THURSDAY, April 26 (HealthDay News) -- Dogs who accidentally eat a commercial poison to combat gophers and moles can emit a toxic gas that can sicken veterinary staff, a new report indicates.

Experts at the U.S. Centers for Disease Control and Prevention say such canine gas attacks felled workers at four veterinary clinics between 2006 and 2011, and such incidents "might be underreported." All of the workers (and dogs) involved in the four cases recovered, the report added.

The cases involved zinc phosphide, a "readily available rodenticide that, on contact with stomach acid and water, produces phosphine, a highly toxic gas," explained a team led by Rebecca Tsai, an epidemic intelligence service officer at the CDC. People who use the rodenticide are typically aiming to rid properties of burrowing rodents such as gophers or moles, and the products' instructions say that the pellets should be inserted within the animals' tunnels or burrows.

However, sometimes users may have simply spread the pellets on the ground, where dogs could eat them, or "even with correct application, dogs might be exposed while digging in treated areas with their paws or by consuming poisoned prey," the CDC team noted.

Once the zinc phosphide is ingested, the dog quickly becomes sick and owners typically rush them to a vet for care. But the chemical reacts with stomach acid and water to produce the toxic gas phosphine.

In one such case in Washington state last year, owners rushed a "limp," semi-comatose dachshund to a veterinary hospital, where she vomited into paper towels. A 34-year-old veterinary technician nearby who breathed in fumes from the vomit "immediately developed pain and nausea," the report said, but she recovered after 20 minutes.

Other cases have been more serious. In 2008, a 62-pound dog was taken to a vet clinic in Michigan after eating three zinc phosphide pellets. The veterinarian induced vomiting in the dog "in a poorly ventilated room" and quickly experienced symptoms such as "respiratory pain, headache, dizziness, chest pain, sore throat and nausea." Still sick 15 hours later, she went to a local emergency room and was kept under hospital care overnight. Three other workers at the same clinic were also sickened; all eventually recovered.

Similar events were also reported at vet clinics in Michigan in 2006 and in Iowa in 2007.

The CDC says many other cases might go undetected. "Because symptoms might only last a few hours and can resolve without medical treatment, victims might never associate symptoms with poisoning," the researchers said.

For now, the agency recommends that pet owners use products containing zinc phosphide as directed or, better yet, try alternate means of eliminating burrowing rodents such as snap traps. And in cases where pets are suspected of becoming sick by ingesting the pellets, veterinarians should always induce vomiting outdoors to disperse any toxic fumes.

Veterinary staff treating horses with phosphine poisoning have also become sick, according to the American Veterinary Medical Association, which issued guidelines this year for vets regarding phosphine products. Besides rodent bait, these include aluminum phosphide, an insecticide used to fumigate grains and animal feed.

The findings on dogs were published in the April 27 issue of the CDC's journal Morbidity and Mortality Weekly Report.

More information

The ASPCA has more on what to do if you think your pet has been poisoned.