Multistate Outbreak of Salmonella Schwarzengrund Infections Linked to Dry Pet Food (FINAL UPDATE)

Posted September 4, 2007

Outbreak Summary

CDC is collaborating with public health officials in Pennsylvania and other state health departments and the US Food and Drug Administration to investigate a multistate 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.

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 multistate 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.

More information can be found in the MMWR article Multistate Outbreak of Human Salmonella Infections Caused by Contaminated Dry Dog Food—United States, 2006–2007.

Final Case Count Map

Persons infected with the outbreak strain of Salmonella Schwarzengrund, by state of residence, as of September 4, 2007 (n=62)

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).

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.

Advice to Consumers

• Wash hands for at least 20 seconds with warm water and soap right after handling dry pet foods and treats.
• Wash hands before preparing food and before eating.
• Keep infants away from pet feeding areas. Do not allow them to touch or eat dog food.
• Follow the Food and Drug Administration's Safe Handling Tips for Pet Foods and Treats

Questions and Answers Related to the Outbreak of Human Illness due to Salmonella Schwarzengrund Associated with having Dry Pet Food in the Home

What is salmonellosis? What are the symptoms in humans?

Salmonellosis is an infection caused by a bacterium called Salmonella. Most people infected with Salmonella develop fever, diarrhea, and abdominal cramps 12–72 hours after exposure. Illness usually lasts 4–7 days, and most people recover without treatment.

However, the diarrhea can be so severe in some people that they need to be hospitalized. In these patients, the Salmonella infection can spread from the intestines to the bloodstream and then to other body sites. In this situation, the infection can cause death unless the patient is treated promptly with antibiotics. Infants, elderly people, and people with impaired immune systems are more likely than other people to become severely ill.

How do people get infected with Salmonella?

Salmonella live in the intestinal tracts of humans and other animals, including birds. Salmonella usually are transmitted to humans when we eat food contaminated with animal feces or food contaminated by an infected food handler who forgot to wash his or her hands with soap after using the bathroom. Salmonella is also transmitted when contaminated objects or fingers are put into the mouth. The feces of some pets, especially reptiles and pets with diarrhea, can contain Salmonella, and people can be infected if they do not wash their hands after contact with these feces.

Contaminated food often originates from animals–for example, beef, poultry, milk, and eggs. However, any food, including vegetables, can become contaminated. Contaminated food usually looks and smells normal, but thorough cooking kills Salmonella.

How is salmonellosis diagnosed?

Salmonella infection is usually diagnosed by culture of a stool sample. In some instances, it can also be cultured from other body sources such as blood.

Can dogs or cats become infected with Salmonella? What are the symptoms in dogs and cats?

Yes, dogs and cats can get salmonellosis. They also can carry Salmonella without getting sick. Pets that become ill may stop eating and may develop diarrhea, fever, abdominal pain, and vomiting. Some cats do not have diarrhea, but have decreased appetite, fever, and excess salivation. If your pet appears ill, seek veterinary care. Most ill pets recover completely.

Has this outbreak been associated with salmonellosis in dogs or cats?

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

How do I prevent myself or my family from getting salmonellosis from my dog or cat?

After petting, touching, handling, or feeding your pet, and especially after contact with feces, wash your hands for at least 20 seconds with soap and running water. Always wash hands before preparing food and before eating. Always wash hands before preparing baby bottles or baby food and after changing diapers.

If I have a dog or a cat that eats dry pet food, what should I do?

• Wash hands for at least 20 seconds with warm water and soap right after handling dry pet foods and treats.
• Wash hands before preparing food and before eating.
• Keep infants away from pet feeding areas. Do not allow them to touch or eat dog food.
• Follow the Food and Drug Administration’s Safe Handling Tips for Pet Foods and Treats

My dog (or cat) has eaten one the recalled brands of dry pet food. Neither the dog (cat) nor any of my household members are ill. I still have the bag. What should I do?

Do not feed any more of that bag of dry pet food to your pet or to any other animal (including wild animals). Place the container of dog food in a trash container with a closed lid outside the home where humans and animals are not likely to contact it. Wash your hands with soap and running water for at least 20 seconds.

If anyone in your household becomes ill with diarrhea and has bloody stools, fever, or diarrhea lasting more than 3 days, he or she should seek medical care. If your pet develops diarrhea, contact your veterinarian.

My dog or cat ate one of the recalled brands of dry pet food and someone in my household became ill. We still have the bag. What should I do?

Do not feed any more of that bag of dry pet food to your pet or to any other animal (including wild animals). Place the container of dog food in a trash container with a closed lid outside the home where humans and animals are not likely to contact it. Wash your hands with soap and running water for at least 20 seconds.

If the person in your household is still ill, contact your health care provider. Also, contact your local health department because their epidemiologists might want to investigate the illness. If your pet develops diarrhea, contact your veterinarian.

Should I stop feeding dry pet food to my dog or cat?

No. Illnesses have been linked only with brands of dry pet food produced at a single manufacturing facility in Pennsylvania. Commercially produced dry pet food can provide your dog or cat with a balanced diet, which is important for its health. Raw diets, especially raw meat diets, are not recommended because of the risk for salmonellosis and other infections that can affect pets and their owners.