Pet hamsters are a potential source of serious infection, U.S. health officials warned on Thursday.

Researchers from the U.S. Centers for Disease Control and Prevention (CDC) describe the case of a 3-year-old boy from Colorado who came down with tularemia after being bitten by a pet hamster.

Tularemia is caused by the bug Francisella tularensis, which is one of the most infectious germs known and for that reason is considered a potential biologic terrorism agent.

As outlined in the CDC’s Morbidity and Mortality Weekly Report, the boy’s family purchased six hamsters from a pet store in the Denver metropolitan area. Within a week, all of the hamsters died of diarrhea, but not before one of them bit the child on the finger.

Seven days after the bite, the child developed fever, malaise, painful swelling of lymph nodes in his left armpit, “and skin sloughing at the bite site.”

Treatment with the antibiotic amoxicillin-clavulanate failed to clear up the condition, and lymph node biopsy was performed. This revealed the cause to be Francisella tularensis.

Employees at the pet store reported that an unusual number of hamsters had died around the time the boy’s family purchased the hamsters.

Officials with the CDC and the Colorado Department of Public Health and Environment investigated, and they think that infected rodents infested the pet store and spread the bacterium to hamsters by urinating and defecating through metal screens covering their cages.

One of two pet cats in the store was also found to be infected with the tularensis bug, perhaps from catching or eating an infected rodent.

“Although tularemia has been associated with hamster hunting in Russia, it has not been associated previously with pet hamsters in the United States,” the CDC’s Dr. Dayna Ferguson and colleagues note in the article.

Symptoms of tularemia include sudden fever, chills, headache, diarrhea, muscle aches, joint pain, dry cough and progressive weakness.

SOURCE: Morbidity and Mortality Weekly Report, January 7, 2005.