Hamster Are Cute, Cuddly, and Potentially Pathogenic

ATLANTA, Jan. 3 -- Those cute little hamsters can carry nasty salmonella pathogens. A rodent is a rodent.

That's the conclusion of an investigation by researchers from the CDC here, after eight pet hamsters were found in 2004 by Minnesota health department workers to have died from the same subtype of Salmonella enterica serotype Typhimurium.

A review of human cases that occurred from December 2003 to September 2004 identified 28 patients with the same rare subtype, according to Stephen Swanson, M.D., of the CDC's Epidemic Intelligence Service Program.

Of the 22 who could be interviewed about exposure to pet rodents, 13 (59%) reported exposure to pet hamsters, mice, or rats, Dr. Swanson and colleagues reported in the Jan. 4 issue of the New England Journal of Medicine.

Two more patients had secondary infections, they said, and there was no confirmed rodent exposure in the remaining seven.

Of the 13 patients with primary rodent exposure, two had pet hamsters, four had pet mice or rats, and seven had bought mice or rats to feed snakes, the investigators found.

The researchers reported two specific human cases that prompted the investigation -- one in South Carolina and one on Minnesota.

In the first case, a four-year-old boy was given a pet hamster from a pet store, which died two days later. A week after the hamster's death, the boy was taken to hospital with fever, watery diarrhea, and abdominal cramping.

A stool culture yielded the same rare subtype of S. enterica serotype Typhimurium, the researchers said.

In the second case, a five-year-old boy had diarrhea for 14 days, abdominal cramps, vomiting, and fever. Four days before the boy fell ill, his family had bought a mouse from a pet store, which immediately became lethargic and developed diarrhea.

Despite the animal's illness, "the boy frequently handled and kissed it," Dr. Swanson and colleagues reported.

Cultures from the boy and the animal yielded the same rare salmonella subtype.

A third case, uncovered during the larger investigation, involved a 23-year-old pregnant woman who had purchased live rats and mice to feed a ball python. She was admitted to hospital with diffuse abdominal pain, diarrhea, and fever, leading to the suspicion of appendicitis.

After an exploratory laparotomy, which showed a normal appendix, a stool sample yielded S. enterica serotype Typhimurium.

After the surgery, the woman went into preterm labor and the infant also proved to be infected with the same subtype of S. enterica serotype Typhimurium, which led to a range of complications and a hospital stay of 56 days.

Tracing backward, the researchers linked the outbreak to 13 pet stores served by seven distributors in 10 states, although no single source of the rodents was found.

The strain found in the outbreak was also cultured from a patient's pet mouse and from seven hamsters from pet stores, while closely related subtypes were found in cages and reusable transport containers at a pet distributor, the researchers said.

Worryingly, all the isolates were resistant to ampicillin, chloramphenicol, streptomycin, sulfisoxazole, and tetracycline, Dr. Swanson and colleagues found.

"Consumers and those who work with animals should be aware that rodents can shed salmonella and should expect rodent feces to be potentially infectious," the researchers concluded.