In 2004 and early 2005, nine people, in the US and Canada, contracted Salmonella Thompson after handling pet food. All the case isolates were analyzed using pulse-field gel electrophoresis; all isolates were genetic matches to one another. The pet food was traced to one British Columbia and one Washington processing plant. Manufacturers had used raw beef and salmon that had been frozen, thawed, formed into shapes and then dehydrated. Although the pet treats were dehydrated, 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. Salmonella was found in customer samples of the products. From plant samples, the salmon treats yielded a Salmonella Thompson strain that was a genetic match to the outbreak strain.