In April 2004, the Colorado Department of Public Health and Environment
(CDPHE) was notified about a boy aged 3 years with diagnosed tularemia associated
with a hamster bite. Tularemia has not been associated previously with pet
hamsters. CDPHE conducted an investigation to determine whether other owners
of hamsters were at risk. Clinicians and public health officials should be
aware that pet hamsters are a potential source of tularemia.
During January 2–February 8, the boy was exposed to six hamsters
that his family had purchased from a pet store in the Denver metropolitan
area. Each hamster reportedly died from “wet tail disease” (i.e.,
diarrhea) within 1 week of purchase. One hamster bit the child on the left
ring finger shortly before it died. Seven days later, the child had fever,
malaise, painful left axillary lymphadenopathy, and skin sloughing at the
bite site. After treatment with amoxicillin clavulanate failed, the patient
underwent excisional biopsy of a left axillary lymph node 49 days after symptom
onset for persistent painful lymphadenopathy and intermittent fever. Tissue
culture yielded a suspected Francisella tularensis isolate,
which was confirmed by real-time polymerase chain reaction and timed-release
fluorescence at the CDPHE laboratory. Convalescent serology was positive at
a titer of 4,096, and the isolate was identified by CDC as type B. No other
risk factors for tularemia exposure were identified, including no other animal
contact, no exposure to game meat, and no known mosquito, tick, or fly bites.
The patient improved after treatment with ciprofloxacin.
Workers at the pet store reported an unusual number of deaths among
hamsters but not other animals during January-February; no carcasses were
available for testing. One of two cats kept as store pets had a positive serologic
test for F. tularensis at a titer of 256. Neither
cat had appeared ill to store employees.
Lists of employees, pet suppliers, and customers who purchased hamsters
during December 2003–February 2004 were obtained from the store owner.
Fifteen of 18 customers were located and interviewed. Eight of these had hamsters
that died within 2 weeks of purchase, but all carcasses had been disposed
of and were unavailable for testing. One customer and one employee who had
febrile illness after being bitten by hamsters from the store were negative
for F. tularensis by serologic testing. The same
customer’s hamster was available, and it was also negative for F. tularensis by serology and culture.
Approximately 80% of the 50 hamsters at the pet store came from customers
who had pets with unanticipated litters. The other 20% were purchased from
two small-pet breeders. These breeders were contacted, and neither reported
an unusually high number of deaths of hamsters or other animals. One breeder
also supplied animals to two pet stores in Wyoming. The Wyoming Department
of Health had not been notified of any tularemia cases linked to these stores.
Confirmation of a hamster as the infectious source was limited by the
delay between the patient’s illness onset and diagnosis and subsequent
lack of availability of implicated hamsters for testing. Nonetheless, the
hamster that bit the patient was the most likely cause of infection because
no other exposures or risk factors were identified. The positive serologic
test for F. tularensis in a pet cat at the store
suggested that other animals in the store might have been exposed to F. tularensis. In addition, the proximity of the onset
of the patient’s illness to the timing of the hamster bite, reports
of illness among hamsters, and the deaths of hamsters at the pet store indicated
an infected hamster as the likely source of illness. A possible scenario,
similar to an outbreak of tularemia that involved zoo primates,1 is
that infected wild rodents infested the store and spread the infection to
hamsters by urinating and defecating through metal screens covering hamster
cages. The infected cat might have had a subclinical or unrecognized illness
after catching or eating an infected wild rodent.
The storeowner was advised to set traps for wild rodents and to inform
the state health department of any recurrent animal deaths or reports of ill
customers or staff. No other cases have been identified.
Although tularemia has been associated with hamster hunting in Russia,2 it has not been associated previously with pet hamsters
in the United States. However, clinicians and public health officials should
be aware that pet hamsters might be a potential source of tularemia. Moreover,
because F. tularensis is a potential agent of biologic
terrorism,3 clinicians should have a heightened
awareness of tularemia.
J Pape, K Gershman, MD, Colorado Dept of Public Health and Environment.
J Petersen, PhD, Div of Vector-Borne Infectious Diseases, National Center
for Infectious Diseases; DD Ferguson, MD, JE Staples, MD, EIS officers, CDC.
This report is based, in part, on contributions by S Dolan, Children’s
Hospital, Denver; S Leach, Colorado Dept of Agriculture; staff of the Colorado
Dept of Public Health and Environment laboratory.
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