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is lymphocytic choriomeningitis?
or LCM, is a rodent-borne viral infectious disease that presents as aseptic
meningitis (inflammation of the membrane, or meninges, that surrounds
the brain and spinal cord), encephalitis (inflammation of the brain),
or meningoencephalitis (inflammation of both the brain and meninges).
Its causative agent is the lymphocytic choriomeningitis virus (LCMV),
a member of the family Arenaviridae that was initially isolated in 1933.
Although LCMV is most commonly recognized as causing neurological disease,
as its name implies, infection without symptoms or mild febrile illnesses
are common clinical manifestations. Additionally, pregnancy-related infection
has been associated with congenital hydrocephalus, chorioretinitis, and
does the virus come from?
The primary host
is the common house mouse, Mus musculus. Infection in house
mouse populations may vary by geographic location; about 5% of mice
throughout the United States carry LCMV. The virus is found in the saliva,
urine, and feces of infected mice. Infected mice carry LCMV and shed it
for the duration of their lives without showing any sign of illness. Other
types of rodents, such as hamsters, are not the natural reservoirs but
can become infected with LCMV from wild mice at the breeder, in the pet
store or home environment. Humans are more likely to contract LCMV from
house mice, but infections from pet rodents have also been reported.
do humans become infected?
infected with LCMV after exposure to fresh urine, droppings, saliva, or
nesting materials. Transmission can also occur when these materials are
directly introduced into broken skin, the nose, the eyes, or the mouth,
or presumably, via the bite of an infected rodent. Person-to-person transmission
has not been reported, with the exception of vertical transmission from
infected mother to fetus. Recent investigations indicate that organ transplantation
may also be a means of transmission.
does the disease occur?
LCM and milder LCMV
infections have been reported in Europe, the Americas, Australia, and
Japan, and may occur wherever infected rodent hosts of the virus are found.
However, the disease has historically been underreported, often making
it difficult to determine incidence rates or estimates of prevalence by
geographic region. Several serologic studies conducted in urban areas
have shown that the prevalence of LCMV infection among humans ranges from
2% to 5%.
are the symptoms of LCM?
Some people infected
with LCMV do not become ill. For infected persons who do become ill, onset
of symptoms usually occurs 8-13 days after being exposed to the virus.
A characteristic biphasic febrile illness then follows. The initial phase,
which may last as long as a week, typically begins with any or all of
the following symptoms: fever, malaise, lack of appetite, muscle aches,
headache, nausea, and vomiting. Other symptoms that appear less frequently
include sore throat, cough, joint pain, chest pain, testicular pain, and
parotid (salivary gland) pain. Following a few days of recovery, the second
phase of the disease occurs, consisting of symptoms of meningitis (for
example, fever, headache, and a stiff neck) or characteristics of encephalitis
(for example, drowsiness, confusion, sensory disturbances, and/or motor
abnormalities, such as paralysis). LCMV has also been known to cause acute
hydrocephalus (increased fluid on the brain), which often requires surgical
shunting to relieve increased intracranial pressure. In rare instances,
infection results in myelitis (inflammation of the spinal cord) and presents
with symptoms such as muscle weakness, paralysis, or changes in body sensation.
An association between LCMV infection and myocarditis (inflammation of
the heart muscles) has been suggested.
During the first
phase of the disease, the most common laboratory abnormalities are a low
white blood cell count (leukopenia) and a low platelet count (thrombocytopenia).
Liver enzymes in the serum may also be mildly elevated. After the onset
of neurological disease during the second phase, an increase in protein
levels, an increase in the number of white blood cells or a decrease in
the glucose levels in the cerebrospinal fluid (CSF) is usually found.
there any complications after recovery?
have shown that most patients who develop aseptic meningitis or encephalitis
due to LCMV recover completely. No chronic infection has been described
in humans, and after the acute phase of illness, the virus is cleared.
However, as in all infections of the central nervous system, particularly
encephalitis, temporary or permanent neurological damage is possible.
Nerve deafness and arthritis have been reported. Infection of the human
fetus during the early states of pregnancy may lead to developmental deficits
that are permanent.
the disease ever fatal?
LCM is usually not
fatal. In general, mortality is less than 1%.
is LCM treated?
encephalitis, or meningoencephalitis requires hospitalization and supportive
treatment based on severity. Anti-inflammatory drugs, such as corticosteroids,
may be considered under specific circumstances. Although studies have
shown that ribavirin, a drug used to treat several other viral diseases,
is effective against LCMV in vitro, there is no established evidence to
support its routine use for treatment of LCM in humans.
is at risk for LCMV infection?
Individuals of all
ages who come into contact with urine, feces, saliva, or blood of the
house mouse are potentially at risk for infection. Laboratory workers
who work with the virus or handle infected animals are also at risk. However,
this risk can be minimized by utilizing animals from sources that regularly
test for the virus, wearing proper protective laboratory gear, and following
appropriate safety precautions. Owners of pet mice or hamsters may be
at risk for infection if these animals originate from colonies that have
become contaminated with LCMV, or if the animals become infected from
other wild mice. Human fetuses are at risk of acquiring infection vertically
from an infected mother.
can I do to prevent getting LCMV?
LCMV infection can
be prevented by avoiding contact with house mice and taking precautions
when handling pet rodents (i.e. mice, hamsters, or guinea pigs).
Although rare, pet
rodents may become infected with LCMV from wild rodents. Breeders, pet
stores, and pet owners should take measures to prevent infestations of
wild rodents. Pet rodents should not come into contact with wild rodents.
If you have a rodent
infestation in and around your home, take the following precautions to
reduce the risk of LCMV infection:
- Seal up rodent
entry holes or gaps with steel wool, lath metal, or caulk.
- Trap rats and
mice by using an appropriate snap trap.
- Clean up rodent
food sources and nesting sites and take precautions when cleaning rodent-infected
areas. See recommendations for cleaning rodent-infested areas.
If you have a pet
rodent, wash your hands with soap and water (or waterless alcohol-based
hand rubs when soap is not available and hands are not visibly soiled)
after handling rodents or their cages and bedding.
are the recommendations for cleaning a rodent-infested area?
- Use cross-ventilation
when entering a previously unventilated enclosed room or dwelling prior
- Put on rubber,
latex, vinyl or nitrile gloves.
- Do not stir up
dust by vacuuming, sweeping, or any other means.
- Thoroughly wet
contaminated areas with a bleach solution or household disinfectant.
(bleach) solution: Mix 1 and ½ cups of household bleach in 1
gallon of water.
- Once everything
is wet, take up contaminated materials with damp towel and then mop
or sponge the area with bleach solution or household disinfectant.
- Spray dead rodents
with disinfectant and then double-bag along with all cleaning materials
and throw bag out in an appropriate waste disposal system.
- Remove the gloves
and thoroughly wash your hands with soap and water (or waterless alcohol-based
hand rubs when soap is not available and hands are not visibly soiled).
needs to be done to address the threat of LCMV?
The geographic distributions
of the rodent hosts are widespread both domestically and abroad. However,
infrequent recognition and diagnosis, and therefore underreporting, of
LCM, have limited scientists’ ability to estimate incidence rates
and prevalence of disease among humans. Understanding the epidemiology
of LCM and LCMV infections will help to further delineate risk factors
for infection and develop effective preventive strategies. Increasing
physician awareness will improve disease recognition and reporting, which
may lead to better characterization of the natural history and the underlying
immunopathological mechanisms of disease, and stimulate future therapeutic
research and development.
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