Health
Hazards Posed by Rodents
What
many people do not realize, however, is that these pests can be much more than
a nuisance. Rodents, such as rats, mice, prairie dogs and rabbits, are
associated with a number of health risks. In fact, rats and mice are known to
spread more than 35 diseases. These diseases can be spread to humans directly,
through handling of live or dead rodents, through contact with rodent feces,
urine, or saliva, and through rodent bites. Diseases carried by rodents can
also be spread to humans indirectly, through fleas, ticks, or mites that have
fed on an infected rodent.
Rodent droppings can
trigger allergies and transmit food borne illness such as salmonella, and as
mice are capable of dropping up to 25,000 fecal pellets each year, an estimated
70 times each day - prevention and prompt removal in case of an infestation is
key.
Below is a summary of
some of the most common diseases associated with rodents: Hantavirus,
lymphocytic choriomeningitis, tularemia, and plague.
HANTAVIRUS
The Hantavirus was
first recognized in 1993 in the Four Corners region of the southwestern United
States, but is now found primarily in the western United States. This virus is
carried by the deer and white-footed mouse and the cotton and rice rat.
People become infected
with Hantavirus through several routes, but rodent infestation in and around
the home remains the primary risk. The virus is mainly transmitted to people
when fresh rodent urine, droppings, or nesting materials are stirred up, become
airborne and are breathed in by people. In addition, if an infected rodent
bites someone, the virus may be spread to that person. Researchers also suspect
people can become sick if they eat food contaminated by urine, droppings, or
saliva from an infected rodent.
Typically, symptoms of
Hantavirus develop between one and five weeks after exposure to fresh urine,
droppings, or saliva of infected rodents. Infection with Hantavirus can
progress to Hantavirus Pulmonary Syndrome (HPS), a severe respiratory disease which can be
fatal. Early symptoms include fatigue, fever and muscle aches in the thighs,
hips, back, and sometimes shoulders. The infected person may also experience
headaches, dizziness, chills, and abdominal complaints, such as nausea,
vomiting, diarrhea, and abdominal pain. Four to ten days after the initial
phase of illness, the late symptoms of Hantavirus infection develop and HPS may
appear. These include coughing and shortness of breath and progression to
respiratory distress and failure. HPS has a mortality rate of 38 percent.
There is no specific
treatment, cure, or vaccine for Hantavirus infection. However, if an infection
is recognized early and the patient receives acute medical care in an intensive
care unit, they may do better. In these care settings, patients may receive
mechanical ventilation for respiratory failure and be given oxygen therapy to
help them through the period of severe respiratory distress.
LYMPHOCYTIC
CHORIOMENINGITIS (LCM)
Lymphocytic choriomeningitis, or LCM, is a rodent-borne viral infectious disease caused by
lymphocytic choriomeningitis virus (LCMV). The primary host of LCMV is the
common house mouse. Other rodents, such as hamsters, are not the natural
carriers, but can become infected with LCMV from wild mice. Some human
infections have resulted from contact with pet rodents.
Transmission of LCMV
infections can occur after exposure to fresh urine, droppings, saliva, or
nesting materials from infected rodents. Infections are more common in the
colder months when mice enter homes seeking warmer winter
habitats. Transmission may 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, and rarely, through organ transplantation.
An LCMV infection has
two phases; the first phase has non-specific signs and symptoms such as fever,
malaise, lack of appetite, muscle aches, headache, nausea, and vomiting. Less
frequent symptoms include sore throat, cough, joint pain, chest pain,
testicular pain, and salivary gland pain. The second phase of illness is
dominated by neurologic disease. Symptoms may include meningitis (fever,
headache, stiff neck, etc.), encephalitis (drowsiness, confusion, sensory
disturbances, and/or motor abnormalities, such as paralysis), or
meningoencephalitis (inflammation of both the brain and meninges).
Most patients who
develop neurological disease due to LCMV survive. However, as in all infections
of the central nervous system, particularly encephalitis, temporary or
permanent neurological damage is possible.
Women who become
infected with LCM during pregnancy may pass the infection on to the fetus.
Infections occurring during the first trimester may result in fetal death and
pregnancy termination. Infections in the second and third trimesters may result
in serious and permanent birth defects, including vision problems, mental
retardation, and hydrocephaly (water on the brain).
However,
excluding fetal infection, LCM is usually not fatal with a reported mortality
of less than 1 percent. Most cases are self-limited, but often meningitis,
encephalitis, or meningoencephalitis require hospitalization and supportive
treatment based on severity.
PLAGUE
Plague
is infamous for killing millions of people in Europe during the Middle Ages. It
is a disease that affects humans and other mammals and is caused by the
bacterium, Yersinia pestis. Humans usually get plague after being bitten
by an infected rodent flea or by handling an animal infected with plague.
Plague bacteria are
most often transmitted by the bite of an infected flea. If an infected rodent
dies, hungry fleas will seek other sources of blood - including humans,
although dogs and cats may also bring plague-infected fleas into the home. Flea
bite exposure typically results in bubonic plague.
Bubonic plague is
characterized by the sudden onset of fever, headache, chills, and weakness and
one or more swollen, tender and painful lymph nodes (called buboes). The buboes
generally occur in the lymph nodes closest to where the bacteria entered the
human body contain large quantities of multiplying bacteria.
Transmission of plague
may also result from contact with contaminated fluid or tissue. For example, a
hunter skinning a rabbit or other infected animal without using proper
precautions could become infected. This form of exposure most commonly results
in bubonic plague or septicemic plague.
Septicemic plague is
characterized by life threatening septic shock with fever, chills, extreme
weakness, abdominal pain, shock, and possibly bleeding into the skin and other
organs. Septicemic plague can occur as the first symptom of plague, or may
develop from untreated bubonic plague.
Pneumonic plague
typically develops after a person breathes in bacteria-containing droplets.
Patients develop fever, headache, weakness, and a rapidly developing pneumonia
with shortness of breath, chest pain, and cough. The pneumonia may cause
respiratory failure and shock. Pneumonic plague is the most serious form of the
disease and is the only form of plague that can be spread from person to
person
Plague is a very
serious illness, but is treatable with commonly available antibiotics.
However, without prompt treatment, the disease can cause serious illness
or death. The earlier a patient seeks medical care and receives
treatment that is appropriate for plague, the better his or her chances are for
a full recovery. Close contacts of patients with pneumonic plague may need to
be evaluated and possibly treated as well.
TULAREMIA
Tularemia is a disease
of animals and humans caused by the bacterium Francisella tularensis. Rabbits,
hares, and other rodents are especially susceptible and often die in large
numbers during outbreaks. Humans can become infected through several routes,
including tick and deer fly bites; skin contact with infected animals;
ingestion of contaminated water; and through laboratory exposure or inhalation
of contaminated dusts or aerosols.
The signs and symptoms
of tularemia vary depending on how the bacteria enters the body. All forms are
accompanied by fever, which can be as high as 104 °F. Although tularemia can be
life-threatening, most infections can be treated successfully with antibiotics.
The most common form
of tularemia is ulceroglandular disease and usually occurs following a tick or
deer fly bite or after handling an infected animal. A skin ulcer appears at the
site where the organism entered the body and is accompanied by swelling of
regional lymph glands, usually in the armpit or groin.
Glandular tularemia is
similar to ulceroglandular tularemia but without an ulcer. It is also generally
acquired through the bite of an infected tick or deer fly or from handling sick
or dead animals.
Oculoglandular disease
occurs when the bacteria enter through the eye. This can occur when a person is
butchering an infected animal and touches or accidentally has some of the
airborne particles enter their eyes. Symptoms include irritation and
inflammation of eye and swelling of lymph glands in front of the ear.
Oropharyngeal
infection results from eating or drinking contaminated food or water. Patients
with orophyangeal tularemia may have sore throat, mouth ulcers, tonsillitis,
and swelling of lymph glands in the neck.
The most serious form
of tularemia is oneumonic infection. Symptoms include cough, chest pain, and
difficulty breathing. This form results from breathing dusts or aerosols
containing the organism. It can also occur when other forms of tularemia (e.g.
ulceroglandular) are left untreated and the bacteria spread through the
bloodstream to the lungs.
