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Multistate Outbreak of Human Salmonella Schwarzengrund Infections Linked to Dry Pet Food (Final Update)

Posted September 4, 2007

This outbreak appears to be over. However, Salmonella is an important cause of human illness in the United States. More information about Salmonella, and steps people can take to reduce their risk of infection, can be found on the CDC Salmonella Web Page.

 

CDC is collaborating with public health officials in Pennsylvania and other state health departments and the US Food and Drug Administration to investigate a multi-state outbreak of Salmonella serotype Schwarzengrund infections in humans. These human illnesses have been linked with dry pet food produced by Mars Petcare US at a single manufacturing facility in Pennsylvania. People who think they might have become ill after contact with dry pet food or with an animal that has eaten dry pet food should consult their health-care providers.

As of September 4, 2007, 62 persons infected with the same strain of Salmonella Schwarzengrund have been reported to CDC from 18 states: Pennsylvania (26 cases), New York (8 cases), Ohio (6 cases), Massachusetts (5 cases), Maine (2 cases), North Dakota (2 cases), Virginia (2 cases), Alabama (1 case), California (1 case), Delaware (1 case), Illinois (1 case), Kentucky (1 case), Maryland (1 case), Michigan (1 case), Minnesota (1 case), New Jersey (1 case), North Carolina (1 case), and Wisconsin (1 case). Of the ill persons for whom an age is available, 39% were one year of age or younger. Of ill persons for whom clinical information is available, 32% developed bloody diarrhea and 10 (25%) were hospitalized. No deaths have been reported.

State and local health departments and CDC continue to receive reports of cases, suggesting the outbreak is ongoing.

Illness related to this outbreak has not been reported in pets. However, the outbreak strain of Salmonella Schwarzengrund was isolated from fecal specimens from two dogs that ate dry pet food in the homes of two of the ill persons.

Investigation of the Outbreak

A multi-state case-control study demonstrated an association between illness and purchase of dry pet foods produced by Mars Petcare US. Households with ill persons were significantly more likely than matched households without ill persons to usually purchase a brand of dry pet food made by Mars PetCare US that may have been produced at a single facility in Pennsylvania.

The Pennsylvania Department of Health (PADOH) conducted environmental testing in this pet food production facility. One of the environmental samples collected by PADOH yielded the outbreak strain of Salmonella Schwarzengrund. In tests by the US Food and Drug Administration of unopened bags of finished dog food produced by this facility, two brands yielded the outbreak strain of Salmonella Schwarzengrund. On August 21, 2007, Mars Petcare US announced a voluntary recall of select bags of these two brands: Red Flannel Large Breed Adult Formula dry dog food and Krasdale Gravy dry dog food. Neither of these brands has been linked to human illness.

Investigations are ongoing to determine why human illness, especially among infants, is associated with dry pet food. Factors under investigation include handling and storage of dry pet food, hand-washing practices, exposure of children to dry pet food, and location in the home where pets are fed.

Transmission and Clinical features

Salmonella bacteria live in the intestines of many food animals, such as cows and chickens, and commonly contaminate foods of animal origin. People get Salmonella infection by ingesting these germs, usually in contaminated food or water, but also by putting objects or fingers contaminated with these germs into the mouth.

Most people infected with Salmonella develop diarrhea, fever, and abdominal cramps 12–72 hours after infection. Infection is usually diagnosed by culture of a stool sample. The illness usually lasts 4– 7 days, and most people recover without treatment. Infants, elderly persons, and people with impaired immune systems are more likely than others to develop severe illness. In severe infection, Salmonella spreads from the intestines to the bloodstream and then to other body sites, and death can occur if the person is not treated promptly with antibiotics.

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