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On August 12, this report was posted as an MMWR
Dispatch on the MMWR website (http://www.cdc.gov/mmwr).
In May 2005, CDC received reports of illness in four solid-organ transplant
recipients who were later determined to have been infected with lymphocytic
choriomeningitis virus (LCMV) from a common organ donor.1 Three
of the four organ recipients died, 23-27 days after transplantation. This
report updates information about the ongoing investigation and provides interim
measures for reducing the risk for LCMV infection from pet rodents associated
with this outbreak.
Epidemiologic investigation traced the source of the virus to a pet
hamster recently purchased by the organ donor from a pet store in Rhode Island.
LCMV testing of other rodents at the pet store identified three other LCMV-infected
rodents (two hamsters and a guinea pig). All four pet rodents had been supplied
by a single distributor, MidSouth Distributors of Ohio. Preliminary test results
determined that four (3.4%) of 115 hamsters sampled from the Ohio distributor
had active LCMV infection. On the basis of sequence analysis, the LCMV from
the transplant recipients, the donor’s pet rodent, and from rodents
obtained from the Rhode Island pet store and the Ohio distributor were determined
to have the same lineage (i.e., likely to share a common source). Under the
authority of the Ohio Department of Agriculture, the MidSouth facility was
quarantined. The MidSouth owner voluntarily depopulated the facility; the
premises also will be disinfected.
LCMV test results for the sampled rodents and records reviewed at the
Rhode Island pet store and at MidSouth Distributors indicate that LCMV-infected
pet rodents might have been transported from the Ohio facility to pet stores
in the northeastern and midwestern United States as early as February 2005.
Ohio authorities and CDC are working to determine which stores and states
have received potentially affected shipments from the Ohio facility. CDC also
is conducting an ongoing traceback investigation of the breeding facilities
that supplied MidSouth Distributors.
LCMV infection in humans with normal immune systems usually causes either
asymptomatic or mild, self-limited illness. Aseptic meningitis also can occur
in some patients, but the infection is rarely fatal.2 However,
LCMV infection during the first or second trimester of pregnancy can cause
severe illness or developmental defects in the fetus, including hydrocephalus,
psychomotor retardation, blindness, and fetal death.3 The
frequency with which developmental defects occur after in utero LCMV infection
is not known. In addition, LCMV can be a serious infection in persons with
impaired immune systems.
Pet hamsters and guinea pigs are not known to be natural reservoirs
for LCMV. However, pet rodents can become infected if they have contact with
wild house mice (Mus musculus) (e.g, in a breeding
facility, pet store, or home). Although infection of other animals with LCMV
might be possible, documented infections in humans have occurred only after
exposure to infected mice, guinea pigs, and hamsters.2,4 Most
human cases are associated with wild house mice, which are considered the
Serologic testing of pet rodent species for antibodies against LCMV
has not been reliable; the tests have not detected antibodies in animals with
active infections demonstrated by other tests (i.e., immunohistochemistry
staining of tissues and virus isolation). The unreliability of serologic testing
is of concern because certain species of pet rodents infected with LCMV can
shed virus for up to 8 months without signs of illness and thus can be a source
of infection for humans.4,6
A large outbreak of LCMV infection associated with pet hamsters sold
by a single distributor was reported in 1974, when 181 symptomatic human cases
were identified in 12 states; no deaths occurred.7 The
outbreak was controlled by voluntary cessation of the sale of pet hamsters
and subsequent destruction of the infected breeding stock. Stores were advised
that all caging material be decontaminated or destroyed before receiving new
animals. In addition, the public was informed of the risk for infection from
hamsters purchased during the outbreak at stores supplied by the affected
Two national retail chains have temporarily stopped the sale of potentially
affected rodents (e.g., hamsters, guinea pigs, gerbils, rats, chinchillas,
and mice) originating from MidSouth Distributors since February 2005. Pet
stores that have received rodents from MidSouth Distributors since February
should contact the appropriate authority in their states (i.e., state health
department or state department of agriculture) for additional information
Although LCMV is known to infect hamsters and guinea pigs, data are
insufficient to determine the potential for infection of other rodent species
(e.g., chinchillas, dwarf hamsters, or gerbils). However, husbandry practices
in breeding facilities, distribution centers, and pet stores make cross-contamination
with LCMV of other species a possibility. CDC is working with retailers in
the pet industry to consider appropriate testing of these other rodent species.
Practices that can lead to cross-contamination of rodents include (1)
housing healthy rodents in the same room or bin or in cages near potentially
infected rodents (i.e., rodents from the MidSouth Distributors facility in
Ohio); (2) handling or caring for rodents without washing hands or changing
gloves after handling other rodents and between other animal-care activities,
such as cleaning cages; (3) placing rodents in cages that previously housed
other rodents without first decontaminating the cages with bleach or other
appropriate disinfectants; and (4) reusing materials (e.g., water bottles,
food dishes, bedding, or toys) that might be contaminated by potentially infected
Pet rodents that did not originate from MidSouth Distributors of Ohio
and were not exposed to potential cross-contamination can be sold or distributed
as normal. In addition, nonrodent species (e.g., ferrets and rabbits) can
be sold or distributed as normal.
Pet stores are advised to work with state authorities to minimize the
risk for transmission of LCMV from affected rodents to humans. Options considered
by state authorities include (1) stopping sale or distribution of all rodents
originating from MidSouth Distributors of Ohio since February, (2) stopping
sale or distribution of hamsters and guinea pigs originating from MidSouth
Distributors of Ohio since February, or (3) allowing distribution (i.e., sale
or adoption), provided that appropriate educational material (e.g., state-approved
informed consent or fact sheet) is provided to purchasers of pet rodents originating
from MidSouth Distributors since February. Educational material should disclose
the specific LCMV risk in this population of pet rodents and potential outcomes
in humans, including birth defects and fetal deaths. If sale of rodents is
allowed to continue, populations at high risk (i.e., pregnant women, women
who think they might become pregnant, and persons with weakened immune systems)
should be advised against purchasing a pet rodent.9
Efforts are under way to ensure that animal facilities and equipment
in retail outlets are disinfected, that new supplies of rodents come from
sources free from LCMV, and that cross-contamination between new supplies
of rodents and potentially infected animals will not occur. Surfaces, cages,
and any reusable equipment that has been in contact with affected animals,
their waste, or bedding material should be cleaned and disinfected by using
a household disinfectant according to the manufacturer’s instructions.
Persons who are pregnant or have compromised immune systems should not engage
in cleaning and disinfection related to these affected animals or other rodents.
CDC and other partners will work with breeders and retailers in the pet industry
to implement quality-assurance programs to minimize the risk for LCMV infection
in rodents that are sold to the public.
Testing of individual pet rodents in households is not a recommended
strategy to minimize risk for LCMV infection; the probability of any one rodent
in the United States being infected is low. The greatest infection risk for
a pet owner is likely to occur soon after purchase of a pet rodent. Thus,
most exposures likely already have occurred for existing owners and substantial
added risk is unlikely to result from continued ownership of the rodent. However,
women who are or who plan to become pregnant and persons who are immunocompromised
should avoid contact with all rodents.
To prevent any possible infection of other rodents in stores, owners
should not return pet rodents from MidSouth Distributors to pet stores. For
legal, ethical, and wildlife conservation considerations, owners should not
release pet rodents into the wild. Persons who no longer wish to keep their
pet rodent should consult a veterinarian.
CDC continues to work with state public health officials and retailers
in the pet industry to educate the public regarding safe handling of pet rodents
and has prepared educational material for reducing the risk for LCMV infection
from pet rodents. Rodents and other pets from any pet store pose some risk
for transmitting certain infectious diseases and should be handled appropriately.
Additional information about reducing the risk for infectious diseases from
pets is available at http://www.cdc.gov/healthypets. More detailed
information about LCMV is available at http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/lcmv.htm.
Div of Viral and Rickettsial Diseases, National Center for Infectious
Update: Interim Guidance for Minimizing Risk for Human Lymphocytic
Choriomeningitis Virus Infection Associated With Pet Rodents. JAMA. 2005;294(13):1613–1614. doi:10.1001/jama.294.13.1613