
  • If your dog vomits indoors, remove everyone from the area and open windows and doors for ventilation. Your local fire department can measure the level of phosphine in the air and determine when it’s safe to go back inside. If anyone (human or animal) around the sick pet experiences symptoms of exposure to phosphine gas, he or she should seek medical attention.

If you have pets, I don’t recommend rodent bait traps of any kind in or around your home. If you have a mouse or rat problem, I recommend a live trap called the Havahart®. This is a humane trap that catches mice, rats or other rodents so that you can remove them from your home without using toxins or poisoning your environment.

When your pets are outside, make sure they are supervised. Don’t allow them to consume potentially poisoned rodents on your property or while visiting a neighbor’s home.


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