THURSDAY, June 29 (HealthDay News) -- Pets always welcome treats, but their owners may be putting themselves at risk of developing salmonella infection by handling beef or seafood snacks contaminated with the bacteria.

So warned the authors of a report issued Thursday by the U.S. Centers for Disease Control and Prevention (CDC).

The CDC study outlined nine cases of pet owners becoming sick with a specific type of infection, called Salmonella Thompson, in 2004 and 2005, after handling pet treats from two different manufacturers, one in the state of Washington and the other in British Columbia, Canada.

"This is the third outbreak in North America, the first in the United States, but we know these animal-derived pet treats are frequently contaminated with salmonella," said report co-author Fred Angulo, an epidemiologist at the CDC's Division of Foodborne, Bacterial and Mycotic Diseases, part of the National Center for Zoonotic, Vector-Borne, and Enteric Diseases.

"There probably have been more cases," Angulo said. "There's certainly salmonella being brought into people's homes on pet treats. People are probably getting sick but not attributing it to contact with pet treats," he added.

All the patients included in the CDC report developed diarrhea, and one also experienced vomiting. That patient, an 81-year-old woman, required hospitalization, according to the report.

In each case, the illness was traced back to pet treats contaminated with Salmonella, concluded experts, who detailed their findings in the CDC journal Morbidity and Mortality Weekly Report.

The manufacturers had received frozen, raw beef parts from slaughterhouses in Canada and the United States. In addition, the Washington manufacturer received frozen, raw salmon.

"Although the pet treats were dehydrated at the British Columbia and Washington plants, the dehydration temperatures were not high enough to kill bacteria that might have been present. No processing step, such as irradiation, that would destroy Salmonella and other bacteria was used during the processing," according to the report.

"Ultimately, the way to prevent this is at the point of production," Angulo said. "There is no need for salmonella to be present in pet treats," he said. "Pet treats can be properly produced so that salmonella would not be present. Pet treats could easily be irradiated and easily be heated to a temperature that would kill salmonella and then be quickly and safely packaged so that salmonella would not be reintroduced," he added.

To prevent getting an infection from contaminated pet treats, the CDC recommends that people wash their hands thoroughly with soap and water after handling animal-derived pet treats. They also advise that children under the age of five, older adults and people with immune system problems stay away from animal-derived pet treats because of the possibility of severe infection or serious complications from salmonellosis.

The agency is also calling on pet store owners, health-care providers, veterinarians, and pet treat manufacturers to provide information to pet owners about the potential health risks of animal-derived pet treats and salmonellosis prevention.

In addition, they are urging pet treat manufacturers to use heat-treatment or irradiation that would destroy Salmonella and other bacteria during processing.

An industry spokesman believed the problem was caused by the failure of manufacturers to follow established guidelines for the preparation of pet treats, developed by the U.S. Food and Drug Administration (FDA).

"The American Pet Products Manufacturers Association has worked with the FDA to develop voluntary guidelines for the preparation, manufacture and handling of pet treats," said the association's general council, Ed Rod.

"A lot of animal products can be contaminated if they aren't processed properly," Rod said. "It sounds like there was a failure in the manufacturing process," he added.

Rod doesn't think new regulations are needed, however. "These manufacturers may not have complied with the applicable regulations already in place," he said.

But Angulo disagreed, saying industry and the FDA could be doing more.

"There is an onus on the industry to prevent this from occurring," Angulo said. "Many of the larger pet food companies are aware of this hazard and are attempting to address it already, but there are a lot of small producers whose profit margins are so low that voluntary measures won't be sufficient," he said.

"The only way to way to really prevent this might be a regulation that would require producers to prevent this from occurring," Angulo said. "The way to prevent this would be to have the FDA regulate pet treats, which they have the authority to do," he said.

More information

For more on dog food safety, head to the U.S. Food and Drug Administration.