Tracking down the source of an outbreak of salmonella infection that has spanned the country is a detective story that took an interesting turn last month when a key clue was found hiding in a dog food plant in Fayette County.
As of last week there have been 66 cases across 18 states since early last year. Pennsylvania has had 25 cases including one reported last summer in Allegheny County. No deaths or cases involving pets have been reported, but the outbreak is considered to be continuing.
After the salmonella strain, Salmonella Schwarzengrund, was detected in two dogs in the homes of two of the ill persons, and in unopened bags of dog food produced by Mars Petcare in the Everson plant in Fayette County, the company voluntarily recalled two brands Aug. 21. The plant was closed last week for inspection and cleaning. Officials from the company could not be reached to update the plant's status.
Further investigation of the outbreak is a collaboration between the U.S. Centers for Disease Control and Prevention, health officials in the affected states and the U.S. Food and Drug Administration.
The break in the case -- tracing human sickness to dog food -- was made by Pennsylvania investigators, led by Dr. Stephen Ostroff, director of the bureau of epidemiology at the state Health Department.
He said the state investigation began in mid-June.
"Cases had been occurring every now and then -- once a month or so, for quite a while. ... then, in spring of this year, we started noticing cases occurring of a salmonella strain we don't see very often ... now popping up every week or two," Dr. Ostroff said.
He said many of the sick had told investigators that they had dogs in the home. "Now that's a pretty common finding. But this was fairly consistent [and] prompted investigators to go out to their homes to get samples from the dogs," Dr. Ostroff said, adding that the salmonella strain was found in feces of two dogs.
How did the plant in Everson get targeted?
Dr. Ostroff said the FDA responded in early July to reports from investigators, who canvassed homes that had people with illness and those without illness. "One thing we found, there was a very strong association between illness and having a product made at this plant in Western Pennsylvania," he said. However, he pointed out, "None of the cases in Pennsylvania mentioned either of these brands [now under recall]."
The FDA then collected samples from the plant, but found nothing.
In turn, Dr. Ostroff said, the state health department went back to the plant. "We took swabs from the machinery, the floor all over the plant. We had them tested ... one was positive for this particular organism."
The FDA went back to the plant in late July. In total, according to an FDA report, the agency conducted tests on 10 samples, representing seven product brands from the company. Each sample (with same size and brand) included 15 subsamples, for a total of 150 subsamples. Two samples tested positive for the salmonella strain: one from the Krasdale Gravy dry food and one from Red Flannel Large Breed Adult Formula dry food.
Mars Petcare was notified, and issued its recall. The FDA has reported that none of the cases of illness has been directly linked to the recalled products.
The CDC reported that investigations are continuing to determine why humans got sick -- especially the 39 percent of victims who were under 1 year old -- from dry dog food.
Speculating on how the salmonella was spread, Dr. Ostroff said, "It could be the way you handle the dog food bowl, the way the dog eats the food, maybe getting it on the floor ... that's what we think is probably happening. This type of scenario is similar to what we've seen in the past, with turtles in the home, reptiles in the homes that have spread salmonella among young children."
People infected with salmonella bacteria get diarrhea, fever and abdominal cramps 12 to 72 hours after infection. It usually lasts four to seven days and most people recover without treatment. Salmonella in pet food and treats can cause serious infections in dogs and cats, but also in people -- particularly children, older people and people with compromised immune systems.
It has yet to be determined how the dog food became contaminated. "The FDA and the company will have to try to find that out," Dr. Ostroff said.
Safe handling of food and pets is recommended. Although the state Health Department says the overall risk of salmonella from dry pet food is low, it reminds consumers that pet food is not sterile and is a potential source of harmful bacteria.
Jill Daly can be reached at firstname.lastname@example.org or 412-263-1596.