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Health Advisory for Health Care Providers
Tularemia in Western Washington, August 2005
(posted 8/19/05)
From May 28, 2005- August 17, 2005, seven cases of
tularemia have been reported in residents of western Washington
State. Three of the cases have been laboratory confirmed by culture or
serology, while the remaining four are still undergoing confirmatory
testing.
In most years 2-4 tularemia cases are reported
annually (range 1-8); between January 1, 1990 and August 15, 2005, 52
human cases of tularemia have been reported in Washington (see graph).
The recent tularemia cases reside in Cowlitz
County (2), Clark County (2), and Thurston County (2). Onset dates for
the patients are between 5/28/05 to 8/2/05. The age range is 6 to 66
years old; 5 are male. Investigation suggests that most of the exposures
occurred in the county of residence, though in two cases there is a
possibility of exposure both locally and out of state, and one case is
not yet investigated.
Three of the cases presented with
ulceroglandular or glandular tularemia, one with meningitis and
pneumonia, and two with pneumonic tularemia. Both of the pneumonic
tularemia cases were most likely exposed after inhaling aerosolized
bacteria while doing landscaping (mowing, weed whacking). Other recent
exposures involved insect bites (deer flies and ticks); investigation is
ongoing for two cases.
Tularemia is caused by the bacteria Francisella
tularensis and exposure to just a few bacteria can cause febrile disease
in a large variety of animals and in people. The disease cycles in
nature causing periodic die-offs of rabbits, squirrels and other small
mammals. Sick and dead rabbits and squirrels are easily caught and eaten
by outdoor pets. A recent serosurvey of outdoor pet dogs and cats in 18
counties throughout Washington showed that 7/370 (1.9%) had been exposed
to tularemia. Of those tested in Clark, Cowlitz and Lewis counties, 3/69
(4.3%) had serological evidence of exposure.
Clinical information: Identifying the
primary clinical manifestation in tularemia infection helps to indicate
the route of exposure. The incubation period is usually 3-5 days with a
range of 1-14 days. Clinically, tularemia causes fever, chills, muscle
aches, headache and nausea along with one of the following syndromes.
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Ulceroglandular tularemia is the most common
form and presents as an indolent skin ulcer at the site of
inoculation along with regional lymphadenopathy. Less commonly, the
glandular form presents as a painful enlarged lymph nodes that may
become suppurative without a skin lesion. In these cases, exposure
is usually an inoculum at the site of the skin lesion (animal bite,
deer fly or tick bite, cut while skinning an animal, etc.).
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Pneumonic tularemia causes pleuritis or
pneumonia and usually occurs through inhalation of airborne
particles that are stirred up in dust. This form can also be
secondary to bacteremia. Common exposures may occur during
landscaping (mowing, weed eating) or while stirring up dust in barns
with rodent infestation. This is also the form that would manifest
if a population were exposed to the weaponized form of the bacteria
in a biological release.
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Oropharyngeal tularemia presents as
exhudative pharyngitis, abdominal pain and diarrhea. This form is
often associated with eating improperly cooked rabbit or rodent
meat, or drinking contaminated surface water.
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Oculoglandular tularemia occurs when
tularemia in introduced into conjunctiva. It causes purulent
conjunctivitis with regional lymphadenitis. This form is less
common, though it has occurred in Washington after ocular
contamination with stream water.
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Sepsis or Typhoidal tularemia causes a
fulminating acute systemic illness without a skin lesion or
lymphadenopathy. This may occur in patients with underlying illness.
Laboratory testing: Confirmatory
diagnosis of tularemia must be done in a public health laboratory (PHL).
Rapid tests of wound material, pleural fluid, blood, lymph node
aspirates, exudates, throat swabs include direct fluorescent antibody (DFA),
Time Resolved Fluorescence (TRF), and Polymerase chain reaction (PCR).
Cultures should also be done and confirmed at PHL.
If cultures are not available, serologic
diagnosis using microagglutination testing at CDC is done by identifying
a four fold rise in titer between specimens taken 3-4 weeks apart.
Management: Streptomycin or gentamicin
are the first drugs of choice. Doxycycline and chloramphenicol are used
in less severe illness but since they are bacteriostatic, dosage
schedules longer than 10 days may be needed to prevent relapse.
Penicillins and cephalosporins are not effective and should not be used
to treat tularemia. Post exposure prophylactic antimicrobial treatment
of asymptomatic close contacts is not warranted, however may be
considered for exposed laboratory personnel in some circumstances.
Reporting: Health care providers,
hospitals, laboratories and veterinarians should report suspected or
confirmed tularemia infection to your
Local Health Jurisdiction. |
